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Biological Treatment of Naphthenic Acids and Other Organic Compounds in Oil Sands Process-Affected Waters
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- Author / Creator
- Brown, Lisa D
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The Alberta oil sands contain one of the world’s largest reserves of oil - over 169 billion barrels of bitumen are economically recoverable with current extraction technologies. Surface mining, whereby the ore is extricated from the earth and bitumen is obtained via a hot water extraction process, accounts for approximately half of current production of synthetic crude oil and generates about nine cubic meters of raw tailings per cubic meter of oil. Oil sands facilities are required to operate under a policy of zero water discharge, resulting in impoundments containing more than one billion cubic meters of tailings, a mixture of sand, fines and process-affected water. Effective treatment processes are required in the immanent future, especially for a class of compounds called naphthenic acids, identified as the primary source of acute toxicity of process-affected water. Aerobic biodegradation of oil sands naphthenic acids by indigenous microbial populations present in tailings ponds has been shown to be slow and incomplete, relative to biodegradation of petroleum-refined naphthenic acids available commercially. This research focused on treating oil sands process-affected waters by coupling oxidation, as a means of reducing the recalcitrance of naphthenic acids and other organic compounds, with biodegradation to remove organic matter, including the resulting daughter products of oxidation. In addition, microbial cultures, obtained from an oil sands tailings pond and enriched on organic matter that included naphthenic acids, were assessed for their capability to biodegrade naphthenic acid compounds. Ozone pretreatment significantly improved the biodegradability of dissolved organic carbon in aged process-affected water samples, from 5 mg/L removal in untreated samples to 11-13 mg/L removal in ozone-treated samples. Ozone exposed indigenous microbial communities were able to degrade an amount of ozone treated organic matter equivalent to those communities not previously exposed, although community structure analysis with microbiological molecular methods indicated these communities were only 65% similar. Ozone pretreatment of model naphthenic acid compounds enabled a bacterial isolate from an oil sands tailings pond, Acidovorax sp., to remove 40% of the tricyclic naphthenic acid, adamantane-1-carboxylic acid, hypothesized to be cometabolized during biodegradation of more labile ozone by-products. A fungal isolate from an oil sands tailings pond, Trichoderma harzianum, was capable of degrading two tricyclic model naphthenic acid compounds. Ozonation coupled with biodegradation is a promising treatment technology for oil sands process-affected waters, as the need for treatment of organic matter more aggressive than natural attenuation has been established. Ozone pretreatment prior to placement of process-affected waters in reclamation environments, such as end-pit lakes or constructed wetlands, may result in adequate removal of organic matter and the associated toxicity by subsequent biodegradation, without the need for building costly ex-situ wastewater treatment facilities.
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- Subjects / Keywords
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- Graduation date
- Fall 2014
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.