574 pp.ĮFSA (European Food Safety Authority). Draft Toxicological Profile for Perfluoroalkyls. References: ATSDR (Agency for Toxic Substances and Disease Registry). EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal. Cometabolic dechlorination does not appear to produce energy for the organism. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Anaerobic dechlorination also may occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In anaerobic metabolism, nitrate, sulfate, carbon dioxide, oxidized metals, or organic compounds may replace oxygen as the electron acceptor. Depending on the contaminant of concern, a subset of these activities may be cultivated. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated SitesĪnaerobic: Direct anaerobic metabolism involves microbial reactions occurring in the absence of oxygen and encompasses many processes, including fermentation, methanogenesis, reductive dechlorination, sulfate-reducing activities, and denitrification. 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. For aerobic cometabolism to occur there must be sufficient oxygen and a suitable substrate which allows the microbe to produce the appropriate enzyme. 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)).Īerobic dechlorination may also occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. 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. The bacteria uses a carbon substrate as the electron donor and oxygen as the electron acceptor. Technical and Technology Support ServicesĪerobic: Direct aerobic metabolism involves microbial reactions that require oxygen to go forward.Measurement and Monitoring Technologies for the 21st Century (21M 2).Federal Remediation Technologies Roundtable. Triad: A Smarter Solution to Site Cleanup.High-Resolution Site Characterization (HRSC).Global Efforts to Advance Remediation at Contaminated Sites.Polycyclic Aromatic Hydrocarbons (PAHs).Per- and Polyfluoroalkyl Substances (PFAS).Dense Nonaqueous Phase Liquids (DNAPLs).Going forward, Anaheim will continue to monitor its water for Chrome-6 and will ensure that all of its sources meet all drinking water standards. Data from Orange County suggests that low levels of Chrome-6 are common in this area due to the natural geology and Anaheim’s Chrome-6 levels are similar to those found throughout the County. Anaheim's groundwater has average Chrome-6 levels of approximately 0.7 ppb. Since monitoring first began in 2001, Chrome-6 has been found in most of our active production wells at levels ranging from the laboratory detection level of 0.2 parts per billion to a high of 3.3 ppb. When Chrome-6 first became an issue following the Erin Brokovich movie, all of Anaheim’s wells were tested. According to the State, the new MCL will reduce statewide cancer cases by 12 each year and would cost about $155 million annually in water treatment costs.Īnaheim has been monitoring its water supplies for many years for Total Chromium and has rarely detected it. In July 2014 California established a Maximum Contaminant Level (MCL) of 10 ppb for Chrome-6. Chrome-6 has always been regulated as part of the drinking water standard for Total Chromium, but it is now being regulated on its own. Human caused contamination can also occur due to releases from various industrial processes. Chrome-6 is often present at very low levels in groundwater due to its occurrence in certain geological formations. Hexavalent chromium, also known as Chrome-6, is a form of the element chromium that is suspected to pose a human health risk if ingested.
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