Possible Areas of Application
Coaxial groundwater circulation (KGB) is used in the remediation of groundwater and of perched water contaminated with volatile hydrocarbons, but can also be employed to inject gas into the groundwater for the enhancement of microbiological degradation.
System Components
KGB consists of a combination of soil air venting with in situ groundwater stripping ("push and pull technique"). Clean compressed air is pumped into a pressurized air distributor located between the capillary fringe and the aquifer base depending on the vertical pollutant distribution.
Description of Method
The design of the pressurized air distributor regulates the air flow so that the air can only flow upward. The air bubbles rise within the well, causing water inside the well casing to flow upward (air-lift effect). Consequently, a continuous circulation of groundwater is generated in the area surrounding the remediation well, delivering new contaminants to the stripping zone. In contrast to other sparging methods, the clean water leaving the upper screen section of the well has no air bubbles, therefore no air-water phases can impede the flow. In addition, a mass balance can be obtained between influent and effluent air. KGB needs lower pressure, less air volume, and thus consumes less energy than conventional air sparging methods. Volatile hydrocarbons dissolved in the groundwater are transferred from the liquid to the gas phase in an amount relative to their gas-liquid distribution coefficient and are extracted from the groundwater surface via the double-cased screen. Soil air from the unsatur
Controlled vertical water and air flows differentiate the KGB from other sparging methods. Best results can be achieved if fresh air is continuously sucked into the pressurized air distributor. Heating the groundwater and consequently increasing the possibility of iron-, manganese or carbonate precipitation, which is common for conventional air sparging systems, is avoided.
A special advantage of the KGB is its ability to effectively remediate the often highly contaminated capillary fringe.
The difficulties that arise during conventional remediation procedures due to contaminated perched water, which collects in the remediation well, do not occur with the KGB. Perched water can be stripped directly in the ground without having to pump it up to an above ground treatment system.
Coaxial groundwater circulation (KGB) is a process patented by IEG Industrie Engineering GmbH, D-72770 Reutlingen, Germany.
