Smeets P W M H, van Dijk J C, Stanfield G, Rietveld L C, Medema G J
Kiwa Water Research, PO Box 1072, 3430 BB, Nieuwegein, The Netherlands.
J Water Health. 2007;5 Suppl 1:107-18. doi: 10.2166/wh.2007.140.
Quantitative Microbiological Risk Assessment (QMRA) is increasingly being used to complement traditional verification of drinking water safety through the absence of indicator bacteria. However, the full benefit of QMRA is often not achieved because of a lack of appropriate data on the fate and behaviour of pathogens. In the UK, statutory monitoring for Cryptosporidium has provided a unique dataset of pathogens directly measured in large volumes of treated drinking water. Using this data a QMRA was performed to determine the benefits and limitations of such state-of-the-art monitoring for risk assessment. Estimates of the risk of infection at the 216 assessed treatment sites ranged from 10(-6.5) to 10(-2.5) person(-1) d(-1). In addition, Cryptosporidium monitoring data in source water was collected at eight treatment sites to determine how Cryptosporidium removal could be quantified for QMRA purposes. Cryptosporidium removal varied from 1.8 to 5.2 log units and appeared to be related to source water Cryptosporidium concentration. Application of general removal credits can either over- or underestimate Cryptosporidium removal by full-scale sedimentation and filtration. State-of-the-art pathogen monitoring can identify poorly performing systems, although it is ineffective to verify drinking water safety to the level of 10(-4) infections person(-1) yr(-1).
定量微生物风险评估（QMRA）越来越多地被用于补充通过检测指示菌的缺失来对饮用水安全进行的传统验证。然而，由于缺乏关于病原体归宿和行为的适当数据，QMRA的全部益处往往无法实现。在英国，对隐孢子虫的法定监测提供了一个独特的数据集，该数据集是在大量经过处理的饮用水中直接测量得到的病原体数据。利用这些数据进行了QMRA，以确定这种最先进的监测在风险评估方面的益处和局限性。在216个评估的处理地点，感染风险估计值范围为10^(-6.5)至10^(-2.5)人^(-1)天^(-1)。此外，在8个处理地点收集了原水中的隐孢子虫监测数据，以确定如何为QMRA目的量化隐孢子虫的去除情况。隐孢子虫的去除率从1.8到5.2个对数单位不等，且似乎与原水中隐孢子虫的浓度有关。应用一般去除系数可能会高估或低估全尺寸沉淀和过滤对隐孢子虫的去除效果。最先进的病原体监测可以识别运行不佳的系统，尽管要将饮用水安全验证到10^(-4)人^(-1)年^(-1)的感染水平是无效的。
