Improved fuzzy chance-constrained optimization of booster strategy for water distribution system under uncertainty

To sustain water quality in water distribution system (WDS), disinfectant generally chlorine is boosted to water distribution system. However, the concentration of chlorine should be limited to acceptable scope. The upper bound of the scope is set for preventing the occurrence of disinfectant byproduct, which is harmful to human health. The lower bound of the scope is set for controlling the growth of microorganism as well as reducing the injection mass. As such, the optimization model was applied to solve the water quality issue in WDS. However, in WDS, chlorine decays and varies with time and space, affected by pipe material, temperature, pH value, and chlorine injection, etc. Therefore, in this paper, an improved fuzzy chance constrained optimization model was proposed to optimize the chlorine injection and location to maintain chlorine in WDS distributed uniformly. The proposed model was applied to two WDSs to analyze the effect of reliability level and preference parameter on the chlorine injection and location. The results indicated that the injection mass increases with the increase of preference parameter. The results also indicated that more booster stations can lower the injection mass, and two booster stations are suitable for WDS in Case 2. The method proposed can be applied to decide how and where to inject chlorine to WDS under uncertainty, and can help manager to determine whether optimistic or pessimistic attitude should be taken under various reliability levels.