Enteric pathogen reduction targets for onsite non-potable water systems: A critical evaluation.
Michael A Jahne1, Mary E Schoen2, Anya Kaufmann3
1Office of Research and Development, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr., Cincinnati, OH 45268, USA.
Water Research
|February 27, 2023
Summary
Quantitative microbial risk assessment (QMRA) for onsite non-potable water systems (ONWS) shows consistent pathogen log10-reduction targets (LRTs) between 2017 and 2021. This risk-based approach allows for adaptable LRTs as new data emerges.
Area of Science:
- Environmental Engineering
- Public Health
- Microbiology
Background:
- Onsite non-potable water systems (ONWS) are crucial for water reuse in applications like toilet flushing and irrigation.
- Quantitative microbial risk assessment (QMRA) is employed to establish pathogen log10-reduction targets (LRTs) for ONWS, aiming for a benchmark of 10^-4 infections per person per year.
- Two significant efforts in 2017 and 2021 have refined these LRTs.
Purpose of the Study:
- To compare and synthesize the pathogen LRTs established in 2017 and 2021 for ONWS.
- To inform the selection of appropriate pathogen LRTs for various onsite water sources.
- To highlight the adaptability of the risk-based QMRA approach.
Main Methods:
- Comparative analysis of QMRA methodologies and pathogen data used in 2017 and 2021 LRT efforts.
- Evaluation of LRTs for human enteric viruses and parasitic protozoa across different source waters (wastewater, greywater, stormwater).
- Assessment of reference pathogen selection and its impact on LRTs, particularly for viruses in stormwater.
Main Results:
- LRTs for viruses and protozoa in onsite wastewater, greywater, and stormwater remained within 1.5-log10 units between the 2017 and 2021 efforts.
- Differences in LRTs were most pronounced for viruses in stormwater, influenced by updated municipal wastewater data and reference pathogen choices (Norovirus vs. adenoviruses).
- Roof runoff LRTs indicate a need for protozoa treatment, though variability in pathogen presence poses characterization challenges.
Conclusions:
- The risk-based QMRA approach for ONWS is adaptable, allowing for updated LRTs as new information becomes available.
- Consistent LRTs across different efforts demonstrate the robustness of the QMRA framework for ensuring water safety.
- Future research should prioritize data collection on onsite water sources to further refine risk assessments and treatment strategies.
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