Biological/Physical in-situ Groundwater Remediation using Groundwater-Circulation-Wells (GZB®) Possible Areas of Application Due to the minimal environmental impact and low cost of implementation, biological remediation technologies have become increasingly popular during the last few years. In an ideal case, depending on the type of contaminants on the site, naturally occurring microorganisms completely mineralize organic compounds. A waste air decontamination system is obsolete. The rate of biodegradation is determined by the existing chemical and physical conditions. The goal of in-situ biological remediation technologies is to optimize the existing degradation potential. By improving the environmental conditions needed by the degrading bacteria, an effective reduction of contaminants is achieved. System Components The system consists of a specially adapted groundwater well, and a bioreactor positioned either in the well or above ground. Description of Method The GZB® technology is especially suitable for eliminating biologically degradable contaminants (e.g. hydrocarbons, phenols, pesticides, etc.) from the groundwater without having to pump the groundwater to the ground surface. The specially designed UVB produces a groundwater convection cell in the aquifer around the remediation well. The circulating groundwater constantly transports both contaminants and existing degrading bacteria to the well. When flowing through the well the contaminants are adsorbed onto the material inside the bioreactor; simultaneously the bacteria settle in the same area. If necessary, the accumulated microorganisms can be supplied with nutrients. Another advantage of the UVB is the oxygen enriched groundwater, which enhances the population growth of the microorganisms in the aquifer, thus accelerating the degradation process. System variations are discontinuous circulation flow, reversing the circulation direction, installing different biofilter configurations and materials, and using a combination of physical, chemical and/or biological methods enabling the technology to be adapted to he specific contaminated site. The above described Groundwater-Circulation-Well (GZB®) is a patented process by IEG Industrie Engineering GmbH, D-72770 Reutlingen, Germany.