Diagnóstico e prognóstico de qualidade da água em ambiente lótico urbano. Estudo de caso: Córrego Mumbuca, Monte Carmelo (MG)

Abstract

The Mumbuca stream, which flows through the urban area of Monte Carmelo, Minas Gerais, in the Triângulo Mineiro region, is the water body receiving raw sewage; the deficiency of a sewage system hampers the maintenance of the equilibrium of the aquatic ecosystem and brings social and economic losses to the local population. The objective of this study is to diagnose and forecast the water quality in an urban lotic environment, specifically the Mumbuca Stream in the city of Monte Carmelo (MG), with the main impacting variables being land use and occupation as well as urban sewage and stormwater drainage infrastructure. With a bimonthly seasonality during drought periods, the parameters pH, water temperature, total suspended solids, turbidity, dissolved oxygen, biochemical oxygen demand, total phosphorus, organic nitrogen, ammonia, and nitrate were characterized at four monitoring stations along the Mumbuca Stream. Regarding the mathematical modeling of self-purification using the WASP computational tool, after calibrating the kinetic terms inputted into the simulations of the parameters dissolved oxygen, biochemical oxygen demand, ammonia, nitrate, and total phosphorus, the maximum pollutant loads of organic matter, nitrogen, and phosphorus that the stream can support without compromising the limit concentrations established in CONAMA Resolution 357 (2005) were evaluated. The results obtained from the calibration process of the water quality model indicate that the Mumbuca Stream, during drought periods, does not have self-purification capacity for the pollutant loads from the clandestine connections of raw domestic sewage, with the maximum admissible loads obtained in the study being 7.0 kg BOD/day, 1.0 kg Ammonia/day, and 0.02 kg Total Phosphorus/day.