Microbial contamination in the groundwater of Aligarh city

Aligarh city is a part of the central Ganga Plain. The Quaternary alluvium in the area has been deposited on a faulted and eroded surface of upper Vin dhyan shale which comprises sand, silt and clay with occasional calcrete. b eds. There are three levels of aquifer in the alluvium of the area. The top , aquifer lies at a depth of 9-66 m and is highly vulnerable to microbial a nd chemical pollution. The present paper evaluates the microbial contaminat ion of groundwater, which was analysed using water samples from shallow (ha nd pumps) and deep aquifers (tube wells) at different sites during the summ er season. Samples were examined for total aerobic heterotrophic bacterial load by the plate count method and the multiple tube dilution method for de termining the most probable number (MPN) index of total coliform and faecal coliform bacteria, Microbiological analysis showed that microbial (heterot rophic bacterial) contamination in groundwater was maximum in wells with ha nd pumps (private) and least in tubewell water. Total coliform and faecal c oliform contamination are also found comparatively more in wells with hand pumps than tubewells. It indicated that those who drink groundwater from ha nd pump (India Mark) may be at increased risk of infection and disease from pathogenic bacteria. The level of contamination is expected to increase in the rainy season. Immediate attention is hence needed to monitor all publi c drinking water systems for total coliform and faecal coliform contaminati ons and to assess the pathogenic potential of microbial contaminants.