Date of Award
12-2016
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Legacy Department
Wildlife and Fisheries Biology
Committee Member
Dr. John H. Rodgers Jr., Committee Chair
Committee Member
Dr. James W. Castle
Committee Member
Dr. Burton C. Suedel
Committee Member
Dr. George M. Huddleston
Committee Member
Dr. William C. Bridges
Abstract
Mining leases in the Athabasca Oil Sands (AOS) region produce extensive volumes of oil sands process-affected water (OSPW) containing constituents that limit beneficial uses, including discharge into receiving aquatic systems. The aim of this research is to provide a scalable approach using hybrid constructed wetland treatment systems for the mitigation of problematic constituents in OSPW. In the first experiment in this dissertation, OSPW was characterized to identify constituents of concern (COCs) using chemical, physical, and toxicological analyses. Following identification of COCs, bench-scale manipulations (termed process-based manipulations [PBMs]) were used to remove or alter “classes†of COCs in an effort to eliminate toxicity to a sentinel aquatic invertebrate and discern treatment processes. COCs identified in OSPW included organics (naphthenic acids [NAs], oil and grease [O/G]), metals/metalloids, and suspended solids. Results from PBMs indicated that the organic fraction of OSPW was the primary source of toxicity, with oxidation (i.e. H2O2+UV254) and granular activated charcoal treatments eliminating toxicity to Ceriodaphnia dubia (7-8 d), in terms of mortality and reproduction. In the second experiment, photocatalytic degradation of commercial (Fluka) NAs was evaluated using fixed-film titanium dioxide (TiO2) irradiated with sunlight for 8 hours. Changes in NA concentrations by photocatalytic degradation were confirmed analytically and with toxicity tests using sentinel fish and aquatic invertebrate species. The half-life for Fluka NAs achieved by photocatalytic degradation was approximately 2 hours, with toxicity eliminated for vertebrate and invertebrate sentinel organisms (Pimephales promelas and Daphnia magna) by the 5th hour of the sunlight exposure. In the third experiment, toxicity of the NA fraction to microbial populations was evaluated to discern adverse impacts to microbially driven processes within wetlands. Following exposures to a commercial NA, potential effects on sulfate-reducing bacteria (SRB), production of sulfides (as acid-volatile sulfides [AVS]), and precipitation of divalent metals (i.e. Cu, Ni, Zn [as aqueous and simultaneously extracted metals; SEM]) were evaluated. Extent of AVS production was sufficient in all NA exposure concentrations tested to achieve ∑SEM:AVS <1, indicating conditions were conducive for treatment of divalent metals. In addition, no adverse effects to SRB (in terms of density, relative abundance, and diversity) were observed. The lines of evidence indicated that dissimilatory sulfate reduction and subsequent metal precipitation in wetlands will not be vulnerable to NA exposures. In the final experiment, a hybrid pilot-scale CWTS was designed to promote treatment processes to alter (transfer and transform) COCs using sequential reducing and oxidizing wetland reactors and a solar photocatalytic reactor using fixed film titanium dioxide (TiO2). Performance criteria were achieved as the CWTS decreased concentrations of NAs, O/G, suspended solids, and metals to an extent that eliminated toxicity to the aquatic invertebrate C. dubia. Results from this study provide proof-of-concept data to inform hybrid passive or semi-passive treatment approaches (i.e. constructed wetlands) that could mitigate COCs contained in OSPWs. Data presented in this dissertation provide approaches to identify problematic constituents contained in complex energy derived waters (e.g. OSPW) and strategies for mitigating risks by altering exposures using passive (low-energy) treatment systems.
Recommended Citation
McQueen, Andrew David, "Mitigating Risks of Oil Sands Process Affected Water Using Hybrid Constructed Wetland Treatment Systems" (2016). All Dissertations. 1827.
https://tigerprints.clemson.edu/all_dissertations/1827