Demonstration of Bioaugmentation at Kelly Air Force Base, Texas

Site Name:

Kelly Air Force Base

Location:

Texas

Period of
Operation:

November 1999 to May 2002

Cleanup
Type:

Field Demonstration

Technology:
Bioaugmentation
-- Bioaugmentation was tested to treat chlorinated solvents-contaminated groundwater. The KB-1 culture, consisting of halorespiring bacteria, was added to a bioaugmentation demonstration plot.
-- The bioaugmentation system consisted of one injection well and three extraction wells. Groundwater was extracted and pumped into a tank; electron donors (methanol and acetate) were added to the groundwater stream to achieve a total concentration of 7.2 milliMoles (mM). The groundwater was then pumped into the injection well. A groundwater recirculation rate of 3 gallons per minute (gpm) was maintained throughout the test with a residence time in the demonstration plot of approximately 8 days.
-- The demonstration plot included nine wells: one injection well, three extraction wells, and five monitoring wells. Three of the monitoring wells were aligned along the center of the plot parallel to the groundwater flow direction and located at a distance of 8, 12, and 22 ft downgradient of the injection well. The other two monitoring wells were aligned perpendicular to groundwater flow, and were initially installed to be outside the zone of influence of the system. Each of the wells in both plots were completed to a depth of 25 feet below ground surface (ft bgs) and were screened from 15 to 25 ft bgs to reduce the opportunity for aeration and increased oxygen concentrations of the groundwater as it moved through the treatment system.
-- Groundwater samples were collected monthly during operation or when system operating parameters were modified. During each sampling event, groundwater was collected for pH, temperature, conductivity, dissolved oxygen (DO), oxidation-reduction potential, salinity, and turbidity volatile organic compound (VOC), volatile fatty acid (VFA), sulfate, nitrite, nitrate, bromide (tracer), and dissolved gas analyses. In addition, samples were collected for gene probe analysis for detection of the KB-1 culture.

Cleanup Authority:
Demonstration conducted under the Department of Defense (DoD) Environmental Security Technology Certification Program (ESTCP).

Contacts:

2nd Lt. Kolin Newsome
Air Force Research Laboratory
139 Barnes Drive, Suite 2
Tyndall AFB, Florida 32403
Phone: 850-283-6308
Fax: 850-283-6064

Paul Kerch
Air Force Research Laboratory
139 Barnes Drive, Suite 2
Tyndall AFB, Florida 32403
Phone: 850-283-6126
Fax: 850-283-6064

Dr. Bruce Alleman
Battelle Memorial Institute
505 King Avenue
Columbus, Ohio 43201
Phone: 614-424-5715
Fax: 614-424-3667

Matt Place
Battelle Memorial Institute
505 King Avenue
Columbus, Ohio 43201
Phone: 614-424-4531
Fax: 614-424-3667

Dr. Dave Major
GeoSyntec Consultants
160 Research Lane
Guelph, Ontario N1G 5B2
Phone: 519-822-2230
Fax: 519-822-3151

Contaminants:
Volatiles - Halogenated; Tetrachloroethene (PCE); Trichloroethene (TCE)

Type/Quantity of Media Treated:
Groundwater (quantity not provided)

Purpose/Significance of Application:
The primary objective of the demonstration was to determine if complete reductive dechlorination could be stimulated through the introduction of a microbial culture KB-1 known to contain halorespiring bacteria. Secondary objectives involved testing the robustness of the applied microbial culture by depriving it of electron donor and adding sulfate to the system.

Regulatory Requirements/Cleanup Goals:
No regulatory requirements or cleanup goals were provided for the demonstration.

Results:
Baseline monitoring, in November 1999, indicated that PCE was the dominant chloroethene species at the site. When the electron donors alone was added to the demonstration plot, limited reductive dechlorination of PCE occurred (PCE conversion to dichlorothene [DCE]). The demonstration plot was then bioaugmented with KB-1 on May 6, 2000. Within 72 days of the addition of the KB-1 culture, ethane was detected in the demonstration plot and the PCE, TCE, and c-DCE were observed at the lowest levels observed since 1999. This indicates that the addition of the KB-1 culture stimulated complete reductive dechlorination of PCE to ethene.

After demonstrating the effects of bioaugmentation for the potential to promote complete reductive dechlorination, the system was shut down (the addition of the electron donor stopped on September 25, 2000). Groundwater samples were collected from the test plot on August 23, 2001 to determine the effects of eliminating the electron donor for one year on the population of the KB-1 culture and the reductive dechlorination process. Gene probe analysis of the groundwater samples indicated presence of KB-1 from demonstration plot. Samples from a non-augmented control plot tested negative for KB-1. The microbial analyses and the distribution of chloroethenes indicated that the KB-1 culture was present and complete dechlorination was still occurring in the demonstration plot.

Sulfate was added to the system at 3.6 mM on March 9, 2002, to determine if the competitive use of the electron donor between the chloroethenes and sulfate would limit the reductive dechlorination occurring in the test plot. Monitoring data collected on May 9, 2002 indicated that the addition of sulfate did not significantly affect reductive dechlorination.

The study indicated that the KB-1 culture was robust and able to compete with, and survive among, the indigenous microbial population. It also indicated that bioaugmentation may not require continuous monitoring following inoculation at sites where the natural attenuation requirements are met.

Cost Factors:
The total cost for the field demonstration of the bioaugmentation technology at Kelly AFB was $333,936, including: $78,000 for microcosm testing; $67,727 for capital costs for full-scale study; and $188,209 for operation and maintenance (O&M).

Description:
A field demonstration was conducted at Kelly AFB to test the capability of a microbial culture, KB-1, to dechlorinate PCE to ethane, and to test the survivability of the culture in the field under various conditions such as presence and absence of electron donors. Bioaugmentation had been successfully demonstrated earlier at Kelly AFB in microcosm studies. The demonstration plot was selected for the earlier microcosm bioaugmentation study based on the presence and concentrations of the contaminants, access to an existing test infrastructure, hydrogeology/ geology of site, and site logistics (site access, electrical power, water, etc.). The geology in the vicinity of the test site consisted of unconsolidated alluvial deposits that have been deposited on the top of the undulatory erosional surface of the Navarro Clay. The alluvial deposits consisted of gravel, sand, silt, and clay, ranging in thickness from 20 to 40 ft bgs. From the surface down, the geology typically consists of 1 to 4 ft of black organic clay, 6 to16 ft of tan silty, calcareous clay; and 4 to 20 ft of clayey limestone and chert gravel (denoted as clayey/gravel). The water table was approximately 15 to 20 ft bgs, and the saturated zone thickness was between 5 to12 ft bgs. Generally, groundwater flow is to the southwest with a flow velocity of approximately 0.3 ft/day. The volatile organic compounds (VOC) at the site groundwater consisted primarily of PCE, TCE, and their degradation products c-DCE and vinyl chloride. Total chlorinated ethene concentrations in the groundwater exceed 8,000 µg/L.