Naphthenic acids (NAs) are a persistent group of dissolved organic acids found in oil sands process affected water (OSPW) from the Athabasca Oil Sands (AOS) in northern Alberta. This study investigated the feasibility of reducing the toxicity of OSPW in wetland environments, and proposed a strategy for reclamation at the AOS. Laboratory microcosms were used to mimic natural wetlands. The purpose was to determine if the toxicities of OSPWs generated by Syncrude Canada Ltd. (Syncrude) and Suncor Energy Inc. (Suncor) change with time as a result of aging and biodegradation. Experiments involved 2 types of OSPW obtained from Syncrude and Suncor. Nutrient availability (nitrogen and phosphorus enrichment) was increased for both short and long hydraulic retention times (40 and 400 days). The NAs found in the OSPW were tracked over the course of one year using Fourier Transform Infrared Spectroscopy, Gas Chromatography/Mass Spectrometry and Microtox bioassays. The objective was to determine the relationships between total NA concentrations, the degree to which different sub-groups of NAs are biodegraded and any potential reduction in OSPW toxicity