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Enteric pathogen treatment requirements for non-potable water reuse despite limited exposure data
Citation:
Schoen, M., M. Jahne, AND J. Garland. Enteric pathogen treatment requirements for non-potable water reuse despite limited exposure data. Environmental Science & Technology Letters. American Chemical Society, Washington, DC, 7(12):943-947, (2020). https://doi.org/10.1021/acs.estlett.0c00752
Impact/Purpose:
Exposure factors (e.g., ingestion volume and frequency) are required to establish risk-based treatment requirements (i.e., log10 reduction targets (LRTs)) for enteric pathogens using Quantitative Microbial Risk Assessment (QMRA). However, data to characterize non-potable exposure factors is sparse. We calculated graywater and wastewater non-potable LRTs (corresponding to 10-4 infections per person per year) for uses missing detailed exposure data and across a range of exposure factors. The LRTs decreased linearly toward zero as the log10 volume or frequency decreased. When non-routine exposure was included, representing either accidental ingestion from misuse or cross-connection between potable and non-potable waters, the LRTs remained high, even as the routine ingestion volume decreased. Therefore, uses with small anticipated routine ingestion volumes (i.e., roughly < 10-5 L), e.g., domestic indoor or decorative fountain uses, share common LRTs, and further refinement of the routine exposure is of limited value. Additional data to characterize non-routine exposures and uses with high routine ingestion, e.g., showering, remain valuable to better estimate LRTs. These results will assist regulators in the selection of LRTs for non-potable uses that lack detailed exposure factor characterizations.
Description:
Exposure factors (e.g., ingestion volume and frequency) are required to establish risk-based treatment requirements (i.e., log10 reduction targets (LRTs)) for enteric pathogens using Quantitative Microbial Risk Assessment (QMRA). However, data to characterize non-potable exposure factors is sparse. We calculated graywater and wastewater non-potable LRTs (corresponding to 10-4 infections per person per year) for uses missing detailed exposure data and across a range of exposure factors. The LRTs decreased linearly toward zero as the log10 volume or frequency decreased. When non-routine exposure was included, representing either accidental ingestion from misuse or cross-connection between potable and non-potable waters, the LRTs remained high, even as the routine ingestion volume decreased. Therefore, uses with small anticipated routine ingestion volumes (i.e., roughly < 10-5 L), e.g., domestic indoor or decorative fountain uses, share common LRTs, and further refinement of the routine exposure is of limited value. Additional data to characterize non-routine exposures and uses with high routine ingestion, e.g., showering, remain valuable to better estimate LRTs. These results will assist regulators in the selection of LRTs for non-potable uses that lack detailed exposure factor characterizations.
URLs/Downloads:
DOI: Enteric pathogen treatment requirements for non-potable water reuse despite limited exposure data
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