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Potential Microbial Water Quality Impacts Resulting from Main Breaks in Edmonton, Alberta: A Quantitative Microbial Risk Assessment
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- Author / Creator
- Teslak, Leanne
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Few studies, and even fewer within Canada, have addressed the efficacy of water utility main break response and repair standard operating procedures (SOPs) for prevention of microbial contamination. To better understand such risks in the City of Edmonton, Alberta, ten main break events were evaluated to provide data for a quantitative microbial risk assessment. The motivation for this research comes from the current practice of not ‘super-chlorinating’ the repaired main and that the use of federal Guideline faecal indicators may not effectively index persistent pathogens that could have negative impacts on public health. Soil samples surrounding each break site as well as initial and final flush water samples were collected. Samples were analysed using relevant indicators of potential faecal contamination, including spores of C. perfringens, total coliforms and E. coli by culture and Enterococcus spp., human-targeted Bacteroides HF183 and E. coli by quantitative Polymerase Chain Reaction (qPCR). Ratios were then determined from concentrations of the faecal indicator bacteria (FIB) and reference pathogens, Norovirus GII, Cryptosporidium, Giardia, Campylobacter and Mastadenovirus, reported for raw sewage, the main contamination source of public health concern. These ratios were then applied to the results from each of the ten main break sites which had FIB above the method detection limits for both water and soil samples, assuming soil intrusion at three possible levels, 5 g, 50 g or 500 g. These scenarios were then applied to mains-break repairs for the whole population of Edmonton, AB and Quantitative Microbial Risk Assessment (QMRA) estimated risks were compared to the U.S. EPA infection benchmark of 1/10,000 people per year and the Health Canada drinking water gastrointestinal illness benchmark of one micro disability adjusted life-year (μDALY)/ person per year. Of the reference pathogens examined, Mastadenovirus (human adenovirus) was determined to have the highest risk to public health while Norovirus GII had the lowest. Although many uncertainties were applied to this study, results showed scenarios ranging from having very minimal risk, up to 200 times higher risk than the recommended benchmarks. The ramifications of these results are discussed against current standard operating procedures.
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- Graduation date
- Fall 2018
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.