Abstract
Although reclaimed water for potable applications has many potential benefits, it poses concerns for chemical and microbial risks to consumers. We present a quantitative microbial risk assessment (QMRA) Monte Carlo framework to compare a de facto water reuse scenario (treated wastewater-impacted surface water) with four hypothetical Direct Potable Reuse (DPR) scenarios for Norovirus, Cryptosporidium, and Salmonella. Consumer microbial risks of surface source water quality (impacted by 0–100% treated wastewater effluent) were assessed. Additionally, we assessed risks for different blending ratios (0–100% surface water blended into advanced-treated DPR water) when source surface water consisted of 50% wastewater effluent. De facto reuse risks exceeded the yearly 10−4 infections risk benchmark while all modeled DPR risks were significantly lower. Contamination with 1% or more wastewater effluent in the source water, and blending 1% or more wastewater-impacted surface water into the advanced-treated DPR water drove the risk closer to the 10−4 benchmark. We demonstrate that de facto reuse by itself, or as an input into DPR, drives microbial risks more so than the advanced-treated DPR water. When applied using location-specific inputs, this framework can contribute to project design and public awareness campaigns to build legitimacy for DPR.
Highlights
Many arid urban centers in developed and developing countries are struggling to meet their long-term water needs
The idea of using wastewater to augment drinking water supplies has historically faced opposition opposition from the general public, and blending advanced treated wastewater with surface water from supplies the general public, and blending advanced treated wastewater with surface water supplies is one is one way to demonstrate that the supply is not dominated with water of wastewater origin way to demonstrate that thewater supply is not may dominated water ofwith wastewater origin
Data for pathogen removal by full-scale facilities were not available for all processes; surrogate information was used in several cases (MS2 for norovirus or E. coli for Salmonella, for example)
Summary
Many arid urban centers in developed and developing countries are struggling to meet their long-term water needs. In arid regions such as the southwestern US, the situation is exacerbated by drought and changing weather patterns, making surface water supplies less reliable. This reclaimed water can become a sizable component of the water portfolio of an urban center and can increase resiliency to climate change impacts. Water reuse in an urban setting can occur in many forms. Both direct and indirect potable reuse paradigms provide an alternative water source for stressed urban centers without the need for costly dual-distribution systems.
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