Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland; ETH Zürich, Institute of Environmental Engineering, 8093 Zürich, Switzerland.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.
Water Res. 2024 Oct 15;264:122216. doi: 10.1016/j.watres.2024.122216. Epub 2024 Aug 4.
In light of increasingly diverse greywater reuse applications, this study proposes risk-based log-removal targets (LRTs) to aid the selection of treatment trains for greywater recycling at different collection scales, including appliance-scale reuse of individual greywater streams. An epidemiology-based model was used to simulate the concentrations of prevalent and treatment-resistant reference pathogens (protozoa: Giardia and Cryptosporidium spp., bacteria: Salmonella and Campylobacter spp., viruses: rotavirus, norovirus, adenovirus, and Coxsackievirus B5) in the greywater streams for collection scales of 5-, 100-, and a 1000-people. Using quantitative microbial risk assessment (QMRA), we calculated LRTs to meet a health benchmark of 10 infections per person per year over 10'000 Monte Carlo iterations. LRTs were highest for norovirus at the 5-people scale and for adenovirus at the 100- and 1000-people scales. Example treatment trains were designed to meet the 95 % quantiles of LRTs. Treatment trains consisted of an aerated membrane bioreactor, chlorination, and, if required, UV disinfection. In most cases, rotavirus, norovirus, adenovirus and Cryptosporidium spp. determined the overall treatment train requirements. Norovirus was most often critical to dimension the chlorination (concentration × time values) and adenovirus determined the required UV dose. Smaller collection scales did not generally allow for simpler treatment trains due to the high LRTs associated with viruses, with the exception of recirculating washing machines and handwashing stations. Similarly, treating greywater sources individually resulted in lower LRTs, but the lower required LRTs nevertheless did not generally allow for simpler treatment trains. For instance, LRTs for a recirculating washing machine were around 3-log units lower compared to LRTs for indoor reuse of combined greywater (1000-people scale), but both scenarios necessitated treatment with a membrane bioreactor, chlorination and UV disinfection. However, simpler treatment trains may be feasible for small-scale and application-scale reuse if: (i) less conservative health benchmarks are used for household-based systems, considering the reduced relative importance of treated greywater in pathogen transmission in households, and (ii) higher log-removal values (LRVs) can be validated for unit processes, enabling simpler treatment trains for a larger number of appliance-scale reuse systems.
鉴于日益多样化的灰水再利用应用，本研究提出了基于风险的对数去除目标 (LRT)，以帮助在不同收集规模下选择灰水回收的处理途径，包括单个灰水溪流的器具规模再利用。本研究使用基于流行病学的模型模拟了在 5 人、100 人和 1000 人规模的收集范围内，常见和具有抗性的参考病原体（原生动物：贾第虫和隐孢子虫属，细菌：沙门氏菌和弯曲杆菌属，病毒：轮状病毒、诺如病毒、腺病毒和柯萨奇病毒 B5）在灰水中的浓度。通过定量微生物风险评估 (QMRA)，我们计算了 LRT，以满足在 10000 次蒙特卡罗迭代中，每人每年 10 次感染的健康基准。在 5 人规模下，诺如病毒的 LRT 最高，而在 100 人和 1000 人规模下，腺病毒的 LRT 最高。设计了示例处理途径以满足 LRT 的 95%分位数。处理途径包括曝气膜生物反应器、氯化和（如有必要）紫外线消毒。在大多数情况下，轮状病毒、诺如病毒、腺病毒和隐孢子虫属决定了整体处理途径的要求。诺如病毒通常是确定氯化（浓度×时间值）所需的关键因素，而腺病毒决定了所需的紫外线剂量。由于与病毒相关的 LRT 较高，较小的收集规模通常不允许使用更简单的处理途径，除了循环洗衣机和洗手站。同样，单独处理灰水来源会导致较低的 LRT，但较低的所需 LRT 通常不允许使用更简单的处理途径。例如，与 1000 人规模的室内混合灰水再利用相比，循环洗衣机的 LRT 低约 3 个对数单位，但两种情况都需要使用膜生物反应器、氯化和紫外线消毒。然而，如果：(i) 对于基于家庭的系统使用更保守的健康基准，考虑到处理后的灰水在家庭中病原体传播中的相对重要性降低，以及 (ii) 可以验证单元工艺的更高对数去除值 (LRV)，则对于小型和应用规模的再利用，可能可以采用更简单的处理途径。能够为更多器具规模的再利用系统提供更简单的处理途径。
