Comparison of the Performance of Contaminant Transport Barriers Using Laboratory Models

By performing a series of laboratory tests، different landfill barrier layers alternatives (liners) were investigated. The selected liner materials were tested for molecular diffusive transport and the diffusion coefficient of chloride ion was determined. Three liner alternatives comprising of clay over silt، geosynthetic clay liner (GCL) over silt، and GCL over clay over silt، were evaluated using laboratory models and under chloride ion advective-diffusive transport. Using the chloride diffusion coefficients obtained in the laboratory and the models downward flow velocity، the observed advective-diffusive transport of chloride ion was evaluated against the predicted transport by theoretical model in three landfill liner alternatives. They were then compared as an effective and suitable liner to decrease contaminant transport in the landfill. The comparison of observed and predicted concentrations showed that there is a good agreement between the two and the theoretical model is capable to predict the behavior of the experimental models. The comparison of the observed concentrations in the simulated ground water underneath the modeled liners showed that for the prevailed test conditions in this study، all three selected liners are good barriers in terms of controlling contaminant transport and there is no significant difference between them، and all possess similar performance.