This study confirms the finding of others that once treated in a household by what ever method, drinking water can be easily contaminated during storage. Boiling water for disinfection takes time, is energy intensive, and not everyone follows through to actually do it. Despite the disadvantages of using a chlorine solution (e.g., sodium hypochlorite) for disinfection, having a slight chlorine residual in the water still remains the best way to addess potential contamination during storage.
Psutka, R., Peletz, R., Michelo, S., Kelly, P., and Clasen, T. Assessing the Microbiological Performance and Potential Cost of Boiling Drinking Water in Urban Zambia. Environ Sci Technol. 2011 Jun 23.
London School of Hygiene and Tropical Medicine, Keppel St., London WC1E 7H, United Kingdom.
This six-week study in peri-urban Zambia assessed the microbiological effectiveness and potential cost of boiling among 49 households without a water connection who reported “always” or “almost always” boiling their water before drinking it.
Source and household drinking water samples were compared weekly for thermotolerant coliforms (TTC), an indicator of fecal contamination. Demographics, costs, and other information were collected through surveys and structured observations.
Drinking water samples taken at the household (geometric mean 7.2 TTC/100 mL, 95% CI, 5.4-9.7) were actually worse in microbiological quality than source water (geometric mean 4.0 TTC/100 mL, 95% CI, 3.1-5.1) (p < 0.001), although both are relatively low levels of contamination.
Only 60% of drinking water samples were reported to have actually been boiled at the time of collection from the home, suggesting over-reporting and inconsistent compliance. However, these samples were of no higher microbiological quality.
Evidence suggests that water quality deteriorated after boiling due to lack of residual protection and unsafe storage and handling. The potential cost of fuel or electricity for boiling was estimated at 5% and 7% of income, respectively.
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