Analysis of 1D Contaminant Migration through Saturated Soil Media Underlying Aquifer Using FDM

Abstract

Finite-difference method (FDM) has been adapted herein to solve a one-dimensional (1D) contaminant transport model to predict contaminant migration through soil in waste landfill underlying an aquifer. Providing an effective engineered barrier, which will separate the waste from groundwater, can minimize the potential contamination in the groundwater system. In this paper, a solution technique has been developed using FDM for the analysis of 1D contaminant transport in a layer of finite thickness. The present study considers the effects of advection, dispersion/diffusion, geochemical reactions, and decay in a single model with a finite quantity of pollutant in the landfill and transport of contaminants toward groundwater beneath the clay deposit/liner. The computer program CONTAMINATE-1D-FM has been developed using the proposed solution technique to analyze the contaminant migration. The short-term and long-term effects of different factors influencing groundwater contamination have been presented in this paper. The values of the relevant parameters used by previous investigators have been adapted in the solution technique presented herein for prediction of contaminant migration. The effects of Péclet number and Courant number criteria have been considered to select appropriate time step and spatial size of the finite-difference grid to avoid oscillation and numerical dispersion. The proposed solution technique for contaminant transport with finite mass has been validated with a published analytical solution. The design of clay liner and the impact of important parameters on a groundwater system have been illustrated to facilitate field engineers.