Microbiological quality of supply water in mega and metro cities of India and their management: An overview

The microbial quality of supplied water in urban areas is of vital concern in India. Supply of safe drinking water in cities is ensured by Urban Local Bodies either through the piped water supply drawing water from surface water bodies or bore wells. However, intermittent supply, prolonged storage, leakages in the water pipeline, sewerage system, poor hygiene, and sanitation facilities lead to water contamination. Mega and metro cities in India generates a million liters of wastewater per day, only a small percentage of which is treated and a considerable quantity of untreated water finds its way into surface water or pollute groundwater resources. This contaminated water provides a suitable medium for microbial growth. Waterborne microbes such as E. coli and enterococcus are used as indicators of fecal contamination. However, most E. coli are usually non-pathogenic and an essential part of the human intestinal tract. However, enterohemorrhagic or Shiga toxin-producing E. coli (EHEC or STEC) and enterotoxigenic E. coli (ETEC) are involved in a range of diseases from diarrhea to hemorrhagic colitis and hemolytic-uremic syndrome. The infectious dose of pathogenic E. coli is significantly less (~ 50 CFU) in humans, and ingestion of even a few cells may cause diseases. Therefore, a better understanding of the pathogenesis, early screening of pathogenic strains, regular monitoring, strict compliance with standards, effective management of microbially contaminated water by adopting advanced techniques, and mass awareness are essential to reduce acute outbreaks in urban areas.