Startup and Commissioning of a Full-Scale Selenium Treatment Facility for Mine Water Treatment

A 4 MGD (2,800 gpm) biological fluidized bed reactor (FBR) based water treatment plant (WTP) was commissioned at a confidential North American mine facility in 2013 to meet effluent discharge limits for selenium and other conventional parameters. This water treatment plant is the first of its kind for selenium removal from mine water. Mine waters from three (3) different sources with varying selenium and nitrate loadings are combined prior to treatment at this plant. The primary process train consisted of FBRs for facilitating anoxic/anaerobic reduction of selenite/selenate to elemental selenium followed by ballasted sand clarifiers for the removal of solids from the FBR effluent including elemental selenium and the biomass. The next step in the process is an aerobic moving bed biofilm reactor (MBBR) for removal of residual organics and to increase the dissolved oxygen (DO) prior to discharge. Once stable operations were reached during startup, the plant was able to consistently meet the selenium limit. An analysis of the plant performance along with challenges faced during startup and commissioning of this plant are discussed.