Dr Sean Shaw, Dr Brenda Bailey, Mrs Kim Bellefontaine
The Province of British Columbia regulates mines in a manner that supports sustainable resource development, while ensuring environmental protection, reclamation and closure of mines, and the minimization of financial risk to taxpayers in the event that a mining company defaults on its regulatory obligations. Metal leaching and acid rock drainage (ML/ARD) represents the most significant and costly environmental issue facing the mining industry. Thus, adequate mitigations strategies to prevent and minimize ML/ARD are the first line of defence to ensuring a mine is developed, operated and closed in a manner to minimize impacts to water quality. These strategies include, but are not limited to, avoidance of high risk mine waste materials, blending of mine materials, cover systems, segregation, sub-aqueous storage and water treatment. Typically, the Province views water treatment as a mitigation strategy of last resort when other methods are not feasible or sufficient to prevent impacts to the receiving environment. This is due to significant drawbacks with water treatment including the associated risks, long term liabilities, land alienation, secondary waste production and costs. Nevertheless, with effective drainage collection and the appropriate process or technology, water treatment of contaminated drainage can be a highly effective and reliable means of protecting the downstream environment, and in many cases, may be the only feasible means of preventing off-site impacts. Water treatment technologies are currently permitted and employed on 18 mine sites in British Columbia, with an additional eight systems required for mine sites in the future, either during operations and/or at closure. These technologies include a range of active water treatment systems, including low and high density sludge lime treatment, ferric sulphate, pit lake bioreactor, fluidized bed reactor, advanced biological metals removal (ABMet), flocculant and multistage metal removal systems. Several new active water treatment technologies have been proposed for new and existing mine sites in British Columbia, including ion exchange, nanofiltration, reverse osmosis, biological oxidation/reduction, electro-coagulation and electrochemical oxidation/reduction processes. Additionally, several semi-passive technologies have been proposed and/or are undergoing pilot scale trials, including various bioreactors, saturated rock fills, permeable reactive barriers, limestone drains and wetlands. This presentation will explore some of the challenges with current and emerging water treatment technologies from a regulatory perspective, and discuss how these can be addressed by industry to meet regulatory requirements for mining projects in BC.