Stabilisation and solidification (S/S) of metal contaminated soil with ash
Industrial activity affects the land under the facility itself, but often also adjacent areas, for example through dusting. Many of these areas have been deemed necessary to clean to reduce risks to human health and avoid negative impacts on the environment. A common measure in Sweden is to excavate the soil and transport it to a landfill. This leads to large mass transports over sometimes long distances of both the contaminated soil and replacement material, while the contamination potential in the re-moved soil remains.
An alternative is to stabilise contaminated soil on the site. This can be done, for example, by mixing material into the soil that binds to the pollutants and reduces their solubility and at the same time stabilises the soil mechanically.
In this way, the pollution risks are radically reduced. Cement is the most common additive used to stabilise waste materials. A more resource-conserving alternative is to use fly ash, which has been shown to significantly reduce metal leaching from ash-stabilised soil. Fly ash from biofuel combustion contains oxides of Ca, Fe, Al, Si and Mn, which have the potential to form insoluble compounds. Oxides of Ca react with atmospheric carbon dioxide in a similar way to cement, which leads to the material hardening and developing concrete-like properties. Such a material can thus be left in place and used as a building material, for example in noise barriers. The method is one of the most common ways of handling hazardous waste in many countries but is rarely applied in Sweden.
In this project, the possibility of using stabilisation and solidification (S/S) of a metal-contaminated soil through mixing it with fly ash is investigated. The current area for the project is Näsudden in Skellefteå. It is a natural area that has been contaminated with airborne particles from Boliden's smelter. The metal contamination lies superficially in a layer up to a decimetre thick, but the size of the area means that the total amount of contaminated soil is estimated to be up to 100,000 tonnes. To be able to assess the effect of the method, site-specific recipes need to be developed and tested and the long-term effect of the stabilisation must be estimated.
The project is carried out in cooperation with the company AFRY and Skellefteå municipality and is financed by SGI within the Tuffo program.
Contact us
- Lale Andreas, Associate Professor, Third-Cycle Programmes Coordinator
- Sepideh Gholizadeh Khasevani, Doctoral Student
- Ivan Carabante, Associate Professor
- Jurate Kumpiene, Professor and Head of Subject
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