Overview: The Nebraska Department of Environmental
Quality (NDEQ) began considering an enhanced in situ bioremediation pilot study
at the Ogallala Groundwater Contamination site in 1998. The project commenced
after ITRC provided NDEQ staff with training, documents, and networking
opportunities regarding in situ bioremediation. The pilot study was
designed to demonstrate the application of the enhanced anaerobic degradation
process at this site contaminated by chlorinated solvents. Though the study is
ongoing, initial indications are positive; they show that this technology can
be used to remediate this site as well as other chlorinated solvent sites in
Nebraska. In addition, NDEQ and Region VII EPA took this opportunity to study
enhanced reductive dechlorination treatability on a portion of the PCE
(tetrachloroethlylene) groundwater plume. The implementation of the Ogallala
pilot study is already prompting enhanced in situ bioremediation to be
considered for other sites in Nebraska. The momentum is also building for
additional applications of this technology. The following provides background
information about the Ogallala project as well as about the current status and
anticipated actions.
Background: A treatability study was performed at the
Ogallala Groundwater Contamination Site to determine whether PCE could be
reductively dechlorinated in the shallow alluvial aquifer. An in situ
treatment cell was developed in a portion of the PCE plume at a downgradient
from the dry cleaners. A substrate solution consisting of 60% food grade sodium
lactate was injected at intervals of 3 to 4 weeks to allow for adequate mixing
and dispersal. Geochemical changes in the groundwater were monitored to assess
the REDOX conditions and to ascertain the best injection schedule. Conditions
in the groundwater plume were reduced in a step-wise fashion: first was
denitrification, followed by reduced iron and manganese, and finally by reduced
sulfate. (Murt et al., 2000). Fermentation of the lactate was confirmed by the
presence of volatile acids under methanogenic conditions and an increase in
carbonate. Reducing conditions and microbial fermentation of the lactate
indicate that geochemical conditions are appropriate for the reductive
dechlorination process. Ground water analyses performed during March and April
indicate that PCE is being reductively dechlorinated. The concentration of PCE
was significantly lower at the downgradient end of the test cell in addition to
the detection of both TCE and cis-1,2-DCE. Vinyl chloride has not been detected
to date, which may be the result of the low concentrations of cis-1,2-DCE or
the rate of ground water flow at the test site area in relation to the size of
the cell.
ITRC Involvement: In September 1997, two members of
NDEQ staff and management attended the first ITRC Natural Attenuation course,
held in Austin, Texas. The training class served as a catalyst for the enhanced
in situ bioremediation project. Of the training introduction, Victoria
Murt, NDEQ Ogallala Project Manager, said: "The book [training manual] and the
class [ITRC Natural Attenuation Training] provided a more clear understanding
of the various bioremediation mechanisms and the necessary geochemical and
food/nutrient requirements. Of particular help were the one-on-one discussions
that I had with various trainers regarding studies that were currently
underway." The professional relationships she and others gained through the
ITRC network are fostering acceptance of innovative technologies in Nebraska.
Benefits: Nebraska is benefiting from its participation in ITRC by
planning for future cleanup efforts. Initial information from the pilot study
has prompted this technology to be considered for other operable units at the
Ogallala site as well as for other sites in Nebraska. If this enhanced in
situ bioremediation technology is implemented as the primary technique,
over a more traditional pump and treat scenario at the Ogallala site, the
overall cost savings has been estimated at 50% to 75% over that for the more
traditional technology.
The confidence level and willingness of NDEQ staff and management
to evaluate and use new environmental technologies is a direct result of their
ITRC participation. NDEQ project managers have benefited from the network of
others across the nation-including state regulators and industry experts who
serve as resources for this project. In addition, the EPA Region VII project
manager for Ogallala has taken the same ITRC training in natural attenuation
and has access to the same ITRC technical and regulatory documents (Natural
of Chlorinated Solvents in Groundwater: Principles and Practices and Technical
and Regulatory Requirements for Enhanced In Situ Bioremediation of Chlorinated
Solvents in Groundwater). This shared training and information has led to
greater cooperation on this EPA-led and state cost-share site.
Through the ITRC, NDEQ personnel can develop professionally while
making great strides in cleaning up some of Nebraska's most significant
hazardous waste sites. In May 2000, Victoria Murt will be presenting the
results of the pilot study at the internationally renowned bioremediation
conference sponsored by Batelle in Monterey, California. In the draft document
written by Ms. Murt and her colleagues, the ITRC document entitled Technical
and Regulatory Requirements for Enhanced In Situ Bioremediation of Chlorinated
Solvents is a primary reference.
Who to Contact for Additional Information: Victoria
Murt Nebraska Department of Environmental Quality Suite 400, The Atrium
1200 N Street Lincoln, NE 68509-8922 P: (402) 471-6411 F: (402)
471-2909 deq115@mail.deq.state.ne.us
Reference: Murt, V. (NDEQ), Huscher, T. (NDEQ), and
Easley, D. (Region VII EPA), A Reductive Dechlorination Treatability Study
of a Shallow Alluvial Aquifer, March 2000 draft, in preparation for the
Batelle Bioremediation Conference, May 2000. |