Microbiology and Geochemistry of Mine Tailings Amended with Organic Carbon for Passive Treatment of Pore Water

A field-scale experiment was conducted to evaluate organic carbon amendment of mine tailings as a technique for pore water and drainage treatment. Six test cells were constructed by amending sulfide- and carbonate- rich tailings with varied mixtures of peat, spent-brewing grain and municipal biosolids. Samples were collected for microbial, geochemical and mineralogical analysis approximately three years after commencing this experiment. Test cells amended with spent-brewing grain promoted sulfate reduction and effective removal of sulfate and metal(loid)s. The addition of municipal biosolids did not sustain enhanced sulfidogenesis after three years, and peat was an ineffective source of organic carbon. Terminal-restriction fragment length polymorphism revealed that test cells which supported sulfidogenesis exhibited the greatest microbial diversity. Indigenous bacteria identified using molecular and cultivation analyses were found to be related to Cellulomonas, Thiobacillus, Bacteroides, Paludibacter and Desulfovibrio, which was the only sulfate-reducing bacterial (SRB) isolated. The results demonstrate that mixtures of solid organic materials which supported complex anaerobic microbial communities, including sulfate- reducing bacteria, were most effective in promoting pore-water treatment.