reaction chamber before the vapor flows over the packing media. The biological packing media may be natural or made of synthetic plastic. Recirculation of the water is always completed in the biological oxidation system to make the system more cost-effective. Biochemical oxygen demand (BOD) indirectly measures the amount of easily biodegradable organic matters thus very low values indicate direct waste water disposal. The prompt removal of a wide range of wastes and pollutants from the waste gas flow is the foremost requirement of biological oxidizers to meet regulatory permitting requirements. Micro-organisms differ in their ability to rapidly metabolize different pollutants, so the selection of the proper mix of organisms is critical. Research is underway to genetically modify various organisms to improve their performance in biological oxidation. Benefits of biological oxididation Biological oxidation of organic matters has led to the innovation of a low cost secondary treatment of the waste water emissions and industrial air emissions. The process of biodegradation offers a very fast method which typically offers 4,000 catalytic cycles per minute. Destruction rate efficiency is generally greater than 99% on most biodegradable organics emissions. The biological oxidation technology is free from secondary emissions () with limited production. While other oxidation technologies such as thermal oxidation produces CO, NO2 and CO2. List of manufacturers The following manufacturers have been involved in the development, design and planning of waste gas purification systems for a wide range of industries: Global manufacture of turnkey systems. American Fabrication and Supply, LLC See also Bacteria Microbiology Microorganism References Further reading and external links McGrew, Roderick. Encyclopedia of Medical History (1985), brief history pp 25–30 Our Microbial Planet A free poster from the National Academy of Sciences about the positive roles of micro-organisms. "Uncharted Microbial World: Microbes and Their Activities in the Environment" Report from the American Academy of Microbiology Understanding Our Microbial Planet: The New Science of Metagenomics A 20-page educational booklet providing a basic overview of metagenomics and our microbial planet. Tree of Life Eukaryotes Microbe News from Genome News Network Medical Microbiology On-line textbook Through the microscope: A look at all things small On-line microbiology textbook by Timothy Paustian and Gary Roberts, University of Wisconsin-Madison Air pollution control systems Environmental engineering Pollution Pollution control technologies Bacteriology Chemical equipment