SELENIUM, URANIUM, AND NITRATE: TREATMENT OF TROUBLESOME CONTAMINANTS IN MINING WASTEWATERS – EBR CASE STUDIES

Abstract: Selenium (Se), uranium (U), and nitrate (NO3) are widespread in many North American mining environments and related industrial waters. These contaminants are often particularly difficult or expensive to remove using conventional water treatment methods, such as chemical coagulation/precipitation, reverse osmosis filtration, ion exchange, etc. Treatment system capital and operating expenses combined with additional costs of sludge or concentrate stream disposal, are driving research and application of biotreatment methods for removal of these contaminants from mining and industrial wastewaters. This paper discusses application of the Electro-Biochemical Reactor (EBR) technology for Se, U, and NO3 bio-reduction and removal from mining wastewaters. Three case studies are presented, based on laboratory benchand onsite pilot-scale trials with significantly different mining waters (flotation-influenced base metals mine water, leach solution from a gold mine, and coal mine seepage water), each contaminated with varying concentrations of Se, U, and NO3. Average concentrations of these contaminants were 2,712 μg L Se, 2.0 μg L U, and 1.53 mg L NO3-N (Site A); 2.9 μg L -1 Se, 92.5 μg L U, and 189 mg L NO3-N (Site B); and 105 μg L Se, 18.4 μg L U, and 50 mg L NO3-N (Site C). The EBR technology was demonstrated on all three sites to treat the waters to <0.5 – 3.2 μg L Se, <0.1 – 0.8 μg L U, and <0.02 – <2 mg L NO3-N.