Long-term performance of polyethylene geomembranes to contain brine

Abstract

The degradation of five fortified polyethylene geomembranes (three HDPE, one LLDPE, and one blended) with high initial properties compared to minimum requirements in GRI-GM13 is investigated when immersed in brine at three concentrations (100%, 50%, and 10% brine) and deionized water at temperatures ranging from 25 to 95°C for 8 years. The performance of the geomembranes in different incubation fluids is compared to explore the effect of salt concentration on the durability of geomembranes. The results indicate that the high initial properties of a GMB may not be indicative of its long-term performance due to the effect of other factors like GMB resin, stabilizers, thickness, exposure conditions, and manufacturing process on GMB degradation. Increasing salt concentration decreases the rate of antioxidant depletion, with a depletion rate in 10% brine 1.5 times faster than that in 100% brine. Thus, any assessment of the likely service life of a polyethylene geomembrane in a brine pond with variable salt concentration requires investigating their performance over the expected range of brine concentrations. Temperature and choice of geomembrane (especially antioxidant package) are shown to have a significant (e.g., by a factor of 4 at 55°C in brine) effect on liner longevity.