Characterization of roof runoff microbial quality in four U.S. cities with varying climate and land use characteristics

Quantitative microbial risk assessment of pathogen exposure from rainwater used in high-pressure vehicle washing

A literature-based quantitative microbial risk assessment (QMRA) was performed for the fit-for-purpose use of roof-collected rainwater in high-pressure vehicle washing. Our exposure assessment combined estimates of enteric pathogens in roof runoff (available for Salmonella, Campylobacter, and Giardia spp.) with an experimental study that directly measured vehicle washing exposure doses via a conserved tracer. For dose-response modeling, we considered a disability-adjusted life year (DALY) endpoint to capture the disease burden of potential pathogen infections. Annual risks for domestic and occupational scenarios were compared to a 10-6 DALY per person per year (ppy) benchmark using either untreated water or water treated to achieve previously reported log reduction targets (LRTs) for other forms of non-potable use. Combined across pathogens, vehicle washing using untreated roof-collected rainwater resulted in 95th percentile risks of 10-1.4 and 10-2.4 DALY ppy for occupational and recreational exposures, respectively, exceeding the selected benchmark. Treatment following indoor use or irrigation LRTs met the benchmark for domestic but not occupational use, suggesting that home vehicle washing can be included with other non-potable uses following existing treatment guidances. We also calculated new setting-specific LRTs for both scenarios (1.0-3.5 for domestic and 3.0-5.5 for occupational depending on pathogen), providing explicit risk-based treatment guidance for these applications.

Microbial Treatment Targets for Potable and Nonpotable Water Reuse - A Comprehensive Update and Harmonization

Increasing pressures on traditional sources of water have accelerated the adoption of water reuse throughout the world. A key consideration for communities pursuing water reuse is understanding the amount of treatment that is needed to ensure adequate human health protection. Several U.S. EPA documents describe the importance of managing acute microbial risks and highlight the utility of quantitative microbial risk assessment for developing "fit-for-purpose" treatment targets based on the source of water and end-use. However, there are no U.S. federal water reuse regulations and states are currently considering microbial treatment targets for various applications. Previous publications have yet to address this need by using an updated and consistent set of input parameters to present risk-based microbial treatment targets across a wide range of sources of water, end-use applications, and health benchmarks. This work combines the most current modeling inputs and dose-response parameter values to provide probability of infection and disease burden-based microbial treatment targets for untreated municipal wastewater, untreated onsite wastewater, graywater, stormwater, and roof runoff water used for potable reuse, indoor nonpotable use, and landscape irrigation applications.

First flush stormwater pollution in urban catchments: A review of its characterization and quantification towards optimization of control measures

Identification, quantification, and control of First-Flush (FF) are considered extremely crucial in urban stormwater management. This paper reviews the methods for FF phenomenon identification, characteristics of pollutants flushes, technologies for FF pollution control, and the relationships among these factors. It further discusses FF quantification methods and optimization of control measures, aiming to reveal directions for future studies on FF management. Results showed that statistical analyses and Runoff Pollutographs Applying Curve (RPAC) fitting modelling of wash-off processes are the most applicable FF identification methods currently available. Furthermore, deep insights into the pollutant mass flushing of roof runoff may be a critical approach to characterizing FF stormwater. Finally, a novel strategy for FF control is established comprising multi-stage objectives, coupling LID/BMPs optimization schemes and Information Feedback (IF) mechanisms, aiming towards its application for the management of urban stormwater at the watershed scale.

Onsite Nonpotable Water Systems Pathogen Treatment Targets: A Comparison of Infection and Disability-Adjusted Life Years (DALYs) Risk Benchmark Approaches

Pathogen log10 reduction targets for onsite nonpotable water systems were calculated using both annual infection (LRTINF) and disability-adjusted life year (LRTDALY) benchmarks. The DALY is a measure of the health burden of a disease, accounting for both the severity and duration of illness. Results were evaluated to identify if treatment requirements change when accounting for the likelihood, duration, and severity of illness in addition to the likelihood of infection. The benchmarks of 10-4 infections per person per year (ppy) and 10-6 DALYs ppy were adopted along with multilevel dose-response models for Norovirus and Campylobacter jejuni, which characterize the probability of illness given infection (Pill|inf) as dose-dependent using challenge or outbreak data. We found differences between treatment requirements, LRTINF - LRTDALY, for some pathogens, driven by the likelihood of illness, rather than the severity of illness. For pathogens with dose-independent Pill|inf characterizations, such as Cryptosporidium spp., Giardia, and Salmonella enterica, the difference, LRTINF - LRTDALY, was identical across reuse scenarios ( Collapse

Key Words

• DALY
• Norovirus
• dose−response
• nonpotable
• reuse
• wastewater

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MESH Headings

• Humans
• Disability-Adjusted Life Years
• Cryptosporidiosis/epidemiology
• Benchmarking
• Cryptosporidium
• Water Purification
• Risk Assessment

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Grants Collapse

Affiliation(s)

Mary E Schoen Soller Environmental, LLC., 3022 King St., Berkeley, California 94703, United States
Jay Garland U.S. Environmental Protection Agency, 26 W. Martin Luther King Drive, Cincinnati Ohio 45268, United States
Jeffrey A Soller Soller Environmental, LLC., 3022 King St., Berkeley, California 94703, United States
Sean X Thimons Oak Ridge Institute for Science and Education, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268, United States
Michael A Jahne U.S. Environmental Protection Agency, 26 W. Martin Luther King Drive, Cincinnati Ohio 45268, United States

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Collaborators Collapse

Enteric pathogen reduction targets for onsite non-potable water systems: A critical evaluation

Onsite non-potable water systems (ONWS) collect and treat local source waters for non-potable end uses such as toilet flushing and irrigation. Quantitative microbial risk assessment (QMRA) has been used to set pathogen log10-reduction targets (LRTs) for ONWS to achieve the risk benchmark of 10-4 infections per person per year (ppy) in a series of two efforts completed in 2017 and 2021. In this work, we compare and synthesize the ONWS LRT efforts to inform the selection of pathogen LRTs. For onsite wastewater, greywater, and stormwater, LRTs for human enteric viruses and parasitic protozoa were within 1.5-log10 units between 2017 and 2021 efforts, despite differences in approaches used to characterize pathogens in these waters. For onsite wastewater and greywater, the 2017 effort used an epidemiology-based model to simulate pathogen concentrations contributed exclusively from onsite waste and selected Norovirus as the viral reference pathogen; the 2021 effort used municipal wastewater pathogen data and cultivable adenoviruses as the reference viral pathogen. Across source waters, the greatest differences occurred for viruses in stormwater, given the newly available municipal wastewater characterizations used for modeling sewage contributions in 2021 and the different selection of reference pathogens (Norovirus vs. adenoviruses). The roof runoff LRTs support the need for protozoa treatment, but these remain difficult to characterize due to the pathogen variability in roof runoff across space and time. The comparison highlights adaptability of the risk-based approach, allowing for updated LRTs as site specific or improved information becomes available. Future research efforts should focus on data collection of onsite water sources.

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

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.