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Biological Oxidation of Arsenite
University of Kentucky The overall objective of the proposed study is to improve our understanding of biological oxidation of arsenite. Arsenic is ubiquitous in the environment and has both natural and anthropogenic sources. Anthropogenic activity contributes to the accumulation of arsenic in a large extent, mainly due to the exploitation and smelting of metalliferous ores, burning of fossil fuels, and agricultural activities. As(III) is very toxic and is carcinogenic and mutagenic in animals and man. As(V), on the other hand, is far less toxic and less soluble. Oxidation of arsenite to arsenate is generally required for the effectively removal of arsenic from aqueous phase. The proposed study will conduct research on arsenite oxidation using both pure and defined mixed bacterial cultures.The experimental evaluation will be initiated with arsenite-oxidizing organisms isolated from arsenite-contaminated sites. Batch studies will be used to screen cultures for their ability to oxidize As(III) when provided different growth substrates. The effect of the following variables on relative rates of As(III) oxidation will be evaluated: type of growth substrate, effect of dissolved oxygen level, As(III) concentration, temperature, and bacterial species and density. Biological oxidation of As(III) does not require costly chemical agents and does not form harmful residuals and by-products from chemical oxidation. Biological transformation of As(III), therefore, has real potential for solving environmental problems of great significance. Biological transformation of As(III) to As(V) has been observed but the effect of environmental conditions on the rate and extent of arsenite oxidation is not yet clear. Results obtained from the proposed study should be useful for designing treatment processes for the removal of arsenic by biological activities. The research should lead to improved risk management involving arsenic by presenting an alternative approach to the costly conventional technique. The ultimate goal is to develop alternative removal and bioremediation techniques for arsenic contaminated soils, mining refuse, sediments, and groundwater.
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