Infectious Prion Inactivation in Water and Wastewater

  • Author / Creator
    Ding, Ning
  • 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.

  • Subjects / Keywords
  • Graduation date
    Fall 2013
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • 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.