Análise temporal de projetos de esgotamento sanitário baseada na projeção populacional e no índice de qualidade de água para o município de Barra do Piraí-RJ

Abstract

The New Legal Framework for Basic Sanitation, enacted in 2020, covers a series of regulations with the aim of improving basic sanitation conditions in Brazil, such as 90% of the population having access to sewage collection by December 31, 2033 and 99% of the population with access to treated water up to the same date. In this way, managers and decision makers of public bodies must pay attention to deadlines. The Municipality of Barra do Piraí has a territorial area of 578.47 km² and is located in the Middle Paraíba region, where the population in 2021 was 101,139 thousand inhabitants. Despite the abundance of water in the city, its rivers suffer from direct pollution to their fullest extent, through the discharge of sanitary sewage in natura. The City Hall has basic sewage projects in its archives, of which only one was built in the Barra district of California and is currently inoperative. The first item to be observed in sanitation projects is the population projection, as it delimits a study horizon and makes it possible to project the flow of sewage stations, the network, among others. The projection is important for the project to be valid for many years following the population growth rate, however, it cannot be oversized, so that it does not burden the public coffers without reason. Therefore, the objective of the work was to evaluate existing sewage projects to verify the methodology used for population projection, compare with the current population with the projection at the time of the project delivered, in addition to presenting data such as the amount of sewage generated and the comparison with the maximum design flows. The calculation of the CCME water quality index was presented as a demonstration of the water quality of the river. For the projection, the following methods were used: geometric, AiBi, Arithmetic, Power, Exponential and Polynomial and compared with the population growth rate of the city to determine the best method. The CCME water quality index was calculated using the calculator provided by the Canadian committee itself and to base the amount of sewage generated in relation to the amount that could be treated, the per capita estimate of water consumption was calculated considering the return coefficient of 0.8. The water quality is in decline and the projects still meet what they were specified, however, there is a need to reassess the projection used for the AiBi method, considering that it was the one that best suited the population growth rate of Barra do Pirai. In this way, the City Hall can reconsider these previously shelved projects, as alternatives for the universalization of sanitary sewage treatment, so that it is a first step for similar projects to be made feasible to serve the entire population of Barrense.