STUDY ON RESIDUAL CHLORINE CONTROL OF WATER DISTRIBUTION SYSTEMS WITH MULTIPLE WATER SOURCES

A best chlorine injection schedule for each source and booster station in a distribution system is studied and a multiple object optimal operation model of water distribution system(WDS) considering residual chlorine is also presented. The optimal scheduling of water distribution system is composed of two parts, the hydraulic and the water quality optimal control, and water quality optimal control is based on the hydraulic optimal control. As an important component of water quality optimal control, the residual chlorine control is selected as one of the objective functions of the optimal scheduling of water distribution system. A new multiple objects optimal operation model of WDSs is developed. The objective functions include minimum of residual chlorine and minimum costs of WDSs operation. The decision variables include the demand, pressure and residual chlorine at each water source, nodal demand, nodal pressure, and nodal residual chlorine. The hydraulic and the water quality model are solved by EPANET. The multiple objects optimal operation model of WDS is solved by the non-dominated sorting genetic algorithm (NSGA-II). Adaptive penalty functions are also applied in the process of model solved As a case study, the multiple objectives optimal operation model is applied in a large scale WDS. The WDS ’s total demand is about 1,320,000 m 3 /d, and is composed of 9 water plants, 32 water sources, and 468 wells. The result shows that the optimization of chlorine of each water source makes the distribution of nodal chlorine more reasonable and the concentration of nodal residual chlorine was reduced.