KSEF R&D Excellence: Biological Oxidation of Arsenite

The overall objective of the proposed study is to improve our understanding of arsenite oxidation by biological processes. 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. Arsenite (As(III» is soluble and very toxic, while arsenate (As(V» is less toxic and less soluble. Oxidation of arsenite to arsenate is generally required for the effective removal of arsenic from aqueous phase. Biological oxidation of As(III) does not require costly chemical agents and may not form harmful residuals and by-products as observed with the conventional chemical oxidation processes. 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 and arsenite oxidation in bioreactor systems has not been reported. The experimental evaluation will be initiated with selected bacterial species capable of As(III) oxidation. Batch studies will be conducted to screen cultures for their ability to oxidize As(III) when provided different growth substrates, and to assess the effect of environmental factors on the relative rates of As(III) oxidation. Batch studies will also be used to evaluate the relationship between substrate utilization rate, rate of As(III) oxidation, and rate of bacterial growth. Based on the batch studies, a continuous-flow bioreactor system will be used to more accurately examine the rate of As(III) oxidation and arsenic removal. Results obtained from the proposed study should be useful for designing biological processes for the removal of arsenic through gaining insights into both the kinetics and the physiological role of biological oxidation of arsenite. These information are needed for assessing the effectiveness of biological processes for arsenite oxidation. This research should also lead to improved risk management involving arsenic by presenting an alternative approach to the costly conventional technique.