High vacuum multi phase extraction or ’slurping’ involves the simultaneous application of vacuum enhanced extraction/recovery, soil vapour extraction, and bioventing to address Light Non Aqueous Phase Liquid (LNAPL), groundwater and soil contamination. Vacuum extraction/recovery is used to remove free product along with some groundwater. Vapour extraction is used to remove high volatility vapours from the vadose zone. Bioventing is used to enhance aerobic biodegradation in the vadose zone and capillary fringe.

High vacuum multi-phase extraction installed at the Horsebridge development in Whitstable, Kent. See the video:
Open Video and case study.

The bioslurping system is made up of a well into which an adjustable length “slurp tube” is installed. The slurp tube, connected to a vacuum pump, is lowered into the LNAPL layer, and pumping begins to remove free product along with some groundwater (vacuum enhanced extraction/recovery). The vacuum-induced negative pressure zone in the well promotes LNAPL flow towards the well and also draws LNAPL trapped in small pore spaces above the water table. When the LNAPL level declines slightly in response to pumping, the slurp tube begins to draw in and extract vapours (vapours extraction).

This removal of vapours promotes air movement through the unsaturated zone, increasing oxygen content and enhancing aerobic bioremediation (bioventing). When the introduced vacuum causes a slight rise in the water table, the slurp cycles back to removing LNAPL and groundwater. This cycling minimises water table fluctuations, reducing “smearing” associated with other recovery techniques.

Ecologia is able to design, manufacture, install and operate a wide range of high vacuum extraction systems, ranging from single wells at domestic properties to multi well systems at large sites.