Galdiero, Enzo (2015) Multi-objective design of district metered areas in water distribution networks. [Tesi di dottorato]

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Abstract

The present thesis addresses the sectorization of Water Distribution Networks (WDNs), a technique based on the use of shut-off valves for the establishment of controlled sub-zones, usually called District Metered Areas (DMAs). The DMA approach is widely recognized as one of the most successful and cost-effective methods for the optimization of the WDNs. Among the many benefits achievable through the sectorization, the most interesting effects are the increased system control and the contribution offered to the mitigation of the water losses. The establishment of DMAs can be carried out under several perspectives and with different goals. Moreover, in real cases the achievement of the optimal design of DMAs may be very challenging because of the intrinsic complexity of the WDNs. Therefore, the development of a methodology able to provide support to decision-making is required. In recent years, an increasing number of researches have addressed this problem, and different optimization approaches can be found in literature. However, the techniques developed so far still suffer from some limitations and drawbacks, which mainly consist in the lack of engineering principles among the design criteria and the dependence on the size of the problem. In this thesis, a comprehensive methodology for the optimal sectorization of WDNs is presented and discussed. The proposed approach consists of a two-objectives optimization problem subjected to a number of constraints related to the topology of the WDN, financial issues and the network hydraulics. One of the most innovative feature of this method is the particular emphasis placed on the minimization of the water leakages, that is explicitly included in the objectives. As highlighted in some studies, the establishment of DMAs is crucial for the development of optimization approaches based on pressure control (e.g. use of Pressure Reducing Valves, PRVs). However, sectorization itself can be considered as a pressure management technique. In fact, the closure of a number of network pipes may cause a significant increase of the head-losses throughout the WDN, with the consequent decrease of the pressures and of the water leakages. A Multi-Objective Evolutionary Algorithm (MOEA) is combined with tools from graph theory for the solution of the problem. The procedure is completely implemented in Matlab environment, and it allows the automatic generation of feasible and optimal designs of DMAs just basing on the network model. The validation of the methodology and the calibration of the parameters are performed through the application to a well-known example from literature. Then, a real test case is analyzed, namely the WDN of Pianura, a neighbourhood in the city of Naples, Italy. Low cost as compared to the budget and a good saving in leakage are obtained.

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