Biological treatment of naphthenic acids in oil sands process waters

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The Athabasca oilsands is the world’s third largest petroleum reserve. The Clark’s hot water extraction process separates bitumen from oilsands and generates a wastewater stream known as oilsands process waters (OSPW). A complex mixture of naphthenic acids (NAs) at a low concentration in the extraction water has been identified as the major toxic component, and as the most significant barrier to remediation of OSPW. Hence, the Alberta Environmental Protection and Enhancement Act prohibits its discharge. Since there is no effective treatment at an industrial scale, OSPW is stored in tailings ponds that exceed 720 million m3. As the oilsands industry expands, environmental concerns become increasingly important. In previous work, we have shown that a microbial biofilm in a fully-instrumented, continuous flow reactor has been established on OSPW as the only source of carbon and energy and was able to remove 38 ± 7% of NAs at a rate of 2.82 mg/L-d, substantially higher than previous reports. However, higher NA removal is needed for industrial application. To achieve this, we need a better understanding of the role that different microbial populations in the biofilm play in degrading different groups of NAs so that we can artificially construct a specific biofilm composition that would degrade NAs more effectively and efficiently and so achieve a much higher level of NAs removal. The overall goal of this research program is to develop a biofilm reactor system for the biodegradation and detoxification of NAs in OSPW. If successful, this program will be the first to demonstrate that an artificially constructed, complex biofilm reactor can effectively enhance the cleanup of complex organic wastes like NAs in OPSW. This could lead to pilot-scale studies and commercialization, resulting in economic, social and environmental benefits to Canada.