Optimal Operation of Water Distribution Networks under Water Shortage Considering Water Quality

Abstract

Water shortages are caused by hydrological droughts and by the disruption of the operation of water distribution networks (WDNs). The water pressure and residual chlorine concentration are examples of quantitative and qualitative indexes, respectively, of a WDN’s performance. This work considers quality and quantity variables simultaneously in the operation of WDNs under water shortages. An optimization model is developed to find the optimum water allocation schedule in WDNs. The objectives of the optimization model are maximizing the number of node-times in which the chlorine concentration is in the allowable range, and maximizing the number of supply nodes under desirable pressure. These objectives satisfy the principle of justice in water distribution under water shortage. The optimization model was solved for a real WDN under different scenarios using the honey-bee mating optimization (HBMO) algorithm linked to a hydraulic simulator. The performance of the developed model was compared to an operation rule based on standard operation policy (SOP) that allocates water among consumers based on constant priority of water supply. The results show that water-shortage operation affects water quality and decreases the chlorine concentration below the allowable minimum in the network, and that applying a water allocation schedule obtained with the developed optimization model minimizes this effect so that this allocation schedule maintains residual chlorine concentration mostly within the allowable range throughout the network. The optimized operation of the WDN satisfies consumer demands fairly under desired pressure while reservoir and hydraulic constraints are satisfied.