Simplified method for determination of thickness of composite liners based on contaminant breakthrough time

Based on the statistic analysis of the measured concentrations of leachate pollutants found in the six landfill sites in China and the contaminant limit concentration specified in the drinking water standard, the breakthrough standard values for the indicative contamiant in the leachate in the typical and extreme situations are determined to be 0.1 and 0.01, respectively. Based on the analytical solution of contaminant transport through a composite liner consisting of a geomembrane (GMB) and a compacted clay liner (CCL), the simplified formula for determination of the thickness of the composite liner is obtained for the indicative inorganic and organic contaminants by using the numerical fitting method. The simplified method is used to design the composite liner system at the Tianziling landfill site in Hangzhou. When considering the lead (Pb) as the index contaminant, the breakthrough time will be longer than 50 years in the case with the thickness of CCL larger than 0.6 m.