Data from US distribution systems that chloraminate are evaluated as predictors of nitrification. Utilities in the United States that chloraminate were surveyed to evaluate the incidence of nitrification in distribution systems and determine whether nitrification can be predicted from basic system and water quality data. An estimated two thirds of medium and large US systems that chloraminate experience nitrification to some degree. About every fourth surveyed utility reported moderate to severe nitrification problems. In addition, every fourth utility did not know the extent of nitrification in its system. The incidence of nitrification was more frequent during summer or when the temperature was greater than 15°C (59°F); nevertheless, several sites sampled under cold water conditions—i.e., below 10°C (50°F)—also evidenced nitrification. No one water quality parameter by itself may be a good indicator of nitrification, but several important factors should be evaluated collectively—nitrite, nitrate, chloramine dosage and residual, ammonia, pH, heterotrophic bacterial counts, and dissolved oxygen.

his article continues the discussion presented by Wilczak et al 1 in the companion article on page 74. The primary objective of this research was to develop practical utility information regarding the occurrence and control of nitrification in drinking water systems using chloramines for secondary disinfection. Specific research goals were to • document nitrification control practices used by utilities,• develop a laboratory method to demonstrate nitrification response under various water quality and operational parameters, and• establish a recommended monitoring and control strategy.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.

Tests indicate particulate fraction of total organic carbon in a natural water is more accurately measured by the combustion method than by the ultraviolet–persulfate oxidation method. The Disinfectants/Disinfection By‐products (D/DBP) Rule includes total organic carbon (TOC) as a regulatory compliance parameter with the idea that TOC concentration is a direct indicator of the potential for DBP formation upon chlorination. A comprehensive study was conducted to evaluate the ability of the two most common methods—ultraviolet (UV)–persulfate oxidation and catalytic combustion—to measure the particulate fraction of the TOC in water and determine whether this fraction contributes to DBP formation. Results showed that particulate TOC fraction in a natural water was more accurately measured by the combustion method. Therefore, the method used by a water utility to evaluate TOC removal through a water treatment plant can significantly affect the chemical dosages required for regulatory compliance and treatment cost. Furthermore, chlorination testing results suggest that the DBP formation reactions may not be affected by particulate TOC, leading the authors to propose that dissolved organic carbon rather than TOC is a more appropriate indicator of DBP formation potential in water treatment.