69cf3305_bstracts___IEEE_GreenTech_2013__Category____Sub_Category
[Paper Title, Abstract] Biogas Generation from a 2-Phase Sludge Treatment System Show AbstractHide Abstract Anaerobic digestion is widely used for treatment of excess sludge from sewage plants to produce biogas and reduce biosolids content. The process typically comprises the hydrolysis, acidogenesis, and methanogenesis phases. The acid formers prefer an acidic environment and are fast growing while methane formers prefer a neutral pH or higher environment and are slow growing; therefore, it is a challenge to optimize the activities of the two microbial communities in the single stage anaerobic reactor. Waste activated sludge also has relatively low biodegradability and the single stage system operated under long HRT (about 30 days) can typically only achieve up to 40% VS reduction efficiency. The two phase process spatially separates the hydrolysis/acidogenesis phases from the acetogenesis/methanogenesis phase to achieve higher organic stabilization, and more gas production. While there have been reports of sewage sludge digestion in 2-phase systems compared with the conventional single stage system, the results have not been consistent. While higher VS reduction and gas yield in the 2-phase system was demonstrated, other researchers have reported the increase in VS reduction in a 2-phase system fed with 1:1 primary and waste sludge was only 1.9-6%. Therefore before commitment to full scale application, it is necessary to investigate digestion of sewage sludge in the single stage and 2-phase anaerobic systems to determine performance and to reinforce the findings to simultaneously explore the microbial community profiles in the two systems to determine differences if any. The degradation of sewage sludge in single stage and 2 phase anaerobic systems was investigated in bench-scale batch reactors. Average COD reduction efficiency in 2 phase system in this initial phase of the study was 4.5% (30 days HRT) and 3.3% (20 days HRT) higher compared to single stage system. Reducing the HRT from 30 days to 20 days had little influence in VS reduction in the two systems. The average methane content in the biogas was 61.8%, 66.5%, and 64.8% (30 days HRT) in acid reactor, methane reactor and single stage reactor, respectively, and the corresponding values were 57.7%, 66.5% and 64.9% at 20 days HRT. The microbial community analyzed by qPCR using primer/probes specific for orders of Archaea involved in methanogenesis showed that hydrogen and acetate utilizing methanogens were present in all the reactors, but relative abundance of methanogens in the acid reactor was lower compared to the methane and single stage reactors. Reducing the HRT from 30 days to 20 days decreased the relative abundance of methanogens and changed the methanogen community structure. [Schedule] TTM-GWRB [Category :: Sub-Category] 
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