Thickness of Compacted Natural Clay Barriers in MSW Landfills

Abstract

Natural clay deposits and compacted clay liners are used as landfill barriers; however, there is no consensus on what an appropriate thickness of the barrier ought to be, due to difficulties encountered while analyzing soil liners. In the present study, an attempt has been made to estimate thickness of clay barriers for landfills for conservative/nonconservative contaminants. The optimum thickness is decided on the basis of the travel time taken by leachate as it moves down through the clay barrier. The one-dimensional (vertical) model is solved numerically by the Green element method and the developed model is first validated for transport of chlorides and dissolved organic carbon through a soil barrier at a landfill site. Later, an analysis is conducted taking a finite mass of the pollutant as the top boundary of the soil barrier and the maximum relative concentration of the contaminant determined, as it moves down. On the basis of these results, knowledge of the total mass of solid waste and the maximum concentration of the solute in the landfill, the minimum thickness of the liner for an equivalent leachate height, and Darcy velocity can be obtained from the design charts developed.