Application of Multiple-Part Method length of Line to Improve the Simulation of Chlorine Decay in Big Isfahan Water Conveyance Line

Chlorine is used as the most common disinfectant to prevent microbial growth in water networks. The concentration of chlorine in distribution systems or water conveyance lines is reduced due to two different types of bulk and wall decay. In this study EPANET software is applied to numerically simulate chlorine decay in the Isfahan water supply line from the Baba Sheikhali water treatment plant to Naein. Two methods are applied for simulation and the results are compared to the measurement. In the first method, chlorine simulation was performed taking into account the whole Isfahan water conveyance line as one section (integrated) and determining a bulk decay and wall decay coefficient for the entire conveyance line. In the second method, the line was divided into two sections (bisection) and decay coefficients of chlorine for each section was separately considered. To determine the bulk reaction rate, the bottle tests were performed at 6o and 18o Celsius corresponding to winter and summer. The results indicated that separating the line to two and applying independent coefficients and decay parameters to each part improves the results and the RMSE values are reduced from 0.09 to 0.03 in summer and from 0.064 to 0.025 in winter.  Therefore, dividing the line in two or more sections substantially improves the accuracy of the simulation of chlorine decay.