Chloramines are widely used to maintain a disinfectant residual in water distribution systems, but can result in nitrification. This research documents the effectiveness of free chlorine for the control of nitrifying bacteria, evaluates the effect of pipe materials on nitrifying bacteria, and determines how DPBs change as a result of the switch to free chlorine.

Utilities that have difficulty maintaining free chlorine residuals in their distribution systems, or that are unable to attain the minimum DBP concentrations set by regulation, often switch to chloramines as secondary disinfectants. Unfortunately, chloraminated distribution systems are biologically unstable in that they may promote nitrifying bacteria growth. The prevention and control of nitrification is a concern for chloraminating utilities as it is identified with disinfectant loss and facilitation of heterotrophic biological growth. This study has shown that a periodic switch from a chloramine residual to a free chlorine residual may not be sufficient for long-term control of nitrification within a chloraminated distribution system. Given the higher levels of DBPs observed following a switch to free chlorine, utilities may be better served by careful maintenance of their ammonia feed such that nitrification episodes are minimized.

In response to many U.S. water utilities that are considering changing disinfectants from chlorine to alternative disinfectants, this research has been undertaken to gain knowledge of long-term effects.

This brand new manual was written because of the increased use of chloramine as a residual disinfectant in drinking water distribution systems and the ubiquitous presence of nitrifying bacteria in the environment. Chapters cover background information on the occurrence and microbiology of nitrification in various water environments and provide current practical approaches to nitrification prevention and response. This manual provides a compendium of the current state-of-the-art knowledge, however with quickly developing new advances in nitrification, more writings will be forthcoming. Each chapter can be read independently.

The goal of this project was to understand the formation and decay of selected DBPs in full-scale distribution systems focusing on the four THMs and the nine HAAs, as well as individual THM and HAA species. Because of its critical nature, NDMA was also included. The project objectives were: evaluate the critical factors that affect THM and HAA behavior in distribution systems; determine the fate and behavior of NDMA in distribution systems; evaluate the effect of pipe material and diameter on the fate of DBPs in distribution systems; examine the effect of storage reservoirs / tanks and booster chlorination stations on THM, HAA and NDMA concentrations; evaluate the changes in DBP concentrations and speciation when a system seasonally switches from chloramines to free chlorine to limit potential nitrification episodes....

Assesses the impact of dynamic water quality conditions in the distribution system on the inactivation of microorganisms in bulk water. Addresses questions about the usefulness of maintaining a secondary residual and the target level to be maintained. Bridges research related to distribution system water quality with that of microbial inactivation.