Avaliação da qualidade de água do sistema de aproveitamento de água da chuva instalado no Campus de Belém da Universidade Federal do Pará

Abstract

This research has main objective to analyze the rainwater quality in an experimental unit of rainwater harvesting and treatment (EURHT) with emphasis on the treatment by filtration in two different filters: sand plus activated carbon of açaí seed (mixed) and activated carbon of açaí seed. The research was developed in three steps: 1) installation of the two filters and characterization of the filter composition; 2) rainwater quality monitoring of EURHT, considering the variables: apparent color, turbidity, electrical conductivity, pH, total alkalinity, total coliforms and E.coli, and the investigation of the presence of microorganisms in the tank; 3) evaluation of the costs involved in the implementation of the system, considering two filtration alternatives. The sand had effective diameter of 0.62mm, uniformity coefficient of 1.42 and specific gravity of 2,632 kg/m3. Activated carbon had an effective diameter of 1.8mm, coeficiente uniformity of 0.58, a humidity of 2.10%, and density of 0.358 g/cm3. Activated carbon filter had a flow rate of 0.35 m³/h, higher than the mixed filter (0.20 m³/h), even as the filtration rate was higher (34.26 m³/m2.d) and the Mixed filter of 19.19 m³/m2.d. The roof contributed to rainwater quality degradation, increasing the values of apparent color, turbidity, electrical conductivity and total alkalinity in relation to atmospheric water, which was already expected; The self-cleaning didn’t had a proptious performance, because there was increase in the variables value apparent color, turbidity, total coliforms and E. Coli in relation to water collected after the roof; The tank was the part of system that best contributed to the improvement of rainwater quality, because there was a decrease in the variables value apparent color, turbidity and electrical conductivity in relation to water after self-cleaning; The mixed filter and the activated carbon filter didn’t had a proptious performance, because decrease the water quality arriving from the tank for all variables. The mixed filter get better results than activated carbon filter. The mixed filter was also the best financial alternative in the system. In the tank were found about 7 different microorganisms, between them: zooplankton, algae frustules and fungal spores. EURHT didn’t produce rainwater for drinking purposes, because there were pathogenic microorganisms, besides values of variables above the limit of the ordinance 2914 (BRASIL, 2011), and there is a requirement for disinfection at end of the treatment process.