Environmental Engineering Reference
In-Depth Information
to collect sufficient data necessary for estimating the full-scale remedial
technology design parameters for the selected site, and the postflush assess-
ment of groundwater parameters to evaluate the potential for enhanced
in
situ
microbial degradation of the chlorinated solvents with residual cosolvent
from the extraction technology. Another objective was to evaluate the sub-
surface and environmental impact of large-scale ethanol injection. Ethanol
was selected as the cosolvent for the solvent extraction demonstration
because it has acceptable cosolvency properties and is a suitable electron
donor for stimulation of
in situ
reductive dechlorination by native micro-
organisms.
The specific objectives of the SERB demonstration were to:
•
Develop a greater understanding of halorespiration and evaluate its
potential as a bioremediation technology for PCE and other halogenated
compounds either by enhancement of native activity (biostimulation)
or by introduction of active microorganisms (bioaugmentation)
•
Develop a detailed understanding of site geomorphology, contami-
nant distribution, and hydrology utilizing new and innovative tools
and procedures
•
Develop molecular probes for the detection of known PCE-dechlori-
nating organisms
•
Conduct molecular analysis of site material for PCE-dechlorinating
communities and isolates
•
Perform laboratory microcosm tests to detect and evaluate microbial
processes
•
Evaluate cosolvent injection/extraction design and performance
•
Evaluate
in situ
bioprocess performance
•
Evaluate cost and performance
•
Predict long-term performance of the SERB approach
•
Design and produce an implementation manual for SERB technologies
5.3 Technical approach
5.3.1 Laboratory process and microbial ecology
Attempts to achieve PCE dechlorination to ethene in the field have obtained
variable success. This observation and previous work by researchers at the
Center for Microbial Ecology at Michigan State University with materials
from many different contaminated sites have suggested that this inconsis-
tency may be due to site differences in microbial populations. Thus, one
objective of the chlorinated solvents thrust area was to develop our under-
standing of the relationship between the extent of PCE dechlorination and
particular microbial populations. To support this objective, the decision was
made to develop a concerted effort focused on the analysis of microbial
communities associated with successful PCE dechlorination, which was
