Assessment of Heavy Metal and E. coli Contamination in Water Sources of the East and South Districts, Sikkim Himalaya, India

Water quality degradation exerts immense pressure on the availability of suitable freshwater resources. Deterioration in water quality has led to a decrease in the available water for consumption purposes. The excess concentration of heavy metals and faecal contamination in water pose a risk to human health. This study looks at heavy metal contamination and microbial contamination in different water samples of the east and south districts of Sikkim. The sampling extended for tap water, springs, and river water samples across monsoon, post-monsoon, and pre-monsoon seasons. The concentrations of heavy metals in most samples, except for some river water samples were under permissible limits set by the Bureau of Indian Standards (BIS) and World Health Organisation (WHO). Indices such as Heavy Metal Pollution Index (HPI), Heavy Metal Evaluation Index (HEI), and Contamination Index (Cd) show a higher proportion of contamination in the river water samples than in tap and spring water samples and during monsoon season. Sources apportionment of metal concentration show geogenic as well as anthropological sources. For microbial contamination Most Probable Number (MPN) index was used showing possible faecal contamination in all water samples rendering them unsuitable for drinking purposes without appropriate treatment. The study also highlights the urgent need for effective measures to address faecal contamination in the water sources of the study area.