Estudo do comportamento mecânico e hídrico do uso do lodo de estação de tratamento de água em misturas com solo argiloso laterítico

Abstract

The waters coming from the springs are extremely important for the supply of the population. However, the residue that accumulates in the sedimentation process, called water treatment station sludge (WTSS), needs an adequate disposal. The main objective of this work is to evaluate the mechanical and hydric behavior of the use of water treatment station sludge in mixtures with lateritic clay soil, for application in landfill layers. The methodology applied in this study consisted of physical and mechanical characterization tests, chemical analysis, obtaining the characteristic curves of the materials, permeability test, mechanical tests of resistance to simple compression, direct shear and triaxial compression. For this, in this research, mixtures were evaluated with partial replacement of soil by WTSS in the proportions of 15%, 30% and 50%. Regarding the classification of materials, it was found that the soil is clayey and that as the substitution of the soil for WTSS increases, there is a reduction in the fractions of silt and clay besides an increase in the sandy fraction. In the MCT classification, the soil and the mixtures of soil + WTSS showed behavior of lateritic materials. The chemical characterization indicated the predominance of clay mineral kaolinite, in all studied materials. In the permeability test, the most impermeable material was the mixture 85% soil + 15% WTSS, with k equal to 7.82E-10 m/s. The resistance to simple compression of soil + WTSS mixtures showed improvement compared to soil, with better performance presented by the mixture 70% soil + 30% WTSS, with resistance 28.73% higher than the soil. Regarding to shear resistance, the friction angle increased as the percentage of WTSS in the soil increased, thus reducing the cohesion of materials. The soil showed higher effective cohesion value (27.69 kPa) and lower effective friction angle (24.06°), while the 50% soil + 50% WTSS mixture showed better performance in friction resistance (42.03°) and worse performance in cohesion (16.30 kPa). From soil to mixture 50% soil + 50% WTSS there was a reduction in effective cohesion of 41.13% and an increase in the effective friction angle of 74.68%. In general terms, the mixture composed of 85% soil + 15% WTSS was defined as the best for application in base layers and landfill cover. However, it is noteworthy that the use of mixtures, especially 50% soil + 50% WTSS, in daily layers of landfills would be an environmentally beneficial alternative. These applications would bring advantages in the destination of the waste and reduction of consumption of natural resources.