Hydraulic and chemical evolution of GCLs during filter press and oedopermeametric tests performed with real leachate

Abstract

The solid-waste decomposition inside a municipal solid-waste (MSW) landfill may be enhanced by liquid addition in order to reach landfill stabilization in a reduced period of time as compared to dry-tomb landfills. This liquid addition provides an increased leachate volume and its specific chemical composition leads to fear a degradation of the hydraulic properties of the bottom liner system, especially the mineral part. In this study, the impact of four fluids on the chemical and hydraulic properties of three geosynthetic clay liners (GCLs) currently used in landfill bottom liner systems is evaluated using swelling tests, filter press tests and oedopermeameter tests. Each permeability test is associated to chemical analysis of the fluids before and after contact with the bentonites. The four fluids are two real leachates, a sewage 2 / 42 slurry and a leachate from a green waste repository. The three GCLs contain either natural sodium bentonite or sodium activated calcium bentonite. Filter press results and swell index tests reveal a larger impact on the permittivity of the bentonite of leachates as compared to the other fluids. Oedopermeameter tests lasted one year; they show a variable impact, either negative or positive, of the real leachate on the hydraulic conductivity of the GCLs. Specific conditions, such as pre-hydration, limit the impact of leachate on the hydraulic conductivity. Whatever the method used to determine the permittivity of bentonite or of the GCL, the natural sodium bentonite is less impacted by the fluids than the sodium activated calcium bentonites.

State-Of-The-Art Review of Geosynthetic Clay Liners

“…The common method adopted is the "compatibility test", in which the sample is permeated with a leachate similar to that anticipated. Factors influencing the hydraulic conductivity of GCLs have been studied through extensive compatibility tests [25,53,55,[59][60][61][62][63][64][65]. Generally, the hydraulic conductivity can be affected by both internal and external causes.…”

Impact of Uniaxial Mechanical Perturbation on Structural Properties and Smectite Porosity Features: Ion Exchanger Efficiency and Adsorption Performance Fate

“…To evaluate the consistency of these membranes, it is important to examine their chemical compatibility with the different fluids or the leachate to which they are subjected [22]. Based on the fine particle size, the homogeneous micropores and the high surface charges, the low hydraulic conductivity, the high adsorption capacity, and the low cost compared with geosynthetic clay (GC), natural bentonites are most prized in this context [23][24][25][26][27][28][29]. Indeed, [30] studied the shear strength of compacted clays as affected by the mineral content and wet-dry cycles and demonstrated that the cohesion and frictional strength properties were determined and linked to the proportion of clay minerals and the number of wetting and drying cycles.…”

“…However, compacted clays present problems with cracking and/ or desiccation, especially those containing an appreciable amount of bentonite [34][35][36]. Numerous studies have shown that compacted clays undergo large physicochemical properties modifications when exposed to a cycle of swelling and/or desiccation-wetting, which constitutes a surrounding variable environmental constraint [28][29][30][31][32][33][34][35][36][37][38][39]. Montmorillonite fraction, which is a dioctahedral species of the smectite mineral group, can constitute up to 95% of bentonite.…”

Effect of Type of Leachate on Self-Healing Capacity of Geosynthetic Clay Liner

“…There are numerous literatures which investigated the effect of types of liquid on hydraulic conductivity of GCL or bentonite 4,[6][7][8][9][10][11][12] , but the effect of types of liquid on self-healing capacity of GCL is not well investigated. Further, there are two types of GCLs used in engineering practice, namely geomembrane supported GCL (GM-GCL) and geotextile encased GCL (GT-GCL).…”