Water quality standards (WQSs) based on water quality measures (e.g., fecal indicator bacteria (FIB)) have been used by regulatory agencies to assess onsite, non-potable water reuse systems. A risk-based approach, based on quantitative microbial risk assessment, was developed to define treatment requirements that achieve benchmark levels of risk. This work compared these approaches using the predicted annual infection risks for non-potable reuse systems that comply with WQSs along with the benchmark risk levels achieved by the risk-based systems. The systems include a recirculating synthetic sand filter or an aerobic membrane bioreactor (MBR) combined with disinfection. The greywater MBR system had predicted risks in the range of the selected benchmark levels. However, wastewater reuse with systems that comply with WQSs had uncertain and potentially high predicted risks (i.e., >10⁻² infections per person per year) in residential applications, due to exposures to viruses and protozoa. The predicted risks illustrate that WQSs based on FIB treatment performance do not ensure adequate treatment removal of viruses and protozoa. We present risk-based log₁₀ pathogen reduction targets for intermediate-sized non-potable systems, which are 0.5 log₁₀ less than those previously proposed for district-sized systems. Still, pathogen treatment performance data are required to better manage non-potable reuse risk.

监管机构已使用基于水质测量（例如粪便指示菌（FIB））的水质标准（WQS）来评估现场非饮用水再利用系统。开发了一种基于定量微生物风险评估的基于风险的方法，以确定达到基准风险水平的处理要求。这项工作使用符合 WQS 的非饮用水再利用系统的预测年度感染风险以及基于风险的系统实现的基准风险水平来比较这些方法。该系统包括循环合成砂过滤器或与消毒相结合的好氧膜生物反应器（MBR）。灰水 MBR 系统预测了所选基准水平范围内的风险。然而，由于暴露于病毒和原生动物，在住宅应用中使用符合WQS的系统进行废水再利用具有不确定且潜在的高预测风险（即每年每人>10 ^-2感染）。预测的风险表明，基于 FIB 治疗表现的 WQS 不能确保充分治疗去除病毒和原生动物。我们提出了针对中等规模非饮用水系统的基于风险的 log ₁₀病原体减少目标，该目标比之前为地区规模系统提出的目标低 0.5 log ₁₀ 。尽管如此，仍需要病原体处理性能数据来更好地管理非饮用水再利用风险。