Trihalomethanes monitoring and their seasonal variation in urban municipal water supply system in North India

This study reports the trihalomethanes generated during disinfection within the water distribution network of Delhi, India. For 12 months study period tap water samples were collected (n = 216) from the command areas of nine water treatment plants to provide a comprehensive picture of spatial and seasonal variation of trihalomethanes in the city. The mean concentrations of chloroform, bromodichloromethane, dibromochloromethane, bromoform were 34.62 ± 13.09 μg/l, 25.39 ± 11.75 μg/l, 15.83 ± 9.66 μg/l, 1.74 ± 1.51 μg/l respectively, the total trihalomethanes concentration ranged between 11.41–175.54 μg/l. Chloroform was prevalent accounting 45% in total trihalomethanes followed by bromodichloromethane, dibromochloromethane, bromoform accounting 33%, 20%, and 2% respectively. Trihalomethanes concentrations were found to be increasing during summer season and got decreased in the winter and post-monsoon season. Total trihalomethanes levels were found to be highest at Chandrawal water treatment plant command area (85.35–148.38 μg/l) and lowest at Okhla water treatment plant command area (11.41–63.38 μg/l). In many samples trihalomethanes concentrations were discovered to be higher than the allowable limit specified by Indian Standards. A strong relationship between trihalomethanes formation with total organic carbon (r = 0.934) and residual chlorine (r = 0.801) accentuate its capability for monitoring disinfection by-products in the distribution network. Results showed that considerable levels of trihalomethanes are generated in the study area, therefore the competent authorities must take the appropriate steps to regularly monitor the trihalomethanes in drinking water. The findings of this study may help to provide operators with invaluable information on drinking water quality and open up several chances to enhance water quality management.