An analytical solution to contaminant transport through composite liners with geomembrane defects

To investigate the performance of landfill composite liner system, a one-dimensional model was developed for solute transport through composite liners containing geomembrane defects. An analytical solution to the model was obtained by the method of Laplace transformation. The results obtained by the presented solution agree well with those obtained by the numerical method. Results show that leachate head and construction quality of geomembrane (GM) have significant influences on the performance of the composite liners for heavy metal ions. The breakthrough time of lead decreases from 50 a to 19 a when the leachate head increases from 0.3 m to 10 m. It is also indicated that the contaminant mass flux of volatile organic compounds (VOCs) induced by leakage can not be neglected in case of poor construction quality of the landfill barrier system. It is shown that diffusion coefficient and partition coefficient of GM have great influences on solute transport through composite liners for VOCs. The breakthrough time of heavy metal ions will be greatly overestimated if the effects of diffusion and adsorption of clay and geosynthetic clay liner (GCL) are neglected. The composite liner consisting of a geomembrane and a GCL provides a poor barrier for VOCs. The presented analytical solution is relatively simple to apply and can be used for preliminary design of composite liners, evaluating experimental results, and verifying more complex numerical models.