Thermal desorbtion, the company explains, is simply the application of heat to contaminated soils. It is an ex-situ process, heating soils to between 300 and 550°C. The treatment takes place in a specialised portable plant that heats the soil indirectly in a rotating drum. The clean soil can be reused, while the separated hydrocarbon contaminants are recovered. There is no incineration or oxidation in the process.

Land Clean states that it will have a plant in the UK imminently and it is fully licensed under the Environment Agency Mobile Plant Licensing system.

Features of the method

The company outlines the features of this method of treatment as:

  • achieves 25 tonnes per hour or more
  • treats petrol, diesel or mineral range organics, PAHs, pesticides, solvents and PCBs
  • stated to be considerably cheaper than disposal of hazardous wastes
  • treated soil can be reused on site
  • PH & PAHs can be reduced to less than 1mg/kg
  • no upper limits on contaminant loading, moisture content or fines content
  • the system can manage organic cyanide or mercury contaminated soils
  • this is a well understood technology through North American and European experience.

    Land Clean Ltd has undertaken treatability trials for the following soil types:

    1 Sludge from gasification plant: 17% PAH & TPH loading, 40% moisture content, 100% silt and clay – treatable.

    2 Gas works waste: liquid coal tars present up to 5% loading, moisture content up to 30% – treatable.

    3 Other trials undertaken elsewhere have shown that oil refining sludges and oil exploration drilling muds are readily treatable


    4 Furthermore, pesticides and chlorinated solvents can also be handled due to the acid gas removal capability.

    Design considerations

    The company says that the following issues should be considered when designing for this treatment system:

  • hydrocarbon loading and moisture content will impact treatment rate.
  • space available on site for treatment plant (10m x 20m minimum plus clean and dirty stockpiles).
  • fuel costs are the main operating costs – therefore a slow treatment rate will result in higher treatment costs.
  • heavy metal contamination is generally unaffected by treatment.
  • allowance needs to be made for excavation and replacement/recompaction of soils.

    Land Clean can also cite examples of a range of land remediation case studies, ranging for the on-site bioremediation of soil in a timber treatment yard where the primary contaminant was creosote, involving long term environmental monitoring of the site, to the excavation and disposal to licensed facilities of impacted soils at a scrap yard. This involved the excavation, over drumming and disposal of 30 buried chemical drums.

    The company’s wide range of remediation works has also taken in foundry, gas works and used oil processing plant contracts.

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