Microbiological quality of drinking water distributed by water tankers in Kathmandu valley, Nepal

Background: The health and well-being of human is closely linked to the quality of water used for drinking purposes. Water quality in developing countries like Nepal is deteriorating owing to chemical and biological contamination. Majority of water borne diseases in Nepal are due to consumption and usage of contaminated water. In the past pathogenic microorganisms like Salmonella spp and Vibrio spp, were isolated from drinking water which suggests the pressing concern for the inhabitants of Kathmandu Valley. Indicator bacteria like coliforms provide a good assessment of fecal contamination of drinking water.

Objective: Present study was carried out to determine the microbiological quality of drinking water distributed by water tankers in Kathmandu valley.

Methods: A total of 77 water samples were collected for microbiological assessment which included 60 on-site water sample from water tankers, 6 from reservoirs and 11 from other water sources. The collected water samples were aseptically processed in the laboratory of Kantipur College of Medical Science, Kathmandu, Nepal. Collection and processing of water samples were performed following standard guidelines as referred for most probable number technique (MPN).

Result: We categorized water in four quality basis as excellent, satisfactory, intermediate and unsatisfactory. We found 57.1% of water sample to fall in unsatisfactory conditions while only 14.3% of the sampled water was of excellent quality. Fecal coliforms, which is regarded as indicator organisms of fecal contamination was found in source water 36.3% (4/11), reservoir water 16.6% (1/6) and in water tanker 50.0% (30/60). The majority of microorganisms isolated were Klebsiella spp. (33.1%) followed by Citrobacter spp. (30.5%), Enterobacter spp.(19.0%) and E.coli (17.4%). Only 66.7 % of source water was chlorinated while only 28.3 % of tankers distributed chlorinated water. Surprisingly, coliforms were also isolated from chlorinated tanker's water implying the viability of pathogenic microorganisms and ineffectiveness of chlorination process.

Conclusion: We found water sources, reservoir and distributed water to be microbiologically contaminated by fecal coliforms. Providers should select and collect water from safe sources and distribute only chlorinated water. Consumers should practice point-of-use drinking water disinfection process to protect themselves from acquiring water borne diseases.