Formation of organic chlorine in public water supplies

The formation of purgeable and nonpurgeable organic chlorine was evaluated as a function of the type and concentration of precursor material, the type and dosage of chlorine, pH, temperature, and ammonia concentration. The concentration of organic chlorine in a public water supply can be minimized by avoiding prechlorination, avoiding higher concentrations of chlorine than are necessary for good disinfection, using combined chlorine rather than free chlorine, maintaining a high pH, and withdrawing water from a source with a low concentration of precursor material and a cool temperature. Because the conditions that favor lower concentrations of organic chlorine are generally the same conditions that tend to reduce the efficiency of disinfection, careful consideration must be given to the adequacy of disinfection if efforts are made to reduce organic chlorine formation.