Modelagem da qualidade da água utilizando os modelos Streeter-Phelps e QUAL-UFMG na Bacia do Rio Lambari - Poços de Caldas (MG)

Abstract

This study is aimed to evaluate the process of self-depuration of the river Lambari on the stretch that comprises the timely release of the domestic sewage from the urban area of Poços de Caldas (MG). There were 5 sampling points (P1 to P5) established along the section studied, the variables analyzed in the field and laboratory were: pH, air and water temperature, conductivity, dissolved oxygen, biochemical oxygen demand, nitrate, phosphate, fecal coliforms, total dissolved and suspended solids and turbidity. Besides water quality, flow measurements were made at point P4 for 1 (one) hydrological year. Two models were used to calibrate the water quality variables, the traditional model of Streeter-Phelps and the QUAL-UFMG model. After calibration, the simulation was performed for two scenarios, the scenario with 60% of efficiency of released wastewater treatment and the scenario with 90% of efficiency of sewage treatment. The results achieved showed that water quality deteriorated in the month of August/2013, fact related to the difficulty of dilution and self-depuration of the river, due to the low rainfall of the month. With the flow values it was possible to obtain the curve - Key Q = 29,0574.(H-0,26191)1,1618, so this may optimize future work. The calibration of the two models, in general, had acceptable and plausible results, the coefficients proved themselves with a good grip to the field data. The simulation results indicated that the efficiency to 60% of the treatment is reasonable for the river Lambari to recover up to its mouth, reaching the Class 2 standards established by CONAMA Resolution 357/05. In general, the tools for simulating the processes of self-depuration of the water bodies used, the Streeter-Phelps model and QUAL-UFMG, proved to be useful for decision making in the management plans of water resources.