Coliform occurrence and chlorine residual in small water distribution systems

Samples were collected from seven small (0.09–11 ML/d [0.025–3 mgd]) 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 <0.2 mg/L. Enterobacter cloacae and Enterobacter agglomerans were found in samples With a free chlorine residual >0.2 mg/L, whereas Escherichia coli was found only in samples without a free chlorine residual.