In the past, cost-effective, efficient, off-the-shelf, technology has not been available for selenium removal from large volumes of water. Conventional treatments can produce unwanted metal waste products and are subject to greater fluctuations in removal efficiencies. The EBR techhnology uses low voltage to virtually eliminate fluctuations due to seasonal and other changes in water chemistry. Elemental selenium is precipitated and removed from the wastewaters as it is fed through the sytem. The EBR technology has been successfully demonstrated to remove selenium from difficult to treat mining and mineral processing wastewaters from metal and coal mines.
EBR Selenium Removal
Process water comparisons with a two stage conventional bioreactor system and a single stage EBR. Retention times were 12 hours in the EBR and 24 hours in the conventional 2-stage reactor. All reactors were operated under conditions that approximated plug flow (up flow). EBR’s were operated at 3 volts (no current). All other conditions in the CBR and EBR stages were identical. (Note: Microbial populations in the EBR’s were higher and more robust due to the easy availability of electrons [energy] in the EBR systems –EBR reactors received 1/2 the nutrient of the CBR's EBR1 effluent averaged 0.05 mg/L with feed waters averaging 4.35 mg/L selenium. In a second test a second EBR stage, EBR2 , produced effluents below detection of 0.001 mg/L when tested with selenium containing mine wastewaters containing selenium ranging from 0.250 mg/L Se to up to 15.2 mg/L selenium. All analysis used ICP-MS.