Removal of Disinfection By-Products from Drinking Water: Influencing Factors and Physico-Chemical Treatment Processes

Disinfection is one of the most essential procedures in drinking water treatment. Among the various methods of disinfection, chlorination is among the most common methods being economical, reliable, easily-operable, easily-measurable, and efficient enough to maintain residual disinfecting effects for sufficient time period. However, it has been reported that chlorine does react chemically with the naturally available carbon-based compounds in water and produces disinfection by-products (DBPs) such as trihalomethanes. Chloroform (CHCl3) is one of the most common trihalomethanes. It has been reported that both short-term and long-term exposure to trihalomethanes result in adverse health impacts. As per WHO standards, the permissible limits for various trihalomethanes span from 60 μg/L to 300 μg/L. Formation and concentration of DBPs depend upon type and characteristics of source water, type of disinfectants used, operational conditions, temperature, pH, and contact time of chlorinated water with DBPs precursors in water treatment plants and water distribution network. Various treatment techniques have been evolved for the removal of trihalomethanes, such as enhanced coagulation, membrane separation, reverse osmosis, adsorption, filtration, advanced oxidation, etc.; however, each process has its own advantages as well as shortcomings. In this chapter, summary of various physico-chemical processes for the removal of DBPs shall be discussed, with major focus on the two best available techniques, viz. enhanced coagulation and activated carbon adsorption. Moreover, the applicability of alternative disinfectants shall also be explored.