Investigating the toxicity, microbial response and biogeochemical composition of gamma irradiated end products in oil sands process material

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The oil sands deposits of north-eastern Alberta are one of the largest oil reserves in the world, containing an estimated 2.5 trillion barrels of recoverable bitumen held in a mineral matrix consisting of sand, clay and water. Traditional methods used to extract bitumen from excavated oil sands involve the use of hot water digestion and flotation which produces a fine tailing slurry consisting of water, sand, fines, residual bitumen and naphtha products comprising a material known as fluid fine tails (FFT) and oil sands process water (OSPW). Naphthenic acids (NA) are components of most petroleum, including those found in the Athabasca oil sands. Their presence in the environment can pose significant problems since freshly released NAs are toxic to aquatic organisms. Although toxicity declines with time in the environment, the refractory components of the NA mixture can persist for years. The oil companies are interested in finding an optimal solution to treat FFT and reduce and remove residual NAs so that it can be safely released into the natural environment and comply with regulatory guidelines. Our research program is investigating the effects of high energy gamma irradiation to remove and reduce the toxicity of NA mixtures. Preliminary bench scale trials have documented 95% reduction of NAs in OSPW and 50% reduction in the FFT. This research program will confirm the efficacy of gamma irradiation in breaking down NA mixtures in OSPW and FFT, assess biological responses to the irradiated materials in the laboratory, and use field cells to monitor the longer-term characteristics of the gamma treatments in a natural environment. Disposal of the oil sands process waste in an environmentally responsible fashion is paramount to ensuring proactive regional environment management that addresses the cumulative biophysical, health and long-term management strategy for the region. The outcomes generated by this research will contribute to an improved understanding of waste treatment for oil sands operators and provide potential treatment solutions for sustainable management practice in an environmentally sensitive region into perpetuity.