Inactivation of heterotrophic bacterial populations in finished drinking water by chlorine and chloramines

• Published in: Water research (Oxford) 1985, Vol.19 (11), p.1393-1403
• Main Authors: Wolfe, R.L, Ward, N.R, Olson, B.H
• Format: Article
• Language: English
• Subjects: application; Applied sciences; aquatic; bacteria; chloramines; chlorine; disinfection; Drinking water and swimming-pool water. Desalination; Exact sciences and technology; heterotrophic; indigenous; Pollution; preammoniation; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/0043-1354(85)90306-9

The die-off of heterotrophic bacteria from a finished drinking water reservoir, located in southern California, was evaluated using chloramines and free chlorine. Understanding the inactivation of hetertrophic populations is valuable because it reflects the response to disinfection of naturally occurring organisms in their native state and environments. Disinfection studies with the heterotrophic bacterial group were performed during summer and winter months using different chloramine application techniques at pH 6 and 8. In addition, bacteria surviving exposure to chloramines and free chlorine was influenced predominantly by the presence of highly chlorine tolerant, red-pigmented bacteria, identified as Flavobacterium spp. Inactivation by chloramines, though, was chiefly dependent upon the method of application and pH. Viable bacteria recovered from the indigenous population after 60 min of exposure to chloramines (1.0 mg l −1, pH 8) included members of Pseudomonas, Acinetobacter and Flavobacterium. In general, with contact times of 1 h or more, free chlorine and chloramine solutions (1.0–1.6 mg l −1, pH 8) reduced total count levels below 50 colony forming units ml −1.