The concept of a sorption chemical barrier for improving effectiveness of landfill liners

In this work, we apply the concept of a “sorption chemical barrier”, as a means of improving landfill liner effectiveness. The sorption barrier is formed by addition of the organoclay hexadecyltrimethylammoniummontmorillonite (HDTMA-montmorillonite) to a fine sand-bentonite liner. Using previously published experimental data and mathematical model simulations, we demonstrate that such a liner retards significantly the transport of landfill leachate components, thus, increasing the useful life of the liner by a factor of 5 to 10, for the cases calculated. The superior HDTMA-liner performance is maintained even when the sorption extent is significantly decreased, as in the case of leachate containing methanol, a cosolvent miscible with water, found in some industrial and hazardous waste sites. The increase of the useful life of the liner results in smaller liner thickness, required to provide equivalent protection, from the point of view of contaminant transport, as compared to the liner containing no organoclay. Clay liner design based on hydraulic conductivity alone neglects the early breakthrough due to hydrodynamic dispersion and, therefore, is not a conservative one.