The operational management of Water Distribution Systems (WDS), particularly under failure conditions when the behaviour of a WDS is not well understood, is a challenging problem. The research presented in this thesis describes the development of a methodology for risk-based diagnostics of failures in WDS and its application in a near real-time Decision Support System (DSS) for WDS’ operation. In this thesis, the use of evidential reasoning to estimate the likely location of a burst pipe within a WDS by combining outputs of several models is investigated. A novel Dempster-Shafer model is developed, which fuses evidence provided by a pipe burst prediction model, a customer contact model and a hydraulic model to increase confidence in correctly locating a burst pipe. A new impact model, based on a pressure driven hydraulic solver coupled with a Geographic Information System (GIS) to capture the adverse effects of failures from an operational perspective, is created. A set of Key Performance Indicators used to quantify impact, are aggregated according to the preferences of a Decision Maker (DM) using the Multi-Attribute Value Theory. The potential of distributed computing to deliver a near real-time performance of computationally expensive impact assessment is explored. A novel methodology to prioritise alarms (i.e., detected abnormal flow events) in a WDS is proposed. The relative significance of an alarm is expressed using a measure of an overall risk represented by a set of all potential incidents (e.g., pipe bursts), which might have caused it. The DM’s attitude towards risk is taken into account during the aggregation process. The implementation of the main constituents of the proposed risk-based pipe burst diagnostics methodology, which forms a key component of the aforementioned DSS prototype, are tested on a number of real life and semi-real case studies. The methodology has the potential to enable more informed decisions to be made in the near real-time failure management in WDS.

When designing urban water systems (i.e. water distribution and sewer systems) it is imperative that uncertainty is taken into consideration. However, this is a challenging problem due to the inherent uncertainty associated with both system loading requirements and the potential for physical components failure. It is therefore desirable to improve the reliability of each system in order to account for these uncertainties. Although it is possible to directly evaluate the reliability of a water distribution systems (WDS) (using reliability measures), the calculation processes involved are computationally intensive and therefore unsuitable for some state-of-the-art, iterative design approaches (such as optimisation). Consequently, interest has recently grown in the use of reliability indicators, which are simpler and faster to evaluate than conventional direct reliability methods. In this thesis, a novel measure (the RUF) is developed to quantify reliability in urban water systems with a view to enhance their robustness under a range of future scenarios (Policy Reform, Market Forces, Fortress World and New-Sustainability Paradigm). The considered four future scenarios were synthesized in the EPSRC supported multidisciplinary 4 year project: Urban Futures. Each investigated urban future scenario is characterised by a distinct household water demand and local demand distribution (emerging due to different urban forms evolving in future scenarios). In order to assess the impact of urban futures, RUF has been incorporated into Urban Water System (UWS) dynamic simulations for both WDSs and Foul Sewer Systems (FSSs) using open source codes of EPANET and SWMM. Additionally, in order to overcome extensive computational effort, resulting from the use of traditional reliability measures, a new holistic reliability indicator, the hydraulic power entropy (IHPE) has been developed and compared to existing reliability indicators. Additionally, the relationship between the new reliability indicator and the above mentioned RUF reliability measure is investigated. Results suggest that the magnitude of the IHPE in network solutions provides a holistic indication of the hydraulic performance and reliability for a WDS. However, the performance of optimal solutions under some Urban Futures indicates that additional design interventions are required in order to achieve desired future operation. This thesis also proposes a new holistic foul sewer system (FSS) reliability indicator (the IFSR). The IFSR represents sewer performance as a function of excess pipe capacity (in terms of available increase and also decrease in inflow). The indicator has been tested for two case studies (i.e. different sewer network layouts). Results suggest that the magnitude of IFSR has positive correlations with a number of identified key performance indicators (i.e. relating to capacity, velocity, blockages). Finally, an Integrated Design Approach (IDA) has been developed in order to assess the implications of applying design interventions on both a WDS and downstream FSS. The approach holistically considers present and future operation of each interconnected system. The approach was subsequently demonstrated using two proposed design interventions. Results suggest that, for the considered design interventions, there is trade-off between the simultaneous improvement of both WDS and FSS operation and reliability.

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, 2015 / The scarcity of water and strict environmental regulations have made sustainable engineering a prime concern in the process and manufacturing industries. Water minimisation involves the reduction of freshwater use and effluent discharge in chemical plants. This is achieved through water reuse, water recycle and water regeneration. Optimisation of the water network (WN) superstructure considers all possible interconnections between water sources, water sinks and regenerator units (membrane systems). In most published works, membrane systems have been represented using the “black-box” approach, which uses a simplified linear model to represent the membrane systems. This approach does not give an accurate representation of the energy consumption and associated costs of the membrane systems. The work presented in this dissertation therefore looks at the incorporation of a detailed reverse osmosis network (RON) superstructure within a water network superstructure in order to simultaneously minimise water, energy, operating and capital costs. The WN consists of water sources, water sinks and reverse osmosis (RO) units for the partial treatment of the contaminated water. An overall mixed-integer nonlinear programming (MINLP) framework is developed, that simultaneously evaluates both water recycle/reuse and regeneration reuse/recycle opportunities. The solution obtained from optimisation provides the optimal connections between various units in the network arrangement, size and number of RO units, booster pumps as well as energy recovery turbines. The work looks at four cases in order to highlight the importance of including a detailed regeneration network within the water network instead of the traditional “black-box’’ model. The importance of using a variable removal ratio in the model is also highlighted by applying the work to a literature case study, which leads to a 28% reduction in freshwater consumption and 80% reduction in wastewater generation. / GR2016

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. August, 2017 / The foremost aim of potable water treatment is to produce water that does not pose a health risk when consumed and/or otherwise used. Nevertheless, research has established that the quality of treated water deteriorates during distribution. The nature and extent of this deterioration varies from system to system and from time to time. The aim of this research study was to monitor the parameters that are known to significantly affect biostability and biofilm formation potential in drinking water distribution systems. Biweekly water samples were collected from thirteen sites, across a section of Johannesburg Water’s network, between September 2015 and August 2016. All samples were assayed for a suite of fifteen water quality parameters using standard methods. Heightened temperature, dearth of chlorine residuals, availability of biodegradable dissolved organic carbon (BDOC), and advanced water age all engendered the loss of biostability (instability). Biostability controlling parameters varied seasonally and spatially. Samples collected during spring and summer, in general, were most likely to be characterized by instability than samples collected during winter and autumn. Samples collected from sites RW80, RW81, RW82, RW83, RW104 and RW253 were more prone to instability compared to samples from other sites. From the results, it is clear that chlorine residuals ought to be kept above 0.2 mg/l, and, BDOC below 0.3mg/l to prevent the loss of heterotrophic stability in distributed water. BDOC concentrations can be decreased by, flushing the pipes, cleaning reservoirs regularly and by further treating feed water before distributing. Booster disinfection can be relied upon to ensure that chlorine residuals are maintained throughout the network. Apart from potential health risks, biological instability and biofilm growth can result in non-compliance with regulations. / MT2018

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, May 2016. / This thesis presents work on four problems identi ed in the Zomba Water Distribution Network. The research was carried out on the existing network infrastructure with the aim of improving e ciency by reducing Unaccounted-For Water (UFW). The rst challenge was to develop a demand model for the city based on its in uencing factors: daily and seasonal uctuations as well as population dynamics. The model was to capture demand patterns for short-term, medium-term to long-term time periods, thereby becoming an important input factor into decision making. The developed model may be employed to generate demand which can be input into the city's 10 year infrastructure expansion plan. The second problem was to explain why houses built too close to tanks are at risk of inconsistent water supply. It was found that the requirement of observing the tank elevations, helv, had been violated. As a result, the discontinued supplies occurred. Once the required tank elevation helv had been established, an extra increase in the elevation so as to accommodate a larger population was determined to be on the order of one centimeter. Third problem was to explain the continued mains pipe failures observed in the network. It was established that the main cause was the hammering e ects started through the process of manually closing ow control valves (FCVs) tted next to tanks. A possible remedy was to rather t the FCVs at joint nodes and not at the tanks. This was estimated to greatly reduce the hammering e ects, eventually turning them into minor head losses due to elbow bends. Finally, a structural approach to designing tanks that optimize the use of gravity is presented. This is an input into the infrastructure expansion planning of the city. Regardless of any design shapes they may take, tanks with height-radius, h=r, ratio of less than 1 exhibit diminished, as opposed to increased, height changes with demand changes. Such a property would ensure consistency in the pressure at the tank, allowing for delivery of the demanded load. / GR2016

O presente trabalho propõe uma evolução metodológica na operação do Sistema Adutor Metropolitano de São Paulo, em tempo real. Foi implantado um modelo matemático, em tempo real, de previsão de consumo de água horário para uma melhoria na performance operacional. Descrevem-se vários procedimentos de sistema de controle operacional, desde manual até totalmente automático, em sistemas de abastecimento. O sistema de abastecimento de São Paulo é classificado neste contexto. Foi analisada a possibilidade de desenvolvimento da situação atual rumo a um controle mais eficiente, através do uso de um modelo de previsão de demanda de água. O “estado da arte" em modelos de previsão de consumo de água é apresentado através de uma revisão bibliográfica especifica. Foi desenvolvida uma interface entre um modelo de rede hidráulica e um modelo de previsão de demanda de água existente, ambos utilizando dados operacionais, obtidos em tempo real de um sistema de telemetria. A interface foi testada em um estudo de caso do Sistema Adutor de São Paulo. Com a utilização de um modelo de previsão, concluiu-se que é possível estabelecer regras operacionais mais eficientes. Essa eficiência é demonstrada pela redução do número de mudanças de posição de válvula e estado de bombas, bem como é observada a redução do custo de energia elétrica (reduzindo o bombeamento em horário de maior custo). Os benefícios obtidos do uso conjunto do modelo simulador hidráulico e do modelo de previsão de demanda não podem ser considerados como o ótimo global. Seria necessário dispor de um modelo de otimização (programação automática). De qualquer forma, foi concluído que o investimento na implementação desses dois modelos é extremamente atrativa. / This work proposes a methodological evolution of a real time water distribution system operation applied to the Water Mains System of Metropolitan Region of Sao Paulo. It was settled a mathematical model in real time, to forecast hourly water consumptions, intending to increase operational performance. Several operational control procedures of water systems were described, since manual ones until total automatic ones. Sao Paulo system is classified into this concept. The possibility of development from the present status toward a more efficient control was analyzed, through the use of a water demand prediction model. State-of-art of water demand models is presented, through a specific literature review. An interface between a hydraulic network model and an existing water demand prediction model were developed both of them using operational data, obtained in real time by a telemetric system. The interface was tested in a case study of Sao Paulo Water Mains System. One concludes that through the use of the prediction model, it was possible to make more efficient operational schedules. This efficiency is demonstrated by the reduction in number of valve positions changes and in pump status changes, as well as a decrease in energy costs could be observed ( reducing pump operations in hours of more expensive costs). Benefits obtained by the conjunctive use of the hydraulic simulation model and the water demand prediction model can not be admitted as the global optimum. It would be necessary to make available an optimization model (automatic scheduler). However it was concluded that investment in these two models implementations is extremely attractive.

A ocorrência de ventos pode modificar a distribuição da água aplicada por microaspersores, comprometendo a eficiência e a uniformidade de aplicação. Os ensaios para avaliar essa distribuição são, geralmente, demorados sem que se consiga, muitas vezes, realizar as avaliações em todas as condições operacionais e ambientais necessárias. O uso de modelos matemáticos para simulações computacionais possibilita, assim, uma combinação mais diversificada e rápida das análises pretendidas. Apesar de ser considerada, normalmente, como um método de irrigação localizada, a microaspersão apresenta características hidráulicas e de operação mais próximas à aspersão do que ao gotejamento. Os modelos de simulação desenvolvidos para os sistemas de aspersão podem, assim, ser utilizados na microaspersão. O presente trabalho teve como objetivo geral, avaliar o desempenho de um modelo balístico, desenvolvido originariamente para sistemas de aspersão convencional, na simulação da distribuição de água aplicada por microaspersores operando sob condição de vento. As avaliações experimentais foram realizadas em condições de laboratório empregando-se microaspersores da marca Dan 2001, com diâmetros de bocais iguais a 0,84 mm (violeta), 1,00 mm (cinza), 1,10 mm (marrom), 1,25 mm (azul), 1,33 mm (verde), 1,48 mm (laranja) e 1,75 mm (amarelo). Os bocais violeta, cinza e marrom trabalharam com rotor preto e os demais bocais trabalharam com rotor azul. O efeito do vento foi provocado artificialmente empregando-se um conjunto de quatorze ventiladores de 200 W de potência e 0,50 m de diâmetro interno. Para as simulações da distribuição de água foi utilizado o programa computacional SIRIAS (SImulación de RIego por ASpersión), desenvolvido para aspersores convencionais e que se baseia na teoria balística das trajetórias de gotas. As simulações da distribuição de água na ausência de vento apresentaram desempenhos considerados ótimos para todos os bocais analisados. Por sua vez, o desempenho do modelo para simular a distribuição de água na presença de vento variou conforme o bocal e o rotor utilizado. Para os bocais que empregaram rotor preto, o desempenho foi classificado como péssimo para o de cor violeta e muito bom para os bocais cinza e marrom. Para os demais bocais que operaram com rotor azul o desempenho foi considerado regular. / Wind occurrence can modify water distribution by microsprinklers, reducing application efficiency and uniformity. Experimental tests to evaluate this distribution are, normally, cumbersome and frequently they can not be realized at all the operational and environmental conditions. The use of mathematical models for computational simulations permits, therefore, a more diversified and quickly combination of the intended analyses. Although it can be considered as a localized irrigation method, microsprinklers present operational and hydraulic characteristics closer to sprinkler than to drip irrigation. Simulations models developed for sprinkler systems can, therefore, be employed by microsprinklers. The present work had as a general objective the evaluating of a ballistic model, originally developed for sprinkler systems, on simulating water distribution by microsprinklers under windy condition. Experimental tests were carried out in laboratory using Dan 2001 microsprinklers with nozzle sizes of 0.84 mm (violet), 1.00 mm (gray), 1.10 mm (brown), 1.25 mm (blue), 1.33 mm (green), 1.48 mm (orange) and 1.75 mm (yellow). The violet, gray and brown nozzles operated using black spin and the others used blue spin. The wind effect was artificially simulated using fourteen fans (200 W power). Computational simulations were run employing the software SIRIAS, that is based on a ballistic model originally developed for sprinkler systems. Water distribution simulations in conditions of wind absence presented excellent performance for all the analyzed nozzles. In the other side, the model performance for windy condition varied according the nozzle and the utilized spin. For the black spin nozzles the performance was classified as very bad, for the violet one, and very good, for the gray and brown nozzles. For the others nozzles, that operated with blue spin, the performance was considered as regular.

O presente trabalho apresenta uma avaliação de otimização de um sistema complexo de adução de água tratada, em tempo real, com Algoritmos Genéticos (AG’s), associado a um sistema SCADA e a um modelo de simulação hidráulica de rede (Epanet 2.0). Foram utilizados registros históricos de consumos de água, considerados como previsão perfeita. O estudo de caso foi feito em uma parte do Sistema Adutor Metropolitano (SAM) de São Paulo para minimizar uma função multiobjetivo (custos de energia e restrições operacionais). Foram analisados seis cenários com diversas combinações de pesos, tamanhos da população, número de gerações e probabilidades de cruzamento e mutação. As estratégias de operação obtidas permitiram reduções de até 22% na potência consumida e uma redução expressiva do custo de energia pela redução dos bombeamentos nos horários de tarifas mais elevadas. / This work presentss an evaluation of optimization of real time operation of a complex water supply system. Genetic Algorithm associated with a SCADA system and a network hydraulic simulation model was applied. Observed historic consumptions were used as a perfect water demand forecast model. Case study is the optimization of a multiobjective function (energy cost and operational restrictions) subsystem of Water Mains System of São Paulo Metropolitan Region. Six representative combinations of population size, number of generations , crossover and mutation probabilities were analyzed, Operational schedule of pumping and valve controls led to reductions in power consumptions up to 22% and expressive lower operational costs due to reductions of pumping in eenrgy peak times.

Atualmente a avaliação das perdas de água, nos sistemas de distribuição, é feita com base em equações empíricas, que utilizam informações, agrupadas e totalizadas, de uma área. Isto torna necessária sua subdivisão em frações cada vez menores, na busca da fração mais crítica. Neste trabalho, é apresentada uma avaliação da eficácia do uso de modelos de simulação hidráulica na obtenção das informações necessárias para a elaboração de um diagnóstico de perdas de água, com uma metodologia prática para o uso de modelos com este objetivo. Apresenta uma classificação dos trechos de rede em três categorias A, B e C, que facilita a priorização dos trechos mais críticos facilitando a análise por meio de gráficos de pareto e mapas temáticos. Demonstra que a adoção da simulação hidráulica no estudo das causas de perdas de água, nos sistemas de abastecimento, é uma ferramenta eficaz e permitirá às empresas de saneamento, uma melhoria na gestão operacional, que garante a sustentabilidade da empresa, a economia dos recursos humanos, econômicos, e principalmente, os hídricos. / Currently water losses evaluation in distribution systems, is based on empirical equations using information, grouped and totaled, covering whole area. Thus, becomes necessary to subdivide the area into smaller and smaller fractions, searching for the most critical part. This study presents, the effectiveness evaluation of the hydraulic simulation models, use to obtain the information necessary in elaboration diagnosis of water losses, with a practical methodology for using models for this purpose. Shows a pipe classification in three categories A, B and C, its began possible analyses with pareto graphics and thematic maps. Demonstrates that hydraulic simulation adoption is an effective tool in the study of water loss in supply systems. It will allow companies an operational management improvement, ensuring the sustainability of the business and economics of human, financial, and especially, water resources.

As mudanças físicas ocorridas ao longo do tempo requerem que os modelos hidráulicos de previsão de comportamento das redes de distribuição de água para abastecimento tenham seus parâmetros reavaliados periodicamente via calibração. Diversas são as dificuldades inerentes ao processo de calibração de redes reais, dentre as quais aquelas resultantes da precariedade dos cadastros, como a incerteza quanto à localização e condição de abertura de válvulas na rede. Muitos métodos de calibração foram propostos na literatura, geralmente com base em equações analíticas e técnicas de otimização diversas. Reconhece-se, entretanto, a necessidade de estimativas dos parâmetros da rede em termos das rugosidades e dos parâmetros locais da relação entre pressão e vazamento, para sistemas sujeitos a vazamentos expressivos. Propõe-se aqui um método de calibração em duas etapas em que os AGs (algoritmos genéticos) são empregados como ferramenta na resolução dos problemas inversos correspondentes, sendo os estudos realizados para setores de rede da cidade de São Carlos, SP, sobre os quais extensivos trabalhos de campo foram realizados. Foram desenvolvidos também estudos de investigação da melhor representação do problema via AGs e de localização de pontos ótimos de monitoramento. Os resultados demonstraram-se robustos em identificar rugosidades e trechos dotados de válvulas, bem como os parâmetros do modelo de vazamentos, além de indicar possibilidades de melhorias na eficiência dos AGs. Resultados obtidos a partir de considerações sobre técnicas de localização de pontos ótimos de monitoramento também foram considerados bons. / Continuous physical changes that occur in water supply networks along the years require their calibration in order to guarantee realistic forecasts through hydraulic models. There are many difficulties involved in water supply network calibration in terms of their parameters as results of many factors, amongst which the lack or uncertainty on data like location and status of valve openings in the network. Several calibration methods have been proposed in the literature, usually based on many analytical equations and optimization techniques. However, it was known the need of estimative of network parameters in proper form of roughnesses and local parameters of relation between pressure and leakage, for systems submitted to expressive leakages. This work proposes a method of calibration in two phases in which the GAs (genetic algorithms) are used as tools in the resolution of corresponding inverse problems, being the studies performed for sectors of the network of the city of São Carlos, SP, about which extensive field work had been done. It was developed, also, studies investigating of the best representation of problem through GAs and the localization of optimal points for monitoring. The results have showed themselves robust in the identification of roughnesses and sections having valves, as well as the parameters of leakage model, besides to indicate possibilities of improvements in GA\'s efficiency. The results that have been obtained from considerations aboutlocalization techniques of optimal points for monitoring were considered good as well.