Bioslurping combines elements of bioventing and vacuum-enhanced pumping of free-product to recover free-product from the groundwater and soil, and to bioremediate soils. The bioslurper system uses a "slurp" tube that extends into the free-product layer. Much like a straw in a glass draws liquid, the pump draws liquid (including free-product) and soil gas up the tube in the same process stream. Pumping lifts light non-aqueous phase liquids (LNAPLs), such as oil, off the top of the water table and from the capillary fringe (i.e., an area just above the saturated zone, where water is held in place by capillary forces). The LNAPL is brought to the surface, where it is separated from water and air. The biological processes in the term "bioslurping" refer to aerobic biological degradation of the hydrocarbons when air is introduced into the unsaturated zone. This is akin to bioventing, a technology described separately. When free-product removal activities are completed, the bioslurping system is easily converted to a conventional bioventing system to complete the remediation.
Limitations and Concerns
Bioslurping is less effective in tight (low-permeability) soils. The greatest limitation to air permeability is excessive soil moisture. Optimum soil moisture is very soil-specific. Too much moisture can reduce air permeability of the soil and decrease its oxygen transfer capability. Too little moisture will inhibit microbial activity.
Low temperatures slow remediation.
The system has difficulty establishing a vacuum on deep, high permeability sites.
A fluctuating water table could create saturated soil lenses, which are difficult to aerate.
Since the fuel, water, and air are removed from the subsurface in one stream, mixing of the phases occurs. These mixtures may require special oil/water separators or treatment. Air emissions from the bioslurper system often require treatment before discharge. Bioslurper systems may extract large volumes of water that may need to be treated prior to discharge.
Accurate placement of extraction is a key to the success of bioslurping.
Bioslurping is used to remediate soils contaminated by fuel, as well as groundwater contaminated with fuel LNAPLs. It can help to remediate soils contaminated with nonhalogenated volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs). It is applicable at sites with water tables greater than 30 feet.
Technology Development Status
Bioslurping is a commercially available technology.
Other Resources and Demonstrations
See technology description for Bioventing.