A company based in Beersel, Belgium manufactures heat-resistant products (seals, cords, sheets, films, ...) based on mica, which are used for industrial applications such as aircraft engines, thermal insulation, motors, electronics etc. During the production process, organic solvents are used. Soil and ground water contamination was found at the site largely involving BTEX chemicals, especially toluene. The contamination is situated below the production buildings.
As the contaminants were below the existing production halls, the only possible solution was an in situ ground water extraction technique, which was combined with a dedicated water treatment plant.
Soil air and ground water are jointly extracted by means of vacuum extraction (vane pump). Water and air are separated in a closed tank. The air phase is heated in an oxidation bed in the presence of metal catalysts at a temperature of 400 °C and converted to CO2 and water. The aqueous phase is aerated in a stripping tower so that all the volatile organic impurities are introduced into the air phase. The latter is then purified in a biological filter. In order to prevent the formation of high concentrations of toluene in the installation, sensors are mounted at several locations, which are linked to the Emergency Stop of the plant.