Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8847946 | Ecological Engineering | 2018 | 13 Pages |
Abstract
Constructed wetland treatment systems (CWTSs) could provide a passive, low-energy strategy for mitigating risks associated with oil sands process-affected waters (OSPWs). Due to the large volumes (over 975â¯millionâ¯m3), heterogeneous composition, and acute and chronic toxicity of OSPW, passive and efficient treatment to decrease risks to biota will be necessary once operators obtain regulatory permission to discharge into aquatic receiving systems. The research objective was to design, assemble, and measure performance of a pilot-scale hybrid CWTS for treatment of OSPW. Constituents of concern (COCs) identified in OSPW included NAs, oil and grease, As, B, Cu, Pb, and Zn. Oxidizing conditions (net sediment redoxâ¯>â¯â50â¯mV) were promoted to allow aerobic degradation of organic constituents, and co-precipitation of arsenic with iron oxyhydroxides. Treatment of Cu, Pb, and Zn was targeted through precipitation with sulfides in reducing “micro-environments” in wetland sediments. Solar photocatalytic reactors (hybrid components) were used to remove recalcitrant organics. Performance was assessed using rates and extents of removal of COCs and changes in toxicity as indicated by Ceriodaphnia dubia. Mean total naphthenic acid fraction compound concentrations decreased from approximately 43â¯mg/L in untreated OSPW to 10â¯mg/L following a 16-d retention time in the hybrid CWTS. Mean As and Zn concentrations decreased from 0.026â¯mg/L and 0.129â¯mg/L in untreated OSPW to 0.011-0.014â¯mg/L and 0.052-0.062â¯mg/L in wetland outflows, respectively. Cu and Pb mass decreased by 13-26% in the CWTS; however, evaporative concentration masked removal (in terms of total metal concentrations). Toxicity (in terms of C. dubia survival and reproduction) of OSPW was eliminated following treatment. Results demonstrate that hybrid CWTSs can effectively degrade NAs and alleviate toxicity associated with metals and organics in OSPW.
Related Topics
Life Sciences
Agricultural and Biological Sciences
Ecology, Evolution, Behavior and Systematics
Authors
Maas Hendrikse, Daniel P. Gaspari, Andrew D. McQueen, Ciera M. Kinley, Alyssa J. Calomeni, Tyler D. Geer, Monique C. Simair, Kerry M. Peru, John V. Headley, John H. Jr., James W. Castle,