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Geological Society, London, Special Publications; 1999; v. 157; p. 131-142;
DOI: 10.1144/GSL.SP.1999.157.01.10
© 1999 Geological Society of London

The Role of Chemical Containment in Clay Barriers

Geochemical interactions between landfill leachate and sodium bentonite

A. J. Spooner1 & L. Giusti2

1 Fossil Fuels and Environmental Geochemistry (Postgraduate Institute), Newcastle Research Group (NRG), The Drummond Building, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK
2 School of the Environment, University of Sunderland, St. George’s Way, Stockton Road, Sunderland, Tyne & Wear SR2 7BW, UK

The disposal of municipal, commercial and industrial waste by landfill has been, and is, widely used around the world. Within the landfill, leachate is generated with the input of atmospheric water, and by mixing with the moisture already present from the decomposition of waste materials. The potentially hazardous components of leachate have the ability to pollute surface and groundwaters unless stringent criteria are met for the location of landfills, suitable materials are used to build basal barriers and capping systems, and modern leachate collection and disposal techniques are employed. Different types of barriers have been used, including naturally occurring soil/clay liners, compacted clay liners, geosynthetic materials, and composite sealing systems composed of a mineral layer and a synthetic membrane. One of the substances most commonly used in the sealing of landfill sites, either on its own or in combination with synthetic materials, is sodium bentonite. Despite its widespread use, there is some evidence that this material may not be capable of attenuating some of the substances contained in landfill leachate, and that the clay mineral structure itself may be damaged as a result of long-term exposure with the various organic/inorganic components of municipal landfill leachate. In particular, bentonites tend to collapse and shrink once exposed to certain toxic effluents. The stability, chemical resistance and permeability of a bentonite clay liner appear to be significantly affected by landfill leachates and other inorganic/organic solutions used in experimental work. The main aims of this paper are: (i) to describe the properties of bentonite and municipal solid waste leachates, and (ii) to summarize the available information on the interactions between bentonite and leachate.