Effect of hazardous industrial solid waste landfill leachate on the geotechnical properties of clay

Abstract

One of Egypt’s major environmental issues is the disposal of solid waste. Natural clay is commonly employed to produce impermeable liners in solid waste landfills. Leachate from the waste mass can significantly affect the geotechnical properties of clay liners. In this study, the impact of hazardous industrial solid waste leachate (HISWL) on the geotechnical properties of clayey soil was investigated by using a natural clay artificially mixed with HISWL at various concentrations (0%, 25%, 50%, 75%, and 100%) to assess the potential of utilizing this clay as a barrier to line the hazardous industrial solid waste landfill. Changes in the clay structure were interpreted by detailed analyses using X-ray diffraction and scanning electron microscopy. The results revealed that there was a 10.53% percentage decrease (PD) in the plasticity index (IP) of 100% HISWL-contaminated clay. The mixing of natural clay with 75% and 100% HISWL reduced the optimum moisture content (OMC) with a PD of 12% and 20%, respectively. The maximum dry density (MDD) of 25% HISWL-contaminated clay remained unaffected, whereas there was a slight percentage increase (PI) of 3.74% in the MDD of 100% HISWL-contaminated clay. The permeability coefficient (k) of 100% HISWL-contaminated clay significantly decreased with a PD of 78.31%. The angle of internal friction (φ) significantly decreased from 23.7° (for the natural clay samples) to 16.3° (for the 100% HISWL-contaminated samples) with a PD of 31.22%. The cohesion decreased from 33 to 22 kN/m2 at 25% HISWL concentration with a PD of 33.33%. The compression index (CC) of the clay decreased at different concentrations of HISWL. This study recommends utilizing the used clay as a liner in the event that a new hazardous waste landfill is constructed in Egypt, due to its availability and effectiveness.