The removal of both contaminated groundwater and soil vapour at the same time.
This can be achieved by a high vacuum system or a pump treat system.
There are a number of descriptions for dual-phase extraction but in essence it is the removal of both contaminated groundwater and soil vapour at the same time. This can be achieved by either a high vacuum system or a combination of pump and treat with vacuum enhancement.
Groundwater is recovered from abstraction wells and conveyed to the treatment plant where a number of physical treatments occur. These include separation, air stripping and carbon adsorption prior to the cleaned groundwater being disposed of to foul sewer - or to ground if acceptable to the Environment Agency.
As with most vacuum enhanced systems the capillary fringe benefits greatly from this process as it is often highly contaminated. Removal from this area removes a source of recontamination of groundwater and facilitates biodegradation with the inflows of clean air.
Geology and contaminant characterisation greatly influence the effectiveness of this technology. Care should be taken in the design and installation of the abstraction wells as these will also detract from the effectiveness of the system.