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bioventing is a promising new technology that stimulates the natural in situ biodegradation of any aerobically degradable compounds in soil by providing oxygen to existing soil microorganisms. In contrast to soil vapor vacuum extraction, bioventing uses low air flow rates to provide only enough oxygen to sustain microbial activity. Oxygen is most commonly supplied through direct air injection into residual contamination in soil. In addition to degradation of adsorbed fuel residuals, volatile compounds are biodegraded as vapors move slowly through biologically active soil.

The U.S. Air Force has produced a technical memorandum which summarizes the results of bioventing treatability studies of fuels conducted at 145 US Air Force sites. The memorandum discusses overall study results and presents cost and performance data and lessons learned.

Regulatory acceptance of this technology has been obtained in 30 states and in all 10 EPA regions, and the use of this technology in the private sector is growing rapidly following USAF leadership.

Bioventing is a medium to long-term technology. Cleanup ranges from a few months to several years.

Bioventing techniques have been successfully used to remediate soils contaminated by petroleum hydrocarbons, nonchlorinated solvents, some pesticides, wood preservatives, and other organic chemicals.

While bioremediation cannot degrade inorganic contaminants, bioremediation can be used to change the valence state of inorganics and cause adsorption, uptake, accumulation, and concentration of inorganics in micro or macroorganisms. These techniques, while still largely experimental, show considerable promise of stabilizing or removing inorganics from soil.

Factors that may limit the applicability and effectiveness of the process include:

* The water table within several feet of the surface, saturated soil lenses, or low permeability soils reduce bioventing performance.

* Vapors can build up in basements within the radius of influence of air injection wells. This problem can be alleviated by extracting air near the structure of concern.

* Extremely low soil moisture content may limit biodegradation and the effectiveness of bioventing.

* Monitoring of off-gases at the soil surface may be required.

* Aerobic biodegradation of many chlorinated compounds may not be effective unless there is a co-metabolite present, or an anaerobic cycle.

* Low temperatures may slow remediation, although successful remediation has been demonstrat

Source: US-EPA, Clu-In: http://www.frtr.gov/matrix2/section4/4_1.html