Schoen Mary E, Jahne Michael A, Garland Jay L
Soller Environmental, Inc., 3022 King St., Berkeley, CA 94703, USA.
U.S. Environmental Protection Agency, 26 W. Martin Luther King Drive, Cincinnati, OH 45268, USA.
Water (Basel). 2018 Oct;10(10). doi: 10.3390/w10101352. Epub 2018 Sep 28.
We used quantitative microbial risk assessment (QMRA) to estimate the microbial risks from two contamination pathways in onsite non-potable water systems (ONWS): contamination of potable water by (treated) reclaimed, non-potable water and contamination of reclaimed, non-potable water by wastewater or greywater. A range of system sizes, event durations, fraction of users exposed, and intrusion dilutions were considered (chlorine residual disinfection was not included). The predicted annual microbial infection risk from domestic, non-potable reuse remained below the selected benchmark given isolated, short-duration intrusion (i.e., 5-day) events of reclaimed water in potable water. Whereas, intrusions of wastewater into reclaimed, non-potable water resulted in unacceptable annual risk without large dilutions or pathogen inactivation. We predicted that 1 user out of 10,000 could be exposed to a 5-day contamination event of undiluted wastewater in the reclaimed, non-potable water system each year to meet the annual benchmark risk of 10 infections per person per year; whereas, 1 user out of 1000 could be exposed to a 5-day contamination event of undiluted reclaimed water in the potable water each year. Overall, the predicted annual risks support the use of previously derived non-potable reuse treatment requirements for a variety of ONWS sizes and support the prioritization of protective measures to prevent the intrusion of wastewater into domestic ONWS.
我们采用定量微生物风险评估（QMRA）来估算现场非饮用水系统（ONWS）中两条污染途径所带来的微生物风险：（经处理的）再生非饮用水对饮用水的污染，以及废水或中水对再生非饮用水的污染。我们考虑了一系列系统规模、事件持续时间、暴露用户比例和侵入稀释情况（未包括余氯消毒）。对于饮用水中再生水的孤立、短期（即5天）侵入事件，家庭非饮用水回用的预测年度微生物感染风险仍低于选定的基准。然而，废水侵入再生非饮用水会导致年度风险不可接受，除非进行大量稀释或使病原体失活。我们预测，每年在再生非饮用水系统中，每10000名用户中有1人可能会遭遇5天未稀释废水的污染事件，以满足每人每年10次感染的年度基准风险；而在饮用水中，每年每1000名用户中有1人可能会遭遇5天未稀释再生水的污染事件。总体而言，预测的年度风险支持对各种规模的ONWS使用先前推导的非饮用水回用处理要求，并支持优先采取保护措施以防止废水侵入家庭ONWS。
