Joaquim Sousa

Estimation of the benefits yielded by pressure management in water distribution systems

The occurrence of water losses in Water Distribution Systems is inevitable. Knowing that most of the real losses take place in distribution mains and in service connections, the methodology proposed in this paper is based on several leakage-assessment approaches from literature and on water distribution network modeling. This allows assessment of the benefits that can be achieved by pressure management in Water Distribution Systems, particularly in terms of water production reduction. Moreover, this approach can be useful for cost benefit analysis to help establish the level after which there is no more economic interest in reducing water losses (Economic Level of Leakage). Finally, the results from hypothetical case studies are presented and discussed, assuming the installation of Pressure Reducing Valves at District Metered Areas entry points.

Robust Design of Water Distribution Networks for a Proactive Risk Management

In the last three decades the optimal design of water distribution systems problem has been studied by a great many researchers, and this has resulted in the development of a large number of models and the application of optimization techniques. The design of these infrastructures is based on future predefined and perfectly known working conditions for the water distribution networks, a premise that may direct the optimization process to solutions which, although optimal for the imposed scenario, may perform badly if reality turns out to be significantly different. In fact the working conditions can be disrupted by accidents such as broken pipes or reservoirs, technical failures, change in demand, etc. In the context of a proactive attitude toward risk, it is important to consider these aspects at the design phase. This paper presents a robust optimization-based approach for designing a water distribution network aimed at obtaining solutions that can cope with the uncertainty of the network’s working cond...

Identification of the optimal entry points at District Metered Areas and implementation of pressure management

Nowadays, the implementation of pressure management in District Metered Areas (DMAs) is considered one of the most effective tools for leakage control, particularly in large networks and in systems with deteriorated infrastructures and with high pressure. The goal of the methodology proposed in this paper is to identify the optimal entry points at DMAs, determine the network needs in terms of reinforcement/replacement, and fix both the location and settings of different types of Pressure Reduction Valves (PRVs) for leakage control. This methodology is based on an optimisation model, which is solved by a Simulated Annealing algorithm, and the solutions obtained always fulfil the minimum pressure requirements for the network. The objective function comprises the total cost of the DMAs implementation and the economic benefits that can be achieved by pressure management. Finally, the results for two case studies are presented and discussed.

Decision support system to divide a large network into suitable District Metered Areas

This paper presents a new approach to divide large Water Distribution Networks (WDN) into suitable District Metered Areas (DMAs). It uses a hydraulic simulator and two operational models to identify the optimal number of DMAs, their entry points and boundary valves, and the network reinforcement/replacement needs throughout the project plan. The first model divides the WDN into suitable DMAs based on graph theory concepts and some user-defined criteria. The second model uses a simulated annealing algorithm to identify the optimal number and location of entry points and boundary valves, and the pipes reinforcement/replacement, necessary to meet the velocity and pressure requirements. The objective function is the difference between the economic benefits in terms of water loss reduction (arising from the average pressure reduction) and the cost of implementing the DMAs. To illustrate the proposed methodology, the results from a hypothetical case study are presented and discussed.

District Metered Areas Design Under Different Decision Makers’ Options: Cost Analysis

Water loss is a big challenge for water supply companies worldwide, and the Water Network Partitioning (WNP) is an excellent tool for water loss management–particularly in the current difficult economic and financial conditions. WNP is a recent research line and consists in dividing the water distribution network into smaller zones called District Metered Areas (DMAs) with one (or more, in exceptional cases) supply point, to reduce the network complexity and/or allow pressure management. Since there are several possible future scenarios, such as the water demand and/or the infrastructure degradation forecasts, which may have different impacts on the hydraulic behaviour, in this paper a computational application, based on an optimization model, is proposed to achieve a compromise between robustness required for the DMAs design (using a baseline scenario) and different decision makers’ options (using other scenarios with a lower “probability” of occurrence), to reduce the total cost. The objective function reflects the minimization of the squared deviations between the total cost of the DMAs design and the minimum cost for each scenario forecasted for the project plan, multiplied by the weight or “probability” of occurrence for each of the scenarios. The performance of the computational application is illustrated with a case study, and the results are encouraging.

Entropy-based Reliable Design Of WaterDistribution Networks

Water distribution networks are crucial for the wellbeing of communities, but their construction involves huge investment. The need to optimize investments has resulted in the development of methodologies to determine the minimum cost design of these infrastructures. However, as cost minimization tends to eliminate any redundancy in the networks, this kind of approach leads to less reliable solutions. From the reliability point of view, an ideal water distribution network should ensure reasonable service levels even when a failure occurs. But such a scenario, if possible, would certainly imply an intolerable level of investment. The following question therefore arises: by how much is it reasonable to increase investment to reduce the risk of failure? Trying to help decision makers answer this question, this work offers a tool to solve the reliable design of water distribution networks problem. It is based on an optimization model comprising two antagonistic objectives: minimizing the cost and maximizing reliability (here indirectly evaluated by the network entropy). The multiobjective problem is solved by the constraint method. The result is a set of cost minimization problems, each constrained by a different minimum level of entropy, which are solved by the Simulated Annealing method. This approach leads to a set of solutions known as Pareto solutions. Each of these solutions represents a different level of compromise between cost and reliability, and they can be very helpful for decision makers.

Optimal Management of Water Distribution Networks with Simulated Annealing: The C-Town Problem

AbstractSustainability is a major issue for water companies, who have to provide high quality services at achievable costs. In this context, water loss control and energy efficiency are two great challenges water companies have to face. Water loss represents both higher service cost (real losses) and loss of revenue (apparent losses), while the energy bill from treatment plants and pumping stations represents a significant part of the service cost. The Battle of Background Leakage Assessment for Water Networks (BBLAWN) was a competition dedicated to this subject: water distribution network (WDN) optimal management. Teams/individuals from academia, consulting firms, and utilities were invited to propose methodologies for solving the C-Town WDN problem: minimize operational and capital costs and background leakages. This paper presents one of the methodologies proposed at BBLAWN. The methodology proposed here to solve the C-Town WDN problem comprises two optimization models: a least-cost design model to ide...

Hidráulica Urbana: Sistemas de abastecimento de água e de drenagem de águas residuais

Res_por:Este texto aborda temas relacionados com o dimensionamento e a analise do comportamento de infraestruturas de Hidraulica Urbana, concretamente, os sistemas de abastecimento de agua e a drenagem de aguas residuais e pluviais. Apos uma breve introducao geral ao tema (Capitulo I), apresentam-se algumas metodologias frequentemente utilizadas na avaliacao das necessidades gerais de Agua dos nucleos urbanos, bem como dos caudais efluentes desses nucleos (Capitulo II), ao que se segue o estudo de sistemas de aducao e das caracteristicas gerais de condutas e acessorios (Capitulo III). O armazenamento de agua em pequenos reservatorios, isto e, capazes de suprirem as necessidades por periodos nao muito longos (dia), e abordado no Capitulo IV. No Capitulo V, dedicado as redes de distribuicao de agua, apresentam-se os modelos conceptuais e matematicos de equilibrios hidraulicos em regime permanente, bem como os metodos numericos necessarios a resolucao das equacoes nao lineares resultantes. O texto prossegue com o estudo dos transitorios hidraulicos em sistemas sob pressao (Capitulo VI), onde se apresenta o metodo das caracteristicas e as condicoes de fronteira mais comuns, e generaliza com o estudo da simulacao dinâmica do comportamento hidraulico de sistemas sob pressao (Capitulo VII). No capitulo seguinte (Capitulo VIII) e brevemente abordada a modelacao da qualidade da agua em sistemas pressurizados. Nos capitulos seguintes sao analisadas questoes relacionadas com a drenagem de aguas residuais (Capitulo IX) e pluviais (Capitulo X), e por ultimo refere-se de forma sucinta questoes relacionadas com a reabilitacao de canalizacoes (Capitulo XI). Em complemento ao texto compilaram-se, nos anexos 1 e 2, respetivamente, as leis de resistencia dos escoamentos e aspetos relacionados com o comportamento de bombas centrifugas.

Optimal integrated operation of pipeline systems and water treatment plants

Water supply systems usually include a number of components (treatment plants, pipelines, pumping stations and distribution reservoirs), each of which performs a specific function. The interconnection between components requires the integrated operation of the systems. The operation of these systems is quite expensive because the energy consumption of some components is rather high. Both reasons (interconnection between components and high energy consumption) justify the development of tools to help their integrated operation while rninizing costs. This paper presents a mixed-integer optimization model aimed at minimizing systems operation costs, over a 24-hour period. The model includes constraints related to the physical behaviour of the systems, and takes the variable electricity tariff into account. The model is solved using two different methods: “Branch-and-Bound” (an exact method) and “Simulated Amealing” (a random search method), In order to compare the efficiency and effectiveness of the two methods, the model is applied to a hypothetical example. Even though the model has not yet been tested in practice, authors are convinced that the use of this type of tool could be of great help in the operation of water distribution systems, allowing significant savings in energy costs.

Optimal Design Of Water Distribution Networks:A Computer-aided Decision Support Tool

A comprehensive review of the literature reveals that there is, today, an extensive body of work referring to the problem of finding the least cost design of water distribution networks. However, unfortunately, these sophisticated models are not proposed with user-friendly interfaces to facilitate communication with the different practitioners involved in solving this kind of problem. Therefore, suitable packages are needed to overcome the lack of acceptance of the optimization models existing nowadays. In this paper, we describe a program to provide a computer-aided decision support tool for the design of water distribution networks. Data input is userfriendly, done by means of a graphical input of the network. This data acquisition module is linked to an optimization module, whose solutions are also presented graphically. The optimization module is based on a simulated annealing algorithm that has been tested for different networks. The results obtained so far confirm the capacity of this method to handle the combinatorial nature of the problems to be solved and show an improvement in both optimum quality and computational effort in comparison with published results. Transactions on Ecology and the Environment vol 19,