Improving passive bioreactors for treatment of mine drainage

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This research is a collaboration between Bralorne Gold Mines Ltd., Clear Coast consulting and UBC. Avino Silver and Gold Mines Ltd. owns and operates the Bralorne Gold Mine in Bralorne BC. The mine, produces drainage that must be treated. Clear Coast Consulting has developed a novel passive bioreactor system that has been demonstrated to be quite successful in removing arsenic from the mine drainage during regular flows, allowing Bralorne Gold Mines to continue mining operations and meet discharge permit requirements. The passive system, however, was not as successful when treating the large flows that stem from spring freshet. Clear Coast Consulting has developed the idea of adding a soluble carbon source to the reactor during the freshet to stimulate the activity of the organisms in the reactor. Previous experience suggests that this will allow the reactor to perform well under the high flow conditions. When the plan was put to the BC Ministry of Mines, they responded with some specific questions that must be answered before a full scale system can be allowed. This project has been designed to answer those questions by examining some of the fundamental reactions occurring as well as determining practical operating parameters. We will determine the best chemical to be added as a carbon source and when to add the carbon to achieve our goals and how different carbon sources will affect the form of arsenic precipitated in the reactor. The project will provide a valuable training experience to a master's student in both fundamental microbiological and chemical investigations as well as in methods to deal with real-world scenarios in an industrial system. The results will immediately benefit Bralorne Gold Mines and subsequently the BC mining industry and beyond. Passive bioreactors are able to operate with low requirements for human attention and so will reduce labor costs and also the costs associated with mining, transporting and storing the large amounts of chemicals necessary to perform conventional treatment of drainage water. The environmental benefit will be more stable and reliable treatment systems that take advantage of natural microbial processes to control release of pollutants from mining operations.