Modelling of Leachate Leakage and Contaminant Migration Through Municipal Solid Waste Landfill Liner Systems

Low permeability liners are generally used at the bottom of modern engineered landfills for minimizing leachate leaking and contaminant migrating from landfills into the surrounding environment (e.g., groundwater and surface water). For a single liner system, there are three commonly used design options: (1) a compacted clay liner (CCL), (2) a high density polyethylene (HDPE) geomembrane (GMB) on a CCL, (3) a HDPE GMB on a geosynthetic clay liner (GCL) overlying a CCL. This paper numerically examines the leakage of leachate and the migration of contaminant through all three liner systems provided by the Chinese national standard using a finite element method (FEM) computer program. The results show that the calculated leachate leakages from the FEM generally agree well with those from the Rowe’s analytical solution, and the amount of leakage rates through the liner is dependent on the type of the liner. The calculated contaminant concentrations in aquifer indicated that the time for contaminant to reach the peak value is quite different among the three liners. The paper demonstrates that the three design options for a single liner system in the Chinese national standard have quite different performance in terms of minimizing groundwater contamination below the MSW landfill liner.