Abstract:The Research Facility for Subsurface Remediation VEGAS (Institute of Hydraulic Engineering, University of Stuttgart) and the Institute for Groundwater Research Luckner & Partner (Dresden) have developed a method for treating contaminated groundwater with a siphon-reactor system (German abbrev. DHR). This system uses an existing hydraulic gradient or a local gradient produced by an impermeable wall in order to drain groundwater by the siphon principle. Depending on the type and amount of contaminants, the water is cleaned in one or several reactors which are connected to the siphon conduit. At the beginning of the project, a DHR test plant on a technical scale was built and operated at VEGAS. The main elements of this plant are a low-pressure oil separator, a low-pressure activated carbon filter, an automatic deaeration installation, and an automatic measurement-data registration. As the tests with this plant have shown, a stable operation of the system together with a high purification efficiency are also guaranteed at low pressure. Since July 2001, this new technology has already been successfully applied on a site in Baden-Württemberg in order to remediate groundwater contaminated with chlorinated hydrocarbons. Further applications of the siphon-reactor system are currently being planned. The application on the complete site “Öl-Epple” at Stuttgart can not be realized due to financial limitations of the city of Stuttgart. Therefore it is being planned to remediate just one part on the site “Fumy” which is situated downstream of the site “Öl-Epple” (secondary contamination).