Evaluation of a Landfill Composite Liner System Using Different Contaminants

Landfilling is one of municipal solid waste (MSW) management methods in China. Modern engineered landfills generally have a low-permeability liner system with a geomembrane (GMB) on a geosynthetic clay liner (GCL) and/or compacted clay liner (CCL) overlying an attenuation layer (AL) at the base of landfills to minimize contaminants within landfills migrating into groundwater. This paper develops a numerical model based on the transient contaminant transport equation with dispersion/diffusion, advection, adsorption, and decay. Three different contaminants (i.e., toluene, cadmium, and chloride) are selected to evaluate the performance of a GMB/GCL/CCL/AL composite liner, and contaminant concentrations in the aquifer are compared with the corresponding maximum contaminant levels in drinking water. The results show that the time for each contaminant to reach the peak concentration at the downgradient edge of the landfill in the aquifer is quite different. The paper demonstrates the importance of designing the GMB/GCL/CCL/AL composite liner using not just a particular contaminant but the critical contaminants in landfills.