AWWA ACE54433

The City of Los Angeles, California, has embarked upon a study of the feasibility of converting its distribution system disinfectant residual from free to combined chlorine. The City's large uncovered reservoirs may pose the greatest challenge in the conversion process. Reduction of disinfection byproducts and improvement of the reliability and flexibility of the system supply are the main drivers of the study. Results of bench-scale testing showed that chloramines are a very stable disinfectant in the Los Angeles water. Factors such as temperature, pH, and chlorine to ammonia ratio showed significant impact on the chloramine's stability. A sub-breakpoint chlorination concept showed promise as a possible method to achieve disinfection goals in the water exiting the open distribution reservoirs. Includes reference, table, figures.