Conventional pressure reducing valves (PRVs) are often used in water distribution systems for pressure control and water loss reduction. Nevertheless, depending on the conditions in the network, advanced pressure management approaches might be more suitable. In this study, the potential water loss reduction for an intelligent system that combines PRVs and pumps as turbines (PATs) in a pilot study in Germany was estimated. The aim of the proposed system is to recover the pressure energy in the supply network by transforming it into electricity and, at the same time, contribute to the reduction of water losses and material stress. In order to evaluate the pressure situation and predict the water savings of the different pressure management strategies in the studied supply area, hydraulic modelling was used. Using the calibrated model, the optimal outlet pressure for the installed PRV and for the intelligent pressure control system was calculated, taking into account the pressure at the critical point as a boundary condition. Furthermore, the pressure-dependant leakage flow was simulated using the emitter coefficient feature in EPANET. Here, a pressure exponent of 1.5 was used, assuming uniform background leakage along the distribution system. For the analysed network, 28.5% and 45% water savings are expected for the fixed and for the advanced pressure management strategy, respectively. The predicted water savings and the leakage assumptions are to be verified either on field or experimentally. This study concludes that hydraulic modelling is essential for assessing water supply networks, as well as for optimizing current pressure management strategies and predicting its benefits.

Pressure reducing valves (PRVs) are used in water distribution networks (WDNs) for pressure control and water loss reduction. In this study, a system composed of a PRV and a pump as turbine (PAT) in combination with intelligent pressure management is proposed and its performance is analysed experimentally. For this, data analysis using hydraulic modelling and extensive experimentation for a case study in Germany was performed. During the laboratory tests, the pressure at the critical point of the system could be successfully maintained at the selected value at variable discharges during a characteristic day, as a result of the advanced pressure modulation. Additionally, up to 2.3 kW of electrical energy were recovered, when the applied PAT was operating under full load, with a maximum total net system efficiency of 40%. Furthermore, the proposed pressure management was found to increase the water savings by up to 16% compared to conventional PRVs. This study concludes that the PAT-PRV-system may be suitable in WDNs with high differences in altitude, high operational pressures and high demand variability. For its application, the benefits and the investment costs, as well as the seasonal flow and pressure variations in the WDN should be analysed in detail.

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Proj. ECN l l a. M o d i f i c a t i o n York 3. O r i g i n a t o r ' s N f m , Organization, WSIY.

Survey f o r New Liquid Observation Well and Liquid Observation Well Material 2Some of the FG LOUs have been replaced with carbon steel LOUS.