Performance of GCLs in high salinity impoundment applications

Abstract

The interface transmissivity (θ) and hydraulic conductivity (k) are measured for two geosynthetic clay liners (GCLs), one with polymer-enhanced bentonite, when hydrated and permeated with saline (brine) solutions at three different concentrations and Reverse Osmosis (RO) water. Two interface transmissivity values are reported, the 2-week (θ2-week) and the steady-state (θsteady-state) interface transmissivity. For saline solution (brine) permeation, the 2-week interface transmissivity (θ2-week) is one to two orders of magnitude higher than the steady-state values. In addition, the steady-state interface transmissivity (θsteady-state) with respect to brine is almost an order of magnitude higher than that for RO water permeation. Geomembrane (GMB) stiffness has a limited effect on interface transmissivity at 150 kPa, whereas at 10 kPa the interface transmissivity decreases as the GMB stiffness decreases. GMB texture has only a small effect on interface transmissivity at different stress levels. Water prehydration reduces the effect of brine permeation on interface transmissivity and hydraulic conductivity, especially at 150 kPa. Transmissivity tends to increase as the salt concentration increases but the effect was significant at all concentrations considered (440 to 4400 mmol/l). While the effect of bentonite enhancement on interface transmissivity is unclear, the hydraulic conductivity (k) is generally lower for enhanced bentonite.