Formulação de tinta para piso com resíduos de ETE no contexto da economia circular

Abstract

This work evaluated the reuse of filter press-dewatered sludge cake from an effluent treatment plant (ETP) in the formulation of water-based floor paint, from the perspective of circular economy and industrial waste valorization. Currently, residues generated in industrial processes often require appropriate disposal, which may represent operational costs and environmental impacts associated with their management. As an alternative for reusing this material, this study proposed the use of ETP sludge cake as a partial or total substitute for the conventional mineral filler, in slurry form, used in paint formulations. Initially, the sludge cake was characterized regarding its physical and microbiological properties and subsequently used in its in natura form for slurry preparation, without additional drying, grinding or sieving steps. Microbiological and physicochemical analyses of the slurry were carried out, including determination of pH, density, solids content, viscosity, coverage and stability, in addition to evaluating the effectiveness of the microbiological control employed in the formulation. Subsequently, floor paint formulations containing different proportions of sludge-based slurry and conventional mineral slurry were developed and subjected to pH, density, viscosity, solids content, gloss, contrast ratio, stability, abrasion, substrate application and visual evaluation tests. The results demonstrated that the sludge cake presented high initial microbiological contamination; however, the preservative system adopted proved effective in controlling microbial growth. The developed slurry showed characteristics compatible with part of the industrial reference parameters, allowing its incorporation into paint formulations. Formulations containing partial replacement of the conventional mineral filler showed behavior closer to the reference product, whereas total replacement indicated the need for additional formulation adjustments. Therefore, it was concluded that the reuse of sludge cake from the effluent treatment plant presents technical, environmental, operational and economic potential for application in floor paints, especially under conditions of partial replacement of the conventional mineral filler. In addition, the use of the residue without additional drying, grinding or sieving steps, combined with the reduction in conventional mineral filler consumption and the valorization of an industrial waste, indicates potential economic benefits associated with process simplification and waste management, representing an estimated cost reduction of approximately R$ 1 million annually.