Gault, A.G., J.M. Harrington, C. Robertson, M.C. Simair, and V.P.M. Friesen.
11th ICARD IMWA 2018 Annual Conference, September 10-14, Pretoria, South Africa. IMWA Proceedings (Volume I), 2018

Part of closure planning for the United Keno Hill Mines site in central Yukon, Canada included evaluating options for long-term treatment of several flowing adits in which Cd and Zn are the principal contaminants of concern. A 3.5-yr in situ pilot test conducted at the Silver King Mine was initiated to evaluate the potential closure strategy to treat Cd and Zn using in situ biological treatment. Pumped mine water was mixed with methanol or molasses as a carbon source and reinjected to create an environment ideal for sulfate-reducing bacteria to grow, precipitating Zn and Cd in the process. Four molasses injections were performed in 2015, each lasting between 24 and 42 days, and 2 additional injections of methanol followed in 2016, totaling 105 days. Genomic analysis confirmed the presence of sulfate-reducing bacteria dominated by members of the Desulfosporosinus genus. Following carbon injection, Zn and Cd concentrations declined by >90%. Despite rising slowly over time, Zn and Cd concentrations remained below both their pre-treatment concentrations and the effluent quality standards such that carbon injections on an annual basis may maintain low metal concentrations. https://www.imwa.info/docs/imwa_2018/IMWA2018_Gault_121.pdf