Moreau & Lê Cao - Environ Sci Technol

Collaborative paper between Kim-Anh & John Moreau (AM)

In Situ Stimulation of Thiocyanate Biodegradation through Phosphate Amendment in Gold Mine Tailings Water
Mathew P. Watts, Han M. Gan, Lee Y. Peng, Kim-Anh Lê Cao and John W. Moreau

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ABSTRACT
Thiocyanate (SCN−) is a contaminant requiring remediation in gold mine tailings and waste waters globally. Seepage of SCN−-contaminated waters into aquifers can occur from unlined or structurally compromised mine tailings storage facilities. A wide variety of microorganisms are known to be capable of biodegrading SCN−; however, little is known regarding the potential of native microbes for in situ SCN− biodegradation, a remediation option that is less costly than engineered approaches. Here we experimentally characterize the principal biogeochemical barrier to SCN−biodegradation for an autotrophic microbial consortium enriched from mine tailings, to arrive at an environmentally realistic assessment of in situ SCN− biodegradation potential. Upon amendment with phosphate, the consortium completely degraded up to ∼10 mM SCN− to ammonium and sulfate, with some evidence of nitrification of the ammonium to nitrate. Although similarly enriched in known SCN−-degrading strains of thiobacilli, this consortium differed in its source (mine tailings) and metabolism (autotrophy) from those of previous studies. Our results provide a proof of concept that phosphate limitation may be the principal barrier to in situ SCN− biodegradation in mine tailing waters and also yield new insights into the microbial ecology of in situ SCN− bioremediation involving autotrophic sulfuroxidizing bacteria.