Abstract
This study applied a passive sampling approach using low-density polyethylene passive samplers to determine the treatment efficiency of the Kearl surface flow treatment wetland for polycyclic aromatic hydrocarbons (PAHs) in Oil Sands Process-affected Waters (OSPW). Treatment efficiency was measured as concentration-reduction and mass-removal from the OSPW. The results show that the wetland’s ability to remove individual PAHs from the influent varied substantially among the PAHs investigated. Treatment efficiencies of individual PAHs ranged between essentially 0% for certain methylated PAHs (e.g., 2,6-dimethylnaphthalene) to 95% for fluoranthene. Treatment in the Kearl wetland reduced the combined total mass of all detected PAHs by 54 to 83%. This corresponded to a reduction in the concentration of total PAHs in OSPW of 56 to 82% with inflow concentrations of total PAHs ranging from 7.5 to 19.4 ng/L. The concentration of pyrene in water fell below water quality targets in the Muskeg River Interim Management Framework as a result of wetland treatment. The application of the passive samplers for toxicity assessment showed that in this study PAHs in both the influent and effluent were not expected to cause acute toxicity. Passive sampling appeared to be a useful and cost-effective method for monitoring contaminants and for determining the treatment efficiency of contaminants in the treatment wetland.
Highlights
As demand for freshwater conservation grows, there is a need for sustainable solutions to manage and reuse process-affected waters
Organic Carbon (DOC), pH, Total Dissolved Solids (TDS), Total Suspended Solids (TSS), turbidity, and water temperature of Oil Sands Process-affected Waters (OSPW) in the wetland were below the upper limits of the water quality targets (WQTs) listed in [35]
This study shows that a surface treatment wetland is able to substantially reduce concentrations of
Summary
As demand for freshwater conservation grows, there is a need for sustainable solutions to manage and reuse process-affected waters. Since OSPW is currently subject to a ‘zero discharge’ policy and few treatment options are available, OSPW is either recycled for further use in the extraction process or stored in effluent tailings ponds. These effluent tailings ponds are susceptible to leaching and erosion, and present adverse risks to migratory birds and wildlife that confuse these areas for safe ecological havens [5,6,7,8]. Treatment wetlands have emerged as a potentially feasible option to treat OSPW [9,10,11,12,13,14,15]
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