AWWA ACE91006

As part of a program to develop methods of controlling nitrification in the Metropolitan Water District of Southern California distribution system, batch disinfection assays were performed on ammonia-oxidizing bacteria (AOB) with the use of chloramines. The purpose of this study was to assess the ability of AOB to survive and regrow following exposure to various concentrations of chloramines and thus to provide utilities with some idea of the chloramine conditions required to prevent nitrification. The concentration of chloramines necessary to control nitrification was found to be temperature-dependent. Furthermore, regardless of temperature or residual, increasing the Cl2:N ratio of 5:1 is advantageous because no excess ammonia is available for the growth of nitrifiers. The results tend to be representative of a storage tank rather than a reservoir or dynamic pipeline system because the study was based on batch experiments.