Avaliação da viabilidade de reúso da água cinza tratada em filtro biológico

Abstract

Sustainable practices such as water reuse preserve water resources. Thus, the use of appropriate technologies, derived from centralized or decentralized systems for the treatment of wastewater, is a basic strategy for solving the problems of universal water shortage. In this perspective, this work aims to make a technology, in laboratory scale, for wastewater treatment, being a downflow biological filter having medium in four different layers, comprising sawdust, sand, activated carbon and crushed stone. The work was carried out in the Sanitation Laboratory of the Federal University of Alagoas, UFAL-Campus Sertão and treated gray water came from the campus itself, collected from the kitchen sink of the canteen. The system was monitored for 45 days, and after the first 15 days the inoculation was done. In addition, the viability of treated gray water for non-potable reuse was determined in some activities, in view of normative recommendations. The activities in which water reuse was applied were divided into classes and the parameters under analysis were BOD, COD and E. coli. The raw gray water presented high concentrations of organic matter, reaching 210 mg/L of COD and 117 mg/L of BOD, and the presence of fecal indicator, E. coli, was 3357 NMP/100 mL, evidencing the need for treatment before reuse. As for the average reduction in the parameters analyzed, there was a decrease in COD from 126 mg/L ± 56 to 55 mg/L ± 24, BOD from 70 mg/L ± 31 to 30 mg/L ± 13 and E. coli from 936 NMP/100mL for 45 NMP/ 100mL in the final effluent, achieving an average removal efficiency of 56%, 56%, 95.0%, respectively. In these terms, it was found that this gray water can be used, in terms of COD for class 4 and for the BOD parameter, for class 2. The E. coli parameter serves the various activities for the reuse of water that are in the standards, except for class 1 of the FIESP manual, as it requires no detection of E. coli.