AWWA JAW61920

Nitrification is a common problem faced by utilities using chloramines for distribution system residual maintenance. Nitrification involves the growth of ammonia-oxidizing bacteria and the resulting production of nitrite, which exerts a chloramine demand. This can lead to a sometimes precipitous loss of chloramine. Once nitrification becomes established, it can be difficult to bring under control. This study was undertaken to help develop tools for dealing with nitrification. This article assesses the usefulness, using both bench- and full-scale data, of a previously proposed criterion of 0.05 mg/L nitrite-nitrogen as a critical threshold for confirming nitrification in chloraminated distribution systems. In this study, the investigators found that this level of nitrite-nitrogen has value in detecting nitrification, but that the 0.05 mg/L nitrite-nitrogen level is too high to predict nitrification before it becomes well established. A loss of total chlorine or monochloramine residual, however, could give early warning of a potential nitrification episode. The authors conclude that, for utilities concerned about nitrification, multiple water quality parameters should be analyzed simultaneously, if possible, to develop time-series trends specific to a given water utility. If adequate resources are not available to test for a suite of parameters, total chlorine residual data can serve as an early warning sign of potential nitrification. Drops in total chlorine residual should then instigate additional, targeted analyses (such as nitrite and ammonia, among others). Includes 24 references, tables, figures.