Hans-Peter Koschitzky, Dietmar Müller and Yvonne Spira 

EURODEMO is highly pleased to endorse Thermally Enhanced Soil Vapour Extraction (TSVE) using steam/steam-air injection (TUBA) or thermal wells (THERIS) as EURODEMO "Feature Technology" in the field of soil and groundwater remediation, as this in situ technology meets EURODEMO's sustainability demands for innovative technologies:

• the physical principles and processes induced by the technology are understood
• the set-up and the results of lab experiments and field studies are well documented
• compared to a conventional reference technology (SVE: ‘cold' Soil Vapour Extraction)
  • contaminant extraction rates are high, and remedial targets are effectively achievable
  • decontamination is considerably faster (up to factor 10)
  • costs and wider environmental impacts are significantly less

The application of Thermally Enhanced Soil-Vapour Extraction using steam/steam-air injection (TUBA) or thermal wells (THERIS) for the cleanup of volatile and semi-volatile organic contaminants in the unsaturated and in the saturated zone are promising and reliable technologies for enhancing the remediation of source zones. Following an increase of the temperature in the subsurface, the volatility of organic solvents increases and the interfacial tension is reduced, therewith extraction rates increase significantly. Unlike to other in situ remediation technologies, thermal remediation technologies have the big advantage that soil heterogeneities have little effect on heat propagation. Efficient treatment of soil layers with high to low permeability within one remediation zone can achieved with TUBA, increasing the soil temperature also through convective heating. If the layers of low permeability have a certain thickness, TUBA and THERIS can be combined to heat the layers of low permeability with the thermal wells. The self contained application of THERIS is preferred for low to very low permeable soils.
The organizations  VEGAS and  Reconsite have successfully demonstrated in several pilot and field applications (see file links), that soil remediation using TSVE with steam/steam-air injections or thermal wells is effective, energy efficient and fast. Therefore, TSVE with TUBA or THERIS is promoted by EURODEMO as being eco-efficient and a 'Factor-4-Technology' (a technology providing a double service and having half the impacts).

Hans-Peter Koschitzky (VEGAS, DE), Uwe Hiester (Reconsite, DE)

TSVE summarises methods for the in situ heating of soils and groundwater to vaporize organic contaminants like Non-Aqueous Phase Liquids (NAPL) in the soil matrix or in the groundwater (unsaturated and saturated soil zone). The processes induced by the heating are similar for different kinds of contaminants. Therefore, TSVE can be successfully applied for efficient source removal of VOC, BTEX, petroleum derived hydrocarbons and similar components. In specific cases, the high temperatures induced by thermal wells may also be a solution for the remediation of PAH or tar oil. For a successful application of TSVE, the extraction of soil vapour is essential, and sometimes an additional groundwater extraction may be recommendable.
TSVE can be applied in the unsaturated zone as well as in the saturated zone over a wide range of soil permeabilities (sand to clay) and contaminants. TUBA and THERIS can also be combined in special cases.
An efficient use of the methods requires a detailed site investigation to localize the contaminant source. The additional cost for site investigation are multiply reduced by the effective remediation with TUBA or THERIS.
During the past years, several successful projects have been conducted inside urban areas and even below buildings without any restriction to their use or the use of adjacent buildings. Designed and applied with the detailed engineering knowledge, the impacts on the surroundings could be limited on the installation of the treatment system and maintenance intervals. The remediation could be finished within some weeks or a few month.
Applied for source remediations, TSVE is a cost efficient alternative to conventional methods like excavation and disposal (dig and dump). Life cycle assessment analyses (LCA) of successfully completed TSVE field projects have shown a lower natural resource consumptions of TSVE (e.g. fossil resources) as well as lower environmental impacts (e.g. CO₂-immissions and global warming) compared with conventional remediation methods. For application, no special permissions are needed.
Overall,  Reconsite and  VEGAS consider TSVE a remediation technology with high potential, which may get increased recognition across Europe through being featured by EURODEMO.