Evaluation of the various landfill liner systems requires the contaminant transport modeling through selected liner. Normally clay soils alone or bentonite amended with sand are widely used as bottom liner. Bentonite is used due to its high adsorption capacity and sand is used to impart the required volume stability and strength. The performance of the liner has to be assessed for the breakthrough times under different hydrological regime knowing the hydraulic conductivity of the compacted liner and sorption capacity. The data available on sorption capacity of the liner for copper and iron is used to select the appropriate sand bentonite mixture combination. It was found that a mixture of 20% bentonite and 80% sand possess better sorption capacity for copper. The hydraulic conductivity of this mixture has been determined by laboratory testing. The breakthrough curves, under different hydraulic gradients for the compacted mixtures and for the diffusion coefficient of copper, are obtained through the use of POLLUTEv7 software for a liner thickness of 1m. To promote the waste materials for liner construction fly ash is often used as material. To enable comparison and to improve the stability of the 10% fly ash containing 90% sand is used. It was found that fly ash sand mixture possesses better sorption capacity for iron. But the hydraulic conductivity of the mixture was high and the break through times as modeled was very small. To reduce the hydraulic conductivity 5% of bentonite is incorporated to sand fly ash mixture. The breakthrough times as modeled have improved considerably.
, Naik, M., and , “Modeling of the Cu and Fe transport in sand bentonoite and sand-fly ash mixtures”, International Journal of Earth Sciences and Engineering. , vol. 7, no. 1, pp. 325-330, 2014.