In recent decades, natural swimming pools (NSPs) have gained popularity in Europe, especially in Germany and Austria. NSPs differ from swimming pools in that they utilize biological treatment processes based on wetland processes with no disinfection residual. However, data are missing on the specific log-reduction performance of NSPs to address enteric virus, bacteria, and parasitic protozoa removal considered necessary to meet the North American risk-based benchmark (<35 illnesses per 1,000 swimming events) set by the USEPA for voluntary swimming. In this study, we examined Canada's first NSP at Borden Park, Edmonton, Canada, to address the following three questions: (1) Given normal faecal shedding rates by bathers, what is the total log reduction (TLR) theoretically needed to meet the EPA benchmark? (2) what is the in-situ performance of the NSP based on spiking suitable microbial surrogates (MS2 coliphage, Enterococcus faecalis, and Saccharomyces cerevisiae [Baker's yeast])? and (3) how much time is required to reach acceptable bather risk levels under different representative volume-turnover rates? A reverse-quantitative microbial risk assessment (QMRA) revealed that of the four reference pathogens selected (Norovirus, Campylobacter, Cryptosporidium, and Giardia), only Norovirus was estimated to exceed the risk benchmark at the 50th, 75th, and 95th percentiles, while Campylobacter was the only other reference pathogen to exceed at the 95th percentile. Log-reduction values (LRVs) were similar to previous reports for bacterial indicators, and novel LRVs were estimated for the other two surrogates. A key finding was that more than 24 h treatment time would be necessary to provide acceptable bather protection following heavy bather use (378 bathers/day for main pool and 26 bathers/day for children's pool), due to the mixing dynamics of the treated water diluting out possible residual pool faecal contamination. The theoretical maximum number of people in the pool per day to be below USEPA's 35 gastro cases in 1,000 swimming events was 113, 47, and 8, at the 50th, 75th, and 95th percentiles. Further, the use of ultra-violet disinfection to the pool return flow had little effect on reducing the treatment time required.

近几十年来，天然游泳池 (NSP) 在欧洲越来越受欢迎，尤其是在德国和奥地利。NSP 与游泳池的不同之处在于它们利用基于湿地过程的生物处理过程，没有消毒残留。然而，关于 NSP 的特定对数减少性能的数据缺失，以解决被认为是满足北美基于风险的基准（每 1,000 次游泳事件 <35 种疾病）所必需的肠道病毒、细菌和寄生原生动物去除问题。自愿游泳。在这项研究中，我们在加拿大埃德蒙顿博登公园检查了加拿大的第一个 NSP，以解决以下三个问题：(1) 鉴于沐浴者的正常粪便排出率，理论上满足 EPA 所需的总对数减少 (TLR) 是多少基准？(2) 什么是基于加入合适的微生物替代物（MS2大肠杆菌、粪肠球菌和酿酒酵母[面包酵母]）的 NSP的原位性能？(3) 在不同的代表性体积周转率下，达到可接受的入浴者风险水平需要多长时间？一项反向定量微生物风险评估 (QMRA) 显示，在选定的四种参考病原体（诺如病毒、弯曲杆菌、隐孢子虫和贾第虫）中，估计只有诺如病毒在第 50、75 和 95 个百分位超过风险基准，而弯曲杆菌是唯一超过第 95 个百分位的其他参考病原体。对数减少值 (LRV) 与之前关于细菌指标的报告相似，并且估计了其他两个替代物的新 LRV。一个重要的发现是，在大量使用沐浴后，需要超过 24 小时的处理时间才能提供可接受的沐浴保护（主游泳池每天 378 人，儿童游泳池每天 26 人）)，由于处理过的水的混合动力学稀释了可能的残留池粪便污染。在 1,000 次游泳项目中，每天泳池中低于美国环保署规定的 35 例胃病病例的理论最大人数分别为 113、47 和 8，分别位于第 50、75 和 95 个百分位数。此外，对水池回流使用紫外线消毒对减少所需的处理时间几乎没有影响。