Contaminant transport through landfill composite liners due to geomembrane defects

Although a number of studies have been devoted to the assessment of the leachate flow rate through defects in geomembranes, which are routinely used in conjunction with low-permeability mineral layers for the lining of waste disposal facilities, relatively little attention has been paid to the mechanisms that control the transport of contaminants. A theoretical framework is here presented to model the advective-diffusive transport of inorganic contaminants through defects of uniform width and infinite length (holed wrinkles, defective seams, etc.), whereby imperfect contact conditions between the geomembrane and the underlying mineral layer are considered, and the mass conservation condition is imposed for both the solvent and the solute phases. Closed-form analytical solutions have been derived to assess the contaminant mass flow rate for the cases of pure advection and pure diffusion, with a view to quantifying the error associated with the simplified calculation approaches that are currently adopted for the performance-based design of landfill composite liners.