Trussell Technologies, 1939 Harrison Street, Suite 600, Oakland, CA 94612, USA.
Trussell Technologies, 1939 Harrison Street, Suite 600, Oakland, CA 94612, USA.
Water Res. 2017 Oct 1;122:258-268. doi: 10.1016/j.watres.2017.06.014. Epub 2017 Jun 6.
To safely progress toward direct potable reuse (DPR), it is essential to ensure that DPR systems can provide public health protection equivalent to or greater than that of conventional drinking water sources. This study collected data over a one-year period from a full-scale DPR demonstration facility, and used both performance distribution functions (PDFs) and quantitative microbial risk assessment (QMRA) to define and evaluate the reliability of the advanced water treatment facility (AWTF). The AWTF's ability to control enterovirus, Giardia, and Cryptosporidium was characterized using online monitoring of surrogates in a treatment train consisting of ozone, biological activated carbon, microfiltration, reverse osmosis, and ultraviolet light with an advanced oxidation process. This process train was selected to improve reliability by providing redundancy, defined as the provision of treatment beyond the minimum needed to meet regulatory requirements. The PDFs demonstrated treatment that consistently exceeded the 12/10/10-log thresholds for virus, Giardia, and Cryptosporidium, as currently required for potable reuse in California (via groundwater recharge and surface water augmentation). Because no critical process failures impacted pathogen removal performance during the yearlong testing, hypothetical failures were incorporated into the analysis to understand the benefit of treatment redundancy on performance. Each unit process was modeled with a single failure per year lasting four different failure durations: 15 min, 60 min, 8 h, and 24 h. QMRA was used to quantify the impact of failures on pathogen risk. The median annual risk of infection for Cryptosporidium was 4.9 × 10 in the absence of failures, and reached a maximum of 1.1 × 10 assuming one 24-h failure per process per year. With the inclusion of free chlorine disinfection as part of the treatment process, enterovirus had a median annual infection risk of 1.5 × 10 (no failures) and a maximum annual value of 2.1 × 10 (assuming one 24-h failure per year). Even with conservative failure assumptions, pathogen risk from this treatment train remains below the risk targets for both the U.S. (10 infections/person/year) and the WHO (approximately 10 infections/person/year, equivalent to 10 DALY/person/year), demonstrating the value of a failure prevention strategy based on treatment redundancy.
为了安全地推进直接饮用水再利用（DPR），确保 DPR 系统能够提供等同于或优于传统饮用水源的公共卫生保护至关重要。本研究从一个全规模 DPR 示范设施收集了为期一年的数据，并使用性能分布函数（PDF）和定量微生物风险评估（QMRA）来定义和评估先进水处理设施（AWTF）的可靠性。使用臭氧、生物活性炭、微滤、反渗透和带有高级氧化过程的紫外线的处理链中的在线监测替代物，对肠病毒、贾第虫和隐孢子虫的控制能力进行了特征描述。该处理链通过提供冗余性来提高可靠性，冗余性被定义为提供超出满足监管要求所需的最低限度的处理。该 PDF 演示了处理效果始终超过目前加利福尼亚州饮用水再利用所需的 12/10/10 对数阈值，用于地下水回注和地表水补给。因为在一年的测试中没有关键的工艺故障影响病原体去除性能，所以在分析中纳入了假设故障，以了解处理冗余对性能的好处。每个单元过程每年都有一次持续不同故障持续时间的单一故障建模：15 分钟、60 分钟、8 小时和 24 小时。QMRA 用于量化故障对病原体风险的影响。在没有故障的情况下，隐孢子虫的年平均感染风险为 4.9×10，在假设每个过程每年发生一次 24 小时故障的情况下，风险最高可达 1.1×10。通过将自由氯消毒作为处理过程的一部分，肠病毒的年平均感染风险为 1.5×10（无故障），最大年值为 2.1×10（假设每年发生一次 24 小时故障）。即使采用保守的故障假设，该处理链的病原体风险仍低于美国（10 人感染/人/年）和世界卫生组织（约 10 人感染/人/年，相当于 10 人 DALY/人/年）的风险目标，证明了基于处理冗余的故障预防策略的价值。
