本研究旨在确定在哪里存在未发现大肠菌群的余氯浓度，并调查某些大肠菌群可能比其他大肠菌群更好地抵抗分配系统中的游离氯。样本来自七个小型市政供水系统。对数据的统计分析表明，对于游离氯残留量差异很大的系统，大肠菌群密度与小于0.2 mg/L的游离氯残留量之间没有关联。在游离氯残留量小于0.2 mg/L的样品中发现阴沟肠杆菌和聚集肠杆菌。 2 mg/L，而大肠杆菌仅在没有游离氯残留的样品中发现。包括15个参考文献、表格和图表。

This research was conducted to determine where there is a residual chlorine concentration at which coliforms are not found and to investigate the possibility that some species of coliforms may resist free chlorine in distribution systems better than other coliforms. Samples were collected from seven small municipal water systems. Statistical analyses of the data showed that for systems in which the free chlorine residuals vary considerably, there is no association between coliform density and a free chlorine residual of less than 0.2 mg/L. Enterobacter cloacae and Enterobacter agglomerans were found in samples with a free chlorine residual less than 0.2 mg/L, whereas Escherichia coli was found only in samples without a free chlorine residual. Includes 15 references, tables, figure.