Aplicação de filtros contendo biossorventes no tratamento de um efluente de telhado verde extensivo

Abstract

Green roofs (GR) are solutions that contribute to the control of rainwater runoff in urban areas, alleviating the demand for new rainwater drainage works, in addition to improving thermal and acoustic comfort. However, there is little research related to the quality of water drained from green roofs, especially in Brazil. In this sense, this research aims to evaluate the quality of the water drained from an extensive green roof, as well as the treatment through filters with different compositions, to meet the legal requirements for different uses. The study consisted of two phases, the first of which the water drained from the green roof passed through four filters in parallel, the first consisting of sand, gravel, peanut shell (Arachishypogaea L.) used as an adsorbent, and moringa seeds (Moringa Oleifera), these used as a natural coagulant. In the second stage, the drained water passed through the filters in series, resulting in only one sample with the addition of sodium carbonate, used as a pH corrector. For the qualitative analysis of drained water (raw) and water after treatment, physical (turbidity, color, electrical conductivity, solids and temperature), chemical (pH, phosphate, nitrate, nitrite, chloride and sulfates) and microbiological parameters were analyzed (total coliforms and E. coli), in force for drinking or non-drinking use of water. The results showed that GR acted as a source of color, turbidity, solids, electrical conductivity, total coliforms, E. coli and nitrite However, the continuous use of filters, together with pH correction and water disinfection, improved some parameters such as color, solids, pH and nitrite, not detecting the presence of microorganisms. Comparing the results found with the current legislation on water potability, it was observed that the water after the two stages of treatment presented characteristics for non-potable uses, according to ABNT NBR 15527/2019. Regarding the efficiency of the treatments used, the second phase showed an efficiency of 98.3% for color, 98.2% for solids and 100% for total coliforms and E. coli, when compared to raw water. Therefore, for a better quality of drained water and efficiency in the use of filters after GR, long-term studies are suggested regarding the configuration of filters and the use of different biosorbents.