Das Projekt "Thermische In-Situ-Sanierung durch Hochfrequenz-Energie" wird vom Umweltbundesamt gefördert und von Umwelttechnik durchgeführt. The in-situ sanitation by high-frequency energy is a new procedure to restore soils which are contaminated by halogenated and aromatic hydrocarbons as well as by low-boiling aliphatic hydrocarbons (mineral oils). This low-temperature procedure makes use of the principle of dielectric warming up if high frequency electromagnetic fields are put against a dielectric medium (the soil) for 'in-site purification' of the contaminated soil. For technical realization, exciting electrodes are placed into the contaminated area according to a special arrangement which depends on the texture of the soil. Energy feed in is made by a efficient HF energy source and the soil permeated by the high frequency field is gradually warmed up to temperatures of 60 up to a maximum of 150 degree Celsius. The main part of the energy is absorbed by the water stored in the soil, the dielectricity coefficient of water being higher by the factor 10. Soil water and organic contaminations are converted to the gaseous phase which is removed from the subsoil by the exhauster levels. The steam-pollutant mix is condensed, water and pollutants are divided in a phase separator. The remaining contaminations in the exhaust air are retained and destroyed in a two-stage filter system with absorption and catalytic combustion. A newly development probe allows to measure on-line direct in site all parameters decisive for the extraction process, such as soil humidity, temperature, static differential pressure and pollutant concentration in the soil. Thus, direct observation, supervision, data logging and control of the extraction process are possible for the first time. Thanks to the new sanitation procedure, the duration of in-situ sanitations is reduced by the factor 10. Thus, a rapid relief of the environment and a reduction of the effects on groundwater are rendered possible. This procedure now allows to realize in-situ sanitations which, until now, could only be treated by excavation or safety measures.