A comprehensive study on numerical analysis of contaminant migration process in compacted clay liner and underlying aquifer for MSW landfill

Abstract

For the study of MSW landfills in which the lining system is composed of a compacted clay liner (CCL), a two-layer strata model is presented to reproduce the system which consists of a CCL and an underlying aquifer. Considering all types of mechanisms including advection, hydrodynamic dispersion and sorption of soil skeleton, one-dimensional differential equation is formulated for describing the migration behaviour of contaminant in the CCL and aquifer. Together with the actual initial and boundary conditions, the resulting initial boundary value issue is numerically solved by various effective procedures. Based on abundant numerical computations by varying various relevant parameters, the effects of the production modes of contaminant source, hydraulic conductivity and dispersion as well as various sorption behaviours of the CCL, the equilibrium and linear sorption of the aquifer as well as biochemical degradation on the migration behaviour of contaminants in both the CCL and aquifer are systematically examined. It is shown that an independent mechanism in addition to hydrodynamic dispersion and advection, the sorption of soil skeleton plays a much important role in controlling the migration behaviour of contaminants. The sorption model and its parameters should be carefully chosen in the numerical analysis of contaminants migration and design of MSW landfill. Moreover, both coefficients of hydraulic conductivity and dispersion of the CCL should be duly determined according to the actual condition. Compared with the sorption effect of the CCL, the influence of sorption of aquifer on the migration behaviour of contaminants can be overlooked.