Evaluation of Anoxic Bioreactor Efficacy for Reducing Selenium Fish Tissue Accumulation in Mining Influenced Streams

Selenium is introduced into the environment through numerous anthropogenic sources, including mining of coal seams with elevated selenium concentrations, and upon introduction into aquatic ecosystems may bioaccumulate. Se is associated with reproductive impairments in fish, and USEPA has adopted Se criterion that includes concentrations in both the water column and fish tissue. Selenium is redox sensitive and speciation is based on numerous physical and biological processes and it exists in a number of oxidation states, including selenide (Se(-II)), elemental selenium (Se), selenite (Se(IV)), selenate (Se(VI)) and several organic and volatile Se compounds. Limits on the discharge of Se in mining discharges has compelled the industry to adopt various treatment techniques, including the use of anoxic bioreactors to reduce the oxidized Se species to elemental Se, which subsequently precipitates. This study uses mining industry data to analyze the efficacy of bioreactor use for Se treatment and Se fish tissue concentrations in receiving streams.