Trichloroethylene structure

aerobic: Direct aerobic metabolism involves microbial reactions that require oxygen to go forward. The bacteria uses a carbon substrate as the electron donor and oxygen as the electron acceptor. Degradation of contaminants that are susceptible to aerobic degradation but not anaerobic often ceases in the vicinity of the source zone because of oxygen depletion. This can sometimes be reversed by adding oxygen in the form of air (air sparging, bioventing), ozone, or slow oxygen release compound (e.g., ORC(r)). Aerobic dechlorination may also occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal. For aerobic cometabolism to occur there must be sufficient oxygen and a suitable substrate which allows the microbe to produce the appropriate enzyme. These conditions may be present naturally but often in the presence of a source area oxygen and a substrate such as methane or propane will need to be introduced. Adapted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites anaerobic: Direct anaerobic metabolism involves microbi...

The Frank R. Lautenberg Chemical Safety for the 21 st Century Act amends the EPA selected the first 10 chemicals to undergo risk evaluation under the amended TSCA and to make those understandable for the public, the American Council on Science and Health is producing risk-based evaluations of each, which will then be compiled into a free downloadable book for consumers. What is Trichloroethylene (TCE)? Trichloroethylene (TCE) is a colorless, volatile liquid that is nonflammable and has a sweet odor. It evaporates quickly into the air, but can also be found in water and soil. It is used as a solvent to remove greases, oils, fats, waxes, and tars from metal parts, and is also used to clean cotton, wool, and other fabrics. It is also a component of adhesives, lubricants, paints, varnishes, paint strippers, pesticides, and cold metal cleaners. In the past it was used as a food extraction solvent for natural fats and oils, the decaffeination of coffee, and for cosmetic and drug products. The Exposure to TCE The US Agency for Toxic Substances and Disease Registry (ATSDR) of 2014 states that TCE is commonly found in outdoor air at levels far less than 1 part per million (ppm) but levels as high as about 0.02 ppm have sometimes been measured inside homes and in public places. In workplace air at facilities that use TCE for metal degreasing, it has been measured from 1 ppm up to 100 ppm but it is not chemically stable in air and is broken down quickly. TCE has also been found in dr...