Effects of 1,4-dioxane and bisphenol A on the hydraulic barrier performance of clay bottom liners for waste containment facilities

Abstract The bentonite and ocean-floor clay used in hydraulic barriers for on-land and ocean waste disposal sites, respectively, act as the last defense against environmental pollution, and therefore must have high chemical resistivity and long-term stability. The primary factors that determine the hydraulic conductivity of bentonite and ocean-floor clay are the polarity and functional groups of their organic compounds as well as their concentration and hydration characteristics in solution. However, it is not known which of the organic compounds reduce the hydraulic barrier performance of clay liners, and the extent of degradation has not been quantified. Recently, high concentrations of 1,4-dioxane and bisphenol A have been detected in some waste leachates. Although these low-polarity compounds hinder the hydration reaction of clay minerals and increase the hydraulic conductivity of clay liners, the magnitude of their impact in the limited concentrations found in leachates remains unclear. In this study, long-term hydraulic conductivity tests are conducted on a bentonite liner and ocean-floor clay samples, where the permeation liquid contains 1,4-dioxane or bisphenol A. The hydraulic barrier performance is evaluated based on the hydraulic conductivity and the distribution coefficient.