Ecole Polytechnique de Montreal, NSERC Industrial Chair on Drinking Water, Civil Geological and Mining Engineering, CP 6079, Succ. centre-ville, Montreal, Quebec, Canada.
Environ Sci Technol. 2010 Jan 1;44(1):269-77. doi: 10.1021/es901988y.
The 1990s epidemiological studies by Payment and colleagues suggested that an increase in gastrointestinal illnesses observed in the population consuming tap water from a system meeting all water quality regulations might be associated with distribution system deficiencies. In the current study, the vulnerability of this distribution system to microbial intrusion was assessed by characterizing potential sources of contamination near pipelines and monitoring the frequency and magnitude of negative pressures. Bacterial indicators of fecal contamination were recovered more frequently in the water from flooded air-valve vaults than in the soil or water from pipe trenches. The level of fecal contamination in these various sources was more similar to levels from river water rather than wastewater. Because of its configuration, this distribution system is vulnerable to negative pressures when pressure values out of the treatment plant reach or drop below 172 kPa (25 psi), which occurred nine times during a monitoring period of 17 months. The results from this investigation suggest that this distribution system is vulnerable to contamination by intrusion. Comparison of the frequency of occurrence of negative pressure events and repair rates with data from other distribution systems suggests that the system studied by Payment and colleagues is not atypical.
20 世纪 90 年代，Payment 及其同事的流行病学研究表明，在饮用符合所有水质规定的自来水的人群中，胃肠道疾病的发病率增加可能与供水系统的缺陷有关。在当前的研究中，通过描述管道附近潜在的污染来源并监测负压的频率和幅度，评估了该供水系统对微生物入侵的脆弱性。在水淹的空气阀室的水中，比在管道沟槽的土壤或水中，更频繁地回收到粪便污染的细菌指标。这些不同来源的粪便污染程度与河水而不是污水更为相似。由于其配置，当厂外压力值达到或低于 172kPa（25psi）时，该供水系统在 17 个月的监测期内发生了 9 次，容易受到负压的影响。该调查结果表明，该供水系统容易受到入侵污染。将负压事件的发生频率和修复率与其他供水系统的数据进行比较表明，Payment 及其同事研究的系统并非特例。
