The Use of Bentonite in Landfills

A reduction in the availability and release of heavy metals in soil has been an interesting issue worldwide in recent years. Bentonite is a form of expandable montmorillonite clay which possesses the essential quality of a strong sorption for heavy metals.

Increasingly used in the United Kingdom, the naturally occurring clay Bentonite expands when mixed with water and becomes a very effective water-proof material.

One of the most prominent uses of Soil-Bentonite is for the sealing of landfill sites which is widely used in the United States and Australia. Modern landfills are highly engineered, consisting of individual lined compartments or ‘cells' into which waste is packed down before being covered. As the rubbish rots down within the landfill, a polluting liquid called leachate and landfill gases are produced. If not controlled, leachate can seep through the soil surrounding the site, potentially polluting rivers and underground sources of drinking water. Landfill gases such as CO2 and Methane contribute to climate change.

As Bentonite comes into contact with water it expands, strengthening and becoming water-proof. It is used as a base for the lining or sealing of a landfill to prevent the leaching of contaminants into the surrounding environment. This in turn prevents water systems from being contaminated by toxic chemicals which could fatally harm humans and animals alike.

The Rapidmix 400 C, a mobile continuous mixing plant, manufactured by Rapid International Ltd, was used in the Soil-Bentonite application in Brookhaven Landfill, Long Island, New York.

The mix produced by the Rapidmix 400 C involves the soil being loaded into the aggregate hopper and then fed to the twin shaft mixer via the belt. Measurements and feed rates are all automated throughout. The Bentonite itself is stored in the Rapidmix 400's silo and is also fed accurately to the twin shaft mixer. The water is distributed through the positive displacement pumps located in the Rapidmix 400 C. All three components come together in the mixing chamber and are mixed using the twin shaft mixer.

By utilising natural materials and adding lime, fly ash, bentonite and cement to a Rapidmix 400 C, construction can be carried out cheaply, quickly and efficiently.

The Rapidmix 400 C can also be used in various other applications: soil stabilisation; sludge solidification; road paving; airport runways and dam construction.

For more information on the Rapidmix 400 C or any other Rapid products, you can visit the website at , email: or alternatively, you can call +44 (0) 28 38 840 671.

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