With a GCW it is possible to remove non-miscible liquids of higher density than water (DNAPL) from an aquifer. In order to remove dense non aqueous phase liquids (DNAPL) that have accumulated on the bottom of the aquifer, the GCW is operated in standard mode.  The DNAPL is  removed by means of a sensor-controlled, pneumatically-driven submersible pump. Thus it is made sure that just pure phase and no groundwater is extracted.