LIMA, A. N.; http://lattes.cnpq.br/6334162876759362; LIMA, Alisson do Nascimento.
Abstract:
The base liners of sanitary landfills are of fundamental importance in the leachate containment
process, this liquid fluid is the result of the degradation of landfill waste. Soil-bentonite liners
are widely used and studied for the influence of the percolating fluid and the effects on its
functionality regarding the vertical permeability of the layer. In this sense, the present study
aimed to determine the hydraulic and microstructural behavior of soil-bentonite mixtures used
in a sanitary landfill liner with water percolation and leachate. So, from a factorial design of the
Central Composite Design (CCD) type, the variables of moisture content of compaction of the
samples were evaluated at levels of 7, 11 and 15%, and of bentonite, at levels of 5, 15 and 25%,
added to the natural soil. The fluids used on permeability tests were distilled water and leachate,
generated at the Sanitary Landfill in Campina Grande-PB (SLCG). The leachate was subjected
in the laboratory to physical-chemical, viscosity, and density characterization. The samples
were tested in the Triflex-2 flexible wall permeameter, with methodologies suitable for the
percolation of each fluid, with saturation using the percolating (leachate), obtaining the vertical
permeability of the samples. In the results, it was observed that all samples present adequate
water permeability to the standards for use in sanitary landfill liners. As for leachate
permeability, it is possible to observe that, compared to water, the results are higher by up to
two orders of magnitude. These experimental results showed the permeability of the soilbentonite
mixtures, which is a behavior controlled by the liquid in the pores of the soil structure.
Thus, these results of greater permeability were attributed to the increase in the ionic strength
of the leached liquid in the voids of the soil, that is, to contaminating compounds and heavy
metals in the leachate. Thus, these contaminants are attributed to the reduction of the Diffuse
Double Layer (DDL), expansive potential, and flocculation of the clay which explains the
different permeabilities depending on the fluid. Optical Microscopy (OM) and Scanning
Electron Microscopy (SEM) images validated this analysis, showing a higher percentage of
pores in soil samples percolated with leachate. Therefore, this study concludes that there is a
change in the hydraulic and microstructural behavior of the bentonite-soil liners, showing the
need to evaluate construction methodologies for these layers, with more adequate criteria than
water permeability.