Evaluation of Escherichia coli as Indicator of Point-of-Use Chlorination Efficiency of Drinking Water

In this study, the relevance of the presence of Escherichia coli in drinking water as an indicator of point-of-use chlorination efficiency is examined. The survival of clinical isolates of human enteric pathogenic bacteria (Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Shigella dysenteriae, Staphylococcus aureus, Streptococcus faecalis and Vibrio cholerae) as well as E. coli was monitored as a function of effective germicidal concentration and contact time. The inactivation kinetics indicated that the minimum effective dose for three-log units (99.9%) inactivation of E. coli (C·T99.9% = 10 mgl^-1 -min) can sufficiently eliminate the other pathogens (C·T_99.9% ranged from 5.6–10.5 mgl^-1 -min); the exception being K. pneumoniae, which required more than 1.4-times higher dose. In general, the results implied that the branded hypochlorite solution should effectively inactivate almost all vegetative bacteria in household drinking water at the manufacturer’s recommended dosage of 0.5 mgl^-1 after at least 30 minutes contact time. The application of point-of-use chemical disinfectants to drinking water in households will significantly reduce the incidence of water-borne infections particularly in rural communities where central treatment of water is mostly unavailable.