Published: 2006
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OBJECTIVES: The objectives of this project were to (1) document the effectiveness of free chlorine for the control of nitrifying bacteria, (2) evaluate how different distribution system pipe materials affect nitrifying biofilm consortia, and (3) determine how DBP concentrations change as a result of the switch from monochloramine to free chlorine. BACKGROUND: 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.