AWWA ACE54376

The interest in chloramine decay rate has been prompted by the change in the distribution system disinfectant from free chlorine to chloramines at many water utilities in the last 20 years. The major drawback of chloramination is biological nitrification as a result of chloramine decay coupled with excessive water age. Deposits or wall materials in system pipelines and storage reservoirs can exacerbate the problem by harboring bacteria causing nitrification and exerting additional chloramine demand. Most of the factors impacting chloramine decay rate have been described in the literature; however, there are experiences from operations that are worth mentioning to complement the subject. This paper attempts to summarize the published factors impacting chloramine decay rate with some practical experiences. The main goal is to emphasizethe importance of producing a stable chloramine residual entering the distribution system to minimize chloramine decay and system maintenance. Includes figures.