This technique uses the same principal as dual-phase extraction typically employing explosion proof water ring vacuum pumps.
However, through control of the depth of the extraction lance, the MPE technique allows the controlled extraction of free-phase NAPL/DNAPL, even lubricant or crude oils along with groundwater and soil vapour.
Extraction lances of various sizes can be utilised. The smaller the diameter of the extraction lance, the less air flow is required to entrain liquids from the borehole. Therefore an advantage of small lances is that more lances can be employed in more wells from a single MPE system. Particularly small extraction nozzles can limit the soil vapour extracted substantially. This leads to an inherent vacuum within the extraction pipework and lance network such that even if only 1 out of 10 lances is submerged, it can still extract liquids. This may be particularly helpful in more permeable soils where large diameter lances in the same scenario may produce substantial quantities of soil vapour, thus reducing applied vacuum and the potential to extract liquids from boreholes where the lances are still submerged.
Advantages of MPE include: