| Summary: | As more is learned about selenium toxicity, increasingly stringent discharge levels make selenium another potential concern for mine closures. Biological treatment of selenium has been used successfully and offers the possibility of a low-cost, low-input means of treatment. However, a thorough understanding of the processes involved is crucial to an effective design. There are several biological processes which can
remove selenium from a water column, including volatilization, sequestration, and bacterial reduction. Bacterial reduction of selenate and selenite oxyanions appears to be the key process in removing selenium from aquatic systems. Two case studies of biological treatment are presented, with an emphasis on the design approach and how preliminary benchscale tests contributed to an understanding of the processes being designed for. Removal rates of 88% and 96% were obtained in the laboratory tests.
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