Avaliação da eficiência de redes de distribuição de água ao longo da sua vida útil

Abstract

The infrastructure responsible for distributing water to various types of consumers is the water distribution network (WDN). Because it is a basic infrastructure to serve the most varied human needs, besides having a very complex dynamic functioning, these are widely approached in literature studies. WDN operate for long periods of time, and in this context the present work proposes to evaluate the impact that changes in physical and hydraulic characteristics that occur over the operational life of a WDN, such as pipe roughness, leakage rate, water consumption and pump deterioration, will have on its operational efficiency and in terms of costs. For this, the variations of each of the parameters cited were mathematically modeled within a programming environment (MATLAB), coupled to the hydraulic simulator EPANET 2.2, for analysis in two case studies with networks from the literature. The roughness of the pipes was modeled assuming that it increases at a known rate using the Hazen-Williams equation. The leakages were formulated considering a minimum flow that increases with time, plus a variable value depending on the pressure fluctuation of the network, calculated by the orifices equation. The increase in demand was carried out considering that consumption grows in the same proportion as the increase in population, which was estimated by IBGE growth rates. The deterioration of the pumps was performed by calculating a new head at each period of time, following formulations and rates observed in the literature. All parameters cited were varied around an average reference value, as a way of representing uncertainties. After the analyses performed on the parameters, considering a lifetime of 20 years, two energy efficiency measures were implemented and evaluated in one of the case studies, and later these had their feasibility analyzed from an economic point of view. The results of the parameter analyses showed that operating costs are most impacted by network leakage, and operating pressures are most influenced by increased pipe roughness. Energy efficiency measures have proven to be very relevant in order to maintain the proper functioning of the network throughout its lifetime. Regarding the financial analyses, these showed that the implementation of energy efficiency measures are attractive also from an economic point of view, as they brought reductions in total costs in long term.