Modeling Chlorine Residuals in Drinking‐Water Distribution Systems

TLDR

A mass‑transfer‑based model is developed to predict chlorine decay in drinking‑water distribution networks. The model treats chlorine decay as first‑order reactions in bulk flow and at pipe walls, with wall reaction rates governed by mass transfer that depends on pipe geometry and flow regime, and is implemented in EPANET for dynamic simulations. The model explains higher chlorine decay in smaller pipes and at higher flow velocities, matches measurements where hydraulics are well characterized, and offers a useful tool for managing chlorine disinfection.

Abstract

A mass‐transfer‐based model is developed for predicting chlorine decay in drinking‐water distribution networks. The model considers first‐order reactions of chlorine to occur both in the bulk flow and at the pipe wall. The overall rate of the wall reaction is a function of the rate of mass transfer of chlorine to the wall and is therefore dependent on pipe geometry and flow regime. The model can thus explain field observations that show higher chlorine decay rates associated with smaller pipe sizes and higher flow velocities. It has been incorporated into a computer program called EPANET that can perform dynamic water‐quality simulations on complex pipe networks. The model is applied to chlorine measurements taken at nine locations over 53 h from a portion of the South Central Connecticut Regional Water Authority's service area. Good agreement with observed chlorine levels is obtained at locations where the hydraulics are well characterized. The model should prove to be a valuable tool for managing chlorine‐disinfection practices in drinking‐water distribution systems.