Description:

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.

Synonyms:

Applicability:

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.

Limitations:

• 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 demonstrated in extremely cold weather climates.

Data Needs:

Soil grain size and soil moisture significantly influence soil gas permeability. Perhaps the greatest limitation to air permeability is excessive soil moisture. A combination of high water tables, high moisture, and fine-grained soils has made bioventing infeasible at some Air Force test locations.

Several soil characteristics that are known to impact microbial activity are pH, moisture, and basic nutrients, ( e.g., nitrogen and phosphorus), and temperature. Soil pH measurements show the optional pH range to be 6 to 8 for microbial activity; however, microbial respiration has been observed at all sites, even in soils that fall outside this optimal range. Optimum soil moisture is very soil-specific. Too much moisture can reduce the air permeability of the soil and decrease its oxygen transfer capability. Too little moisture will inhibit microbial activity. Several Air Force bioventing test sites have sustained biodegradation rates with moisture levels as low as 2 to 5% by weight. However, in extremely arid climates, it may be possible to increase the rate of biodegradation through irrigation, or humidifying the injected air.

Biological activity has been measured at Eielson AFB, Alaska, in soil temperatures as low as 0° C. Bioventing will more rapidly degrade contaminants during summer months, but some remediation occurs in soil temperatures down to 0° C.

Hydrocarbon degradation rates are almost always estimated from oxygen utilization rates using a simple stoichiometric relationship with the implicit assumption that all oxygen loss is due to the mineralization of hydrocarbons by microbes. However, simple stoichiometric relationships do not account for biomass production and inorganic oxidation reactions. Oxygen serves a terminal electron acceptor not only in the degradation of organic matter but also in oxidation of reduced inorganic compounds by microorganisms which obtain energy through chemical oxidation. In situ respiration tests can also be taken. Measurement of oxygen utilization in a nearby uncontaminated area is used to account for inorganic oxidation reactions. When used with other indicators of increased microbial activity or biodegradation, respiration tests can provide one of several convergent lines of independent evidence to at least qualitatively document biodegradation.

Performance Data:

Cost:

The key cost driver information and cost analysis was developed using the Remedial Action Cost Engineering and Requirements (RACER) software. 

Key Cost Drivers 

·        Surface area is the primary cost driver

o       Impacts the number of injection/extraction wells that are installed.  The number of wells installed (and cost) increases with surface area.

·        Soil Type

o       Soil types containing sand and gravel produced significantly lower costs by reducing the number of injection/extraction wells that needed to be installed.

Cost Analysis

The following table represents estimated costs (by common unit of measure) to apply bioventing technology at sites of varying size and complexity.   A more detailed cost estimate table which includes specific site characteristics and significant cost elements that contributed to the final costs can be viewed by clicking on the link below.

Detailed Cost Estimate

Other factors that affect the cost of bioventing include contaminant type and concentration, soil permeability, well spacing and number, pumping rate, and off-gas treatment. This technology does not require expensive equipment and relatively few personnel are involved in the operation and maintenance of a bioventing system. Periodic maintenance monitoring is conducted.

References:

Engineered Approaches to In Situ Bioremediation of Chlorinated Solvents: Fundamentals and Field Applications, July 2000, EPA-542-R-00-008

Treatment Technologies for Site Cleanup: Annual Status Report (ASR), Tenth Edition, EPA 542-R-01-004

Innovative Remediation Technologies:  Field Scale Demonstration Project in North America, 2nd Edition

Remediation Technology Cost Compendium - Year 2000

Groundwater Cleanup: Overview of Operating Experience at 28 Sites, September 1999, EPA 542-R-99-006,

Treatment Experiences at RCRA Corrective Actions, December 2000, EPA 542-F-00-020

Abstracts of Remediation Case Studies, Volume 4,  June, 2000, EPA 542-R-00-006

Guide to Documenting and Managing Cost and Performance Information for Remediation Projects - Revised Version, October, 1998, EPA 542-B-98-007

Bioventing Performance and Cost Results From Multiple Air Force Test Sites (June 1996)

EPA, 1995 Soil Vapor Extraction (SVE) Enhancement Technology Resource Guide: Air Sparging, Bioventing, Fracturing, Thermal Enhancements, : To Order this document click on EPA 542-B-95-003.

Michigan Soil Vapor Extraction Remediation (MISER) Model: A Computer Program to Model Soil Vapor Extraction and Bioventing of Organic Chemicals in Unsaturated Geologic Material (EPA 600-R-97-009)

AFCEE, 1994. Bioventing Performance and Cost Summary, Draft. Brooks AFB, TX.

Aggarwal, P.K., J.L. Means, R.E. Hinchee, G.L. Headington, and A.R. Gavaskar, July 1990. Methods To Select Chemicals for In-Situ Biodegradation of Fuel Hydrocarbons, Air Force Engineering & Services Center, Tyndall AFB, FL.

California Base Closure Environmental Committee (CBCEC), 1994. Treatment Technologies Applications Matrix for Base Closure Activities, Revision 1, Technology Matching Process Action Team, November, 1994.

EPA, 1992. Evaluation of Soil Venting Application, EPA/540/S-92/004; NTIS: PB92-232362.

CD-ROM of Case Studies:  "FRTR Cost and Performance Remediation Case Studies and Related Information"; EPA 542-C-01-003; May 2001.

• Dover Air Force Base, Building 719
• Bioventing Treatment at Refueling Loop E-7, Source Area ST20, Eielson Air Force Base, Alaska
• Low-intensity Bioventing for Remediation of a JP-4 Fuel Spill at Site 280, Hill Air Force Base, Ogden, Utah
• Soil Vapor Extraction and Bioventing for Remediation of a JP-4 Fuel Spill at Site 914, Hill Air Force Base, Ogden, Utah
• Underground Storage Tanks (USTs) Bioventing Treatment at Lowry Air Force Base (AFB), Denver, Colorado
• Multiple Air Force Sites

DOE, 1993. Methanotrophic In Situ Bioremediation Using Methane/Air and Gaseous Nutrient Injection Via Horizontal Wells, Technology Information Profile, Rev. 2, DOE ProTech Database, TTP Reference No.: SR-1211-06.

Hinchee, R.E., S.K. Ong, and R. Hoeppel, 1991. "A Treatability Test for Bioventing," in Proceedings of the 84th Annual Meeting and Exhibition, Air and Waste Management Association, Vancouver, BC, 91-19.4.

Hinchee, R.E., S.K. Ong, R.N. Miller, and D.C. Downey, 1992. Report to AFCEE, Brooks AFB, TX.

Hinchee, R.E., 1993. "Bioventing of Petroleum Hydrocarbons," Handbook of Bioremediation, Lewis Publication, Boca Raton, FL, pp. 39-59.

Hoeppel, R.E., R.E. Hinchee, and M.F. Arthur, 1991. "Bioventing Soils Contaminated with Petroleum Hydrocarbons," J. Ind. Microbiol., 8:141-146.

Leeson, A., and Hinchee, R.E, 1996. Principles and Practices of Bioventing, Volume I: Bioventing Principles, prepared by Battelle Memorial Institute for U.S. Air Force and U.S. EPA.

Leeson, A., and Hinchee, R.E, 1996. Principles and Practices of Bioventing, Volume II: Bioventing Design, prepared by Battelle Memorial Institute for U.S. Air Force and U.S. EPA.

USAEC, 1997. "Bioventing of POL Contaminated Soils" in Innovative Technology Demonstration, Evaluation and Transfer Activities, FY 96 Annual Report, Report No. SFIM-AEC-ET-CR-97013, pp. 75-76.

• Chemical Disposal Pit, Hill AFB, UT 
• Savannah River
• Air Force Tech Demo
• Tyndall AFB, FL, Armstrong Laboratory/EQW
• Refueling Loop E-7, Source Area ST20, Eielson AFB, AK
• JP-4 Fuel Spill at Site 280, Hill AFB, Ogden, UT
• JP-4 Fuel Spill at Site 914, Hill AFB, Ogden, UT
• Lowry AFB
• DOI Tech Demo: (USGS) Galloway Township, NJ
• 

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A list of vendors offering In Situ Biological Soil Treatment is available from EPA REACH IT which combines information from three established EPA databases, the Vendor Information System for Innovative Treatment Technologies (VISITT), the Vendor Field Analytical and Characterization Technologies System (Vendor FACTS), and the Innovative Treatment Technologies (ITT), to give users access to comprehensive information about treatment and characterization technologies and their applications.

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