AWWA JAW41449

Of US water systems that chloraminate, an estimated two thirds experience some degree of nitrification in the distribution system. Measures utilities use to control nitrification were investigated through field sampling, evaluation of utility data, laboratory tests, and case studies of systems that have evaluated or attempted to control nitrification episodes. Effective control methods included instituting periodic breakpoint chlorination, reducing the available ammonia concentration, increasing chloramine residuals, cleaning the distribution system, and decreasing system detention time. Some control methods were superior for controlling a specific nitrification episode, whereas others showed more promise for reducing the long-term potential for nitrification occurrence. According to the authors, the most important steps utilities can take to control nitrification are to thoroughly understand their systems' chloramine chemistry and to establish an effective monitoring strategy. Includes 26 references, tables, figure.