Monday,
January 11, 2010
6:00 - 7:30 pm
Pellissippi
State Technical Community College
10915 Hardin
Valley Road, Knoxville
J.L. Goins Administration Building, Cafeteria Annex
JANUARY
PRESENTATION
Use of Water
Pillows for the Production of Anaerobic Water
During an In-Situ Groundwater Injection
by
Robert E. Mayer, Jr.
Shaw Environmental & Infrastructure, Inc.
Knoxville, Tennessee
Trichloroethene (TCE) has become a common contaminant in
groundwater due to its abundant use as a cleaning solvent,
degreaser, and in the dry cleaning chemical. At Spill Site #32
(SS-32), on Columbus Air Force Base (CAFB) in Columbus,
Mississippi, TCE is the primary groundwater chemical of concern.
The SS-32 site encloses a groundwater plume that is approximately
½ mile wide by 1 mile long. Much of the site lies along an
active training runway.
Natural attenuation of TCE at SS-32 was determined to be nutrient
limited; therefore, in-situ enhanced bioremediation using
emulsified vegetable oil, sodium lactate and Shaw&rsquos
dechlorinating consortium SDC-9 was performed. However, working
along the runway posed special challenges. The first challenge
was to create and store enough anaerobic injection mixture for a
442 point DPT injection, and the second was to reduce the height
of equipment staged near the edge of a runway. To address these
challenges, large water pillows were determined to be the most
viable solution. Previous in-situ projects utilized large, rigid
holding tanks for preparing and storing an anaerobic mixture for
sub-surface injections. The rigid tanks had an air to water
interface and required an inert gas to help purge the oxygen from
the aqueous mixture. The use of water pillows eliminated the air
to water interface and enabled microbial populations to create an
anaerobic system more efficiently without an influx of ambient
air; much like microcosms used in a lab. A system of four
6,000-gallon water pillows was used. Approximately 12,000 gallons
of anaerobic water were produced every twenty-four hours without
the use of an oxygen scrubber.
At CAFB, equipment that needed to be staged near the runway had
to be less than fifteen feet high. Many rigid holding tanks of
sufficient size would have been near the maximum height limit and
would have required flashing lights for visibility during night
flying. The water pillows were three feet tall when completely
filled. Their low height was favored by CAFB flight operations
staff and also removed the need for lighting. Also, due to faster
production of anaerobic water, the time required to be in the
field was reduced from 40 to 28 days. The shorter field duration
reduced project costs and potential impacts to flight operations.
To assess the progress of the in-situ injection, chlorinated
ethenes, anions, metabolic acids, Dehalococcides sp., and field
parameters were analyzed. Degradation rates and estimated
clean-up times for TCE to reach the federal maximum contamination
level were calculated. The results indicate that use of water
pillows for production and storage of anaerobic solution for
in-situ injection is an effective approach. The innovative use of
water pillows enabled anaerobic water to be produced more
efficiently, surpassed the equipment requirements for working
near active runways, and reduced overall project costs.
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