RESUMO O dimensionamento ótimo de redes de distribuição de água (RDA) tem recebido atenção especial de projetistas e pesquisadores devido, principalmente, aos elevados custos de implantação, operação e manutenção. No entanto, a baixa eficiência computacional da maioria dos algoritmos dificulta a aplicação desses em RDA de grande porte. Diante disto, este artigo apresenta um algoritmo híbrido (H-PSOTS) baseado nos métodos particle swarm optimization (PSO) e tabu search (TS) para o projeto de RDA. Incorporar a TS, como um procedimento de melhoria da busca local, permite que o algoritmo H-PSOTS evite ótimos locais e apresente um desempenho satisfatório. O PSO padrão e o H-PSOTS foram aplicados a três redes de referência propostas na literatura: Balerma irrigation network, ZJ network e Rural network. O algoritmo híbrido obteve bons resultados na busca pela solução ótima e alto desempenho computacional, tornando-se uma nova opção para o projeto ótimo de redes de distribuição de água reais.

ABSTRACT Water distribution network (WDN) optimization has received special attention from various technicians and researchers, mainly due to its high costs of implementation, operation and maintenance. However, the low computational efficiency of most developed algorithms makes them difficult to apply in large-scale WDN design problems. This article presents a hybrid particle swarm optimization and tabu search (H-PSOTS) algorithm for WDN design. Incorporating tabu search (TS) as a local improvement procedure enables the H-PSOTS algorithm to avoid local optima and show satisfactory performance. Pure particle swarm optimization (PSO) and H-PSOTS algorithms were applied to three benchmark networks proposed in the literature: the Balerma irrigation network, the ZJ network and the Rural network. The hybrid methodology obtained good results when seeking an optimal solution and revealed high computational performance, making it a new option for the optimal design of real water distribution networks.

RESUMO As funções de retenção de água no solo e condutividade hidráulica são indispensáveis para a caracterização e modelagem dos processos de infiltração e transferência de água na zona vadosa. No caso do semi-árido brasileiro, caracterizado pela escassez de recursos hídricos, faltam informações sobre as propriedades hidrodinâmicas do solo. Além disso, essas propriedades possuem inúmeros fatores de variabilidade, sendo essencial a caracterização de sua magnitude, bem como sua distribuição no espaço. Esta pesquisa apresenta uma análise das propriedades hidrodinâmicas de um solo sob mata nativa da Caatinga, típica do semi-árido brasileiro, observando sua distribuição espacial. Uma malha de 48 pontos foi desenvolvida em uma área de aproximadamente 875 m2, onde foi aplicada a metodologia Beerkan. As análises foram realizadas com base na aplicação do algoritmo BEST-Slope e em medidas estatísticas de posição, dispersão e aderência. Os resultados mostraram índices de variabilidade médios a altos para as propriedades hidrodinâmicas, com distribuição espacial aleatória, apesar da verificação de uma textura homogênea na área. Assim, verificou-se que a estrutura do solo foi preponderante nos processos de infiltração de água.

ABSTRACT The functions of soil water retention and hydraulic conductivity are indispensable for the characterization and modeling of the infiltration and water transfer processes in the vadose zone. In the case of the Brazilian semi-arid region, characterized by the scarcity of water resources, there is a lack of information on the hydrodynamic properties of the soil. Also, these properties have numerous factors of variability, requiring the characterization of their magnitude and distribution in space. This research presents an analysis of the infiltration process and the hydrodynamic properties of the soil under native Caatinga forest, observing its spatial distribution. This vegetation is typical of the Brazilian semi-arid region. One developed a 48-point grid in an area of approximately 875 m2, and applied on it the Beerkan methodology. The analyzes were performed based on the application of the BEST-Slope algorithm and statistical measures of the position, dispersion, and adherence tests. The results showed medium to high variability indices for the hydrodynamic properties, with random spatial distribution, despite the verification of a homogeneous texture in the area. Thus, it was found that the soil structure was predominant in the processes of water infiltration.

Resumo Em um cenário de crise hídrica, como o vivenciado pelo Agreste Brasileiro nos últimos anos, a sustentabilidade do abastecimento de água tem sido tema de inúmeras investigações. Nesse sentido, esta pesquisa abordou o estudo da implantação hipotética de alternativas tecnológicas direcionadas à redução do consumo de água potável em residências de Caruaru, PE. As alternativas adotadas foram avaliadas segundo uma perspectiva multicritério, considerando critérios ambientais, técnicos, econômicos e sociais, identificados por meio de projetos, pesquisas de mercado e entrevistas com moradores e especialistas. Com a aplicação do método Promethee II, foi possível verificar que a implantação de equipamentos economizadores seria a alternativa mais indicada para a região. A redução no consumo de água dessa alternativa foi de 29,11%, enquanto o tempo de retorno do investimento foi estimado em 16 meses. O elevado prazo para recuperar o capital das demais alternativas evidencia a necessidade de políticas governamentais que ofereçam incentivos financeiros à população, de modo a impedir que as condições socioeconômicas da região sejam o principal entrave para a adoção de práticas de conservação dos recursos hídricos.

Abstract In a scenario of water crisis, such as that experienced by the Brazilian Agreste region in recent years, the sustainability of water supply has been the aim of several investigations. This research project involved the study of the hypothetical implementation of technological alternatives for reducing household potable water consumption in Caruaru, PE. The alternatives were evaluated from a multicriteria perspective. That perspective takes into account environmental, technical, economic and social criteria, which are identified through designs, market research and interviews with residents and experts. With the application of the multicriteria method Promethee II, it was possible to verify that the implementation of water-saving devices is the most suitable alternative for the region. This alternative promotes a 29.11% reduction in water consumption, while the payback period was estimated at 16 months. The long term required to recover the capital in the other alternatives highlights the need for government policies offering financial incentives to the population, preventing the region’s socioeconomic conditions from being the main obstacle for the adoption of water resources conservation practices.

Resumo De acordo com os dados do Sistema Nacional de Informações sobre Saneamento (SNIS) do Brasil, do total da água produzida pelas companhias de saneamento em 2016, cerca de 38% foram perdidos na distribuição, entre perdas reais e aparentes. Além das perdas de água, perdem-se outros insumos, recursos financeiros e mão de obra que poderiam ser investidos na melhoria e na reabilitação de ativos das empresas. A presente pesquisa objetiva avaliar o abastecimento de água de municípios do Agreste brasileiro com base em indicadores do SNIS relacionados às perdas de água. A metodologia fundamentou-se em estatística descritiva, de modo que os valores dos indicadores operacionais adotados de cada munícipio foram comparados com valores de referência, a fim de analisar a eficiência dos sistemas de abastecimento de água e estabelecer um benchmarking da região. Os melhores resultados foram da Embasa (Bahia), enquanto o estado com pior desempenho foi o de Sergipe. O estudo fornece subsídios aos gestores de companhias estaduais para a priorização de investimentos em sistemas ineficientes.

Abstract According to the 2018 report produced by the National Sanitation Information System (hereby referred to by its Brazilian acronym SNIS), 40% of the total amount of water treated by state water utilities in 2016 was lost during its distribution, either through real losses or due to apparent losses. In addition to water, other types of loss are incurred in, such as financial resources and labour, moreover, the financial resources associated with these losses could otherwise be invested in improvements of the companies’ systems. This study aims to evaluate the performance of state water utilities in controlling and reducing water loss in supply systems based on the SNIS indicators in municipalities of the Brazilian Agreste. The methodology was based on descriptive statistics. Therefore, the adopted values of the operational indicators in each municipality were compared with reference values in order to analyse the efficiency of water supply systems and to establish a benchmark for the region. The best results were from Embasa (Bahia), while the worst performing state was Sergipe. The study provides useful information to managers of state companies when prioritising investments to improve inefficient systems.

RESUMO Esta pesquisa objetivou projetar um sistema de controle adaptativo para o modelamento e controle, em tempo real, de um sistema de distribuição de água. Os controladores atuaram no controle da pressão por meio da variação da velocidade de rotação do sistema de bombeamento e do ângulo de abertura de válvulas de controle. O sistema de controle é do tipo Variância Mínima Generalizado (GMV) autoajustável, cujos parâmetros foram estimados em tempo real pelo método dos mínimos quadrados recursivo (MQR). Os ensaios realizados na bancada experimental apresentaram resultados satisfatórios, com um erro máximo no controle de pressão de 2,12% (0,42 mca) e uma redução de 19,2% no consumo de energia elétrica para o sistema atuando na condição mais desfavorável.

ABSTRACT This research aimed to design an adaptive control system for modeling and real-time control of a water distribution system. Air traffic controllers acted on pressure control by varying the rotational speed of the pumping system and opening angle control valve. The system of control is of type Generalized Minimum Variance self-tuning, whose parameters were estimated in real time by the recursive least squares method. The tests performed on experimental workbench presented satisfactory results, with a maximum error on pressure control of 2.12% (0.42 mca) and a decrease of 19.2% in the consumption of electrical energy to the system in the most unfavorable condition.

This paper presents a fuzzy system to control the pressure in a water distribution network, by using valves and controlling the rotor speed of the pumping systems. The variable frequency drive tracks the minimum head of the pumping system, while the control valves have the function of eliminating the excess pressure at various points of the network. The control system can track any reference pressure value and there is no limit for the number of monitored points. Experiments were carried out to demonstrate the fuzzy system's efficiency. By extrapolating the results achieved in the experimental setup to a real hydraulic network with leakages and no pressure control, the volumetric losses could be reduced by more than 56%. The experiments showed that the system is robust enough to control the pressure of an experimental setup of water distribution. Besides, the proposed system can be easily applied to similar water supply systems and would help to reduce the consumption of water and electricity, as well as to reduce the maintenance costs.

This study is aimed at developing a pipe-sizing model for a water distribution system. The optimal solution minimises the system's total cost, which comprises the hydraulic network capital cost, plus the capitalised cost of pumping energy. The developed model, called Lenhsnet, may also be used for economical design when expanding existing hydraulic networks. The methodology developed includes an iterative dynamic calculation process as well as a hydraulic simulation model. The performance of the method is tested against 4 benchmark examples in the literature. The results obtained show the feasibility of this model, presenting it as a viable alternative for water distribution systems. The method is easily used, once it is performed under EPANET2 software interface.

This paper presents an iterative method for the optimisation of the total costs for the rehabilitation of water-supply pipe networks with flow and pressure deficiency at the consumer nodes. The procedure is based on the exchange gradient concept of Granados for the economic design of pressurised networks. The substitution of pipe sections, relining and increase in pumping head are considered as being rehabilitation options. An initial solution is obtained for the deficient network by determining the required pumping head that would meet the pressure and discharge requirements at all the nodes. Subsequently, the pumping head is reduced in stages and for each reduction; the network of minimum cost is obtained by the substitution or relining of individual pipes in part or in full. The optimal solution is reached when the marginal annual cost of pipe rehabilitation exceeds the reduction in annual pumping costs.