Modelagem da poluição difusa em sistemas de macrodrenagem de bacias urbanas.

Abstract

Indiscriminate urbanization, with the removal of vegetation cover from the basin and the expansion of impermeable land, together with inefficiency of basic sanitation services, contributes to the process of launching polluting loads transported superficially by rainwater, causing negative impacts on the urban drainage system. Thus, the objective of this work is to evaluate the diffuse pollution process in the macro drainage system of the Riacho do Prado Watershed through monitoring and mathematical modeling using the Storm Water Management Model (SWMM). For this, 8 points were monitored in the drainage canal, with the analysis of physical, chemical and biological indicators of water quality, in addition to the determination of the flow rate, which was also done for 10 points of sanitary sewage in the canal. By analyzing the concentrations of the pollutants, it was found that the highest concentrations are found during dry periods. It was also verified that the pollution in the area increased considerably in 4 years, which indicates a high danger for the population that lives near the canal. By applying the SWMM model to the simulation of the dry weather flow (DWF), which simulates the continuous discharge of sanitary or industrial wastewater, it was concluded that small interventions that were to be made in the canal would not show a significant improvement in the quality of the drainage system as a whole, the improvements would be only local. As for the analysis of the hydrological periods, it was observed that the number of previous days without rain and the volume precipitated were important for the analysis of the process of buildup and wash off of the polluting charge. Analyzing the effect of the reduction of waterproofing on the washed out load of pollutants, it was verified that the drained volume is also an important factor, since it influences the transportation and dilution of the pollutants illegally dumped by the sewage connections in the drainage gallery. Different from what is observed in a purely quantitative approach, the reduction of impermeable areas is not an interesting action in relation to the improvement of canal water quality. It can be concluded that the program responded well to the simulation of hydraulic and hydrological phenomena occurring in the basin and in the storm drainage galleries. Regarding the modeling of water quality, the results obtained for simulations of the behavior of the pollutants in time scale for the actual event of 8/6/2018 were in agreement with the values observed in the laboratory analyzes, confirming the efficiency of the results for the others performed.