Selective biodegradation of naphthenic acids and a probable link between mixture profiles and aquatic toxicity.

The toxicity of oil sands process-affected waters (OSPW) from the Athabasca Oil Sands (AOS) in northern Alberta, Canada, is related to a relatively persistent group of dissolved organic acids known as naphthenic acids (NAs). Naphthenic acids are a complex mixture of carboxylic acids, with a general formula C(n)H(2n+Z)O2, where n indicates the carbon number and Z specifies the number of rings in the molecule. The present study is the first to evaluate the potential for the selective biodegradation of NAs and the associated reduction in aquatic toxicity of 2 OSPWs, maintained under 2 different hydraulic retention times and increased nutrient availability (nitrate and phosphate), using flow-through laboratory wetland microcosms over a 52-wk test period.

Degradation and aquatic toxicity of naphthenic acids in oil sands process-affected waters using simulated wetlands.

Oil sands process-affected waters (OSPWs) produced during the extraction of bitumen at the Athabasca Oil Sands (AOS) located in northeastern Alberta, Canada, are toxic to many aquatic organisms. Much of this toxicity is related to a group of dissolved organic acids known as naphthenic acids (NAs). Naphthenic acids are a natural component of bitumen and are released into process water during the separation of bitumen from the oil sand ore by a caustic hot water extraction process.