Delhi Jal Board (DJB) is responsible for treatment and supply of drinking water in Delhi. The water is treated in five treatment plants and distributed through more than 9000 km long pipeline network spread over an area of 1483 sq. km. Since the onus of ensuring supply of safe drinking water to consumers lies on the water supply agency, DJB desired to adjudge the microbial quality of drinking water at consumer ends in selected areas throughout Delhi city. With this objective, DJB retained NEERI to undertake a short term study for surveillance of microbial quality and residual chlorine in different areas of Delhi.

            Under the studies, more than 900 water samples were collected from 24 areas as shown in the Index Map and analysed for residual chlorine & fecal coliforms, which ranged NIL to >2 mg/L and NIL to >200 CFU/100 mL, respectively.

            Perusal and analysis of the data reveal that residual chlorine was absent (not detected) in 11% of the collected samples while 81% of the samples contained residual chlorine exceeding 0.2 mg/L which is a desirable limit as per BIS standard.

            Total coliforms and fecal coliforms were detected respectively in 10% and 4.1% of water samples collected for examination. It was also observed that 3.9% of samples showed more than 10 total coliform organisms which is the limit ascribed by BIS standard.