Attenuation potency of mineral liner to cationic migration

Abstract

In waste containment, it has become imperative that regimes of soil, surface and groundwater reserves are duly protected from contamination from leachate generation and migration in landfills. However, in developing countries such as South Africa, the construction of engineered facilities may be costly and the prevention of contaminants may become significantly reliant on the geology of the waste disposal site. More so, membranes forming part of geocomposite systems for waste containment may fail at any point in time leading to consequential environmental and human health impacts. Hence this study conducted series of laboratory tests of a failed membrane in a geocomposite liner under leachate migration through a circular defect using a bespoke hybrid column permeameter device. A zeolitic mineral liner; 24 mm thick, polythene plastic (PP); 2 mm thick having a 5 mm centralized inflicted puncture were used to simulate the circular failure in the membrane with a 225 mm thick mineral layer as attenuation strata (AS) making up the experimental setup. The bespoke device of 60 mm diameter was coupled to a hydraulic pressure frame capable of imposing over 800 kPa pressure to the liner. Permeant through the liner system was evaluated in ranges of 0 – 150 kPa. The study measured migration rates for conditions of good and perfect interface contacts. The study found the conditions of good contact to be valid but unachievable for conditions of perfect contact. However, tests results revealed significant reduction in migration rates with increased pressure, p, on the system. This is plausibly due to reduced system transmissivity, θ, and densification of the zeolitic liner. Subsequent to compatibility tests, there was substantial evidence that cation concentrations migrated through the failed membrane-mineral liner. Nonetheless, a fairly reasonable attenuation potency of the zeolitic mineral layer as AS to migrating cations was recorded.