Risk-based treatment targets for onsite non-potable water systems using new pathogen data

Abstract

Using local sources (roof runoff, stormwater, graywater, and onsite wastewater) to meet non-potable water demands can minimize potable water use in buildings and increase supply reliability. In 2017, an Independent Advisory Panel developed a risk-based framework to identify pathogen log reduction targets (LRTs) for onsite non-potable water systems (ONWSs). Subsequently, California's legislature mandated the development and adoption of regulations—including risk-based LRTs—for use in multifamily residential, commercial, and mixed-use buildings. A California Expert Panel was convened in 2021 to (1) update the LRT requirements using new, quantitative pathogen data and (2) propose treatment trains capable of meeting the updated LRTs. This paper presents the updated risk-based LRTs for multiple pathogens (viruses, protozoa, and bacteria) and an expanded set of end-uses including toilet flushing, clothes washing, irrigation, dust and fire suppression, car washing, and decorative fountains. The updated 95th percentile LRTs required for each source water, pathogen, and end-use were typically within 1-log10 of the 2017 LRTs regardless of the approach used to estimate pathogen concentrations. LRT requirements decreased with influent pathogen concentrations from wastewater to graywater to stormwater to roof runoff. Cost and footprint estimates provide details on the capital, operations and maintenance, and siting requirements for ONWS implementation.

Identifying and aggregating high-quality pathogen data: a new approach for potable reuse regulatory development

“…20–22 Culture methods, which measure infectious organisms, have been the gold standard for QMRA and are therefore the recommended type of assay for viruses. 23…”

“…[20][21][22] Culture methods, which measure infectious organisms, have been the gold standard for QMRA and are therefore the recommended type of assay for viruses. 23 Sample size. Larger sample sets provide a broader characterization of pathogen concentrations at both the low and high end of their distributions.…”

“…While the two datasets for enterovirus used both culture and molecular methods, this effort focused on culture methods given the uncertainty related to the use of molecular data in QMRA. 23,28 The other two criteria (large sample size and temporal distribution) were considered beneficial secondary features but not essential for this effort. As shown in Table 1, DPR-2, 10 Kitajima 2014, 29 Oceanside 2015, 27 San Diego 2019 25 were the only four studies that met all of the criteria (including the beneficial secondary criteria) for an ideal dataset.…”

Health risks from non-potable use of recycled water in buildings. Part 2 - Greywater

“…noveného cíle, kterým je v USA či v Nizozemí míra rizika nepřevyšující referenční hodnotu 10-4 pppy (40)(41)(42). Touto cestou jde např.…”

“…řada jednotlivých států USA. Pro ilustraci zde uvádíme požadavky (LRT) na účinnost čištění šedé vody, ze které má být vyrobena užitková voda pro užití v interiérech: kryptosporidia 3,5; giardie 4,3; noroviry 7,1; adenoviry 6,0; enteroviry 5,2 (40). Certifikaci nabízí např.…”