2019 CSCE Annual Conference - Laval (Greater Montreal) Conference
Dr. Thomas Genty
Dr. Catherine Mulligan, Concordia University (Presenter)
Dr. Laleh Yerushalmi, Concordia University
Dr. Carmen Mihaela Neculita
Mining activities in Agnico-Eagle gold mine site (Laronde, Quebec, Canada) generate wastewater high in sulfate, thiocyanate and ammonium contaminants. The current chemical/biological treatment of the effluent allow being compliant with both Canadian mining effluent regulations and provincial regulation. The Laronde mine site has one of the most advanced biological water treatments of the Canadian mining industry. However, the existing process is complex and evolved anaerobic and aerobic reactors to fully achieve the treatment goal. A recently discovered anaerobic biological ammonium oxidation process known as anammox (AMX) has shown promise in the treatment of sulfate- and ammonium-rich wastewaters due to the capability of the anammox bacteria in the oxidation of ammonium using nitrite, nitrate, and/or sulfate as the main/alternative electron acceptors. Agnico-Eagle is continuously looking to improve the treatment capacity and efficiency (improve water quality and decrease operation cost) and the anammox process was targeted as a promising technology. In this study, the treatment of ammonium-rich gold mine wastewater with low nitrite (< 10 mg/L) by partial nitrification/anammox (PN/AMX) process was investigated in a single-scale hybrid bioreactor at temperature 25 ± 1°C and HRT of 2 days. The main objective was to find the optimal operating and process conditions to support the company in integrating these processes in the existing wastewater treatment trains for the effective treatment of ammonium-rich wastewater. Batch and pilot-scale experiments were conducted with real wastewater containing 100-200 mg/L, 10-50 mg/L, and <10 mg/L of ammonium, nitrate, and nitrite, respectively. The ammonium and total nitrogen removal efficiencies of 87% and 81% were achieved during the stable operation period of 30 days. The batch tests results showed the main mechanisms of ammonium removal was the nitrite dependent ammonium oxidation process. However, nitrate and sulfate were used, respectively, as the main alternative electron acceptors in the absence of nitrite. It was found that the control of pH at 7-8 was the critical operating parameter for a stable PN/A process at this temperature as it minimized the fast pH decreases due to the rapid alkalinity consumption by microorganisms. This study confirmed the effective removal of ammonium from wastewater with the PN/A process at the temperature of 25°C.