Seasonal variation of trihalomethane formation potential in treated water supplies of Delhi City (India).

The main goal in using chlorine as water disinfectant is to protect the water in the distribution systems against microbial contamination and to prevent and control re-growth of microorganisms in the water distribution system. Organics in water have the potential to generate harmful disinfection by-products (DBPs) such as trihalomethanes (THMs) as a result of their reaction with chlorine. DBPs are increasingly recognized as cancerous agents. Residual chlorine concentration, temperature and pH are the major factors that influence the rate and degree of THMs formation. Trihalomethanes formation potential (TFP) is very useful test to assess the level of the formation of trihalomethanes. Seasonal variations of TFP of post chlorinated treated water were investigated at six water treatment plants (WTPs) in Delhi City (India).The post chlorinated treated water samples from Bhagirathi, Sonia Vihar, Wazirabad, Nangloi, Okhla, and Haiderpur WTPs were collected just at the outlet before water supply to the consumers. The investigation was based on an intensive bi-monthly sampling program, undertaken from May 2007 to March 2008. Correlation among TFP, residual chlorine, temperature and pH, and their variation throughout the year is also discussed in this paper.