BioslurpingBioslurping is the adaptation and application of vacuum-enhanced dewatering technologies to remediate hydrocarbon-contaminated sites. Bioslurping utilizes elements of both, bioventing and free product recovery, to address two separate contaminant media. Bioslurping combines elements of both technologies to simultaneously recover free product and bioremediate vadose zone soils. Bioslurping can improve free-product recovery efficiency without extracting large quantities of ground water. In bioslurping, vacuum-enhanced pumping allows LNAPL to be lifted off the water table and released from the capillary fringe. This minimizes changes in the water table elevation which minimizes the creation of a smear zone. Bioventing of vadose zone soils is achieved by drawing air into the soil due to withdrawing soil gas via the recovery well. The system is designed to minimize environmental discharge of ground water and soil gas. When free-product removal activities are completed, the bioslurping system is easily converted to a conventional bioventing system to complete the remediation.

Operation and maintenance duration for bioslurping varies from a few months to years, depending on specific site conditions.

Applicability:

Bioslurping can be successfully used to remediate soils contaminated by petroleum hydrocarbons. It is a cost-effective in situ remedial technology that simultaneously accomplishes LNAPL removal and soil remediation in the vadose zone. Bioslurping is also applicable at sites with a deep ground water table (>30ft.).

Limitations:

Factors that may limit the applicability and effectiveness of the bioslurping process include: Bioslurping is less effective in tight (low-permeability) soils.

Low soil moisture content may limit biodegradation and the effectiveness of bioventing, which tends to dry out the soils.

Aerobic biodegradation of many chlorinated compounds may not be effective unless there is a co-metabolite present.

Low temperatures slow remediation.

Frequently, the off-gas from the bioslurper system requires treatment before discharge. However, treatment of the off-gas may only be required shortly after the startup of the system as fuel rates decrease.

At some sites, bioslurper systems can extract large volumes of water that may need to be treated prior to discharge depending on the concentration of contaminants in the process water.

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 before the process water can be discharged.

Bioslurping would work in GA because we have relatively normal soil moisture throughout the year. It is sometimes dry in the autumn and summer months so that could be a problem. During the winter, the soil moisture is high.

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). Thevacuum-induced negative pressure zone in the well promotes LNAPL flow toward 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 vapors (vapors extraction). This removal of vapors promotes air movement through the unsaturated zone, increasing oxygen content and enhancing aerobic bioremediation (bioventing). When mounding due to the introduced vacuum causes a slight rise in the water table, the slurp cycles back to removing LNAPL and groundwater. This cycling minimizes water table fluctuations, reducing smearing associated with other recovery techniques.

Liquid (product and groundwater) removed through the slurp tube is sent to an oil/water separator, and vapors are sent to a liquid vapor separator. Aboveground water and vapor treatment systems may also be included, if required. However, in some cases, system design modifications have allowed discharge of groundwater and vapor extracted via bioslurping without treatment. Results of field tests of bioslurping systems have shown that LNAPL and vapor recovery are directly correlated with the degree of vacuum. A comparison of bioslurping to conventional methods of LNAPL recovery reported that bioslurping achieved the greater recovery rates than either skimming or dual-pump methods.

Reported advantages of bioslurping, as compared to other LNAPL recovery/treatment techniques, include lower project costs (because less groundwater is extracted and because vapor and groundwater may not require treatment) and a reduction in aquifer smearing. Disadvantages cited as associated with bioslurping include potential biofouling of well screens due to active aeration and lack of treatment of residual LNAPL contamination in saturated soils.

http://www.frtr.gov/matrix2/section4/4-35.htmlhttp://www.clu-in.org/download/toolkit/slurp_o.pdfhttp://www.hawaii.edu/abrp/Technologies/biovent.htmlhttp://www.hawaii.edu/abrp/Technologies/biovent.htmlhttp://www.wcc.nrcs.usda.gov/publications/SCAN_SoilMoisReg.pdf