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EPA Science Inventory
EPA, in conjunction with ONSI Corp., embarked on a project to define, design, test, and assess a fuel cell energy recovery system for application at anaerobic digester waste water (sewage) treatment plants. Anaerobic digester gas (ADG) is produced at these plants during the proce...
Test results for fuel cell operation on anaerobic digester gas
NASA Astrophysics Data System (ADS)
EPA, in conjunction with ONSI, embarked on a project to define, design, test, and assess a fuel cell energy recovery system for application at anaerobic digester waste water (sewage) treatment plants. Anaerobic digester gas (ADG) is produced at these plants during the process of treating sewage anaerobically to reduce solids. ADG is primarily comprised of methane (57-66%), carbon dioxide (33-39%), nitrogen (1-10%), and a small amount of oxygen (<0.5%). Additionally, ADG contains trace amounts of fuel cell catalyst contaminants consisting of sulfur-bearing compounds (principally hydrogen sulfide) and halogen compounds (chlorides). The project has addressed two major issues: development of a cleanup system to remove fuel cell contaminants from the gas and testing/assessing of a modified ONSI PC25 C fuel cell power plant operating on the cleaned, but dilute, ADG. Results to date demonstrate that the ADG fuel cell power plant can, depending on the energy content of the gas, produce electrical output levels close to full power (200 kW) with measured air emissions comparable to those obtained by a natural gas fuel cell. The cleanup system results show that the hydrogen sulfide levels are reduced to below 10 ppbv and halides to approximately 30 ppbv.
Spiegel, R. J.; Preston, J. L.
Fuel cell cogeneration using anaerobic digester gas
Microsoft Academic Search
Gilbert\\/Commonwealth, in association with Public Service Electric and Gas Company (PSE and G), the Bergen County (New Jersey) Utilities Authority (BCUA) and United Technologies Corporation (UTC), conducted a site specific conceptual design study for the U.S. Department of Energy (DOE) to investigate the technical and economic feasibility of a cogeneration fuel cell power plant (FCPP) operating in a large water
J. H. Hirschenhofer; T. M. Piascik; J. Zemkoski
Fuel cell operation on anaerobic digester gas: conceptual design and assessment
The conceptual design of a fuel cell (FC) system for operation on anaerobic digester gas (ADG) is described and its economic and environmental feasibility is projected. ADG is produced at wastewater treatment plants during the process of treating sewage anaerobically to reduce solids. The economic feasibility study shows the fuel cell is economical where plant electricity costs are 5 �\\/kW
R. J. Spiegel; S. A. Thorneloe; J. C. Trocciola; J. L. Preston
Evaluation of systems for purification of fuel gas from anaerobic digestion. Engineering report
Fuel gas obtained from the anaerobic digestion of waste materials usually needs to be treated before being transmitted in existing pipeline systems. The purification scheme involves the removal of carbon dioxide, hydrogen sulfide, and moisture from the digester gas to meet pipeline specifications. Gas treatment systems for the handling of 0.1, 1.0, and 3.0 MM Scfd of raw feed gas
E. Ashare; D. C. Augenstein; J. C. Yeung; R. J. Hossan; G. L. Duret
Enhancement of methane gas production using an industrial waste in anaerobic digestion
SciTech Connect
One method of recycling that may aid in the solution of the current energy problems is anaerobic digestion. Chromium shavings are a solid waste produced by the leather tanning industry. Chromium can block enzymatic systems or interfere with essential cellular metabolites of most oxidizing bacteria. In general, heavy metals coagulate and precipitate proteins, many of which are denatured by this action. This study examines the effects on anaerobic digestion of chromium shavings from leather tanning. Leather chrome shavings contain proteins, nitrogen, and fats. These shavings were added to two of three digesters at various rates. The methane gas production of the experimental units improved significantly compared to the control. In addition, the presence of a toxic loading or change of feed had no harmful effect on the digester performance.
Fradkin, L.; Kremer, F.
Characterization of gas produced by the anaerobic digestion of municipal solid waste
A large-scale proof-of-concept facility has been constructed in Pompano, Florida, to evaluate the feasibility of producing methane-rich gas from the anaerobic digestion of municipal solid waste. The University of Miami together with the AMES Research Laboratory are participating in the environmental source assessment of that technology. The ultimate goal is to determine if the products are environmentally acceptable or are
H. P. Gerrish; E. L. Daly; J. F. Lascarro; N. Nemerow; S. Sengupta; K. F. Wong
Fuel cell operation on anaerobic digester gas: Conceptual design and assessment
The conceptual design of a fuel cell (FC) system for operation on anaerobic digester gas (ADG) is described and its economic and environmental feasibility is projected. ADG is produced at wastewater treatment plants during the process of treating sewage anaerobically to reduce solids. The economic feasibility study shows the fuel cell is economical where plant electricity costs are 5 [cents]/kW h or higher, based on entry level fuel cell costs of $3,000/kW. FCs are one of the cleanest energy technologies available, and the widespread use of this concept should result in a significant reduction in global warming gas and acid rain air emissions. Additionally, technology evaluation focused on improving a commercial phosphoric acid FC power plant operation on ADG is described.
Spiegel, R.J.; Thorneloe, S.A. [Environmental Protection Agency, Research Triangle Park, NC (United States). National Risk Management Research Lab.] [Environmental Protection Agency, Research Triangle Park, NC (United States). National Risk Management Research Lab.; Trocciola, J.C.; Preston, J.L. [ONSI Corp., South Windsor, CT (United States)] [ONSI Corp., South Windsor, CT (United States)
Greenhouse gas emission reductions from domestic anaerobic digesters linked with sustainable sanitation in rural China.
Anaerobic digesters provide clean, renewable energy (biogas) by converting organic waste to methane, and are a key part of China's comprehensive rural energy plan. Here, experimental and modeling results are used to quantify the net greenhouse gas (GHG) reduction from substituting a household anaerobic digester for traditional energy sources in Sichuan, China. Tunable diode laser absorption spectroscopy and radial plume mapping were used to estimate the mass flux of fugitive methane emissions from active digesters. Using household energy budgets, the net improvement in GHG emissions associated with biogas installation was estimated using global warming commitment (GWC) as a consolidated measure of the warming effects of GHG emissions from cooking. In all scenarios biogas households had lower GWC than nonbiogas households, by as much as 54%. Even biogas households with methane leakage exhibited lower GWC than nonbiogas households, by as much as 48%. Based only on the averted GHG emissions over 10 years, the monetary value of a biogas installation was conservatively estimated at US$28.30 ($16.07 ton(-1) CO(2)-eq), which is available to partly offset construction costs. The interaction of biogas installation programs with policies supporting improved stoves, renewable harvesting of biomass, and energy interventions with substantial health cobenefits are discussed. PMID:21348471
Dhingra, Radhika; Christensen, Erick R; Liu, Yang; Zhong, Bo; Wu, Chang-Fu; Yost, Michael G; Remais, Justin V
Greenhouse gas emission reductions from domestic anaerobic digesters linked with sustainable sanitation in rural China
PubMed Central
Anaerobic digesters provide clean, renewable energy (biogas) by converting organic waste to methane, and are a key part of China's comprehensive rural energy plan. Here, experimental and modeling results are used to quantify the net greenhouse gas (GHG) reduction from substituting a household anaerobic digester for traditional energy sources in Sichuan, China. Tunable diode laser absorption spectroscopy and radial plume mapping were used to estimate the mass flux of fugitive methane emissions from active digesters. Using household energy budgets, the net improvement in GHG emissions associated with biogas installation was estimated using global warming commitment (GWC) as a consolidated measure of the warming effects of GHG emissions from cooking. In all scenarios biogas households had lower GWC than non-biogas households, by as much as 54%. Even biogas households with methane leakage exhibited lower GWC than non-biogas households, by as much as 48%. Based only on the averted GHG emissions over 10 years, the monetary value of a biogas installation was conservatively estimated at US$28.30 ($16.07 ton?1 CO2-eq.), which is available to partly offset construction costs. The interaction of biogas installation programs with policies supporting improved stoves, renewable harvesting of biomass, and energy interventions with substantial health co-benefits, are discussed.
Anaerobic Digestion of Agricultural Solid Residues
Agricultural residues can be converted to methane-rich gas mixture. Anaerobic biomethane production is an effective process for conversion of a broad variety of agricultural residues to methane to substitute natural gas and medium calorific value gases. Methane generating bacteria (methanogens) and other microbes that help digest dying plants in anaerobic conditions. Agricultural solid residues (ASR) represent a potential energy resource
Ayhan Demirbas; Temel Ozturk
Mitigation of greenhouse gas emissions by adopting anaerobic digestion technology on dairy, sow and pig farms in Finland
The impact of anaerobic digestion (AD) technology on mitigating greenhouse gas (GHG) emissions from manure management on typical dairy, sow and pig farms in Finland was compared. Firstly, the total annual GHG emissions from the farms were calculated using IPCC guidelines for a similar slurry type manure management system. Secondly, laboratory-scale experiments were conducted to estimate methane (CH4) potentials and
P. Kaparaju; J. Rintala
The paper summarizes the results of a 2-year field test to assess the performance of a specially modified commercial phosphoric acid 200 kW fuel cell power plant to recover energy from anaerobic digester gas (ADG) which has been cleansed of contaminants (sulfur and halide compoun...
Anaerobic digestion of agricultural and other substrates--implications for greenhouse gas emissions.
The greenhouse gas (GHG) emissions, expressed in carbon dioxide equivalents (CO2-eq), of different Austrian biogas systems were analyzed and evaluated using life-cycle assessment (LCA) as part of a national project. Six commercial biogas plants were investigated and the analysis included the complete process chain: viz., the production and collection of substrates, the fermentation of the substrates in the biogas plant, the upgrading of biogas to biomethane (if applicable) and the use of the biogas or biomethane for heat and electricity or as transportation fuel. Furthermore, the LCA included the GHG emissions of construction, operation and dismantling of the major components involved in the process chain, as well as the use of by-products (e.g. fermentation residues used as fertilizers). All of the biogas systems reduced GHG emissions (in CO2-eq) compared with fossil reference systems. The potential for GHG reduction of the individual biogas systems varied between 60% and 100%. Type of feedstock and its reference use, agricultural practices, coverage of storage tanks for fermentation residues, methane leakage at the combined heat and power plant unit and the proportion of energy used as heat were identified as key factors influencing the GHG emissions of anaerobic digestion processes. PMID:23739470
Pucker, J; Jungmeier, G; Siegl, S; P�tsch, E M
Application of enzymes in anaerobic digestion.
Owing to the very low economic value of brewer's spent grains, its utilisation for biogas production is very promising. The hydrolysis of ligno-cellulose is the rate limiting step in anaerobic digestion. Enzymatic pre-treatment promotes the hydrolysis of ligno-cellulose, breaking it down to lower molecular weight substances which are ready to be utilised by the bacteria. A cheap raw multi-enzyme produced by a solid state fermentation (SSF) process is a good substitute for expensive conventional enzyme. The SSF enzyme application to spent grain has been investigated by carrying out enzymatic solubility tests, hydrolytic experiments and two-step anaerobic fermentation of spent grain. Gas chromatograph analysis was conducted to quantify fatty acids concentrations, while CH(4), CO(2), O(2), H(2) and H(2)S were measured to determine biogas quality by means of a gas analyser. DS, oDS, pH were also measured to analyse the anaerobic digestion. The result shows that enzyme application promotes the hydrolysis of ligno-cellulose, indicated by higher enzymatic solubility and fatty acid concentration in a hydrolytic bioreactor. Moreover, biogas production is also increased. The quality of the gases produced is also enhanced. Since the anaerobic digestion can be operated in a stable performance, it can also be concluded that SSF enzyme is compatible with anaerobic digestion. PMID:18048974
Bochmann, G; Herfellner, T; Susanto, F; Kreuter, F; Pesta, G
Anaerobic digestion of woody biomass
Woody biomass without pretreatment is generally considered to be refractive to anaerobic decomposition. This refractory property is attributed to its low moisture content, crystalline nature of the cellulose, and complex association of the component carbohydrates with lignin. This study investigated the methane fermentation (anaerobic digestion) of various wood species using conventional anaerobic digestion and batch anaerobic biogasification potential assays. Most experiments were conducted at 35/sup 0/C with a particle size in the range of 1 to 2 mm, and with a full complement of inorganic nutrient supplements. Conventional CSTR semicontinuous feed anaerobic digestion resulted in low methane yields and low conversion (less than 5% organic reduction). Significantly higher conversion (as high as 54%) and higher methane yields (as high as 5.4 SCF/lb VS added) were observed for several hardwood species in ABP assays employing low loading and long residence times (60 days). One softwood (loblolly pine) and eucalyptus were refractory under these conditions. Pretreatments, including particle size reduction and NaOH, increased rates but not total conversion. These results demonstrate that woody biomass can be decomposed by the methane fermentation and support the potential for development of this process for commercial wood conversion applications. 24 refs., 4 figs., 3 tabs.
Chynoweth, D.P.; Jerger, D.E.
Full Scale Conversion of Anaerobic Digesters to Heated Aerobic Digesters.
National Technical Information Service (NTIS)
Full plant scale experiments were made to determine the effect of heated aerobic digesters on digestion of waste water treatment plant sludge. Existing heated, floating cover equipped, anaerobic digesters, which had failed under excessive paper mill waste...
[Anaerobic digestion of lignocellulosic biomass with animal digestion mechanisms].
Lignocellulosic material is the most abundant renewable resource in the earth. Herbivores and wood-eating insects are highly effective in the digestion of plant cellulose, while anaerobic digestion process simulating animal alimentary tract still remains inefficient. The digestion mechanisms of herbivores and wood-eating insects and the development of anaerobic digestion processes of lignocellulose were reviewed for better understanding of animal digestion mechanisms and their application in design and operation of the anaerobic digestion reactor. Highly effective digestion of lignocellulosic materials in animal digestive system results from the synergistic effect of various digestive enzymes and a series of physical and biochemical reactions. Microbial fermentation system is strongly supported by powerful pretreatment, such as rumination of ruminants, cellulase catalysis and alkali treatment in digestive tract of wood-eating insects. Oxygen concentration gradient along the digestive tract may stimulate the hydrolytic activity of some microorganisms. In addition, the excellent arrangement of solid retention time, digesta flow and end product discharge enhance the animal digestion of wood cellulose. Although anaerobic digestion processes inoculated with rumen microorganisms based rumen digestion mechanisms were developed to treat lignocellulose, the fermentation was more greatly limited by the environmental conditions in the anaerobic digestion reactors than that in rumen or hindgut. Therefore, the anaerobic digestion processes simulating animal digestion mechanisms can effectively enhance the degradation of wood cellulose and other organic solid wastes. PMID:23668159
Wu, Hao; Zhang, Pan-Yue; Guo, Jian-Bin; Wu, Yong-Jie
Anaerobic digestion of space mission wastes.
The technical feasibility of applying leachbed high-solids anaerobic digestion for reduction and stabilization of the organic fraction of solid wastes generated during space missions was investigated. This process has the advantages of not requiring oxygen or high temperature and pressure while producing methane, carbon dioxide, nutrients, and compost as valuable products. Anaerobic biochemical methane potential assays run on several waste feedstocks expected during space missions resulted in ultimate methane yields ranging from 0.23 to 0.30 L g-1 VS added. Modifications for operation of a leachbed anaerobic digestion process in space environments were incorporated into a new design, which included; (1) flooded operation to force leachate through densified feedstock beds; and (2) separation of biogas from leachate in a gas collection reservoir. This mode of operation resulted in stable performance with 85% conversion of a typical space solid waste blend, and a methane yield of 0.3 Lg per g VS added after a retention time of 15 days. These results were reproduced in a full-scale prototype system. A detailed analysis of this process was conducted to design the system sized for a space mission with a six-person crew. Anaerobic digestion compared favorably with other technologies for solid waste stabilization. PMID:16784202
Chynoweth, D P; Owens, J M; Teixeira, A A; Pullammanappallil, P; Luniya, S S
Hemicellulose conversion by anaerobic digestion
The digestibility of an aquatic biomass (water hyacinth), a land-based biomass (Coastal Bermuda grass), and a biomass-waste blend (a mixture of hyacinth, grass, MSW, and sludge) under various digestion conditions was studied. Anaerobic digestion of hemicellulose consists of the steps of enzymatic hydrolysis of hemicellulose to glucans, mannans, galactans, xylans, and arabans, and then to simple hexose and pentose sugars; production of C/sub 2/ and higher fatty acids from the simple sugars; conversion of higher fatty acids to acetate; and finally, production of methane and CO/sub 2/ from acetate, and CO/sub 2/ and hydrogen. The conversion of hemicellulose was higher under mesophilic conditions than those of cellulose or protein for all biomass test feeds, probably because the hemicellulose structure was more vulnerable to enzymatic attack than that of the lignocellulosic component. Cellulose conversion efficiencies at the mesophilic and thermophilic temperatures were about the same. However, hemicellulose was converted at a much lower efficiency than cellulose during thermophilic digestion - a situation that was the reverse of that observed at the mesophilic temperature. Cellulose was utilized in preference to hemicellulose during mesophilic digestion of nitrogen-supplemented Bermuda grass. It was speculated that Bermuda grass cellulose was converted at a higher efficiency than hemicellulose in the presence of external nitrogen because the metabolism of the breakdown product (glucose) of cellulose requires the least investment of enzymes and energy.
Ghosh, S.; Henry, M.P.; Christopher, R.W.
Anaerobic sludge digestion with a biocatalytic additive
The objective of this research was to evaluate the effects of a lactobacillus additive an anaerobic sludge digestion under normal, variable, and overload operating conditions. The additive was a whey fermentation product of an acid-tolerant strain of Lactobacillus acidophilus fortified with CaCO/sub 3/, (NH/sub 4/)/sub 2/HPO/sub 4/, ferrous lactate, and lactic acid. The lactobacillus additive is multifunctional in nature and provides growth factors, metabolic intermediates, and enzymes needed for substrate degradation and cellular synthesis. The experimental work consisted of several pairs of parallel mesophilic (35/sup 0/C) digestion runs (control and test) conducted in five experimental phases. Baseline runs without the additive showed that the two experimental digesters had the same methane content, gas production rate (GPR), and ethane yield. The effect of the additive was to increase methane yield and GPR by about 5% (which was statistically significant) during digester operation at a loading rate (LR) of 3.2 kg VS/m/sup 3/-day and a hydraulic retention time (HRT) of 14 days. Data collected from the various experimental phases showed that the biochemical additive increased methane yield, gas production rate, and VS reduction, and decreased volatile acids accumulation. In addition, it enhanced digester buffer capacity and improved the fertilizer value and dewatering characteristics of the digested residue.
Ghosh, S.; Henry, M.P.; Fedde, P.A.
Anaerobic Digestion in Suspended Growth Bioreactors
\\u000a This chapter concerns the principles of suspended growth anaerobic digestion. The fundamentals of anaerobic metabolism of\\u000a organic matter are first presented. This is followed by presentation of anaerobic process stoichiometry and energetics as\\u000a well as kinetics as these are prerequisites for the design of anaerobic processes. The importance of the feed characteristics\\u000a that make a particular substrate medium or feedstock
Gerasimos Lyberatos; Pratap C. Pullammanappallil
Technical assessment of fuel cell operation on anaerobic digester gas at the Yonkers, NY, wastewater treatment plant.
This paper summarizes the results of a 2-year field test to assess the performance of a specially modified commercial phosphoric acid 200-kW fuel cell power plant to recover energy from anaerobic digester gas (ADG) which has been cleansed of contaminants (sulfur and halide compounds) using a patented gas pretreatment unit (GPU). Specific project goals include characterization of the fuel cell power plant emissions and verification of the GPU performance for removing sulfur contaminants. To remove halide contaminants from the ADG, a halide guard, consisting of a vessel with a metal oxide supported on alumina, was incorporated into the fuel cell reactant supply. This first-of-a-kind demonstration was conducted at the Yonkers, NY, wastewater treatment plant, a sewage processing facility owned and operated by Westchester County. Results have demonstrated that the ADG fuel cell power plant can produce electrical output levels close to full power (200 kW) with negligible air emissions of CO, NO(x), and SO(2). The GPU removed virtually 100% of H(2)S and 88% of organic sulfur, bringing the overall sulfur removal efficiency of the GPU to over 99%. The halide guard removed up to 96% of the halides exiting the GPU. PMID:14522189
Spiegel, R J; Preston, J L
Biochar from anaerobically digested sugarcane bagasse.
This study was designed to investigate the effect of anaerobic digestion on biochar produced from sugarcane bagasse. Sugarcane bagasse was anaerobically digested to produce methane. The digested residue and fresh bagasse was pyrolyzed separately into biochar at 600 degrees C in nitrogen environment. The digested bagasse biochar (DBC) and undigested bagasse biochar (BC) were characterized to determine their physicochemical properties. Although biochar was produced from the digested residue (18% by weight) and the raw bagasse (23%) at a similar rate, there were many physiochemical differences between them. Compared to BC, DBC had higher pH, surface area, cation exchange capacity (CEC), anion exchange capacity (AEC), hydrophobicity and more negative surface charge, all properties that are generally desirable for soil amelioration, contaminant remediation or wastewater treatment. Thus, these results suggest that the pyrolysis of anaerobic digestion residues to produce biochar may be an economically and environmentally beneficial use of agricultural wastes. PMID:20634061
Inyang, Mandu; Gao, Bin; Pullammanappallil, Pratap; Ding, Wenchuan; Zimmerman, Andrew R
On-farm anaerobic digester and fuel alcohol plant
An anaerobic digestion system was constructed and set up on a southern Illinois farm. The anaerobic digestion system was designed to be coupled with a fuel alcohol plant constructed by the farm family as part of an integrated farm energy system. The digester heating can be done using waste hot water from the alcohol plant and biogas from the digester can be used as fuel for the alcohol production. The anaerobic digestion system is made up of the following components. A hog finishing house, which already had a slotted floor and manure pit beneath it, was fitted with a system to scrape the manure into a feed slurry pit constructed at one end of the hog house. A solids handling pump feeds the manure from the feed slurry pit into the digester, a 13,000 gallon tank car body which has been insulated with styrofoam and buried underground. Another pump transfers effluent (digested manure) from the digester to a 150,000 gallon storage tank. The digested manure is then applied to cropland at appropriate times of the year. The digester temperature is maintained at the required level by automated hot water circulation through an internal heat exchanger. The biogas produced in the digester is pumped into a 32,000 gallon gas storage tank.
Not Available
Anaerobic digestibility of algal bioethanol residue.
The aim of this work was to investigate anaerobic digestibility of algal bioethanol residue from saccharification and fermentation processes. A series of batch anaerobic digestion tests using saccharification and fermentation residue showed that the maximum methane yields of saccharification residue and fermentation residue were 239 L/kg VS (Volatile Solids) and 283 L/kg VS (Volatile Solids), respectively. Energy recovered by anaerobic digestion of the residue was 2.24 times higher than that from the ethanol produced in the main process. 5-HMF (5-hydroxymethylfurfural), a saccharification byproduct, could retard methanogenesis at over 3g/L however, the inhibition was prevented by increasing cell biomass concentration. Anaerobic digestion of residue has the potential to enhance bioenergy recovery and environmental sustainability of algal bioethanol production. PMID:22364770
Park, Jeong-Hoon; Yoon, Jeong-Jun; Park, Hee-Deung; Lim, Dong Jung; Kim, Sang-Hyoun
Production of clean energy by anaerobic digestion of phytomass�New prospects for a global warming amelioration technology
Anaerobic digestion of animal dung generated combustible gas � this fact has been known since over 130 years and has been gainfully utilized in generating clean energy in the form of methane-rich �biogas�. During 1970s it was found that aquatic weeds and other phytomass, if anaerobically digested, also produced similarly combustible �bio� gas. It raised great hopes that anaerobic digestion
Tasneem Abbasi; S. A. Abbasi
Methane Enrichment Digestion Experiments at the Anaerobic Experimental Test Unit at Walt Disney World.
The goal of the project was to determine the technical feasibility of utilizing a novel concept in anaerobic digestion, in-situ methane enrichment digestion or MED for producing utility-grade gas from a pilot-scale anaerobic digester. MED tests conducted ...
V. J. Srivastava A. H. Hill
Waste-to-wheel analysis of anaerobic-digestion-based renewable natural gas pathways with the GREET model.
In 2009, manure management accounted for 2,356 Gg or 107 billion standard cubic ft of methane (CH{sub 4}) emissions in the United States, equivalent to 0.5% of U.S. natural gas (NG) consumption. Owing to the high global warming potential of methane, capturing and utilizing this methane source could reduce greenhouse gas (GHG) emissions. The extent of that reduction depends on several factors - most notably, how much of this manure-based methane can be captured, how much GHG is produced in the course of converting it to vehicular fuel, and how much GHG was produced by the fossil fuel it might displace. A life-cycle analysis was conducted to quantify these factors and, in so doing, assess the impact of converting methane from animal manure into renewable NG (RNG) and utilizing the gas in vehicles. Several manure-based RNG pathways were characterized in the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model, and their fuel-cycle energy use and GHG emissions were compared to petroleum-based pathways as well as to conventional fossil NG pathways. Results show that despite increased total energy use, both fossil fuel use and GHG emissions decline for most RNG pathways as compared with fossil NG and petroleum. However, GHG emissions for RNG pathways are highly dependent on the specifics of the reference case, as well as on the process energy emissions and methane conversion factors assumed for the RNG pathways. The most critical factors are the share of flared controllable CH{sub 4} and the quantity of CH{sub 4} lost during NG extraction in the reference case, the magnitude of N{sub 2}O lost in the anaerobic digestion (AD) process and in AD residue, and the amount of carbon sequestered in AD residue. In many cases, data for these parameters are limited and uncertain. Therefore, more research is needed to gain a better understanding of the range and magnitude of environmental benefits from converting animal manure to RNG via AD.
Han, J.; Mintz, M.; Wang, M. (Energy Systems)
Anaerobic digestion of industrial activated aerobic sludge
The Tennessee Eastman Company manufactures a variety of organic chemicals, plastics and fibers at their Kingsport Tennessee Facility. The wastewater generated during the manufacture of these compounds is currently treated using an activated sludge process. The objective of the project is to evaluate the economic potential of an anaerobic digestion process to convert industrial sludge at the Tennessee Eastman Company into biogas. The evaluation will require collection and analysis of experimental data on the anaerobic digestion of industrial sludge obtained from Kingsport. Although the experiments will be conducted using Tennessee Eastman sludge, these results should be also generally applicable to similar industrial sludge.
Goodloe, J.G.; Roberts, R.S.
Anaerobic sludge digestion with a biocatalytic additive. [Lactobacillus acidophilus
Aimed at improving the process operating characteristics of anaerobic digestion for sludge stabilization and SNG production, this study evaluates the effects of a lactobacillus additive under normal, variable, and overload conditions. This whey fermentation product of an acid-tolerant strain of L. acidophilus fortified with CoCO/sub 3/, (NH/sub 4/)/sub 2/HPO/sub 4/, ferrous lactate, and lactic acid provides growth factors, metabolic intermediates, and enzymes needed for substrate degradation and cellular synthesis. Data indicate that the biochemical additive increases methane yield, gas production rate, and volatile solids reduction; decreases volatile acids accumulation; enhances the digester buffer capacity; and improves the fertilizer value and dewatering characteristics of the digested residue. Digester capacities could be potentially doubled when the feed is so treated. Results of field tests with six full-scale digesters confirm observations made with bench-scale digesters.
Microbial activity measurements for anaerobic sludge digestion
The use of particulate substrate in the anaerobic sludge digestion process makes it difficult to measure the biomass in these reactors. Adenosine triphosphate (ATP) and dehydrogenase activity (DHA) were investigated as indicators of the sludge activity for the anaerobic sludge digestion process. ATP measures the energy pools in the biomass and is therefore a measure of the total sludge activity. DHA measurement relies on the addition of specific substrates to stimulate the metabolic activity of the bacteria. Glucose, starch, propionic acid, butyric acid, acetic acid, and digester feed as added substrates were used to stimulate the metabolic activity for DHA measurements. Laboratory experiments were performed to monitor the microbial activity of anaerobic sludge digesters operated both under steady state and in batch mode. The ATP content responded rapidly to changes in the digester operation, which may be the result of increased non-growth associated biochemical activity, not that of increased numbers of the bacteria. DHA was more sensitive than ATP at both low and high sludge ages and seemed to be correlated with the cell's growth phase. At low sludge ages (less than 10 days) glucose as added substrate showed the highest DHA responses, while the digester food and no added substrated showed the highest response when the sludge age exceeded 20 days. A kinetic model based on the solids balances was developed to determine the microbial mass and activity. Both ATP and DHA on a VSS basis (viability) appeared nearly constant over a wide range of sludge ages for the kinetic model data, indicating that ATP and DHA may be used as a rapid and convenient indicator of microbial mass and activity for anaerobic sludge digestion.
Chung, Y.C.
Anaerobic Digestion in a Flooded Densified Leachbed
NASA Technical Reports Server (NTRS)
A document discusses the adaptation of a patented biomass-digesting process, denoted sequential batch anaerobic composting (SEBAC), to recycling of wastes aboard a spacecraft. In SEBAC, high-solids-content biomass wastes are converted into methane, carbon dioxide, and compost.
Chynoweth, David P.; Teixeira, Arthur A.; Owens, John M.; Haley, Patrick J.
Use of biochars in anaerobic digestion.
This study investigated the behavior of biochars from pyrolysis (pyrochar) and hydrothermal carbonization (hydrochar) in anaerobic digestion regarding their degradability and their effects on biogas production and ammonia inhibition. A batch fermentation experiment (42�C, 63 days) was conducted in 100mL syringes filled with 30 g inoculum, 2g biochar and four levels of total ammonium nitrogen (TAN). For pyrochar, no clear effect on biogas production was observed, whereas hydrochar increased the methane yield by 32%. This correlates with the hydrochar's larger fraction of anaerobically degradable carbon (10.4% of total carbon, pyrochar: 0.6%). Kinetic and microbiota analyses revealed that pyrochar can prevent mild ammonia inhibition (2.1 g TANk g(-1)). Stronger inhibitions (3.1-6.6 g TAN kg(-1)) were not mitigated, neither by pyrochar nor by hydrochar. Future research should pay attention to biochar-microbe interactions and the effects in continuously-fed anaerobic digesters. PMID:24859210
Mumme, Jan; Srocke, Franziska; Heeg, Kathrin; Werner, Maja
Operational characteristics of anaerobic digesters at selected wastewater-treatment facilities in the United States
The effectiveness of powered activated carbon in improving volatile solids destruction and gas production in anaerobic digesters that are operating at less than normally expected levels of efficiency was studied. Digester operating characteristics were surveyed and the number of stressed digesters estimated. It is shown that although median values of the operating parameters conformed with those of a well operated digester, 30 percent of the digesters surveyed were stressed with regard to at least one important parameter. Digester gas production and usage are examined to determine the importance of methane off gas as an energy source. Onsite uses include heating digesters and buildings, incinerating sludge, operating equipment, and generating electricity.
Anaerobic digestion for household organics
Considerable success in using anaerobic technology for processing household organics is being reported by several recently constructed facilities in Europe. Organic residuals collected separately in a Belgian town are processed to produce biogas and a compost-like material in less than one month. The dry anaerobic conversion process (DRANCO) was developed by Organic Waste Systems (OWS) in the 1980s, with the collaboration of Professor Willy Verstraete at the University of Ghent`s Laboratory of Applied Microbial Ecology. The patented process converts solid and semisolid organic residuals into biogas (for energy recovery) and a stable humus like product. The plant has competing odor sources such as the active landfill and the surrounding farmland - in fact, the smell of livestock manure is quite prevalent in this heavily agricultural area. Addition of the nonrecyclable paper fraction to the feedstock improves the carbon/nitrogen ratio, soaks up moisture, and absorbs odor. The entire Brecht facility does not occupy much space and total material retention time at the site is one month, compared to a number of months for aerobic systems. It also has a low staffing requirement, provides energy self-sufficiency, and the final soil enhancement product meets established quality standards.
Sinclair, R.; Kelleher, M.
Operational characteristics of anaerobic digesters at selected municipal wastewater treatment facilities in the United States
Bench-scale and pilot plant studies at PNL have shown that powdered activated carbon is effective in improving volatile solids destruction and gas production in anaerobic digesters that are operating at less than normally expected levels of efficiency. To evaluate the applicability of this technology to digesters in the United States, digester operating characteristics at 60 facilities were surveyed and the
R. R. Spencer; A. L. Wong; J. A. Coates; S. B. Ahlstrom
Anaerobic digestion of slaughterhouse by-products
Anaerobic digestion of animal by-products was investigated in batch and semi-continuously fed, reactor experiments at 55�C and for some experiments also at 37�C. Separate or mixed by-products from pigs were tested. The methane potential measured by batch assays for meat- and bone flour, fat, blood, hair, meat, ribs, raw waste were: 225, 497, 487, 561, 582, 575, 359, 619dm3kg?1 respectively,
Anette Hejnfelt; Irini Angelidaki
Effect of pectin on anaerobic digestion of cattle dung
It is therefore desirable to discover procedures to increase the rate of digestion. It has been reported that addition of powdered activated carbon results in an increase in total gas production with high methane content. Based on a review of the literature, it is evident that carbon is responsible for improved digestion. The surface of the activated carbon provides adsorption sites where substrate can accumulate, thereby providing high localized substrate concentration. These areas of adsorption provide a more favorable growth environment for bacterial-substrate systems. No study, however, seems to have been made so far on the effect of other additives like pectin on anaerobic digestion of cattle dung. Since pectin is also used as one of the adsorbents in many cases, it appears desirable to study the effect of pectin on anaerobic digestion of cattle dung with the ultimate aim of improving the production of gas with increased methane content. Experiments carried out with this object in view are reported in this paper. The impact of pectin on volatile acid, pH, and process stability has also been examined. This paper presents the results of two sets of experiments involving pectin addition to bench-scale digesters. One set of experiments is carried out at a controlled temperature of 38 +/- 1 degree C, while the other is carried out at ambient temperature-ambient temperature varied from 40 to 15 degrees C, that is from August to November. 14 references.
Madamwar, D.B.; Mithal, B.M.
Self-heating of anaerobic digesters using energy crops
With the increasing application of energy crops in agricultural biogas plants and increasing digester volumes, the phenomenon of self-heating in anaerobic digesters appeared in some cases. Until now this development was just known from aerobic systems. To get an idea of the thermodynamics inside an anaerobic digester, a detailed analysis of all heat fluxes in a full scale agricultural biogas
H. Lindorfer; R. Braun; R. Kirchmayr
Flow pattern visualization in a mimic anaerobic digester using CFD.
Three-dimensional steady-state computational fluid dynamics (CFD) simulations were performed in mimic anaerobic digesters to visualize their flow pattern and obtain hydrodynamic parameters. The mixing in the digester was provided by sparging gas at three different flow rates. The gas phase was simulated with air and the liquid phase with water. The CFD results were first evaluated using experimental data obtained by computer automated radioactive particle tracking (CARPT). The simulation results in terms of overall flow pattern, location of circulation cells and stagnant regions, trends of liquid velocity profiles, and volume of dead zones agree reasonably well with the experimental data. CFD simulations were also performed on different digester configurations. The effects of changing draft tube size, clearance, and shape of the tank bottoms were calculated to evaluate the effect of digester design on its flow pattern. Changing the draft tube clearance and height had no influence on the flow pattern or dead regions volume. However, increasing the draft tube diameter or incorporating a conical bottom design helped in reducing the volume of the dead zones as compared to a flat-bottom digester. The simulations showed that the gas flow rate sparged by a single point (0.5 cm diameter) sparger does not have an appreciable effect on the flow pattern of the digesters at the range of gas flow rates used. PMID:15685599
Vesvikar, Mehul S; Al-Dahhan, Muthanna
Processing anaerobic sludge for extended storage as anaerobic digester inoculum.
Thermophilic anaerobic sludge was processed to reduce the volume and moisture content in order to reduce costs for storing and transporting the sludge as microbial inoculum for anaerobic digester startup. The moisture content of the sludge was reduced from 98.7% to 82.0% via centrifugation and further to 71.5% via vacuum evaporation. The processed sludge was stored for 2 and 4months and compared with the fresh sludge for the biogas and methane production using food waste and non-fat dry milk as substrates. It was found that fresh unprocessed sludge had the highest methane yield and the yields of both unprocessed and processed sludges decreased during storage by 1-34%, however processed sludges seemed to regain some activity after 4months of storage as compared to samples stored for only 2months. Maximum methane production rates obtained from modified Gompertz model application also increased between the 2-month and 4-month processed samples. PMID:24907580
Li, Jiajia; Zicari, Steven M; Cui, Zongjun; Zhang, Ruihong
Balancing hygienization and anaerobic digestion of raw sewage sludge.
The anaerobic digestion of raw sewage sludge was evaluated in terms of process efficiency and sludge hygienization. Four different scenarios were analyzed, i.e. mesophilic anaerobic digestion, thermophilic anaerobic digestion and mesophilic anaerobic digestion followed by a 60 �C or by an 80 �C hygienization treatment. Digester performance (organic matter removal, process stability and biogas yield) and the hygienization efficiency (reduction of Escherichia coli, somatic coliphages and F-specific RNA phages) were the main examined factors. Moreover, a preliminary economical feasibility study of each option was carried out throughout an energy balance (heat and electricity). The obtained results showed that both thermophilic anaerobic digestion and mesophilic anaerobic digestion followed by a hygienization step were able to produce an effluent sludge that fulfills the American and the European legislation for land application. However, higher removal efficiencies of indicators were obtained when a hygienization post-treatment was present. Regarding the energy balance, it should be noted that all scenarios have a significant energy surplus. Particularly, positive heat balances will be obtained for the thermophilic anaerobic digestion and for the mesophilic anaerobic digestion followed by 60 �C hygienization post-treatment if an additional fresh-sludge/digested sludge heat exchanger is installed for energy recovery. PMID:23063441
Astals, S; Venegas, C; Peces, M; Jofre, J; Lucena, F; Mata-Alvarez, J
Effects of turbulence modelling on prediction of flow characteristics in a bench-scale anaerobic gas-lift digester.
Flow in a gas-lift digester with a central draft-tube was investigated using computational fluid dynamics (CFD) and different turbulence closure models. The k-? Shear-Stress-Transport (SST), Renormalization-Group (RNG) k-?, Linear Reynolds-Stress-Model (RSM) and Transition-SST models were tested for a gas-lift loop reactor under Newtonian flow conditions validated against published experimental work. The results identify that flow predictions within the reactor (where flow is transitional) are particularly sensitive to the turbulence model implemented; the Transition-SST model was found to be the most robust for capturing mixing behaviour and predicting separation reliably. Therefore, Transition-SST is recommended over k-? models for use in comparable mixing problems. A comparison of results obtained using multiphase Euler-Lagrange and singlephase approaches are presented. The results support the validity of the singlephase modelling assumptions in obtaining reliable predictions of the reactor flow. Solver independence of results was verified by comparing two independent finite-volume solvers (Fluent-13.0sp2 and OpenFOAM-2.0.1). PMID:23624047
Coughtrie, A R; Borman, D J; Sleigh, P A
Demonstration of Fuel Cells to Recover Energy from Anaerobic Digester Gas. Phase 1. A Conceptual Design, Preliminary Cost, and Evaluation Study.
The report discusses Phase I (a conceptual design, preliminary cost, and evaluation study) of a program to demonstrate the recovery of energy from waste methane produced by anaerobic digestion of waste water treatment sludge. The fuel cell is being used f...
J. C. Trocciola H. C. Healy
Expert system for control of anaerobic digesters
Anaerobic digestion is a biochemical process that converts organic matter into methane and carbon dioxide along with the production of bacterial matter. It is primarily used for waste and wastewater treatment but can also be used for energy production. Continuous anaerobic digesters are systems that present challenging control problems including the possibility that an unmeasured disturbance can change the sign of the steady-state process gain. An expert system is developed that recognizes changes in the sign of process gain and implements appropriate control laws. The sole on-line measured variable is the methane production rate, and the manipulated input is the dilution rate. The expert system changes the dilution rate according to one of four possible strategies: a constrained conventional set-point control law, a constant yield control law (CYCL) that is nearly optimal for the most common cause of change in the sign of the process gain, batch operation, or constant dilution rate. The algorithm uses a t test for determining when to switch to the CYCL and returns to the conventional set-point control law with bumpless transfer. The expert system has proved successful in several experimental tests: severe overload; mild, moderate, and severe underload; and addition of phenol in low and high levels. Phenol is an inhibitor that in high concentrations changes the sign of the process gain.
Pullammanappallil, P.C.; Svoronos, S.A.; Chynoweth, D.P. [Univ. of Florida, Gainesville, FL (United States)] [Univ. of Florida, Gainesville, FL (United States); Lyberatos, G. [Univ. of Patras (Greece)] [Univ. of Patras (Greece)
State Of The Science On Cogeneration Of Heat And Power From Anaerobic Digestion Of Municipal Biosolids
This presentation will report on work underway to inventory facilities currently utilizing biogas from anaerobic digestion and speak with practitioners to learn: techniques for preparing residuals for digestion, methods to use for cleaning biogas (e.g., of siloxane), and how gas...
Anaerobic Digestion II. Sludge Treatment and Disposal Course #166. Instructor's Guide [and] Student Workbook.
ERIC Educational Resources Information Center
This lesson is the second of a two-part series on anaerobic digestion. Topics discussed include classification of digester by function, roof design, and temperature range, mixing systems, gas system components, operational control basics, and general safety considerations. The lesson includes an instructor's guide and student workbook. The�
Arasmith, E. E.
Anaerobic digestion Of a Petrochemical Wastewater using the UASB process
Anaerobic digestion of effluent from a petrochemical plant producing terephthalic acid has been tested using two Upflow Anaerobic\\u000a Sludge Blanket (USAB) reactors. The reactors were seeded with two different inocula: one from an anaerobic stabilization pond\\u000a receiving wasted sludge from the aerobic treatment plant of the petrochemical industry (reactor A); the other was an anaerobically\\u000a adapted activated sludge from a
J. P. Guyot; H. Macarie; A. Noyola
Autogenerative high pressure digestion: anaerobic digestion and biogas upgrading in a single step reactor system.
Conventional anaerobic digestion is a widely applied technology to produce biogas from organic wastes and residues. The biogas calorific value depends on the CH, content which generally ranges between 55 and 65%. Biogas upgrading to so-called 'green gas', with natural gas quality, generally proceeds with add-on technologies, applicable only for biogas flows > 100 m3/h. In the concept of autogenerative high pressure digestion (AHPD), methanogenic biomass builds up pressure inside the reactor. Since CO2 has a higher solubility than CH4, it will proportion more to the liquid phase at higher pressures. Therefore, AHPD biogas is characterised by a high CH4 content, reaching equilibrium values between 90 and 95% at a pressure of 3-90 bar. In addition, also H2S and NH3 are theoretically more soluble in the bulk liquid than CO2. Moreover, the water content of the already compressed biogas is calculated to have a dew point <--10 degrees C. Ideally, high-quality biogas can be directly used for electricity and heat generation, or injected in a local natural gas distribution net. In the present study, using sodium acetate as substrate and anaerobic granular sludge as inoculum, batch-fed reactors showed a pressure increase up to 90 bars, the maximum allowable value for our used reactors. However, the specific methanogenic activity (SMA) of the sludge decreased on average by 30% compared to digestion at ambient pressure (1 bar). Other results show no effect of pressure exposure on the SMA assessed under atmospheric conditions. These first results show that the proposed AHPD process is a highly promising technology for anaerobic digestion and biogas upgrading in a single step reactor system. PMID:22097043
Lindeboom, R E F; Fermoso, F G; Weijma, J; Zagt, K; van Lier, J B
Ecological clarification of cheese whey prior to anaerobic digestion in upflow anaerobic filter
Anaerobic digestion of cheese whey wastewaters (CW) was investigated in a system consisting of an ecological pretreatment followed by upflow anaerobic filter (UAF). The pretreatment was conducted to solve the inhibition problems during anaerobic treatment of CW caused by the amounts of fats, proteins and carbohydrates and to avoid the major problems of clogging in the reactor. The optimized ecological
H. Gannoun; E. Khelifi; H. Bouallagui; Y. Touhami; M. Hamdi
Methane enrichment digestion experiments at the anaerobic experimental test unit at Walt Disney World. Final report, March 1989-August 1990
The goal of the project was to determine the technical feasibility of utilizing a novel concept in anaerobic digestion, in-situ methane enrichment digestion or MED for producing utility-grade gas from a pilot-scale anaerobic digester. MED tests conducted during this program consistently achieved digester product gas with a methane (CH4) content of greater than 90% (on a dry-, nitrogen-free basis). The MED concept, because it requires relatively simple equipment and modest energy input, has the potential to simplify gas cleanup requirements and substantially reduce the cost of converting wastes and biomass to pipeline quality gas.
Srivastava, V.J.; Hill, A.H.
Anaerobic digestion of animal waste: Effect of mixing
Six laboratory scale biogas mixed anaerobic digesters were operated to study the effect of biogas recycling rates and draft tube height on their performance. The digesters produced methane at 0.40�0.45L per liter of digester volume per day. A higher methane production rate was observed in unmixed digesters, while increased biogas circulation rate reduced methane production. However, different draft tube heights
Khursheed Karim; K. Thomas Klasson; Rebecca Hoffmann; Sadie R. Drescher; David W. DePaoli; M. H. Al-Dahhan
40 CFR Table Jj-6 to Subpart Jj of... - Collection Efficiencies of Anaerobic Digesters
Code of Federal Regulations, 2013 CFR
...Efficiencies of Anaerobic Digesters Anaerobic digester type Cover type Methane collection efficiency Covered anaerobic lagoon (biogas capture) Bank to bank, impermeable 0.975 Modular, impermeable 0.70 Complete mix, fixed film, or plug...
Improving products of anaerobic sludge digestion by microaeration.
Biogas, digested sludge and sludge liquor are the main products of anaerobic sludge digestion. Each of the products is influenced significantly by specific conditions of the digestion process. Therefore, any upgrade of the digestion technology must be considered with regard to quality changes in all products. Microaeration is one of the methods used for the improvement of biogas quality. Recently, microaeration has been proved to be a relatively simple and highly efficient biological method of sulfide removal in the anaerobic digestion of biosolids, but little attention has been paid to comparing the quality of digested sludge and sludge liquor in the anaerobic and microaerobic digestion and that is why this paper primarily deals with this area of research. The results of the long-term monitoring of digested sludge quality and sludge liquor quality in the anaerobic and microaerobic digesters suggest that products of both technologies are comparable. However, there are several parameters in which the 'microaerobic' products have a significantly better quality such as: sulfide (68% lower) and soluble chemical oxygen demand (COD) (33% lower) concentrations in the sludge liquor and the lower foaming potential of the digested sludge. PMID:24569280
Jenicek, P; Celis, C A; Krayzelova, L; Anferova, N; Pokorna, D
Modeling anaerobic digestion of microalgae using ADM1.
The coupling between a microalgal pond and an anaerobic digester is a promising alternative for sustainable energy production by transforming carbon dioxide into methane using solar energy. In this paper, we demonstrate the ability of the original ADM1 model and a modified version (based on Contois kinetics for the hydrolysis steps) to represent microalgae anaerobic digestion. Simulations were compared to experimental data of an anaerobic digester fed with Chlorella vulgaris. The modified ADM1 fits adequately the data for the considered 140 day experiment encompassing a variety of influent load and flow rates. It turns out to be a reliable predictive tool for optimising the coupling of microalgae with anaerobic digestion processes. PMID:21536430
Mairet, Francis; Bernard, Olivier; Ras, Monique; Lardon, Laurent; Steyer, Jean-Philippe
Stabilization of Sewage Sludge by Two-Phase Anaerobic Digestion.
The research described in the report was concerned with evaluation of alternative approaches to anaerobic digestion, a process commonly used on the residual stream from wastewater treatment. The principal approach studied was that of separating the acid- ...
A. Sajjad M. P. Henry S. Ghosh
The Water Environment Research Foundation (WERF) recently published a report titled ?Examination of Reactivation and Regrowth of Fecal Coliforms in Anaerobically Digested Sludges?. Seven full-scale publicly owned treatment facilities were sampled several times to determine if bac...
Membrane-coupled anaerobic digestion of municipal sewage sludge.
Membrane-coupled anaerobic digestion utilizes a concept of simultaneous sludge digestion and thickening. Membranes may successfully be applied to eliminate the need for thickening polymers and avoid their likely inhibitory effect on anaerobic biomass. A 550 L completely mixed anaerobic digester was operated under mesophilic conditions (35 degrees C). Two ultrafiltration membrane systems were evaluated for their potential in membrane-coupled anaerobic digestion: vibrating and cross flow. A volatile solids reduction of 590% was achieved at an average mixed liquor suspended solids concentration of 1.8%. The substrate utilization rate was 1.3 d(-1). The vibrating membrane operated at a flux of 1.6-2.0 m3/m2-d and the tubular membrane fluxes in the range 3.4-3.6 m3/m2-d. PMID:16180436
Pierkiel, A; Lanting, J
Anaerobic digestion of water hyacinth and sludge
The Institute of Gas Technology (IGT) has been operating an experimental test unit (ETU) at the Walt Disney World (WDW) wastewater treatment plant to demonstrate the conversion of water hyacinth and sludge to methane in a solids concentrating (SOLCON) digester. Results from 2 years to operation have confirmed earlier laboratory observations that this digester achieves higher methane yields and solids conversion than those observed in continuous stirred tank reactors. Methane yields as high as 0.49 m/sup 3/ kg/sup -1/ (7.9 SCF/lb) volatile solids added have been obtained during steady-state operation on a blend of water hyacinth and sludge. 9 refs., 5 figs., 5 tabs.
Biljetina, R.; Srivastava, V.J.; Chynoweth, D.P.; Hayes, T.D.
Characterization and Environmental Studies of Pompano Beach Anaerobic Digestion Facility. Semi-Annual Report.
Anaerobic digestion of municipal waste has been demonstrated to be feasible in bench scale experiments by Pfeffer (1974). Approximately, 50% reduction in mass and production of 6000 ft exp 3 of gas/ton have been estimated. The gas composition is estimated...
S. Sengupta S. Farooq H. P. Gerrish K. F. Wong E. L. Daly
On-Farm Anaerobic Digester and Fuel Alcohol Plant.
An anaerobic digestion system, coupled with a fuel alcohol plant, was constructed and set up on a southern Illinois farm as part of an integrated farm energy system. The digester heating can be done using waste hot water from the alcohol plant and biogas ...
H. H. Bengtson
Sequencing Mesophilic and Thermophilic Anaerobic Digesters. Final Report.
This project employed two laboratory bench scale, complete-mix anaerobic sludge digesters arranged in a series configuration. The first digester was operated at 35 exp 0 C (mesophilic) and the second at 50 exp 0 C (thermophilic). A portion of the thermoph...
Steam pressure disruption of municipal solid waste enhances anaerobic digestion kinetics and biogas yield.
Biomass waste, including municipal solid waste (MSW), contains lignocellulosic-containing fiber components that are not readily available as substrates for anaerobic digestion due to the physical shielding of cellulose imparted by the nondigestible lignin. Consequently, a substantial portion of the potentially available carbon is not converted to methane and the incompletely digested residues from anaerobic digestion generally require additional processing prior to their return to the environment. We investigated and developed steam pressure disruption as a treatment step to render lignocellulosic-rich biomass more digestible and as a means for increasing methane energy recovery. The rapid depressurization after steam heating (240 degrees C, 5 min.) of the nondigested residues following a 30-day primary digestion of MSW caused a visible disruption of fibers and release of soluble organic components. The disrupted material, after reinoculation, provided a rapid burst in methane production at rates double those observed in the initial digestion. This secondary digestion proceeded without a lag phase in gas production, provided approximately 40% additional methane yields, and was accompanied by a approximately 40% increase in volatile solids reduction. The secondary digestate was found to be enriched in lignin and significantly depleted in cellulose and hemi-cellulose components when compared to primary digestate. Thus, steam pressure disruption treatment rendered lignocellulosic substrates readily accessible to anaerobic digestion bacteria and improved both the kinetics of biogas production and the overall methane yield from MSW. Steam pressure disruption is central to a new anaerobic digestion process approach including sequential digestion stages and integrated energy recovery, to improve process yields, provide cogenerated energy for process needs, and to provide effective reuse and recycling of waste biomass materials. PMID:11753918
Liu, H W; Walter, H K; Vogt, G M; Vogt, H S; Holbein, B E
Effect of alkaline pretreatment on anaerobic digestion of solid wastes
The introduction of the anaerobic digestion for the treatment of the organic fraction of municipal solid waste (OFMSW) is currently of special interest. The main difficulty in the treatment of this waste fraction is its biotransformation, due to the complexity of organic material. Therefore, the first step must be its physical, chemical and biological pretreatment for breaking complex molecules into simple monomers, to increase solubilization of organic material and improve the efficiency of the anaerobic treatment in the second step. This paper describes chemical pretreatment based on lime addition (Ca(OH){sub 2}), in order to enhance chemical oxygen demand (COD) solubilization, followed by anaerobic digestion of the OFMSW. Laboratory-scale experiments were carried out in completely mixed reactors, 1 L capacity. Optimal conditions for COD solubilization in the first step of pretreatment were 62.0 mEq Ca(OH){sub 2}/L for 6.0 h. Under these conditions, 11.5% of the COD was solubilized. The anaerobic digestion efficiency of the OFMSW, with and without pretreatment, was evaluated. The highest methane yield under anaerobic digestion of the pretreated waste was 0.15 m{sup 3} CH{sub 4}/kg volatile solids (VS), 172.0% of the control. Under that condition the soluble COD and VS removal were 93.0% and 94.0%, respectively. The results have shown that chemical pretreatment with lime, followed by anaerobic digestion, provides the best results for stabilizing the OFMSW.
Lopez Torres, M. [National Center for Scientific Researcher (CNIC), Environmental Pollution Department (DECA), Ave. 25 y 158, Cubanacan, Playa, Havana City (Cuba)], E-mail: firstname.lastname@example.com; Espinosa Llorens, Ma. del C. [National Center for Scientific Researcher (CNIC), Environmental Pollution Department (DECA), Ave. 25 y 158, Cubanacan, Playa, Havana City (Cuba)
Anaerobic digestion of marine microalgae in different salinity levels.
In the context of biofuel production from marine microalgae, anaerobic digestion has the potential to make the process more sustainable and to increase energy efficiency. However, the use of salt-containing microalgae organic residues entails the presence of salts which inhibits methanogenesis. The search for suitable anaerobic microbial consortium adapted to saline conditions can boost the anaerobic conversion into methane. The anaerobic digestion performance of three different anaerobic microbial consortia was assessed in batch tests at different salinities between 15 and 150gL(-1) and for three successive substrate additions. After an acclimation period, the methane (CH4) yield of the halophilic methanogens at 35gL(-1) of salinity was close to the reference value without salt addition. Above 75gL(-1) of salinity, methanogenesis was considerably slowed down. The results underline that methane production from halophilic sediment can be envisaged and promoted for practical application at a seawater concentration. PMID:24632407
Mottet, Alexis; Habouzit, Fr�d�ric; Steyer, Jean Philippe
Potential of anaerobic digestion for mitigation of greenhouse gas emissions and production of renewable energy from agriculture: barriers and incentives to widespread adoption in Europe.
The paper considers the role of anaerobic digestion in promoting good agricultural practice on farms and the contribution this would make to reducing the environmental impacts associated with manure management. There are no regulatory drivers to promote the use of digestion in Europe, and the technology has only been widely adopted where economic drivers and coherent policies have been implemented at a national level. These measures have included direct subsidy on the energy price paid for "green electricity", and exemption of tax when biogas is used as a vehicle fuel. In those countries where financial incentives are not available or where a financial penalty is incurred through the regulatory regime, the uptake of digestion has been poor. Even with subsidies, digestion of animal manures as a single substrate is not common, and countries with successful schemes have achieved this either by permitting the import of wastes onto the farm or offering bonus subsidies for the use of energy crops. Both of these measures improve the energy efficiency of the process by increasing the volumetric methane production, although concerns are expressed that attention could concentrate on energy production at the expense of improving manure management. PMID:17564382
Banks, C J; Salter, A M; Chesshire, M
Thermochemical liquidization of anaerobically digested and dewatered sludge and anaerobic retreatment
The pretreatment effect of thermochemical liquidization for the anaerobic retreatment of anaerobically digested and dewatered sludge was studied. The digested sludge (dry matter; 15.7%) was thermochemically liquidized at 175�C and 4 MPa with a holding time of 1 h. The liquidized sludge was separated by centrifugation to produce a supernatant of 44.7% (w\\/w) and precipitate of 52.3%. The liquidized sludge
Shigeki Sawayama; Seiichi Inoue; Kenichiro Tsukahara; Tomoko Ogi
Anaerobic Digestion and Combined Heat and Power Study
One of the underlying objectives of this study is to recover the untapped energy in wastewater biomass. Some national statistics worth considering include: (1) 5% of the electrical energy demand in the US is used to treat municipal wastewater; (2) This carbon rich wastewater is an untapped energy resource; (3) Only 10% of wastewater treatment plants (>5mgd) recover energy; (4) Wastewater treatment plants have the potential to produce > 575 MW of energy nationwide; and (5) Wastewater treatment plants have the potential to capture an additional 175 MW of energy from waste Fats, Oils and Grease. The WSSC conducted this study to determine the feasibility of utilizing anaerobic digestion and combined heat and power (AD/CHP) and/or biosolids gasification and drying facilities to produce and utilize renewable digester biogas. Digester gas is considered a renewable energy source and can be used in place of fossil fuels to reduce greenhouse gas emissions. The project focus includes: (1) Converting wastewater Biomass to Electricity; (2) Using innovative technologies to Maximize Energy Recovery; and (3) Enhancing the Environment by reducing nutrient load to waterways (Chesapeake Bay), Sanitary Sewer Overflows (by reducing FOG in sewers) and Greenhouse Gas Emissions. The study consisted of these four tasks: (1) Technology screening and alternative shortlisting, answering the question 'what are the most viable and cost effective technical approaches by which to recover and reuse energy from biosolids while reducing disposal volume?'; (2) Energy recovery and disposal reduction potential verification, answering the question 'how much energy can be recovered from biosolids?'; (3) Economic environmental and community benefit analysis, answering the question 'what are the potential economic, environmental and community benefits/impacts of each approach?'; and (4) Recommend the best plan and develop a concept design.
Frank J. Hartz; Rob Taylor; Grant Davies
Effect of dietary arsonic acids on performance characteristics of swine waste anaerobic digesters
A completely random design experiment was conducted to determine the effect of dietary arsonic acids on the performance of laboratory swine waste anaerobic digesters. Fortified corn-soybean meal diets containing no arsonic acids (control), 100 ppm arsanilic acid or 75 ppm roxarsone were fed to growing-finishing pigs. Fresh waste (including urine) from all treatments were collected daily for 74 days and loaded at a rate of 2.4 kg volatile solids/cubic meter into nine 25-L anaerobic digesters heated to 34 degrees with continuous agitation and total gas collection. After a 60-day acclimation period, daily gas production and composition and nutrient composition data were obtained from the anaerobic digesters. Inclusion of the arsonic acids in swine diets reduced dry matter and volatile solids content. Dietary arsonic acids also increased NH4+-N. Alky. was high in all the digesters; however, arsonic acids decreased alky. Dietary arsonic acids reduced the ratio of CH4 to CO2 in the gas compared to the control. Significant amounts of As accumulated in the digesters. Alcohol, ethanol, and propanol concentrations were increased by roxarsone, and arsanilic acid increased the PrCO2H concentrations over the percentage in both the roxarsone and control digesters.
Brumm, M.C.; Sutton, A.L.; Jones, D.D.
Energetic and biochemical valorization of cork boiling wastewater by anaerobic digestion
Background In addition to energy benefits, anaerobic digestion offers other interesting advantages. The cork industry is of great environmental, economic and social significance in the western Mediterranean region, with Portugal being the world-leading producer and exporter. Cork boiling wastewater (CBW) is a toxic and recalcitrant organic effluent produced by this sector, which constitutes a serious environmental hazard. However, there is no documented research on anaerobic treatment/valorization performed with this effluent. The work presented here was developed with the aim to use the anaerobic digestion process to convert the CBW polluting organic load into an energy carrier gas and valuable molecules for industry. Results No lag phases were observed and a methane yield of 0.126 to 0.142�m3�kg-1 chemical oxygen demand (COD)added was registered in the mesophilic consortium experiments carried out in batch flasks at 37?�?1�C. Anaerobic digestion can be advantageously connected to ultrafiltration or electrochemical processes, due to the following: 1) reduction of ellagic acid content and consequent decrease of CBW viscosity; and 2) increase in conductivity after the anaerobic process, avoiding the electrolyte application of the electrochemical process. The improvement of several CBW biochemical features shows that anaerobic digestion may provide additionally useful molecules. The rise in concentration of some of these compounds, belonging to the benzoic acid family (gallic, protocatechuic, vanillic and syringic acids), is responsible for the increase of antiradical activity of the phenolic fraction. Additionally, some enzymatic activity was also observed and while the laccase activity increased in the digested effluent by anaerobiosis, xylanase was formed in the process. Conclusions The multidisciplinary approach adopted allowed the valorization of CBW in terms of energy and valuable biomolecules. By exploiting the anaerobic digestion process potential, a novel methodology to toxic and recalcitrant cork processing wastewater was developed.
Animal digestive strategies versus anaerobic digestion bioprocesses for biogas production from lignocellulosic biomass
Herbivorous mammals and wood-eating insects are fairly effective in the digestion of plant polymers, such as lignocellulosics.\\u000a In order to improve methane production from the lignocellulosic biomass, several kinds of anaerobic digestion processes derived\\u000a from animal models have been devised. However, the rates of biodegradation occurring in the anaerobic bioreactors still remain\\u000a lower than in animal guts. The effectiveness of
Ali Bayan�; Serge R. Guiot
Effect of metals on anaerobic digestion of water hyacinth-cattle dung
The effect of several salts, FeCl3, NiCl2, CoCl2, CuCl2, and ZnCl2, on anaerobic digestion of water hyacinth-cattle dung was examined. Among the salts studied, FeCl3 caused a more than 60% increase in gas production with a high methane content.
Vikram B. Patel; Anami R. Patel; Manisha C. Patel; Datta B. Madamwar
Potential errors in the quantitative evaluation of biogas production in anaerobic digestion processes
Errors that are commonly made in the quantification of biogas from anaerobic digestion experiments were investigated.For liquid displacement gasometers where a barrier solution separates the biogas and the atmosphere, inaccuracy due to gas diffusion was examined experimentally. Acidified saturated saline solution was the most suitable barrier solution, as biogas characteristics changed least with time. Using acidified or tap water caused
Mark Walker; Yue Zhang; Sonia Heaven; Charles Banks
Three-reaction model for the anaerobic digestion of microalgae.
Coupling an anaerobic digester to a microalgal culture has received increasing attention as an alternative process for combined bioenergy production and depollution. In this article, a dynamic model for anaerobic digestion of microalgae is developed with the aim of improving the management of such a coupled system. This model describes the dynamics of inorganic nitrogen and volatile fatty acids since both can lead to inhibition and therefore process instability. Three reactions are considered: Two hydrolysis-acidogenesis steps in parallel for sugars/lipids and for proteins, followed by a methanogenesis step. The proposed model accurately reproduces experimental data for anaerobic digestion of the freshwater microalgae Chlorella vulgaris with an organic loading rate of 1 gCOD?L(-1)?d(-1). In particular, the three-reaction pathway allows to adequately represent the observed decoupling between biogas production and nitrogen release. The reduced complexity of this model makes it suitable for developing advanced, model-based control and monitoring strategies. PMID:22020983
Mairet, Francis; Bernard, Olivier; Cameron, Elliot; Ras, Monique; Lardon, Laurent; Steyer, Jean-Philippe; Chachuat, Beno�t
Cellulosic waste degradation by rumen-enhanced anaerobic digestion
Anaerobic digestion of lignocellulosic material is carried out effectively in many natural microbial ecosystems including the rumen. A rumen-enhanced anaerobic sequencing batch reactor was used to investigate cellulose degradation to give analysis of overall process stoichiometry and rates of hydrolysis. The reactor achieved VFA production rates of 207-236 mg COD\\/L\\/h at a loading rate of 10 g\\/L\\/d. Overloading of the
S. P. Barnes; J. Keller
Fate and effect of silver on the anaerobic digestion process
Laboratory assays were conducted to assess the anaerobic biodegradability of a silver-bearing, waste activated sludge as well as the effect of silver compounds on the anaerobic digestion process. All assays were performed at 35�C in the dark. The ultimate biodegradability of a silver-bearing waste activated sludge (5.0�g silver\\/kg sludge dry solids) was 61% as compared to 59% for the control
Spyros G Pavlostathis; Sung Kyu Maeng
Alginate degradation during anaerobic digestion of Laminaria hyperborea stipes
Polyphenols and divalent metal ions present in the tissue may seriously affect the degradation of alginate during anaerobic\\u000a digestion of brown seaweeds. Laminaria hyperborea stipes, harvested at 59 N off the Norwegian coast in the autumn, were degraded\\u000a at different concentrations of polyphenols in anaerobic batch reactors at 35 C and pH 7. This was done by removing or adding
Einar Moen; Svein Horn; Kjetill �stgaard
Advantages of anaerobic digestion of sludge in microaerobic conditions.
The paper reviews results and experience of microaerobic experiments at both high and low sulphide concentrations and evaluates advantages and drawbacks of the anaerobic digestion of sludge in microaerobic conditions as regards biogas quality, digested sludge quality, organic pollutants biodegradability and methanogenic activity of biomass. The innovative microaerobic modification of the anaerobic sludge digestion technology was studied in both laboratory and full scale. Microaerobic conditions are obtained by dosing of a limited amount of the air into the liquid phase of the anaerobic digester. It was shown that anaerobic bacteria including methanogens can be active also in such system. In a mixed culture, even strict anaerobes can survive without inhibition, if the facultative microorganisms are able to consume the present oxygen quickly and fully. Until now, the microaerobic conditions were predominantly used for hydrogen sulphide removal from biogas. In the paper the role of the surplus oxygen was studied also at low sulphide concentration, when the oxygen is consumed in high extent for other processes beside sulphide oxidation. PMID:20651449
Jenicek, P; Koubova, J; Bindzar, J; Zabranska, J
Waste heat utilization in an anaerobic digestion system
Anaerobic digestion has great potential as an energy source. Not only does it provide an effective method for waste mitigation, but it has the potential to generate significant quantities of fuel and electricity. In order to ensure efficient digestion and biomass utilization, however, the system must be continuously maintained at elevated temperatures. It is technically feasible to supplement such a system with outside energy, but it is more cost effective to heat the system using only the produced biogas. While there is considerable literature covering the theory of anaerobic digestion, there are very few practical studies to show how heat utilization affects system operation. This study considers the effect of major design variables (i.e. heat exchanger efficiencies and biogas conditioning) on promoting a completely self-sustaining digestion system. The thesis considers a real world system and analyzes how it can be improved to avoid the need of an external energy source.
Boissevain, Brett
Anaerobic digestion and wastewater treatment systems
Upflow Anaerobic Sludge Bed (UASB) wastewater (pre-)treatment systems represent a proven sustainable technology for a wide range of very different industrial effluents, including those containing toxic\\/inhibitory compounds. The process is also feasible for treatment of domestic wastewater with temperatures as low as 14�16� C and likely even lower. Compared to conventional aerobic treatment systems the anaerobic treatment process merely offers
G. Lettinga
Modelling of the mesophilic anaerobic co-digestion of olive mill wastewater with olive mill solid waste using anaerobic digestion model No. 1 (ADM1)
The anaerobic digestion model No. 1 (ADM1), conceived by the international water association (IWA) task group for mathematical modelling of anaerobic digestion processes is a structured generic model which includes multiples steps describing biochemical and physicochemical processes encountered in the anaerobic degradation of complex organic substrates and a common platform for further model enhancement and validation of dynamic simulations for
Fezzani Boubaker; Ben Cheikh Ridha
Anaerobic sludge digestion in the presence of lactobacillus additive
A laboratory evaluation of a lactobacillus fermentation product was performed to study its effects as an additive on the anaerobic digestion of sewage sludge under conventional and overloaded high-rate conditions. The overloaded conditions were those experienced in commercial municipal digesters. It was concluded from this work that the use of the additive at low concentrations permits digester operation at least up to double the loading of untreated digesters and at higher methane yields and volatile solids reductions without affecting effluent quality. The additive also imparts iproved digester stability and rapid response to loading rate and detention time excursions and upsets. The beneficial effets of the additive observed in the laboratory remain to be established with other feeds such as biomass, and in large-scale commercial digestion tests that are now in progress.
Ghosh, S.; Klass, D.L.
Influence of high gas production during thermophilic anaerobic digestion in pilot-scale and lab-scale reactors on survival of the thermotolerant pathogens Clostridium perfringens and Campylobacter jejuni in piggery wastewater.
Safe reuse of animal wastes to capture energy and nutrients, through anaerobic digestion processes, is becoming an increasingly desirable solution to environmental pollution. Pathogen decay is the most important safety consideration and is in general, improved at elevated temperatures and longer hydraulic residence times. During routine sampling to assess pathogen decay in thermophilic digestion, an inversely proportional relationship between levels of Clostridium perfringens and gas production was observed. Further samples were collected from pilot-scale, bench-scale thermophilic reactors and batch scale vials to assess whether gas production (predominantly methane) could be a useful indicator of decay of the thermotolerant pathogens C. perfringens and Campylobacter jejuni. Pathogen levels did appear to be lower where gas production and levels of methanogens were higher. This was evident at each operating temperature (50, 57, 65 degrees C) in the pilot-scale thermophilic digesters, although higher temperatures also reduced the numbers of pathogens detected. When methane production was higher, either when feed rate was increased, or pH was lowered from 8.2 (piggery wastewater) to 6.5, lower numbers of pathogens were detected. Although a number of related factors are known to influence the amount and rate of methane production, it may be a useful indicator of the removal of the pathogens C. perfringens and C. jejuni. PMID:19500814
Skillman, L C; Bajsa, O; Ho, L; Santhanam, B; Kumar, M; Ho, G
Dry anaerobic digestion of the organic fraction of municipal solid waste
Anaerobic digestion is an attractive technology for solid waste management. This thesis describes the technological potentials of dry anaerobic digestion of the organic fraction of Municipal Solid Waste (MSW) using batch systems. In 1985 a research programme was started to develop the so- called BIOCEL system based on batchwise anaerobic digestion yielding biogas and compost. The research programme was financially
E. ten Brummeler
The anaerobic digestion of solid wastes is now a widely- used technology in Europe with more than 50 full- scale plants operating. However, anaerobic solid waste digestion is still used to only a limited extent in North America with only three facilities in Canada. Because of the expected importance of anaerobic digestion in the future for energy recovery, reliable tools
Mariana Chavez-Vazquez; David M. Bagley
Inactivation of selected bacterial pathogens in dairy cattle manure by mesophilic anaerobic digestion (balloon type digester).
Anaerobic digestion of animal manure in biogas digesters has shown promise as a technology in reducing the microbial load to safe and recommended levels. We sought to treat dairy manure obtained from the Fort Hare Dairy Farm by investigating the survival rates of bacterial pathogens, through a total viable plate count method, before, during and after mesophilic anaerobic digestion. Different microbiological media were inoculated with different serial dilutions of manure samples that were withdrawn from the biogas digester at 3, 7 and 14 day intervals to determine the viable cells. Data obtained indicated that the pathogens of public health importance were 90%-99% reduced in the order: Campylobacter sp. (18 days) < Escherichia coli sp. (62 days) < Salmonella sp. (133 days) from a viable count of 10.1 � 103, 3.6 � 105, 7.4 � 103 to concentrations below the detection limit (DL = 102 cfu/g manure), respectively. This disparity in survival rates may be influenced by the inherent characteristics of these bacteria, available nutrients as well as the stages of the anaerobic digestion process. In addition, the highest p-value i.e., 0.957 for E. coli showed the statistical significance of its model and the strongest correlation between its reductions with days of digestion. In conclusion, the results demonstrated that the specific bacterial pathogens in manure can be considerably reduced through anaerobic digestion after 133 days. PMID:25026086
Manyi-Loh, Christy E; Mamphweli, Sampson N; Meyer, Edson L; Okoh, Anthony I; Makaka, Golden; Simon, Michael
Inactivation of Selected Bacterial Pathogens in Dairy Cattle Manure by Mesophilic Anaerobic Digestion (Balloon Type Digester)
Anaerobic digestion of animal manure in biogas digesters has shown promise as a technology in reducing the microbial load to safe and recommended levels. We sought to treat dairy manure obtained from the Fort Hare Dairy Farm by investigating the survival rates of bacterial pathogens, through a total viable plate count method, before, during and after mesophilic anaerobic digestion. Different microbiological media were inoculated with different serial dilutions of manure samples that were withdrawn from the biogas digester at 3, 7 and 14 day intervals to determine the viable cells. Data obtained indicated that the pathogens of public health importance were 90%�99% reduced in the order: Campylobacter sp. (18 days) < Escherichia coli sp. (62 days) < Salmonella sp. (133 days) from a viable count of 10.1 � 103, 3.6 � 105, 7.4 � 103 to concentrations below the detection limit (DL = 102 cfu/g manure), respectively. This disparity in survival rates may be influenced by the inherent characteristics of these bacteria, available nutrients as well as the stages of the anaerobic digestion process. In addition, the highest p-value i.e., 0.957 for E. coli showed the statistical significance of its model and the strongest correlation between its reductions with days of digestion. In conclusion, the results demonstrated that the specific bacterial pathogens in manure can be considerably reduced through anaerobic digestion after 133 days.
Manyi-Loh, Christy E.; Mamphweli, Sampson N.; Meyer, Edson L.; Okoh, Anthony I.; Makaka, Golden; Simon, Michael
Assessing amendment and fertilizing properties of digestates from anaerobic digestion through a comparative study with digested sludge and compost.
Digestate, with biogas represents the final products of anaerobic digestion (AD). The methane-rich biogas is used to produce electricity and heat, whereas the digestate could be valorized in agriculture. Contrarily to well-recognized biomasses such as digested sludge and compost, the properties of the digestate are not well known and its agricultural use remains unexplored. In this work, a first attempt to study the agronomic properties of digestates was performed by comparing the chemical, spectroscopic, and biological characteristics of digestates with those of compost and digested sludge, used as reference organic matrices. A total of 23 organic matrices were studied, which include eight ingestates and relative digestates, three composts, and four digested sludges. The analytical data obtained was analyzed using principal component analysis to better show in detail similarities or differences between the organic matrices studied. The results showed that digestates differed from ingestates and also from compost, although the starting organic mix influenced the digestate final characteristics. With respect to amendment properties, it seems that biological parameters, more than chemical characteristics, were more important in describing these features. In this way, amendment properties could be ranked as follows: compost?digestate>digested sludge?ingestate. As to fertilizer properties, AD allowed getting a final product (digestate) with very good fertilizing properties because of the high nutrient content (N, P, K) in available form. In this way, the digestate appears to be a very good candidate to replace inorganic fertilizers, also contributing, to the short-term soil organic matter turnover. PMID:20825964
Tambone, Fulvia; Scaglia, Barbara; D'Imporzano, Giuliana; Schievano, Andrea; Orzi, Valentina; Salati, Silvia; Adani, Fabrizio
Thermophilic Anaerobic Digester Performance Under Different Feed-Loading Frequency
The effect of feed-loading frequency on digester performance was studied on a thermophilic anaerobic digester with a working volume of 27.43 m3. The digester was fed 0.93 m3 of chicken-litter slurry/d, containing 50.9 g/L chemical oxygen demand. The treatments were loading frequencies of 1, 2, 6, and 12 times/d. The hourly pH, biogas production, and methane percent of the biogas were less stable at lower feed frequencies. There was no statistical difference among treatments in methanogenic activity. The feed-loading frequency of six times per day treatment provided the greatest biogas production.
Bombardiere, John; Espinosa-Solares, Teodoro; Domaschko, Max; Chatfield, Mark
Biogas production from anaerobic digestion of Spirulina maxima algal biomass
The photosynthetic spectrum of solar energy could be exploited for the production of chemical energy of methane through the combined algal-bacterial process. In this process, the algae are mass produced from light and from carbon in the first step. The algal biomass is then used as a nutrient for feeding the anaerobic digester, in the second step, for the production
Rejean Samson; Anh LeDuy
A field-scale research project was conducted in 2004-2005 to evaluate land application of anaerobically digested biosolids at agronomic levels. Biosolids had not been applied to this land previously. For this study, biosolids wee applied in a 100-m diameter circle by a side dis...
Dynamic modeling of mesophilic anaerobic digestion of animal waste
A mathematical model with time-varying parameters was developed to describe the dynamic behavior of the anaerobic mesophilic digestion of animal waste. Batch and continuous cases were considered. In the case of continuous process linearized models were proposed. Special emphasis was given to the parameters identification. Using sensitivity analysis and optimization software a simple methodology was developed. The model verification and
Iv. Simeonov; V. Momchev; D. Grancharov
Anaerobic Digestion. Instructor's Guide. Biological Treatment Process Control.
This instructor's guide contains materials needed to teach a four-lesson unit on anaerobic digestion control. These materials include: (1) unit overview; (2) lesson plans; (3) lecture outlines; (4) student worksheets for each lesson (with answers); and (5) two copies of a final quiz (with and without answers). Lesson 1 is a review of the theory of�
Carnegie, John W., Ed.
Anaerobic Digestion Analysis. Training Module 126.96.36.199.
This document is an instructional module package prepared in objective form for use by an instructor familiar with alkalinity, volatile acids and carbon dioxide determinations for an anaerobic sludge digester. Included are objectives, instructor guides, student handouts and transparency masters. This module considers total and bicarbonate�
Kirkwood Community Coll., Cedar Rapids, IA.
Anaerobic digestion of the liquid fraction of dairy manure
The authors tested several solid liquid separation systems suitable for processing dairy manure prior to anaerobic digestion. None of the systems tried have completely satisfied the requirements. Evaluated effects of separation on biogas production. Unseparated dairy manure produced more biogas than the liquid fraction.
Haugen, V.; Dahlberg, S.; Lindley, J.A.
Study of Resource Recovery and Epidemiology in an Anaerobic Digester.
Three 4-liter packed bed anaerobic digesters were fabricated and operated at 35 degrees C, pH around 7, and hydraulic retention time (HRT) of 20, 10 and 5 days to study the resource recovery and epidemiology in a controlled ecological life support system ...
K. Y. Li S. Cao M. D. Hunt X. Fu
Biogas Production by Anaerobic Digestion of Vegetable Matter.
A mixed cellulolytic culture was employed in anaerobic digestion tests. The start-up of the semi-continuous process was rapid and, after eight days of fermentation, a specific biogas production (0.38 m exp 3 /Kg VS added) which remained constant for about...
M. Gamboni F. Pacciaroni
Anaerobic digestion of polyelectrolyte flocculated waste activated sludge.
This work examined how adding one of three polyelectrolyte flocculants (T3052: cationic, T2000: non-ionic, and T1052: anionic) affected the anaerobic digestion of wastewater sludge. Methane production, floc characteristics (morphology and zeta-potential) and process parameters (soluble chemical oxygen demands (SCODs) and reductive potentials) were monitored along the digestion tests. The digestion rates of T2000- and T1052-conditioned sludge resembled that for original sludge. The T3052-flocculated sludge generated methane at a higher rate during the first 6 days of digestion than did the original one. In the following stage, the digestion rate of sludge flocculated with T3052 at dosage exceeding 15 g/kg dried solids declined. For example, at 40 days of digestion the methane production amounts for original, 15 g/kg DS flocculated, and 40 g/kg flocculated sludge were of 136, 105, and 85 g/kg DS, respectively. The role of flocculants could change in different stages of digestion. The dosed polymers had no apparent toxicity to the inoculum used. The changes in SCOD, adenosintriphosphate concentrations, oxidative and reductive potential, and zeta-potentials did not correlate with the noted hindered digestion for T3052-conditioned sludge. Microphotographic observation revealed that the flocs of T3052-conditioned sludge were not only of a large size, but also were resistant to structural deterioration during digestion. Therefore, mass transfer resistance was proposed to account for the hindered digestion efficiency observed for T3052-conditioned sludge. PMID:13129515
Chu, C P; Lee, D J; Chang, Bea-Ven; You, C H; Liao, C S; Tay, J H
Anaerobic digestion of crude glycerol: a review
Several researchers have used crude glycerol as a source of substrate for methane production and power generation, which is a way of adding value to this residue that has a high chemical oxygen demand (COD) and is rich in impurities. This review article summarizes recent data and discussions on the use of crude glycerol as substrate and co-substrate for anaerobic
M. B. Viana; A. V. Freitas; R. C. Leit�o; G. A. S. Pinto; S. T. Santaella
Anaerobic digestion of yard waste with hydrothermal pretreatment.
The digestibility of lignocellulosic biomass is limited by its high content of refractory components. The objective of this study is to investigate hydrothermal pretreatment and its effects on anaerobic digestion of sorted organic waste with submerged fermentation. Hydrothermal pretreatment (HT) was performed prior to anaerobic digestion, and three agents were examined for the HT: hot compressed water, alkaline solution, and acidic solution. The concentrations of glucose and xylose were the highest in the sample pretreated in acidic solution. Compared with that of the untreated sample, the biogas yields from digesting the samples pretreated in alkaline solution, acidic solution, and hot water increased by 364, 107, and 79%, respectively. The decrease of chemical oxygen demand (COD) in liquid phase followed the same order as for the biogas yield. The initial ammonia content of the treated samples followed the order sample treated in acidic solution > sample treated in alkaline solution > sample treated in hot water. The concentrations of volatile fatty acids (VFAs) were low, indicating that the anaerobic digestion process was running at continuously stable conditions. PMID:24425302
Li, Wangliang; Zhang, Guangyi; Zhang, Zhikai; Xu, Guangwen
Anaerobic Digestion I. Sludge Treatment and Disposal Course #166. Instructor's Guide [and] Student Workbook.
This lesson is the first of a two-part series on anaerobic digestion. Topics discussed include the five basic functions of an anaerobic digester, basic theory of the biological processes involved, basic equipment necessary for digestion, and the products of digestion. The lesson includes an instructor's guide and student workbook. The instructor's�
Optimizing the Logistics of Anaerobic Digestion of Manure
Electrical power production from the combustion of biogas from anaerobic digestion (AD) of manure is a means of recovering energy from animal waste. We evaluate the lowest cost method of moving material to and from centralized AD plants serving multiple confined feeding operations. Two areas are modeled, Lethbridge County, Alberta, Canada, an area of concentrated beef cattle feedlots, and Red Deer County, Alberta, a mixed-farming area with hog, dairy, chicken and beef cattle farms, and feedlots. We evaluate two types of AD plant: ones that return digestate to the source confined feeding operation for land spreading (current technology), and ones that process digestate to produce solid fertilizer and a dischargeable water stream (technology under development). We evaluate manure and digestate trucking, trucking of manure with return of digestate by pipelines, and pipelining of manure plus digestate. We compare the overall cost of power from these scenarios to farm or feedlot-based AD units. For a centralized AD plant with digestate return for land spreading the most economical transport option for manure plus digestate is by truck for the mixed-farming area and by pipelines for the concentrated feedlot area. For a centralized AD plant with digestate processing, the most economical transport option is trucking of manure for both cases.
Ghafoori, Emad; Flynn, Peter C.
A mass transfer model of ammonia volatilisation from anaerobic digestate
Anaerobic digestion (AD) is becoming increasingly popular for treating organic waste. The methane produced can be burned to generate electricity and the digestate, which is high in mineral nitrogen, can be used as a fertiliser. In this paper we evaluate potential losses of ammonia via volatilisation from food waste anaerobic digestate using a closed chamber system equipped with a sulphuric acid trap. Ammonia losses represent a pollution source and, over long periods could reduce the agronomic value of the digestate. Observed ammonia losses from the experimental system were linear with time. A simple non-steady-state partitioning model was developed to represent the process. After calibration, the model was able to describe the behaviour of ammonia in the digestate and in the trap very well. The average rate of volatilisation was approximately 5.2 g N m{sup -2} week{sup -1}. The model was used to extrapolate the findings of the laboratory study to a number of AD storage scenarios. The simulations highlight that open storage of digestate could result in significant losses of ammonia to the atmosphere. Losses are predicted to be relatively minor from covered facilities, particularly if depth to surface area ratio is high.
Whelan, M.J., E-mail: firstname.lastname@example.com [School of Applied Sciences, Cranfield University, College Road, Cranfield, Bedfordshire, MK43 0AL (United Kingdom); Everitt, T.; Villa, R. [School of Applied Sciences, Cranfield University, College Road, Cranfield, Bedfordshire, MK43 0AL (United Kingdom)
Anaerobic digestion of stillage to produce bioenergy in the sugarcane-to-ethanol industry.
Stillage is the main wastewater from ethanol production, containing a high chemical oxygen demand in addition to acidic and corrosive characteristics. Though stillage may be used as a soil fertilizer, its land application may be considered problematic due its high polluting potential. Anaerobic digestion represents an effective alternative treatment to reduce the pollution load of stillage. In addition, the methane gas produced within the process may be converted to energy, which can be directly applied to the treatment plant. The objective of this paper was to investigate the energetic potential of anaerobic digestion applied to stillage in the sugarcane ethanol industry. An overall analysis of the results indicates energy recovery capacity (ERC) values for methane ranging from 3.5% to 10%, respectively, for sugarcane juice and molasses. The processes employed to obtain the fermentable broth, as well as the distillation step, represent the main limiting factors to the energetic potential feasibility. Considering financial aspects the annual savings could reach up to US$ 30 million due to anaerobic digestion of stillage in relatively large-scale distilleries (365,000 m3 of ethanol per year). The best scenarios were verified for the association between anaerobic digestion of stillage and combustion of bagasse. In this case, the fossil fuels consumption in distilleries could be fully ceased, such the ERC of methane could reach values ranging from 140% to 890%. PMID:24600872
Fuess, Lucas Tadeu; Garcia, Marcelo Loureiro
Thermophilic two-stage dry anaerobic digestion of model garbage with ammonia stripping.
To avoid the inhibition of methane production by ammonia that occurs during the degradation of garbage, anaerobic digestion with prior ammonia production and subsequent stripping was investigated. In the ammonia production phase, the maximum ammonia concentration was approximately 2800 mg N/kg of total wet sludge in the range of 4 days of sludge retention time, indicating that only 43% of total nitrogen in the model garbage was converted to ammonia. The model garbage from which ammonia was produced and stripped was subjected to semi-continuous thermophilic dry anaerobic digestion over 180 days. The gas yield was in the range of 0.68 to 0.75 Nm(3)/kg volatile solid, and it decreased with the decrease of the sludge retention time. The ammonia-nitrogen concentration in the sludge was kept below 3000 mg N/kg total wet sludge. Microbial community structure analysis revealed that the phylum Firmicutes dominated in the ammonia production, but the community structure changed at different sludge retention times. In dry anaerobic digestion, the dominant bacteria shifted from the phylum Thermotogae to Firmicutes. The dominant archaeon was the genus Methanothermobacter, but the ratio of Methanosarcina increased during the process of dry anaerobic digestion. PMID:21094085
Yabu, Hironori; Sakai, Chikako; Fujiwara, Tomoko; Nishio, Naomichi; Nakashimada, Yutaka
The role of anaerobic digestion in the emerging energy economy.
Anaerobic digestion is the default process for biological conversion of residue organics to renewable energy and biofuel in the form of methane. However, its scope of application is expanding, due to availability of new technologies, and the emerging drivers of energy and nutrient conservation and recovery. Here, we outline two of these new application areas, namely wastewater nutrient and energy recovery, and generation of value added chemicals through mixed culture biotechnology. There exist two options for nutrient and energy recovery from domestic wastewater: low energy mainline and partition-release-recovery. Both are heavily dependent on anaerobic digestion as an energy generating and nutrient release step, and have been enabled by new technologies such as low emission anaerobic membrane processes. The area of mixed culture biotechnology has been previously identified as a key industrial opportunity, but is now moving closer to application due application of existing and new technologies. As well as acting as a core technology option in bioproduction, anaerobic digestion has a key role in residual waste valorization and generation of energy for downstream processing. These new application areas and technologies are emerging simultaneously with substantial advances in knowledge of underlying mechanisms such as electron transfer, understanding of which is critical to development of the new application areas. PMID:24534620
Batstone, Damien John; Virdis, Bernardino
Novel trends in anaerobic digestion of municipal solid waste.
Anaerobic digestion capacity has been installed on a large scale for the treatment of biowaste coming from municipal solid waste in the 90's. However, in recent years, a new trend has developed in which anaerobic digestion is applied more and more for the treatment of mixed or grey waste. It is expected that the installed capacity for grey/mixed waste will surpass the capacity installed for biowaste digestion. Five years ago, more than 85% of the treatment capacity was for biowaste digestion and only 15% for grey/mired waste digestion, derived from two old plants that were constructed prior to 1990. By the end of 2004, a digestion capacity of 1,285,000 ton per year will be available in Europe for the treatment of grey or mixed MSW, while digestion capacity for biowaste will only amount to 1,270,000 ton per year. Especially dry digestion offers new perspectives. Dry digestion is particularly suited for the treatment of grey/mixed waste due to its insensitivity to the presence of heavy inerts and light materials. Heavy inerts such as sand, glass and stones cause sedimentation and the light materials cause floatation and scum formation in the more conventional wet and semi-dry systems. Due to the high initial dry solids content, the digestate coming from dry digestion can be treated in a variety of ways. Besides the conventional mechanical dewatering, drying with waste heat or aerobic drying by addition of a fresh waste can be utilized for the production of a high-quality compost in case of the treatment of biowaste. Digestate from mixed or grey waste is not immediately suitable for the production of a high-quality compost. However, integration with incineration plants and landfills can be optimized easily with such a dry digestate and offers various interesting alternatives. In case a maximum of recyclables is pursued, the dry digestion can be followed by a wet separation in order to produce marketable endproducts such as sand and fibers. PMID:15296145
De Baere, Luc
Large eddy simulation of mechanical mixing in anaerobic digesters.
A comprehensive study of anaerobic digestion requires an advanced turbulence model technique to accurately predict mixing flow patterns because the digestion process that involves mass transfer between anaerobes and their substrates is primarily dependent on detailed information about the fine structure of turbulence in the digesters. This study presents a large eddy simulation (LES) of mechanical agitation of non-Newtonian fluids in anaerobic digesters, in which the sliding mesh method is used to characterize the impeller rotation. The three subgrid scale (SGS) models investigated are: (i) Smagorinsky-Lilly model, (ii) wall-adapting local eddy-viscosity model, and (iii) kinetic energy transport (KET) model. The simulation results show that the three SGS models produce very similar flow fields. A comparison of the simulated and measured axial velocities indicates that the LES profile shapes are in general agreement with the experimental data but they differ markedly in velocity magnitudes. A check of impeller power and flow numbers demonstrates that all the SGS models give excellent predictions, with the KET model performing the best. Moreover, the performance of six Reynolds-averaged Navier-Stokes turbulence models are assessed and compared with the LES results. PMID:22038563
Wu, Binxin
Structure of a cellulose degrading bacterial community during anaerobic digestion.
It is widely accepted that cellulose is the rate-limiting substrate in the anaerobic digestion of organic solid wastes and that cellulose solubilisation is largely mediated by surface attached bacteria. However, little is known about the identity or the ecophysiology of cellulolytic microorganisms from landfills and anaerobic digesters. The aim of this study was to investigate an enriched cellulolytic microbial community from an anaerobic batch reactor. Chemical oxygen demand balancing was used to calculate the cellulose solubilisation rate and the degree of cellulose solubilisation. Fluorescence in situ hybridisation (FISH) was used to assess the relative abundance and physical location of three groups of bacteria belonging to the Clostridium lineage of the Firmicutes that have been implicated as the dominant cellulose degraders in this system. Quantitation of the relative abundance using FISH showed that there were changes in the microbial community structure throughout the digestion. However, comparison of these results to the process data reveals that these changes had no impact on the cellulose solubilisation in the reactor. The rate of cellulose solubilisation was approximately stable for much of the digestion despite changes in the cellulolytic population. The solubilisation rate appears to be most strongly affected by the rate of surface area colonisation and the biofilm architecture with the accepted model of first order kinetics due to surface area limitation applying only when the cellulose particles are fully covered with a thin layer of cells. PMID:16142797
O'Sullivan, Cathryn A; Burrell, Paul C; Clarke, William P; Blackall, Linda L
Development of a new genetic algorithm to solve the feedstock scheduling problem in an anaerobic digester
As worldwide environmental awareness grow, alternative sources of energy have become important to mitigate climate change. Biogas in particular reduces greenhouse gas emissions that contribute to global warming and has the potential of providing 25% of the annual demand for natural gas in the U.S. In 2011, 55,000 metric tons of methane emissions were reduced and 301 metric tons of carbon dioxide emissions were avoided through the use of biogas alone. Biogas is produced by anaerobic digestion through the fermentation of organic material. It is mainly composed of methane with a rage of 50 to 80% in its concentration. Carbon dioxide covers 20 to 50% and small amounts of hydrogen, carbon monoxide and nitrogen. The biogas production systems are anaerobic digestion facilities and the optimal operation of an anaerobic digester requires the scheduling of all batches from multiple feedstocks during a specific time horizon. The availability times, biomass quantities, biogas production rates and storage decay rates must all be taken into account for maximal biogas production to be achieved during the planning horizon. Little work has been done to optimize the scheduling of different types of feedstock in anaerobic digestion facilities to maximize the total biogas produced by these systems. Therefore, in the present thesis, a new genetic algorithm is developed with the main objective of obtaining the optimal sequence in which different feedstocks will be processed and the optimal time to allocate to each feedstock in the digester with the main objective of maximizing the production of biogas considering different types of feedstocks, arrival times and decay rates. Moreover, all batches need to be processed in the digester in a specified time with the restriction that only one batch can be processed at a time. The developed algorithm is applied to 3 different examples and a comparison with results obtained in previous studies is presented.
Cram, Ana Catalina
Methane production from and beneficiation of anaerobic digestion of aquatic plant material
A process is disclosed for improved CH/sub 4/ production by anaerobic digestion of aquatic plant material, at least a portion or all which was grown in organically polluted water. Mixtures of aquatic plant material whose 1 portion was grown in nonpolluted and a 2nd portion comprising approximately 10 wt.% or more grown in organically polluted water can be used. The liquid effluent from the digester may be advantageously returned to the aquatic plant-growing pond to maintain the desired organic pollution. The process provides for improved CH/sub 4/ production from aquatic plant material which is, by itself, recalcitrant to anaerobic digestion. Thus, 2 digesters were operated under the same conditions, the 1st being fed with water hyacinth grown in nonorganic polluted hardwater of BOD 5 mg/l and hardness of 20 grains/gal. and the 2nd being fed with water hyacinth grown in sewage-polluted water of BOD 20 mg/l. Each digester was operated in a semicontinuous completely mixed anaerobic manner with a culture volume of 5 liters for a detention time of 12 days, a loading of 0.1 lb volatile solid/cubic feet-day, and 35/sup 0/ at pH of 6.8-7.1. The runs were contained for several detention times and exhibited stable performance. CH/sub 4/ yield increased approximately 69% and the gas-production rate increased approximately 82% by using water hyacinth feed grown in sewage-polluted water.
Klass, D.L.; Ghosh, S.
Novel anaerobic digestion process with sludge ozonation for economically feasible power production from biogas.
A novel process scheme was developed to achieve economically feasible energy recovery from anaerobic digestion. The new process scheme employs a hybrid configuration of mesophilic and thermophilic anaerobic digestion with sludge ozonation: the ozonated sludge is first degraded in a thermophilic digester and then further degraded in a mesophilic digester. In small-scale pilot experiments of the new process scheme, degradation of VSS improved by 3.5% over the control (mesophilic-only configuration) with 20% less ozone consumption. Moreover, biogas conversion also improved by 7.1% over the control. Selective enrichment of inorganic compounds during centrifugation produced a dewatered sludge cake with very low water content (59.4%). This low water content in the sludge cake improved its auto-thermal combustion potential during incineration and added to the overall energy savings. We conducted a case study to evaluate power generation from biogas for a municipal wastewater treatment plant with an average dry weather flow of 43,000 m3/d. Electricity production cost was 5.2 �/kWh for the advanced process with power generation, which is lower than the current market price of 7.2 �/kWh. The new anaerobic digestion scheme with power generation may reduce greenhouse gas emissions by about 1,000 t-CO(2)/year compared with the conventional process without power generation. PMID:21508552
Komatsu, K; Yasui, H; Goel, R; Li, Y Y; Noike, T
Electrolysis-enhanced anaerobic digestion of wastewater.
This study demonstrates enhanced methane production from wastewater in laboratory-scale anaerobic reactors equipped with electrodes for water electrolysis. The electrodes were installed in the reactor sludge bed and a voltage of 2.8-3.5 V was applied resulting in a continuous supply of oxygen and hydrogen. The oxygen created micro-aerobic conditions, which facilitated hydrolysis of synthetic wastewater and reduced the release of hydrogen sulfide to the biogas. A portion of the hydrogen produced electrolytically escaped to the biogas improving its combustion properties, while another part was converted to methane by hydrogenotrophic methanogens, increasing the net methane production. The presence of oxygen in the biogas was minimized by limiting the applied voltage. At a volumetric energy consumption of 0.2-0.3 Wh/L(R), successful treatment of both low and high strength synthetic wastewaters was demonstrated. Methane production was increased by 10-25% and reactor stability was improved in comparison to a conventional anaerobic reactor. PMID:21435864
Tartakovsky, B; Mehta, P; Bourque, J-S; Guiot, S R
The effects of digestion temperature and temperature shock on the biogas yields from the mesophilic anaerobic digestion of swine manure
In order to obtain basic design criteria for anaerobic digesters of swine manure, the effects of different digesting temperatures, temperature shocks and feed loads, on the biogas yields and methane content were evaluated. The digester temperatures were set at 25, 30 and 35�C, with four feed loads of 5%, 10%, 20% and 40% (feed volume\\/digester volume). At a temperature of
K. J. Chae; Am Jang; S. K. Yim; In S. Kim
Application of Anaerobic Digestion Model No. 1 to describe the syntrophic acetate oxidation of poultry litter in thermophilic anaerobic digestion.
A molecular analysis found that poultry litter anaerobic digestion was dominated by hydrogenotrophic methanogens which suggests that bacterial acetate oxidation is the primary pathway in the thermophilic digestion of poultry litter. IWA Anaerobic Digestion Model No. 1 (ADM1) was modified to include the bacterial acetate oxidation process in the thermophilic anaerobic digestion (TAD). Two methods for ADM1 parameter estimation were applied: manual calibration with non-linear least squares (MC-NLLS) and an automatic calibration using differential evolution algorithms (DEA). In terms of kinetic parameters for acetate oxidizing bacteria, estimation by MC-NLLS and DEA were, respectively, km 1.12 and 3.25�0.56kgCODkgCOD(-1)d(-1), KS 0.20 and 0.29�0.018kgCODm(-3) and Yac-st 0.14 and 0.10�0.016kgCODkgCOD(-1). Experimental and predicted volatile fatty acids and biogas composition were in good agreement. Values of BIAS, MSE or INDEX demonstrate that both methods (MC-NLLS and DEA) increased ADM1 accuracy. PMID:25011081
Rivera-Salvador, V�ctor; L�pez-Cruz, Irineo L; Espinosa-Solares, Teodoro; Aranda-Barradas, Juan S; Huber, David H; Sharma, Deepak; Toledo, J Ulises
Feasibility of anaerobic digestion from bioethanol fermentation residue.
The focus of this study was the reuse of red algal ethanol fermentation residue as feedstock for anaerobic digestion. Levulinic acid and formic acid, the dilute-acid hydrolysis byproducts, inhibited methanogenesis at concentrations over 3.0 and 0.5 g/L, respectively. However, the inhibition was overcome by increasing inoculum concentration. A series of batch experiments with the fermentation residue showed increased methane yield and productivity at higher inoculum concentration. The maximum methane conversion rate of 84.8% was found at 5 g COD/L of fermentation residue at 0.25 g COD/g VSS of food-to-microorganism (F/M) ratio. The red algal ethanol fermentation residue can possibly be used as a feedstock in anaerobic digestion at appropriate concentration and F/M ratio. PMID:23561951
Park, Jeong-Hoon; Kim, Sang-Hyoun; Park, Hee-Deung; Lim, Dong Jung; Yoon, Jeong-Jun
Conversion of carbohydrates in herbaceous crops during anaerobic digestion.
The methane yields and conversion of pentoses (xylose) and hexoses (cellulose) in hemp, maize, and white lupin were studied over 30 days of anaerobic digestion. Preservation of hemp increased the methane yield by 23% compared with the fresh hemp. The increased methane yield of hemp was verified by the enhanced conversion of C6 sugars, increasing from 48% to about 70%, whereas the conversion of C5 sugars increased from only 9% to nearly 50%. The consumption of all carbohydrates in fresh maize was almost complete in the 30 days of anaerobic digestion. Hence, there was no major difference in carbohydrate consumption between fresh and preserved maize during biogas production. Fresh white lupin produced the highest methane yield (343 � 33 dm(3) kg(-1) TS) in this work, mainly due to its highest amount of proteins. Conversion of C6 sugars was 80%, but that of C5 sugars was notably less at 46%. PMID:22788699
Pakarinen, Annukka; Kymalainen, Maritta; Stoddard, Frederick L; Viikari, Liisa
Production of Methane Biogas as Fuel Through Anaerobic Digestion
\\u000a Anaerobic digestion (AD) is a biotechnology by which biomass is converted by microbes to methane (CH4) biogas, which can then be utilized as a renewable fuel to generate heat and electricity. A genetically and metabolically\\u000a diverse community of microbes (mainly bacteria and methanogens) drives the AD process through a series of complex microbiological\\u000a processes in the absence of oxygen. During
Zhongtang Yu; Floyd L. Schanbacher
Potential of anaerobic digestion of complex waste (water)
Although they differ greatly in origin complex waste(water)s mainly consist of proteins, lipids, carbohydrates and sometimes lignin in addition. Hydrolysis is the first and generally rate-limiting step in the process of anaerobic digestion of particulate organic substrates. Hydrolysis of particulate polymers can be described by Surface Based Kinetics, but for use in practice the empirical first order relation is advised.
G. Zeeman; W. Sanders
There are more than 2,000 anaerobic digesters working with animal manure in EU countries, in parti- cular in Germany (more than 1,800), followed by Denmark, Austria, Italy and Sweden. It is estimated that biogas production in EU countries was 2762 ktep (32 million MWh) in 2002; 38% from biogas recupera- ted from MSW landfills. For Italy, in 2002, EurObserv'ER estimates
S. Piccinini
Anaerobic Digestion for Mitigation of Biodiesel Production Byproducts
NSDL National Science Digital Library
The Advanced Technology Environmental and Energy Center (ATEEC) provides this document, which was part of a workshop held on anaerobic digestion for mitigation of biodiesel production byproducts. It would be useful for instructors looking to develop their own curriculum on biofuels and biodiesel byproducts. Users must download this resource for viewing, which requires a free log-in. There is no cost to download the item.
Modeling temperature variations in a pilot plant thermophilic anaerobic digester
A model that predicts temperature changes in a pilot plant thermophilic anaerobic digester was developed based on fundamental\\u000a thermodynamic laws. The methodology utilized two simulation strategies. In the first, model equations were solved through\\u000a a searching routine based on a minimal square optimization criterion, from which the overall heat transfer coefficient values,\\u000a for both biodigester and heat exchanger, were determined.
Salvador Valle-Guadarrama; Teodoro Espinosa-Solares; Irineo L. L�pez-Cruz; Max Domaschko
State-of-the-art of anaerobic digestion technology for industrial wastewater treatment
Anaerobic digestion is the most suitable option for the treatment of high strength organic effluents. The presence of biodegradable components in the effluents coupled with the advantages of anaerobic process over other treatment methods makes it an attractive option. This paper reviews the suitability and the status of development of anaerobic reactors for the digestion of selected organic effluents from
K. V. Rajeshwari; M. Balakrishnan; A. Kansal; Kusum Lata; V. V. N. Kishore
Characteristics of carbohydrate degradation and the rate-limiting step in anaerobic digestion
The characteristics of the degradation of cellulose, soluble starch, and glucose in the acidogenic phase and the effects of the substrate loading rate and biological solids retention time on the methanogenic phase of anaerobic digestion were investigated. The results obtained from continuous experiments using laboratory-scale anaerobic chemostat reactors elucidated the true rate-limiting step of anaerobic digestion. The specific rate of
Tatsuya Noike; Ginro Endo; Juu-En Chang; Jun-Ichi Yaguchi; Jun-Ichiro Matsumoto
A coupling model for EGSB bioreactors: Hydrodynamics and anaerobic digestion processes
The aim of this paper is to present a coupling model for calculating both the hydrodynamic and anaerobic digestion processes in expanded granular sludge bed (EGSB) bioreactors for treating wastewaters. The bioreactor is modeled as a dynamic (gas�solid�liquid) three-phase system. An existing set of experimental data of three case studies based on the start-up and operational performance of EGSB reactors
Mauren Fuentes; Nicol�s J. Scenna; P�o A. Aguirre
Development of a pilot scale anaerobic digester for biogas production from cow manure and whey mix
This paper presents results from anaerobic digestion of cow manure and whey mix. A pilot scale anaerobic digester, 128l in volume, has been developed, to operate under batch and fed-batch conditions. The versatile and unique characteristics of the instrument allowed testing the methane production directly in the farm. The digester performance was evaluated with two calibration tests, the main for
Elena Comino; Maurizio Rosso; Vincenzo Riggio
Methane production by anaerobic digestion of water hyacinth (Eichhornia crassipes)
Water hyacinth under conventional high-rate digestion conditions exhibited higher methane yields and energy recovery efficiencies when grown in sewage-fed lagoons as compared to the corresponding values obtained with water hyacinth grown in a fresh-water pond. Mesophilic digestion provided the highest feed energy recovered in the product gas as methane while thermophilic digestion, when operated at sufficiently high loading rates and reduced detention times, gave the highest specific methane production rates. Methane yields, volatile solids reduction, and energy recovery as methane for the sewage-grown water hyacinth were in the same range as those observed for other biomass substrates when digested under similar conditions.
Water hyacinth under conventional high-rate digestion conditions exhibited higher CH4 yields and energy recovery efficiencies when grown in sewage-fed lagoons than when grown in a fresh water pond. Mesophilic digestion provided the highest recovery of feed energy in the product gas as CH4, while thermophilic digestion, when operated at sufficiently high loading rates and reduced detention times, gave the highest specific CH4 production rates. CH4 yields, volatile solids reduction, and energy recovery as CH4 from the sewage-grown water hyacinth were in the same range as those observed for other biomass substrates when digested under similar conditions.
Novel two-phase anaerobic gasification with solid-bed acid digestion in tandem with fixed-film methane fermentation
The development and performance of a novel solid-bed two-phase anaerobic digestion system are described. The system consists of a bed of organic feed operated in tandem with an acid-phase slurry digester and a methane-phase upflow anaerobic filter. The bed and the acid-phase digesters liquefy and convert the organics to volatile fatty acids (VFA) without gas production, while a high methane-content product gas is collected from the methane-phase filter. With municipal refuse feeds, VFA and ethanol were the major products from acid-phase digestion. A high methane content (up to 88 mol %) gas was the major product from the methane phase filter.
Ghosh, S.; Henry, M.P.; Sajjad, A.
Liquid-liquid extraction of short-chain organic acids from anaerobic digesters
Anaerobic digesters with glucose or municipal solid waste (MSW) feed were operated to maximize production of short-chain organic acids. Digester effluent was extracted by liquid-liquid extraction with trioctylphosphine oxide (TOPO) or trioctylamine (TOA) in heptane or 2-heptanone as the water immiscible phase. Digester effluent was recycled to digesters after extraction. Both TOPO and TOA in organic solvents effectively extract organic acids from anaerobic digester fluid. Longer chain acids have a higher distribution coefficient than shorter-chain acids. Long term extraction of digester fluid with recycle was not toxic to the anaerobic production of short-chain acids.
Wene, E.G.; Antonopoulos, A.A.
Digesters and demographics: identifying support for anaerobic digesters on dairy farms.
The dairy industry in the United States is amidst a long-running trend toward fewer, larger dairy farms. This development has created a backlash in some communities over concerns such as odor, waste management, and environmental degradation. Separately, anaerobic digestion has advanced as a waste management technology that potentially offers solutions to some of these issues, providing odor control and a combustible biogas among other things. These digesters require significant capital investments. Voluntary consumer premiums for the renewable energy produced have been used in some instances as a means to move adoption of such systems toward financial feasibility. This project employed a survey to measure Ohio consumers' willingness to pay a premium for renewable energy produced by anaerobic digesters on dairy farms. Cluster analysis was used to segment consumers by willingness to pay, age, education, income, self-identified political inclination, and a composite variable that served as a proxy for respondents' environmental stewardship. Four distinctive groups emerged from the data. Older, less educated respondents were found to have the least amount of support for digesters on dairy farms, whereas politically liberal, environmentally proactive respondents demonstrated the strongest support. Well-educated, affluent respondents and young respondents fell between these 2 groups. Most large dairy farms are generally met with fairly negative responses from their local communities; in contrast, this research finds some popular support for anaerobic digestion technology. Going forward, establishing a positive link between support for anaerobic digesters and for their use on large dairies could open up a new route for less-contested large dairy farm developments. Evaluation of community demographics could become an important part of finding an optimal location for a large dairy farm. PMID:20965366
Sanders, D J; Roberts, M C; Ernst, S C; Thraen, C S
Survey of the Anaerobic Biodegradation Potential of Organic Chemicals in Digesting Sludge
The degradation potential of 77 organic chemicals under methanogenic conditions was examined with an anaerobic digesting sludge from the United Kingdom. Degradation was assessed in terms of net total gas (CH4 plus CO2) produced, expressed as a percentage of the theoretical production (ThGP). The compounds tested were selected from various chemical groups and included substituted phenols and benzoates, pesticides, phthalic acid esters, homocyclic and heterocyclic ring compounds, glycols, and monosubstituted benzenes. The results obtained were in good agreement with published surveys of biodegradability in U.S. digesting sludges and other methanogenic environments. In general, the presence of chloro or nitro groups inhibited anaerobic gas production, while carboxyl and hydroxyl groups facilitated biodegradation. The relationship between substituent position and susceptibility to methanogenic degradation was compound dependent. The following chemicals were completely degraded (?80% ThGP) at a concentration of 50 mg of carbon per liter: phenol, 2-aminophenol, 4-cresol, catechol, sodium benzoate, 4-aminobenzoic acid, 3-chlorobenzoic acid, phthalic acid, ethylene glycol, diethylene glycol, triethylene glycol, sodium stearate, and quinoline. 3-Cresol, 4-chlorobenzoic acid, dimethyl phthalate, and pyridine were partially degraded. Although the remaining chemicals tested were either persistent or toxic, their behavior may differ at more environmentally realistic chemical-to-biomass ratios. Our findings suggest that biodegradability assessments made with sludge from one source can be extrapolated to sludge from another source with a reasonable degree of confidence and should help in predicting the fate of an organic chemical during the anaerobic digestion of sewage sludge.
Battersby, Nigel S.; Wilson, Valerie
Optimizing the logistics of anaerobic digestion of manure.
Electrical power production from the combustion of biogas from anaerobic digestion (AD) of manure is a means of recovering energy from animal waste. We evaluate the lowest cost method of moving material to and from centralized AD plants serving multiple confined feeding operations. Two areas are modeled, Lethbridge County, Alberta, Canada, an area of concentrated beef cattle feedlots, and Red Deer County, Alberta, a mixed-farming area with hog, dairy, chicken and beef cattle farms, and feedlots. We evaluate two types of AD plant: ones that return digestate to the source confined feeding operation for land spreading (current technology), and ones that process digestate to produce solid fertilizer and a dischargeable water stream (technology under development). We evaluate manure and digestate trucking, trucking of manure with return of digestate by pipelines, and pipelining of manure plus digestate. We compare the overall cost of power from these scenarios to farm or feedlot-based AD units. For a centralized AD plant with digestate return for land spreading the most economical transport option for manure plus digestate is by truck for the mixed-farming area and by pipelines for the concentrated feedlot area. For a centralized AD plant with digestate processing, the most economical transport option is trucking of manure for both cases.However, for the concentrated feedlot area, pipeline transport of manure is close in cost to trucking, and the impact of truck congestion would likely lead to selection of pipeline transport. For the mixed-farming area, centralized AD is more economical than for any individual farm or feedlot unit. For the concentrated feedlot area, a centralized AD plant is less economical than a feedlot-based AD unit more than 55,000 head (digestate return) and 300,000 head (digestate processing). The study demonstrates the viability of centralized AD plants vs farm-based units in most farming environments, and that careful analysis of the cost of pipeline vs truck transport of manure and digestate is required on a case-by-case basis. PMID:18478421
Ghafoori, Emad; Flynn, Peter C
Anaerobic digestion of glycerol derived from biodiesel manufacturing.
The anaerobic digestion of glycerol derived from biodiesel manufacturing, in which COD was found to be 1010 g/kg, was studied in batch laboratory-scale reactors at mesophilic temperature using granular and non-granular sludge. Due to the high KOH concentration of this by-product, H(3)PO(4) was added to recover this alkaline catalyst as agricultural fertilizer (potassium phosphates). Although it would not be economically viable, a volume of glycerol was distilled and utilised as reference substrate. The anaerobic revalorisation of glycerol using granular sludge achieved a biodegradability of around 100%, while the methane yield coefficient was 0.306 m(3) CH(4)/kg acidified glycerol. Anaerobic digestion could be a good option for revalorising this available, impure and low priced by-product derived from the surplus of biodiesel companies. The organic loading rate studied was 0.21-0.38 g COD/g VSS d, although an inhibition phenomenon was observed at the highest load. PMID:19592236
Siles L�pez, Jos� Angel; Mart�n Santos, Mar�a de Los Angeles; Chica P�rez, Arturo Francisco; Mart�n Mart�n, Antonio
Microbial ecology of anaerobic digesters: the key players of anaerobiosis.
Anaerobic digestion is the method of wastes treatment aimed at a reduction of their hazardous effects on the biosphere. The mutualistic behavior of various anaerobic microorganisms results in the decomposition of complex organic substances into simple, chemically stabilized compounds, mainly methane and CO2. The conversions of complex organic compounds to CH4 and CO2 are possible due to the cooperation of four different groups of microorganisms, that is, fermentative, syntrophic, acetogenic, and methanogenic bacteria. Microbes adopt various pathways to evade from the unfavorable conditions in the anaerobic digester like competition between sulfate reducing bacteria (SRB) and methane forming bacteria for the same substrate. Methanosarcina are able to use both acetoclastic and hydrogenotrophic pathways for methane production. This review highlights the cellulosic microorganisms, structure of cellulose, inoculum to substrate ratio, and source of inoculum and its effect on methanogenesis. The molecular techniques such as DGGE (denaturing gradient gel electrophoresis) utilized for dynamic changes in microbial communities and FISH (fluorescent in situ hybridization) that deal with taxonomy and interaction and distribution of tropic groups used are also discussed. PMID:24701142
Ali Shah, Fayyaz; Mahmood, Qaisar; Maroof Shah, Mohammad; Pervez, Arshid; Ahmad Asad, Saeed
Anaerobic digestion of solid wastes of cane sugar industry
The cane sugar manufacturing industry generates large quantities of lignocellulosic solid wastes, namely bagasse and cachaza. Bagasse is the fibrous residue of the cane after extracting the juice. Cachaza is the filter cake of the precipitated insoluble sugars. This research investigates the feasibility of anaerobic digestion of a mixture of bagasse and cachaza to produce methane. Two rations of bagasse-cachaza mix as substrates were investigated. The first one was 8:1 which represents the average ratio of bagasse and cachaza produced in a raw sugar mill. The second ratio investigated was 2.4:1 which represents the proportion of bagasse and cachaza wastes after 70% of the bagasse is burned in sugar mill boilers. An acclimated microbial culture for this substrate was developed. Organic Loading-Detention Time relationships were established for an optimum system. Pre-treatment techniques of the substrate were investigated as a means of enhancing the digestibility of the cellulosic substrate. Recirculation of the filtrate was evaluated as a method for increasing solids retention time without increasing hydraulic detention time. The kinetics of the digestion process for bagasse-cachaza mixed substrate was investigated and growth constants were determined. The bionutritional characteristics of the substrate used for the digestion were evaluated. Based on the results obtained, mass balances and preliminary economic analysis of the digestion system were developed.
Dasgupta, A.
Thermophilic anaerobic digester with ultrafilter for solids stabilization.
A thermophilic anaerobic digester with ultrafilter (TADU) for solids separation offers potential advantages of higher VS destruction, biomass retention, and pathogen removal. However, potential disadvantages include ultrafilter fouling, decreasing flux, and high VFA concentrations. In this study, a thermophilic anaerobic digester coupled to a sintered titanium, cross-flow ultrafilter was operated for over five months. Dairy manure was digested (HRT of 23 days). The filtrate VFA concentration was low (220 mg/L as HAc), average VS destruction was 49%, and a low average effluent fecal coliform concentration of 10(2) MPN/100 mL was observed. The low coliform value may be beneficial if dewatered biosolids are used for livestock bedding since low pathogen counts help prevent mastitis. Ultrafilter fluxes of 40-80 L/m2-hr were maintained by cleaning using caustic (3.5% NaOH) followed by water and acid (3% phosphoric acid). Sand from livestock bedding was found to damage the pump and ultrafilter. If TADU were implemented at full scale, then replacing sand bedding with dewatered biosolids should be considered. PMID:16180473
Zitomer, D H; Bachman, T C; Vogel, D S
Flow pattern visualization in a mimic anaerobic digester: experimental and computational studies.
Advanced non-invasive experiments like computer automated radioactive particle tracking and computed tomography along with computational fluid dynamics (CFD) simulations were performed in mimic anaerobic digesters to visualize their flow pattern and obtain hydrodynamic parameters. The mixing in the digester was provided by sparging gas at three different flow rates. The simulation results in terms of overall flow pattern, location of circulation cells and stagnant regions, trends of liquid velocity profiles, and volume of dead zones agree reasonably well with the experimental data. CFD simulations were also performed on different digester configurations. The effects of changing draft tube size, clearance, and shape of the tank bottoms were calculated to evaluate the effect of digester design on its flow pattern. Changing the draft tube clearance and height had no influence on the flow pattern or dead regions volume. However increasing the draft tube diameter or incorporating a conical bottom design helped in reducing the volume of the dead zones as compared to a flat bottom digester. The simulations showed that the gas flow rate sparged by a single point (0.5 cm diameter) sparger does not have appreciable effect on the flow pattern of the digesters. PMID:16180475
Vesvikar, M S; Varma, R; Karim, K; Al-Dahhan, M
Biogas generation from in-storage psychrophilic anaerobic digestion.
In-storage psychrophilic anaerobic digestion (ISPAD) is a technology allowing livestock producers to operate an anaerobic digester with minimum technological know-how and for the cost of a conventional storage cover. Nevertheless, the system is exposed to ambient temperatures and biogas production is expected to vary with climatic conditions. The objective of the project was therefore to measure ISPAD biogas production during the winter and fall seasons for a region east of Montreal, Canada. A calibrated biogas monitoring system was used to monitor biogas methane and carbon dioxide concentrations inside a two-year-old field installation with a 1000 m3 storage capacity. Despite a leaking pumping hatch, winter 2010 (January to March) methane concentrations varied directly with solar radiation and maximum exterior temperature, rather than with manure temperature at 2.4 and 1.2 m depths which remained relatively constant between 1 and 5 degrees C. During a six-month-period from November 2009 to April 2010, inclusively, the field ISPAD degraded 34% of the manure volatile solids corresponding to an average methane production of 40 m3/d. The ISPAD biogas production could be further increased by improving its air tightness and intrusion and by regularly pumping out the biogas. PMID:23837352
Giard, David; Choiniere, Denis; Cordeau, S�bastien; Barrington, Suzelle
Thermochemical Pretreatment for Anaerobic Digestion of Sorted Waste
The effect of alkaline hydrothermal pre-treatment for anaerobic digestion of mechanically-sorted municipal solid waste (MSW) and source-sorted waste was studied. Waste was hydrothermally pre-treated in dilute alkali solution. Hydrolysis product was incubated in 500 ml saline bottle to determine methane potential (MP) under mesospheric anaerobic conditions. Optimum reaction condition obtained in the study is 170 �C at the dose of 4 g NaOH/100 g solid for one hour. Soluble COD was 13936 mg/L and methane yield was 164 ml/g VS for 6 days incubation at optimum conditions. More than 50% biogas increase was achieved over the control, and methane conversion ratio on carbon basis was enhanced to 30.6%. The digestion period was less than 6 days when pre-treatment temperature was above 130 �C. The organic part of sorted waste is mainly constituted of kitchen garbage and leaf. Model kitchen garbage was completely liquidized at 130 �C for one hour and the methane yield was 276 ml/g VS. Addition of alkali enhance hydroxylation rate and methane yield slightly. The biogas potential of leaf could be observed by pre-treatment above 150 �C under alkaline condition.
Hao, W.; Hongtao, W.
Methanogenic potential of formate in thermophilic anaerobic digestion.
In the present study the methanogenic potential of formate (HCOO(-)) during thermophilic anaerobic digestion was investigated. After appropriate conditions for methanogenesis (HCOO(-) and inoculum concentration, pH and duration of incubation) were assessed, an experiment with initial 31 replicates was run. Diluted fermenter sludge was used as inoculum, and process parameters including the pH, quality and quantity of the produced biogas and the concentrations of volatile fatty acids and HCO(3) (-) were determined. Remarkably, after 5 days of incubation the highest CH(4) production was calculated for a HCOO(-) concentration of 200 mmol L(-1), a concentration, however, which might not occur in situ. During the phase of high CH(4) production HCOO(-) was degraded with a rate of 1.5 mmol L(-1) h(-1), and distinct changes of Gibbs free energy for several reactions were observed. Based on denaturing high-performance liquid chromatography, denaturing gradient gel electrophoresis, and additional subsequent sequencing approaches the hydrogenotrophic Methanothermobacter wolfeii was the dominant methanogen responsible for CH(4) production. Further confirmation was achieved due to the detection of autofluorescing rods with a size of up to ~3 �m, which were often arranged in pairs and chains. It was shown that even high concentrations of HCOO(-) are readily degraded, which might lead to an underestimation of both, the concentration and thus, the importance of HCOO(-) in anaerobic digestion. PMID:22588113
Lins, Philipp; Schwarzenauer, Thomas; Reitschuler, Christoph; Wagner, Andreas O; Illmer, Paul
Effect of shear on performance and microbial ecology of continuously stirred anaerobic digesters treating animal manure
We determined the effect of different mixing intensities on the performance, methanogenic population dynamics, and juxtaposition of syntrophic microbes in anaerobic digesters treating cow manure from a dairy farm. Computer automated radioactive particle tracking in con- junction with computational fluid dynamics was performed to quantify the shear levels locally. Four continuously stirred anaerobic digesters were operated at different mixing inten-
Rebecca A. Hoffmann; Marcelo L. Garcia; Mehul Veskivar; Khursheed Karim; Muthanna H. Al-Dahhan; Largus T. Angenent
Digested Sewage Sludge as Seed for Batch Test of Anaerobic Biodegradability
Research was carried out to optimize the use of digested sewage sludge (DSS) as a seed for batch tests of food waste anaerobic biodegradability. Digested sewage sludge was used as the seed because of its abundant supply and previous use as a seed. A seed volume of 1:1 g VS basis to the substrate provided a stable anaerobic process, however
Nastaein Qamaruz-Zaman; Mark W. Milke
Method for the anaerobic digestion of solid organic waste
US Patent & Trademark Office Database
The present invention relates to a method wherein solid organic waste originating from plants or animals or both, is digested by an anaerobic fermentation, that is less labor, time and space consuming than the conventional aerobic fermentation method, and may be performed with waste that has not to be subjected to a pre-treatment wherein a slurry having a rather low solids content is prepared. According to the present method solid organic waste originating from plants or animals or both is decomposed under anaerobic conditions in at least one primary reactor, whereupon the water soluble fatty acids formed by said decomposition together with other soluble organic and inorganic substances are removed to a substantial extent by rinsing with an aqueous liquid in order to avoid that in the reactor the concentration of fermentation inhibiting substances becomes too high and/or the pH of the contents of the reactor becomes too low, and the solution thus formed is fed to at least one auxiliary reactor wherein the organic material is converted into a mixture of carbon dioxide and methane under anaerobic conditions in a way known per se and the sludge formed in the primary reactor is removed therefrom.
Development of an advanced anaerobic digester design and a kinetic model for biogasification of water hyacinth/sludge blends
The Institute of Gas Technology (IGT) conducted a comprehensive laboratory-scale research program to develop and optimize the anaerobic digestion process for producing methane from water hyacinth and sludge blends. This study focused on digester design and operating techniques, which gave improved methane yields and production rates over those observed using conventional digesters. The final digester concept and the operating experience was utilized to design and operate a large-scale experimentla test unit (ETU) at Walt Disney World, Florida. This paper describes the novel digester design, operating techniques, and the results obtained in the laboratory. The paper also discusses a kinetic model which predicts methane yield, methane production rate, and digester effluent solids as a function of retention time. This model was successfully utilized to predict the performance of the ETU. 15 refs., 6 figs., 6 tabs.
Srivastava, V.; Fannin, K.F.; Biljetina, R.; Chynoweth, D.P.; Hayes, T.D.
Utilisation of energy from digester gas and sludge incineration at Hamburg's K�hlbrandh�ft WWTP.
At Hamburg's K�hlbrandh�ft WWTP the demand for external energy supply is minimised by state of the art sludge treatment. The sludge is subjected to thickening, anaerobic digestion, dewatering, drying and incineration. The digester gas is used in a combined gas and steam turbine process. The sludge incineration also produces steam, which is also used in the steam turbine that follows the gas turbine. The turbines produce electricity, partially expanded steam is used for the sludge drying process. Heat from the condensation of vapours from sludge drying is used to heat the anaerobic digesters. The overall process requires no external heat or fuel and produces 60% of the WWTP's electricity demand. PMID:12361039
Thierbach, R D; Hanssen, H
Impact of food industrial waste on anaerobic co-digestion of sewage sludge and pig manure
The performance of an anaerobic digestion process is much dependent on the type and the composition of the material to be digested. The effects on the degradation process of co-digesting different types of waste were examined in two laboratory-scale studies. In the first investigation, sewage sludge was co-digested with industrial waste from potato processing. The co-digestion resulted in a low
M Murto; L Bj�rnsson; B Mattiasson
Use of hydrodynamic disintegration to accelerate anaerobic digestion of surplus activated sludge.
Hydrodynamic disintegration of activated sludge resulted in organic matter and polymers transfer from the solid phase into the liquid phase. Disintegration by hydrodynamic cavitation had a positive effect on the degree and rate of excess sludge anaerobic digestion. Also, addition of a part of anaerobic digested sludge containing adapted microorganisms resulted in acceleration of the process. The disruption of cells of foam microorganisms and addition to the digestion process led to an increase of biogas production. PMID:20099626
Gr�bel, Klaudiusz; Machnicka, Alicja
Stabilization and gasification of soft-drink manufacturing waste by conventional and two-phase anaerobic digestion
Energy recovery and waste stabilization accomplished simultaneously in the beverage industry by anaerobic digestion are investigated. The applicability and limitation of the conventional high-rate anaerobic digestion process are tested. A rapid-rate waste conversion process, two-phase anaerobic digestion, developed for enhanced net energy production with COD reduction comparable to that obtainable by application of a conventional digestion process is discussed. The high-rate digestion run was developed from a mixed MSW-sludge-biomass-fed inoculum.
Ghosh, S.; Henry, M.P.
Application of low-strength ultrasonication to the continuous anaerobic digestion processes: UASBr and dry digester.
In this study, the positive effects of low-strength ultrasonication (LS-ultrasonication) on the anaerobic digestion (AD) performance were investigated by continuously operating an upflow anaerobic sludge blanket reactor (UASBr) and a dry digester. In the ultrasonicated UASBr system (1 s per min, 0.05 W/mL), ultrasonication enhanced the CH? production by 38% and 19% in an ambient and a mesophilic condition, respectively. In addition, a different sludge yield and a changed electron flow were observed after ultrasonication. In the ultrasonicated dry digestion system (2 s per 30 s, 0.0025 W/mL), a 40% increase in the production of CH? was observed after lowering the total solid content of the reactor from 12% to 10%, implying that a high solid content diminished the ultrasonic stimulation effect. Moreover, the ultrasonication strength itself appeared to be a more crucial factor than the ultrasonication density during the application of LS-ultrasonication in the AD system. PMID:23582223
Cho, Si-Kyung; Kim, Dong-Hoon; Jeong, In-Seok; Shin, Hang-Sik; Oh, Sae-Eun
Thermophilic anaerobic digestion: the best option for waste treatment.
After introducing thermophilic anaerobic digestion (AD), characteristics of thermophilic methanogens are provided. Accordingly, (a) site of occurrence, (b) morphological characteristics (shape and motility), (c) biochemical characteristics (Gram character and % G+C profile), (d) nutritional characteristics (NaCl requirement and substrate specificity), and (e) growth characteristics (pH and temperature) of thermophilic methanogens are described. Some studies of the thermophilic AD are cited with their operational management problems. Subsequently, strategies to maximize net energy production are given, including mode of heating the bioreactors, role of agitation to promote AD performance and mode/intensity of mixing. Finally, advantages as well as drawbacks of AD under thermophilic conditions are given, concluding with its applications. PMID:20148754
Suryawanshi, P C; Chaudhari, A B; Kothari, R M
Anaerobic digestion of wheat straw--performance of continuous solid-state digestion.
In this study the upflow anaerobic solid-state (UASS) reactor was operated at various conditions to optimize the process parameters for anaerobically digesting wheat straw in a continuous process. Additionally, particle size effects have been studied in the operation at 55 and 60�C. Moreover, the incremental effect of the organic loading rate (OLR) to the system was examined from 2.5 to 8 gVS L(-1) d(-1). It was found that the UASS operating at 60 �C with a small OLR yields highest methane production, but the advantage over thermophilic operation is negligible. The rise in OLR reduces the systems yields, as expected. From OLR=8 gVS L(-1) d(-1) a second stage is necessary to circumvent volatile fatty acids accumulation. PMID:23954246
Pohl, Marcel; Heeg, Kathrin; Mumme, Jan
Solubilization of particulate organic carbon during the acid phase of anaerobic digestion
Hydrolysis of particulates to soluble substrates rather than bacterial growth was the rate-limiting step during the acid phase of anaerobic digestion of sewage sludge, and pH had a greater effect on the process than did influent solids concentrations, suggesting that digestability can be improved for highly variable feed sludges by separate phase digestion for acid production and CH� production. Carbohydrates
J. A. Eastman; J. F. Ferguson
Anaerobic digestion and horticultural value of solid waste from manufacture of instant coffee
Anaerobic methanogenic thermophilic digestion (AMTD) of the solid fraction of waste from an instant coffee factory was carried out in laboratory scale digesters. Optimal conditions were established for stable fermentation by controlling loading rates, pH, volatile fatty acid concentrations, biogas production and composition. The results of the experiments indicated that steady digestion can be maintained at organic loading rates up
D. Kostenberg; U. Marchaim
Comparison of non-agitated and agitated batch, thermophilic anaerobic digestion of sugarbeet tailings.
Sugar beet tailings were anaerobically digested at non-agitated and agitated conditions in identical thermophilic batch reactors. The average methane yield in the agitated digester was only 74% of that in the non-agitated digester. Ninety percent of the ultimate methane yield was produced in approximately 5 days in the non-agitated digester whereas it took 12 days in agitated digester. Even upon using an active inoculum from non-agitated digester the methane rate and yield was low in the agitated digester. On the other hand when the poorly performing inoculum from the agitated digester was transferred to the non-agitated digester, its activity was immediately enhanced. The non-agitated digester harbored a diverse microbial community with phylotypes Methanoculleus and Methanosarcina being dominant methanogens. Methanosaeta was the only methanogen detected in the agitated digester. It also contained a hydrogen-producing bacterial phylotype Petrotoga in high proportion which was not detected in the other digester. PMID:23262019
Tian, Zhuoli; Chauliac, Diane; Pullammanappallil, Pratap
Investigation of Non-Newtonian Flow in Anaerobic Digesters
This thesis examines how the non-Newtonian characteristics of liquid hog manure affect the flow conditions within a steady-flow anaerobic digester. There are three main parts to this thesis. In the first part of this thesis, the physical properties of liquid hog manure and their variation with temperature and solids concentration are experimentally determined. Naturally-settled manure sampled from an outdoor storage lagoon is studied, and density, viscosity, and particle size distribution are measured. Hog manure with total solids concentrations of less than 3.6% exhibits Newtonian behaviour; manure between 3.6% and 6.5% total solids is pseudoplastic, and fits the power law; manure with more than 6.5% total solids exhibits non-Newtonian and time-dependent characteristics. The second part of this thesis investigates the flow of Newtonian and non-Newtonian fluids---represented by tap water and xanthan gum solution, respectively---within four lab-scale reactor geometries, using residence time distribution (RTD) experiments. The effect of reactor geometry, flow rate, and fluid viscosity are evaluated. In the third part of this thesis, flow conditions within lab-scale and pilot-scale anaerobic digester reactors are simulated using three-dimensional modeling techniques. The RTDs of lab-scale reactors as predicted by the 3D numerical models compare well to the experimental results. The 3D models are also validated using data from particle image velocimetry (PIV) experiments. Finally, the viscous properties of liquid hog manure at 3% and 8% total solids are incorporated into the models, and the results are evaluated.
Langner, Jeremy M.
Biomass production, anaerobic digestion, and nutrient recycling of small benthic or floating seaweeds
A number of experiments have been carried out supporting the development of a seaweed-based ocean energy farm. Beginning in 1976, forty-two species of seaweed indigenous to the coastal waters of Central Florida were screened for high biomass yields in intensive culture. Gracilaria tikvahiae achieved the highest annual yield of 34.8 g dry wt/m/sup 2/ day. Yield has been found to vary inversely with seawater exchange rate, apparently because of carbon dioxide limitation at low exchange rates. Gracilaria was anaerobically digested in 120 liter and 2 liter reactors. Gas yields in the large digesters averaged 0.4 1/g volatile solids (.24 1 CH/sub 4//gv.s.) with a bioconversion efficiency of 48%. Studies of the suitability of digester residue as a nutrient source for growing Gracilaria have been conducted. Nitrogen recycling efficiency from harvested plant through liquid digestion residue to harvested plant approached 75%. Studies of nutrient uptake and storage by Gracilaria, Ascophyllum, and Sargassum showed that nutrient starved plants are capable of rapidly assimilating and storing inorganic nutrients which may be used later for growth when no nutrients are present in the medium. A shallow water seaweed farm was proposed which would produce methane from harvested seaweed and use digester residues as a concentrated source of nutrients for periodic fertilizations.
Ryther, J.H.
The effects of different mixing intensities during anaerobic digestion of the organic fraction of municipal solid waste.
Mixing inside an anaerobic digester is often continuous and is not actively controlled. The selected mixing regime can however affect both gas production and the energy efficiency of the biogas plant. This study aims to evaluate these effects and compare three different mixing regimes, 150 RPM and 25 RPM continuous mixing and minimally intermittent mixing for both digestion of fresh substrate and post-digestion of the organic fraction of municipal solid waste. The results show that a lower mixing intensity leads to a higher biogas production rate and higher total biogas production in both cases. 25 RPM continuous mixing and minimally intermittent mixing resulted in similar biogas production after process stabilization, while 150 RPM continuous mixing resulted in lower production throughout the experiment. The lower gas production at 150 RPM could not be explained by the inhibition of volatile fatty acids. Cumulative biogas production until day 31 was 295 � 2.9, 317 � 1.9 and 304 � 2.8N ml/g VS added during digestion of fresh feed and 113 � 1.3, 134 � 1.1 and 130 � 2.3N ml/g VS added during post digestion for the 150 RPM, 25 RPM and minimally mixed intensities respectively. As well as increasing gas production, optimal mixing can improve the energy efficiency of the anaerobic digestion process. PMID:24814768
Lindmark, Johan; Eriksson, Per; Thorin, Eva
Data summary of municipal solid waste management alternatives. Volume 10, Appendix H: Anaerobic digestion of MSW
While municipal solid waste (MSW) thermoconversion and recycling technologies have been described in Appendices A through E, this appendix addresses the role of bioconversion technologies in handling the organic fraction in MSW and sewage sludge. Much of the organic matter in MSW, consisting mainly of paper, food waste, and yard waste, has potential for conversion, along with sewage sludge, through biochemical processes to methane and carbon dioxide providing a measurable, renewable energy resource potential. The gas produced may be treated for removal of carbon dioxide and water, leaving pipeline quality gas. The process also has the potential for producing a stabilized solid product that may be suitable as a fuel for combustion or used as a compost fertilizer. Anaerobic digestion can occur naturally in an uncontrolled environment such as a landfill, or it can occur in a controlled environment such as a confined vessel. Landfill gas production is discussed in Appendix F. This appendix provides information on the anaerobic digestion process as it has been applied to produce methane from the organic fraction of MSW in enclosed, controlled reactors.
Survey of the anaerobic biodegradation potential of organic chemicals in digesting sludge.
The degradation potential of 77 organic chemicals under methanogenic conditions was examined with an anaerobic digesting sludge from the United Kingdom. Degradation was assessed in terms of net total gas (CH(4) plus CO(2)) produced, expressed as a percentage of the theoretical production (ThGP). The compounds tested were selected from various chemical groups and included substituted phenols and benzoates, pesticides, phthalic acid esters, homocyclic and heterocyclic ring compounds, glycols, and monosubstituted benzenes. The results obtained were in good agreement with published surveys of biodegradability in U.S. digesting sludges and other methanogenic environments. In general, the presence of chloro or nitro groups inhibited anaerobic gas production, while carboxyl and hydroxyl groups facilitated biodegradation. The relationship between substituent position and susceptibility to methanogenic degradation was compound dependent. The following chemicals were completely degraded (>/=80% ThGP) at a concentration of 50 mg of carbon per liter: phenol, 2-aminophenol, 4-cresol, catechol, sodium benzoate, 4-aminobenzoic acid, 3-chlorobenzoic acid, phthalic acid, ethylene glycol, diethylene glycol, triethylene glycol, sodium stearate, and quinoline. 3-Cresol, 4-chlorobenzoic acid, dimethyl phthalate, and pyridine were partially degraded. Although the remaining chemicals tested were either persistent or toxic, their behavior may differ at more environmentally realistic chemical-to-biomass ratios. Our findings suggest that biodegradability assessments made with sludge from one source can be extrapolated to sludge from another source with a reasonable degree of confidence and should help in predicting the fate of an organic chemical during the anaerobic digestion of sewage sludge. PMID:16347851
Battersby, N S; Wilson, V
Thermophilic anaerobic digestion of sewage sludge with high solids content.
The treatment performance of thermophilic anaerobic digestion (AD) of sewage sludge with high solids content was investigated with two laboratory-scale thermophilic anaerobic reactors (R1 and R2) with a feeding of pre-centrifuged sewage sludge. Reactor R1 was fed with sludge of 3.7% total solids (TS). The volatile solids (VS) removal ratio and methane yield in the stable state were 54.9% and 0.29 NL CH(4)/g VS(added), respectively. For reactor R2, when the TS content of fed sludge was 7.4%, the VS removal ratio and methane yield in the stable state were 73.2% and 0.38 NL CH(4)/g VS(added), respectively. When the TS content was increased to 9.5%, the VS removal ratio and methane yield slightly decreased to 69.3% and 0.32 NL CH(4)/g VS(added), respectively, but the reactor was stably operated. An increase of ammonia concentration was observed, but it was in the safe range without severe inhibition on the methane production. The result indicated that thermophilic AD could support sewage sludge with high TS content (9.5%) without abrupt deterioration of the treatment performance. The high-solids AD process is an economical method for centralized sewage sludge treatment with lower transport cost. PMID:24804672
Wang, Feng; Hidaka, Taira; Uchida, Tsutomu; Tsumori, Jun
Pretreatment technologies for advancing anaerobic digestion of pulp and paper biotreatment residues.
While anaerobic digestion is commonly practiced in the municipal sector, it has not gained popularity in the pulp and paper industry mainly because of its long sludge residence time requirement of 20-30 days. The construction of large digesters to provide such extended residence times is capital-intensive and thus the implementation of anaerobic digestion has remained economically prohibitive. A review of the literature suggests that recent developments in sludge preconditioning technologies have substantially reduced the sludge residence time requirement to the order of 7 days. Also, the preconditioned sludges have been reported to hold potential for higher methane recovery with reduced excess sludge production requiring disposal. Such advantages, coupled with escalating fuel prices and the introduction of carbon credits under the Kyoto Accord, have significantly improved the economics of anaerobic digestion. As the cost of sludge management varies from one mill to another, mill-specific economic assessment of anaerobic digestion could identify cost-saving opportunities. PMID:17628630
Elliott, Allan; Mahmood, Talat
Model assisted startup of anaerobic digesters fed with thermally hydrolysed activated sludge.
This paper presents the use of the IWA ADM1 to predict and interpret results from two full-scale anaerobic digesters fed with thermal hyrolysate (waste activated sludge with a long upstream sludge age) from a Cambi hydrolysis process operating at 165�C and 6 bar-g. The first digester was fed conventionally-though intermittently, while the second was heavily diluted through a substantial component of the evaluation period (110 days). There were a number of important outcomes-related to both model application, and model predictions. Input and inert COD: mass ratio was very important, and was considerably higher than the 1.42 g g?� used for biomass throughout the IWA activated sludge and anaerobic digestion models. Input COD: VS ratio was 1.6 g g?�, and inert COD: VS ratio was 1.7 g g?�. The model succeeded on a number of levels, including effective prediction of important outputs (degradability, gas flow and composition, and final solids), clarification of the substantial data scatter, prediction of recovery times during operationally poor periods, and cross-validation of the results between digester 1 and digester 2. Key failures in model performance were related to an early incorrect assumption of the COD: VS ratio of 1.42 g g?�, and intermittent high acetate levels, most likely caused by inhibition, and rapid acclimatisation to ammonia. The acute free ammonia limit was found to be 0.008 M NH(3)-N, while the chronic inhibition constant (K(I,NH?,ac)) was 0.007 � 0.001 M NH?-N. Overall, this is a complex system, and application of the model added significant confidence to the initial operational decisions during an aggressive startup on an atypical feed. PMID:20935385
Batstone, D J; Balthes, C; Barr, K
Modeling temperature variations in a pilot plant thermophilic anaerobic digester.
A model that predicts temperature changes in a pilot plant thermophilic anaerobic digester was developed based on fundamental thermodynamic laws. The methodology utilized two simulation strategies. In the first, model equations were solved through a searching routine based on a minimal square optimization criterion, from which the overall heat transfer coefficient values, for both biodigester and heat exchanger, were determined. In the second, the simulation was performed with variable values of these overall coefficients. The prediction with both strategies allowed reproducing experimental data within 5% of the temperature span permitted in the equipment by the system control, which validated the model. The temperature variation was affected by the heterogeneity of the feeding and extraction processes, by the heterogeneity of the digestate recirculation through the heating system and by the lack of a perfect mixing inside the biodigester tank. The use of variable overall heat transfer coefficients improved the temperature change prediction and reduced the effect of a non-ideal performance of the pilot plant modeled. PMID:21120536
Valle-Guadarrama, Salvador; Espinosa-Solares, Teodoro; L�pez-Cruz, Irineo L; Domaschko, Max
CFD simulation of mixing for high-solids anaerobic digestion.
A computational fluid dynamics (CFD) model that simulates mechanical mixing for high-solids anaerobic digestion was developed. Numerical simulations of mixing manure slurry which exhibits non-Newtonian pseudo-plastic fluid behavior were performed for six designs: (i) one helical ribbon impeller; (ii) one anchor impeller; (iii) one curtain-type impeller; (iv) three counterflow (CF-2) impellers; (v) two modified high solidity (MHS 3/39�) impellers; and (vi) two pitched blade turbine impellers. The CFD model was validated against measurements for mixing a Herschel-Bulkley fluid by ribbon and anchor impellers. Based on mixing time with respect to mixing energy level, three impeller types (ribbon, CF-2, and MHS 3/39�) stand out when agitating highly viscous fluids, of these mixing with two MHS 3/39� impellers requires the lowest power input to homogenize the manure slurry. A comparison of digestion material demonstrates that the mixing energy varies with manure type and total solids concentration to obtain a given mixing time. Moreover, an in-depth discussion about the CFD strategy, the influences of flow regime and impeller type on mixing characteristics, and the intrinsic relation between mixing and flow field is included. PMID:22422446
Efficiency of the anaerobic digestion of amine wastes.
Laboratory-scale anaerobic degradation of monoethanolamine waste (MEAw) with co-substrate organics was conducted at room temperature and organic loading rates from 0.19 to 5.03 kg COD/m(3) day for 486 days in a hybrid digester. 90 % feed COD conversion to methane was obtained at the lower loads and only 45 % at the highest MEA waste/COD ratio (MEAwr) of 0.62 due to inhibition of methanogenesis. Inhibition at comparable loads decreased with time, implying that the culture adapted to the challenging feed. Methane yield was negatively correlated to MEAwr applied and inhibition avoided at MEAwr <0.5. Acetate accumulation implies inhibition of acetoclastic methanogenesis that can be caused by ammonia, a product of MEAw degradation. Moderate total ammonia nitrogen and free ammonia nitrogen accumulation, maximum 2.2 g N/l and 90 mg N/l, respectively suggests, however, that other components of MEAw, and/or degradation products of such, also inhibit methanogenesis, disturbing the digester performance. PMID:23912885
Wang, Shuai; Hovland, Jon; Bakke, Rune
Anaerobic digestion of autoclaved and untreated food waste.
Anaerobic digestion of autoclaved (160�C, 6.2 bar) and untreated source segregated food waste (FW) was compared over 473 days in semi-continuously fed mesophilic reactors with trace elements supplementation, at organic loading rates (OLRs) of 2, 3, 4 and 6 kg volatile solids(VS)/m(3)d. Methane yields at all OLR were 5-10% higher for untreated FW (maximum 0.483�0.013 m(3) CH4/kg VS at 3 kg VS/m(3) d) than autoclaved FW (maximum 0.439�0.020 m(3) CH4/kg VS at 4 kg VS/m(3) d). The residual methane potential of both digestates at all OLRs was less than 0.110 m(3) CH4/kg VS, indicating efficient methanation in all cases. Use of acclimated inoculum allowed very rapid increases in OLR. Reactors fed on autoclaved FW showed lower ammonium and hydrogen sulphide concentrations, probably due to reduced protein hydrolysis as a result of formation of Maillard compounds. In the current study this reduced biodegradability appears to outweigh any benefit due to thermal hydrolysis of ligno-cellulosic components. PMID:24238799
Tampio, Elina; Ervasti, Satu; Paavola, Teija; Heaven, Sonia; Banks, Charles; Rintala, Jukka
Anaerobic digestion of spent bedding from deep litter piggery housing.
This paper investigates spent litter from deep litter piggery housing as a potential substrate for farm-scale anaerobic digestion. Degradability and degradation rates were evaluated under mesophilic conditions for unused, lightly soiled (used by weaner/small pigs), and heavily soiled (used by finishing/large pigs) wheat straw, barley straw, and rice husks bedding. Apparent first order hydrolysis rate coefficients varied, but were comparable across all samples analysed (<0.1 day(-1)). Spent wheat straw was generally more degradable (approximately 60%) than spent barley straw, while spent barley straw was comparable to raw straw (40-50%), but with higher hydrolysis rates, indicating better accessibility. Rice husks were relatively poorly degradable (<20%), but degradability was improved by weathering in a pig shed. Digestion of spent barley and wheat straw litter was significantly faster (approximately twice the rate) at low (8% solids) than high (14% solids) solids loading. Rice husks degradation kinetics were not significantly influenced by solids concentration. Intrinsic methanogenic activity of heavily soiled spent wheat straw and rice husks bedding was initially poor, but achieved full activity after 40-60 days, indicating that reactor operation without external inoculum may be possible with care. PMID:19097776
Tait, Stephan; Tamis, Jelmer; Edgerton, Bruce; Batstone, Damien J
Kinetics and advanced digester design for anaerobic digestion of water hyacinth and primary sludge
A research program centered around a facility located at Walt Disney World (WDW) is in progress to evaluate the use of water hyacinth (WH) for secondary and tertiary wastewater treatment, to optimize growth of WH under these conditions, and to convert the resultant primary sludge (PS) and WH to methane via anaerobic digestion. This article describes the status of the biogasification component of this program, which includes baseline and advanced digestion experiments with individual feeds and blends and the design of an experimental test unit (ETU) to be installed at WDW. Experiments with several blends demonstrated that methane yields can be predicted from the fractional content and methane yield of each component. The process was found to adhere to the Monod kinetic model for microbial growth, and associated kinetic parameters were developed for various feed combinations. A novel upflow digester is achieving significantly higher conversion than a stirred-tank digester. Of several pretreatment techniques used, only alkaline treatment resulted in increased biodegradability. A larger scale (4.5 m/sup 3/) experimental test unit is being designed for installation at WDW in 1982. 13 figures, 4 tables.
Chynoweth, D.P.; Dolenc, D.A.; Ghosh, S.; Henry, M.P.; Jerger, D.E.; Srivastava, V.J.
On-farm anaerobic digester and fuel-alcohol plant. Final report
An anaerobic-digestion system, coupled with a fuel-alcohol plant, was constructed and set up on a southern Illinois farm as part of an integrated farm-energy system. The digester heating can be done using waste hot water from the alcohol plant and biogas from the digester can be used as fuel for the alcohol production. The anaerobic digestion system is made up of the following components; a hog finishing house with a manure pit; a solids handling pump to feed the manure; and a 13,000-gallon railroad tank car as the main digester vessel and pump to transfer effluent from the digester to a 150,000 gallon storage tank. The digester was operated for sufficient time to demonstrate the use of hot water in an automated digester temperature control system. Sufficient biogas was produced to demonstrate the use of biogas in a converted propane boiler.
Bengtson, H.H.
Anaerobic co-digestion of poultry blood with OFMSW: FTIR and TG-DTG study of process stabilization.
The potential of anaerobic digestion for the treatment of poultry blood has been evaluated in a co-digestion process. The organic fraction of municipal solid waste (OFMSW) was employed as the co-substrate to avoid digestion inhibition by dilution of nitrogen content and improvement of biodegradability. A semi-continuous mesophilic anaerobic digester was studied with a hydraulic retention time (HRT) of 36 days and an organic loading (OLR1) of 1.5 kg VSS feed m(-3) d(-1). The normal operational conditions of the reactor were altered with the application of an OLR2 of 2.0 kg VSS feed m(-3) d(-1) for a short period causing an imbalance in the process. The reduction of the OLR to initial conditions allowed the recovery of the system. The digestion process reached a final specific gas production (SGP) and a methane yield of 0.33 and 0.20 m3 kg(-1) VSS feed, respectively, maintaining low total and free ammonia concentrations. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to gain an insight into transformations experimented by the organic matter at the end of the stabilization process. Furthermore, these analytical techniques were used for evaluating the transformations undergone by the nitrogen-rich protein components of blood after digestion. It was proved that a reduction in volatile content and aliphatic structures of biowastes along with an increase in the degree of aromaticity occurred during the digestion process. PMID:19603704
Cuetos, M J; Mor�n, A; Otero, M; G�mez, X
Pretreatment of sludge with microwaves for pathogen destruction and improved anaerobic digestion performance.
A new way of generating Class A sludge using microwaves was evaluated through a series of laboratory-scale experiments. Microwaves provide rapid and uniform heating throughout the material. Other benefits of microwave treatment include instant and accurate control and selective and concentrated heating on materials, such as sludge, that have a high dielectric loss factor. Sludge was irradiated with 2450-MHz microwaves, and fecal coliforms were counted. Fecal coliforms were not detected at 65 degrees C for primary sludge and anaerobic digester sludge and at 85 degrees C for waste activated sludge when sludge was irradiated with 2450-MHz microwaves. During the bench-scale anaerobic digester operation, the highest average log reduction of fecal coliforms was achieved by the anaerobic digester fed with microwave-pretreated sludge (> or = 2.66 log removal). The anaerobic digester fed with microwave-irradiated sludge was more efficient in inactivation of fecal coliforms than the other two digesters fed with raw sludge and externally heated sludge, respectively. It took more than three hydraulic retention times for a bench-scale mesophilic anaerobic digester to meet Class A sludge requirements after feeding microwave-irradiated sludge. Class A sludge can be produced consistently with a continuously fed mesophilic anaerobic digester if sludge is pretreated with microwaves to reach 65 degrees C. PMID:16553169
Hong, Seung M; Park, Jae K; Teeradej, N; Lee, Y O; Cho, Y K; Park, C H
Alternative Utilization of Processes for Anaerobic Digestion: Production of Combustible Liquids and Compound Chemicals.
The anaerobic digestion process can be utilized for the production of alternative compounds to biogas. Acidogenic fermentation can convert with high yields complex biomass feedstocks into a mixture of organic acids, which, after separation from the fermen...
G. Di Giorgio M. Gamboni A. R. Sprocati
The Effects of Alum Sludge on Primary Sedimentation and Anaerobic Digestion.
A study investigating the feasibility of disposing alum sludge to sanitary sewers is reported. Since primary clarification and anaerobic digestion are the two sewage treatment processes most likely to be affected by alum sludge disposal, their physical an...
B. A. Rindt
Application of Kaolin for Control of Heavy Metals in Anaerobic Sludge Digestion.
Six laboratory-scale anaerobic digesters were used to evaluate the potential of kaolin addition for the control of heavy metal toxicity. Adsorption isotherms were obtained for the kaolin-metal system in solutions of the individual metals, nickel, copper, ...
W. H. Cross P. M. Rossello
In raw sludges and in mesophilically and thermophilically digested anaerobic sludges, large variations in numbers of viruses occurred over narrow ranges of numbers of fecal coliforms, total coliforms, and fecal streptococci, demonstrating that the bacteria are poor quantitative r...
High Solids Anaerobic Digestion (HSAD) Feasibility Assessment for the Municipality of Ajka in Hungary. Volume 1.
The report, prepared by Alpha-Gamma Technologies, Inc. and AP International Finance Corporation, examines the feasibility of a high solids anaerobic digestion system as a means of solid waste eco-processing. The study examines increasing the available was...
High Solids Anaerobic Digestion (HSAD) Feasibility Assessment for the Municipality of Ajka in Hungary. Volume 2.
Techno-economic evaluation of stillage treatment with anaerobic digestion in a softwood-to-ethanol process
Background Replacing the energy-intensive evaporation of stillage by anaerobic digestion is one way of decreasing the energy demand of the lignocellulosic biomass to the ethanol process. The biogas can be upgraded and sold as transportation fuel, injected directly into the gas grid or be incinerated on-site for combined heat and power generation. A techno-economic evaluation of the spruce-to-ethanol process, based on SO2-catalysed steam pretreatment followed by simultaneous saccharification and fermentation, has been performed using the commercial flow-sheeting program Aspen Plus�. Various process configurations of anaerobic digestion of the stillage, with different combinations of co-products, have been evaluated in terms of energy efficiency and ethanol production cost versus the reference case of evaporation. Results Anaerobic digestion of the stillage showed a significantly higher overall energy efficiency (87-92%), based on the lower heating values, than the reference case (81%). Although the amount of ethanol produced was the same in all scenarios, the production cost varied between 4.00 and 5.27 Swedish kronor per litre (0.38-0.50 euro/L), including the reference case. Conclusions Higher energy efficiency options did not necessarily result in lower ethanol production costs. Anaerobic digestion of the stillage with biogas upgrading was demonstrated to be a favourable option for both energy efficiency and ethanol production cost. The difference in the production cost of ethanol between using the whole stillage or only the liquid fraction in anaerobic digestion was negligible for the combination of co-products including upgraded biogas, electricity and district heat.
Biodegradability of wastewater and activated sludge organics in anaerobic digestion.
The investigation provides experimental evidence that the unbiodegradable particulate organics fractions of primary sludge and waste activated sludge calculated from activated sludge models remain essentially unbiodegradable in anaerobic digestion. This was tested by feeding the waste activated sludge (WAS) from three different laboratory activated sludge (AS) systems to three separate anaerobic digesters (AD). Two of the AS systems were Modified Ludzack - Ettinger (MLE) nitrification-denitrification (ND) systems and the third was a membrane University of Cape Town (UCT) ND and enhanced biological P removal system. One of the MLE systems and the UCT system were fed the same real settled wastewater. The other MLE system was fed raw wastewater which was made by adding a measured constant flux (gCOD/d) of macerated primary sludge (PS) to the real settled wastewater. This PS was also fed to a fourth AD and a blend of PS and WAS from settled wastewater MLE system was fed to a fifth AD. The five ADs were each operated at five different sludge ages (10-60d). From the measured performance results of the AS systems, the unbiodegradable particulate organic (UPO) COD fractions of the raw and settled wastewaters, the PS and the WAS from the three AS systems were calculated with AS models. These AS model based UPO fractions of the PS and WAS were compared with the UPO fractions calculated from the performance results of the ADs fed these sludges. For the PS, the UPO fraction calculated from the AS and AD models matched closely, i.e. 0.30 and 0.31. Provided the UPO of heterotrophic (OHO, fE_OHO) and phosphorus accumulating (PAO, fE_PAO) biomass were accepted to be those associated with the death regeneration model of organism "decay", the UPO of the WAS calculated from the AS and AD models also matched well - if the steady state AS model fE_OHO�=�0.20 and fE_PAO�=�0.25 values were used, then the UPO fraction of the WAS calculated from the AS models deviated significantly from those calculated with the AD models. Therefore in plant wide wastewater treatment models the characterization of PS and WAS as defined by the AS models can be applied without modification in AD models. The observed rate limiting hydrolysis/acidogenesis rates of the sludges are listed. PMID:24699419
Ikumi, D S; Harding, T H; Ekama, G A
Improvement of activated sludge stabilisation and filterability during anaerobic digestion by fruit and vegetable waste addition
Anaerobic co-digestion of fruit and vegetable waste (FVW) and activated sludge (AS) was investigated using anaerobic sequencing batch reactors (ASBRs). The effects of AS:FVW ratio and the organic loading rate (OLR) on digesters performances were examined. The mixtures having AS:FVW ratios of 100:00, 65:35, 35:65, by a total solid (TS) basis were operated at an hydraulic retention time (HRT) of
Lahdheb Habiba; Bouallagui Hassib; Hamdi Moktar
Biogas plasticization coupled anaerobic digestion: continuous flow anaerobic pump test results.
In this investigation, the Anaerobic Pump (TAP) and a conventional continuous flow stirred tank reactor (CFSTR) were tested side by side to compare performance. TAP integrates anaerobic digestion (AD) with biogas plasticization-disruption cycle to improve mass conversion to methane. Both prototypes were fed a "real world" 50:50 mixture of waste-activated sludge (WAS) and primary sludge and operated at room temperature (20 degrees Celsius). The quantitative results from three steady states show TAP peaked at 97% conversion of the particulate COD in a system hydraulic residence time (HRT) of only 6 days. It achieved a methane production of 0.32 STP cubic meter CH(4) per kilogram COD fed and specific methane yield of 0.78 m(3) CH(4) per cubic meter per day. This was more than three times the CFSTR specific methane yield (0.22 m(3) CH(4) per cubic meter per day) and more than double the CFSTR methane production (0.15 m(3) CH(4) per kilogram COD fed). A comparative kinetics analysis showed the TAP peak substrate COD removal rate (R (o)) was 2.24 kg COD per cubic meter per day, more than three times the CFSTR substrate removal rate of 0.67 kg COD per cubic meter per day. The three important factors contributing to the superior TAP performance were (1) effective solids capture (96%) with (2) mass recycle and (3) stage II plasticization-disruption during active AD. The Anaerobic Pump (TAP) is a high rate, high efficiency-low temperature microbial energy engine that could be used to improve renewable energy yields from classic AD waste substrates like refuse-derived fuels, treatment plant sludges, food wastes, livestock residues, green wastes and crop residuals. PMID:19455433
Schimel, Keith A; Boone, David R
Supercritical Fluid Extraction of Bacterial and Archaeal Lipid Biomarkers from Anaerobically Digested Sludge
Supercritical fluid extraction (SFE) was used in the analysis of bacterial respiratory quinone (RQ), bacterial phospholipid fatty acid (PLFA), and archaeal phospholipid ether lipid (PLEL) from anaerobically digested sludge. Bacterial RQ were determined using ultra performance liquid chromatography (UPLC). Determination of bacterial PLFA and archaeal PLEL was simultaneously performed using gas chromatography-mass spectrometry (GC-MS). The effects of pressure, temperature, and modifier concentration on the total amounts of RQ, PLFA, and PLEL were investigated by 23 experiments with five settings chosen for each variable. The optimal extraction conditions that were obtained through a multiple-response optimization included a pressure of 23.6 MPa, temperature of 77.6 �C, and 10.6% (v/v) of methanol as the modifier. Thirty nine components of microbial lipid biomarkers were identified in the anaerobically digested sludge. Overall, the SFE method proved to be more effective, rapid, and quantitative for simultaneously extracting bacterial and archaeal lipid biomarkers, compared to conventional organic solvent extraction. This work shows the potential application of SFE as a routine method for the comprehensive analysis of microbial community structures in environmental assessments using the lipid biomarkers profile.
Hanif, Muhammad; Atsuta, Yoichi; Fujie, Koichi; Daimon, Hiroyuki
Extension of the anaerobic digestion model No. 1 (ADM1) to include phenolic compounds biodegradation processes for the simulation of anaerobic co-digestion of olive mill wastes at thermophilic temperature.
This paper describes for the first time the extension of the anaerobic digestion model No. 1 (ADM1) to handle and simulate the anaerobic degradation processes of phenol compounds and homologues in olive mill wastewater (OMW) and olive mill solid waste (OMSW) at thermophilic temperature (55 degrees C). The general structure of the ADM1 was not changed except for the modifications related to the inclusion of phenolic compounds degradation processes into acetate and further into methane and CO(2). The effect of soluble phenolic compounds upon pH was taken into account in the pH simulation equations. The inhibitory effect of phenolic compounds on the fermenting process and methanogenic sub-populations was accounted for by the use of non-competitive inhibition functions. The most sensitive and new phenolic parameters were calibrated and validated using experimental data from our previous study dealing with the thermophilic anaerobic co-digestion of OMW with OMSW in semi-continuous tubular digesters. The simulation results indicated that the extended ADM1 was able to predict with reasonable accuracy effluent phenol concentrations and gas flow rates and effluent pH of various influent concentrations digested at hydraulic retention times (HRTs) of 36 and 24 days. PMID:18774218
Fezzani, Boubaker; Cheikh, Ridha Ben
An examination of the effects of detergents on anaerobic digestion.
An anaerobic filter was used to examine the treatability of wastewater formulated to simulate that from the manufacture of detergents. The detergent element was a mixture (1:1:1 v/v) of concentrated washing up liquid, a non-biological hand washing detergent and a fabric softener and, thus contained a combination of cationic surfactants, anionic surfactants, non-ionic surfactants and amphoteric surfactants. A concentration of 2 ml/l caused a deterioration in the performance of the digester which was pronounced after 7 days. When the packing of the filter was modified to include two layers of granular activated carbon, 320 g in total, the reactor was capable of treating a feed containing 10 ml/l. The amount of detergent removed during this second trial was greater than the Langmuir monolayer capacity of the carbon, indicating that both adsorption and degradation were occurring. The results also showed that, at detergent concentrations greater than 1 ml/l, the theoretical COD removal was lower than the actual COD removal. This was compatible with there being an element of adsorption by the activated carbon. PMID:12895555
Mensah, Kojo Arthur; Forster, Christopher F
Sensors network diagnosis in anaerobic digestion processes using evidence theory.
Instrumentation defines a sensors network on a process. Hardware sensors indeed allow one to get different information sources that can be often cross-checked to provide reliable data. However, each of these sources of information contains some uncertainties, either due to the hardware sensors' measurement principles, to their possible fouling, to the estimated parameters of the models used in software sensors and/or to the specific structures of the software sensors. This paper demonstrates that, in this context, the evidence theory is a very well suited formalism for fault detection and diagnosis. This theory indeed allows one to take into account the exact knowledge supported by each source of information and to combine them in order to detect the occurring faults. Moreover, this combination guarantees the best fault isolability from a practical point of view and is suitable for multiple faults occurring at the same time. Finally, the evidence theory is a highly modular formalism since new information sources can be very easily added and old ones can be removed. Validation is performed using real-life experiments from a 1 m3 anaerobic digestion fixed bed process used applied to the treatment of winery wastewaters. PMID:15685976
Steyer, J P; Lardon, L; Bernard, O
Ammonia volatilization from farm tanks containing anaerobically digested animal slurry
Ammonia (NH 3) volatilization from three full-scale tanks containing anaerobically digested animal slurry from one biogas plant was determined with a meteorological mass balance technique. No surface crust developed on the slurry. This provided an ideal system for analysing loss patterns from slurries without cover and to study the effect of a cover of straw and air-filled clay granules. Ammonia volatilization from uncovered slurry ranged from zero at subzero temperatures to 30 g N m -2 d -1 during summer. The high volatilization rate was attributed to a lack of surface cover, high slurry pH and high TAN (NH 3 + NH 4+) concentration. Ammonia volatilization from the covered slurry was insignificant. From the uncovered slurry the annual loss of NH3 was 3.3 kg N m -2 There was a significant effect of incident global radiation (ICR), air temperature at 20 cm (T_20) and rain on NH3 volatilization from the uncovered slurry. The straw covered slurry was significantly affected by T_20.
Sommer, S. G.
Anaerobic co-digestion of mechanically biologically treated municipal waste with primary sewage sludge � A feasibility study
This bench scale study investigated the suitability of MBT material for treatment by anaerobic digestion and the impacts of co-digestion of these wastes with sewage sludge. The results suggest that MBT material is amenable to anaerobic digestion with sewage sludge. The main problems for scale-up are related to the physical composition of the MBT material, the accumulation of heavy metals
Ole Pahl; Anna Firth; Iain MacLeod; Jim Baird
Mechanisms of floc destruction during anaerobic and aerobic digestion and the effect on conditioning and dewatering of biosolids
Laboratory anaerobic and aerobic digestion studies were conducted using waste activated sludges from two municipal wastewater treatment plants in order to gain insight into the mechanisms of floc destruction that account for changes in sludge conditioning and dewatering properties when sludges undergo anaerobic and aerobic digestion. Batch digestion studies were conducted at 20�C and the dewatering properties, solution biopolymer concentration
John T. Novak; Mary E. Sadler; Sudhir N. Murthy
Anaerobic digestibility of marine microalgae Phaeodactylum tricornutum in a lab-scale anaerobic membrane bioreactor.
The biomass of industrially grown Phaeodactylum tricornutum was subjected in a novel way to bio-methanation at 33�C, i.e., in an anaerobic membrane bioreactor (AnMBR) at a hydraulic retention time of 2.5 days, at solid retention times of 20 to 10 days and at loading rates in the range of 2.6-5.9 g biomass-COD L(-1) day(-1) with membrane fluxes ranging from 1 to 0.8 L m(-2) h(-1). The total COD recovered as biogas was in the order of 52%. The input suspension was converted to a clear effluent rich in total ammonium nitrogen (546 mg TAN L(-1)) and phosphate (141 mg PO(4)-P L(-1)) usable as liquid fertilizer. The microbial community richness, dynamics, and organization in the reactor were interpreted using the microbial resource management approach. The AnMBR communities were found to be moderate in species richness and low in dynamics and community organization relative to UASB and conventional CSTR sludges. Quantitative polymerase chain reaction analysis revealed that Methanosaeta sp. was the dominant acetoclastic methanogen species followed by Methanosarcina sp. This work demonstrated that the use of AnMBR for the digestion of algal biomass is possible. The fact that some 50% of the organic matter is not liquefied means that the algal particulates in the digestate constitute a considerable fraction which should be valorized properly, for instance as slow release organic fertilizer. Overall, 1 kg of algae dry matter (DM) could be valorized in the form of biogas ( euro 2.07), N and P in the effluent (euro 0.02) and N and P in the digestate (euro 0.04), thus totaling about euro 2.13 per kilogram algae DM. PMID:22005739
Zamalloa, Carlos; De Vrieze, Jo; Boon, Nico; Verstraete, Willy
A technological and socioeconomic assessment of anaerobic digester feasibility for small to mid-size livestock operations was undertaken. Three full scale digesters and one pilot scale facility were under various degrees of monitoring and evaluation to assess design and operation...
Biosynthesis of plant hormones during anaerobic digestion of instant coffee waste
A large amount of solid waste remains after the production of instant coffee. This waste has to be moved to dumps, where it poses a threat of environmental pollution. Treatment of this waste by anaerobic methanogenic thermophilic digestion produced, besides biogas, a digested slurry which was used as a growth medium for horticulture, and proved to be a suitable and
D. Kostenberg; U. Marchaim; A. A. Watad; E. Epstein
A study was conducted of the relative performance of anaerobic digestion systems under mesophilic and thermophilic conditions. Fifty liter laboratory scale digesters were fed primary sludge from the Allentown, PA Waste Water Treatment Plant. Long-term, steady-state performance da...
Pilot plant study of the effects of quebracho and wattle on anaerobic digestion
Quebracho and wattle tannin adversely affected the operational control required for the systems as well as CH4 production. The anaerobic organisms however degraded the tannins and the characteristic red color was effectively removed from the supernatant (liquid phase of digested sludge) during digestion.
Eye, J.D.; Ficker, C.F.
Economic analysis of anaerobic digestion�A case of Green power biogas plant in The Netherlands
One of the key concerns of biogas plants is the disposal of comparatively large amounts of digestates in an economically and environmentally sustainable manner. This paper analyses the economic performance of anaerobic digestion of a given biogas plant based on net present value (NPV) and internal rate of return (IRR) concepts. A scenario analysis is carried out based on a
Solomie A. Gebrezgabher; Miranda P. M. Meuwissen; Bram A. M. Prins
Anaerobic digestion of processed municipal solid waste using a novel high solids reactor: Maximum solids levels and mixing requirements
Summary Novel, laboratory-scale, high solids reactors operated under mesophilic conditions were used to study the anaerobic fermentation of processed municipal solid waste (MSW) to methane. The anaerobic digestion consortium was introduced to high solids levels through gradual adaptation. The maximum sludge solids level for stable anaerobic fermentation performance was identified as approximately 36% wt\\/wt. Recovery of the anaerobic consortium, following
Christopher J. Rivard; Michael E. Himmel; Todd B. Vinzant; William S. Adney; Charles E. Wyman; Karel Grohmann
The environmental sustainability of anaerobic digestion as a biomass valorization technology.
This paper studies the environmental sustainability of anaerobic digestion from three perspectives. First, reference electricity is compared to electricity production from domestic organic waste and energy crop digestion. Second, different digester feed possibilities in an agricultural context are studied. Third, the influence of applying digestate as fertilizer is investigated. Results highlight that biomass is converted at a rational exergy (energy) efficiency ranging from 15.3% (22.6) to 33.3% (36.0). From a life cycle perspective, a saving of over 90% resources is achieved in most categories when comparing biobased electricity to conventional electricity. However, operation without heat valorization results in 32% loss of this performance while using organic waste (domestic and agricultural residues) as feedstock avoids land resources. The use of digestate as a fertilizer is beneficial from a resource perspective, but causes increased nitrogen and methane emissions, which can be reduced by 50%, making anaerobic digestion an environmentally competitive bioenergy technology. PMID:22864176
De Meester, Steven; Demeyer, Jens; Velghe, Filip; Peene, Andy; Van Langenhove, Herman; Dewulf, Jo
Thermophilic anaerobic digestion of pulp and paper mill primary sludge and co-digestion of primary and secondary sludge.
Anaerobic digestion of pulp and paper mill primary sludge and co-digestion of primary and secondary sludge were studied for the first time in semi-continuously fed continuously stirred tank reactors (CSTR) in thermophilic conditions. Additionally, in batch experiments, methane potentials of 210 and 230 m�CH?/t volatile solids (VS)(added) were obtained for primary, and 50 and 100 m�CH?/tVS(added) for secondary sludge at 35 �C and 55 �C, respectively. Anaerobic digestion of primary sludge was shown to be feasible with organic loading rates (OLR) of 1-1.4 kgVS/m�d and hydraulic retention times (HRT) of 16-32 d resulting in methane yields of 190-240 m�CH?/tVS(fed). Also the highest tested OLR of 2 kgVS/m�d and the shortest HRT of 14-16 d could be feasible, if pH stability is confirmed. Co-digestion of primary and secondary sludge with an OLR of 1 kgVS/m�d and HRTs of 25-31 d resulted in methane yields of 150-170 m�CH?/tVS(fed). In the digestion processes, cellulose and hemicellulose degraded while lignin did not. pH adjustment and nitrogen deficiency needs to be considered when planning anaerobic digestion of pulp and paper mill wastewater sludges. PMID:22795957
Bayr, Suvi; Rintala, Jukka
Anaerobic digestion of Jatropha curcas L. press cake and effects of an iron-additive.
Oil production from Jatropha curcas L. seeds generates large amounts of Jatropha press cake (JPC) which can be utilized as a substrate for biogas production. The objective of this work was to investigate anaerobic mono-digestion of JPC and the effects of an iron additive (IA) on gas quality and process stability during the increase of the organic loading rate (OLR). With the increase of the OLR from 1.3 to 3.2 g(VS) L(-1) day(-1), the biogas yield in the reference reactor (RR) without IA decreased from 512 to 194 L(N) kg(VS) (-1) and the CH? concentration decreased from 69.3 to 44.4%. In the iron additive reactor (IAR), the biogas yield decreased from 530 to 462 L(N) kg(VS) (-1) and the CH? concentration decreased from 69.4 to 61.1%. The H?S concentration in the biogas was reduced by addition of the IA to values below 258 ppm in the IAR while H?S concentration in the RR increased and exceeded the detection limit of 5000 ppm. The acid capacity (AC) in the RR increased to more than 20 g L(-1), indicating an accumulation of organic acids caused by process instability. AC values in the IAR remained stable at values below 5 g L(-1). The results demonstrate that JPC can be used as sole substrate for anaerobic digestion up to an OLR of 2.4 g(VS) l(-1) day(-1). The addition of IA has effectively decreased the H(2)S content in the biogas and has improved the stability of the anaerobic process and the biogas quality. PMID:21987413
Schmidt, Thomas
Anaerobic co-digestion of dairy manure with mulched switchgrass for improvement of the methane yield
The owners of farm-scale anaerobic digesters are relying on off-farm wastes or energy crops as a co-digestion feedstock with\\u000a animal manure in order to increase their production of methane and thus revenues. Switchgrass represents an interesting feedstock\\u000a for Canadian digesters owners as it is a high-yielding low-maintenance perennial crop, well adapted to northern climate. Methane\\u000a potential assays in batch tests
Jean-Claude Frigon; Caroline Roy; Serge R. Guiot
Relationship between anaerobic digestion of biodegradable solid waste and spectral characteristics of the derived liquid digestate.
The evolution of spectral properties during anaerobic digestion (AD) of 29 types of biodegradable solid waste was investigated to determine if spectral characteristics could be used for assessment of biological stabilization during AD. Biochemical methane potential tests were conducted and spectral indicators (including the ratio of ultraviolet-visible absorbance at 254nm to dissolved organic carbon concentration (SUVA254), the ratio of ultraviolet-visible absorbance measured at 465nm and 665nm (E4/E6), and the abundance of fluorescence peaks) were measured at different AD phases. Inter-relationship between organic degradation and spectral indicators were analyzed by principle component analysis. The results shows that from methane production phase to the end of methane production phase, SUVA254 increased by 0.16-10.93 times, the abundance of fulvic acid-like compounds fluorescence peak increased by 0.01-0.54 times, the abundance of tyrosine fluorescence peak decreased by 0.03-0.64 times. Therefore, these indicators were useful to judge the course of mixed waste digestion. PMID:24686373
Zheng, Wei; L�, Fan; Phoungthong, Khamphe; He, Pinjing
Effect of anaerobic digestion on oocysts of the protozoan Eimeria tenella.
The effect of anaerobic digestion of poultry waste on oocysts of the protozoan Eimeria tenella, a common enteric pathogen that causes coccidiosis in poultry, was investigated in this study. Thermophilic (50 degrees C) and mesophilic (35 degrees C) anaerobic digestors, with poultry manure as the substrate, were inoculated with the oocysts. The oocysts were damaged during anaerobic digestion, as determined by morphological change and loss of their ability to sporulate. The recovered oocysts were tested for their infectivity in young chicks, as measured by body weight gain, mortality, and cecal lesions. Oocysts lost all their infectivity during thermophilic digestion, while oocysts subjected to mesophilic digestion remained moderately infective in comparison with untreated oocysts, which produced severe coccidiosis, high mortality, and low body weight gain in chicks. Oocysts were inactivated at 50 degrees C when they were suspended in digestor fluid or saline. Inactivation at 35 degrees C was significantly stronger in the digestor fluid than in the saline, which implied that factors other than temperature were involved in the lethal effect of anaerobic digestion on protozoan oocysts. In this study we demonstrated that the treatment of animal waste by anaerobic digestion, especially at a thermophilic temperature, has the benefits of pathogen control and protection of human and animal health in a farm environment. Images
Lee, M R; Shih, J C
Evaluation of a microwave-heating anaerobic digester treating municipal secondary sludge.
This work experimentally determined the effect of microwave irradiation on the anaerobic digestion of municipal secondary sludge in semi-continuous mesophilic digesters at hydraulic retention times (HRT) of 15, 10 and 5 days when microwaves were used as a heating source. A microwave-heating anaerobic digester (MHAD) was compared with a water-heating reactor (control). Biogas production increased in both digesters as the HRT decreased except for the control with a HRT of 5 days. Improvement in removal efficiency of volatile solid and biogas production of the MHAD relative to the control increased as the HRT decreased. The results show that the MHAD was more effective than the control in increasing mesophilic anaerobic biodegradability and biogas production treating secondary sludge. PMID:23837339
Jang, Joo-Hyun; Ahn, Johng-Hwa
[Effect of substrate concentration on pathogen indicators inactivation during thermophilic anaerobic digestion].
Because excess sludge contains high density of pathogens, it has to be treated to reduce pathogens before being disposed for land application. In this study, the effect of substrate concentration on pathogen inactivation during thermophilic anaerobic digestion was investigated. The results show that, with the increase of substrate concentration, VFAs and cumulative methane production increased. The density of total coliforms in the suspension liquid has a 2.0-3.0 orders of magnitude decline and fecal coliforms has 1.8-3.3 orders of magnitude decline after 28 days thermophilic anaerobic digestion at substrate concentration of 28-84 g x L(-1) and temperature of 55 degrees C. More than 99% of total coliforms and fecal coliforms have been killed after 28 days digestion. Salmonella spp. was not detected in the suspension and solid after anaerobic digestion. When substrate concentration was higher than 45 g x L(-1), the inactivation of total coliforms and fecal coliforms declined. PMID:24881391
Cao, Hong-Qing; Zhang, Fei-Fei; Li, Jian; Tong, Zi-Lin; Hu, Zhen-Hu
Effect of seasonal changes in quantities of biowaste on full scale anaerobic digester performance
A 750,000 l digester located in Roppen/Austria was studied over a 2-year period. The concentrations and amounts of CH{sub 4}, H{sub 2}, CO{sub 2} and H{sub 2}S and several other process parameters like temperature, retention time, dry weight and input of substrate were registered continuously. On a weekly scale the pH and the concentrations of NH{sub 4}{sup +}-N and volatile fatty acids (acetic, butyric, iso-butyric, propionic, valeric and iso-valeric acid) were measured. The data show a similar pattern of seasonal gas production over 2 years of monitoring. The consumption of VFA and not the hydrogenotrophic CH{sub 4} production appeared to be the limiting factor for the investigated digestion process. Whereas the changes in pH and the concentrations of most VFA did not correspond with changes in biogas production, the ratio of acetic to propionic acid and the concentration of H{sub 2} appeared to be useful indicators for reactor performance. However, the most influential factors for the anaerobic digestion process were the amount and the quality of input material, which distinctly changed throughout the year.
Illmer, P. [University of Innsbruck, Institute of Microbiology, Technikerstr. 25, A-6020 Innsbruck (Austria)], E-mail: email@example.com; Gstraunthaler, G. [Abfallbeseitigungsverband Westtirol, Breite Mure, A-6426 Roppen (Austria)
Process performance of anaerobic co-digestion of raw and acidified pig slurry.
The effect of incorporating different ratios of acidified pig slurry on methane yield was evaluated in two scales of anaerobic digesters: Thermophilic (50 �C) pilot scale digester (120 l), operating with an average hydraulic retention time of 20 days and thermophilic (52 �C) full-scale digesters (10 and 30 m(3)), operating with an average hydraulic retention time of 30 days. In the lab-scale digester, different inclusion levels of acidified slurry (0-60%) were tested each 15 days, to determine the maximum ratio of acidified to non-acidified slurry causing inhibition and to find process state indicators helping to prevent process failure. In the full-scale digesters, the level of inclusion of the acidified slurry was chosen from the ratio causing methane inhibition in the pilot scale experiment and was carried on in a long-term process of 100 days. The optimal inclusion level of acidified pig slurry in anaerobic co-digestion with conventional slurry was 10%, which promoted anaerobic methane yield by nearly 20%. Higher inclusion levels caused methane inhibition and volatile fatty acids accumulations in both experiments. In order to prevent process failure, the most important traits to monitor in the anaerobic digestion of acidified pig slurry were found to be: sulfate content of the slurry, alkalinity parameters (especially partial alkalinity and the ratio of alkalinity) and total volatile fatty acids (especially acetic and butyric acids). PMID:22884372
Moset, V; Cerisuelo, A; Sutaryo, S; M�ller, H B
Feasibility and interest of the anammox process as treatment alternative for anaerobic digester supernatants in manure processing--an overview.
Completely autotrophic nitrogen removal (ANR) is based on the combination of partial nitritation (PN) and anaerobic ammonium oxidation (anammox). It is a promising alternative for the subsequent treatment of biogas digester supernatants in livestock manure processing and nitrogen surplus scenarios. However, as no full-scale experiences in the treatment of manure digestates by ANR have been published to date, future field studies addressing treatment of this kind of effluent would be of great interest. Some topics to be considered in these studies would be coupling anaerobic digestion and ANR, analysis of the factors that affect the process, comparing reactor configurations, microbial ecology, gas emissions, and achieving robust performance. This paper provides an overview of published studies on ANR. Specific issues related to the applicability of the process for treating manure digestates are discussed. The energy requirements of ANR are compared with those of other technological alternatives aimed at recovering nitrogen from digester supernatants. The results of the assessment were shown to depend on the composition of the supernatant. In this regard, the PN-anammox process was shown to be more competitive than other alternatives particularly at concentrations of up to 2�kg NH4(+)-N�m(-3). PMID:24161806
Magr�, Albert; B�line, Fabrice; Dabert, Patrick
Energy and CO2 balance of maize and grass as energy crops for anaerobic digestion.
Energy crops can be used to feed anaerobic digesters and produce renewable energy. However, sustainability of this option requires that it contributes to a net production of renewable energy and a net reduction of fossil CO2 emission. In this paper, the net balance of CO2 emission and renewable energy production is assessed for maize and grass energy crops produced in several agricultural systems relevant for Southern Belgium and surrounding areas. The calculated net energy yields are 8-25 (maize) and 7.4-15.5 (grass) MWh of renewable CH4 per MWh of fossil energy invested, depending on the agricultural option considered. After conversion to electricity, the specific CO2 emissions range from 31 to 104 kg(CO2)MWhelectricity(-1), depending on the case considered. This corresponds to a significant reduction in CO2 emissions compared to the current reference gas-steam turbine technology which produces 456 kg(CO2)MWhelectricity(-1). PMID:17574409
Gerin, Patrick A; Vliegen, Fran�ois; Jossart, Jean-Marc
Terminal Reactions in the Anaerobic Digestion of Animal Waste �
An anaerobic mesophilic digestor was operated using beef cattle waste (diluted to 5.75% volatile solids) as substrate; retention time was 10 days with daily batch feed. Volatile solids destruction was 36%. Daily gas production rate was 1.8 liters of gas (standard temperature and pressure) per liter of digestor contents (0.99 liters of CH4 per liter of digestor contents). Acetate turnover was measured, and it was calculated that 68% of the CH4 was derived from the methyl group of acetate. When the methanogenic substrates acetic acid or H2/CO2 were added to the digestor on a continuous basis, the microflora were able to adapt and convert them to terminal products while continuing to degrade animal waste to the same extent as without additions. The methanogenic substrates were added at a rate at least 1.5 times the microbial production rate which was measured in the absence of added substrates. Added acetate was converted directly to CH4 by acetoclastic methanogens; H2 addition greatly stimulated acetate production in the digestor. A method is described for the measurement of acetate turnover in batch-fed digestors.
Boone, David R.
Low-heat, mild alkaline pretreatment of switchgrass for anaerobic digestion.
This study examines the effectiveness of alkaline pretreatment under mild heat conditions (100�C or 212�F) on the anaerobic co-digestion of switchgrass. The effects of alkaline concentration, types of alkaline, heating time and rinsing were evaluated. In addition to batch studies, continuous-feed studies were performed in triplicate to identify potential digester operational problems caused by switchgrass co-digestion while accounting for uncertainty due to digester variability. Few studies have examined anaerobic digestion of switchgrass or the effects of mild heating to enhance alkaline pretreatment prior to biomass digestion. Results indicate that pretreatment can significantly enhance digestion of coarse-ground (? 0.78 cm particle size) switchgrass. Energy conversion efficiency as high as 63% was observed, and was comparable or superior to fine-grinding as a pretreatment method. The optimal NaOH concentration was found to be 5.5% (wt/wt alkaline/biomass) with a 91.7% moisture level. No evidence of operational problems such as solids build-up, poor mixing, or floating materials were observed. These results suggest the use of waste heat from a generator could reduce the concentration of alkaline required to adequately pretreat lignocellulosic feedstock prior to anaerobic digestion. PMID:24410687
Jin, Guang; Bierma, Tom; Walker, Paul M
Long-term anaerobic digestion of food waste stabilized by trace elements
Highlights: Black-Right-Pointing-Pointer Korean food waste was found to contain low level of trace elements. Black-Right-Pointing-Pointer Stable anaerobic digestion of food waste was achieved by adding trace elements. Black-Right-Pointing-Pointer Iron played an important role in anaerobic digestion of food waste. Black-Right-Pointing-Pointer Cobalt addition further enhanced the process performance in the presence of iron. - Abstract: The purpose of this study was to examine if long-term anaerobic digestion of food waste in a semi-continuous single-stage reactor could be stabilized by supplementing trace elements. Contrary to the failure of anaerobic digestion of food waste alone, stable anaerobic digestion of food waste was achieved for 368 days by supplementing trace elements. Under the conditions of OLR (organic loading rates) of 2.19-6.64 g VS (volatile solid)/L day and 20-30 days of HRT (hydraulic retention time), a high methane yield (352-450 mL CH{sub 4}/g VS{sub added}) was obtained, and no significant accumulation of volatile fatty acids was observed. The subsequent investigation on effects of individual trace elements (Co, Fe, Mo and Ni) showed that iron was essential for maintaining stable methane production. These results proved that the food waste used in this study was deficient in trace elements.
Zhang Lei, E-mail: firstname.lastname@example.com [Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024 (China); Jahng, Deokjin, E-mail: firstname.lastname@example.com [Department of Environmental Engineering and Biotechnology, Myongji University, San 38-2, Namdong, Cheoin-Gu, Yongin, Gyeonggi-Do 449-728 (Korea, Republic of)
Navigating wastewater energy recovery strategies: a life cycle comparison of anaerobic membrane bioreactor and conventional treatment systems with anaerobic digestion.
The objective of this study was to evaluate emerging anaerobic membrane bioreactor (AnMBR) technology in comparison with conventional wastewater energy recovery technologies. Wastewater treatment process modeling and systems analyses were combined to evaluate the conditions under which AnMBR may produce more net energy and have lower life cycle environmental emissions than high rate activated sludge with anaerobic digestion (HRAS+AD), conventional activated sludge with anaerobic digestion (CAS+AD), and an aerobic membrane bioreactor with anaerobic digestion (AeMBR+AD). For medium strength domestic wastewater treatment under baseline assumptions at 15 �C, AnMBR recovered 49% more energy as biogas than HRAS+AD, the most energy positive conventional technology considered, but had significantly higher energy demands and environmental emissions. Global warming impacts associated with AnMBR were largely due to emissions of effluent dissolved methane. For high strength domestic wastewater treatment, AnMBR recovered 15% more net energy than HRAS+AD, and the environmental emissions gap between the two systems was reduced. Future developments of AnMBR technology in low energy fouling control, increased flux, and management of effluent methane emissions would make AnMBR competitive with HRAS+AD. Rapid advancements in AnMBR technology must continue to achieve its full economic and environmental potential as an energy recovery strategy for domestic wastewater. PMID:24742289
Smith, Adam L; Stadler, Lauren B; Cao, Ling; Love, Nancy G; Raskin, Lutgarde; Skerlos, Steven J
Two-stage anaerobic digestion of energy crops: methane production, nitrogen mineralisation and heavy metal mobilisation.
Energy crops (willow, sugar beet and grass silage) were digested in pilot scale two-stage anaerobic digesters. The specific methane yields obtained were 0.16, 0.38 and 0.39 m3 kg(-1) added volatile solids (VSadded) for willow, sugar beet and grass, respectively, corresponding to yearly gross energy yields of 15, 53 and 26 megawatt-hours (MWh) per hectare. With grass and sugar beets as substrate, 84-85% of the harvestable methane was obtained within 30 days. In pilot scale two-stage digestion of willow and sugar beet, 56 and 85% of the laboratory scale methane yields were obtained, but digestion of grass in two-stage reactors yielded 5% more methane than digestion in laboratory scale completely mixed low solids systems, possibly due to the pH conditions favourable to hydrolysis in the two-stage system. In digestion of grass and sugar beet the liquid at the end of digestion was rich in ammonium nitrogen, and the nitrogen in the substrate was efficiently mineralised. The results show that heavy metal concentrations are not likely to limit the utilisation of residues from digestion of nonmetal accumulating crops. Efficient mobilisation of heavy metals during the acidic phase of digestion revealed the possibility of removing metals from leachate generated in two-stage anaerobic digestion of phytoextracting crops. PMID:16506517
Lehtom�ki, A; Bj�rnsson, L
Combined anaerobic/aerobic digestion: effect of aerobic retention time on nitrogen and solids removal.
A combined anaerobic/aerobic sludge digestion system was studied to determine the effect of aerobic solids retention time (SRT) on its solids and nitrogen removal efficiencies. After the anaerobic digester reached steady state, effluent from the anaerobic digester was fed to aerobic digesters that were operated at 2- to 5-day SRTs. The anaerobic system was fed with a mixture of primary and secondary sludge from a local municipal wastewater treatment plant. Both systems were fed once per a day. The aerobic reactor was continuously aerated with ambient air, maintaining dissolved oxygen level at 1.1 +/- 0.3 mg/L. At a 4-day or longer SRT, more than 11% additional volatile solids and 90% or greater ammonia were removed in the aerobic digester, while 32.8 mg-N/L or more nitrite/nitrate also was measured. Most total Kjeldahl nitrogen removal was via ammonia removal, while little organic nitrogen was removed in the aerobic digester. PMID:22073727
Kim, Jongmin; Novak, John T
Treatment of municipal landfill leachate using a combined anaerobic digester and activated sludge system
The main objective of this study was to assess the feasibility of treating sanitary landfill leachate using a combined anaerobic and activated sludge system. A high-strength leachate from Shiraz municipal landfill site was treated using this system. A two-stage laboratory-scale anaerobic digester under mesophilic conditions and an activated sludge unit were used. Landfill leachate composition and characteristics varied considerably during 8 months experiment (COD concentrations of 48,552-62,150 mg/L). It was found that the system could reduce the COD of the leachate by 94% at a loading rate of 2.25 g COD/L/d and 93% at loading rate of 3.37 g COD/L/d. The anaerobic digester treatment was quite effective in removing Fe, Cu, Mn, and Ni. However, in the case of Zn, removal efficiency was about 50%. For the rest of the HMs the removal efficiencies were in the range 88.8-99.9%. Ammonia reduction did not occur in anaerobic digesters. Anaerobic reactors increased alkalinity about 3.2-4.8% in the 1st digester and 1.8-7.9% in the 2nd digester. In activated sludge unit, alkalinity and ammonia removal efficiency were 49-60% and 48.6-64.7%, respectively. Methane production rate was in the range of 0.02-0.04, 0.04-0.07, and 0.02-0.04 L/g COD{sub rem} for the 1st digester, the 2nd digester, and combination of both digesters, respectively; the methane content of the biogas varied between 60% and 63%.
Kheradmand, S. [Department of Civil and Environmental Engineering, University of Shiraz, Shiraz 7134851156 (Iran, Islamic Republic of); Karimi-Jashni, A., E-mail: email@example.com [Department of Civil and Environmental Engineering, University of Shiraz, Shiraz 7134851156 (Iran, Islamic Republic of); Sartaj, M. [Department of Civil Engineering, Isfahan University of Technology, Isfahan 841568311 (Iran, Islamic Republic of)
Comparative metagenomic analysis of bacterial populations in three full-scale mesophilic anaerobic manure digesters.
While the use of anaerobic digestion to generate methane as a source of bioenergy is increasing worldwide, our knowledge of the microbial communities that perform biomethanation is very limited. Using next-generation sequencing, bacterial population profiles were determined in three full-scale mesophilic anaerobic digesters operated on dairy farms in the state of Vermont (USA). To our knowledge, this is the first report of a metagenomic analysis on the bacterial population of anaerobic digesters using dairy manure as their main substrate. A total of 20,366 non-chimeric sequence reads, covering the V1-V2 hypervariable regions of the bacterial 16S rRNA gene, were assigned to 2,176 operational taxonomic units (OTUs) at a genetic distance cutoff value of 5 %. Based on their limited sequence identity to validly characterized species, the majority of OTUs identified in our study likely represented novel bacterial species. Using a na�ve Bayesian classifier, 1,624 anaerobic digester OTUs could be assigned to 16 bacterial phyla, while 552 OTUs could not be classified and may belong to novel bacterial taxonomic groups that have yet to be described. Firmicutes, Bacteroidetes, and Chloroflexi were the most highly represented bacteria overall, with Bacteroidetes and Chloroflexi showing the least and the most variation in abundance between digesters, respectively. All digesters shared 132 OTUs, which as a "core" group represented 65.4 to 70.6 % of sequences in individual digesters. Our results show that bacterial populations from microbial communities of anaerobic manure digesters can display high levels of diversity despite sharing a common core substrate. PMID:24085391
St-Pierre, Benoit; Wright, Andr�-Denis G
Inhibition of the anaerobic digestion process by linear alkylbenzene sulfonates
Linear Alkylbenzene Sulfonates (LAS) are the most widely used synthetic anionicsurfactants. They are anthropogenic, toxic compounds and are found in the primarysludge generated in municipal wastewater treatment plants. Primary sludge is usuallystabilized anaerobically and therefore it is important to investigate the effect of thesexenobiotic compounds on an anaerobic environment. The inhibitory effect of LinearAlkylbenzene Sulfonates (LAS) on the acetogenic and
Hariklia N. Gavala; Birgitte K. Ahring
Occurrence and reactivation of viable but non-culturable E. coli in sewage sludge after mesophilic and thermophilic anaerobic digestion.
The occurrence and reactivation of viable but non-culturable (VBNC) Escherichia coli after different anaerobic digestions and the subsequent dewatering and storage were evaluated and compared. Culturable E. coli in digested sludge increased by two to four orders of magnitudes immediately after dewatering. However, counts of both the total and viable E. coli indicated that the increase of E. coli was attributed to its reactivation from the VBNC state to the culturable state. The VBNC pathogen incidences of thermophilic digestion were two to three orders of magnitude higher than those of mesophilic digestion. Accordingly, culturable E. coli in thermophilic, digested sludge after storage were one order of magnitude higher than mesophilic digestion. Anaerobic digestion thus mainly alters the culturable state of pathogens rather than killing them; therefore the biological safety of digested sludge, especially temperature-phased anaerobic digestion, should be carefully assessed. PMID:24101245
Fu, Bo; Jiang, Qian; Liu, Hongbo; Liu, He
Should We Build "Obese" or "Lean" Anaerobic Digesters?
Conventional anaerobic digesters (ADs) treating dairy manure are fed with raw or fermented manure rich in volatile fatty acids (VFAs). In contrast, pre-fermented AD (PF-AD) is fed with the more recalcitrant, fiber-rich fraction of manure that has been pre-fermented and depleted of VFAs. Thus, the substrate of PF-AD may be likened to a lean diet rich in fibers while the pre-fermentation stage fermenter is fed a relatively rich diet containing labile organic substances. Previous results have shown that conventional and pre-fermented ADs fed with raw or pre-fermented manure, respectively, produced comparable methane yields. The primary objective of this study was to characterize, using next-generation DNA sequencing, the bacterial communities in various bioreactors (pre-fermentation stage fermenter; various operational arrangements PF-AD; conventional single-stage AD; and a full scale AD) and compare the Firmicutes to Bacteroidetes (F/B) ratios in these different systems. Firmicutes and Bacteroidetes constituted the two most abundant phyla in all AD samples analyzed, as well as most of the samples analyzed in the fermenters and manure samples. Higher relative abundance of Bacteroidetes, ranging from 26% to 51% of bacteria, tended to be associated with PF-AD samples, while the highest relative abundance of Firmicutes occurred in the fermenter (maximum of 76% of bacteria) and manure (maximum of 66% of bacteria) samples. On average, primary stage fermenters exhibited microbiological traits linked to obesity: higher F/B ratios and a �diet� that is less fibrous and more labile compared to that fed to PF-AD. On the other hand, microbial characteristics associated with leanness (lower F/B ratios combined with fibrous substrate) were associated with PF-AD. We propose that bacterial communities in AD shift depending on the quality of substrate, which ultimately results in maintaining VFA yields in PF-AD, similar to the role of bacterial communities and a high fiber diet in lean mice.
Briones, Aurelio; Coats, Erik; Brinkman, Cynthia
Bioavailability of Cu and Zn in raw and anaerobically digested pig slurry.
The impact of anaerobic digestion on the bioavailability of copper and zinc from pig slurry was assessed. Both chemical and biological approaches were used independently on raw slurry (RS) and anaerobically digested pig slurry (DS). This work, using ultracentrifugation pellets from the same pig slurry before and after an anaerobic treatment, confirmed that Cu and Zn behave differently in terms of bioavailability, and contrasting results were obtained by chemical and biological assessments. A chemical approach combined a preliminary study of the pH effect on particulate/dissolved metal partitioning, sequential extraction, and biochemical fractionation. This approach tended to show a lower mobility of metals from digested slurry (DS). A biological approach was carried out with Zea mays and Vicia faba to study Cu and Zn uptake in soil amended with RS or DS. This assay could not differentiate the two slurries. PMID:19200597
Marcato, Claire-Emmanuelle; Pinelli, Eric; Cecchi, Marie; Winterton, Peter; Guiresse, Maritxu
In situ volatile fatty acids influence biogas generation from kitchen wastes by anaerobic digestion.
Anaerobic digestion is considered to be an efficient way of disposing kitchen wastes, which can not only reduce waste amounts, but also produce biogas. However, the excessive accumulation of volatile fatty acids (VFA) caused by high organic loads will inhibit anaerobic digestion intensively. Effects of the VFA composition on biogas generation and microbial community are still required for the investigation under various organic loads of kitchen wastes. Our results showed that the maximum specific methane production was 328.3mlgTS(-1), and acetic acid was the main inhibitor in methanogenesis. With the increase of organic load, aceticlastic methanogenesis was more sensitive to acetic acid than hydrogenotrophic methanogenesis. Meanwhile, methanogenic microbial community changed significantly, and few species grew well under excessive organic loads. This study provides an attempt to reveal the mechanism of VFA inhibition in anaerobic digestion of kitchen wastes. PMID:24811447
Xu, Zhiyang; Zhao, Mingxing; Miao, Hengfeng; Huang, Zhenxing; Gao, Shumei; Ruan, Wenquan
Enhanced stabilization of digested sludge during long-term storage in anaerobic lagoons.
The goal of this work was to study changes in anaerobically stored digested sludge under different lengths of storage time to evaluate the quality of final product biosolids. The analyses of collected data suggest the organic matter degradation occurrence in the anaerobic environment of the lagoon approximately within the first year. After that, the degradation becomes very slow, which is likely caused by unfavorable environmental conditions. The performance of lagoon aging of digested sludge was also compared to the performance of lagoon aging of anaerobically digested and dewatered sludge. It was concluded that both of these processes result in biosolids of comparative quality and that the former provides more economical solution to biosolids handling by eliminating the need for mechanical dewatering. PMID:24851324
Lukicheva, Irina; Pagilla, Krishna; Tian, Guanglong; Cox, Albert; Granato, Thomas
Rapid start-up of thermophilic anaerobic digestion with the turf fraction of MSW as inoculum.
This study aims to determine suitable start-up conditions and inoculum sources for thermophilic anaerobic digestion. Within days of incubation MSW at 55�C, methane was produced at a high rate. In an attempt to narrow down which components of typical MSW contained the thermophilic methanogens, vacuum cleaner dust, banana peel, kitchen waste, and garden waste were tested as inoculum for thermophilic methanogenesis with acetate as the substrate. Results singled out grass turf as the key source of thermophilic acetate degrading methanogenic consortia. Within 4 days of anaerobic incubation (55�C), anaerobically incubated grass turf samples produced methane accompanied by acetate degradation enabling successful start-up of thermophilic anaerobic digestion. Other essential start-up conditions are specified. Stirring of the culture was not conducive for successful start-up as it resulted specifically in propionate accumulation. PMID:21723117
Suwannoppadol, Suwat; Ho, Goen; Cord-Ruwisch, Ralf
Influence of staging, mean cell residence time, and thermophilic temperature on the thermophilic anaerobic digestion process.
As Class B biosolids land application has become less acceptable to many local jurisdictions, low-cost processes to achieve Class A standards have become more popular. Prominent among these low-cost processes is thermophilic anaerobic digestion. As a result, thermophilic anaerobic digestion is now a popular topic in wastewater treatment literature, but quantifiable methods for selecting a particular thermophilic process have not been offered. To provide for this need, an empirical model was developed from data collected in thermophilic anaerobic digestion studies conducted using East Bay Municipal Utility District's (Oakland, California) primary and waste activated sludge to feed both bench- and full-scale digesters. The model predicts at which thermophilic temperature and mean cell residence time (MCRT) one process will outperform or equal another, with respect to fecal coliform reduction. The different disinfection efficiencies in the different thermophilic processes might be explained by the presence or absence of high volatile acid and/or un-ionized ammonia levels in the processes' digested sludges. Data from these studies also show an apparent relationship between increased thermophilic temperatures and volatile solids destruction, and between increased temperatures and specific volatile acids production, for digesters operating at a 13-day MCRT and higher, but not for digesters operating at a 2-day MCRT. PMID:16752611
Gray, Donald M D; Hake, John M; Ghosh, Sambhunath
Benefits of supplementing an industrial waste anaerobic digester with energy crops for increased biogas production.
Currently, there is increasing competition for waste as feedstock for the growing number of biogas plants. This has led to fluctuation in feedstock supply and biogas plants being operated below maximum capacity. The feasibility of supplementing a protein/lipid-rich industrial waste (pig manure, slaughterhouse waste, food processing and poultry waste) mesophilic anaerobic digester with carbohydrate-rich energy crops (hemp, maize and triticale) was therefore studied in laboratory scale batch and continuous stirred tank reactors (CSTR) with a view to scale-up to a commercial biogas process. Co-digesting industrial waste and crops led to significant improvement in methane yield per ton of feedstock and carbon-to-nitrogen ratio as compared to digestion of the industrial waste alone. Biogas production from crops in combination with industrial waste also avoids the need for micronutrients normally required in crop digestion. The batch co-digestion methane yields were used to predict co-digestion methane yield in full scale operation. This was done based on the ratio of methane yields observed for laboratory batch and CSTR experiments compared to full scale CSTR digestion of industrial waste. The economy of crop-based biogas production is limited under Swedish conditions; therefore, adding crops to existing industrial waste digestion could be a viable alternative to ensure a constant/reliable supply of feedstock to the anaerobic digester. PMID:21975301
Nges, Ivo Achu; Escobar, Federico; Fu, Xinmei; Bj�rnsson, Lovisa
Anaerobic digestion for simultaneous sewage sludge treatment and CO biomethanation: process performance and microbial ecology.
Syngas is produced by thermal gasification of both nonrenewable and renewable sources including biomass and coal, and it consists mainly of CO, CO2, and H2. In this paper we aim to bioconvert CO in the syngas to CH4. A novel technology for simultaneous sewage sludge treatment and CO biomethanation in an anaerobic reactor was presented. Batch experiments showed that CO was inhibitory to methanogens, but not to bacteria, at CO partial pressure between 0.25 and 1 atm under thermophilic conditions. During anaerobic digestion of sewage sludge supplemented with CO added through a hollow fiber membrane (HFM) module in continuous thermophilic reactors, CO did not inhibit the process even at a pressure as high as 1.58 atm inside the HFM, due to the low dissolved CO concentration in the liquid. Complete consumption of CO was achieved with CO gas retention time of 0.2 d. Results from high-throughput sequencing analysis showed clear differences of the microbial community structures between the samples from liquid and biofilm on the HFM in the reactor with CO addition. Species close to Methanosarcina barkeri and Methanothermobacter thermautotrophicus were the two main archaeal species involved in CO biomethanation. However, the two species were distributed differently in the liquid phase and in the biofilm. Although the carboxidotrophic activities test showed that CO was converted by both archaea and bacteria, the bacterial species responsible for CO conversion are unknown. PMID:23952148
Luo, Gang; Wang, Wen; Angelidaki, Irini
Biochemical methane potential and solid state anaerobic digestion of Korean food wastes
In order to develop an anaerobic digestion process for Korean food wastes containing 15�30% total solids (TS) the biochemical methane potentials (BMP) of their components and mixture (mixed food waste, MFW) were measured. The methane yields of cooked meat, cellulose (as control), boiled rice, fresh cabbage and MFW were 482, 356, 294, 277 and 472 ml CH4\\/gVS added and anaerobic
Ho Nam Chang; Soon Chul Park
A novel alternate feeding mode for semi-continuous anaerobic co-digestion of food waste with chicken manure.
A novel alternate feeding mode was introduced to study the possibilities of improving methane yield from anaerobic co-digestion of food waste (FW) with chicken manure (CM). Two kinds of feeding sequence (a day FW and next day CM (FM/CM), two days FM and the third day CM (FW/FM/CM)) were investigated in semi-continuous anaerobic digestion and lasted 225 days, and the mono-digestions of FW and CM were used as control group, respectively. The feeding sequence of FW/CM and mono-digestion of CM were observed to fail to produce gas at hydraulic retention time (HRT) of 70 days due to the ammonia inhibition, however, the mode of FW/FM/CM was proved to successfully run at HRT of 35 days with a higher OLR of 2.50 kg L(-1)d(-1) and obtain a higher methane production rate of 507.58 ml g(-1) VS and volumetric biogas production rate of 2.1 L L(-1)d(-1). PMID:24865323
Wang, Ming; Sun, Xianli; Li, Pengfei; Yin, Lili; Liu, Dan; Zhang, Yingwei; Li, Wenzhe; Zheng, Guoxiang
Performance of sequential anaerobic/aerobic digestion applied to municipal sewage sludge.
A promising alternative to conventional single phase processing, the use of sequential anaerobic-aerobic digestion, was extensively investigated on municipal sewage sludge from a full scale wastewater treatment plant. The objective of the work was to evaluate sequential digestion performance by testing the characteristics of the digested sludge in terms of volatile solids (VS), Chemical Oxygen Demand (COD) and nitrogen reduction, biogas production, dewaterability and the content of proteins and polysaccharides. VS removal efficiencies of 32% in the anaerobic phase and 17% in the aerobic one were obtained, and similar COD removal efficiencies (29% anaerobic and 21% aerobic) were also observed. The aerobic stage was also efficient in nitrogen removal providing a decrease of the nitrogen content in the supernatant attributable to nitrification and simultaneous denitrification. Moreover, in the aerobic phase an additional marked removal of proteins and polysaccharides produced in the anaerobic phase was achieved. The sludge dewaterability was evaluated by determining the Optimal Polymer Dose (OPD) and the Capillary Suction Time (CST) and a significant positive effect due to the aerobic stage was observed. Biogas production was close to the upper limit of the range of values reported in the literature in spite of the low anaerobic sludge retention time of 15 days. From a preliminary analysis it was found that the energy demand of the aerobic phase was significantly lower than the recovered energy in the anaerobic phase and the associated additional cost was negligible in comparison to the saving derived from the reduced amount of sludge to be disposed. PMID:21477916
Tomei, M Concetta; Rita, Sara; Mininni, Giuseppe
With the aim of the Phase I project to develop an innovative anaerobic co-digestion design for the treatment of dairy manure and poultry waste, our Phase I team has evaluated the technical and economic feasibility of the anaerobic co-digestion design concept with a thorough in...
Effect of ultrasonic pretreatment on anaerobic digestion and its sludge dewaterability.
To investigate the effect of ultrasonic pretreatment on anaerobic digestion and sludge dewaterability and further to probe into the influencing factors on sludge dewaterability, sludge flocs were stratified into four fractions: (1) slime; (2) loosely bound extracellular polymeric substances (LB-EPS); (3) tightly bound EPS (TB-EPS); and (4) EPS-free pellets. The results showed that ultrasonic pretreatment increased the anaerobic digestion efficiency by 7%-8%. Anaerobic digestion without ultrasonic pretreatment deteriorated the sludge dewaterability, with the capillary suction time (CST) increased from 1.42 to 47.3 (sec x L)/g-TSS. The application of ultrasonic pretreatment firstly deteriorated the sludge dewaterability (normalized CST increased to 44.4 (sec x L)/g-TSS), while subsequent anaerobic digestion offset this effect and ultimately decreased the normalized CST to 23.2 (sec x L)/g-TSS. The dewaterability of unsonicated sludge correlated with protein (p = 0.003) and polysaccharide (p = 0.004) concentrations in the slime fraction, while that of sonicated sludge correlated with protein concentrations in the slime and LB-EPS fractions (p < 0.05). Fluorescent excitation-emission matrix analysis showed that the fluorescence matters in the LB-EPS fraction significantly correlated with sludge dewaterability during anarobic digestion. PMID:22432282
Xu, Huacheng; He, Pinjing; Yu, Guanghui; Shao, Liming
Attribute based specification, comparison and selection of feed stock for anaerobic digestion using MADM approach.
Organic wastes are common in nature and generated at different sources which need to be treated before disposing into the environment. Anaerobic digestion (AD) process is a primary technique used for digestion and reduction of the ill effects of disposing the organic waste. Selection of appropriate feed stock for anaerobic digestion among the available options is a primary concern and the process efficiency and stability largely depend on this. The present paper describes a methodology for evaluation, comparison, ranking and optimum selection of a feed stock for anaerobic digestion. A 30 attribute coding scheme is proposed to evaluate the existing alternatives for feed stock of anaerobic digester. A three stage procedure which includes the elimination search is proposed to evaluate the available alternatives with the help of attributes quickly. Technique for order preference by similarity to ideal solution (TOPSIS) is a Multiple Attribute Decision Making (MADM) approach and graphical methods namely line graph and spider diagrams are used for optimum selection of feed stock among the available options. MATLAB code is written to execute the three stage procedure. The proposed methodology is explained through an illustrated example. PMID:21247688
Rao, P Venkateswara; Baral, Saroj S
Biodegradation of pulp and paper mill effluent using anaerobic followed by aerobic digestion.
An experimental study was carried to find out the degradability of black liquor of pulp and paper mill wastewater for biomethanogenesis in continuous stirred tank reactor (CSTR) and followed by activated sludge process (ASP). Continuous stirred tank reactor was used in present study for anaerobic digestion of black liquor, while completely mixed activated sludge system was used for aerobic digestion. A maximum methane production was found up to 430 ml/day, chemical oxygen demand was reduced up to 64% and total volatile fatty acid increased up to 1500 mg/l from 975 mg/l at 7.3 pH, 37 degrees C temperature and 8 days hydraulic retention time during anaerobic digestion. In activated sludge process (aerobic digestion) chemical oxygen demand and biological oxygen demand reduction were 81% and 86% respectively at 72 hr hydraulic retention time. PMID:17436533
Bishnoi, Narsi R; Khumukcham, R K; Kumar, Rajender
Experimental study on a coupled process of production and anaerobic digestion of Chlorella vulgaris.
The main goal of this present study is to investigate the feasibility of coupling algae production (Chlorella vulgaris) to an anaerobic digestion unit. An intermediate settling device was integrated in order to adapt the feed-flow concentration and the flow rate. Digestion of C. vulgaris was studied under 16 and 28 days hydraulic retention times (HRT), with a corresponding organic loading rate of 1g(COD)L(-1). Increasing the HRT achieved 51% COD removal with a methane production measured at 240 mL g(VSS)(-1). Performing different HRTs and dynamic monitoring during degradation highlighted differential hydrolysis of microalgae compartments. However, 50% of the biomass did not undergo anaerobic digestion, even under long retention times. This points out the interest for further studies on pre-treatment performances and more generally speaking on the need for intensifying microalgae biomass digestion. PMID:20678925
Ras, Monique; Lardon, Laurent; Bruno, Sialve; Bernet, Nicolas; Steyer, Jean-Philippe
Aluminum-Organic Interactions Influencing Anaerobic Digestion of Coagulated Substrates.
Results are presented of an investigation in which ten soluble organic substrates were coagulated with alum and then assayed for anaerobic biodegradability using a serum bottle technique. Compounds employed included lactic acid, acetic acid, butyric acid,...
R. L. Greco J. M. Coto S. K. Dentel J. M. Gossett
Microbial Ecology of Thermophilic Anaerobic Digestion: Progress Report, Year 4.
The goal of this project is to gain a more complete understanding of the microorganisms converting a lignocellulose waste to methane in a thermophilic (58/degree/C) anaerobic bioreactor. We have directly examined microbial populations in the bioreactor an...
S. H. Zinder
Microbial Ecology of Thermophilic Anaerobic Digestion: (Progress Report, Year 3).
Impact of nano zero valent iron (NZVI) on methanogenic activity and population dynamics in anaerobic digestion.
Nano zero valent iron (NZVI), although being increasingly used for environmental remediation, has potential negative impact on methanogenesis in anaerobic digestion. In this study, NZVI (average size = 55 � 11 nm) showed inhibition of methanogenesis due to its disruption of cell integrity. The inhibition was coincident with the fast hydrogen production and accumulation due to NZVI dissolution under anaerobic conditions. At the concentrations of 1 mM and above, NZVI reduced methane production by more than 20%. At the concentration of 30 mM, NZVI led to a significant increase in soluble COD (an indication of cell disruption) and volatile fatty acids in the mixed liquor along with an accumulation of H2, resulting in a reduction of methane production by 69% (�4% [standard deviation]). By adding a specific methanogenesis inhibitor-sodium 2-bromoethanesulfonate (BES) to the anaerobic sludge containing 30 mM NZVI, the amount of H2 produced was only 79% (�1%) of that with heat-killed sludge, indicating the occurrence of bacterially controlled hydrogen utilization processes. Quantitative PCR data was in accordance with the result of methanogenesis inhibition, as the level of methanogenic population (dominated by Methanosaeta) in the presence of 30 mM NZVI decreased significantly compared to that of the control. On the contrary, ZVI powder (average size <212 ?m) at the same concentration (30 mM) increased methane production presumably due to hydrogenotrophic methanogenesis of hydrogen gas that was slowly released from the NZVI powder. While it is a known fact that NZVI disrupts cell membranes, which inhibited methanogenesis described herein, the results suggest that the rapid hydrogen production due to NZVI dissolution also contribute to methanogenesis inhibition and lead to bacterially controlled hydrogenotrophic processes. PMID:24112628
Yang, Yu; Guo, Jialiang; Hu, Zhiqiang
Characterization of the methanogen community in a household anaerobic digester fed with swine manure in China.
Household anaerobic digesters have been installed across rural China for biogas production, but information on methanogen community structure in these small biogas units is sparsely available. By creating clone libraries for 16S rRNA and methyl coenzyme M reductase alpha subunit (mcrA) genes, we investigated the methanogenic consortia in a household biogas digester treating swine manure. Operational taxonomic units (OTUs) were defined by comparative sequence analysis, seven OTUs were identified in the 16S rRNA gene library, and ten OTUs were identified in the mcrA gene library. Both libraries were dominated by clones highly related to the type strain Methanocorpusculum labreanum Z, 64.0�% for 16S rRNA gene clones and 64.3�% for mcrA gene clones. Additionally, gas chromatography assays showed that formic acid was 84.54�% of the total volatile fatty acids and methane was 57.20�% of the biogas composition. Our results may help further isolation and characterization of methanogenic starter strains for industrial biogas production. PMID:23649353
Qin, Huibin; Lang, Huihua; Yang, Hongjiang
Anaerobic biodegradation of phenolic compounds in digested sludge
The authors examined the anaerobic degradation of phenol and the ortho, meta, and para isomers of chlorophenol, methoxyphenol, methylphenol (cresol),and nitrophenol in anaerobic sewage sludge diluted to 10% in a mineral salts medium. Of the 12 monosubstituted phenols studied, only p-chlorophenol and o-cresol were not significantly degraded during an 8-week incubation period. The phenol compounds degraded and the time required
S. A. Boyd; D. R. Shelton; D. Berry; J. M. Tiedje
Continuous thermal hydrolysis and anaerobic digestion of sludge. Energy integration study.
Experimental data obtained from the operation in a pilot plant are used to perform mass and energy balances to a global process combining units of thermal hydrolysis (TH) of secondary sludge, anaerobic digestion (AD) of hydrolysed secondary sludge together with fresh primary sludge, and cogeneration from biogas by using a gas engine in which the biogas produces electricity and heat from the exhaust gases. Three scenarios were compared, corresponding to the three digesters operated: C (conventional AD, 17 days residence time), B (combined TH + AD, same time), and A (TH + AD at half residence time). The biogas production of digesters B and A was 33 and 24% better, respectively when compared with C. In the case of the combined TH + AD process (scenarios A and B), the key factors in the energy balance were the recovery of heat from hot streams, and the concentration of sludge. The results of the balances showed that for 8% DS concentration of the secondary sludge tested in the pilot plant, the process can be energetically self-sufficient, but a fraction of the biogas must by-pass the gas engine to be directly burned. From an economic point of view, scenario B is more profitable in terms of green energy and higher waste removal, while scenario A reduces the digester volume required by a half. Considering a population of 100,000 inhabitants, the economic benefit is 87,600 �/yr for scenario A and 132,373 �/yr for B. This value can be increased to 223,867 �/yr by increasing the sludge concentration of the feeding to the TH unit to a minimum value that allows use of all the biogas to produce green energy. This concentration is 13% DS, which is still possible from a practical point of view. Additional benefits gained with the combined TH + AD process are the enhancement of the digesters rheology and the possibility of getting Class A biosolids. The integration study presented here set the basis for the scale-up to a demonstration plant. PMID:22546800
P�rez-Elvira, S I; Fdz-Polanco, F
Effect of inoculum sources on the anaerobic digestion of rice straw.
The aim of this study was to evaluate the effect of different inoculum sources on the rice straw anaerobic digestion. Six different digestates (DM, SM, CM, MS, AGS and PS) were applied as inoculums and their effects were evaluated in batch reactors. The results indicated that digested manures were more suitable than sludge. Reactors inoculated with digested manures achieved higher, biogas production and lignocellulose degradation. The better adaptability of digested manures had relationship with its higher cellulase and xylanase activities and sufficient nutrients content. DM had the best effect among all three digested manures. Reactors inoculated with DM achieved the highest biogas production (325.3 mL/g VS) and enzymes activities. The synergism between cellulase and xylanase activities played an important role in lignocellulose degradation. PMID:24589383
Gu, Yu; Chen, Xiaohua; Liu, Zhanguang; Zhou, Xuefei; Zhang, Yalei
Removal and recovery of nutrients as struvite from anaerobic digestion residues of poultry manure
The removal and the recovery of nutrients, namely nitrogen (N) and phosphorus (P) from anaerobically digested and solid�liquid separated manure effluents via struvite precipitation were investigated. Both the liquid and the solid phases of the poultry manure digester effluent were subjected to struvite precipitation experiments. The Mg:N:P molar ratio of 1:1:1 in the liquid phase resulted in an average NH4?N
Y. D. Yilmazel; G. N. Demirer
The effects of digestion temperature and temperature shock on the biogas yields from the mesophilic anaerobic digestion of swine manure.
In order to obtain basic design criteria for anaerobic digesters of swine manure, the effects of different digesting temperatures, temperature shocks and feed loads, on the biogas yields and methane content were evaluated. The digester temperatures were set at 25, 30 and 35 degrees C, with four feed loads of 5%, 10%, 20% and 40% (feed volume/digester volume). At a temperature of 30 degrees C, the methane yield was reduced by only 3% compared to 35 degrees C, while a 17.4% reduction was observed when the digestion was performed at 25 degrees C. Ultimate methane yields of 327, 389 and 403 mL CH(4)/g VS(added) were obtained at 25, 30 and 35 degrees C, respectively; with moderate feed loads from 5% to 20% (V/V). From the elemental analysis of swine manure, the theoretical biogas and methane yields at standard temperature and pressure were 1.12L biogas/g VS(destroyed) and 0.724 L CH(4)/g VS(destroyed), respectively. Also, the methane content increased with increasing digestion temperatures, but only to a small degree. Temperature shocks from 35 to 30 degrees C and again from 30 to 32 degrees C led to a decrease in the biogas production rate, but it rapidly resumed the value of the control reactor. In addition, no lasting damage was observed for the digestion performance, once it had recovered. PMID:17306978
Chae, K J; Jang, Am; Yim, S K; Kim, In S
Effective reduction of enteric bacteria and viruses during the anaerobic digestion of biomass and wastes
Natural resource depletion increases the amount of waste requiring efficient and affordable disposal alternatives. Through effective management, many of these so-called wastes can be utilized as important energy and agricultural resources. One such management approach involves the utilization of emergent aquatic plant species, such as water hyacinth, to remove nutrients from the wastewater during growth. This process produces an energy-containing biomass that can then be anaerobically digested either separately or with other waste components to produce energy-containing methane and an effluent residue containing significant quantities of protein and nutrients. This residue can be utilized as an effective fertilizer, soil conditioner, or animal feed supplement provided it is rendered reasonably safe from such contaminants as enteric microorganisms. This study was conducted to identify the digester operating parameters that affect the survival of enteric bacteria and viruses during the anaerobic digestion of blends of water hyacinth and primary sewage sludge. Solids retetion time and temperature were demonstrated to be important parameters affecting the survival of poliovirus, f-2 coliphage, Streptoccus fecalis, and Escherichia coli during anaerobic digestion. The die-off rates of the coliphages were similar to those of the poliovirus at 35/sup 0/C. S. fecalis appeared to be the most stable of any of the bacteria and viruses studied. All organisms were more stable at 25 than at 35/sup 0/C. The data demonstrate that the concentration of enteric bacteria and viruses can be effectively reduced during anaerobic digestion using techniques, such as increased solids retention times and mesophilic temperatures, that are consistent with achieving high methane yields. The survival of enteric viruses during anaerobic digestion may be affected by the characteristics of the feedstock as well as by the process operating conditions.
Fannin, K.F.; Hsu, P.H.; Mensinger, J.; Cahill, C.
Sewage sludge-to-energy approaches based on anaerobic digestion and pyrolysis: Brief overview and energy efficiency assessment
Energy recovery from sewage sludge offers an opportunity for sustainable management of sewage sludge and energy. Anaerobic digestion and pyrolysis are among the most promising processes applicable for sewage sludge-to-energy conversion. Anaerobic digestion of sewage sludge forms methane-rich biogas, which can be utilized as fuel to offset heat and electricity consumption of the wastewater treatment sector. However, the digestion process
Yucheng Cao
Test/QA Plan For Verification Of Anaerobic Digester For Energy Production And Pollution Prevention
The ETV-ESTE Program conducts third-party verification testing of commercially available technologies that improve the environmental conditions in the U.S. A stakeholder committee of buyers and users of such technologies guided the development of this test on anaerobic digesters...
Anaerobic digestion of semi-solid organic waste: biogas production and its purification
The main objective of the present experimental investigation was to evaluate the effects of using different bacteria inoculums at identical technical settings on the anaerobic digestion process for the treatment of semi-solid organic waste available from the orthofruit market. As a possible means to improve the biogas production, as well as reduce their pollution potential, the idea of using recycled
G. Lastella; C. Testa; G. Cornacchia; M. Notornicola; F. Voltasio; Vinod Kumar Sharma
Nonparametric identification and adaptive control of an anaerobic fluidized bed digester
In this paper, a new adaptive and robust control algorithm that is able to successfully deal with unpredictable internal changes (unmodeled dynamics) and external disturbances (changes in input) of the processes in an anaerobic digestion bioreactor is presented. The adaptive controller is based on a nonparametric statistical approach of the process identification. The regulation is done by optimally adapting the
Nadine Hilgert; J�r�me Harmand; Jean-Philippe Steyer; Jean-Pierre Vila
Purification of coal gasification combined with brewery waste waters in upflow anaerobic sludge blanket digesters
Laboratory-scale upflow anaerobic sludge blanket (UASB) digesters containing granular sludge adapted to brewery effluent were fed increasing concentrations of artificial coal gasification (CG) waste water in brewery effluent and were effective at purifying this combined waste water up to a CG effluent concentration of 15%. At higher CG waste water concentrations and flow rates, performance declined rapidly.
Alan R. Howgrave-Graham; Mike B. Nicholls
Optimization of biogas production by anaerobic digestion for sustainable energy development in Zimbabwe
There is increasing international interest in developing low carbon renewable energy technologies. Biomass is increasingly being utilized as an energy source throughout the world. Several modern technologies have been developed that convert biomass to bioenergy. Anaerobic digestion is a mature energy technology for converting biomass to biogas, which is a renewable primary energy source. Biogas is a robust fuel that
Raphael M. Jingura; Rutendo Matengaifa
Effect of temperature and solid concentration on anaerobic digestion of rice straw in South China
Anaerobic digestion (AD) technology for rice straw conversion to biogas was investigated for biomass utilization and bioenergy generation. The effects of solid concentration in different temperatures on AD efficiency were conducted in bottle-tests, these tests showed that higher biogas production was achieved at the mesophilic temperature. Biogas production was inhibited under thermophilic conditions, and lowest biogas production was achieved in
Li Lianhua; Li Dong; Sun Yongming; Ma Longlong; Yuan Zhenhong; Kong Xiaoying
Long-term effect of ZnO nanoparticles on waste activated sludge anaerobic digestion.
The increasing use of zinc oxide nanoparticles (ZnO NPs) raises concerns about their environmental impacts, but the potential effect of ZnO NPs on sludge anaerobic digestion remains unknown. In this paper, long-term exposure experiments were carried out to investigate the influence of ZnO NPs on methane production during waste activated sludge (WAS) anaerobic digestion. The presence of 1 mg/g-TSS of ZnO NPs did not affect methane production, but 30 and 150 mg/g-TSS of ZnO NPs induced 18.3% and 75.1% of inhibition respectively, which showed that the impact of ZnO NPs on methane production was dosage dependant. Then, the mechanisms of ZnO NPs affecting sludge anaerobic digestion were investigated. It was found that the toxic effect of ZnO NPs on methane production was mainly due to the release of Zn(2+) from ZnO NPs, which may cause the inhibitory effects on the hydrolysis and methanation steps of sludge anaerobic digestion. Further investigations with enzyme and fluorescence in situ hybridization (FISH) assays indicated that higher concentration of ZnO NPs decreased the activities of protease and coenzyme F(420), and the abundance of methanogenesis Archaea. PMID:21917290
Mu, Hui; Chen, Yinguang
Biological pretreatment applied to industrial organic fraction of municipal solid wastes (OFMSW): Effect on anaerobic digestion
The application of the anaerobic digestion for the treatment of the industrial organic fraction of municipal solid waste (OFMSW) has currently been of special interest. The main barrier in the treatment of this type or organic waste is its biotransformation, due to the complexity of organic material. Therefore, the first step must be its physical, chemical and biological pretreatment for
L. A. Fdez.-G�elfo; C. �lvarez-Gallego; D. Sales M�rquez; L. I. Romero Garc�a
Preliminary Comparison of Five Anaerobic Digestion Systems on Dairy Farms in New York State
As environmental regulations controlling direct land application of livestock waste increase, farmers search for ways to cost-effectively handle manure from their farms. Farmers' goals include efficient and effective means to remove the objectionable characteristics of their manure so that it may be recycled in an environmentally friendly manner. Anaerobic digestion is one way to control odors, liquefy manure and decrease
Peter Wright; Scott Inglis; Jianguo Ma; Curt Gooch; Brian Aldrich; Alex Meister; Norman Scott
Reducing the environmental impact of methane emissions from dairy farms by anaerobic digestion of cattle waste
Four dairy cattle farms considered representative of Northern Spain milk production were studied. Cattle waste was characterised and energy consumption in the farms was inventoried. Methane emissions due to slurry\\/manure management and fuel consumption on the farms were calculated. The possibility of applying anaerobic digestion to the slurry to minimise emissions and of using the biogas produced to replace fossil
E. Mara��n; A. M. Salter; L. Castrill�n; S. Heaven; Y. Fern�ndez-Nava
Prospect of anaerobic co-digestion of dairy manure: a review
Dairy manure is an abundant waste in dairy farming and poses handling, storage and disposal challenges. With poor management, dairy manure produces odour, ammonia and releases greenhouse gases that contribute to global warming. Anaerobic digestion (AD) is a means to produce renewable energy and to reduce environmental impacts resulting from improper management of dairy manure. Dairy manure AD suffers from
Eric Atandi; Shafiqur Rahman
Summary: A comparison of two existing odor control treatments on dairy farms in NY shows the costs and benefits of each system. On one dairy farm an anaerobic digester is used to stabilize the manure and collect methane for the production of electricity. The effluent is then separated. The solids are sold, and the liquid effluent is then land applied.
Peter E. Wright; Stephen P. Perschke
Alkali pretreatment enhances biogas production in the anaerobic digestion of pulp and paper sludge
The objective of this research was to develop an alkali pretreatment process prior to anaerobic digestion (AD) of pulp and paper sludge (PPS) to improve the methane productivity. Different concentrations of sodium hydroxide solution were used to pretreat PPS, and then followed by AD of PPS and monosodium glutamate waste liquor (MGWL).Laboratory-scale experiments were carried out in completely mixed bioreactors,
Yunqin Lin; Dehan Wang; Shaoquan Wu; Chunmin Wang
A comparative study of anaerobically digested and undigested sewage sludges in preparation of activated carbons
Disposal of sewage sludge is an increasingly expensive and environmentally sensitive problem throughout the world. Preparation of activated carbon from sewage sludge offers an attractive re-use alternative to the traditional disposal routes. The objective of this research work was to compare anaerobically digested sewage sludge (DS) and undigested sewage sludge (US) as source materials in the preparation of activated carbons.
J. H Tay; X. G Chen; S Jeyaseelan; N Graham
Anaerobic co-digestion of algal sludge and waste paper to produce methane
The unbalanced nutrients of algal sludge (low C\\/N ratio) were regarded as an important limitation factor to anaerobic digestion process. Adding high carbon content of waste paper in algal sludge feedstock to have a balanced C\\/N ratio was undertaken in this study. The results showed adding 50% (based on volatile solid) of waste paper in algal sludge feedstock increased the
Hong-Wei Yen; David E. Brune
Integrated treatment of olive oil mill effluents (OME): Study of ozonation coupled with anaerobic digestion
The possibility of coupling a chemical treatment (ozonation) with a biological treatment (anaerobic digestion), is investigated for olive oil mill effluents (OME). Preliminary tests showed that both total phenols and unsaturated lipids are reduced to about 50% in 3h of ozonation and that the total COD remains about unvaried. Nevertheless ozonated OME exhibit in general a longer lag phase and
R. Andreozzi; G. Longo; M. Majone; G. Modesti
Thermophilic anaerobic digestion of Lurgi coal gasification wastewater in a UASB reactor.
Lurgi coal gasification wastewater (LCGW) is a refractory wastewater, whose anaerobic treatment has been a severe problem due to its toxicity and poor biodegradability. Using a mesophilic (35�2�C) reactor as a control, thermophilic anaerobic digestion (55�2�C) of LCGW was investigated in a UASB reactor. After 120 days of operation, the removal of COD and total phenols by the thermophilic reactor could reach 50-55% and 50-60% respectively, at an organic loading rate of 2.5 kg COD/(m(3) d) and HRT of 24 h; the corresponding efficiencies were both only 20-30% in the mesophilic reactor. After thermophilic digestion, the wastewater concentrations of the aerobic effluent COD could reach below 200 mg/L compared with around 294 mg/L if mesophilic digestion was done and around 375 mg/L if sole aerobic pretreatment was done. The results suggested that thermophilic anaerobic digestion improved significantly both anaerobic and aerobic biodegradation of LCGW. PMID:21112778
Wang, Wei; Ma, Wencheng; Han, Hongjun; Li, Huiqiang; Yuan, Min
Removal of Ammonium from RO Permeate of Anaerobically Digested Wastewater by Natural Zeolite
The purpose of this paper was to study simultaneous removal of ammonia and potassium retained in wastewater by ion exchange with original and sodium conditioned zeolite after membrane treatment of anaerobically digested cattle manure effluents. Batch and column flow?through ion exchange tests were conducted to determine ion exchange capacity, pH effect, exchange kinetics, column runs and regeneration conditions. The exchange
Xuejun Guo; Larry Zeng; Xiaomei Li
Anaerobic Digestion for Reduction and Stabilization of Organic Solid Waste During Space Missions: Systems Analysis
High Solids Leachbed Anaerobic Digestion (HSLAD) is a biological waste treatment system that has been successfully demonstrated for solid waste treatment in terrestrial applications. The process involves a solid phase leachbed fermentation, employing leachate recycle between new and mature reactors for inoculation, wetting, and removal of volatile organic acids during startup. HSLAD also offers a potential option for treatment of
Qiyong Xu; Tim Townsend; David Chynoweth; Patrick Haley; John Owens; Elana Rich; Sabrina Maxwell; Hong-Lim Choi
Ethanol production from maize silage as lignocellulosic biomass in anaerobically digested and wet-oxidized manure
In this communication, pretreatment of the anaerobically digested (AD) manure and the application of the pretreated AD manure as liquid medium for the simultaneous saccharification and fermentation (SSF) were described. Furthermore, fermentation of pretreated maize silage and wheat straw was investigated using 2l bioreactors. Wet oxidation performed for 20min at 121�C was found as the most suitable pretreatment conditions for
Piotr Oleskowicz-Popiel; Przemyslaw Lisiecki; Jens Bo Holm-Nielsen; Anne Belinda Thomsen; Mette Hedegaard Thomsen
Minimisation of excess sludge production in a WWTP by coupling thermal hydrolysis and rapid anaerobic digestion.
In many cases, reducing sludge production could be the solution for wastewater treatment plants (WWTP) that here difficulty evacuating the residuals of wastewater treatment. The aim of this study was to test the possibility of minimising the excess sludge production by coupling a thermal hydrolysis stage and an anaerobic digestion with a very short HRT. The tests were carried out on a 2,500 p.e. pilot plant installed on a recycling loop between the clarifier and the actived sludge basin. The line equipped with the full scale pilot plant produced 38% TSS less than the control line during a 10 week period. Moreover, the rapid anaerobic digestion removed, on average, more than 50% of the total COD load with a hydraulic retention time (HRT) of 3 days. Lastly, the dryness of the remaining excess sludge, sanitised by the thermal hydrolysis, was more than 35% with an industrial centrifuge. This combination of thermal hydrolysis and rapid anaerobic digestion equally permits a significant gain of compactness compared to traditional anaerobic digesters. PMID:16459799
Chauzy, J; Graja, S; Gerardin, F; Cr�tenot, D; Patria, L; Fernandes, P
Anaerobic digestion of industrial hemp�Effect of harvest time on methane energy yield per hectare
There is a worldwide emphasis to increase the share of renewable transportation fuels. When using agricultural land for production of renewable transportation fuels, the energy output per hectare for different crops and transportation fuels is a crucial factor. In this study, the gross methane energy yield per hectare from anaerobic digestion of industrial hemp (Cannabis sativa L.), was determined at
E. Kreuger; T. Prade; F. Escobar; S.-E. Svensson; J.-E. Englund; L. Bj�rnsson
Anaerobic Digestion. Selected Instructional Activities and References. Instructional Resources Monograph Series.
Focusing specifically on the wastewater treatment process of anaerobic digestion, this document identifies instructional and reference materials for use by professionals in the field in the development and implementation of new programs or in the updating of existing programs. It is designed to help trainers, plant operators, educators, engineers,�
Townsend, Robert D., Comp.
Anaerobic co-digestion of sewage sludge and primary clarifier skimmings for increased biogas production.
The objective of the study was to identify the impact of co-digesting clarifier skimmings on the overall methane generation from the treatment plant and additional energy value of the increased methane production. Biogas production from co-digesting clarifier skimmings and sewage sludge in pilot-scale fed-batch mesophilic anaerobic digesters has been evaluated. The digester was fed with increasing quantities of clarifier skimmings loads: 1.5, 2.6, 3.5 and 7.0 g COD equivalent/(L�d) (COD: chemical oxygen demand). Average volatile solids reduction of 65% was achieved in the scum-fed digester, compared with 51% in the control digester. Average 69% COD removal was achieved at highest scum loading (7 g COD eq/(L�d)) with approximate methane yield of 250 L CH(4)/kg COD fed (4 ft(3)/lb COD fed). The results show that scum as co-substrate in anaerobic digestion systems improves biogas yields while a 29% increase in specific CH(4) yield could be achieved when scum load is 7 g COD eq/(L�d). Based on the pilot-scale study results and full-scale data from South East Water Pollution Control Plant and Northeast Water Pollution Control Plant the expected annual energy recovery would be approximately 1.7 billion BTUs or nearly 0.5 million kWh. PMID:23128636
Alanya, S; Yilmazel, Y D; Park, C; Willis, J L; Keaney, J; Kohl, P M; Hunt, J A; Duran, M
Modelling the energy balance of an anaerobic digester fed with cattle manure and renewable energy crops.
Knowledge of the net energy production of anaerobic fermenters is important for reliable modelling of the efficiency of anaerobic digestion processes. By using the Anaerobic Digestion Model No. 1 (ADM1) the simulation of biogas production and composition is possible. This paper shows the application and modification of ADM1 to simulate energy production of the digestion of cattle manure and renewable energy crops. The paper additionally presents an energy balance model, which enables the dynamic calculation of the net energy production. The model was applied to a pilot-scale biogas reactor. It was found in a simulation study that a continuous feeding and splitting of the reactor feed into smaller heaps do not generally have a positive effect on the net energy yield. The simulation study showed that the ratio of co-substrate to liquid manure in the inflow determines the net energy production when the inflow load is split into smaller heaps. Mathematical equations are presented to calculate the increase of biogas and methane yield for the digestion of liquid manure and lipids for different feeding intervals. Calculations of different kinds of energy losses for the pilot-scale digester showed high dynamic variations, demonstrating the significance of using a dynamic energy balance model. PMID:17631938
L�bken, Manfred; Wichern, Marc; Schlattmann, Markus; Gronauer, Andreas; Horn, Harald
Anaerobic digester foaming in full-scale cylindrical digesters--effects of organic loading rate, feed characteristics, and mixing.
Cylindrical anaerobic digesters (AD) were investigated to determine the causes and contributors of AD foaming due to the following: organic loading rate (OLR) and mixing effects, waste activated sludge (WAS) storage effects and foam suppression mixing at the surface of AD, and the effects of primary sludge (PS) solids fraction in the feed sludge. No foaming was observed over the duration of the study, indicating absence of a primary foaming cause even though the suspected contributors to AD foaming were present. Total solids and temperature profiles showed that reducing mixing frequency did not significantly impact digester performance or the homogeneity of the digester contents. The results showed that high organic loading rates, reduced mixing, and feed sludge storage by themselves do not cause foaming in most ADs when the primary foaming cause is absent. Reduced mixing and surface sludge sprays are practical strategies to control AD foaming. PMID:24650532
Subramanian, Bhargavi; Pagilla, Krishna R
Anaerobic digestion of source-segregated domestic food waste: performance assessment by mass and energy balance.
An anaerobic digester receiving food waste collected mainly from domestic kitchens was monitored over a period of 426 days. During this time information was gathered on the waste input material, the biogas production, and the digestate characteristics. A mass balance accounted for over 90% of the material entering the plant leaving as gaseous or digestate products. A comprehensive energy balance for the same period showed that for each tonne of input material the potential recoverable energy was 405 kWh. Biogas production in the digester was stable at 642 m3 tonne(-1) VS added with a methane content of around 62%. The nitrogen in the food waste input was on average 8.9 kg tonne(-1). This led to a high ammonia concentration in the digester which may have been responsible for the accumulation of volatile fatty acids that was also observed. PMID:20797849
Banks, Charles J; Chesshire, Michael; Heaven, Sonia; Arnold, Rebecca
Benefits of supplementing an industrial waste anaerobic digester with energy crops for increased biogas production
Highlights: Black-Right-Pointing-Pointer This study demonstrates the feasibility of co-digestion food industrial waste with energy crops. Black-Right-Pointing-Pointer Laboratory batch co-digestion led to improved methane yield and carbon to nitrogen ratio as compared to mono-digestion of industrial waste. Black-Right-Pointing-Pointer Co-digestion was also seen as a means of degrading energy crops with nutrients addition as crops are poor in nutrients. Black-Right-Pointing-Pointer Batch co-digestion methane yields were used to predict co-digestion methane yield in full scale operation. Black-Right-Pointing-Pointer It was concluded that co-digestion led an over all economically viable process and ensured a constant supply of feedstock. - Abstract: Currently, there is increasing competition for waste as feedstock for the growing number of biogas plants. This has led to fluctuation in feedstock supply and biogas plants being operated below maximum capacity. The feasibility of supplementing a protein/lipid-rich industrial waste (pig manure, slaughterhouse waste, food processing and poultry waste) mesophilic anaerobic digester with carbohydrate-rich energy crops (hemp, maize and triticale) was therefore studied in laboratory scale batch and continuous stirred tank reactors (CSTR) with a view to scale-up to a commercial biogas process. Co-digesting industrial waste and crops led to significant improvement in methane yield per ton of feedstock and carbon-to-nitrogen ratio as compared to digestion of the industrial waste alone. Biogas production from crops in combination with industrial waste also avoids the need for micronutrients normally required in crop digestion. The batch co-digestion methane yields were used to predict co-digestion methane yield in full scale operation. This was done based on the ratio of methane yields observed for laboratory batch and CSTR experiments compared to full scale CSTR digestion of industrial waste. The economy of crop-based biogas production is limited under Swedish conditions; therefore, adding crops to existing industrial waste digestion could be a viable alternative to ensure a constant/reliable supply of feedstock to the anaerobic digester.
Nges, Ivo Achu, E-mail: email@example.com [Department of Biotechnology, Lund University, P.O. Box 124, SE 221 00 Lund (Sweden); Escobar, Federico; Fu Xinmei; Bjoernsson, Lovisa [Department of Biotechnology, Lund University, P.O. Box 124, SE 221 00 Lund (Sweden)
Anaerobic co-digestion of chicken manure and corn stover in batch and continuously stirred tank reactor (CSTR).
Anaerobic co-digestion of chicken manure and corn stover in batch and CSTR were investigated. The batch co-digestion tests were performed at an initial volatile solid (VS) concentration of 3gVS/L, carbon-to-nitrogen (C/N) ratio of 20, and retention time of 30d. The methane yield was determined to be 281�12mL/gVSadded. Continuous reactor was carried out with feeding concentration of 12% total solids and C/N ratio of 20 at organic loading rates (OLRs) of 1-4gVS/L/d. Results showed that at OLR of 4gVS/L/d, stable and preferable methane yield of 223�7mL/gVSadded was found, which was equal to energy yield (EY) of 8.0�0.3MJ/kgVSadded. Post-digestion of digestate gave extra EY of 1.5-2.6MJ/kgVSadded. Pyrolysis of digestate provided additional EY of 6.1MJ/kgVSadded. Pyrolysis can be a promising technique to reduce biogas residues and to produce valuable gas products simultaneously. PMID:24531118
Li, Yeqing; Zhang, Ruihong; He, Yanfeng; Zhang, Chenyu; Liu, Xiaoying; Chen, Chang; Liu, Guangqing
Characterization and single-stage denitrification anaerobic digestion of spent stream from the hydrolysis-fermentation-combustion process
The demand for ethanol as an oxygenate and octane booster in automobile fuel is growing. A number of processes are being investigated for conversion of biomass to ethanol. The Hydrolysis-Fermentation-Combustion (HFC) process for fuel ethanol production developed at the University of California Forest Products Laboratory, Richmond, California is at the stage of technology transfer following over two decades of research and development. This study addresses the technology to be used in treatment of spent streams to be discharged from this process. The treatment design combines a single stage denitrification and anaerobic digestion (SSDAD) for the biological treatment of a representative stream from this process. A typical spent stream contained a wide range of soluble organic materials including: unfermented sugars, components of the feedstocks solubilized in the hydrolysis, acid degradation products of carbohydrates, cleavage products of lignin, water-soluble extractives and phenolics, terpenes and other unfermented organic material, and nitrate ion from the nitric acid used as a catalyst in the hydrolysis reaction. Three sets of experiments were conducted in laboratory scale anaerobic digesters. Commonly available anaerobic sludge from local sewage treatment plants was used as a starter seed and was successfully acclimated to the high nitrate substrate leading to enrichment of denitrifiers. Necessary nutrients and trace elements were identified and supplied to satisfy the obligatory requirements of different groups of bacterial groups present. A major finding was the unique role of ammonium hydroxide in controlling pH leading to steady-state operation of the digester. At steady state operation the reduction in COD was 65%, the nitrate reduction was 88% and the nitrite reduction was 100%. Nitrate was reduced to safe nitrogen gas without buildup of any intermediate products. Organic material was converted to useful methane gas and carbon dioxide. The SSDAD system was shown to be effective in treating spent streams having high COD and nitrate concentrations.
Singh, Ramnik
Emission of greenhouse gases from home aerobic composting, anaerobic digestion and vermicomposting of household wastes in Brisbane (Australia).
This study investigated greenhouse gas (GHG) emissions from three different home waste treatment methods in Brisbane, Australia. Gas samples were taken monthly from 34 backyard composting bins from January to April 2009. Averaged over the study period, the aerobic composting bins released lower amounts of CH(4) (2.2 mg m(- 2) h(-1)) than the anaerobic digestion bins (9.5 mg m(-2) h(-1)) and the vermicomposting bins (4.8 mg m(-2) h( -1)). The vermicomposting bins had lower N(2)O emission rates (1.2 mg m(-2) h(- 1)) than the others (1.5-1.6 mg m(-2) h( -1)). Total GHG emissions including both N(2)O and CH(4) were 463, 504 and 694 mg CO(2)-e m(- 2) h(-1) for vermicomposting, aerobic composting and anaerobic digestion, respectively, with N(2)O contributing >80% in the total budget. The GHG emissions varied substantially with time and were regulated by temperature, moisture content and the waste properties, indicating the potential to mitigate GHG emission through proper management of the composting systems. In comparison with other mainstream municipal waste management options including centralized composting and anaerobic digestion facilities, landfilling and incineration, home composting has the potential to reduce GHG emissions through both lower on-site emissions and the minimal need for transportation and processing. On account of the lower cost, the present results suggest that home composting provides an effective and feasible supplementary waste management method to a centralized facility in particular for cities with lower population density such as the Australian cities. PMID:20601402
Chan, Yiu C; Sinha, Rajiv K; Weijin Wang
Controlling the pH of acid cheese whey in a two-stage anaerobic digester with sodium hydroxide
Anaerobic digestion of cheese whey offers a two-fold benefit: pollution potential reduction and biogas production. The biogas, as an energy source, could be used to reduce the consumption of traditional fuels in the cheese plant. However, as a result of little or no buffering capacity of whey, the pH of the anaerobic digester drops drastically and the process is inhibited. In this study, the effect of controlling the pH of the second chamber of a two-stage, 150 L anaerobic digester operating on cheese whey on the quality and quantity of biogas and the pollution potential reduction, was investigated using sodium hydroxide. The digester was operated at a temperature of 35 C and a hydraulic retention time of 15 days for three runs (no pH control, pH control with no reseeding, and ph control with reseeding) each lasting 50 days. The results indicated that operating the digester without pH control resulted in a low pH (3.3) which inhibited the methanogenic bacteria. The inhibition was irreversible and the digester did not recover (no methane production) when the pH was restored to 7.0 without reseeding, as the observed increased gas production was a false indication of recovery because the gas was mainly carbon dioxide. The addition of base resulted in a total alkalinity of 12,000 mg/L as CaCO{sub 3}. When the system was reseeded and the pH controlled, the total volatile acid concentration was 15,100 mg/L (as acetic acid), with acetic (28%), propionic (21%), butyric (25%), valeric (8%), and caproic (15%) acids as the major constituents. The biogas production was 62.6 L/d (0.84 m{sup 3}/m{sup 3}/d) and the methane content was 60.7%. Reductions of 27.3, 30.4 and 23.3% in the total solids, chemical oxygen demand and total kjeldahl nitrogen were obtained, respectively. The ammonium nitrogen content increased significantly (140%).
Ghaly, A.E.; Ramkumar, D.R. [Dalhousie Univ., Halifax, Nova Scotia (Canada). Biological Engineering Dept.
Semi-continuous anaerobic co-digestion of cow manure and steam-exploded Salix with recirculation of liquid digestate.
The effects of recirculating the liquid fraction of the digestate during mesophilic anaerobic co-digestion of steam-exploded Salix and cow manure were investigated in laboratory-scale continuously stirred tank reactors. An average organic loading rate of 2.6�g VS L(-1)�d(-1) and a hydraulic retention time (HRT) of 30 days were employed. Co-digestion of Salix and manure gave better methane yields than digestion of manure alone. Also, a 16% increase in the methane yield was achieved when digestate was recirculated and used instead of water to dilute the feedstock (1:1 dilution ratio). The reactor in which the larger fraction of digestate was recirculated (1:3 dilution ratio) gave the highest methane yields. Ammonia and volatile fatty acids did not reach inhibitory levels, and some potentially inhibitory compounds released during steam explosion (i.e., furfural and 5-hydroxy methyl furfural) were only detected at trace levels throughout the entire study period. However, accumulation of solids, which was more pronounced in the recycling reactors, led to decreased methane yields in those systems after three HRTs. Refraining from the use of fresh water to dilute biomass with a high-solids content and obtaining a final digestate with increased dry matter content might offer important economic benefits in full-scale processes. To ensure long-term stability in such an approach, it would be necessary to optimize separation of the fraction of digestate to be recirculated and also perform proper monitoring to avoid accumulation of solids. PMID:24534902
Estevez, Maria M; Sapci, Zehra; Linjordet, Roar; Schn�rer, Anna; Morken, John
A stable anaerobic degradation of swine manure with ammonia concentration of 6 g-N\\/litre was obtained in continuously stirred tank reactors with a hydraulic retention time of 15 days, at four different temperatures. Methane yields of 188, 141, 67 and 22 ml-CH4\\/g-VS were obtained at 37, 45, 55 and 60�C, respectively. The yields were significantly lower than the potential biogas yield
Anaerobic Digestion of Red and Chum Salmon Wastes. Final Report.
This report is on the second and final phase of a project designed to investigate the feasibility of digesting fish wastes to reduce pollution and recover useable oils, solids, and liquids. The first part of the project was a literature search to determin...
G. L. Turner
The effect of managing nutrients in the performance of anaerobic digesters of municipal wastewater treatment plants.
Is it possible to create conditions in the anaerobic digesters to control nutrients without changing the performance of a reactor? This study investigates an answer for this question. To this purpose, anaerobic reactors are operated at high concentrations of Mg(2+) ion to harvest the nutrient ions (NH4 (+) and PO4 (3-)) in the form of struvite, that is, magnesium ammonium phosphate. The effects of this modification on the anaerobic digestion of sewage sludge were investigated in terms of chemical oxygen demand (COD) removal and cumulative CH4 production as well as the changes in the biological diversity. The results showed that approximately 50�% of the nutrients (NH4 (+) and PO4 (3-)) were removed regardless of the method adopted for the addition of Mg(2+) ion, slug or daily dosing. The numbers of Methanosaeta and Methanosarcina in the samples withdrawn prior to and after the addition of Mg(2+) did not show significant difference according to the results obtained from qPCR analyses. The research results showed that the addition of Mg(2+) into the anaerobic digesters in municipal wastewater treatment facilities may help to remove the nutrients from the effluent while recovering in their solid forms. PMID:23090053
Demirer, Sibel Uludag; Taskin, Bilgin; Demirer, Goksel N; Duran, Metin
Enhanced methane production from Taihu Lake blue algae by anaerobic co-digestion with corn straw in continuous feed digesters.
Anaerobic digestion of Taihu blue algae was tested in laboratory scale, continuous feed digesters (hydraulic retention time 10 days) at 35�C and various organic loading rates (OLR). The methane production and biomass digestion performed well at OLR below 4.00 gVSL(-1)d(-1) but deteriorated as OLR increased due to the increased ammonia concentration, causing inhibition mainly to acetate and propionate degradation. Supplementing corn straw as co-feedstock significantly improved the digestion performance. The optimal C/N ratio for the co-digestion was 20:1 at OLR of 6.00 gVSL(-1) d(-1). Methane yield of 234 mL CH4 gVS(-1) and methane productivity of 1404 mL CH4 L(-1) d(-1) were achieved with solid removal of 63%. Compared with the algae alone, the methane productivity was increased by 46% with less accumulation of ammonia and fatty acids. The reactor rate-limiting step was acetate and propionate degradation. PMID:23506978
Zhong, Weizhang; Chi, Lina; Luo, Yijing; Zhang, Zhongzhi; Zhang, Zhenjia; Wu, Wei-Min
Hyperspectral imaging techniques applied to the monitoring of wine waste anaerobic digestion process
An anaerobic digestion process, finalized to biogas production, is characterized by different steps involving the variation of some chemical and physical parameters related to the presence of specific biomasses as: pH, chemical oxygen demand (COD), volatile solids, nitrate (NO3-) and phosphate (PO3-). A correct process characterization requires a periodical sampling of the organic mixture in the reactor and a further analysis of the samples by traditional chemical-physical methods. Such an approach is discontinuous, time-consuming and expensive. A new analytical approach based on hyperspectral imaging in the NIR field (1000 to 1700 nm) is investigated and critically evaluated, with reference to the monitoring of wine waste anaerobic digestion process. The application of the proposed technique was addressed to identify and demonstrate the correlation existing, in terms of quality and reliability of the results, between "classical" chemical-physical parameters and spectral features of the digestate samples. Good results were obtained, ranging from a R2=0.68 and a RMSECV=12.83 mg/l for nitrate to a R2=0.90 and a RMSECV=5495.16 mg O2/l for COD. The proposed approach seems very useful in setting up innovative control strategies allowing for full, continuous control of the anaerobic digestion process.
Serranti, Silvia; Fabbri, Andrea; Bonifazi, Giuseppe
Evaluation of integrated anaerobic digestion and hydrothermal carbonization for bioenergy production.
Lignocellulosic biomass is one of the most abundant yet underutilized renewable energy resources. Both anaerobic digestion (AD) and hydrothermal carbonization (HTC) are promising technologies for bioenergy production from biomass in terms of biogas and HTC biochar, respectively. In this study, the combination of AD and HTC is proposed to increase overall bioenergy production. Wheat straw was anaerobically digested in a novel upflow anaerobic solid state reactor (UASS) in both mesophilic (37 �C) and thermophilic (55 �C) conditions. Wet digested from thermophilic AD was hydrothermally carbonized at 230 �C for 6 hr for HTC biochar production. At thermophilic temperature, the UASS system yields an average of 165 LCH4/kgVS�(VS: volatile solids) and 121 L CH4/kgVS�at mesophilic AD over the continuous operation of 200 days. Meanwhile, 43.4 g of HTC biochar with 29.6 MJ/kgdry_biochar was obtained from HTC of 1 kg digestate (dry basis) from mesophilic AD. The combination of AD and HTC, in this particular set of experiment yield 13.2 MJ of energy per 1 kg of dry wheat straw, which is at least 20% higher than HTC alone and 60.2% higher than AD only. PMID:24962786
Reza, M Toufiq; Werner, Maja; Pohl, Marcel; Mumme, Jan
Neutral fat hydrolysis and long-chain fatty acid oxidation during anaerobic digestion of slaughterhouse wastewater.
Neutral fat hydrolysis and long-chain fatty acid (LCFA) oxidation rates were determined during the digestion of slaughterhouse wastewater in anaerobic sequencing batch reactors operated at 25 degrees C. The experimental substrate consisted of filtered slaughterhouse wastewater supplemented with pork fat particles at various average initial sizes (D(in)) ranging from 60 to 450 microm. At the D(in) tested, there was no significant particle size effect on the first-order hydrolysis rate. The neutral fat hydrolysis rate averaged 0.63 +/- 0.07 d(-1). LCFA oxidation rate was modelled using a Monod-type equation. The maximum substrate utilization rate (kmax) and the half-saturation concentration (Ks) averaged 164 +/- 37 mg LCFA/L/d and 35 +/- 31 mg LCFA/L, respectively. Pork fat particle degradation was mainly controlled by LCFA oxidation rate and, to a lesser extent, by neutral fat hydrolysis rate. Hydrolysis pretreatment of fat-containing wastewaters and sludges should not substantially accelerate their anaerobic treatment. At a D(in) of 450 microm, fat particles were found to inhibit methane production during the initial 20 h of digestion. Inhibition of methane production in the early phase of digestion was the only significant effect of fat particle size on anaerobic digestion of pork slaughterhouse wastewater. Soluble COD could not be used to determine the rate of lipid hydrolysis due to LCFA adsorption on the biomass. PMID:17590931
Masse, L; Mass�, D I; Kennedy, K J; Chou, S P
Feasibility of spent metalworking fluids as co-substrate for anaerobic co-digestion.
In this paper, anaerobic co-digestion of spent metalworking fluids (SMWF) and pig manure (PM) was evaluated. Three SMWF:PM ratios were tested in order to find the highest process efficiency. The best results (COD removal efficiencies of 74%) were achieved co-digesting a mixture with a SMWF:PM ratio of 1:99, w/w(1) (corresponding to 3.75mL SMWF/Lreactor week), which indicates that SMWF did not affect negatively PM degradation. Furthermore, two different weekly SMWF pulse-frequencies were performed (one reactor received 1 pulse of 3.75mL/Lreactor and the other 3 pulses of 1.25mL/Lreactor) and no differences in COD removal efficiency were observed. Microbiology analysis confirmed that Pseudomonas was the predominant genus when treating anaerobically SMWF and the presence of a higher fraction of Archaea was indicative of good digester performance. This study confirms the feasibility of anaerobic co-digestion as an appropriate technology for treating and valorising SMWF. PMID:24457301
Rodriguez-Verde, Ivan; Regueiro, Leticia; Pena, Rocio; �lvarez, Juan A; Lema, Juan M; Carballa, Marta
Co-digestion of kitchen waste and fruit-vegetable waste by two-phase anaerobic digestion.
The high salinity and fat contents of kitchen waste (KW) inhibits the effect of two-phase anaerobic digestion system. This research introduces fruit-vegetable waste (FVW) to alleviate the inhibition effect caused by salinity and fat concentrations, and tries to achieve an optimal addition ratio of FVW, an optimal hydraulic remain time (HRT) of acidogenic-phase reactor and methanogenic-phase reactor. A two-phase anaerobic digestion (AD) system was developed to co-dispose KW and FVW. Four sets of experiments were run with different mass proportions between KW and FVW (25-75, 50-50, 75-25, and 100-0% m/m). Considering the biodegradation rate and the acidification degree, the system with 25% KW had the best performance during the acidogenic phase. When the system was run with 50% KW, it not only had the best stability performance but also had a bigger capacity to treat KW than the system with 25% KW. The system with 50% KW was the best ratio in this two-phase AD system. Co-digestion of KW and FVW by two-phase AD is feasible. The addition of FVW can reduce the inhibition effect caused by salinity and fat concentrations, reduce the HRT, and lead to a higher degree of acidification. PMID:23288673
Yang, Yu-Qiang; Shen, Dong-Sheng; Li, Na; Xu, Dong; Long, Yu-Yang; Lu, Xuan-Yu
Anaerobic digestion of animal waste: Effect of mode of mixing
Laboratory-scale digesters were operated to study the effect of mixing (via biogas recirculation, impeller mixing, and slurry recirculation) on biogas production. Three sets of experiments were performed using cow manure slurry feed with either 50, 100, or 150g\\/L total solids (TS) concentrations (referred in the text as 5%, 10%, and 15% manure slurry). The experiments were conducted at a controlled
Khursheed Karim; Rebecca Hoffmann; K. Thomas Klasson; M. H. Al-Dahhan
Anaerobic digestion of corn stovers for methane production in a novel bionic reactor.
To improve the biogas production from corn stovers, a new bionic reactor was designed and constructed. The bionic reactor simulated the rumen digestion of ruminants. The liquid was separated from corn stovers and refluxed into corn stovers again, which simulated the undigested particles separated from completely digested materials and fed back again for further degradation in ruminant stomach. Results showed that the bionic reactor was effective for anaerobic digestion of corn stovers. The liquid amount and its reflux showed an obvious positive correlation with biogas production. The highest biogas production rate was 21.6ml/gVS-addedd, and the total cumulative biogas production was 256.5ml/gVS-added. The methane content in biogas ranged from 52.2% to 63.3%. The degradation of corn stovers were greatly enhanced through simulating the animal digestion mechanisms in this bionic reactor. PMID:24923659
Zhang, Meixia; Zhang, Guangming; Zhang, Panyue; Fan, Shiyang; Jin, Shuguang; Wu, Dan; Fang, Wei
Combined thermophilic aerobic process and conventional anaerobic digestion: effect on sludge biodegradation and methane production.
The efficiency of hyper-thermophilic (65 degrees Celsius) aerobic process coupled with a mesophilic (35 degrees Celsius) digester was evaluated for the activated sludge degradation and was compared to a conventional mesophilic digester. For two Sludge Retention Time (SRT), 21 and 42 days, the Chemical Oxygen Demand (COD) solubilisation and biodegradation processes, the methanisation yield and the aerobic oxidation were investigated during 180 days. The best results were obtained at SRT of 44 days; the COD removal yield was 30% higher with the Mesophilic Anaerobic Digestion/Thermophilic Aerobic Reactor (MAD-TAR) co-treatment. An increase of the sludge intrinsic biodegradability is also observed (20-40%), showing that the unbiodegradable COD in mesophilic conditions becomes bioavailable. However, the methanisation yield was quite similar for both processes at a same SRT. Finally, such a process enables to divide by two the volume of digester with an equivalent efficiency. PMID:19959355
Dumas, C; Perez, S; Paul, E; Lefebvre, X
Electrochemical oxidation of the effluent from anaerobic digestion of dairy manure.
The electrochemical oxidation of the digested effluent from anaerobic digestion of dairy manure was investigated in this study. The digested effluent sample containing with suspended solids was pretreated by filtration for the electrochemical experiment. The influence of direct anodic oxidation and indirect oxidation was evaluated through the use of dimensionally stable anode (DSA) and Ti/PbO2 as anode. The decreasing rate of chemical oxygen demand (COD) was higher at lead dioxide coated titanium (Ti/PbO2) electrode than at DSA, however the DSA was preferred anode for the decrease of ammonium nitrogen (NH4-N) due to the control of ammonium nitrate (NO3-N) accumulation. The results showed that the filtration of suspended solids as a pretreatment and addition of NaCl could improve the whole removing efficiency of NH4-N in the digested effluent on electrochemical oxidation. PMID:16125931
Ihara, Ikko; Umetsu, Kazutaka; Kanamura, Kiyoshi; Watanabe, Tsuneo
The authors examined the anaerobic degradation of phenol and the ortho, meta, and para isomers of chlorophenol, methoxyphenol, methylphenol (cresol),and nitrophenol in anaerobic sewage sludge diluted to 10% in a mineral salts medium. Of the 12 monosubstituted phenols studied, only p-chlorophenol and o-cresol were not significantly degraded during an 8-week incubation period. The phenol compounds degraded and the time required for complete substrate disappearance (in weeks) were: phenol (2), o-chlorophenol (3), m-chlorophenol (7), o-methoxyphenol (2), m- and p-methoxyphenol (1), m-cresol (7), p-cresol (3), and o-, m-, and p-nitrophenol (1). Complete mineralization of phenol, o-chlorophenol, m-cresol, p-cresol, o-nitrophenol, p-nitrophenol, and o-, m-, and p-methoxyphenol was observed. In general, the presence of Cl and NO/sub 2/ groups on phenols inhibited methane production. Elimination or transformation of these substituents was accompanied by increased methane production. o-Chlorophenol was metabolized to phenol, which indicated that dechlorination was the initial degradation step. The methoxyphenols were transformed to the corresponding dihydroxybenzene compounds, which were subsequently mineralized. (Refs. 14).
Boyd, S.A.; Shelton, D.R.; Berry, D.; Tiedje, J.M.
Full-stream and part-stream ultrasound treatment effect on sludge anaerobic digestion.
The use of ultrasound as pre-treatment to improve anaerobic digestion of secondary sludge has been established as a promising technology. There are great differences between lab scale and full-scale devices, regarding the relationship between the disintegration achieved and the energy supplied. Based on economic aspects, most of the full-scale plants use partial-stream instead of the full-stream sonication, which affects biogas production and digestate dewatering characteristics. A laboratory scale operation combining ultrasound and anaerobic digestion (batch tests) has been performed, determining the relationship between the ratio of sonicated sludge fed and the methane production, SCOD removal and capillary suction time after 20-day anaerobic biodegradation, in order to check the possible benefits of part-stream versus full-stream sonication. Additional incubation was also evaluated, searching for an optimum process combining ultrasound and 24-h incubation pretreatment. Results showed that by sonicating fresh WAS at 25,700 kJ/kg TS biogas yield increased linearly with the percentage of sonicated WAS in the substrate, from 248 (control reactor) to 349 mL CH(4)/g VS (41% increase in full-stream sonication). By incubation (24 h, 55 degrees C), 325 mL CH(4)/g VS were obtained (31% increase), but the digestion of the soluble compounds generated during incubation of sonicated sludge appeared to be less degradable compared to those solubilised by ultrasound or incubation alone, which showed no benefit in combining both treatments. Post-digestion dewatering deteriorated for both part-stream and full-stream sonication, and CST values were constant (74% higher than the control digestate) from 30% to 100% sonicated sludge. PMID:20351414
P�rez-Elvira, S I; Ferreira, L C; Donoso-Bravo, A; Fdz-Polanco, M; Fdz-Polanco, F
Study of the operational conditions for anaerobic digestion of urban solid wastes.
This paper describes an experimental evaluation of anaerobic digestion technology as an option for the management of organic solid waste in developing countries. As raw material, a real and heterogeneous organic waste from urban solid wastes was used. In the first experimental phase, seed selection was achieved through an evaluation of three different anaerobic sludges coming from wastewater treatment plants. The methanization potential of these sludges was assessed in three different batch digesters of 500 mL, at two temperature levels. The results showed that by increasing the temperature to 15 degrees C above room temperature, the methane production increases to three times. So, the best results were obtained in the digester fed with a mixed sludge, working at mesophilic conditions (38-40 degrees C). Then, this selected seed was used at the next experimental phase, testing at different digestion times (DT) of 25, 20 and 18 days in a bigger batch digester of 20 L with a reaction volume of 13 L. The conversion rates were registered at the lowest DT (18 days), reaching 44.9 L/kg(-1) of wet wasteday(-1). Moreover, DT also has a strong influence over COD removal, because there is a direct relationship between solids removal inside the reactor and DT. PMID:16321515
M, Edgar Fernando Castillo; Cristancho, Diego Edison; Arellano, A Victor
Effect of solids retention time on the bioavailability of organic carbon in anaerobically digested swine waste.
Anaerobic digestion (AD) can be used to stabilize and produce energy from livestock waste; however, digester effluents may require further treatment to remove nitrogen. This paper quantifies the effects of varying solids retention time (SRT) methane yield, volatile solids (VS) reduction and organic carbon bioavailability for denitrification during swine waste AD. Four bench-scale anaerobic digesters, with SRTs of 14, 21, 28 and 42days, operated with swine waste feed. Effluent organic carbon bioavailability was measured using anoxic microcosms and respirometry. Excellent performance was observed for all four digesters, with >60% VS removal and CH4 yields between 0.1 and 0.3(m(3)CH4)/(kgVS added). Organic carbon in the centrate as an internal organic carbon source for denitrification supported maximum specific denitrification rates between 47 and 56(mgNO3(-)-N)/(gVSSh). The digester with the 21-day SRT had the highest CH4 yield and maximum specific denitrification rates. PMID:24736207
Kinyua, Maureen N; Cunningham, Jeffrey; Ergas, Sarina J
Effects of thermal pretreatment on anaerobic digestion of Nannochloropsis salina biomass.
The marine microalga Nannochloropsis salina was investigated as feedstock for anaerobic digestion under batch and semi-continuous conditions for the first time. Biodegradability and methane yield were low under both digestion conditions. Thermal pretreatment prior to anaerobic digestion significantly increased the methane yield from 0.2 to 0.57 m(3) kg VS(-1) under batch conditions and from 0.13 to 0.27 m(3) kg VS(-1) in semi-continuous digestion. Still, the methane yield was limited with semi-continuous feeding due to volatile fatty acid (VFA) accumulation in the digester caused by high ammonium and salt concentrations in the feedstock. Despite VFA accumulation adaption of the microorganisms to the changing conditions and high buffer capacity resulted in steady methane production. A first energy balance considering the required heat for thermal pretreatment revealed significant benefit from the pretreatment. Conversely, the high energy demand for dewatering algal cultures is one major bottleneck for industrial-scale processing of microalgae. PMID:23831893
Schwede, Sebastian; Rehman, Zia-Ur; Gerber, Mandy; Theiss, Carsten; Span, Roland
The Water Environment Research Foundation (WERF) recently published a report titled Examination of Reactivation and Regrowth of Fecal Coliforms in Anaerobically Digested Sludges. Seven full-scale publicly owned treatment facilities were sampled several times to determine if bacte...
CFD simulation of mechanical draft tube mixing in anaerobic digester tanks.
Computational Fluid Dynamics (CFD) was used to simulate the mixing characteristics of four different circular anaerobic digester tanks (diameters of 13.7, 21.3, 30.5, and 33.5m) equipped with single and multiple draft impeller tube mixers. Rates of mixing of step and slug injection of tracers were calculated from which digester volume turnover time (DVTT), mixture diffusion time (MDT), and hydraulic retention time (HRT) could be calculated. Washout characteristics were compared to analytic formulae to estimate any presence of partial mixing, dead volume, short-circuiting, or piston flow. CFD satisfactorily predicted performance of both model and full-scale circular tank configurations. PMID:19135698
Meroney, Robert N; Colorado, P E
Start-up of an anaerobic dynamic membrane digester for waste activated sludge digestion: temporal variations in microbial communities.
An anaerobic dynamic membrane digester (ADMD) was developed to digest waste sludge, and pyrosequencing was used to analyze the variations of the bacterial and archaeal communities during the start-up. Results showed that bacterial community richness decreased and then increased over time, while bacterial diversity remained almost the same during the start-up. Proteobacteria and Bacteroidetes were the major phyla. At the class level, Betaproteobacteria was the most abundant at the end of start-up, followed by Sphingobacteria. In the archaeal community, richness and diversity peaked at the end of the start-up stage. Principle component and cluster analyses demonstrated that archaeal consortia experienced a distinct shift and became stable after day 38. Methanomicrobiales and Methanosarcinales were the two predominant orders. Further investigations indicated that Methanolinea and Methanosaeta were responsible for methane production in the ADMD system. Hydrogenotrophic pathways might prevail over acetoclastic means for methanogenesis during the start-up, supported by specific methanogenic activity tests. PMID:24695488
Yu, Hongguang; Wang, Qiaoying; Wang, Zhiwei; Sahinkaya, Erkan; Li, Yongli; Ma, Jinxing; Wu, Zhichao
Start-Up of an Anaerobic Dynamic Membrane Digester for Waste Activated Sludge Digestion: Temporal Variations in Microbial Communities
An anaerobic dynamic membrane digester (ADMD) was developed to digest waste sludge, and pyrosequencing was used to analyze the variations of the bacterial and archaeal communities during the start-up. Results showed that bacterial community richness decreased and then increased over time, while bacterial diversity remained almost the same during the start-up. Proteobacteria and Bacteroidetes were the major phyla. At the class level, Betaproteobacteria was the most abundant at the end of start-up, followed by Sphingobacteria. In the archaeal community, richness and diversity peaked at the end of the start-up stage. Principle component and cluster analyses demonstrated that archaeal consortia experienced a distinct shift and became stable after day 38. Methanomicrobiales and Methanosarcinales were the two predominant orders. Further investigations indicated that Methanolinea and Methanosaeta were responsible for methane production in the ADMD system. Hydrogenotrophic pathways might prevail over acetoclastic means for methanogenesis during the start-up, supported by specific methanogenic activity tests.
Detailed study of anaerobic digestion of Spirulina maxima algae biomass
Biomass of the blue-green alga Spirulina maxima was converted to methane using continuous stirred tank digesters with an energy conversion efficiency of 59%. Digesters were operated using once-a-day feeding with a retention time (theta) between 5 and 40 days, volatile solid concentrations (Sto) between 20 and 100 kg VS/cubic m, and temperatures between 15 and 52/sup 0/C. The results indicated a maximum methane yield of 0.35 cubic m (STP)/kg VS added at theta = 30 days and Sto = 20 kg VS/cubic m. Under such conditions, the energy conversion of the algal biomass to methane was 59%. The maximum methane production rate of 0.80 cubic m (STP)/cubic m day was obtained with theta = 20 days and Sto = 100 kg VS/cubic m. The mesophilic condition at 35/sup 0/C produced the maximum methane yield and production rate. The process was stable and characterized by a high production of volatile acids (up to 23,200 mg/l), alkalinity (up to 20,000 mg/l), and ammonia (up to 7000 mg/l), and the high protein content of the biomass produced a well-buffered environment which reduced inhibitory effects. At higher loading rates, the inhibition of methanogenic bacteria was observed, but there was no clear-cut evidence that such a phenomenon was due to nonionized volatile acids or gaseous ammonia. The kinetic analysis using the model proposed by Chen and Hashimoto indicated that the minimum retention time was seven days. The optimum retention time increased gradually from 11 to 16 days with an increase in the initial volatile solid concentration. The kinetic constant K decreased with the improvement in the digester performance and increased in parallel with the ammonia concentration in the culture media. 32 references.
Samson, R.; LeDuy, A.
WASTEWATER reclamation and methane production using water hyacinth and anaerobic digestion
This paper describes the results of research in progress to evaluate the technical and economic feasibility of utilizing water hyacinth ponds for treatment of domestic wastewater and the utilization of anaerobic digestion for conversion of the hyacinth crop and primary sludge to methane. The system concept illustrated in Figure I employs water hyacinth ponds for secondary and tertiary treatment of effluent from primary treatment (which removes settleable solids). Primary effluent supernatant is passed through water hyacinth ponds which effect organic and nutrient reduction. Collected primary sludge and harvested hyacinth are added as a blend to the anaerobic digestion process where a portion of the organic matter is converted to methane and carbon dioxide. The methane is separated from the carbon dioxide and used as an energy product.
Chynoweth, D.P.; DoLenc, D.A.; Reddy, K.R.; Schwegler, B.
The fate of antagonistic microorganisms and antimicrobial substances during anaerobic digestion of pig and dairy manure.
The goals of the present study were to evaluate the suppressive capability of anaerobically digested slurry (ADS) against Phytophthora capsici and to determine the key factors of disease control in ADS. This was achieved by the investigations of the changes in microbial populations and the levels of antimicrobial compound during anaerobic digestion (AD). AD had no significant impact on the numbers of antagonistic fluorescent pseudomonads or Bacillus sp. The contents of total phenolics, volatile fatty acids and sugar fed with the raw slurries to the reactors were decreased by AD. However, the bioreactor effluents had higher concentrations of humic substances and ammonia than the feedstocks. Moreover, AD had a different influence on the content of amino acid in the pig manure compared to the dairy manure. The results obtained indicated that the key inhibitory factors of ADS might be attributed to ammonia and humic substances. PMID:23570714
Cao, Yun; Chang, Zhizhou; Wang, Jidong; Ma, Yan; Fu, Guangqin
Electrochemical treatment of anaerobic digestion effluent using a Ti/Pt-IrO2 electrode.
Electrochemical treatment of the anaerobic digestion effluents using a Ti/Pt-IrO(2) electrode was evaluated in this study. The effects of electric current, NaCl dosage, and initial pH on ammonia, nitrate, total organic carbon (TOC), inorganic carbon (IC), final pH, and turbidity variations were studied in a series of batch experiments. It was found that the electric current and NaCl dosage had a considerably larger effect on the oxidization of ammonia; this was less for the effect of the initial pH. In addition, electroflotation was the main mechanism for turbidity, TOC, and IC removals. Further, the IC removal was mainly affected by the pH of wastewater. The electrochemical treatment using Ti/Pt-IrO(2) electrode without pretreatment was feasible for the anaerobic digestion effluent. PMID:17207618
Lei, Xiaohui; Maekawa, Takaaki
Microbial communities in anaerobic digestion processes for waste and wastewater treatment: a microbiological update.
Anaerobic digestion technology is the biological treatment of organic waste and wastewater without input of external electron acceptors (oxygen), offering the potential to reduce treatment cost and to produce energy as 'biogas' (methane) from organic waste. The technology has become enormously popular in the past two decades, and knowledge of microbiological aspects of the technology has also accumulated significantly. Major advances have been made in elucidating the diversity of yet-to-be cultured microbes in anaerobic digestion processes, and the cultivation of uncultured organisms is of great interest with regard to gaining insights into the function of these organisms. In addition, recent advances have been made in the development of microbial fuel cells as an alternative, direct energy-yielding treatment system. PMID:17462878
Narihiro, Takashi; Sekiguchi, Yuji
Review on the fate of emerging contaminants during sludge anaerobic digestion.
Several research papers have been published during the last years investigating the occurrence, fate and effects of emerging contaminants (ECs) on sludge anaerobic digestion (AD). Literature review revealed that research has been mainly focused on specific groups of compounds (linear alkylbenzene sulphonates, nonylphenol ethoxylates, some pharmaceuticals, estrogens, phthalates), while there are fewer or no data for others (personal care products, perfluorinated compounds, brominated flame retardants, organotins, benzotriazoles, benzothiazoles, nanoparticles). AD operational parameters (sludge residence time, temperature), sludge characteristics (type of sludge, adaptation on the compound), physicochemical properties of ECs and co-metabolic phenomena seem to affect compounds' biodegradation. The use of sludge pretreatment methods does not seem to enhance ECs removal; whereas encouraging results have been reported when AD was combined with other treatment methods. Future efforts should be focused on better understanding of biotransformation processes and sorption phenomena occurred in anaerobic digesters, as well as on identification of (bio)transformation products. PMID:22853968
Stasinakis, Athanasios S
NIR Monitoring of Ammonia in Anaerobic Digesters Using a Diffuse Reflectance Probe
The feasibility of using a diffuse reflectance probe attached to a near infrared spectrometer to monitor the total ammonia nitrogen (TAN) content in an anaerobic digester run on cattle manure was investigated; as a previous study has indicated that this probe can be easily attached to an anaerobic digester. Multivariate modelling techniques such as partial least squares regression and interval partial least squares methods were used to build models. Various data pre-treatments were applied to improve the models. The TAN concentrations measured were in the range of 1.5 to 5.5 g/L. An R2 of 0.91 with an RMSEP of 0.32 was obtained implying that the probe could be used for monitoring and screening purposes.
Raju, Chitra S.; L?kke, Mette Marie; Sutaryo, Sutaryo; Ward, Alastair J.; M?ller, Henrik B.
Metagenomic analysis of sludge from full-scale anaerobic digesters operated in municipal wastewater treatment plants.
This study applied Illumina high-throughput sequencing to explore the microbial communities and functions in anaerobic digestion sludge (ADS) from two wastewater treatment plants based on a metagenomic view. Taxonomic analysis using SILVA SSU database indicated that Proteobacteria (9.52-13.50�%), Bacteroidetes (7.18�%-10.65�%) and Firmicutes (7.53�%-9.46�%) were the most abundant phyla in the ADS. Differences of microbial communities between the two types of ADS were identified. Genera of Methanosaeta and Methanosarcina were the major methanogens. Functional analysis by SEED subsystems showed that the basic metabolic functions of metagenomes in the four ADS samples had no significant difference among them, but they were different from other microbial communities from activated sludge, human faeces, ocean and soil. Abundances of genes in methanogenesis pathway were also quantified using a methanogenesis genes database extracted from KEGG. Results showed that acetotrophic was the major methanogenic pathway in the anaerobic sludge digestion. PMID:24633414
Yang, Ying; Yu, Ke; Xia, Yu; Lau, Frankie T K; Tang, Daniel T W; Fung, Wing Cheong; Fang, Herbert H P; Zhang, Tong
Bio-Recovery of N and P from an Anaerobic Digester Effluent: The Potential of Duckweed (Lemna minor)
The possibility of growing duckweed (Lemna minor) on anaerobic digester effluent and its nitrogen and phosphorus acquisition potential was studied. Duckweed was cultured for 21 days on an anaerobic digester effluent using two methods: static aeration (SAT) and normal batch reactor (NBR) techniques, respectively. The treatments involved pure effluent and 1\\/10, 1\\/25 and 1\\/50 effluent dilutions, respectively. Fifty duckweed fronds
E. Abuaku; K. A. Frimpong; B. A. Osei; W. Verstraete
Effects of microbial and non-microbial factors of liquid anaerobic digestion effluent as inoculum on solid-state anaerobic digestion of corn stover.
The microbial activity of the inoculum (liquid anaerobic digestion effluent) was altered by autoclaving part of the effluent to study the effect of feedstock to active effluent ratio (F/Ea, 2.2-6.6) and the feedstock to total effluent ratio (F/Et, 2.2 and 4.4) on reactor performance in solid state anaerobic digestion (SS-AD) of corn stover. When the F/Ea ratio was increased from 2.2 to 6.6, methane yield was not significantly reduced; however, reactors became acidified when the F/Et ratio was increased from 2.2 to 4.4. It was concluded that F/Et had a greater effect on methane yields than F/Ea for the range studied in this paper. As analyzed by denaturing gradient gel electrophoresis using PCR amplified 16S rRNA genes, the microbial community underwent dynamic shifts under acidified conditions over 38days of SS-AD. These shifts reflected the acclimation, both adaptive selection and diversification, of the initial inoculated microbial consortia. PMID:24556372
Shi, Jian; Xu, Fuqing; Wang, Zhongjiang; Stiverson, Jill A; Yu, Zhongtang; Li, Yebo
Digest Your Food!
In a multi-week experiment, student teams gather biogas data from the mini-anaerobic digesters that they build to break down different types of food waste with microbes. Using plastic soda bottles for the mini-anaerobic digesters and gas measurement devices, they compare methane gas production from decomposing hot dogs, diced vs. whole. They monitor and measure the gas production, then graph and analyze the collected data. Students learn how anaerobic digestion can be used to biorecycle waste (food, poop or yard waste) into valuable resources (nutrients, biogas, energy).
Membrane Biotechnology Laboratory
Commissioning of the gigantic anaerobic sludge digesters at the wastewater treatment plant of Athens.
The pre-commissioning strategy, the start-up procedure and the analytical data obtained during the commissioning period for the first of the four new anaerobic gigantic digesters, with active volume of 10,000 m3 each, are presented in this paper. The digester was initially filled up with water, and the temperature was raised to 36 +/- 1 degrees C. Then, a total amount of 1,860 m3 of digested primary sludge was transferred, in four equal daily batches, into the digester from neighbouring digesters, performing routine operation. Following this, the digester was gradually fed with fresh primary thickened sludge, up to the point that the retention time reached approximately 20 d. A number of significant operational parameters (pH, alkalinity, total and volatile solids concentration, volatile fatty acids concentration, biogas production rate and composition) were monitored several times per day, and the appropriate adjustments were performed in order to achieve stable operation. The time duration of the whole process was about two and a half months. Later on, the digester was supplied with a mixture of primary and biological sludge. PMID:18613612
Gikas, P
Inactivation of Ascaris suum and poliovirus in biosolids under thermophilic anaerobic digestion conditions.
There is considerable interest in the United States in production of Class A (low pathogen content) biosolids from the treatment of municipal wastewater sludge. Current requirements imposed by the U.S. Environmental Protection Agency make it difficult for thermophilic anaerobic digestion, in its simplest process configurations, to achieve Class A status. In particular, the time-temperature requirements necessitate long batch treatment times at temperatures associated with thermophilic anaerobic digestion. The time-temperature requirements are meant to ensure extensive inactivation of helminth eggs and enteric viruses, considered to be the most heat-resistant of the relevant pathogen classes. However, data on inactivation kinetics of these pathogens at precisely controlled and well-characterized temperatures are scarce. We measured inactivation of vaccine-strain poliovirus and eggs from the helminth Ascaris suum at temperatures from 49 to 55 degrees C in a lab-scale batch reactor containing biosolids from a continuous-flow thermophilic anaerobic digester. Both microbes were inactivated rapidly, with Ascaris more resistant to inactivation than poliovirus, and the relationships between inactivation rate and temperature were steep. The Arrhenius correlation between inactivation rate and temperature over the range 49-53 degrees C is consistent with protein denaturation as the inactivation mechanism for both microbes. The least stringent of the EPA time-temperature equations for thermal processes requires batch treatment times more than 2 orders of magnitude greater than would be required for three-log reduction of Ascaris at the rates we measured, suggesting an overly conservative regulatory approach. Such a grossly conservative approach can hinder full-scale implementation of thermophilic anaerobic digestion. PMID:16124318
Aitken, Michael D; Sobsey, Mark D; Blauth, Kimberly E; Shehee, Mina; Crunk, Phillip L; Walters, Glenn W
Designs of anaerobic digesters for producing biogas from municipal solid-waste
The production of biogas is of growing interest as fossil-fuel reserves decline. However, there exists a dearth of literature on the design considerations that would lead to process optimization in the development of anaerobic digesters aimed at creating useful commodities from the ever-abundant municipal solid-waste. Consequently, this paper provides a synthesis of the key issues and analyses concerning the design
A. Hilkiah Igoni; M. J. Ayotamuno; C. L. Eze; S. O. T. Ogaji; S. D. Probert
Inactivation of virus during anaerobic digestion of manure in laboratory scale biogas reactors
Reduction of porcine parvovirus, bovine enterovirus and faecal enterococci were measured in biogas reactors continuously run\\u000a on manure and manure supplemented with household waste at 35�C and 55�C and in batch test run at 70�C. The aim of the experiments\\u000a was to study the sanitation effect of anaerobic digestion and to evaluate the use of faecal enterococci as an indicator
Bente Lund; Vibeke Fr�kj�r Jensen; Per Have; Birgitte Ahring
Nutrient removal by floating aquatic macrophytes cultured in anaerobically digested flushed dairy manure wastewater
The potential of three floating aquatic macrophytes to improve the water quality of anaerobically digested flushed dairy manure wastewater (ADFDMW) was evaluated. In undiluted ADFDMW (total chemical oxygen demand 2010mg\\/l), growth of water hyacinth (Eichhornia crassipes) was inhibited and both pennywort (Hydrocotyle umbellata) and water lettuce (Pistia stratiotes) failed to grow. In a 1:1 dilution of ADFDMW, all three plants
Reeta D. Sooknah; Ann C. Wilkie
Kinetic analysis of the anaerobic digestion of untreated vinasses and vinasses previously treated with Penicillium decumbens
A kinetic study was carried out on the anaerobic digestion of untreated vinasses and vinasses previously fermented with Penicillium decumbens. Two 1-l volume continuous-flow stirred tank reactors (CFSTR) operating at mesophilic temperature (35�C) were used for the study. One reactor was fed with untreated vinasses (COD concentration of 80.5g\\/l) and the other with vinasses previously fermented (COD concentration of 23.0g\\/l).
A. M. Jim�nez; R. Borja; A. Mart�n; F. Raposo
Mesophilic and thermophilic anaerobic digestion with thermophilic pre-acidification of instant-coffee-production wastewater
The thermophilic and mesophilic digestion of instant-coffee-production wastewater in upflow anaerobic sludge blanket (UASB) reactors with thermophilic pre-acidification was studied over a period of more than 120 days. The UASB reactors had been seeded with granules adapted to this wastewater, and they previously operated in single-stage mode mesophilically or thermophilically. The thermophilic pre-acidification stage was operated with pH control or
Richard M. Dinsdale; Freda R. Hawkes; Dennis L. Hawkes
Removal of heavy metals from anaerobically digested sewage sludge by isolated indigenous iron-oxidizing bacteria
The removal of heavy metals (Cr, Cu, Zn, Ni and Pb) from anaerobically digested sludge from the Yuen Long wastewater treatment plant, Hong Kong, has been studied in a batch system using isolated indigenous iron-oxidizing bacteria. The inoculation of indigenous iron-oxidizing bacteria and the addition of FeSO4 accelerated the solubilization of Cr, Cu, Zn, Ni and Pb from the sludge.
L Xiang; L. C Chan; J. W. C Wong
Escherichia coli inactivation kinetics in anaerobic digestion of dairy manure under moderate, mesophilic and thermophilic temperatures.
Batch anaerobic digestion experiments using dairy manure as feedstocks were performed at moderate (25�C), mesophilic (37�C), and thermophilic (52.5�C) temperatures to understand E. coli, an indicator organism for pathogens, inactivation in dairy manure. Incubation periods at 25, 37, and 52.5�C, were 61, 41, and 28 days respectively. Results were used to develop models for predicting E. coli inactivation and survival in anaerobic digestion. For modeling we used the decay of E. coli at each temperature to calculate the first-order inactivation rate coefficients, and these rates were used to formulate the time - temperature - E. coli survival relationships. We found the inactivation rate coefficient at 52.5�C was 17 and 15 times larger than the inactivation rate coefficients at 25 and 37�C, respectively. Decimal reduction times (D10; time to achieve one log removal) at 25, 37, and 52.5�C, were 9 -10, 7 - 8 days, and < 1 day, respectively. The Arrhenius correlation between inactivation rate coefficients and temperatures over the range 25 -52.5�C was developed to understand the impacts of temperature on E. coli inactivation rate. Using this correlation, the time - temperature - E. coli survival relationships were derived. Besides E. coli inactivation, impacts of temperature on biogas production, methane content, pH change, ORP, and solid reduction were also studied. At higher temperatures, biogas production and methane content was greater than that at low temperatures. While at thermophilic temperature pH was increased, at mesophilic and moderate temperatures pH were reduced over the incubation period. These results can be used to understand pathogen inactivation during anaerobic digestion of dairy manure, and impacts of temperatures on performance of anaerobic digesters treating dairy manure. PMID:21906374
Pandey, Pramod K; Soupir, Michelle L
Effect of natural zeolite on methane production for anaerobic digestion of ammonium rich organic sludge
The effect of an inorganic additive on the methane production from NH4+-rich organic sludge during anaerobic digestion was investigated using different kinds of inorganic adsorbent zeolites (mordenite, clinoptilolite, zeolite 3A, zeolite 4A), clay mineral (vermiculite), and manganese oxides (hollandite, birnessite). The additions of inorganic materials resulted in significant NH4+ removals from the natural organic sludge ([NH4+]=1, 150 mgN\\/l), except for
Chika Tada; Yingnan Yang; Toshiaki Hanaoka; Akinari Sonoda; Kenta Ooi; Shigeki Sawayama
Agricultural potential of anaerobically digested industrial orange waste with and without aerobic post-treatment
The potential of anaerobically digested orange waste with (AAD) and without (AD) aerobic post-treatment for use in agriculture was evaluated through chemical analyses, short-term phytotoxicity and long-term plant assays. Chemical analyses showed that AD contained ammonia and organic acids, and aerobic post-treatment did not significantly remove these phytotoxins. The N:P2O5:K2O ratio in AD was 1:0.26:0.96 and aerobic post-treatment did not
Prasad Kaparaju; Jukka Rintala; Aimo Oikari
Mechanism of inhibition caused by long-chain fatty acids in anaerobic digestion process
The inhibitory effect of long-chain fatty acids on the anaerobic digestion process was examined in batch experiments using synthetic substrates. The addition of long-chain fatty acids caused the appearance of the lag period in the methane production from acetate and in the degradation of both long-chain fatty acids and n-butyrate. Methane production from hydrogen proceeded without lag period although its
Keisuke Hanaki; Tomonori Matsuo; Michihiko Nagase
Effects of lipids on thermophilic anaerobic digestion and reduction of lipid inhibition upon addition of bentonite
The effect of bentonite-bound oil on thermophilic anaerobic digestion of cattle manure was investigated. In digestor experiments, addition of oil was found to be inhibitory during start-up and the inhibitory effect was less pronounced when the oil was added in the form of bentonite-bound oil compared to when the oil was added alone. After adaption of the digestors, very rapid
I. Angelidaki; S. P. Petersen; B. K. Ahring
Increasing biogas production by thermal (70 �C) sludge pre-treatment prior to thermophilic anaerobic digestion
The objective of this work was to investigate the effect of a low temperature pre-treatment (70�C) on the efficiency of thermophilic anaerobic digestion of primary and secondary waste sludge. Firstly, effect of sludge pre-treatment time (9, 24, 48 and 72h) was evaluated by the increase in volatile dissolved solids (VDSs), volatile fatty acids (VFAs) and biogas production in thermophilic batch
Ivet Ferrer; Sergio Pons�; Fel�citas V�zquez
Peroxidation enhances the biogas production in the anaerobic digestion of biosolids
During the anaerobic digestion of wastewater treatment sludge, commonly called biosolids, an energy rich biogas is formed which is now considered as renewable energy source and widely used for the production of heat and\\/or electricity. Pre-treatment methods, which achieve a transformation of refractory COD into readily available and soluble BOD, have the potential to enhance the biogas-production. This paper studies
Raf Dewil; Lise Appels; Jan Baeyens; Jan Degr�ve
Feasibility of biohydrogen production by anaerobic co-digestion of food waste and sewage sludge
Anaerobic co-digestion of food waste and sewage sludge for hydrogen production was performed in serum bottles under various volatile solids (VS) concentrations (0.5�5.0%) and mixing ratios of two substrates (0:100�100:0, VS basis). Through response surface methodology, empirical equations for hydrogen evolution were obtained. The specific hydrogen production potential of food waste was higher than that of sewage sludge. However, hydrogen
Sang-Hyoun Kim; Sun-Kee Han; Hang-Sik Shin
Escherichia coli inactivation kinetics in anaerobic digestion of dairy manure under moderate, mesophilic and thermophilic temperatures
Batch anaerobic digestion experiments using dairy manure as feedstocks were performed at moderate (25�C), mesophilic (37�C), and thermophilic (52.5�C) temperatures to understand E. coli, an indicator organism for pathogens, inactivation in dairy manure. Incubation periods at 25, 37, and 52.5�C, were 61, 41, and 28 days respectively. Results were used to develop models for predicting E. coli inactivation and survival in anaerobic digestion. For modeling we used the decay of E. coli at each temperature to calculate the first-order inactivation rate coefficients, and these rates were used to formulate the time - temperature - E. coli survival relationships. We found the inactivation rate coefficient at 52.5�C was 17 and 15 times larger than the inactivation rate coefficients at 25 and 37�C, respectively. Decimal reduction times (D10; time to achieve one log removal) at 25, 37, and 52.5�C, were 9 -10, 7 - 8 days, and < 1 day, respectively. The Arrhenius correlation between inactivation rate coefficients and temperatures over the range 25 -52.5�C was developed to understand the impacts of temperature on E. coli inactivation rate. Using this correlation, the time - temperature - E. coli survival relationships were derived. Besides E. coli inactivation, impacts of temperature on biogas production, methane content, pH change, ORP, and solid reduction were also studied. At higher temperatures, biogas production and methane content was greater than that at low temperatures. While at thermophilic temperature pH was increased, at mesophilic and moderate temperatures pH were reduced over the incubation period. These results can be used to understand pathogen inactivation during anaerobic digestion of dairy manure, and impacts of temperatures on performance of anaerobic digesters treating dairy manure.
Zinc and copper distribution in swine wastewater treated by anaerobic digestion.
Swine wastewater contain high levels of metals, such as copper and zinc, which can cause a negative impact on the environment. Anaerobic digestion is a process commonly used to remove carbon, and can act on metal availability (e.g., solubility or oxidation state). The present study aimed to evaluate the influence of anaerobic digestion on total Zn and Cu contents, and their chemical fractioning due to the biodegradation of the effluent over different hydraulic retention times (HRTs). The sequential extraction protocol proposed by the Community Bureau of Reference (BCR), plus two additional fractions, was the method chosen for this study of Cu and Zn distribution evaluation in swine wastewater. The Zn and Cu concentrations in raw swine manure were 63.58���27.72�mg�L(-1) and 8.98���3.99�mg�L(-1), respectively. The metal retention capacity of the bioreactor decreased when the HRT was reduced from 17.86�d to 5.32�d. Anaerobic digestion had a direct influence on zinc and copper distribution when raw manure (RM) and digested manure (DM) were compared. The reducible fraction showed a reduction of between 3.17% and 7.84% for Zn and between 2.52% and 11.92% for Cu when DM was compared with RM. However, the metal concentration increased in the oxidizable fraction of DM, viz. from 3.01% to 10.64% for Zn and from 4.49% to 16.71% for Cu, thus demonstrating the effect of anaerobic conditions on metal availability. PMID:24794386
Cestonaro do Amaral, Andr�; Kunz, Airton; Radis Steinmetz, Ricardo Lu�s; Justi, Karin Cristiane
A methodology for optimising feed composition for anaerobic co-digestion of agro-industrial wastes
An optimisation protocol for maximising methane production by anaerobic co-digestion of several wastes was carried out. A linear programming method was utilised to set up different blends aimed at maximising the total substrate biodegradation potential (L CH4\\/kg substrate) or the biokinetic potential (L CH4\\/kg substrate d). In order to validate the process, three agro-industrial wastes were considered: pig manure, tuna
J. A. �lvarez; L. Otero; J. M. Lema
Do anaerobic digestates promote dispersion, acidification and water repellency in soils?
Digestates are used as organic fertilizer on agricultural land due to their high amounts of nutrients (e.g. potassium, sodium). It is commonly expected that the application of sludge derived from anaerobic digestion can influence the soil structure and soil stability. Due to the fact that digestates contain large quantities of monovalent salts and long-chained fatty acids, the consequence of sludge amendment can be soil degradation caused by acidification, dispersion and increased water-repellency. Thus, water infiltration can be impeded which results in a preservation of stable soil aggregates. However, a diminished water infiltration can support water erosion and preferential flow of easy soluble nutrients into the groundwater. Our research was conducted with different digestates derived from maize, wheat and sugar beet to examine occurring processes in soils of two different textures after the application of anaerobic sludges. Particularly, we focused on the wetting properties of the soil. For this purpose, the wetting behavior was investigated by determining the sorptivity-based Repellency Index with moist samples and the contact angle with homogenized, air-dried soil material. Further surveys were carried out to assess the flow behavior of digestates application and the deformation of the particle-to-particle association by microscaled shearing. Additionally, the acidification process in the soil as a result of sludge application was investigated. To account for the dispersive impact of digestates, the turbidity of soil suspensions was ascertained. We summarize from the results that the digestates have a clear impact on the water repellency of the soil. We recognized a shift to more hydrophobic conditions. Partially, the pH remains on a high level due to the alkaline digestate, but several samples show a decline of pH, depending on the soil texture, respectively. However, soil structure was weakened as was shown by an increase of turbidity. As a conclusion, we point out the necessity to take into account the impact which anaerobic digestates might have on soil structure and stability in addition to their fertilizing effect to sustain the soil in a good state.
Voelkner, Amrei; Holthusen, D�rthe; Horn, Rainer
Effect of Increasing Total Solids Contents on Anaerobic Digestion of Food Waste under Mesophilic Conditions: Performance and Microbial Characteristics Analysis.
The total solids content of feedstocks affects the performances of anaerobic digestion and the change of total solids content will lead the change of microbial morphology in systems. In order to increase the efficiency of anaerobic digestion, it is necessary to understand the role of the total solids content on the behavior of the microbial communities involved in anaerobic digestion of organic matter from wet to dry technology. The performances of mesophilic anaerobic digestion of food waste with different total solids contents from 5% to 20% were compared and the microbial communities in reactors were investigated using 454 pyrosequencing technology. Three stable anaerobic digestion processes were achieved for food waste biodegradation and methane generation. Better performances mainly including volatile solids reduction and methane yield were obtained in the reactors with higher total solids content. Pyrosequencing results revealed significant shifts in bacterial community with increasing total solids contents. The proportion of phylum Chloroflexi decreased obviously with increasing total solids contents while other functional bacteria showed increasing trend. Methanosarcina absolutely dominated in archaeal communities in three reactors and the relative abundance of this group showed increasing trend with increasing total solids contents. These results revealed the effects of the total solids content on the performance parameters and the behavior of the microbial communities involved in the anaerobic digestion of food waste from wet to dry technologies. PMID:25051352
Yi, Jing; Dong, Bin; Jin, Jingwei; Dai, Xiaohu
Effect of Increasing Total Solids Contents on Anaerobic Digestion of Food Waste under Mesophilic Conditions: Performance and Microbial Characteristics Analysis
The total solids content of feedstocks affects the performances of anaerobic digestion and the change of total solids content will lead the change of microbial morphology in systems. In order to increase the efficiency of anaerobic digestion, it is necessary to understand the role of the total solids content on the behavior of the microbial communities involved in anaerobic digestion of organic matter from wet to dry technology. The performances of mesophilic anaerobic digestion of food waste with different total solids contents from 5% to 20% were compared and the microbial communities in reactors were investigated using 454 pyrosequencing technology. Three stable anaerobic digestion processes were achieved for food waste biodegradation and methane generation. Better performances mainly including volatile solids reduction and methane yield were obtained in the reactors with higher total solids content. Pyrosequencing results revealed significant shifts in bacterial community with increasing total solids contents. The proportion of phylum Chloroflexi decreased obviously with increasing total solids contents while other functional bacteria showed increasing trend. Methanosarcina absolutely dominated in archaeal communities in three reactors and the relative abundance of this group showed increasing trend with increasing total solids contents. These results revealed the effects of the total solids content on the performance parameters and the behavior of the microbial communities involved in the anaerobic digestion of food waste from wet to dry technologies.
Jin, Jingwei; Dai, Xiaohu
Pig slurry concentration by vacuum evaporation: influence of previous mesophilic anaerobic digestion process.
Water can be removed from pig slurry by evaporation, through the application of wasted heat from a power plant or from other processes. Apart from obtaining a concentrate with an obviously higher nutrient concentration than the original slurry, another objective of water removal is to obtain water as condensate, which could be reused. The objective of this work was to study the vacuum evaporation of pig slurry liquid fraction and to evaluate condensate composition as a function of both pH (4, 5, and 6) and pig slurry type (fresh slurry and anaerobically digested slurry). Batch experiments showed that condensate characteristics, total ammonia nitrogen (NH3-N), volatile fatty acids (VFA), and chemical oxygen demand were strongly dependent on initial slurry pH. In addition to producing part of the required thermal energy, previous anaerobic digestion presented several other clear advantages. The consumption of VFA and other volatile organic compounds during anaerobic digestion reduced the volatilization of organic matter in the evaporation treatment and, consequently, provided a higher quality condensate. PMID:12568250
Bonmat�, August; Flotats, Xavier
Anaerobic co-digestion of aquatic flora and quinoa with manures from Bolivian Altiplano
Quinoa stalk (Chenopodium quinoa Willd.) from agricultural crop residue, totora (Schoenoplectus tatora) and o-macrophytes (aquatic flora) from Lake Titicaca (on the Bolivian Altiplano) were studied in a wet anaerobic co-digestion process together with manure from llama, cow and sheep. Anaerobic semi-continuous experiments were performed in (10) 2-l reactors at a temperature of 25 deg. C with 30 days of hydraulic retention time (HRT) and an organic loading rate (OLR) of 1.8 kg VS m{sup -3} d{sup -1}. Totora was found to be the best co-substrate. In mixture ratios of 1:1 (VS basis), it increased the biogas productivity by 130% for llama manure, 60% for cow manure, and 40% for sheep manure. It was possible to use up to 58% (VS basis) of totora in the substrate. Higher concentrations (including pure totora) could not be digested, as that caused acidification problems similar to those caused by other lignocellulosic materials. When quinoa and o-macrophytes were used as co-substrates, the increase in biogas productivity was slightly less. However, these co-substrates did not cause any operational problems. An additional advantage of quinoa and o-macrophytes was that they could be used in any proportion (even in pure form) without causing any destabilization problems in the anaerobic digestion process.
Alvarez, Rene [IIDEPROQ, UMSA, Plaza del Obelisco 1175, La Paz (Bolivia)], E-mail: email@example.com; Liden, Gunnar [Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00 Lund (Sweden)
Anaerobic co-digestion of aquatic flora and quinoa with manures from Bolivian Altiplano.
Quinoa stalk (Chenopodium quinoa Willd.) from agricultural crop residue, totora (Schoenoplectus tatora) and o-macrophytes (aquatic flora) from Lake Titicaca (on the Bolivian Altiplano) were studied in a wet anaerobic co-digestion process together with manure from llama, cow and sheep. Anaerobic semi-continuous experiments were performed in (10) 2-l reactors at a temperature of 25 degrees C with 30 days of hydraulic retention time (HRT) and an organic loading rate (OLR) of 1.8 kg VS m(-3) d(-1). Totora was found to be the best co-substrate. In mixture ratios of 1:1 (VS basis), it increased the biogas productivity by 130% for llama manure, 60% for cow manure, and 40% for sheep manure. It was possible to use up to 58% (VS basis) of totora in the substrate. Higher concentrations (including pure totora) could not be digested, as that caused acidification problems similar to those caused by other lignocellulosic materials. When quinoa and o-macrophytes were used as co-substrates, the increase in biogas productivity was slightly less. However, these co-substrates did not cause any operational problems. An additional advantage of quinoa and o-macrophytes was that they could be used in any proportion (even in pure form) without causing any destabilization problems in the anaerobic digestion process. PMID:18155895
Alvarez, Ren�; Lid�n, Gunnar
Changes of heavy metal speciation during high-solid anaerobic digestion of sewage sludge.
The sequential extraction procedure developed by Tessier et al. was used in sludge anaerobic digestion to determine the heavy metal speciation. Sludge samples were taken every three days to investigate humic substances, VS/TS, pH, VFA, alkalinity, ammonia, the total content of Zn, Pb, Cu, Ni, and Cr, and also their distribution into EXCH, CARB, FeMnOx, OMB and RESI fractions. Results showed that, (1) Heavy metals were concentrated during the anaerobic digestion process. The concentration of all five kinds of heavy metals increased by about 50%. (2) The distribution of these heavy metals differed. (3) High-solid anaerobic digestion much or less increased the bioavailability of Cu, Zn, Ni and Cr while decreased the bioavailability of Pb. (4) There were significant degrees of correlation between heavy metal fractions and changes of some selected parameters (for example, pH, VS/TS, and VFA content). Except for Pb, the contents of total mobile fractions for Cu, Zn, Ni, Cr could be predictable from its total content. PMID:23347922
Dong, Bin; Liu, Xiaoguang; Dai, Lingling; Dai, Xiaohu
A novel process simulation model (PSM) for anaerobic digestion using Aspen Plus.
A novel process simulation model (PSM) was developed for biogas production in anaerobic digesters using Aspen Plus�. The PSM is a library model of anaerobic digestion, which predicts the biogas production from any substrate at any given process condition. A total of 46 reactions were used in the model, which include inhibitions, rate-kinetics, pH, ammonia, volume, loading rate, and retention time. The hydrolysis reactions were based on the extent of the reaction, while the acidogenic, acetogenic, and methanogenic reactions were based on the kinetics. The PSM was validated against a variety of lab and industrial data on anaerobic digestion. The P-value after statistical analysis was found to be 0.701, which showed that there was no significant difference between discrete validations and processing conditions. The sensitivity analysis for a �10% change in composition of substrate and extent of reaction results in 5.285% higher value than the experimental value. The model is available at http://hdl.handle.net/2320/12358 (Rajendran et al., 2013b). PMID:24524857
Rajendran, Karthik; Kankanala, Harshavardhan R; Lundin, Magnus; Taherzadeh, Mohammad J
Implications of urine-to-feces ratio in the thermophilic anaerobic digestion of swine waste.
Thermophilic anaerobic digestion of swine manure represents a potential waste treatment technology to address environmental concerns, such as odor emissions and removal of pathogenic microorganisms. However, there are concerns relative to the stability of this process when swine manure is the sole substrate. In this study, the potential of biogas production from swine manure as the sole substrate under thermophilic (50 degrees C) conditions was investigated in the laboratory, to determine whether separation of urine and feces as part of the waste collection process would benefit anaerobic digestion. Effluent from a continuously stirred tank reactor was used as the inoculum for batch tests, in which the substrate contained three different concentrations of urine (urine-free, as-excreted urine-to-feces ratio and double the as-excreted urine-to-feces ratio). Inocula were acclimated to these same urine-to-feces ratios to determine methane production. Results show that both urine-free and as-excreted substrates were not inhibitory to anaerobic inocula. Anaerobic microorganisms can be readily acclimated to substrate with double the as-excreted urine concentration, which contained nitrogen concentrations up to 7.20 g/L. Cumulative methane production reached similar levels in the batch tests, regardless of the substrate urine concentration. PMID:18419015
Creamer, K S; Williams, C M; Chen, Y; Cheng, J J
Recent development of anaerobic digestion processes for energy recovery from wastes.
Anaerobic digestion leads to the overall gasification of organic wastewaters and wastes, and produces methane and carbon dioxide; this gasification contributes to reducing organic matter and recovering energy from organic carbons. Here, we propose three new processes and demonstrate the effectiveness of each process. By using complete anaerobic organic matter removal process (CARP), in which diluted wastewaters such as sewage and effluent from a methane fermentation digester were treated under anaerobic condition for post-treatment, the chemical oxygen demand (COD) in wastewater was decreased to less than 20 ppm. The dry ammonia-methane two-stage fermentation process (Am-Met process) is useful for the anaerobic treatment of nitrogen-rich wastes such as waste excess sludge, cow feces, chicken feces, and food waste without the dilution of the ammonia produced by water or carbon-rich wastes. The hydrogen-methane two-stage fermentation (Hy-Met process), in which the hydrogen produced in the first stage is used for a fuel cell system to generate electricity and the methane produced in the second stage is used to generate heat energy to heat the two reactors and satisfy heat requirements, is useful for the treatment of sugar-rich wastewaters, bread wastes, and biodiesel wastewaters. PMID:17368391
Nishio, Naomichi; Nakashimada, Yutaka
Performance evaluation of an anaerobic/aerobic landfill-based digester using yard waste for energy and compost production
Highlights: Black-Right-Pointing-Pointer Biochemical methane potential decreased by 83% during the two-stage operation. Black-Right-Pointing-Pointer Net energy produced was 84.3 MWh or 46 kWh per million metric tons (Mg). Black-Right-Pointing-Pointer The average removal efficiency of volatile organic compounds (VOCs) was 96-99%. Black-Right-Pointing-Pointer The average removal efficiency of non-methane organic compounds (NMOCs) was 68-99%. Black-Right-Pointing-Pointer The two-stage batch digester proved to be simple to operate and cost-effective. - Abstract: The objective of this study was to evaluate a new alternative for yard waste management by constructing, operating and monitoring a landfill-based two-stage batch digester (anaerobic/aerobic) with the recovery of energy and compost. The system was initially operated under anaerobic conditions for 366 days, after which the yard waste was aerated for an additional 191 days. Off gas generated from the aerobic stage was treated by biofilters. Net energy recovery was 84.3 MWh, or 46 kWh per million metric tons of wet waste (as received), and the biochemical methane potential of the treated waste decreased by 83% during the two-stage operation. The average removal efficiencies of volatile organic compounds and non-methane organic compounds in the biofilters were 96-99% and 68-99%, respectively.
Yazdani, Ramin, E-mail: firstname.lastname@example.com [Yolo County Planning and Public Works Department, Division of Integrated Waste Management, Woodland, CA 95776 (United States); Civil and Environmental Engineering, University of California, One Shields Avenue, Ghausi Hall, Davis, CA 95616 (United States); Barlaz, Morton A., E-mail: email@example.com [Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Augenstein, Don, E-mail: firstname.lastname@example.com [Institute for Environmental Management, Inc., Palo Alto, CA 94306 (United States); Kayhanian, Masoud, E-mail: firstname.lastname@example.com [Civil and Environmental Engineering, University of California, One Shields Avenue, Ghausi Hall, Davis, CA 95616 (United States); Tchobanoglous, George, E-mail: email@example.com [Civil and Environmental Engineering, University of California, One Shields Avenue, Ghausi Hall, Davis, CA 95616 (United States)
Gas-phase separations of protease digests
A mixture of peptides from a complete tryptic digest of ubiquitin has been analyzed by ion mobility\\/time-of-flight mass spectrometry\\u000a techniques. All components of the mixture were electrosprayed and ions were separated in the gas phase based on differences\\u000a in their mobilities through helium before being dispersed into a time-of-flight mass spectrometer for mass-to-charge analysis.\\u000a The data show that ions separate
Stephen J. Valentine; Anne E. Counterman; Cherokee S. Hoaglund; James P. Reilly; David E. Clemmer
Implementation of an UASB anaerobic digester at bagasse-based pulp and paper industry
Upflow anaerobic sludge blanket (UASB) reactor was installed to replace the conventional anaerobic lagoon treating bagasse wash wastewater from agro-based pulp and paper mill, to generate bio-energy and to reduce greenhouse gas emissions. The plant was designed to treat 12MLd?1 of wastewater having two 5ML capacity reactors, 5.75kgCODm?3d?1 organic loading rate and 20h hydraulic retention time. In the plant 80�85%
S. Chinnaraj; G. Venkoba Rao
Development of a pilot scale anaerobic digester for biogas production from cow manure and whey mix.
This paper presents results from anaerobic digestion of cow manure and whey mix. A pilot scale anaerobic digester, 128 l in volume, has been developed, to operate under batch and fed-batch conditions. The versatile and unique characteristics of the instrument allowed testing the methane production directly in the farm. The digester performance was evaluated with two calibration tests, the main for a period of 56 days. The study test was divided into three phases, one for each type of feeding operation (batch, fed-batch, batch). The initial phase of digestion resulted in 57 l-CH(4)/kg-VS, the second phase had a yield of 86.6 l-CH(4)/kg-VS and the third one had a production of 67 l-CH(4)/kg-VS. The total methane yield was equal to 211.4 l-CH(4)/kg-VS. Using the obtained pilot plant results to a real scale diary production cycle, it was possible to evaluate an electricity production equal to 8.86 kwh per 1 t/d. The conducted tests did show that there is a good potential to the use of a cow manure and whey biomass mix for biogas production. PMID:19559606
Comino, Elena; Rosso, Maurizio; Riggio, Vincenzo
Continuously-stirred anaerobic digester to convert organic wastes into biogas: system setup and basic operation.
Anaerobic digestion (AD) is a bioprocess that is commonly used to convert complex organic wastes into a useful biogas with methane as the energy carrier. Increasingly, AD is being used in industrial, agricultural, and municipal waste(water) treatment applications. The use of AD technology allows plant operators to reduce waste disposal costs and offset energy utility expenses. In addition to treating organic wastes, energy crops are being converted into the energy carrier methane. As the application of AD technology broadens for the treatment of new substrates and co-substrate mixtures, so does the demand for a reliable testing methodology at the pilot- and laboratory-scale. Anaerobic digestion systems have a variety of configurations, including the continuously stirred tank reactor (CSTR), plug flow (PF), and anaerobic sequencing batch reactor (ASBR) configurations. The CSTR is frequently used in research due to its simplicity in design and operation, but also for its advantages in experimentation. Compared to other configurations, the CSTR provides greater uniformity of system parameters, such as temperature, mixing, chemical concentration, and substrate concentration. Ultimately, when designing a full-scale reactor, the optimum reactor configuration will depend on the character of a given substrate among many other nontechnical considerations. However, all configurations share fundamental design features and operating parameters that render the CSTR appropriate for most preliminary assessments. If researchers and engineers use an influent stream with relatively high concentrations of solids, then lab-scale bioreactor configurations cannot be fed continuously due to plugging problems of lab-scale pumps with solids or settling of solids in tubing. For that scenario with continuous mixing requirements, lab-scale bioreactors are fed periodically and we refer to such configurations as continuously stirred anaerobic digesters (CSADs). This article presents a general methodology for constructing, inoculating, operating, and monitoring a CSAD system for the purpose of testing the suitability of a given organic substrate for long-term anaerobic digestion. The construction section of this article will cover building the lab-scale reactor system. The inoculation section will explain how to create an anaerobic environment suitable for seeding with an active methanogenic inoculum. The operating section will cover operation, maintenance, and troubleshooting. The monitoring section will introduce testing protocols using standard analyses. The use of these measures is necessary for reliable experimental assessments of substrate suitability for AD. This protocol should provide greater protection against a common mistake made in AD studies, which is to conclude that reactor failure was caused by the substrate in use, when really it was improper user operation. PMID:22824993
Usack, Joseph G; Spirito, Catherine M; Angenent, Largus T
Continuously-stirred Anaerobic Digester to Convert Organic Wastes into Biogas: System Setup and Basic Operation
Anaerobic digestion (AD) is a bioprocess that is commonly used to convert complex organic wastes into a useful biogas with methane as the energy carrier 1-3. Increasingly, AD is being used in industrial, agricultural, and municipal waste(water) treatment applications 4,5. The use of AD technology allows plant operators to reduce waste disposal costs and offset energy utility expenses. In addition to treating organic wastes, energy crops are being converted into the energy carrier methane 6,7. As the application of AD technology broadens for the treatment of new substrates and co-substrate mixtures 8, so does the demand for a reliable testing methodology at the pilot- and laboratory-scale. Anaerobic digestion systems have a variety of configurations, including the continuously stirred tank reactor (CSTR), plug flow (PF), and anaerobic sequencing batch reactor (ASBR) configurations 9. The CSTR is frequently used in research due to its simplicity in design and operation, but also for its advantages in experimentation. Compared to other configurations, the CSTR provides greater uniformity of system parameters, such as temperature, mixing, chemical concentration, and substrate concentration. Ultimately, when designing a full-scale reactor, the optimum reactor configuration will depend on the character of a given substrate among many other nontechnical considerations. However, all configurations share fundamental design features and operating parameters that render the CSTR appropriate for most preliminary assessments. If researchers and engineers use an influent stream with relatively high concentrations of solids, then lab-scale bioreactor configurations cannot be fed continuously due to plugging problems of lab-scale pumps with solids or settling of solids in tubing. For that scenario with continuous mixing requirements, lab-scale bioreactors are fed periodically and we refer to such configurations as continuously stirred anaerobic digesters (CSADs). This article presents a general methodology for constructing, inoculating, operating, and monitoring a CSAD system for the purpose of testing the suitability of a given organic substrate for long-term anaerobic digestion. The construction section of this article will cover building the lab-scale reactor system. The inoculation section will explain how to create an anaerobic environment suitable for seeding with an active methanogenic inoculum. The operating section will cover operation, maintenance, and troubleshooting. The monitoring section will introduce testing protocols using standard analyses. The use of these measures is necessary for reliable experimental assessments of substrate suitability for AD. This protocol should provide greater protection against a common mistake made in AD studies, which is to conclude that reactor failure was caused by the substrate in use, when really it was improper user operation 10.
Usack, Joseph G.; Spirito, Catherine M.; Angenent, Largus T.
Anaerobic Granulation in Expanded Granular Sludge Bed (EGSB) Reactor Seeded with Digestion Sludge for Treatment of Actual Coking Wastewater
To obtain the rapid anaerobic granulation in expanded granular sludge bed (EGSB) reactor seeded with digestion sludge for treatment of actual coking wastewater, the rapid granulation using brewery wastewater and the quickly acclimation using coking wastewater of the EGSB reactor seeded with municipal digestion sludge and little granules were studied in this paper. The results indicated that the EGSB reactor
Chunjuan Dong; Fei An
The mesophilic-thermophilic digestion process is a new two-step concept for treating municipal wasterwater sludges. The first step operates under mesophilic process conditions (digestion with anaerobic microorganisms that thrive at 90 to 100F). The second step operates under ther...
Wastewater reclamation and methane production using water hyacinth and anaerobic digestion
Research reported here supports the conclusion that water hyacinth ponds are effective in the secondary treatment of domestic wastewater and under these conditions exhibited an average growth yield of 60 dry tons/ha-yr. However, treatment efficiencies and growth yields vary significantly in response to factors which include: (1) of nutrients in the pond influent; (2) residence times and water depth; (3) cultural techniques such as plant density and harvest frequency; (4) environmental conditions such as temperature, frost, etc.; and (5) insect infestation. These variables are under more intense study using smaller scale experiments. The results of these studies will be employed to determine optimum conditions for operation of the larger ponds. Work thus far completed on the anaerobic digestion of hyacinth and sludge has provided information on feed properties, feed biodegradabilities, digestion efficiencies under conventional digestion, nutritional balance, and the effects of blend constituents on methane yield and production rate. It is known that these feeds can be digested without external nutrient addition or pH control. The kinetics and efficiencies are comparable to those of other biomass or waste feeds; in fact, the yield from primary sludge is the highest we have seen reported for particulate feeds. Two conventional digester designs are currently exhibiting a significant increase in feed conversion to methane. Future laboratory research will continue to focus on advanced digestion and pretreatment for improvement of conversion efficiencies and net energy production. This will be complemented by operation of a larger scale experimental test unit.
Chynoweth, D.P.; Dolenc, D.A.; Schwegler, B.; Reddy, K.R.
Biokinetic and molecular studies of methanogens in phased anaerobic digestion systems.
The influence of differing operational conditions of two-stage digesters on biokinetic characteristics and communities of methanogenic archaea was evaluated. Operating temperature of each phase influenced the archaeal communities significantly. Also, a strong correlation was observed between community composition and temperature and pH. The maximum specific substrate utilization rates (k max) of acetoclastic methanogens in the mesophilic and thermophilic 1st phases were 11.4 and 22.0 mgCOD mgCOD(-1)d(-1), respectively, whereas significantly lower k max values were estimated for the mesophilic and thermophilic 2nd-phase digesters which were 7.6 and 16.6 mgCOD mgCOD(-1)d(-1), respectively. It appeared that the biokinetic characteristics of the acetoclastic methanogen communities were reliant on digester loading rates. Also, higher temperature dependency coefficients (?) were observed for the long retention time digesters when compared to the values computed for the 1st-phase digesters. Accordingly, the implementation of two sets of biokinetic parameters for acetoclastic methanogen will improve modeling of phased anaerobic digesters. PMID:24125797
Zamanzadeh, Mirzaman; Parker, Wayne J; Verastegui, Yris; Neufeld, Josh D
Forward osmosis for concentration of anaerobic digester centrate.
The nutrient-rich liquid stream produced during the dewatering of digested biomass (i.e., the centrate) is commonly mixed with the influent raw wastewater at wastewater treatment facilities. This increases the nitrogen and phosphorus loading on biological processes, increases operating costs, and in some cases, results in increased nutrient concentrations in the final effluent. Forward osmosis (FO) is a membrane treatment process that was investigated at bench scale to determine its feasibility to concentrate centrate under both batch and continuous operating conditions. The continuous bench-scale system used FO as pretreatment for reverse osmosis (RO). Results demonstrated that high water flux and high nutrient rejection could be achieved. The combined FO/RO process exhibited sustainable flux over an extended time period. A mathematical model was developed in order to determine the specific energy, power, and membrane area requirements for a larger-scale centrate treatment process. Modeling results indicated that to optimize power and membrane area requirements, the system should be operated at approximately 70% water recovery. PMID:17604810
Holloway, Ryan W; Childress, Amy E; Dennett, Keith E; Cath, Tzahi Y
Enhanced anaerobic treatment of CSTR-digested effluent from chicken manure: The effect of ammonia inhibition
Highlights: Black-Right-Pointing-Pointer Enhanced anaerobic treatment of CSTR-digested effluent from chicken manure. Black-Right-Pointing-Pointer The SCOD/TAN (soluble COD/total ammonia nitrogen) ratio was key controlling factor. Black-Right-Pointing-Pointer The threshold of the SCOD/TAN ratio was 2.4 at an influent pH of 8.5-9. - Abstract: The effect of ammonia inhibition was evaluated during the enhanced anaerobic treatment of digested effluent from a 700 m{sup 3} chicken-manure continuous stirred tank reactor (CSTR). A 12.3 L internal circulation (IC) reactor inoculated with an anaerobic granular sludge and operated at 35 {+-} 1 Degree-Sign C was employed for the investigation. With a corresponding organic loading rate of 1.5-3.5 kg-COD/m{sup 3} d over a hydraulic retention time of 1.5 d, a maximum volumetric biogas production rate of 1.2 m{sup 3}/m{sup 3} d and TCOD (total COD) removal efficiency ranging from 70% to 80% was achieved. However, the continual increase in the influent TAN content led to ammonia inhibition in the methanogenesis system. The SCOD/TAN (soluble COD/total ammonia nitrogen) ratio was presented to be the key controlling factor for the anaerobic treatment of semi-digested chicken manure, and further validation through shock loading and ammonia inhibition experiments was conducted. The threshold value of the SCOD/TAN ratio was determined to be 2.4 (corresponding to a TAN of 1250 mg/L) at an influent pH of 8.5-9.
Liu Zhanguang; Zhou Xuefei [Key Laboratory of Yangtze Water Environment of Ministry of Education, State Key Laboratory of Pollution and Resource Reuse, Tongji University, Shanghai 200092 (China); Zhang Yalei, E-mail: firstname.lastname@example.com [Key Laboratory of Yangtze Water Environment of Ministry of Education, State Key Laboratory of Pollution and Resource Reuse, Tongji University, Shanghai 200092 (China); Zhu Hongguang [Institute of Modern Agricultural Science and Engineering, National Engineering Research Center of Protected Agriculture, Tongji University, Shanghai 200092 (China)
Digestion of frozen/thawed food waste in the hybrid anaerobic solid-liquid system
The hybrid anaerobic solid-liquid (HASL) system, which is a modified two-phase anaerobic digester, is to be used in an industrial scale operation to minimize disposal of food waste at incineration plants in Singapore. The aim of the present research was to evaluate freezing/thawing of food waste as a pre-treatment for its anaerobic digestion in the HASL system. The hydrolytic and fermentation processes in the acidogenic reactor were enhanced when food waste was frozen for 24 h at -20 deg. C and then thawed for 12 h at 25 deg. C (experiment) in comparison with fresh food waste (control). The highest dissolved COD concentrations in the leachate from the acidogenic reactors were 16.9 g/l on day 3 in the control and 18.9 g/l on day 1 in the experiment. The highest VFA concentrations in the leachate from the acidogenic reactors were 11.7 g/l on day 3 in the control and 17.0 g/l on day 1 in the experiment. The same volume of methane was produced during 12 days in the control and 7 days in the experiment. It gave the opportunity to diminish operational time of batch process by 42%. The effect of freezing/thawing of food waste as pre-treatment for its anaerobic digestion in the HASL system was comparable with that of thermal pre-treatment of food waste at 150 deg. C for 1 h. However, estimation of energy required either to heat the suspended food waste to 150 deg. C or to freeze the same quantity of food waste to -20 deg. C showed that freezing pre-treatment consumes about 3 times less energy than thermal pre-treatment.
Stabnikova, O. [School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)], E-mail: email@example.com; Liu, X.Y.; Wang, J.Y. [School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)
Aspetti economici della digestione anaerobica nell'agroindustria: Applicazione di una nuova tecnologia in una distilleria. (Agro-industrial anaerobic digestion cost benefits: Technology utilization in distillery).
Anaerobic digestion, followed by aerobic post treatment, is widely used as a treatment technology of distillery wastes. An economic comparison between two different treatment processes; a traditional concentration unit and the termophilic hybrid anaerobic...
F. De Poli E. Mela S. Pasqualini
Dynamics of biofilm formation during anaerobic digestion of organic waste.
Biofilm-based reactors are effectively used for wastewater treatment but are not common in biogas production. This study investigated biofilm dynamics on biofilm carriers incubated in batch biogas reactors at high and low organic loading rates for sludge from meat industry dissolved air flotation units. Biofilm formation and dynamics were studied using various microscopic techniques. Resulting micrographs were analysed for total cell numbers, thickness of biofilms, biofilm-covered surface area, and the area covered by extracellular polymeric substances (EPS). Cell numbers within biofilms (10(11)�cells�ml(-1)) were up to one order of magnitude higher compared to the numbers of cells in the fluid reactor content. Further, biofilm formation and structure mainly correlated with the numbers of microorganisms present in the fluid reactor content and the organic loading. At high organic loading (45�kg�VS�m(-3)), the thickness of the continuous biofilm layer ranged from 5 to 160�?m with an average of 51�?m and a median of 26�?m. Conversely, at lower organic loading (15�kg�VS�m(-3)), only microcolonies were detectable. Those microcolonies increased in their frequency of occurrence during ongoing fermentation. Independently from the organic loading rate, biofilms were embedded completely in EPS within seven days. The maturation and maintenance of biofilms changed during the batch fermentation due to decreasing substrate availability. Concomitant, detachment of microorganisms within biofilms was observed simultaneously with the decrease of biogas formation. This study demonstrates that biofilms of high cell densities can enhance digestion of organic waste and have positive effects on biogas production. PMID:24342346
Langer, Susanne; Schropp, Daniel; Bengelsdorf, Frank R; Othman, Maazuza; Kazda, Marian
A comparative study of anaerobic digestion of acid cheese whey and dairy manure in a two-stage reactor
The performance of a two-stage, two-phase, unmixed anaerobic digester of 155 l working volume operating on acid cheese whey and dairy manure at various temperatures and hydraulic retention times was investigated. The effect of controlling the pH of the methanogonic stage of cheese whey digestion on the biogas production rate and pollution potential reduction was also investigated. The digester was
A. E. Ghaly
Sulfate reduction, nutrient limitation, and reactor design considerations in anaerobic digesters
Three areas of improvement in anaerobic digestion were investigated: inhibition of sulfate reduction, nutrient limitation, and reactor design. In the anaerobic treatment of wastewaters containing high concentrations of sulfate, hydrogen sulfide, an undesirable end product, is produced by sulfate reducing bacteria (SRB). Research was conducted to evaluate the feasibility of adding SRB-specific biochemical inhibitors to a waste stream as a method of preventing sulfate reduction in continuous anaerobic digesters. Two classes of inhibitory compounds were identified: (1) sulfate analogs and (2) transition metal divalent cations. Molybdate was found to have an immediate inhibitory effect on sulfate reduction, and a delayed effect on other trophic groups. Non-specific inhibition was not caused by a dynamic imbalance due to cessation of fatty acid degradation via sulfate reduction. Transition metals had no effect on sulfate reduction or overall digester performance in high sulfate digesters. The hypothesis that nutrient limitation could be synergistically coupled with the addition of SRB-specific inhibitors was investigated. Recovery of sulfate reduction was slower after molybdate removal from the feed when phosphate was limited as compared with when it was continually added, although this effect may have been an indirect result of non-specific inhibition. Periodic pulse nutrient addition was investigated as a method of (1) reducing cell growth, sludge production and related disposal costs and (2) reducing nutrient addition costs. Sustained waste treatment performance was demonstrated for iron, phosphorus, and nitrogen-free feeds. When withheld nutrients were added in pulses, effective operation could be maintained over long periods. Increasing pulse strength delayed the onset of adverse effects related to nutrient starvation.
Clancy, P.B.
Kinetics and dynamic modelling of batch anaerobic digestion of municipal solid waste in a stirred reactor
A series of batch, slurry anaerobic digestion experiments were performed where the soluble and insoluble fractions, and unwashed MSW were separately digested in a 200 l stirred stainless steel vessel at a pH of 7.2 and a temperature of 38 deg. C. It was found that 7% of the total MSW COD was readily soluble, of which 80% was converted to biogas; 50% of the insoluble fraction was solubilised, of this only 80% was converted to biogas. The rate of digesting the insoluble fraction was about four times slower than the rate of digesting the soluble fraction; 48% of the total COD was converted to biogas and 40% of the total nitrogen was converted to ammonia. Soluble and insoluble fractions were broken down simultaneously. The minimum time to convert 95% of the degradable fraction to biogas was 20 days. The lag phase for the degradation of insoluble fraction of MSW can be overcome by acclimatising the culture with the soluble fraction. The rate of digestion and the methane yield was not affected by particle size (within the range of 2-50 mm). A dynamic model was developed to describe batch digestion of MSW. The parameters of the model were estimated using data from the separate digestion of soluble and insoluble fractions and validated against data from the digestion of unwashed MSW. Trends in the specific aceticlastic and formate-utilising methanogenic activity were used to estimate initial methanogenic biomass concentration and bacterial death rate coefficient. The kinetics of hydrolysis of insoluble fraction could be adequately described by a Contois equation and the kinetics of acidogenesis, and aceticlastic and hydrogen utilising methanogenesis by Monod equations.
Nopharatana, Annop [Division of Environmental of Engineering, The University of Queensland, Brisbane, Qld. 4072 (Australia); Pilot Plant Development and Training Institute, King Mongkut's University of Technology, Thonburi, Bangkok 10150 (Thailand); Pullammanappallil, Pratap C. [Division of Environmental of Engineering, The University of Queensland, Brisbane, Qld. 4072 (Australia); Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611 (United States); Clarke, William P. [Division of Environmental of Engineering, The University of Queensland, Brisbane, Qld. 4072 (Australia)], E-mail: email@example.com
Methane from an integrated hyacinth treatment anaerobic digestion facility
Results to date indicate that the Hyacinth Project could lead to the production of cost-competitive methane from a hyacinth wastewater treatment system. An information base from the project will be available by the end of 1985 to support a decision on whether methane generation from a hyacinth facility is sufficiently attractive for communities and gas companies to pursue at a commercial scale. If the economics are promising, construction of a full-scale plant could begin in the late 1980s. The project could ultimately provide a low-cost supplemental source of pipeline-quality gas while offering a cost-effective wastewater treatment alternative. 9 references, 4 figures, 2 tables.
Hayes, T.D.; Chynoweth, D.P.; Reddy, K.R.; Schwegler, B.
Characterization of a Methanogenic Community within an Algal Fed Anaerobic Digester
The microbial diversity and metabolic potential of a methanogenic consortium residing in a 3785-liter anaerobic digester, fed with wastewater algae, was analyzed using 454 pyrosequencing technology. DNA was extracted from anaerobic sludge material and used in metagenomic analysis through PCR amplification of the methyl-coenzyme M reductase ? subunit (mcrA) gene using primer sets ML, MCR, and ME. The majority of annotated mcrA sequences were assigned taxonomically to the genera Methanosaeta in the order Methanosarcinales. Methanogens from the genus Methanosaeta are obligate acetotrophs, suggesting this genus plays a dominant role in methane production from the analyzed fermentation sample. Numerous analyzed sequences within the algae fed anaerobic digester were unclassified and could not be assigned taxonomically. Relative amplicon frequencies were determined for each primer set to determine the utility of each in pyrosequencing. Primer sets ML and MCR performed better quantitatively (representing the large majority of analyzed sequences) than primer set ME. However, each of these primer sets was shown to provide a quantitatively unique community structure, and thus they are of equal importance in mcrA metagenomic analysis.
Ellis, Joshua T.; Tramp, Cody; Sims, Ronald C.; Miller, Charles D.
Application of urea dosing for alkalinity supply during anaerobic digestion of vinasse.
Pushed by demand for renewable energy, the ethanol industry in Brazil is expanding. However, production of 1 m(3) of ethanol generates around 13 m(3) of liquid residues (vinasse), so this expansion results in an increasing need for a more adequate destination of these residues. Nowadays the vinasse is dispersed on the sugar cane fields in the practice of fertirrigation, but anaerobic digestion of this residue may be a better solution, additionally offering an alternative source of energy, able to complement hydroelectric power supply in the dry season. However, when trying to digest vinasse at reduced hydraulic retention times, complications arise from its strong tendency toward acidification, upsetting the fragile balance of transformations normally occurring under anaerobic conditions. For successful operation of an anaerobic treatment process with acceptable hydraulic residence times, increasing alkalinity levels inside the reactor is neces-sary. In the present work we show that pH regulation by means of urea dosing, in spite of the risk posed by ammonia toxicity towards methanogenic biomass, can be a viable alternative to avoid vinasse acidification. The ammonia formed in urea conversion remains in solution, rather than escaping to the biogas, and so its use as fertiliser can offset its cost of application in the process. PMID:23032778
Boncz, M A; Formagini, E L; Santos, L da S; Marques, R D; Paulo, P L
The efficiency of concentration methods used to detect enteric viruses in anaerobically digested sludge.
The presence of enteric viruses in biosolids can be underestimated due to the inefficient methods (mainly molecular methods) used to recover the viruses from these matrices. Therefore, the goal of this study was to evaluate the different methods used to recover adenoviruses (AdV), rotavirus species A (RVA), norovirus genogroup II (NoV GII) and the hepatitis A virus (HAV) from biosolid samples at a large urban wastewater treatment plant in Brazil after they had been treated by mesophilic anaerobic digestion. Quantitative polymerase chain reaction (PCR) was used for spiking experiments to compare the detection limits of feasible methods, such as beef extract elution and ultracentrifugation. Tests were performed to detect the inhibition levels and the bacteriophage PP7 was used as an internal control. The results showed that the inhibitors affected the efficiency of the PCR reaction and that beef extract elution is a suitable method for detecting enteric viruses, mainly AdV from biosolid samples. All of the viral groups were detected in the biosolid samples: AdV (90%), RVA, NoV GII (45%) and HAV (18%), indicating the viruses' resistance to the anaerobic treatment process. This is the first study in Brazil to detect the presence of RVA, AdV, NoV GII and HAV in anaerobically digested sludge, highlighting the importance of adequate waste management. PMID:23440119
Prado, Tatiana; Guilayn, Wilma de Carvalho Pereira Bonet; Gaspar, Ana Maria Coimbra; Miagostovich, Marize Pereira
Methanogenic pathway and community structure in a thermophilic anaerobic digestion process of organic solid waste.
The methanogenic pathway and microbial community in a thermophilic anaerobic digestion process of organic solid waste were investigated in a continuous-flow stirred-tank reactor using artificial garbage slurry as a feedstock. The decomposition pathway of acetate, a significant precursor of CH(4) and a key intermediate metabolite in the anaerobic digestion process, was analyzed by using stable isotopes. A tracer experiment using (13)C-labeled acetate revealed that approximately 80% of the acetate was decomposed via a non-aceticlastic oxidative pathway, whereas the remainder was converted to methane via an aceticlastic pathway. Archaeal 16S rRNA analyses demonstrated that the hydrogenotrophic methanogens Methanoculleus spp. accounted for >90% of detected methanogens, and the aceticlastic methanogens Methanosarcina spp. were the minor constituents. The clone library targeting bacterial 16S rRNA indicated the predominance of the novel Thermotogales bacterium (relative abundance: ~53%), which is related to anaerobic acetate oxidizer Thermotoga lettingae TMO, although the sequence similarity was low. Uncultured bacteria that phylogenetically belong to municipal solid waste cluster I were also predominant in the microflora (~30%). These results imply that the microbial community in the thermophilic degrading process of organic solid waste consists exclusively of unidentified bacteria, which efficiently remove acetate through a non-aceticlastic oxidative pathway. PMID:20851673
Sasaki, Daisuke; Hori, Tomoyuki; Haruta, Shin; Ueno, Yoshiyuki; Ishii, Masaharu; Igarashi, Yasuo
The efficiency of concentration methods used to detect enteric viruses in anaerobically digested sludge
The presence of enteric viruses in biosolids can be underestimated due to the inefficient methods (mainly molecular methods) used to recover the viruses from these matrices. Therefore, the goal of this study was to evaluate the different methods used to recover adenoviruses (AdV), rotavirus species A (RVA), norovirus genogroup II (NoV GII) and the hepatitis A virus (HAV) from biosolid samples at a large urban wastewater treatment plant in Brazil after they had been treated by mesophilic anaerobic digestion. Quantitative polymerase chain reaction (PCR) was used for spiking experiments to compare the detection limits of feasible methods, such as beef extract elution and ultracentrifugation. Tests were performed to detect the inhibition levels and the bacteriophage PP7 was used as an internal control. The results showed that the inhibitors affected the efficiency of the PCR reaction and that beef extract elution is a suitable method for detecting enteric viruses, mainly AdV from biosolid samples. All of the viral groups were detected in the biosolid samples: AdV (90%), RVA, NoV GII (45%) and HAV (18%), indicating the viruses' resistance to the anaerobic treatment process. This is the first study in Brazil to detect the presence of RVA, AdV, NoV GII and HAV in anaerobically digested sludge, highlighting the importance of adequate waste management.
Feedstocks affect the diversity and distribution of propionate CoA-transferase genes (pct) in anaerobic digesters.
Anaerobic digestion (AD) is an attractive microbiological technology for both waste treatment and energy production. Syntrophic acetogenic bacteria are an important guild because they are essential for maintaining efficient and stable AD operation. However, this guild is poorly understood due to difficulties to culture them. In this study, we developed specific PCR assays targeting the propionate-CoA transferase genes (pct) to investigate their diversity and distribution in several mesophilic anaerobic digesters and a bench-scale temperature-phased AD (TPAD) system. Phylogenetic analysis of sequenced pct amplicons revealed the occurrence of Syntrophobacter fumaroxidans and six other clusters of putative pct genes. Principal coordinate analysis (PCoA) showed that pct diversity and abundance were largely correlated to the feedstocks of the digesters, while little difference was seen between the granular and the liquid fractions of each digester or between the two digesters of the TPAD system. Cluster-specific qPCR analysis revealed major impact of feedstocks and fractions on the abundance of pct genes. Readily fermentable substrates such as sugar- or starch-rich feedstocks selected for pct genes (Cluster I) related to Syntrophobacter, while manure feedstock selected for pct clusters related to pct of Clostridium spp. These results suggest that propionate metabolism can be affected by feedstocks and partition differently between solid and liquid phases in digesters. The PCR assays developed in this study may serve as a tool to investigate propionate-oxidizing bacteria in anaerobic digesters and other anaerobic environments. PMID:23640276
Li, Yueh-Fen; Wei, Shan; Yu, Zhongtang
Archaeal community composition affects the function of anaerobic co-digesters in response to organic overload
Highlights: Black-Right-Pointing-Pointer Two types of methanogens are necessary to respond successfully to perturbation. Black-Right-Pointing-Pointer Diversity of methanogens correlates with the VFA concentration and methane yield. Black-Right-Pointing-Pointer Aggregates indicate tight spatial relationship between minerals and microorganisms. - Abstract: Microbial community diversity in two thermophilic laboratory-scale and three full-scale anaerobic co-digesters was analysed by genetic profiling based on PCR-amplified partial 16S rRNA genes. In parallel operated laboratory reactors a stepwise increase of the organic loading rate (OLR) resulted in a decrease of methane production and an accumulation of volatile fatty acids (VFAs). However, almost threefold different OLRs were necessary to inhibit the gas production in the reactors. During stable reactor performance, no significant differences in the bacterial community structures were detected, except for in the archaeal communities. Sequencing of archaeal PCR products revealed a dominance of the acetoclastic methanogen Methanosarcina thermophila, while hydrogenotrophic methanogens were of minor importance and differed additionally in their abundance between reactors. As a consequence of the perturbation, changes in bacterial and archaeal populations were observed. After organic overload, hydrogenotrophic methanogens (Methanospirillum hungatei and Methanoculleus receptaculi) became more dominant, especially in the reactor attributed by a higher OLR capacity. In addition, aggregates composed of mineral and organic layers formed during organic overload and indicated tight spatial relationships between minerals and microbial processes that may support de-acidification processes in over-acidified sludge. Comparative analyses of mesophilic stationary phase full-scale reactors additionally indicated a correlation between the diversity of methanogens and the VFA concentration combined with the methane yield. This study demonstrates that the coexistence of two types of methanogens, i.e. hydrogenotrophic and acetoclastic methanogens is necessary to respond successfully to perturbation and leads to stable process performance.
Lerm, S.; Kleyboecker, A. [International Centre for Geothermal Research (ICGR), GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany); Miethling-Graff, R. [International Centre for Geothermal Research (ICGR), GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany); Johann Heinrich von Thuenen Institut, Bundesforschungsinstitut fuer Laendliche Raeume, Wald und Fischerei Institut fuer Biodiversitaet, 38116 Braunschweig (Germany); Alawi, M.; Kasina, M.; Liebrich, M. [International Centre for Geothermal Research (ICGR), GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany); Wuerdemann, H., E-mail: email@example.com [International Centre for Geothermal Research (ICGR), GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany)
Two-phase thermophilic anaerobic digestion process for biohythane production treating biowaste: preliminary results.
This paper deals with the optimization of a two-phase anaerobic process treating biowaste for hydrogen and methane production. Neither physical nor chemical pre-treatments were used to optimize the process. The work was carried out at pilot scale, using two CSTRs (200 and 380 L working volume respectively) both maintained at thermophilic temperature (55 C) and fed semi-continuously with biowaste. The experiment was divided into three periods; during the first two periods the organic loading rate was maintained at 20 kg TVS/m3 d and the hydraulic retention time was changed from 6.6 to 3.3 days, while in the last period the digestate of the second reactor was recirculated to the first reactor in order to buffer the system and control pH at levels around 5. The HRT was maintained at 3.3 days and the OLR was decreased at 16.5 kg TVS/m3 d. The best yield was obtained in the last period where a specific hydrogen production of 50.9 L/kg VSfed was reached, with a H2 content in biogas from the first reactor of 36%. The methanogenic stage after the hydrogen conversion reached a specific biogas production of 0.62 m3/kg VSfed and an overall organic removal above 70%, without any stability problem. The overall biogas production was some 1.5 m3 per day with a gas composition of 10% H2 and 50% CH4. PMID:22097052
Cavinato, C; Bolzonella, D; Fatone, F; Giuliano, A; Pavan, P
Effect of anaerobic digestion at 35, 55 and 60 �C on pharmaceuticals and organic contaminants.
The application of treated sewage sludge on farmland is a suggested method for recycling nutrients and reducing demand for commercial fertilizer. However, sludge needs to be safe from possible contaminants which can cause acute and long-term health and environmental problems. Residual pharmaceuticals and organic contaminants are mentioned as emerging threats since wastewater treatment plants are not designed to degrade these substances. The aim of this study was to screen and evaluate the presence, and reduction, of pharmaceuticals and polycyclic aromatic hydrocarbons (PAHs) during anaerobic digestion of mixed primary and waste-activated sludge at 35, 55 and 60 �C and during pasteurization at 70 �C. The study showed the difficulty of analysing pharmaceutical compounds in low concentrations in the sludge matrix. No general reduction of these compounds was seen during treatment, but for individual substances some reduction occurred. The PAHs were generally not reduced during digestion or pasteurization, but for three substances (indeno[1,2,3-cd]pyrene and dibenzo[a,h]anthracene (analysed together) and benzo[g,h,i]perylene) reduction (up to 60%) during digestion was seen. Digestion at 35 and 55 �C resulted in about the same order of reduction of the three individual PAHs, which was higher than for digestion at 60 �C. PMID:24647195
Davidsson, A; Kjerstadius, H; Haghighatafshar, S; Fick, J; Olsson, M; Wachtmeister, H; Eriksson, E; la Cour Jansen, J
Improvement of mesophilic anaerobic co-digestion of agri-food waste by addition of glycerol.
Anaerobic co-digestion is a promising alternative to manage agri-food waste rather than landfilling, composting or incineration. But improvement of methane yield and biodegradability is often required to optimize its economic viability. Biomethanization of agri-food solid waste presents the disadvantage of a slow hydrolytic phase, which might be enhanced by adding a readily digestible substrate such as glycerol. In this study, strawberry extrudate, fish waste and crude glycerol derived from biodiesel manufacturing are mixed at a proportion of 54:5:41, in VS (VS, total volatile solids), respectively. The mesophilic anaerobic co-digestion at lab-scale of the mixture was stable at loads lower than 1.85�g VS/L, reaching a methane yield coefficient of 308�L CH4/kg VS (0��C, 1�atm) and a biodegradability of 96.7%, in VS. Moreover, the treatment capacity of strawberry and fish waste was increased 16% at adding the crude glycerol. An economic assessment was also carried out in order to evaluate the applicability of the proposed process. Even in a pessimistic scenario, the net balance was found to be positive. The glycerol adding implied a net saving in a range from 25.5 to 42.1 �/t if compared to landfill disposal. PMID:24726968
Serrano, Antonio; Siles, Jose A; Chica, Arturo F; Martin, M Angeles
Microbial ecology of the leach bed anaerobic digestion of unsorted municipal solid waste.
The microbial ecology of the sequential, leach-bed, mesophilic anaerobic digestion of unsorted, coarse municipal solid waste (MSW) was examined over 80 days. The methane yield was approximately 75% of the ultimate biochemical methane potential (BMP) of the waste loaded into the digesters. The operational strategy involved a sequence of two digesters containing fresh and anaerobically stabilised MSW respectively. Cell wall phospholipid fatty acid (PLFA) and ether lipid (PLEL) analysis was used to monitor changes in microbial biomass. Both Bacterial and Archaeal biomass were heavily influenced by pH during the two-week start up period. Archaeal biomass peaked just before the methane production rate reached a maximum whereas Bacterial biomass peaked at a later stage. Changes in the phylogenetic diversity of the population were monitored by denaturing gradient gel electrophoresis (DGGE). An analysis of the changes in DGGE banding patterns suggested that rapid start-up of a new reactor was effected by inoculation as well as the provision of buffering capacity from the mature reactor leachate. PMID:11382013
Silvey, P; Pullammanappallil, P C; Blackall, L; Nichols, P
Anaerobic digestion of raw and thermally hydrolyzed wastewater solids under various operational conditions.
In this study, high-solids anaerobic digestion of thermally pretreated wastewater solids (THD) was compared with conventional mesophilic anaerobic digestion (MAD). Operational conditions, such as pretreatment temperature (150 to 170 degrees C), solids retention time (15 to 20 days), and digestion temperature (37 to 42 degrees C), were varied for the seven THD systems operated. Volatile solids reduction (VSR) by THD ranged from 56 to 62%, compared with approximately 50% for MAD. Higher VSR contributed to 24 to 59% increased biogas production (m3/kg VSR-d) from THD relative to MAD. The high-solids conditions of the THD feed resulted in high total ammonia-nitrogen (proportional to solids loading) and total alkalinity concentrations in excess of 14 g/L as calcium carbonate (CaCO3). Increased pH in THD reactors caused 5 to 8 times more un-ionized ammonia to be present than in MAD, and this likely led to inhibition of aceticlastic methanogens, resulting in accumulation of residual volatile fatty acids between 2 and 6 g/L as acetic acid. The THD produced biosolids cake that possessed low organic sulfur-based biosolids odor and dewatered to between 33 and 39% total solids. Dual conditioning with cationic polymer and ferric chloride was shown to be an effective strategy for mitigating dissolved organic nitrogen and UV-quenching compounds in the return stream following centrifugal dewatering of THD biosolids. PMID:22073729
Wilson, Christopher A; Tanneru, Charan T; Banjade, Sarita; Murthy, Sudhir N; Novak, John T
Enhanced high-solids anaerobic digestion of waste activated sludge by the addition of scrap iron.
Anaerobic digestion of waste activated sludge usually requires pretreatment procedure to improve the bioavailability of sludge, which involves considerable energy and high expenditures. This study proposes a cost-effective method for enhanced anaerobic digestion of sludge without a pretreatment by directly adding iron into the digester. The results showed that addition of Fe(0) powder could enhance 14.46% methane yield, and Fe scrap (clean scrap) could further enhance methane yield (improving rate 21.28%) because the scrap has better mass transfer efficiency with sludge and liquid than Fe(0) powder. The scrap of Fe with rust (rusty scrap) could induce microbial Fe(III) reduction, which resulted in achieving the highest methane yield (improving rate 29.51%), and the reduction rate of volatile suspended solids (VSS) was also highest (48.27%) among Fe powder, clean scrap and rusty scrap. PCR-DGGE proved that the addition of rusty scrap could enhance diversity of acetobacteria and enrich iron-reducing bacteria to enhance degradation of complex substrates. PMID:24657762
Zhang, Yaobin; Feng, Yinghong; Yu, Qilin; Xu, Zibin; Quan, Xie
Liquid digestate from anaerobic treatment of source-separated household waste as fertilizer to barley.
This study examined the efficiency of different organic waste materials as NPK fertilizer, in addition to the risk for leaching losses related to shower precipitation in the first part of the growing season. The experiment was tested in a pot trial on a sandy soil in a greenhouse. Six organic fertilizers were evaluated: liquid anaerobic digestate (LAD) sourced from separated household waste, nitrified liquid anaerobic digestate (NLAD) of the same origin as LAD, meat and bone meal (MBM), hydrolysed salmon protein (HSP), reactor-composted catering waste (CW) and cattle manure (CM). An unfertilized control, calcium nitrate (CN) and Fullgj�dsel� 21-4-10 were used as reference fertilizers. At equal amounts of mineral nitrogen both LAD and Fullgj�dsel� gave equal yield of barley in addition to equal uptake of N, P, and K in barley grain. NLAD gave significantly lower barley yield than the original LAD due to leaching of nitrate-N after a simulated surplus of precipitation (28?mm) at Zadoks 14. There was significantly increased leaching of nitrate N from the treatments receiving 160?kg?N?ha(-1) of CN and NLAD in comparison with all the other organic fertilizers. In this study LAD performed to the same degree as Fullgj�dsel� NPK fertilizer and it was concluded that LAD can be recommended as fertilizer for cereals. Nitrification of the ammonium N in the digestate caused significantly increased nitrate leaching, and cannot be recommended. PMID:21746761
Haraldsen, Trond Knapp; Andersen, Uno; Krogstad, Tore; S�rheim, Roald
Reducing the environmental impact of methane emissions from dairy farms by anaerobic digestion of cattle waste.
Four dairy cattle farms considered representative of Northern Spain milk production were studied. Cattle waste was characterised and energy consumption in the farms was inventoried. Methane emissions due to slurry/manure management and fuel consumption on the farms were calculated. The possibility of applying anaerobic digestion to the slurry to minimise emissions and of using the biogas produced to replace fossil fuels on the farm was considered. Methane emissions due to slurry management (storage and use as fertiliser) ranged from 34 to 66kg CH(4)cow(-1)year(-1) for dairy cows and from 13 to 25kg CH(4)cow(-1)year(-1) for suckler calves. Cattle on these farms are housed for most of the year, and the contribution from emissions from manure dropped in pastures is insignificant due to the very low methane conversion factors. If anaerobic digestion were implemented on the farms, the potential GHG emissions savings per livestock unit would range from 978 to 1776kg CO(2)eq year(-1), with the main savings due to avoided methane emissions during slurry management. The methane produced would be sufficient to supply digester heating needs (35-55% of the total methane produced) and on-farm fuel energy requirements. PMID:21504844
Mara��n, E; Salter, A M; Castrill�n, L; Heaven, S; Fern�ndez-Nava, Y
Anaerobic Digestion of Renewable Biomass: Thermophilic Temperature Governs Methanogen Population Dynamics ? �
Beet silage and beet juice were digested continuously as representative energy crops in a thermophilic biogas fermentor for more than 7 years. Fluorescence microscopy of 15 samples covering a period of 650 days revealed that a decrease in temperature from 60�C to 55�C converted a morphologically uniform archaeal population (rods) into a population of methanogens exhibiting different cellular morphologies (rods and coccoid cells). A subsequent temperature increase back to 60�C reestablished the uniform morphology of methanogens observed in the previous 60�C period. In order to verify these observations, representative samples were investigated by amplified rRNA gene restriction analysis (ARDRA) and fluorescence in situ hybridization (FISH). Both methods confirmed the temperature-dependent population shift observed by fluorescence microscopy. Moreover, all samples investigated demonstrated that hydrogenotrophic Methanobacteriales dominated in the fermentor, as 29 of 34 identified operational taxonomic units (OTUs) were assigned to this order. This apparent discrimination of acetoclastic methanogens contradicts common models for anaerobic digestion processes, such as anaerobic digestion model 1 (ADM1), which describes the acetotrophic Euryarchaeota as predominant organisms.
Krakat, Niclas; Westphal, A.; Schmidt, S.; Scherer, P.
Ribosomal intergenic spacer analysis as a tool for monitoring methanogenic Archaea changes in an anaerobic digester.
The applicability of a newly-designed PCR primer pair in examination of methanogenic Archaea in a digester treating plant biomass was evaluated by Ribosmal Intergenic Spacer Analysis (RISA). To find a suitable approach, three variants of RISA were tested: (1) standard, polyacrylamide gel-based, (2) automated, utilized capillary electrophoresis (GA-ARISA), and (3) automated microfluidics-based (MF-ARISA). All three techniques yielded a consistent picture of archaeal community structure changes during anaerobic digestion monitored for more than 6�weeks. While automated variants were more practical for handling and rapid analysis of methanogenic Archaea, the gel-based technique was advantageous when micro-organism identification was required. A DNA-sequence analysis of dominant bands extracted from the gel revealed that the main role in methane synthesis was played by micro-organisms affiliated with Methanosarcina barkeri. The obtained results revealed that RISA is a robust method allowing for detailed analysis of archaeal community structure during organic biomass conversion into biogas. In addition, our results showed that GA-ARISA has a higher resolution and reproducibility than other variants of RISA and could be used as a technique for tracking changes in methanogenic Archaea in an anaerobic digester. PMID:23525724
Ciesielski, Slawomir; Bu?kowska, Katarzyna; Dabrowska, Dorota; Kaczmarczyk, Dariusz; Kowal, Przemyslaw; Mo?ejko, Justyna
Comparison of seven chemical pretreatments of corn straw for improving methane yield by anaerobic digestion.
Agriculture straw is considered a renewable resource that has the potential to contribute greatly to bioenergy supplies. Chemical pretreatment prior to anaerobic digestion can increase the anaerobic digestibility of agriculture straw. The present study investigated the effects of seven chemical pretreatments on the composition and methane yield of corn straw to assess their effectiveness of digestibility. Four acid reagents (H2SO4, HCl, H2O2, and CH3COOH) at concentrations of 1%, 2%, 3%, and 4% (w/w) and three alkaline reagents (NaOH, Ca(OH)2, and NH3�H2O) at concentrations of 4%, 6%, 8%, and 10% (w/w) were used for the pretreatments. All pretreatments were effective in the biodegradation of the lignocellulosic straw structure. The straw, pretreated with 3% H2O2 and 8% Ca(OH)2, acquired the highest methane yield of 216.7 and 206.6 mL CH4 g VS -1 in the acid and alkaline pretreatments, which are 115.4% and 105.3% greater than the untreated straw. H2O2 and Ca(OH)2 can be considered as the most favorable pretreatment methods for improving the methane yield of straw because of their effectiveness and low cost. PMID:24695485
Song, Zilin; Gaiheyang; Liu, Xiaofeng; Yan, Zhiying; Yuan, Yuexiang; Liao, Yinzhang
Digestion and dewatering characteristics of waste activated sludge treated by an anaerobic biofilm system.
Immobilization of microorganisms for sludge anaerobic digestion was investigated in this study. The effects of filler properties on anaerobic digestion and dewaterability of waste activated sludge were assessed at mesophilic temperature in batch mode. The results showed that the duration of the methanogenic stage of reactors without filler, with only filler, and with pre-incubated filler was 39days, 19days and 13days, respectively, during which time the protein was degraded by 45.0%, 29.4% and 30.0%, and the corresponding methane yield was 193.9, 107.2 and 108.2mL/g volatile suspended solids added, respectively. On day 39, the final protein degradation efficiency of the three reactors was 45.0%, 40.9% and 42.0%, respectively. The results of normalized capillary suction time and specific resistance to filtration suggested that the reactor incorporating pre-incubated filler could improve the dewaterability of digested sludge, while the effect of the reactor incorporating only filler on sludge dewaterability was uncertain. PMID:24355503
Wang, Tianfeng; Shao, Liming; Li, Tianshui; L�, Fan; He, Pinjing
Managing Dairy Waste Inputs in Morrisville's Hard-top Plug-flow Anaerobic Digester (Final Report June 30, 2005-December 31, 2006).
The state of New York through the New York State Energy Research and Development Authority (NYSERDA) has developed a suite of digester projects throughout the state to assess the potential for anaerobic digestion systems to improve manure management and c...
W. H. Shayya
Hydrogen utilization rate: A crucial indicator for anaerobic digestion process evaluation and monitoring.
Hydrogenotrophic methanogens had been considered as key species for the anaerobic digestion (AD) of industrial wastewater and municipal sludge. However, how to evaluate the activity of the hydrogenotrophic methanogens was less studied. In this study, a volumetric device and a test procedure were developed for measuring the specific hydrogen utilization rate (HUR) of anaerobic sludge. Results showed that HUR values were highly influenced by sludge concentrations because of limitation on H2 mass transfer. The critical value of sludge concentration in the test bottle should not be higher than 1 gVSS/L. Under such condition, the kinetics of HUR would not be limited by H2 mass transfer and the maximal value of HUR could be obtained. Field survey confirmed that HUR exhibits a good relationship with specific methanogenic activity (SMA) and reactor performance. An anaerobic system with a relatively high HUR was found to be beneficial for maintaining H2 partial pressure in an appropriately low level. Moreover, such system was thermodynamically favourable for the syntrophic degradation of volatile fatty acids. As a crucial parameter of the anaerobic process, HUR could be used as a key indicator for evaluating and monitoring AD processes. PMID:24216460
Hou, Yin-ping; Peng, Dang-cong; Xue, Xu-dong; Wang, Hong-ye; Pei, Li-ying
Treatment of olive oil mill wastewater by combined process electro-Fenton reaction and anaerobic digestion.
In this work, we investigated an integrated technology for the treatment of the recalcitrant contaminants of olive mill wastewaters (OMW), allowing water recovery and reuse for agricultural purposes. The method involves an electrochemical pre-treatment step of the wastewater using the electro-Fenton reaction followed by an anaerobic bio-treatment. The electro-Fenton process removed 65.8% of the total polyphenolic compounds and subsequently decreased the OMW toxicity from 100% to 66.9%, which resulted in improving the performance of the anaerobic digestion. A continuous lab-scale methanogenic reactor was operated at a loading rate of 10 g chemical oxygen demand (COD)l(-1) d(-1) without any apparent toxicity. Furthermore, in the combined process, a high overall reduction in COD, suspended solids, polyphenols and lipid content was achieved by the two successive stages. This result opens promising perspectives since its conception as a fast and cheap pre-treatment prior to conventional anaerobic post-treatment. The use of electro-coagulation as post-treatment technology completely detoxified the anaerobic effluent and removed its toxic compounds. PMID:16678883
Khoufi, Sonia; Aloui, Fathi; Sayadi, Sami
Evaluation of the anaerobic co-digestion of sewage sludge and tomato waste at mesophilic temperature.
Sewage sludge is a hazardous waste, which must be managed adequately. Mesophilic anaerobic digestion is a widely employed treatment for sewage sludge involving several disadvantages such as low methane yield, poor biodegradability, and nutrient imbalance. Tomato waste was proposed as an easily biodegradable co-substrate to increase the viability of the process in a centralized system. The mixture proportion of sewage sludge and tomato waste evaluated was 95:5 (wet weight), respectively. The stability was maintained within correct parameters in an organic loading rate from 0.4 to 2.2 kg total volatile solids (VS)/m(3) day. Moreover, the methane yield coefficient was 159 l/kg VS (0 �C, 1 atm), and the studied mixture showed a high anaerobic biodegradability of 95 % (in VS). Although the ammonia concentration increased until 1,864 � 23 mg/l, no inhibition phenomenon was determined in the stability variables, methane yield, or kinetics parameters studied. PMID:24682875
Belhadj, Siham; Joute, Yassine; El Bari, Hassan; Serrano, Antonio; Gil, Aida; Siles, Jos� A; Chica, Arturo F; Mart�n, M Angeles
Comparison of various microbial inocula for the efficient anaerobic digestion of Laminaria hyperborea
Background The hydrolysis of seaweed polysaccharides is the rate limiting step in anaerobic digestion (AD) of seaweeds. Seven different microbial inocula and a mixture of these (inoculum 8) were therefore compared in triplicate, each grown over four weeks in static culture for the ability to degrade Laminaria hyperborea seaweed and produce methane through AD. Results All the inocula could degrade L. hyperborea and produce methane to some extent. However, an inoculum of slurry from a human sewage anaerobic digester, one of rumen contents from seaweed-eating North Ronaldsay sheep and inoculum 8 used most seaweed volatile solids (VS) (means ranged between 59 and 68% used), suggesting that these each had efficient seaweed polysaccharide digesting bacteria. The human sewage inoculum, an inoculum of anaerobic marine mud mixed with rotting seaweed and inoculum 8 all developed to give higher volumes of methane (means between 41 and 62.5 ml g-1 of seaweed VS by week four) ,compared to other inocula (means between 3.5 and 27.5 ml g-1 VS). Inoculum 8 also gave the highest acetate production (6.5 mmol g-1 VS) in a single-stage fermenter AD system and produced most methane (8.4 mL mmol acetate-1) in phase II of a two-stage AD system. Conclusions Overall inoculum 8 was found to be the most efficient inoculum for AD of seaweed. The study therefore showed that selection and inclusion of efficient polysaccharide hydrolysing bacteria and methanogenic archaea in an inoculum offer increased methane productivity in AD of L. hyperborea. This inoculum will now being tested in larger scale (10L) continuously stirred reactors optimised for feed rate and retention time to determine maximum methane production under single-stage and two-stage AD systems.
Prediction of trace compounds in biogas from anaerobic digestion using the MATLAB Neural Network Toolbox
Abstract The outlook,to apply the highly energetic biogas,from,anaerobic,digestion into fuel cells will result in a significantly higher electrical efficiency and,can contribute,to an increase of renewable,energy,production. The practical bottleneck is the fuel cell poisoning,caused,by several gaseous,trace compounds,like hydrogen,sulfide and,ammonia.,Hence artificial neural networks,were developed,to predict these trace compounds.,The experiments,concluded,that ammonia,in biogas,can indeed,be present up to 93 ppm. Hydrogen,sulfide and ammonia,concentrations,in biogas were
David P. B. T. B. Strik; Alexander M. Domnanovich; Loredana Zani; Rudolf Braun; Peter Holubar
Anaerobic digestion of organic waste in Japan: the first demonstration plant at Kyoto City.
Recycling of Municipal Solid Waste is vigorously promoted in Japan and the necessity of energy recovery from organic waste is increasing. An anaerobic digestion demonstration plant for organic waste in Kyoto City, Japan has been operated for about two years. Three kinds of wastes (garbage and leftovers from hotels, yard waste and used paper) mixed at various ratios are used. The plant has maintained stable operations with each mixture, generating biogas by the decomposition of VS at the rate of about 820 m3N/ton-VS. PMID:12201091
Komatsu, T; Kimura, T; Kuriyama, Y; Isshiki, Y; Kawano, T; Hirao, T; Masuda, M; Yokoyama, K; Matsumoto, T; Takeda, M
The variability in nutrient composition of Anaerobic Digestate granules produced from high shear granulation.
This study investigates the production of organic fertilizer using Anaerobic Digestate (as a nutrient source) and limestone powder as the raw materials. A two-level factorial experimental design was used to determine the influence of process variables on the nutrient homogeneity within the granules. Increasing the liquid-to-solid ratio during granulation resulted in increased granule nutrient homogeneity. Increasing the processing time and the impeller speed were also found to increase the nutrient homogeneity. In terms of nutrients release into deionized water, the granules effectively released both potassium and phosphate into solution. PMID:23083974
Mangwandi, Chirangano; JiangTao, Liu; Albadarin, Ahmad B; Allen, Stephen J; Walker, Gavin M
Treatment of anaerobic digestion effluent of sewage sludge using soilless cultivation
Soilless cultivation was carried out using anaerobic digestion effluent of sewage sludge as liquid fertilizer, with a preparation which cultures microorganisms in nutrient solution. As a result, ammonium ions contained in the effluent were nitrified into nitrate ions by the microorganisms. And then, Japanese mustard spinach (Brassica rapa var. perviridis) was cultivated by soilless cultivation system. The plants were grown well using microbial nutrient solution, which similar to the plants using conventional inorganic nutrient solution. In contrast, the plants were grown poorly using the effluent as liquid fertilizer without microorganisms.
Uchimura, Koki; Sago, Yuki; Kamahara, Hirotsugu; Atsuta, Yoichi; Daimon, Hiroyuki
An evaluation of the USEPA calculations of greenhouse gas emissions from anaerobic lagoons.
On 10 Apr. 2009, USEPA proposed and on 30 Oct. 2009 USEPA finalized reporting thresholds for a wide range of human-derived sources of greenhouse gas (GHG) as a first step in establishing emission limits in the United States. The only on-farm source category that required monitoring under the proposed and final rule was methane (CH(4)) and nitrous oxide (NO(2)) emissions from manure storage facilities. Our objective was to assess, through a literature review, the methodology used by USEPA to estimate current CH(4) emissions from uncovered anaerobic lagoons and the proposed methodology for reporting those emissions under the proposed rule. A review of the performance of uncovered anaerobic lagoons indicates that they are more effective at degrading volatile solids (VS) than predicted using parameters provided by USEPA that had been developed for anaerobic digesters. We also documented errors in the USEPA- and International Panel on Climate Change-estimated methane conversion factors for uncovered anaerobic lagoons. We suggest estimating CH(4) emissions from anaerobic lagoons based on VS degraded in the lagoon and B' (m(3) CH(4) generated kg(-1) VS destroyed). Our estimate of CH(4) released from uncovered anaerobic lagoons indicated the regulatory operation size threshold could be at least 65% smaller than predicted by USEPA in the proposed rule. Our calculated estimate of CH(4) emissions was substantially greater than the few estimates of CH(4) loss based on direct measurements on uncovered anaerobic lagoons. More research is needed before it will be possible to provide definitive estimates of CH(4) loss from uncovered anaerobic lagoons. PMID:20400573
Lory, John A; Massey, R E; Zulovich, J M
Characterization of three Chlorella sorokiniana strains in anaerobic digested effluent from cattle manure.
Chlorella sorokiniana CS-01, UTEX 1230 and UTEX 2714 were maintained in 10% anaerobic digester effluent (ADE) from cattle manure digestion and compared with algal cultivation in Bold's Basal Medium (BBM). Biomass of CS-01 and UTEX 1230 in ADE produced similar or greater than 280mg/L after 21days in BBM, however, UTEX 2714 growth in ADE was suppressed by more than 50% demonstrating a significant species bias to synthetic compared to organic waste-based media. The highest accumulation of protein and starch was exhibited in UTEX 1230 in ADE yielding 34% and 23% ash free dry weight (AFDW), respectively, though fatty acid methyl ester total lipid measured less than 12% AFDW. Results suggest that biomass from UTEX 1230 in ADE may serve as a candidate alga and growth system combination sustainable for animal feed production considering high yields of protein, starch and low lipid accumulation. PMID:24185420
Kobayashi, Naoko; Noel, Eric A; Barnes, Austin; Watson, Andrea; Rosenberg, Julian N; Erickson, Galen; Oyler, George A
Anaerobic model for high-solids or high-temperature digestion - additional pathway of acetate oxidation.
Current anaerobic digestion models cannot properly simulate processes that are operated under high solids concentrations or high temperatures. A modification to existing models has been implemented by adding important missing degradation pathways, to accommodate these systems without artificially recalibrating the model parameters. Specifically, we implemented the alternate acetate oxidizing mechanism that is more tolerant to ammonia than the standard aceticlastic pathway. Inhibition values were estimated and an empirical function has been used to apply ammonia inhibition. The model also relates metabolic activity to un-ionised species such as undissociated acetic acid as substrate (although not obligatory for all organisms) and unionised ammonia as inhibitor. The model relies on an equilibrium chemistry module (e.g. including the phosphate buffer), resulting in more accurate pH predictions, which is crucial for proper modeling of CO2 and NH3 stripping. Calibration results from three case-studies modeling thermal hydrolysis and subsequent digestion of sludge are presented. PMID:24759522
Wett, B; Tak�cs, I; Batstone, D; Wilson, C; Murthy, S
Can sludge dewatering reactivate microorganisms in mesophilically digested anaerobic sludge? Case of belt filter versus centrifuge.
The anaerobic digestion process that successfully reduces the organic content of sludge is one of the most common alternatives to meet pathogen reduction requirements for particular classes of biosolids. However, recently it was reported that, much higher densities of indicator bacteria were measured in dewatered cake samples compared to samples collected after anaerobic digestion. Additionally, this increase was commonly observed after centrifugation but not after belt filter dewatering. Several hypotheses were tested to explain this occurrence; however, much of the attention was given to the reactivation of the indicator bacteria which might enter a viable but non-culturable state (VBNC) during digestion. The objective of this research is to examine sludge samples from 5 different full-scale treatment plants in order to observe the effect of dewatering processes on the reactivation potential of indicator bacteria. The bacterial enumerations were performed by both Standard Culturing Methods (SCM) and quantitative polymerase chain (qPCR) on samples collected after digestion and dewatering. Results obtained by SCM indicated that in two investigated treatment plants operating belt filter dewatering, an average 0.6 log decrease was observed after the dewatering process. However, 0.7-1.4 log increases were observed immediately after centrifuge dewatering for the other three treatment plants. On the other hand, qPCR results gave 0.1-1.9 log higher numbers compared to SCM. Comparative evaluation of results obtained by two analytical methods for five treatment plants indicates that the differences observed might be originating from both reactivation of VBNC bacteria and amplification of DNA from dead cells found in the sludge. PMID:23141737
Erkan, M; Sanin, F D
Continuous high-solids anaerobic co-digestion of organic solid wastes under mesophilic conditions
Highlights: > High-solids (dry) anaerobic digestion is attracting a lot of attention these days. > One reactor was fed with food waste (FW) and paper waste. > Maximum biogas production rate of 5.0 m{sup 3}/m{sup 3}/d was achieved at HRT 40 d and 40% TS. > The other reactor was fed with FW and livestock waste (LW). > Until a 40% LW content increase, the reactor exhibited a stable performance. - Abstract: With increasing concerns over the limited capacity of landfills, conservation of resources, and reduction of CO{sub 2} emissions, high-solids (dry) anaerobic digestion of organic solid waste (OSW) is attracting a great deal of attention these days. In the present work, two dry anaerobic co-digestion systems fed with different mixtures of OSW were continuously operated under mesophilic conditions. Dewatered sludge cake was used as a main seeding source. In reactor (I), which was fed with food waste (FW) and paper waste (PW), hydraulic retention time (HRT) and solid content were controlled to find the maximum treatability. At a fixed solid content of 30% total solids (TS), stable performance was maintained up to an HRT decrease to 40 d. However, the stable performance was not sustained at 30 d HRT, and hence, HRT was increased to 40 d again. In further operation, instead of decreasing HRT, solid content was increased to 40% TS, which was found to be a better option to increase the treatability. The biogas production rate (BPR), CH{sub 4} production yield (MPY) and VS reduction achieved in this condition were 5.0 m{sup 3}/m{sup 3}/d, 0.25 m{sup 3} CH{sub 4}/g COD{sub added}, and 80%, respectively. Reactor (II) was fed with FW and livestock waste (LW), and LW content was increased during the operation. Until a 40% LW content increase, reactor (II) exhibited a stable performance. A BPR of 1.7 m{sup 3}/m{sup 3}/d, MPY of 0.26 m{sup 3} CH{sub 4}/g COD{sub added}, and VS reduction of 72% was achieved at 40% LW content. However, when the LW content was increased to 60%, there was a significant performance drop, which was attributed to free ammonia inhibition. The performances in these two reactors were comparable to the ones achieved in the conventional wet digestion and thermophilic dry digestion processes.
Kim, Dong-Hoon [Wastes Energy Research Center, Korea Institute of Energy Research, 102, Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Oh, Sae-Eun, E-mail: email@example.com [Department of Environmental Engineering, Hanbat National University, San 16-1, Duckmyoung-dong, Yuseong-gu, Daejeon (Korea, Republic of)
Dry Anaerobic Co-digestion of Cow Dung with Pig Manure for Methane Production.
The performance of dry anaerobic digestions of cow dung, pig manure, and their mixtures into different ratios were evaluated at 35?�?1��C in single-stage batch reactors for 63�days. The specific methane yields were 0.33, 0.37, 0.40, 0.38, 0.36, and 0.35�LCH4/gVSr for cow dung to pig manure ratios of 1:0, 4:1, 3:2, 2:3, 1:4, and 0:1, respectively, while volatile solid (VS) and chemical oxygen demand (COD) removal efficiencies were 48.59, 50.79, 53.20, 47.73, 46.10, and 44.88�% and 55.44, 57.96, 60.32, 56.96, 53.32, and 50.86�%, respectively. The experimental results demonstrated that the co-digestions resulted in 5.10-18.01�% higher methane yields, 2.03-12.95�% greater VS removals, 2.98-12.52�% greater COD degradation and so had positive synergism. The various mixtures of pig manure with cow dung might persuade a better nutrient balance and dilution of high ammonia concentration in pig manure and therefore enhanced digester performance efficiency and higher biogas yields. The dry co-digestion of 60�% cow dung and 40�% pig manure achieved the highest methane yield and the greatest organic materials removal efficiency than other mixtures and controls. PMID:24818871
Li, Jianzheng; Jha, Ajay Kumar; Bajracharya, Tri Ratna
Potential for methane production from anaerobic co-digestion of swine manure with winery wastewater.
This work examines the methane production potential for the anaerobic co-digestion of swine manure (SM) with winery wastewater (WW). Batch and semi-continuous experiments were carried out under mesophilic conditions. Batch experiments revealed that the highest specific methane yield was 348 mL CH(4)g(-1) COD added, obtained at 85.4% of WW and 0.7 g COD g(-1)VS. Specific methane yield from SM alone was 27 mL CH(4)g(-1) COD added d(-1). Furthermore, specific methane yields were 49, 87 and 107 mL CH(4)g(-1) COD added d(-1) for the reactors co-digesting mixtures with 10% WW, 25% WW and 40% WW, respectively. Co-digestion with 40% WW improved the removal efficiencies up to 52% (TCOD), 132% (SCOD) and 61% (VSS) compared to SM alone. These results suggest that methane can be produced very efficiently by the co-digestion of swine manure with winery wastewater. PMID:21232936
Ria�o, B; Molinuevo, B; Garc�a-Gonz�lez, M C
Anaerobic digestion of residual municipal solid waste using biological-mechanical pre-treatment: the plant of Varennes Jarcy.
Residual municipal solid waste can be treated by anaerobic digestion after a sorting process in order to remove the unwanted materials. After a mechanical sorting the quality of the final compost can hardly cope with requirements for agriculture use. In this way, a more efficient sorting process using a specific equipment that provides a combined biological and mechanical effect, has been implemented on the plant of Varennes Jarcy prior to anaerobic digestion. This paper presents the main results obtained on this plant. The reduction of biodegradable organics in particle lower than 10 mm allows a very efficient separation by screening. An additional ballistic sorting removes the remaining glass. The composition of the resulting sorted waste was close to a source-sorted organic fraction. The sorted waste exhibit methane yields comparable with raw biodegradable organics, showing that the pre-treatment had little impact on anaerobic digestion performance. PMID:18957758
Fruteau de Laclos, H; Thiebaut, E; Saint-Joly, C
Improving methane production and phosphorus release in anaerobic digestion of particulate saline sludge from a brackish aquaculture recirculation system.
In this study, batch tests were conducted to examine the effects of trehalose and glycine betaine as well as potassium on the specific methanogenic activity (SMA), acid and alkaline phosphatase activity of anaerobic biomass and phosphorus release in anaerobic digestion of saline sludge from a brackish recirculation aquaculture system. The results of ANOVA and Tukey's HSD (honestly significant difference) tests showed that glycine betaine and trehalose enhanced SMA of anaerobic biomass and reactive phosphorus release from the particulate waste. Moreover, SMA tests revealed that methanogenic sludge, which was long-term acclimatized to a salinity level of 17g/L was severely affected by the increase in salinity to values exceeding 35g/L. Addition of compatible solutes, such as glycine betaine and trehalose, could be used to enhance the specific methane production rate and phosphorus release in anaerobic digestion from particulate organic waste produced in marine or brackish aquaculture recirculation systems. PMID:24785791
Zhang, Xuedong; Ferreira, Rui B; Hu, Jianmei; Spanjers, Henri; van Lier, Jules B
Profile of hydrolases and biogas production during two-stage mesophilic anaerobic digestion of solid potato waste
Two two-stage systems, one consisting of a solid-bed reactor for hydrolysis\\/acidification connected to an upflow anaerobic sludge blanket methanogenic reactor, and the other consisting of a solid-bed reactor connected to a methanogenic reactor packed with wheat straw biofilm carriers, were investigated with regard to hydrolytic enzymes and methane production during mesophilic anaerobic digestion of solid potato waste. Some of the
W. Parawira; M. Murto; J. S. Read; B. Mattiasson
Phylogenetic description of immobilized methanogenic community using real-time PCR in a fixed-bed anaerobic digester
After immobilization of anaerobes on polyurethane foam in a thermophilic, fixed-bed, anaerobic digester supplied with acetate, the results of real-time PCR analysis indicated that the major immobilized methanogenic archaea were Methanosarcina spp., and that the major free-living methanogenic archaea were Methanosarcina and Methanobacterium spp. 16S rRNA gene densities of Methanosarcina spp. and Methanobacterium spp. immobilized on the polyurethane foam were
S. Sawayama; K. Tsukahara; T. Yagishita
Suitability of anaerobic digestion effluent as process water for corn fuel ethanol fermentation.
A corn fuel ethanol plant integrated with anaerobic digestion treatment of thin stillage increases the net energy balance. Furthermore, the anaerobic digestion effluent (ADE) can be reused as a potential substitute for process water in the ethanol fermentation. In this study, the suitability of ADE as process water for corn ethanol fermentation was investigated by analyzing the potential inhibitory components in the ADE. It was found that ammonium influenced the growth and metabolism of Saccharomyces cerevisiae. Maximum ethanol production was obtained when the concentration of ammonium nitrogen was 200 mg/L, and ammonium could replace urea as the nitrogen source for S. cerevisiae under this concentration. In the ethanol fermentation with a higher concentration of ammonium, more glycerol was produced, thereby resulting in the decrease of ethanol production. In addition, components except ammonium in the ADE caused no inhibition to ethanol production. These results suggest that ADE could be reused as process water for corn ethanol fermentation without negative effect when ammonium concentration is well controlled. PMID:24804665
Wang, Ke; Zhang, Jian-Hua; Liu, Pei; Mao, Zhong-Gui
Concentration of pig slurry by evaporation: anaerobic digestion as the key process.
Nutrient redistribution between areas with a structural pig slurry surplus and those with a shortage, is limited by the high cost of transportation and spreading, due to the high water content in slurry (more than 90%) and its relative low nutrient concentration. Water can be removed from slurry by evaporation, through the application of waste heat from a power plant or from other processes. Apart from obtaining a concentrate with an obviously higher nutrient concentration than the original slurry, another objective is to obtain clean water as condensate. The objective of this work was to study the batch vacuum evaporation of pig slurry liquid fraction, to evaluate the economic feasibility and to evaluate condensate quality as a function of both pH (4, 5 and 6) and pig slurry type (fresh slurry and anaerobically digested slurry). Results showed that condensate characteristics (ammonia nitrogen, VFA, COD) were strongly dependent on these variables. Previous anaerobic digestion presented clear advantages: it provided a fraction of the required energy and it removed organic matter, preventing its volatilisation in the evaporation process and providing higher quality condensates. These advantages make the combined treatment strategy economically more feasible than the evaporation process alone. PMID:14531439
Bonmat�, A; Campos, E; Flotats, X
Sequential extraction of anaerobic digestate sludge for the determination of partitioning of heavy metals.
In China, agricultural use of anaerobic digestate sludge is considered a concern due to high heavy metal content of the sludge. In this study, sequential extraction procedure (SEP) was conducted to determine metal speciation which affects release and mobility of metal significantly. The results of SEP showed that each heavy metal possessed different distribution characteristics. Cu mainly reacted with carboxyl functional group to form the fraction bound to organic matter. Zn and Mn were dominated in the fraction bound to Fe-Mn oxides and carbonates, respectively. Pb, Ni, Cr, Cd and As were present as the residual fraction. Examination of mobility factors (MFs) indicated that Zn, Pb, Ni, Mn and Cd were more mobile whereas Cr and As were immobilized in anaerobic digestate. Based on the results, it can be stated that Cu, Zn, Mn, Ni and Cd may be grouped as toxic and active components in sludge and should be regarded as the priority pollutants for elimination. Pb should be monitored in terms of its high mobility factors (MF). Cr and As, nevertheless, were the most stable components in sludge. PMID:24580817
Zhu, Neng-min; Qiang-Li; Guo, Xu-jing; Hui-Zhang; Yu-Deng
A critical review on inhibition of anaerobic digestion process by excess ammonia.
Ammonia plays a vital role in the performance and stability of anaerobic digestion (AD) of N-rich organic-feedstock. Several research works were carried-out to study the effect of ammonia on the efficiency of AD of agro-food, industrial and livestock wastes/wastewater. However, excess ammonia remains a critical hitch in AD process. The mechanism of ammonia-inhibition has also been studied and there is no simple strategy available to mitigate ammonia-toxicity, when it exceeds threshold inhibition-level. For successful operation of AD systems at higher ammonia-level, adequate choice of temperature, control of pH and C/N ratio, and utilization of acclimatized-microflora to higher ammonia concentrations may ensure a stable and undisturbed digestion. This review provides a critical summary of earlier and recent research conducted on ammonia-inhibition during the anaerobic degradation of organic substrates, especially, at high ammonia concentrations. This article emphasizes that more profound knowledge on parameters influencing ammonia-inhibition is needed to apply appropriate control strategies. PMID:23835276
Rajagopal, Rajinikanth; Mass�, Daniel I; Singh, Gursharan
High-solid anaerobic digestion of sewage sludge under mesophilic conditions: feasibility study.
Feasibility of high-solid anaerobic digestion of sewage sludge was investigated in single-stage completely stirred tank reactors at 35�1 �C. System stability and the effect of organic loading rate (OLR), sludge retention time (SRT) and total solid (TS) content on the performance of high-solid system was examined. Experimental results showed that, with the concentration of free ammonia nitrogen (FAN) lower than 600 mg l(-1), high-solid anaerobic digestion of sewage sludge could maintain satisfactory stability. Slight, moderate and significant inhibition was found with FAN concentration ranging from 250 to 400, 400 to 600 and 600 to 800 mg l(-1), respectively. The VFA/TA criteria could not foresee system instability in significant ammonia inhibition system by its traditional ratio grades. High-solid system could support higher OLR (4-6 times as high) and obtain similar methane yield and VS reduction as conventional low-solid system at the same SRT, thus reach much higher volumetric methane production rate. PMID:22104097
Duan, Nina; Dong, Bin; Wu, Bing; Dai, Xiaohu
Effects of ultrasonic pretreatment on sludge dewaterability and extracellular polymeric substances distribution in mesophilic anaerobic digestion.
Effect of ultrasonic pretreatment on sludge dewaterability was determined and the fate of extracellular polymeric substances (EPS) matrix in mesophilic anaerobic digestion after ultrasonic pretreatment was studied. Characteristics of proteins (PN), polysaccharides (PS), excitation-emission matrix (EEM) fluorescence spectroscopy and molecular weight (MW) distribution of dissolved organic matters (DOM) in different EPS fractions were evaluated. The results showed that after ultrasonic pretreatment, the normalized capillary suction time (CST) decreased from 44.4 to 11.1 (sec x L)/g total suspended solids (TSS) during anaerobic digestion, indicating that sludge dewaterability was greatly improved. The normalized CST was significantly correlated with PN concentration (R2 = 0.92, p < 0.01) and the PN/PS ratio (R2 = 0.84, p < 0.01) in the loosely bound EPS (LB-EPS) fraction. Meanwhile, the average MW of DOM in the LB-EPS and tightly bound EPS (TB-EPS) fractions also had a good correlation with the normalized CST (R2 > 0.66, p < 0.01). According to EEM fluorescence spectroscopy, tryptophan-like substances intensities in the slime, LB-EPS and TB-EPS fractions were correlated with the normalized CST. The organic matters in the EPS matrix played an important role in influencing sludge dewaterability. PMID:20614793
Shao, Liming; Wang, Guanzhao; Xu, Huacheng; Yu, Guanghui; He, Pinjing
Inhibitory effects of fruit flavors on methane production during anaerobic digestion.
In order to improve biogas production from fruit wastes, the inhibitory effects of fruit flavors on anaerobic digestion were investigated. Batch anaerobic digestion was performed for 30 days using synthetic medium and thermophilic sludge. Three groups of flavor compounds i.e. aldehydes (hexanal, nonanal, and E-2-hexenal), terpenes (car-3-ene, ?-pinene, and myrcene), and alcohol (octanol) at concentration of 0.005%, 0.05%, and 0.5% were examined. All the flavor compounds showed inhibitory effect on methane production. The highest methane reduction was obtained at addition of 0.5% of flavor compounds. For terpenoids, the presence of 0.5% of car-3-ene, myrcene, and ?-pinene reduced 95%, 75%, and 77% of methane production, respectively. For aldehydes, addition of 0.5% concentration resulted in more than 99% methane reduction for hexanal and E-2-hexenal, and 84% methane reduction for nonanal. For alcohol, the presence of 0.5% octanol decreased 99% methane production. PMID:23422220
Wikandari, Rachma; Gudipudi, Sailaja; Pandiyan, Ishwarya; Millati, Ria; Taherzadeh, Mohammad J
Effects of lipid concentration on anaerobic co-digestion of municipal biomass wastes.
The influence of the lipid concentration on the anaerobic co-digestion of municipal biomass waste and waste-activated sludge was assessed by biochemical methane potential (BMP) tests and by bench-scale tests in a mesophilic semi-continuous stirred tank reactor. The effect of increasing the volatile solid (VS) concentration of lipid from 0% to 75% was investigated. BMP tests showed that lipids in municipal biomass waste could enhance the methane production. The results of bench-scale tests showed that a lipids concentration of 65% of total VS was the inhibition concentration. Methane yields increased with increasing lipid concentration when lipid concentrations were below 60%, but when lipid concentration was set as 65% or higher, methane yields decreased sharply. When lipid concentrations were below 60%, the pH values were in the optimum range for the growth of methanogenic bacteria and the ratios of volatile fatty acid (VFA)/alkalinity were in the range of 0.2-0.6. When lipid concentrations exceeded 65%, the pH values were below 5.2, the reactor was acidized and the values of VFA/alkalinity rose to 2.0. The amount of Brevibacterium decreased with increasing lipid content. Long chain fatty acids stacked on the methanogenic bacteria and blocked the mass transfer process, thereby inhibiting anaerobic digestion. PMID:24075452
Sun, Yifei; Wang, Dian; Yan, Jiao; Qiao, Wei; Wang, Wei; Zhu, Tianle
Utilisation of wastewater nutrients for microalgae growth for anaerobic co-digestion.
The feasibility of growing microalgae in natural light using wastewater high in nutrients (N & P) for the production of more bioenergy was examined. The main retrofitting unit would be a photobioreactor for wastewater treatment plants (wwtp) having anaerobic digesters in close proximity. Theoretical microalgae production rates from different wastewater sources (municipal wwtp, source separation of human and animal wastewaters) were estimated using mass balance. Mass and energy balances for a conventional wwtp using chemically enhanced primary treatment was investigated for microalgae growth for a situation limited by availability of carbon dioxide (CO2) generated onsite and where additional CO2 was imported from outside source. Reject water from dewatering of anaerobically digested sludge from four wwtp around Oslo region were pretreated for improved light penetration and examined for microalgae growth. Several pre-treatment methods were investigated. Pretreatment using flocculation + settling + anthracite filtration yielded high light transmittance. A maximum microalgae growth rate of 13 g TSS/m(2)-d was achieved using this pretreated reject water. The challenges of integrating photobioreactors with existing units have been highlighted. PMID:23570973
Sahu, Ashish K; Siljudalen, Jon; Trydal, Tina; Rusten, Bj�rn
A multi-criteria ranking of different technologies for the anaerobic digestion for energy recovery of the organic fraction of municipal solid wastes
This paper describes a conceptual framework and methodological tool developed for the evaluation of different anaerobic digestion technologies suitable for treating the organic fraction of municipal solid waste, by introducing the multi-criteria decision support method Electre III and demonstrating its related applicability via a test application. Several anaerobic digestion technologies have been proposed over the last years; when compared to
A. Karagiannidis; G. Perkoulidis
Effect of microwave pretreatment in presence of NaOH on mesophilic anaerobic digestion of thickened waste activated sludge.
This work experimentally determined the effect of microwave irradiation with NaOH pretreatment on anaerobic digestion of thickened waste activated sludge in semi-continuous mesophilic digesters at hydraulic retention times (HRT) of 15, 10, 7, and 5 days. The degree of substrate solubilization was 18 times higher in pretreated sludge (53.2%) than in raw sludge (3.0%). Removal efficiency of volatile solid in digesters fed with raw (control) and pretreated sludges (PD) decreased as HRT reduced. The highest relative improvement of properties compared with the control occurred at 5 day HRT. Improvements in biogas production compared with the control increased in the PD as HRT was reduced to 5 days (205% higher at 5 days). However, digested sludges in the control and PD increased capillary suction time compared with raw sludge. The results show that microwave irradiation combined with alkali pretreatment is effective in increasing mesophilic anaerobic biodegradability of sewage sludge. PMID:23376834
Effect of natural zeolite on methane production for anaerobic digestion of ammonium rich organic sludge.
The effect of an inorganic additive on the methane production from NH(4+)-rich organic sludge during anaerobic digestion was investigated using different kinds of inorganic adsorbent zeolites (mordenite, clinoptilolite, zeolite 3A, zeolite 4A), clay mineral (vermiculite), and manganese oxides (hollandite, birnessite). The additions of inorganic materials resulted in significant NH4+ removals from the natural organic sludge ([NH4+]=1, 150 mg N/l), except for the H-type zeolite 3A and birnessite. However, an enhanced methane production was only achieved using natural mordenite. Natural mordenite also enhanced the methane production from the sludge with a markedly high NH4+ concentration (4500 mg N/l) during anaerobic digestion. Chemical analyses of the sludge after the digestion showed considerable increases in the Ca2+ and Mg2+ concentrations in the presence of natural mordenite, but not with synthetic zeolite 3A. The effect of Ca2+ or Mg2+ addition on the methane production was studied using Na(+)-exchanges mordenite and Ca2+ or Mg(2+)-enriched sludge. The simultaneous addition of Ca2+ ions and Na(+)-exchanged mordenite enhanced the methane production; the amount of produced methane was about three times greater than that using only the Na(+)-exchanged mordenite. In addition, comparing the methane production by the addition of natural mordenite or Ca2+ ions, the methane production with natural mordenite was about 1.7 times higher than that with only Ca2+ ions. The addition of 5% and 10% natural mordenite were suitable condition for obtaining a high methane production. These results indicated that the Ca2+ ions, which are released from natural mordenite by a Ca2+/NH4+ exchange, enhanced the methane production of the organic waste at a high NH4+ concentration. Natural mordenite has a synergistic effect on the Ca2+ supply as well on the NH4+ removal during anaerobic digestion, which is effective for the mitigation of NH4+ inhibition against methane production. PMID:15491827
Tada, Chika; Yang, Yingnan; Hanaoka, Toshiaki; Sonoda, Akinari; Ooi, Kenta; Sawayama, Shigeki
Inhibitory effects of ammonia on methanogen mcrA transcripts in anaerobic digester sludge.
Methanogens in anaerobic ammonia-rich digesters show differential responses to ammonia stress. The mechanism for this is poorly understood. In the present study, we determined the rates of methane production, the composition of methanogen mcrA (the gene coding for the alpha subunit of methyl-coenzyme M reductase) and their transcripts in response to ammonium addition in the anaerobic sludge retrieved from a full-scale digester treating swine manure. The rate of CH4 production substantially reduced with increased addition of ammonium. The analysis of natural (13) C abundances of CH4 and CO2 indicated that the aceticlastic methanogenesis was more sensitive than hydrogenotrophic methanogenesis. Quantitative PCR analysis revealed that mcrA copy number decreased by one order of magnitude in the treatment with a large amount of ammonium (10�g�NH4+-N�L(-1) ) but did not change much with treatments of smaller amounts (3 and 7�g�NH4+-N�L(-1) ) compared with the control. T-RFLP analysis of mcrA compositions showed that the structure of the methanogen community remained highly stable, with Methanosaetaceae dominating the methanogen community in all incubations. The composition of mcrA transcripts, however, showed a substantial response to the addition of ammonium. The relative abundance of Methanosaetaceae transcripts declined with increasing amounts of ammonium, whereas the transcript level of Methanobacteriales mcrA was relatively resistant. The differential responses corresponded to the shift of methanogenic pathway inferred from (13) C isotope fractionation. Our study suggests that methanogens in anaerobic sludge have a strong mcrA transcriptional response to ammonia stress without a change in the community structure. PMID:24117957
Zhang, Chen; Yuan, Quan; Lu, Yahai
Evaluation of biodegradability of phenol and bisphenol A during mesophilic and thermophilic municipal solid waste anaerobic digestion using 13C-labeled contaminants.
In this paper, the isotopic tracing using (13)C-labeled phenol and bisphenol A was used to study their biodegradation during anaerobic digestion of municipal solid waste. Microcosms were incubated anaerobically at 35 �C (mesophilic conditions) and 55 �C (thermophilic conditions) without steering. A continuous follow-up of the production of biogas (CH(4) and CO(2)), was carried out during 130 d until the establishment of stable methanogenesis. Then (13)C(12)-BPA, and (13)C(6)-phenol were injected in microcosms and the follow-up of their degradation was performed simultaneously by gas chromatography isotope-ratio mass spectrometry (GC-IRMS) and gas chromatography mass spectrometry (GC-MS). Moreover, Carbon-13 Nuclear Magnetic Resonance ((13)C-NMR) Spectroscopy is used in the identification of metabolites. This study proves that the mineralization of phenol to CO(2) and CH(4) occurs during anaerobic digestion both in mesophilic and thermophilic conditions with similar kinetics. In mesophilic condition phenol degradation occurs through the benzoic acid pathway. In thermophilic condition it was not possible to identify the complete metabolic pathway as only acetate was identified as metabolite. Our results suggest that mineralization of phenol under thermophilic condition is instantaneous explaining why metabolites are not observed as they do not accumulate. No biodegradation of BPA was observed. PMID:22985591
Limam, Intissar; Mezni, Mohamed; Guenne, Ang�line; Madigou, C�line; Driss, Mohamed Ridha; Bouchez, Th�odore; Maz�as, Laurent
Anaerobic co-digestion of excess brewery yeast in a granular biomass reactor to enhance the production of biomethane.
The anaerobic co-digestion of brewery yeast using granular biomass was studied on the lab, pi