This paper presents risk-based enteric pathogen log reduction targets for non-potable and potable uses of a variety of alternative source waters (i.e., locally-collected greywater, roof runoff, and stormwater). A probabilistic Quantitative Microbial Risk Assessment (QMRA) was used to derive the pathogen log₁₀ reduction targets (LRTs) that corresponded with an infection risk of either 10⁻⁴ per person per year (ppy) or 10⁻² ppy. The QMRA accounted for variation in pathogen concentration and sporadic pathogen occurrence (when data were available) in source waters for reference pathogens in the genera Rotavirus, Mastadenovirus (human adenoviruses), Norovirus, Campylobacter, Salmonella, Giardia and Cryptosporidium. Non-potable uses included indoor use (for toilet flushing and clothes washing) with occasional accidental ingestion of treated non-potable water (or cross-connection with potable water), and unrestricted irrigation for outdoor use. Various exposure scenarios captured the uncertainty from key inputs, i.e., the pathogen concentration in source water; the volume of water ingested; and for the indoor use, the frequency of and the fraction of the population exposed to accidental ingestion. Both potable and non-potable uses required pathogen treatment for the selected waters and the LRT was generally greater for potable use than non-potable indoor use and unrestricted irrigation. The difference in treatment requirements among source waters was driven by the microbial quality of the water – both the density and occurrence of reference pathogens. Greywater from collection systems with 1000 people had the highest LRTs; however, those for greywater collected from a smaller population (∼ 5 people), which have less frequent pathogen occurrences, were lower. Stormwater had highly variable microbial quality, which resulted in a range of possible treatment requirements. The microbial quality of roof runoff, and thus the resulting LRTs, remains uncertain due to lack of relevant pathogen data.

本文提出了各种替代水源（即当地收集的灰水、屋顶径流和雨水）的非饮用水和饮用水用途的基于风险的肠道病原体对数减少目标。使用概率定量微生物风险评估（QMRA）得出病原体对数₁₀减少目标（LRT），该目标与每人每年10 ^{-4 (ppy)或10 -2}  ppy的感染风险相对应。QMRA 考虑了轮状病毒、乳腺病毒（人类腺病毒）、诺如病毒、弯曲杆菌、沙门氏菌、贾第鞭毛虫和隐孢子虫属参考病原体的源水中病原体浓度和散发病原体发生（数据可用时）的变化。非饮用水用途包括室内使用（冲厕所和洗衣服），偶尔意外摄入经过处理的非饮用水（或与饮用水交叉连接），以及室外使用的不受限制的灌溉。各种暴露场景捕获了关键输入的不确定性，即源水中的病原体浓度；摄入的水量；对于室内使用，意外摄入的频率和人口比例。饮用水和非饮用水都需要对选定的水域进行病原体处理，并且饮用水的 LRT 通常大于非饮用水室内使用和不受限制的灌溉。水源水处理要求的差异是由水的微生物质量（参考病原体的密度和出现情况）驱动的。来自 1000 人的收集系统的灰水的 LRT 最高；然而，从病原体出现频率较低的较小人群（约 5 人）收集的灰水的结果较低。雨水的微生物质量变化很大，这导致了一系列可能的处理要求。由于缺乏相关病原体数据，屋顶径流的微生物质量以及由此产生的 LRT 仍然不确定。