Effect of Synthetic Leachate on Volume Change Behavior of Compacted Clay Liners: Fid-Bau Portal

Effect of Synthetic Leachate on Volume Change Behavior of Compacted Clay Liners

Shanmuga Priya, R. / Thyagaraj, T.

Compacted clay liners (CCLs) are widely used as hydraulic barriers below the leachate collection systems of municipal solid waste (MSW) landfills as they reduce the rate of contaminant migration by advection owing to their low hydraulic conductivity and molecular diffusion. The main requirement of liner materials is to minimize the pollutant migration into the soil and groundwater. Apart from the low hydraulic conductivity, the compacted liners should possess enough shear strength to withstand the load of waste over them and volume stability for preventing desiccation cracking. Field studies have shown that compacted clay liners placed at shallow depths undergo swell–shrink movements due to seasonal moisture fluctuations. The swell–shrink volume change in turn affects the hydraulic conductivity of CCLs as complete healing of desiccation cracks does not occur instantaneously. Also, the concentration of leachate has a great impact on the hydraulic conductivity of CCLs. However, most of the literature was focused on bringing out the physicochemical effects on CCLs using inorganic solutions such as 0.1–0.4 M NaCl solutions. The characteristics of the chemically aggressive municipal landfill leachate cannot be demonstrated effectively using distilled water or inorganic simple solutions. To yield a reasonable worst-case scenario, actual leachates obtained from three different MSW dumpsites are characterized. Then, the synthetic leachates (SLs) were prepared based on the maximum concentrations of each element obtained from the actual leachates collected from the MSW dumpsites. In this study, SLs are prepared and used as inundating solutions to understand the volumetric behavior of CCLs.