AWWA JAW70992

Chloramine is typically viewed as a far superior disinfectant to free chlorine in terms of bacterial control because it persists longer in the distribution system. However, if nitrification is present, chloramine can quickly disappear and the remaining available ammonia could stimulate the growth of pathogenic bacteria in home plumbing. It is not news that nitrification can accelerate chloramine decay, but some studies have raised suspicions about whether chloramines are as persistent as free chlorine. Because of the potential health concerns with chloramine use, this study was conducted to examine the relative stability and disinfection effectiveness of chlorine and chloramine in various plumbing materials both with and without nitrification present. Absent nitrification, chloramine was more stable than chlorine. In the presence of nitrification, however, the relative stability of the disinfectants was shown to depend on the relative rates of corrosion and nitrification. The authors advise utilities already using chloramines to routinely monitor disinfectant stability and nitrification in premise plumbing and implement prevention strategies to stop the occurrence of nitrification. Includes 42 references, tables, figures.