Uso da modelagem de qualidade da água na gestão dos recursos hídricos aplicada à bacia do rio Santo Antônio/MG

Abstract

The release of untreated domestic effluents into water bodies is one of the major problems of basic sanitation, which has several implications for water quality and reflects on the health of the population that depends on it. Allied to this, high investments in this sector are necessary to solve this problem, and for this reason, it is essential to carry out an efficient planning using tools that enable the analysis of the interactions that occur in the water body. For that, mathematical models can be used, which jointly analyze water quality and quantity, in addition to simulating the current and future behavior of the water body. Thus, the objective of this research is to evaluate alternatives for the management of water resources for the Santo Antônio River basin, using mathematical modeling of water quality. The modeled parameters were: dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrogen variations (organic, ammoniacal, nitrite and nitrate), total phosphorus and Escherichia coli using the QUAL-UFMG model. For the calibration and validation of the model, data from the monitoring of quality fluviometric stations located on the Santo Antônio river were used. At the end, 3 intervention scenarios were simulated, foreseeing the implementation of effluent treatment systems and considering the initial stretch of the river with a more restricted classification, class 1. The results showed that the Santo Antônio river has self-cleaning and dilution capacity for all parameters analyzed, with the exception of total phosphorus in the section near its mouth. In the current scenario, the total phosphorus modeling revealed that only 14.8% of the stretch near its mouth meets the legislation. However, in the scenarios that envisaged the implementation of effluent treatment in all urban centers in the basin, the stretch became compliant in 66.8% of its extension. When considering part of the stretch of the river as class 1, the modeling of future scenarios for the E. coli parameter indicated the need for secondary effluent treatment in all urban centers of the basin. On the other hand, BOD modeling revealed that the implementation of secondary treatment systems only in urban centers with a population greater than 5,000 inhabitants would be able to decrease concentrations to values within the limit of the legislation. This demonstrates that the modeling of DO and BOD alone is insufficient to determine the need for intervention to improve the quality of water in a watercourse.