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.
GRS has specialised in constructing systems with a multi-functional application. By installing two inlet separators, two vacuum headers and two or more high vacuum pumps, the operator can choose between the following applications:
- High Vacuum on one branch of wells and low vacuum on another. This can overcome the problem of air flow following the path of least resistance and the failure to remediate less permeable parts of the site.
- Dual-phase or multi-phase extraction on one header and lower vacuum SVE on another header. This enables a single system to extract liquids from numerous wells in very permeable soils while simultaneously extracting soil vapours from the same wells using separate pumps. The operator has the ability to select the number of pumps connected to either header.
Advantages of MPE include:
- Simultaneously extract soil vapour and liquids with the same pump if required;
- Recovery of viscous/dense products eg lubricating oil;
- No complex down-hole skimmer pump systemsl;
- Simultaneously control the cone of depression, skim free-phase product and vapour extract if required.
Associated Treatment Technologies
GRS Typically supplies integrated containerised plant inclusive of off-gas treatment technologies such as catalytic oxidation or activated carbon and aqueous phas treatment for abstracted liquids such as oil/water separation, air stripping, activated carbon etc.
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