Effects of Temperature and Leachate Exposure on Hydraulic Performance of Compacted Clay Liners (CCLs) in Landfills

A.A. Aldaeef, M.T. Rayhani

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Geoenvironmental Engineering

ABSTRACT: Temperature and Leachate Exposure on Hydraulic Performance of Compacted Clay Liners (CCLs) in Landfills. A. A. Aldaeef, and M.T. Rayhani Carleton University, Ottawa, Ontario, Canada Department of Civil and Environmental Engineering Œ Carleton University, Ottawa, Ontario, Canada. ABSTRACT An experimental set up was designed to study the effects of Thermo-chemical exposure on hydraulic conductivity of various CCLs, simulating landfill conditions after waste placement. Results showed an increase in hydraulic conductivity of specimens permeated with synthetic leachate at room temperature (22). However, as the leachate exposure proceeded beyond 15 days exposure threshold, hydraulic conductivity significantly decreased to as low as one order of magnitude. This behaviour was attributed to chemical precipitation and pore void clogging along with possible double layer expansion leading to a more dispersed fabric arrangement, which in turn reduced the effective pore volume and the relevant hydraulic conductivity. The rate of hydraulic conductivity reduction due to leachate permeation was slower at higher temperatures when combined thermo-chemical exposure was applied. This was linked to reduction in viscosity of the permeant at higher temperatures which seemed to facilitate the permeant movement throughout the soil matrix and resulted in higher hydraulic conductivity at higher exposure temperature. Moreover, lower bacterial growth was observed at higher temperature which could result in lower clogging potential at higher exposure temperatures. RÉSUMÉ Une expérimental a été conçu pour étudier les effets de l'exposition Thermo -chimique sur la conductivité hydraulique de divers CCL simulant les conditions d'enfouissement des déchets après le placement . Les résultats ont montré augmentation initiale de la conductivité hydraulique de spécimens imprégnés de lixiviat synthétique à température ambiante ( 22 ) . Cependant, comme l'exposition des lixiviats procédé delà du seuil de 15 jours , la conductivité hydraulique nettement diminué à aussi peu que un ordre de grandeur . Ce problème a été attribuée à la précipitation chimique et le colmatage des pores vide en même temps que l'expansion possible de double couche conduisant à un agencement de tissu plus dispersée , qui à son tour réduit le volume effectif des pores et la conductivité hydraulique correspondant. Le taux de réduction de la conductivité hydraulique en raison de lixiviat perméation a été plus lente à des températures plus élevées lorsqu'il est combiné exposition thermo -chimique a été appliquée. Cela a été liée à la réduction de la viscosité du perméat à des températures plus élevées qui semblaient faciliter la circulation de perméation à travers la matrice du sol et ont abouti à la conductivité hydraulique supérieure à la température plus élevée de l'exposition . En outre, la croissance bactérienne inférieure a été observée à plus haute température , qui pourrait se traduire par l'encrassement inférieure à des températures d'exposition élevées 1 INTRODUCTION Earthen barriers are widely used as a part of waste containments in order to minimize their environmental impacts and maximize their hydraulic performance. Municipal solid waste landfills are examples of the most recently used waste containment. Landfills are often equipped with a barrier system that may consist of a layer of Compacted Clay Liner (CCL) or a Geosynthetic Clay Liner (GCL) overlain by a geomembrane (High Density Polyethylene, HDPE). A typical CCL consists of a 0.75-1.0 m thick layer of compacted clay with a hydraulic conductivity of about 1x10-9 m/s. CCLs are normally covered by a layer of leachate collection system or a layer of soil immediately after construction to be isolated from climate effects. This measure is desired to minimize their moisture content fluctuation, which may occur following to wet-dry and/or daily thermal cycle's exposure, thereby, maintain their designated hydraulic performance. However, different exposure conditions would be generated and subjected to the barrier system even after waste placement in landfills. Chemical leachate and elevated temperatures are typically generated on top of the barrier system following to the organic waste biodegradation. These conditions may facilitate the antioxidants depletions from the geomembrane (Rowe and Yu 2010). Geomembrane depletion will result in an immediate contact between the

RÉSUMÉ: ts of Temperature and Leachate Exposure on

Access this article:
Canadian Geotechnical Society members can access to this article, along with all other Canadian Geotechnical Conference proceedings, in the Member Area. Conference proceedings are also available in many libraries.

Cite this article:
A.A. Aldaeef; M.T. Rayhani (2014) Effects of Temperature and Leachate Exposure on Hydraulic Performance of Compacted Clay Liners (CCLs) in Landfills in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper366,author = A.A. Aldaeef; M.T. Rayhani,title = Effects of Temperature and Leachate Exposure on Hydraulic Performance of Compacted Clay Liners (CCLs) in Landfills,year = 2014}