The presented thesis investigates the identification of burst locations in water distribution systems (WDS) by analysis of field and simulation experimental data. This required the development of a new hybrid method of burst detection and sizing, and also a burst location identification algorithm. Generally, existing practice relies on a combination of some simple procedure and experience of the involved staff and cannot be easily automated. The practical methods are based on direct manifestation of burst on the surface or on systematically surveying suspected areas e.g. by using listening sticks, such methods are very time consuming. The proposed burst location algorithm is based on comparing data by means of statistical analysis of field data with results of water network simulation. An extended network hydraulic simulator is used to model pressure dependent leakage terms. The presence of a burst changes the flow pattern and also pressure at network nodes which may be used to estimate the burst size and its location. The influence of such random factors as demand flows and background leakage on the process of burst detection is also considered. The field data is from a generalised fixed area and variable area (FAVOR) test where inlet pressure is being stepped up and down and the following variables are measured: inlet flow, inlet pressure (head) and pressure at a number of selected sensitive nodes. The method has three stages and uses two different models, one is inlet flow model (IFM) to represent the total inlet flow and another is the extended hydraulic model to simulate different burst locations. Initially the presence of a potential burst is investigated. If this is confirmed precise values of the demand, background leakage flow and burst flow in IFM are subsequently estimated. They are used to identify the burst site at the third stage of the method. The method can be easily adapted for practical use. It requires data from experiments carried out at night between 1am and 5am and involves placing typically about 20 temporary loggers to collect the measurements during this period. It also requires the availability of a hydraulic model which normally is in the possession of a water company. The program has been implemented in the Matlab package and is easy to use. The current methodology is tuned to identify a single burst but can be generalised to identify locations of multiple bursts.

Municipal water distribution systems are operated and maintained by utilities whose first priority is the safe and reliable provision of drinking water to consumers. The cost to move and treat water through distribution networks is significant and can account for up to 80% of a utility’s energy costs. As these networks age, operating and maintenance costs continue to increase due to higher incidences of leaks and breaks and increased pipe friction leading to higher energy use. Many utilities are considering water conservation as a strategy to reducing their energy consumption by reducing the amount of water being pumped and treated in their jurisdictions. This work studies the pumping energy response of a distribution system when water conservation strategies are implemented in small geographic areas in the network. A water conservation plan is tailored to each defined area by specifying which conservation measures are feasible to implement, desired by the customer, and are attractive to the utility based on a potential return on investment in the form of reduced electricity bills to pump and treat water. Energy intensity and energy elasticity indicators are developed to assess the mechanical energy used in a network to distribute water to end-users. A case study for the City of Kingston water distribution system is presented. The distribution system studied indicated that when water conservation strategies produced marginal water savings, the energy response was inelastic to changes in water demand. The amount of energy required to move one cubic metre of water through the network increased with higher water savings because the percent savings of water was higher than the percent savings of pumping energy. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-05-31 14:20:18.363

Water utilities are facing pressure to continue to provide high-quality potable water in an increasingly energy constrained world; managing the ageing infrastructure that exists in many countries is a challenge in and of itself, but recently this has been coupled with political and public attention to the environmental impacts of the distribution system. Utility managers need to take a holistic approach to decision-making in order to determine all of the impacts of their plans. The intention of this thesis is to present a set of considerations for utility planners and managers to provide clarity to the trade-offs associated with any pipe replacement decision. This research has examined the energy relationships between operational energy reduction and the embodied energy tied to replacing deteriorated pipes in water distribution networks. These relationships were investigated through the development and application of a life-cycle energy analysis (LCEA) for three different pipe replacement schedules developed with the intent to reduce leakage in the system. The results showed that the embodied energy for pipe replacement is significant even when compared against the large amount of energy required to operate a large-scale water utility. The annual operational energy savings of between 8.9 and 9.6 million kWh achieved by 2070 through pipe replacement comes at a cost; 0.88-2.05 million kWh/mile for replacement with ductile iron pipes with diameters of 6” to 16” respectively. This imbalance resulted in a maximum energy payback period of 17.6 years for the most aggressive replacement plan in the first decade. Some of the assumptions that were used to complete the LCEA were investigated through a sensitivity analysis; specific factors that were numerically queried in this chapter include the break rate forecasting method, pumping efficiency, the leakage duration and the flow rate per leakage event. Accurate accounting of energy requirements for pipe replacement will become even more important as energy and financial constraints continue to increase for most water utilities, this thesis provides guidance on some of the complex relationships that need to be considered. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-08-21 16:51:18.963

The objective of this research project is to develop new software tools capable of operational optimisation of existing, large-scale water distribution networks. Since pumping operations represent the main operating cost of any water supply scheme, the optimisation problem is equivalent to providing a new sequence for pumping operations that makes better use of the different electricity tariff structures available to the operators of distribution systems. The minimisation of pumping costs can be achieved by using an optimal schedule that will allow best use of gravitational flows, and restriction of pumping to low-cost power periods as far as possible. A secondary objective of the operational optimisation is to maintain the desired level of disinfectant chlorine at the point of delivery to consumers. There is a steady loss of chlorine with residence time in the system. If the level drops too low there is a risk of bacterial activity. Re-dosage points are sometimes provided in the network. Conversely, too high a level produces an unacceptable odour. The combinatation of dynamic elements (reservoir volumes and chlorine concentration responses) and discrete elements (pump stati and valve positions) makes this a challenging Model Predictive Control (MPC) and constrained optimisation problem, which was solved using MINLP (Mixed Integer Non-linear Programming). The MINLP algorithm was selected for its ability to handle a large number of integer choices (valves open or shut / pumps on or off in this particular case). A model is defined on the basis of a standard element, viz. a vessel containing a variable volume, capable of receiving multiple inputs and delivering just two outputs. The physical properties of an element can be defined in such a way as to allow representation of any item in the actual network: pipes (including junctions and splits), reservoirs, and of course, valves or pumps. The overall network is defined by the inter-linking of a number of standard elements. Once the network has been created within the model, the model predictive control algorithm minimises a penalty function on each time-step, over a defined time horizon from the present, with all variables also obeying defined constraints in this horizon. This constrained non-linear optimization requires an estimate of expected consumer demand profile, which is obtained from historical data stored by the SCADA system monitoring the network. Electricity cost patterns, valve positions, pump characteristics, and reservoir properties (volumes, emergency levels, setpoints) are some of the parameters required for the operational optimisation of the system. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2004.

Water distribution systems are large and complex structures. Hence, their construction, management and improvements are time consuming and expensive. But nearly all the optimisation methods, whether aimed at design or operation, suffer from the need for simulation models necessary to evaluate the performance of solutions to the problem. These simulation models, however, are increasing in size and complexity, and especially for operational control purposes, where there is a need to regularly update the control strategy to account for the fluctuations in demands, the combination of a hydraulic simulation model and optimisation is likely to be computationally excessive for all but the simplest of networks. The work presented in this thesis has been motivated by the need for reduced, whilst at the same time appropriately accurate, models to replicate the complex and nonlinear nature of water distribution systems in order to optimise their operation. This thesis attempts to establish the ground rules to form an underpinning basis for the formulation and subsequent evaluation of such models. Part I of this thesis introduces some of the modelling, simulation and optimisation problems currently faced by water industry. A case study is given to emphasise one particular subject, namely reduction of water distribution system models. A systematic research resulted in development of a new methodology which encapsulate not only the system mass balance but also the system energy distribution within the model reduction process. The methodology incorporates the energy audits concepts into the model reduction algorithm allowing the preservation of the original model energy distribution by imposing new pressure constraints in the reduced model. The appropriateness of the new methodology is illustrated on the theoretical and industrial case studies. Outcomes from these studies demonstrate that the new extension to the model reduction technique can simplify the inherent complexity of water networks while preserving the completeness of original information. An underlying premise which forms a common thread running through the thesis, linking Parts I and II, is in recognition of the need for the more efficient paradigm to model and simulate water networks; effectively accounting for the discontinuous behaviour exhibited by water network components. Motivated largely by the potential of contemplating a new paradigm to water distribution system modelling and simulation, a further major research area, which forms the basis of Part II, leads to a study of the discrete event specification formalism and quantised state systems to formulate a framework within which water distribution systems can be modelled and simulated. In contrast to the classic time-slicing simulators, depending on the numerical integration algorithms, the quantisation of system states would allow accounting for the discontinuities exhibited by control elements in a more efficient manner, and thereby, offer a significant increase in speed of the simulation of water network models. The proposed approach is evaluated on a number of case studies and compared with results obtained from the Epanet2 simulator and OpenModelica. Although the current state-of-art of the simulation tools utilising the quantised state systems do not allow to fully exploit their potential, the results from comparison demonstrate that, if the second or third order quantised-based integrations are used, the quantised state systems approach can outperform the conventional water network simulation methods in terms of simulation accuracy and run-time.

M.Ing. / The aim of this research was to investigate the use of stream processing on the graphics processing unit (GPU) and to apply it into the hydraulic modelling of a water distribution system. The stream processing model was programmed and compared to the programming on the conventional, sequential programming platform, namely the CPU. The use of the GPU as a parallel processor has been widely adopted in many different non-graphic applications and the benefits of implementing parallel processing in these fields have been significant. They have the capacity to perform from billions to trillions of floating-point operations per second using programmable shader programs. These great advances seen in the GPU architecture have been driven by the gaming industry and a demand for better gaming experiences. The computational performance of the GPU is much greater than the computational capability of CPU processors. Hydraulic modelling of water distribution systems has become vital to the construction of new water distribution systems. This is because water distribution networks are very complex and are nonlinear in nature. Further, modelling is able to prevent and anticipate problems in a system without physically building the system. The hydraulic model that was used was the Gradient Method, which is the hydraulic model used in the EPANET software package. The Gradient Method produces a linear system which is both positive-definite and symmetric. The Cholesky method is currently being used in the EPANET algorithm in order to solve the linear equations produced by the Gradient Method. Thus, a linear solution method had to be selected for the use in both parallel processing on the GPU and as a hydraulic network solver. The Conjugate Gradient algorithm was selected as an ideal algorithm as it works well with the hydraulic solver and could be converted into a parallel algorithm on the GPU. The Conjugate Gradient Method is one of the best-known iterative techniques used in the solution of sparse symmetric positive definite linear systems. The Conjugate Gradient Method was constructed both in the sequential programming model and the stream processing model, using the CPU and the GPU respectively on two different computer systems. The Cholesky method was also programmed in the sequential programming model for both of the computer systems. A comparison was made between the Cholesky and the Conjugate Gradient Methods in order to evaluate the two methods relative to each other. The findings in this study have shown that stream processing on the GPU can be used in the parallel GPU architecture in order to perform general-purpose algorithms. The results further affirmed that iterative linear solution methods should only be used for large linear systems.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2016 / The water-energy nexus considers the relationship between water and energy resources. Increases in environmental degradation and social pressures in recent years have necessitated the development of manufacturing processes that are conservative with respect to both these resources, while maintaining financial viability. This can be achieved by process integration (PI); a holistic approach to design which emphasises the unity of processes. Within the realm of PI, water network synthesis (WNS) explores avenues for reuse, recycle and regeneration of effluent in order to minimise freshwater consumption and wastewater production. When regeneration is required, membrane-based treatment processes may be employed. These processes are energy intensive and result in a trade-off between water and energy minimisation, thus creating an avenue for optimisation. Previous work in WNS employed a black box approach to represent regenerators in water minimisation problems. However, this misrepresents the cost of regeneration and underestimates the energy requirements of a system. The aim of the research presented in this dissertation is to develop an integrated water regeneration network synthesis model to simultaneously minimise water and energy in a water network. A novel MINLP model for the design of an electrodialysis (ED) unit that is capable of treating a binary mixture of simple salts was developed from first principles. This ED model was embedded into a water network superstructure optimisation model, where the objective was to minimise freshwater and energy consumption, wastewater productions, and associated costs. The model was applied to a pulp and paper case study, considering several scenarios. Global optimisation of the integrated water network and ED design model, with variable contaminant removal ratios, was found to yield the best results. A total of 38% savings in freshwater, 68% reduction in wastewater production and 55% overall cost reduction were observed when compared with the original design. This model also led to a 80% reduction in regeneration (energy) cost. / GS2016

O presente trabalho tem por objetivo apresentar o efeito da redução de pressões nas redes de distribuição sob as perdas reais de água. Para desenvolvimento do trabalho foram recolhidos dados de campo que permitiram avaliar as condições dos sistemas de distribuição e montar modelos matemáticos para realização de simulações hidráulicas. A partir dos modelos, se desenvolveram os estudos de caso para o Setor de Abastecimento de Ermelino Matarazzo (no município de São Paulo) e para o Setor Fonte (em Araraquara). No caso do Setor Ermelino, efetivamente implantaram-se subsetores controlados por válvulas redutoras de pressão (VRPs), obtendo-se reduções significativas na vazão fornecida à distribuição. Para o Setor Fonte, foram realizados estudos para reformulação da setorização existente e subdivisão em Distritos de Medição e Controle (DMCs) levando-se em conta todas as obras para melhoria e adequação do sistema de distribuição. A subsetorização proposta para o Setor Fonte não foi efetivamente implantada, mas os modelos desenvolvidos mostraram que apenas com a subdivisão do setor já é possível a redução nas pressões de distribuição e conseqüentemente redução das perdas reais. Para o Setor Ermelino optou-se pela solução com resultados imediatos através da instalação das válvulas: as perdas reais foram reduzidas, embora tenha significado que 80% da extensão de rede da zona alta do setor tenha ficado protegida por VRPs, o que sugere um desperdício de energia. Já no Setor Fonte buscou-se uma solução mais abrangente para otimização do sistema de distribuição e equilíbrio hidráulico do plano piezométrico, que também apresenta resultados satisfatórios na redução das perdas reais de água. Finalmente, concluiu-se, através dos resultados obtidos em ambos os estudos que a redução das pressões na distribuição está intimamente ligada à redução das perdas reais de água. A diferença entre eles é a abrangência dos estudos. É desejável que o imediatismo dos resultados obtidos pela instalação das VRPs seja confrontado com ações de longo prazo e que a utilização de VRPs seja acessória ao sistema de distribuição e não usada indiscriminadamente. / The following study aims to present the effect of pressure reducing in the distribution networks over the water real loss. For development of the studies, were collected field data that allowed to evaluate the distribution systems conditions and build mathematical models for hydraulic simulations. From the hydraulics models, were developed cases for the Water Supply Ermelino Matarazzo District (in São Paulo) and the Fonte District (in Araraquara). In the Ermelino Districts case, in fact were deployed pressure reducing valves (PRVs) sub-districts, resulting in significant reductions in the supplied flow to the distribution system. For the Fonte District, studies were developed to reformulate the existing sectorization and the subdivision into District Meter Areas (DMAs) taking into account all the activities for improvement and adjustment of the distribution system. The proposal to subdivide the Fonte District had not been effectively implemented, but the models developed showed that only the sub-sector division is enough to reduce the pressure distribution and therefore reduce real losses. For Ermelino District was chosen the solution with immediate results through the installation of the valves: the actual losses have been reduced, meaning that although 80% of the network extension of the High Service Area has been protected by PRVs, which suggests an energy waste. In the Fonte District sought an embracing solution for the distribution system optimizing and gain the best hydraulic balance of the piezometric plan, that also provides satisfactory results in the reduction of real losses. Finally, it was concluded through the results obtained in both studies that, the pressure reduction in distribution system is closely linked to the real losses reduction. The difference between them is the scope of the studies. It is desirable that the immediate results achieved by the PRVs installation be compared with long-term actions and, the use of PRVs should be an accessory to the distribution system and not used indiscriminately.

O presente trabalho apresenta um plano de substituição de tubulações do sistema de distribuição de água da Região Metropolitana de São Paulo (RMSP), utilizando um sistema de informações geográficas (SIG), que permitiu o relacionamento de dados do cadastro físico das tubulações com informações de reparos de vazamentos. Foram criados grupos de tubulações de mesmo material e, em alguns casos, de um mesmo período de implantação, para a definição de taxas anuais de substituição a partir da previsão de quebras futuras e da determinação do tempo ótimo de substituição das tubulações. Os resultados obtidos indicam que a vida média das tubulações apresenta um valor inferior ao verificado em países desenvolvidos. Assim, a taxa anual de substituição de tubulações, devendo oscilar entre 1,25 e 2%, será superior à média dos países desenvolvidos, que gira em torno de 0,5 a 1%, considerando que a idade média das tubulações varie entre 100 e 200 anos. / The following study presents a pipes replacement plan for the water distribution system of the Metropolitan Region of Sao Paulo (MRSP), using a geographic information system (GIS), which allowed the relation between the data of the water mains and the information about leakage repairs. Water main groups of the same material were created and, in some cases, of the same installation period, for the definition of yearly replacement rates based on the future breaks forecast and determination of the water mains optimal replacement timing. The results obtained suggest that the water mains average life, show a lower value than the one verified in developed countries. Thus, the water mains year replacement rate, witch should range from 1.25 to 2%, will be higher than the average in developed countries, witch is about 0.5 and 1%, considering that water mains mean age varies between 100 and 200 years.

O trabalho apresenta uma descrição da estrutura de um sistema de controle de reservatórios em tempo real e as diversas formas de controle existentes, mostrando a necessidade de otimização e automatização do controle. São descritas as experiências de controle operacional baseado em computador obtidas da bibliografia. É apresentado o estado da arte na modelação da operação, no que diz respeito a simulação, otimização e previsão de demandas. E apresentado o sistema adutor metropolitano de São Paulo e descrito o seu sistema de controle operacional. São discutidos dois modelos alternativos propostos para a previsão de consumos em tempo real, baseados em ajustes polinomiais e harmônicos das séries de dados. Analisam-se os resultados de aplicação prática destes modelos quanto a precisão de resultados e a confiabilidade de operação. / This work describes the structure of a reservoir system control in real time. Several usual types of control are shown, focusing on the need for optimization and automation of real time operations. Experiences on operational control based on computer referred in literature are described. The state-of-art of operation modeling concerning to simulation, optimization and demand forecasting is presented. The Metropolitan System of Water Distribution of São Paulo and its operational control system are described. Two proposed models for water demand forecasting in real time are discussed. The first one is based on the concept of polynomial adjustement to water consumption data. The other one uses an harmonic representation of the observed values. Results of practical application of these models are analyzed, in respect of numerical precision and confidence on operational decisions.