Payment P
Institut national de la recherche scientifique (INRS)-Institut Armand-Frappier, Université du Québec, Laval, Canada.
Can J Microbiol. 1999 Aug;45(8):709-15.
To evaluate the inactivating power of residual chlorine in a distribution system, test microorganisms (Escherichia coli, Clostridium perfringens, bacteriophage phi-X 170, and poliovirus type 1) were added to drinking water samples obtained from two water treatment plants and their distribution system. Except for Escherichia coli, microorganisms remained relatively unaffected in water from the distribution systems tested. When sewage was added to the water samples, indigenous thermotolerant coliforms were inactivated only when water was obtained from sites very close to the treatment plant and containing a high residual chlorine concentration. Clostridium perfringens was barely inactivated, suggesting that the most resistant pathogens such as Giardia lamblia, Cryptosporidium parvum, and human enteric viruses would not be inactivated. Our results suggest that the maintenance of a free residual concentration in a distribution system does not provide a significant inactivation of pathogens, could even mask events of contamination of the distribution, and thus would provide only a false sense of safety with little active protection of public health. Recent epidemiological studies that have suggested a significant waterborne level of endemic gastrointestinal illness could then be explained by undetected intrusions in the distribution system, intrusions resulting in the infection of a small number of individuals without eliciting an outbreak situation.
为评估配水系统中余氯的灭活能力，将测试微生物（大肠杆菌、产气荚膜梭菌、噬菌体φ-X 170和1型脊髓灰质炎病毒）添加到从两家水处理厂及其配水系统采集的饮用水样本中。除大肠杆菌外，在所测试的配水系统的水中，其他微生物相对未受影响。当向水样中添加污水时，只有从非常靠近处理厂且余氯浓度高的地点采集的水，其中的耐热大肠菌群才会被灭活。产气荚膜梭菌几乎未被灭活，这表明诸如蓝氏贾第鞭毛虫、微小隐孢子虫和人类肠道病毒等最具抗性的病原体不会被灭活。我们的结果表明，在配水系统中维持自由余氯浓度并不能显著灭活病原体，甚至可能掩盖配水系统的污染事件，因此只会提供一种虚假的安全感，而对公众健康几乎没有实际保护作用。近期的流行病学研究表明，地方性胃肠道疾病存在显著的水传播水平，这可能是由于配水系统中未被检测到的入侵所致，这些入侵导致少数人感染，但未引发疫情。
