Full-Scale Evaluation of In Situ Bioremediation of Chlorinated Solvent
Groundwater Contamination
Principal Investigators
Perry L. McCarty, Mark N. Goltz, and Gary D. Hopkins
Stanford University
(Supported by the U. S. Air Force)
E-mail: mccarty@cive.stanford.edu
Goal
To evaluate at full scale the efficiency and effectiveness of in
situ aerobic cometabolic bioremediation of chlorinated aliphatic hydrocarbon
compounds at an actual hazardous waste site.
Rationale
Full-scale implementation of an innovative technology, working with
organizations in the user community, is an ideal way to communicate knowledge
gained by research and put it into practice. A full-scale application of in
situ aerobic biodegradation of chlorinated solvents is justified based upon
several years of research at Stanford University and elsewhere, and by field
demonstrations that the process can operate efficiently with indigenous
microorganisms. This project is a cooperative activity between the U. S. Air
Force, the U. S. Environmental Protection Agency, and other parties with interest
in this activity (to include citizen groups).
Approach
Recent studies conducted by Stanford University researchers at the
Moffett Field pilot site have demonstrated that trichloroethylene (TCE) can be
effectively biodegraded cometabolically through the introduction into the
subsurface of a primary substrate (such as toluene or phenol) and oxygen to
support the growth and energy requirements of a native population of
microorganisms. The proposed remediation system will consist of two wells, each
screened at two depths. In operation, a submersible pump, installed between the
two screens, will draw water into the well at one screened interval and discharge
the water out of the second screened interval. The well will have feed lines to
introduce toluene and hydrogen peroxide (as a source of oxygen) into the
discharge water. A biotransformation zone will be developed near the discharge
side of each well, and the water will circulate between the wells to clean the
aquifer.
Status
This one year successful evaluation was completed in March
1997. With pumping at 25 liters per minute at each well, and the introduction of 9 mg/l
toluene, 30 mg/l dissolved oxygen, and 41 mg/l hydrogen peroxide for fouling control and
additional oxygen, 83 to 85 percent TCE biodegradation was achieved with each pass through
a treatment well. An estimated 60-m width of the TCE contaminated plume was treated with
this system, reducing its upgradient TCE by about 98 percent from 1200 µg/l to 25 µg/l.
Toluene concentration was reduced to 1.4 + 0.6 µg/l at the 22m x 22m boundary of
the steady zone. Potential clogging was successfully controlled.
Copyright © Georgia Tech Research Corporation, 1999. All Rights
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Make comments to: mark.hodges@gtri.gatech.edu
Last modified on: December 15, 1999.
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