Using GA for the Economic Optimization of WDN Designs Based on Quantitative and Qualitative Criteria

The supply of water with a desirable quality and at required quantities by water distribution networks (WDNs) requires exorbitant costs over their effective life. Optimized network design is، therefore، not only a basic and most decisive step toward reducing costs but will also serve a means for considering other quantitative and qualitative criteria in the design process. In this study، a gravitational network with two reservoirs was investigated to determine the effects of the quantitative parameter of resilience index and the qualitative parameter of free chlorine residual on network design costs. The quantitative parameter used gurantees network efficiency at critical demand times through creating extra capacity while the qualitative one is meant to ensure adequate concentrations are maintained throughout the network. For this purpose، a Genetic Algorithm (GA) was written in the Matlab code and incorporated into the EPANET Toolkit to perform thorough WDN hydraulic and water quality analyses. Results showed that the proposed method was capable of creating a logical and consistent relationship between quantitative and qualitative parameters، on the one hand، and design objectives، on the other، although the WDN costs are only slightly increased. It was concluded that the method could be exploited as a new basis for selecting the final WDN optimal design.