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LRT Updates: Synthesizing Results from the 2017 Guidance and the 2021 California Update
Citation:
Jahne, M., J. Garland, M. Schoen, N. Ashbolt, B. Pecson, A. Kaufmann, A. Olivieri, S. Sharvelle, AND A. Anderson. LRT Updates: Synthesizing Results from the 2017 Guidance and the 2021 California Update. Ad Hoc Meeting of the National Blue Ribbon Committee for Onsite Non-Potable Water Systems, virtual, OH, March 03, 2022.
Impact/Purpose:
To share the most recent information on the state of the science of quantitative microbial risk assessment to inform treatment of alternative source waters for safe, non-potable end uses with a nationwide groups of stakeholders (National Blue Ribbon Commission for Onsite Non-Potable Water Systems).
Description:
In 2017, WE&RF published the guidance document “Risk-Based Framework for the Development of Public Health Guidance for Decentralized Non-Potable Water Systems” recommending pathogen log-reduction targets (LRTs) for the treatment of alternative water sources (graywater, combined wastewater, roof runoff, and stormwater) during onsite reuse for indoor use and irrigation. These recommendations were developed using the best-available scientific information to characterize potential health risks and have since been adopted by proposed or enacted state and local regulations throughout the country. As part of this implementation, California has also instituted a new advisory panel to evaluate and update the LRTs as needed to reflect new pathogen datasets and additional end uses of interest. We present an updated set of pathogen LRTs developed for the California State Water Board’s Division of Drinking Water in response to Senate Bill 996. These new LRTs are based on different source characterization assumptions vs. the 2017 guidance and utilize newly available pathogen datasets. Additionally, they extend non-potable end uses to include fire suppression and car washing in addition to toilet flushing, clothes washing, and irrigation. We then compare these to the previous recommendations and discuss implications for regulators and operators of these systems with the goal of developing consensus on best practices for the selection of appropriate treatment targets. We also discuss ongoing efforts under WRF Project #5034 to improve practical implementation of the risk-based framework by assessing stormwater contamination levels and associated treatment requirements for onsite capture and use.