Implications of single and double liners on the impact of PFOA in landfills on an underlying aquifer

Abstract

The transport of perfluorooctanoic acid (PFOA) through the base of a municipal solid waste landfill lined by a single or double composite liner system underlain by an aquifer is examined. Experiments conducted to obtain permeation coefficients for PFOA (and other PFAS) through HDPE and a GCL at different stress levels are described and the results presented. Experimentally derived interface transmissivity and GCL hydraulic conductivity permeated by a PFAS solution are presented. The experimentally derived parameters for PFOA are then used together with finite element software to model diffusive and diffusive-advective transport of PFOA through holed wrinkles from a landfill. The peak concentrations of PFOA in the modelled aquifer are reported and compared to the maximum allowable drinking water regulations for PFOA in different jurisdictions. A sensitivity analysis is performed to assess the effect of different parameters on the degree of contamination of the aquifer. With no holes in the geomembrane (pure diffusive transport), all regulatory limits are met for both single and double-lined barrier systems. The amount of leakage through holed wrinkles required for PFOA to exceed regulatory limits varies depending on the initial concentration of PFOA and jurisdictional allowable limits. Most results showed that the single composite liner barrier system examined is unlikely to be sufficient to contain PFOA to an acceptable level. The double liner system is more likely to meet regulatory requirements if most of the leakage through the primary is collected. • Estimates the permeation coefficients of PFOS, PFOA, PFBS, 6:2FTS and GenX through HDPE liners at 23 °C, 35 °C and 50 °C. • Correlates the peak concentration in the aquifer beneath a landfill and the initial concentration in the landfill leachate. • Correlates the peak concentration in the aquifer and the leakage passing through the liner system and the flow in the aquifer. • Shows the effectiveness of single and double liner systems in containing PFOA and compares the results with regulatory limits. • Models different double liner barrier system designs and compares their effectiveness at mitigating PFOA transport.

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