Optimal operation of intermittent water supply systems under water scarcity

Abstract

In South Asia, Latin America, and Africa, approximately 1.3 billion people intermittently receive water for domestic use through piped networks, known as intermittent water supply (IWS). IWS poses high operation costs and Non-Revenue Water (NRW) to water utilities, coping costs for water storage and treatment facilities to consumers, inequitable water supply, and health problems. Water scarcity is one of the main causes of water supply intermittency. This study presents a heuristic approach for sectorizing and optimum operation of IWS systems under water scarcity conditions. The methodology employs a two-step strategy: the first is a heuristic method for dividing the network into sectors based on connectivity, direct access to the source, and minimizing cut size between sectors. The second is the application of the evolutionary multiobjective optimization method, a non-dominated sorting genetic algorithm (NSGA-II), for the optimum operation of IWS systems considering three objectives: the operational cost, level of equity, and level of pressure among consumers. Design variables for the optimization problem include the status of bridge pipes between sectors as well as the triggers on/off for the tank levels. A benchmark network was used to demonstrate the effectiveness of the proposed methodology. The results of the application of optimization for the optimal operation of non-sectorized and sectorized networks highlight the potential of improving both equity and pressure uniformity of the IWS system. Sectorization and optimal operation of IWS systems appear to have significant effects on improving pressure uniformity in different parts of the sector, improving equity among consumers, and saving energy throughout the day.