Equivalent Transport Parameters for Volatile Organic Compounds in Coextruded Geomembrane–Containing Ethylene-Vinyl Alcohol

A method to estimate the equivalent diffusion coefficient and partition coefficient of a coextruded ethylene-vinyl alcohol (EVOH) geomembrane (GM) is presented. The method is based on the weighted harmonic mean of diffusion coefficients of each layer and the partition coefficient of the outer layers. The method was evaluated using experimental data obtained with five volatile organic compounds (VOCs) typically found in landfill leachate [methylene chloride (MC), methyl tertiary butyl ether (MTBE), trichloroethylene (TCE), toluene (TOL), and chlorobenzene (CB)] and a coextruded GM composed of outer layers of low-density polyethylene (LLDPE) or high-density polyethylene (HDPE), an adhesive tie layer (maleic anhydride), and a core of EVOH. Equivalent diffusion coefficients computed with the recommended equation were found to be no different statistically from equivalent diffusion coefficients measured using a modified double-compartment apparatus. VOC transport through a composite liner using a coextruded EVOH GM was predicted using a finite-difference model with the equivalent transport parameters as input. Good agreement was obtained between predictions from the model and measured concentrations from a column test simulating a composite liner.