Reduction of acid mine drainage with sulfate reducing bacteria

摘要

Coal or mineral mining operations generate pyritic wastes that are often deposited at open lands near the mine sites. Chemical or biocvhemical oxidation of pyrites in the waste piles results in the production of sulfuric acid solutions with pH values frequently less than 2. In addition, these low pH leachates often contain high concentrations of toxic heavy metals. This study addresses an innovative approach to preventing the production of acidic leachate from mining waste piles by promoting the growth of sulfate reducing bacteria (SRB) within the piles. The activity of SRB is known to neutralize acids and stabilize toxic metals as non-bioavailable metal sulfide precipitates. Batch and column studies were conducted to evaluate the feasibility of colonizing mine waste piles with SRB for in-situ treatment of acidic leachate containing toxic metals. Inoculation of mine waste materials in batch reactors with SRB cultures resulted in the neutralization of acidic supernatant (pHapprox3) to pH above 7.0. During the batch incubation, the dissolved concentrations of Cd, Cu, Ni, and Zn were also decreased to undetectable levels. In continuous flow column experiments we observed that the effulent pH fromt he column containing SRB colonized waste increase to above 7.0 while the effluent from abiotic column have pH of 2.5. Heavy metal removal efficiencies of greater than 99 percent for Cd, Cu, and Zn, and 87 percent for Ni were attained due to the SRB colonizat ion of mine waste columns.