Ramon Pérez

Optimal control of a water distribution network in a supervisory control system

This paper deals with the use of optimal control techniques in water distribution networks. An optimal control tool, developed in the context of a European research project is described and the application to the city of Sintra (Portugal) is presented. ( 2000 Elsevier Science Ltd. All rights reserved.

Review of the dielectric properties of nanofiltration membranes and verification of the single oriented layer approximation.

The structuring of water at soft solid surfaces remains an area of great interest to colloid science as a whole and has many applications in relation to colloid stability, foams, and wetting films as well as being central to membrane separations. Quantitatively calculating the structural components of thin layers of water and the interaction forces of hydrated molecules with the surface of pores through a layer of water having modified structure is one of the most important challenges in the physics of surface phenomenon. In this paper these effects are reviewed and discussed in relation to the confines of a capillary pore. Membrane nanofiltration is extremely complex and is dependent on the micro-hydrodynamics and interfacial events occurring at the membrane surface and within the membrane nanopores. There is significant debate as to the exact nature of these complex phenomena and rejection is typically attributed to a combination of steric and electrical effects. The electrical effects are less well understood and in particular the contribution of dielectric exclusion. A review of the two competing descriptions of dielectric exclusion is presented along with the theories currently used in modelling this phenomena. A series of rejection experiments of 0.01 M salt solutions at the membrane isoelectric point has been performed for the NF270 and NF99HF membranes. The dielectric constants inside the nanopore are calculated and these values were consistent for three of the salts studied, indicating that a simplistic model based on Born theory is accurate enough for engineering calculations and that ion solvation is most likely to be the more appropriate dielectric exclusion mechanism for true nanofiltration membranes.

Leak Localization in Water Networks: A Model-Based Methodology Using Pressure Sensors Applied to a Real Network in Barcelona [Applications of Control]

The efficient distribution of water is a subject of major concern for water utilities and authorities [1]. While some leaks in water distribution networks (WDNs) are unavoidable, one of the main challenges in improving the efficiency of drinking water networks is to minimize leaks. Leaks can cause significant economic losses in fluid transportation and extra costs for the final consumer due to the waste of energy and chemicals in water treatment plants. Leaks may also damage infrastructure and cause third-party damage and health risks. In many WDNs, losses due to leakage are estimated to account up to 30% of the total amount of extracted water [2]; a very important issue in a world struggling to satisfy water demands of a growing population.

Sensitivity Analysis for Sampling Design and Demand Calibration in Water Distribution Networks Using the Singular Value Decomposition

AbstractResearch in water distribution networks during recent decades has often focused on calibration. There is no unique solution for this problem as the methodologies are developed depending on which parameters have to be calibrated and the final use of the model. This work presents a demand calibration methodology that identifies a set of patterns that minimize the error in predicted measurements. The singular value decomposition (SVD) of the sensitivity matrix is a powerful tool for solving the optimization problem. Additionally, in this work, the deep understanding of the SVD allows the selection of an alternative to the classic patterns. Each individual demand is defined as a combination of geographically distributed patterns. The membership of each demand to every pattern is produced naturally through the analysis of the SVD of the sensitivity matrix. Three types of memberships are considered: binary, positive, and free. The SVD analysis is also used to define the location of sensors for the calib...

A decision support system for on-line leakage localization

This paper describes a model-driven decision-support system (software tool) implementing a model-based methodology for on-line leakage detection and localization which is useful for a large class of water distribution networks. Since these methods present a certain degree of complexity which limits their use to experts, the proposed software tool focuses on the integration of a method emphasizing its use by water network managers as a decision support system. The proposed software tool integrates a model-based leakage localization methodology based on the use of on-line telemetry information, as well as a water network calibrated hydraulic model. The application of the resulting decision support software tool in a district metered area (DMA) of the Barcelona distribution network is provided and discussed. The obtained results show that the leakage detection and localization may be performed efficiently reducing the required time.

Leakage isolation using pressure sensitivity analysis in water distribution networks: Application to the Barcelona case study

Abstract Leaks are present to some extent in all water-distribution systems. This paper proposes a leakage localisation method based on the pressure measurements and pressure sensitivity analysis of nodes in a network. The sensitivity analysis using analytical tools is not a trivial job in a real network because the huge non-explicit non-linear systems of equation that describe its dynamics. Simulations of the network in presence and absence of leakage may provide an approximation of this sensitivity. This matrix is binarised using a threshold independent of the node. The binary matrix is assumed as a signature matrix for leakages. However, there is a trade-off between the resolution of the leakage isolation procedure and the number of available pressure sensors. In order to maximise the isolability with a reasonable number of sensors, an optimal sensor placement methodology, based on genetic algorithms, is also proposed. This methodology has been developed for Barcelona Network using Piccolo simulator. The sensor placement and the leakage detection and localization methodologies are applied to district management areas (DMA).

Leakage isolation in water distribution networks: A comparative study of two methodologies on a real case study

Leakages are present to some extent in all water-distribution systems. This paper compares two model based methodologies for leakage isolation in water distribution networks. Both are based on the pressure measurements and pressure sensitivity analysis of nodes in a network. Simulations of the network in presence and absence of leakage may provide an approximation of this sensitivity. The difference between both methodologies relies on how the information of the sensitivity matrix is handled. In the first approach, this information is binarised using a threshold. The resultant binary matrix is assumed as a signature matrix for leakages. One of the main issues in the binarisation process is the threshold selection. Even with the best selection of a threshold, binarisation implies loss of information. The second method is based on the use of the sensitivity matrix without any transformation in order to avoid loss of information. Results obtained on a real network (a District Metered Area (DMA) of Barcelona water distribution network) using both methods are compared. Finally, some discussions and conclusions about the limitations of both techniques and future work are presented.

Leakage localization in water networks using fuzzy logic

This paper presents a methodology for leakage localization using FIR (Fuzzy Inductive Reasoning). A real water network situated in Barcelona has been subdivided in zones which could contain a leakage. Two sensors measure pressures on two separated points of the network. A faulty fuzzy model for each zone and sensor is generated. Test data have been used for classification of leakages in order to evaluate how this methodology helps in leakage localization. Results are compared with another isolation methodology. All the work has been done using simulations carried out by EPANET connected with Matlab. FIR applications used are programmed in Matlab too.

FIRST RESULTS OF PREDICTIVE CONTROL APPLICATION ON WATER SUPPLY AND DISTRIBUTION IN SANTIAGO-CHILE

Abstract This paper deals with the use of predictive optimal control techniques for flow management in a large water system including reservoirs, open channels for water transport, water treatment plants, pressurized water pipe networks, flow/pressure control elements and a telemetry/telecontrol system. Predictive control is used to generate flow control strategies from the sources to the consumer areas to meet future demands with appropriate pressure levels, optimizing operational goals such as network safety volumes and flow control stability.

Abnormal quality detection and isolation in water distribution networks using simulation models

This paper proposes a model based fault localisation method to deal with abnormal quality levels based on the chlorine measurements and chlorine sensitivity analysis in a water distribution network. A fault isolation algorithm which correlates on line the residuals, generated by comparing the available chlorine measurements with their estimation using a model, with the fault sensitivity matrix is used. The proposed methodology has been applied to a District Metered Area (DMA) in the Barcelona network.