Estudo da remoção de poluentes de águas da drenagem urbana por um dispositivo de biorretenção

Abstract

Bioretention is a type of urban drainage control technique that contemplates filtration, storage and infiltration processes, containing an upper layer of vegetation. Thus, this device can be used for various purposes in the area of storm water management, among them, to reduce the peak flow, to maintain groundwater recharge and to remove pollutants. However, the performance of this technique is conditioned by factors ranging from regionality (climate, soil characteristics) to the design of its project. In this sense, the main objective of this work was to perform a water quality analysis in a bioretention constructed at the Technology Center of the Federal University of Alagoas (CTEC / UFAL), with emphasis on the efficiency of removal of pollutants (COD, BOD5,20 , TSS, E coli, P, Ammonia, NO3, Cr, Pb, Zn, Ni, Cu and oils and greases). For this, analyzes were carried out on the launching of three types of urban drainage water, the drainage in a roof, a gutter and a stream. A methodology for collecting and launching the last two effluents had to be developed. During the monitoring of rainy events, the formation of a superficial water level was verified. Studies with infiltometer and level sensor data resulted in surface infiltration rates from 70mm/h to 179mm/h. Regarding the results of the roof waters, it was noticed flaws in the design of the procedure for collecting this type of effluent. The effect of the first flush and the contribution of adjacent soil water was not considered, depriving the incoming water in the bioretention. The results of the releases of other effluents were quite satisfactory. With the exception of some values of TSS, there was good removal of pollutants, especially the reductions of total phosphorus (72.6 - 76.5%), ammonia-N (68.0 - 74, 8%) and heavy metals (71.4 - 85.7%). Thus, the bioretention under study showed good performance in the retention of pollutants.