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Bioslurping is a new in situ remediation technology that combines elements of bioventing and vacuum-enhanced pumping to recover free product from the groundwater and soil while promoting the aerobic bioremediation of hydrocarbon contaminants.
Vacuum extraction/recovery removes free product along with some groundwater; vapor extraction removes high volatility vapors from the vadose zone; and bioventing enhances biodegradation in both the vadose zone and the capillary fringe.
The bioslurping system consists of well(s) into which an adjustable length ‘slurp tube’ is installed. The slurp tube is lowered into the light non-aqueous phase liquid (LNAPL) layer, connected to a vacuum pump, and removes free product along with some groundwater. When LNAPL levels decline slightly in response to pumping, the slurp tube extracts vapors (vapor extraction). The liquids (product and groundwater solution) removed from the slurp tube are sent to an oil/water separator, and the vapors to a liquid / vapor separator.
In addition , the extraction of vapors through the slurp tube promotes aeration of the unsaturated zone; it increases the oxygen content and therefore the rate of aerobic degradation.
Discussion
Bioslurping, designed to address floating LNAPL layers, is used most often at sites with fine – to medium-grained overburden materials, but it is also used successfully at sites with medium – to coarse-grained materials and in fractured rock. It can be applied at sites with shallow groundwater as well as sites with the groundwater below 30 ra.
Important observations related to the performance of bioslurping technology are:
* Bioslurping recovers free product, thus speeding remediation
* Bioslurping reduces aquifer ‘smearing’. Smearing can increase the vertical extent of contamination in the aquifer by introducing contaminants into saturated soils as LNAPL travels deeper into the aquifer on the lowered water table
* Bioslurping enhances natural in situ bioremediation of the vadose zone soils