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Infectious Prion Inactivation in Water and Wastewater Open Access


Other title
Type of item
Degree grantor
University of Alberta
Author or creator
Ding, Ning
Supervisor and department
Gamal El-Din, Mohamed (Civil and Environmental Engineering)
Belosevic, Miodrag (Biological Sciences)
Examining committee member and department
Gamal El-Din, Mohamed (Civil and Environmental Engineering)
Biswas, Nihar (Civil and Environmental Engineering, University of Winsor)
Belosevic, Miodrag (Biological Sciences)
Neumann, Norman (Public Health Sciences)
Ulrich, Ania (Civil and Environmental Engineering)
Department of Civil and Environmental Engineering
Environmental Engineering
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Misfolded prions (PrPSc) are well known for their resistance to conventional decontamination processes. The potential risk of contamination of the water environment, as a result of the disposal of specified risk materials (SRM), has raised public concerns. Ozone is commonly utilized in the water industry for the inactivation of microbial contaminants and was tested in this research for its ability to inactivate prions (263K hamster scrapie). With the applied ozone dose of 7.6-25.7 mg/L, the efficacy of ozone inactivation of PrPSc was both pH and temperature dependent. Treatment variables included applied ozone dose (7.6–25.7 mg/L), contact time (5 s and 5 min), temperature (4°C and 20°C) and pH (pH 4.4, 6.0, and 8.0). The inactivation of PrPSc was quantified by determining the in vitro destruction of PrPSc templating properties using the protein misfolding cyclic amplification (PMCA) assay and bioassay. Highest levels of prion inactivation (≥4-log) were observed with applied ozone doses of 13.0 and 25.7 mg/L, at pH 4.4 and 20°C. The kinetic modeling of prion inactivation in phosphate buffered saline (PBS) with applied ozone dose of 10.8 mg/L at pHs and temperatures described above was characterized by both Chick-Watson (CW) and efficiency factor Hom (EFH) models. It was found that the EFH model fit the experimental data more appropriately. Based on the EFH model, CT values were determined for 2-log, 3-log, and 4-log inactivation. A comparison of ozone CT requirements among various pathogens suggests that prions are more susceptible to ozone degradation than some model bacteria and protozoa. Subsequently, the ozone inactivation of infectious prions was assessed in the raw, gravity separated and dissolved air flotation (DAF) treated rendering wastewater, and in the municipal final effluent. It was found that the organic load highly affected prion inactivation by ozone, while DAF treatment significantly removed the organics and improved the efficacy. At the applied ozone dose of 44.6 mg/L, a >4-log inactivation was achieved after 5 min of exposure in the DAF treated rendering plant wastewater. The results indicated that ozone could serve as a final barrier for prion inactivation in primary and/or secondary treated wastewater.
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.
Citation for previous publication
Ding, N., Neumann, N., Luke, P., Braithwaite, S., Balachandran, A., Belosevic, M., Gamal El-Din, M. (2012) Applied and Environmental Microbiology. 78(3): 613-620.Ding, N., Neumann, N., Luke, P., Braithwaite, S., Balachandran, A., Belosevic, M., Gamal El-Din, M. (2013) Applied and Environmental Microbiology. Published ahead of print 15 February 2013.

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