Opinion of the scientific panel on contaminants in the food chain on perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) and their salts. 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).I acknowledge that is a lot of pfaff.but your question was rather open-ended. We add the individual redox equations together in a way to eliminate the electrons, which are particles of convenience.And so we take #(i) + 2xx(ii)#: Is this balanced with respect to mass and charge? It must be if we purport to represent physical reality.Īnd, inevitably, something must be reduced to effect the oxidation let's say it is oxygen. Consider the oxidation of ammonia to give nitrate ion.in terms of formal oxidation state this is the transition, #stackrel(-III)N# to #stackrel(+V)N#, an 8 electron oxidation, which we formally represent in the equation. balance, a chemical equation, with respect to mass and charge, #"redox equations"#, straightforwardly and systematically (says he, #"modelling a modern major general"#.)Īnd so we can interpret a given chemical reaction with the use of oxidation numbers. And when we assign oxidation numbers, we use them to solve, i.e. The rules for assignment of oxidation numbers are given here.Īs given, #"oxidation number"# and #"oxidation state"# are FORMALISMS, they are convenient fictions that may nevertheless have a practical use.
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