Resumo:
Mathematical modeling of water quality is considered an important tool for evaluating the impact of the release of polluting loads, as well as analyzing intervention scenarios, control measures, verifying and quantifying the self-purification process of water bodies and simulating future water quality scenarios. The main objective of this research was to contribute to the management of water resources to verify the impact generated by the implementation of a sewage treatment plant in the city of Caratinga - WWTP Caratinga, whose effluent is discharged into the Caratinga river and analyze the self-purification capacity of this river. The QUALUFMG mathematical model was used to evaluate the impact of the sewage treatment plant and the self-purification capacity in the section that comprises the specific launch of the ETE Caratinga. The study considered the variables biochemical oxygen demand (BOD) and dissolved oxygen (DO). The simulations were carried out for raw effluent scenarios (before the implementation of the Caratinga WWTP) and effluent with 60% and 90% BOD removal efficiency in the treatment. Scenarios were also created considering the increase in pollutant load released as a result of the increase in population in the basin for the years 2033 and 2041. In the current scenario, the variables presented values for the RMEQ index (Root Mean Squared Error) of 0.66 for BOD and 0.66 for OD. The DO and BOD remained within the limits established for class 2 waters based on CONAMA Resolution 357/2005 at 90.5% and 72.1%, respectively. For a scenario in 2033, the analyzed parameters would remain within the limits established for class 2 waters of CONAMA Resolution 357/2005 at only 53.1% for DO and 8.8% for BOD. For scenarios considering the 60% efficiency of BOD removal (minimum limit for launch established by CONAMA Resolution 430/2011), the entire stretch, after km 36.4 (launch point of ETE Caratinga), would be outside the limits established for class 2 waters of CONAMA Resolution 357/2005. Thus, it was found that, for better management of water resources in the Caratinga river basin, it is necessary to intensify effluent treatment and control over polluting sources, considering the efficiency of sewage treatment and the number of inhabitants of the main cities of the basin, in addition to increasing effluent treatment coverage in the respective municipalities.
