BAUER Environment Group

Soil Vapour Extraction (SVE) - despite successful application in many cases - faces its limits in fine soil matrices, like clayey, fine-sandy soils and highly water saturated soils.

In order to shorten remediation time and to achieve a homogenous treatment under such difficult circumstances BAUER Environment Group uses the Theris process. The first field trial using the Theris process confirmed the findings of the laboratory tests carried out by the VEGAS institute at the University of Stuttgart.

This thermal in-situ process heats the subsoil by means of solid heat sources. Thus the soil is heated rapidly to 70 - 100 °C. By the resultant evaporation of the capillary water, the pollutants are driven out of the silty and dense soil layers and removed from the soil mass by a conventional-design soil vapour extractor.

25 electrically powered heating probes were installed at a 2.5 metre grid spacing and an average depth of 7 metres. The heating of the capillary water initiated after a few days led to a spontaneous rise in soil vapour concentrations. The increase in concentration was completed in all areas after around 35 - 40 days, and after 60 days it was below the starting values. In this period some 40 kg of pollutants were additionally removed from the clayey areas. The soil vapour extraction operated parallel with the soil heating. The system reliably prevented vertical diffusion of the pollutant vapours created by the heat generation towards the water-saturated zone.