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

Abstract

To address decreasing water supplies, several US regulatory entities are developing regulations and guidance for the direct potable reuse (DPR) of wastewater, i.e., potable reuse with a limited or no...

Science-based pathogen treatment requirements for direct potable reuse

“…To expand the dataset to include other geographic locations and time periods, Darby et al identified other historical datasets meeting a minimum set of criteria and developed an approach to combine these highest-quality data into single pathogen distributions. 10 All data points from each of the selected studies were pooled together and log-transformed to produce a normally distributed dataset. The parameters of the resulting log-normal distribution were defined and values from the distribution were sampled for the estimation of LRT requirements.…”

“…This decision is relevant for regulatory development because it can impact the LRT required to protect public health. The following example shows how the Cryptosporidium LRT would be impacted by the use of 1) a conservative point 20 or 2) the aggregated, DPR-2 distribution 10 by keeping all other QMRA inputs equal (see Methods). The point estimate leads to a single LRT value of approximately 11 logs to achieve the daily risk goal of 2.7 × 10 −7 infections per person per day (Fig.…”

“…When appropriate, the new data could be integrated using the approach of Darby et al to create a more robust dataset. 10…”

“…Ultimately, adenovirus was determined to require lower LRTs than the other viruses and so was not included in the present analysis, though details on adenovirus distributions are available. 5,10 Concentrations of these pathogens in raw wastewater were recently evaluated as a part of the State Board's pathogen monitoring campaign, 5 henceforth referred to as DPR-2. The State Board developed LRTs for DPR using different data for raw wastewater concentrations.…”

“…Both the DPRisk tool and the new dataset provide flexibility to be adapted for site-specific conditions in other locations. If a more localized dataset is desired, the approach could be adopted for the monitoring campaign, integrated into the new dataset distributions, 10 and evaluated using site-specific conditions within DPRisk.…”