University of Illinois at Urbana-Champaign. Water Resources Center
Abstract
Research was conducted to evaluate methods for the biological treatment of acid mine drainage (AMD). Two general approaches were evaluated. The first evaluated treatment of impounded AMD through the addition of a mixed microbial community and carbon sources appropriate for their maintenance. This approach was designed to promote sulfate reduction. Hydrogen sulfide produced by sulfate reduction can potentially react with metals in solution to form metal sulfide precipitates. The process improves pH and generally improves water quality. Several approaches were attempted to provide suitable microbial communities, carbon sources, and environmental conditions suitable for continuous microbial activity. Wood dust and typical solid waste materials were shown to support sulfate reduction, but maintenance of sulfate reduction in AMD solutions was limited. In addition to wood dust and solid waste materials, sponge substrates were used to "package" the microbial community in portable units which could be added to AMD impoundments. Tests of sulfate reduction and water quality improvement indicated that microbial communities were limited by "packaging" procedures. Sustained sulfate reduction was not obtained and water quality improvement was minimal. Several mechanisms of AMD quality improvement were evaluated or identified. Most significant was the potential for wood dust improvement of AMD quality when no biological activity was present. To provide adequate treatment of AMD, a second effort was directed to evaluation of a biologically based unit process for AMD treatment. Using an anerobic digestor which provided waste liquors high in organic acids, AMD was mixed with digestor effluent in an anaerobic reactor which maintained sulfate reduction. The end result was production of an effluent with low iron concentrations and no detectable heavy metals with a pH in the range of 6.5 to 8.5. The utility of a pilot plant design incorporating anaerobic digestion, sulfate reduction, aeration, and final clarification and settling was demonstrated. Useful outcomes of the proposed process were the production of metal precipitates in a form which is easily dewatered and potentially valuable, and the production of organic material (from the digestor) which may be considered a useful soil amendment in site reclamation.U.S. Department of the InteriorU.S. Geological SurveyOpe
