Performance of HDPE geomembrane liners in landfill applications

Both short-term and long-term performances of high-density polyethylene (HDPE) geomembrane liners used to minimize municipal solid waste (MSW) leachate contaminants migration to groundwater was examined. In the short-term performance investigation, diffusion and sorption tests were performed on a 2.0 mm HDPE geomembrane and on “untreated” and fluorinated 1.5 mm HDPE geomembranes using volatile organic compounds. The results showed that the permeation of organic contaminants was greatly reduced by the surface fluorination.; The evaluation of the long-term performance involved three components. First, a field investigation undertaken involved the exhumation and the evaluation of a 1.5 mm HDPE geomembrane from a leachate lagoon after 14 years of use. The results show that the geomembrane has experienced some degradation, especially samples that had been perpetually exposed to sunlight and weather. The results from diffusion tests indicated very low permeation parameters for organic contaminants. Second, a natural weathering test in which both field-exhumed and new unaged geomembrane samples were exposed to sunlight and weather and the degradation assessed was conducted. The results indicated that, for the pre-aged samples, the antioxidants were completely consumed and the degradation progressed while for the new geomembrane the consumption of antioxidants was not completed. Third, laboratory experiments consisting of accelerating the degradation of the geomembrane by using four elevated temperatures were performed. In this study, 2.0 mm HDPE geomembrane samples were exposed to air, water and reduced synthetic leachate that simulates closely a typical MSW landfill leachate. The results demonstrated the role played by antioxidants in protecting the geomembrane from oxidative degradation and the important catalytic role played by leachate constituents (metals, salts, surfactant etc.) on the depletion of antioxidants.; HDPE geomembranes service life was addressed based on the laboratory-accelerated tests using Arrhenius modelling. The implications on the overall performance of landfill liners are outlined.