Evaluating <i>Cryptosporidium</i> Oocyst Removal in SSF: Impact of Underwater Skimming and Dry Skimming

Data for Evaluating <i>Cryptosporidium</i> Oocyst Removal in SSF: Impact of Underwater Skimming and Dry Skimming<br><i>Cryptosporidium</i> is a protozoan parasite that presents significant challenges to water supply security due to its resilience against conventional chemical disinfection. This study evaluates the effectiveness of two slow sand filter (SSF) skimming techniques—dry skimming (DS) and underwater skimming (UWS)—in removing <i>Cryptosporidium</i> oocysts under pilot-scale conditions using 10 filters. Oocyst retention was monitored during dosing, post-dosing, and following each skimming event. Results demonstrated that UWS achieved superior pathogen removal, evidenced by fewer oocyst breakthroughs and higher cumulative log retention values (LRVs). During dosing, UWS filters attained LRVs consistently exceeding 6.6, whereas DS filters averaged 5.6. In the post-dosing period, UWS retained LRVs above 6.9, while DS averaged 5.9. A quantitative microbial risk assessment (QMRA) indicated a substantially lower probability of illness from oocyst breakthrough in UWS-treated water, with a daily risk of ~2.6 × 10⁻⁶ for immunocompetent individuals, compared to up to 8.2 × 10⁻⁶ in DS-treated water—equating to a 3.2-fold risk reduction. These findings highlight that the UWS maintenance technique enhances SSF operation by improving pathogen retention while enabling minimal filter downtime, thereby contributing to improved water safety and public health protection. The work also provides novel empirical data and theoretical predictions regarding the potential risk of <i>Cryptosporidium</i> penetration or compromised water quality arising from the routine requirement to skim SSFs.慢砂滤池（Slow Sand Filter, SSF）隐孢子虫（Cryptosporidium）卵囊去除效果评估数据集：水下撇渣与干式撇渣的影响 隐孢子虫（Cryptosporidium）是一种原生动物寄生虫，因其对常规化学消毒具有较强抗性，对供水安全构成严峻挑战。本研究以10组中试规模滤池为对象，评估了两种慢砂滤池（Slow Sand Filter, SSF）撇渣工艺——干式撇渣（Dry Skimming, DS）与水下撇渣（Underwater Skimming, UWS）——对隐孢子虫卵囊的去除效果。研究监测了投加期、投加后以及每次撇渣操作后的卵囊截留情况。结果表明，水下撇渣工艺的病原体去除效果更优，具体体现为卵囊穿透事件更少、累积对数保留值（Log Retention Values, LRVs）更高。在投加阶段，采用水下撇渣工艺的滤池LRVs始终高于6.6，而干式撇渣滤池的平均LRVs为5.6。在投加后阶段，水下撇渣工艺的LRVs维持在6.9以上，干式撇渣工艺的平均LRVs为5.9。定量微生物风险评估（Quantitative Microbial Risk Assessment, QMRA）结果显示，经水下撇渣工艺处理的水体中，因卵囊穿透引发疾病的概率显著更低：免疫功能正常人群的每日感染风险约为2.6×10⁻⁶，而干式撇渣处理水体的该风险最高可达8.2×10⁻⁶，相当于将疾病风险降低了3.2倍。上述研究结果表明，水下撇渣运维工艺通过提升病原体截留效果、同时将滤池停机时间降至最低，优化了慢砂滤池的运行效能，进而助力提升供水安全性与公共健康保护水平。本研究还针对因慢砂滤池常规撇渣操作可能引发的隐孢子虫穿透或水质恶化风险，提供了全新的实测数据与理论预测结果。