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WP1 Restoration of Contaminated Sites
(413) Advances in Biotreatment of Acid Mine Drainage and Biorecovery of Metals: 1. Metal.
Tabak, H1, Scharp, R1, Burckle, J1, Kavahara, F1, Govind, R2, 1 USEPA, NRMRL, Cincinnati, OH, USA2 University of Cincinnati, Cincinnati, OH, USA
ABSTRACT- Acid mine drainage (AMD) , an acidic metal-bearing wastewater poses a severe pollution problem attributed to post-mining activities. The metals (metal sulfates) usually encountered in AMD and considered of concern for risk assessment are: arsenic, cadmium, iron, lead, manganese, zinc and copper, and the organic contaminant in this acidic waste is sulfate. The pollution generated by abandoned mining activities in the area of Butte, Montana has resulted in the designation of the Silver Bow Creek - Butte area as the largest superfund (National Priorities List) site in the U.S. This paper reports the results of bench-scale studies conducted to develop a resource recovery based remediation process for the clean up of the Berkeley Pit, Butte.Montana and equally applicable for the remediation of other acid mine water Pits in U.S and abroad. The process utilizes selective, sequential precipitation (SSP) of metals as hydroxides and sulfides, such as copper, zinc, aluminum, iron and manganese, from the Berkelwy Pit acid mine water for their removal from water in a form suitable for additional processing into marketable precipitates and pigments. The metal biorecovery and recycle process is based on complete separation of the biological sulfate reduction step due to the sulfate reducing bacteria (SRB) activity and the metal precipitation step. Hydrogen sulfide produced in in the SRB bioreactor systems is used in the precipitation step to form insoluble metal sulfides. and hydroxides. The average metal recoveries using the SSP precess were as follows: aluminum (as hydroxide) 99.8%, cadmium (as sulfide) 99.7%, cobalt (as sulfide) 99.1%, copper (as sulfide) 99.8%, ferrous iron (as sulfide) 97.1%, manganese (as sulfide) 87.4%, nickel (as sulfide)47/8% and zinc (as sulfide)100%. The average precipitate purity for metals, copper sulfide, ferric hydroxide, zinc sulfide, aluminum hydroxide and manganese sulfide were: 92.4, 81.5, 97.8, 95.6, 92.1 and 75.0% respectively. The final effluent water, contained only calcium and manganese and both sulfate and sulfide concentratons were below usable water limits. The water quality of this agriculturally usable water meets EPA's gold standard criterion.
Key words: biorecovery and recycle of metals, acid mine drainage
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