Oil sands naphthenic acids: A review of properties, measurement, and treatment

• Toxicity and ubiquity of NAs in OSPW continues to drive concerted research efforts.
• Research, monitoring plagued by lack of universal adoption of single analytical method.
• NA recalcitrance to biodegradation by indigenous microorganisms firmly established.
• Treatment strategy has evolved to advanced oxidation, attached growth bioreactors.

The Alberta oil sands contain one of the world’s largest reserves of oil – over 169 billion barrels of bitumen are economically recoverable with current extraction technologies. Surface mining and subsequent hot water extraction of bitumen from the ore generates about nine cubic meters of raw tailings per cubic meter of oil. Oil sands facilities are required to operate under a policy of zero water discharge, resulting in ponds containing more than one billion cubic meters of tailings, a mixture of sand, fines and process-affected water. Process-affected water contains numerous organic compounds, including naphthenic acids (NAs), which have been identified as the primary source of acute toxicity of process-affected water. Developments in analytical techniques, aerobic biodegradability, and treatment via chemical oxidation (ozone) of NAs are reviewed. The field continues to be challenged by the lack of a cost-effective, accurate analytical technique for NAs or an understanding of all the organic constituents in process-affected water that may be contributing to observed toxicity and thus requiring treatment.

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