Coliform Persistence in Highly Chlorinated Waters

Abstract

This study demonstrates how coliform organisms might exist under hours of contact with one mg/l of chlorine or even greater concentrations. The investigation discovered a train of events whereby a Crustacea harboring coli forms, while passing through a spigot, becomes ruptured by the velocity of the water, and is almost immediately flushed into a sample bottle containing sodium thiosulphate. The chlorine is neutralized and the coliforms are distributed throughout the sample, resulting in illogical bacteriologic results.

Examination of the behaviour of Escherichia coli in biofilms established in laboratory-scale units receiving chlorinated and chloraminated water

“…These results showed the effectiveness of monochloramine in preventing the attachment of E. coli during early biofilm formation as well as the resistance of E. coli to chlorination and their attachment in young biofilms. This observation supported the findings of others showing the capability of coliform bacteria to survive high disinfectant doses of chlorine (Tracy et al, 1966;LeChevallier et al, 1988b). Previous investigators have shown that many coliforms survive standard chlorine residuals as chlorine-injured cells, with subsequent release in distribution systems (McFeters et al, 1986).…”

Chloramination: its effect on distribution system water quality

“…In Hopewell, free chlorine doses ranged from 1.7 to 3.9 mg/L, whereas in Muncie they ranged from 1.7 to 2.8 mg/L. Most of the samples positive for coliform bacteria contained chlorine residuals >1.5 mg/L, indicating that maintenance of a free chlorine residual alone is not sufficient to control coliform occurrences in all distribution systems 1 , 2 ,. 48…”

“…Maintenance of a disinfectant residual is intended to control bacterial concentrations throughout the distribution system. However, this alone is not sufficient to control coliform bacteria originating from distribution system biofilms 1 – 1 …”

Removal of particle-associated bacteria by prefiltration and ultraviolet irradiation

“…Planktonic organisms can harbour a variety of bacterial strains. The survival of plankton‐associated coliforms and Vibrio cholera was found to be greater than that of free‐living bacteria in drinking water treatment systems ( Tracy, Camarena & Wing 1966; Huq, Xu, Chowdhury, Islam, Montilla & Colwell 1996; Chowdhury et al . 1997 ).…”