Controlling Chloramine Decay and Nitrification in Distribution Systems

Project: Research project

Project Details

Description

Controlling Chloramine Decay and Nitrification in Distribution Systems Controlling Chloramine Decay and Nitrification in Distribution Systems Research Objective. The objective of this project is to better identify and quantify chloramine decay mechanisms and their relationship to supporting nitrification in distribution systems. This objective will be obtained using the CDWQ distribution system water quality model, field data collected from participating utilities, and data gathered from laboratory pilot studies. Technical Approach. Monochloramine is becoming widely used as drinking-water disinfectant. The primary goal of disinfection is to maintain a residual that effectively suppresses microbial growth, including growth that leads to nitrification, to the far ends of the distribution system. However, chloramines participate in numerous reactions that diminish residual concentrations during distribution. Chloramine decay releases ammonia, supporting nitrification. A reaction model for free chlorine and chloramines was developed as part of a distribution-system water-quality model, called the Comprehensive Disinfection and Water Quality (CDWQ) model (Woolschlager, 2000). CDWQ was calibrated using data from a year-long distribution system sampling program conducted at United Water of New Jersey (Woolschlager et al., 1999; Woolschlager 2000; \Yoolschlager et aI., 2001). Figure 1 shows the disinfectant chemistry sub-model contained in CDWQ. As shown in Figure 1, this sub-model contains six major groups of reactions: equilibrium reactions (EI, E2, and E3); chloramine autocatalyticdecay reactions (ADI to ADS); and a surface-catalyzed reaction (SCI); corrosion reactions (Crl to Cr3); oxidation reactions (OxI - OxS); and biologically catalyzed reactions (BI and B2). These reactions accurately capture chloramine decay chemistry and the resulting release of ammonia that supports nitrification in the distribution system. Beyond the disinfectant subroutine, CDWQ is a comprehensive water quality model that represents the major chemical, physical, and biological processes that affect drinking water quality within distribution systems.
StatusFinished
Effective start/end date1/15/093/2/10

Funding

  • Awwa Research Foundation: $74,984.00

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