Research On Leakage Control Of Water Distribution System By Pressure Reducing Valves

Reducing and controlling water loss is becoming very important issue in this age ofrapidly growing demand and relative abundance to one of relative scarcity of the waterresources. Water loss depends on the physical characteristics of the pipe network,operating factors and parameters, and among them the network pressure is an importantfactor, which has been a common practice that reducing operating pressures can lead tothe reduction of leakage in water distribution networks. Based on this, this dissertationfocuses on optimal control of pressure reducing valves in water distribution networks inorder to save more water and improve economic benefits of water supply companies.Pressure test of district metered area is the first step to carry out pressuremanagement, which can provide significant theoretical basis to determine whether thearea is suitable for pressure management. The dissertation makes a detailed discussionon the preparation and operation steps of pressure test and takes pressure test on apractical example network to find out the scope of reducing pressure and possibleeconomical benefits through pressure management. According to the result of pressuretest, it can be seen that leakage of that water distribution network is highly related topressure, so it is important to carry out pressure management to control leakage.After pressure test, it is necessary to estimate appropriate number and location ofpressure reducing valves. Firstly, this dissertation uses minimum night flow to calculateleakage coefficient of each node in water distribution network and establish anenhanced hydraulic model, which incorporate pressure dependent leakage terms. Then,a decision support model for optimal control of pressure reducing valves is formulatedas a two criteria optimization problem and is solved with NSGA-II algorithm. Inparticular, the first criterion is represented by the minimization of total leakage, and thesecond is the minimization of capital of pressure reducing valves. The decision variableis the scheduling scheme and settings of pressure reducing valves, when maintaining therequired pressure at critical node. The following example network illustrates thecalculation procedures of the decision support model.Optimal number and location of pressure reducing valves can be obtained throughthe decision support model, but it is still important to determine outlet pressures afterinstallation of them to form integrated scheme of pressure management. The dissertationproposes optimal field controlling methods of pressure reducing valves based on flowand time, and uses Particle Swarm Optimization and statistical methods to calculaterespectively. A study is made on the following example network and shows that leakagereduces significantly after the implementation of pressure management strategy.Finally, the optimal location and control of pressure reducing valves for a realsecondary partition water distribution network is obtained, applying integrated scheme of pressure management. The result shows that pressure management can effectivelyreduce the leakage and burst frequency, and improve safety of supplying water in thiswater distribution network at the same time.