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 by the U.S. Bureau of Mines 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 ppm, ph increased from 2.9 to 6.5, and alkalinity increased from 0 to 1,077 ppm when the mine drainage was forced through the anaerobic zone. The observed improvement in water quality was due to both the inherent chemical characteristics of the organic substrate and bacterial activity. Bacterial sulfate reduction rates in the organic substrate ranged from 2 to 600 nmol cm-3 day-1. Sulfate reduction rates are high enough to significantly affect the water quality of acid mine drainage. The sulfate-reducing bacteria effectively precipitate many heavy metals as insoluble sulfides and may also be useful in treatment processes designed to improve the water quality of metal mine drainage.
Proceeds, 1990 Mng. & Reclamation Conf. & Exhibition. West Virginia Univ. Pub. Serv., V. 2, PP. 409-415