Numerical study on performance of anti-seepage liner of landfills

Anti-seepage liner plays an important role in modern landfills as the main structure preventing the landfill leachate from polluting environment. Four typical liner structures frequently used in Chinese landfills are analyzed, and three indexes, including leakage rate, mass flux and sorption capacity, are employed to evaluate the performance of liners. Cadmium and benzene are chosen as the typical inorganic and organic pollutants in leachate. The defects of geomembrane are the main pathway of inorganic pollutants, and the results show that performance of single CCL liner is much worse than that of the composite liner due to the excellent obstruction ability of geomembrane. The performances of GM+CCL composite liner and the GM+GCL composite liner are close with a low leachate head, but the GM+GCL composite perform better when the leachate head reaches a high value (eg. 10 m). As to organic pollutant, the leakage through the geomembrane defects and the diffusion through the geomembrane itself are both considered. The results show that the mass flux of benzene at the base of liner is 1~5 magnitude higher than that of Cadmium, and the GM+GCL composite liner provides a minimum defense to the organic pollutant due to its lowest thickness. The evaluating indexes using here are proved to be able to provide reasonable and scientific assess to the large-scale and long-term performances of the landfill liner. The proposed methods and results can contribute to a better design or refining of landfill liner.