131-Assessment of Drinking Water Quality in Delhi City.

Abstract

Assessment of water quality at treatment plant and consumer ends in Delhi city was undertaken during June to November 2006 to assess the quality as per BIS 10500:1991. Physicochemical and microbiological quality of treated water from five treatment plants was assessed fortnightly during the survey period. Water samples were also collected from private taps and public hydrants used by consumers from 900 identified locations from distribution network. Samples from distribution system were analyzed for total and feacal coliforms, along with free residual chlorine. It is observed from assessment of treated water quality at treatment plants that essential characteristics such as pH, turbidity, total hardness and chloride are well within the desired limits as per BIS norms. Free residual chlorine ranged between 1.5 to >2.0 mg/L and no sample was found to contain total or feacal coliform. It is observed form analysis of water sample at consumer ends that free residual chlorine was less than 0.2 mg/L in 13.4% samples. Coliform were detected in 10°/0 of the samples and their count was found to exceed 10 in 3.9% samples. Faecal Coliforms were detected in 4.1% samples. It is observed that water gets contaminated in distribution network, even if treated adequately at treatment works to render it safe and acceptable. This could be attributed to intermittent mode of water supply, use of inline booster pump by consumers and leakages in service pipelines. It is desired that quality of water be safeguarded especially during distribution phase to protect the public heath.