Caracterização e tratamento de águas pluviais visando seu aproveitamento em edificações

Abstract

The rapid growth in urban population, alongside with the growing demand for water, as well as the imminent prospect of its scarcity, has led to serious pressures on water resources, making water conservation a current topic of great importance. Although Brazil has one of the largest water resources on the planet, water conservation measures are necessary, especially in large urban areas. The use of rainwater, in order to reach part of the demand for residential consumption, is an effective alternative and has been practiced all over the world for many years. However, depending on the desired consumption, some types of treatment may be necessary for safe use. Therefore, this study characterized the rainwater captured in roof tops and different treatment possibilities were analyzed for use in residential buildings. Rainwater was sampled from the roof-water drainage of one of the housing units called Efficient Popular House, built at the Federal University of Santa Maria (UFSM) in Santa Maria / RS. The system of capture included the installation of gutters, conductors, filter, first flush and reservoir. Rainwater was characterized according to its physical-chemical and microbiological features, and these are associated to the characteristics of precipitation events, both in the disposal system and in the reservoir. The evaluated treatments consisted of filtration, discard of the first two millimeters of rainfall, and disinfection in order to obtain quality water, without risks to users' health. For this, chlorine and ozone were tested as disinfectants agents and, based on the final quality of the obtained water, the possible non-drinkable uses were established according to Brazilian and international resolutions. The final quality of the water obtained after filtration, discard of the first two millimeters of precipitation and chlorine disinfection at 0.5, 1.0 and 1.5 mg L-1, and with ozone at 5, 10 and 15 minutes. Results indicated that there is a tendency to improve rainwater quality, as there are a lower number of days with no previous precipitation, and also the improvement in quality with increasing volume precipitation intensity was identified. In addition, it was possible to show that the first two millimeters of discarded rainfall improved in the quality water parameters stored in the reservoir. After the disinfection step, the coliform parameter was absent in all analyzes for chlorine at the concentration of 1.5 mg L-1, and ozonization of 15 minutes.