Pressure and Leakage Management in Water Distribution Systems via Flow Modulation PRVs

Abstract

Globally, water demand is increasing while the recourses are diminishing therefore the leakage reduction in water distribution systems (WDSs) becomes an important objective for the water industry. The benefits of applying pressure control policy in WDS in order to reduce the leakage has been discussed in (Ulanicki et al. 2008). The pressure management via flow modulation has been applied and its benefits has been documented e.g. in (Yates and MacDonald 2007). Flow modulation PRVs can be operated either hydraulically (AbdelMeguid et al. 2009) or electronically to modulate the outlet pressure according to the demand level and required pressure at critical nodes. In this paper a genetic algorithm (GA) is used to calculate the coefficients of second order relationship between the flow and the optimal outlet pressure for a PRV. The method is implemented in Matlab linked to the EPAnet hydraulic simulator. The obtained curve can be subsequently implemented using a flow modulation controller (AbdelMeguid et al. 2009). The results of optimal PRV flow modulation via GA has been compared with the time schedule approach using a non-linear programming method described in (Ulanicki et al. 2008). The results of both techniques are very close to each other and resulted in almost the same amount of leakage reduction. The main advantage of the flow modulation in comparison to time schedules is that the modulation curve is calculated once and operates robustly over a wide range of demands. Although, the flow modulation is getting popular in the UK for single inlet district metering areas (DMAs), a special care must be taken for multi-inlet DMAs where interactions between inconsistent flow modulation curves may lead to hunting phenomena.