Bacterial sulfate reduction is a naturally occurring process that proceeds only in the absence of oxygen and in the presence of sufficient organic carbon and sulfate. The net byproducts of sulfate reduction, hydrogen sulfide and bicarbonate, can precipitate metal sulfides and neutralize acidic water, respectively. An experimental wetland was designed and built to maximize contact between mine drainage and the anaerobic zone of the organic substrate, where sulfate reduction takes place. Preliminary results from the wetland were encouraging. Iron concentrations decreased from 237 to 27 mg l-1, ph increased from 2.9 to 6.5, and alkalinity increased from 0 to 1,077 mg l-1 when the mine drainage was forced through the anaerobic zone. The observed improvement in water quality was due to the inherent chemical characteristics of the organic substrate as well as to bacterial activity. Bacterial sulfate reduction rates in the organic substrate ranged from 0.002 to 0.6 Mmol/l-sediment/day. Sulfate reduction rates are high enough to significantly affect the water quality of acid mine drainage. Minor modifications to existing wetland designs may improve the efficiency of water treatment by incorporating anaerobic bacterial processes.
Biohydrometallurgy--'89: Proceeds '89 Intl Symp. Biohydro. Canmet, Ottawa, Ontario, PP. 627-41