Resuscitation of Bacteria after Dechlorination of Treated Drinking Water

In this study, the effects of initial bacterial load (102 , 104 and 106 cells/ml) and dechlorination idiosyncrasy on the efficacy of varying concentrations (0.018–0.126% v/v applied for 30 minutes) of a point-of-use chlorine-based proprietary disinfectant (WaterCare®) were investigated in drinking water. Results indicated that higher initial cell populations significantly affected the efficacy of the disinfectant.Subsequent dechlorination of the disinfected water resulted in resuscitation of bacteria. This was demonstrated after 1440 minutes post-dechlorination for Salmonella typhi and after at least 120 minutes for Escherichia coli, Proteus vulgaris and Shigella dysenteriae, particularly at lower disinfectant concentrations (0.018–0.054% v/v). Thus, whilst the use of WaterCare® at the recommended dosage(0.072% v/v or 10 ml to 25 litres of clean water for 30 minutes) may produce microbiologically safe drinking water high initial microbial load and post-disinfection residual chlorine loss may limit its efficacy. Keywords: Bacterial resuscitation, Escherichia coli, Dechlorination, Drinking water, Salmonella typhi, WaterCare