Removing selenite from groundwater with an in situ biobarrier: laboratory studies

Laboratory biobarriers were evaluated for their ability to remove selenite from flowing groundwater. Microbial activity in aquifers is usually limited by substrate availability, and biobarriers stimulate microbial activity by providing a substrate; for these studies soybean oil was used. Water containing 10 mg L(-1) selenite-Se was pumped through the biobarriers for 74 days and the amount present in the effluent monitored. The amounts remained high for the first 2 weeks of the study but then declined. From day 28 until the end of the study the amount of selenite-Se in the column effluents averaged 0.20 +/- 0.04 mg L(-1), a decrease of approximately 98%. At the end of the study about half of the selenite-Se applied to the columns was recovered as immobilized selenium trapped by the biobarrier. This study suggests that biobarriers containing vegetable oil might be used as a process for removing selenite from contaminated groundwater.