Tratamento de resíduos sólidos industriais e proposição de padrões para avaliação ambiental do nitrogênio amoniacal em materiais estabilizados por solidificação

Abstract

This study aimed to treat industrial solid wastes red mud (RM), sewage sludge (SS), and sugarcane bagasse ash (SBA) using the stabilization/solidification (S/S) technique and to propose environmental parameters for ammoniacal nitrogen in S/S materials. Cementitious matrices were produced with 15% waste content, Portland cement CPII-Z-32, and sand, and cured for 28 days. The wastes were characterized for total solids, pH, electrical conductivity, and mineralogical composition by X-ray diffraction (XRD). The integrity and durability of the matrices were evaluated through compressive strength, water absorption, and wetting-drying cycle tests, using a one-way experimental design to assess the influence of waste type. Environmental assessment included leaching and solubilization tests, followed by the determination of ammoniacal nitrogen, heavy metals, and chemical oxygen demand (COD). Contaminant immobilization was determined by mass balance and retention efficiency. All treatments met the integrity and durability criteria, with RM showing the best mechanical performance. Analysis of variance confirmed that the type of waste significantly influenced the physical properties of the matrices. Maximum permissible limits for ammoniacal nitrogen were proposed at 20 mg·L-1 in leachate and 1.2 mg·L-1 in solubilized extract, based on current environmental regulations. After treatment, reductions were observed in the concentrations of all evaluated contaminants – ammoniacal nitrogen, aluminum, iron, zinc, manganese, and COD – with effective immobilization of iron, zinc, and manganese. The results indicate that the S/S technique was effective in contaminant immobilization and in ensuring satisfactory physical-mechanical properties of the matrices, enabling the safe reuse of the materials.