In situ stimulation of thiocyanate biodegradation through phosphate amendment in gold mine tailings water

Thiocyanate (SCN - ) is a contaminant requiring remediation in gold mine tailings and wastewaters 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 â10 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 sulfur-oxidizing bacteria.