Wall Decay Coefficient of Combined Chlorine in a Drinking Water Distribution System

Using water quality models to predict disinfectant concentrations in water distribution systems requires a knowledge of the wall decay coefficient. In this study, field water sampling was conducted in conjunction with a SynerGEE Water hydraulic model for an area of the water distribution system of the City of Edmonton to calibrate a wall decay coefficient for combined chlorine. Using the least squares method, a unique wall decay coefficient, 0.0295 m/d, was obtained. Using the same method it was found that the wall decay coefficient was 0.0455 m/d for a sub-section of the studied area with predominantly cast iron pipes, and 0.0160 m/d for another sub-section where the pipes had been extensively renewed. By identifying wall decay coefficients for individual areas using this method, it is feasible to turn SynerGEE Water hydraulic model into a working model to predict water quality for the City of Edmonton.