Tratamento de efluentes de lavanderia pela técnica de eletrocoagulação-flotação visando o reuso.

Abstract

The inadequate release of effluents into the environment, such as laundry greywater, deteriorates water resources, reflecting on the scarcity of good quality water. Allied to this, extreme weather events and the increase in demand for water have helped in the problems of water scarcity. Such facts have shown the importance of using effluent treatment techniques aimed at its reuse. In this scenario, electrocoagulation-flotation (ECF) is an efficient treatment technique and has demonstrated the potential to attribute good quality to treated wastewater. Thus, the objective of this study was to determine the ideal condition for the treatment of laundry effluents using the ECF technique and to enable reuse. Raw laundry effluent samples were collected in a domestic laundry. The ECF system used consisted of a cylindrical acrylic reactor with 8 aluminum electrodes (29 cm high, 8 cm wide and 0.05 cm thick), with a distance of 0.3 cm between them and operated with a flow of 0.8 L min-1, connected to a direct current power supply and a helical tubular flocculator. To determine the ideal treatment condition, an experimental design of the central rotational composite design (CRCD) 2² was carried out, with the independent variables initial pH and aluminum concentration, generating response surfaces for the variables color, turbidity, electrical conductivity, pH, total coliforms, sludge and total suspended solids (TSS). From the analysis of the generated response surfaces, new tests were performed. Based on the results obtained, it was possible to verify that the dose of 50.86 mg L-1 of aluminum and pH 4 is the ideal condition for the treatment of laundry effluents by ECF, making the parameters final pH, conductivity, TSS and coliforms thermotolerants according to the provisions of the analyzed reuse standards, US-EPA (2012) and ABNT NBR 16783 (2019). The turbidity parameter was included only in ABNT NBR 16783 (2019) and in US-EPA (2012) for restricted use. Although most parameters were within the analyzed standards, the Biochemical Oxygen Demand (BOD) was above the allowed limits, requiring a complementary treatment step to remove higher levels of this parameter. Thus, it was possible to conclude that the ECF system is efficient in the treatment of laundry effluents, however, only with the insertion of a complementary treatment step, such as the use of a filtration unit, this effluent can be reused.