Reduction of Sulfate Concentrations in Neutral Mine Effluent

Elevated concentrations of sulfate (500-4000 mg/L) exist in certain neutral drainages that contain reactive rock, but sufficient carbonate to neutralize the sulfuric acid produced. Due to concerns that sulfate may degrade surface water, cost-effective methods are required for reducing the contaminant load into these streams. This review examines methods primarily for sulfate removal, although selenium is very often simultaneously removed. The chemistry of selenium, particularly the redox chemistry, has distinctive similarities to sulfer, and reductive processes are known to reduce selenium to the insoluble elemental form. We have conducted limited column studies and noted that selenium removal can be very efficient under sulfate reducing conditions. However, site specific conditions may affect the efficiency of selenium removal, and additional testing will be necessary to establish success.