BIOAUGMENTATION FOR GROUNDWATER REMEDIATION: AN OVERVIEW - Bioaugmentation for Groundwater Remediation - page 24

bioaugmentation was used to successfully remediate TCE in a well-monitored demonstration
project at the Cape Canaveral Air Force Station, Florida (Hood et al., 2008 ). Similar results
using a commercially available KB-1 # inoculum were achieved at the Caldwell Trucking
Facility in New Jersey (Kane et al., 2005 ) and Kelly Air Force Base (AFB), Texas (Major
et al., 2002 ). A different culture was used with similarly successful results at Dover AFB (Ellis
et al., 2000 ). A recent field demonstration successfully used gene biomarkers to track the
dechlorination (Scheutz et al., 2008 ).
The use of bioaugmentation to remediate chlorinated ethene pollution has enjoyed greater
success than any other bioaugmentation approach for several reasons. First, the organisms that
can degrade these compounds are not ubiquitous and are generally not common in contami-
nated environments, unlike the case for petroleum degraders. Also, CAH degradation has
profited from greater interest and research than other pollutants, with the result that there are
now proposed protocols for CAH remediation, like the reductive anaerobic biological in situ
treatment technology (RABITT) (Morse et al., 1998 ). The use of bioaugmentation to degrade
chlorinated ethenes has been succinctly detailed in a white paper (ESTCP, 2005 ).
1.6.2 Applications for Other Chlorinated Compounds
There are numerous chlorinated compounds other than CAHs, and these also present
difficult cleanup challenges. These pollutants include PCBs used in a wide variety of applica-
tions including dielectric fluids and flame retardants, and carbon tetrachloride used in fire
extinguishers, refrigerants and cleaning agents. PCB contamination is widespread and persis-
tent. Dehalococcoides strains are able to dechlorinate highly chlorinated PCBs (Fennell et al.,
2004 ). There have been few studies on the use of bioaugmentation for enhanced degradation of
PCBs at the field scale, although it has been tested in microcosms (Winchell and Novak, 2008 ).
One co-culture has been found to be able to couple PCB degradation with growth and could
make for a good bioaugmentation inoculum (May et al., 2008 ).
Carbon tetrachloride is a widespread groundwater contaminant whose use has been
discontinued. Chapter 9 discusses in depth the use of bioaugmentation to remediate CT,
which may represent another promising target for bioaugmentation. A bioaugmentation pilot
experiment showed positive results with the degradation of carbon tetrachloride by Pseudomo-
nas stutzeri KC without an accumulation of formaldehyde (Dybas et al., 1998 , 2002 ).
1.7 BIOAUGMENTATION TO REMEDIATE OTHER
CONTAMINANTS
Several reviews have summarized the key literature regarding bioaugmentation (Gentry
et al., 2004 ; Scow and Hicks, 2005 ). There is a gradient of success that seems to correlate with
the chemical nature of the pollutant. For example, bioaugmentation has been more successful
for compounds that are absent or rare in natural systems than for those more commonly found
at high concentrations. Thus, chlorinated solvents, which are naturally present at low concen-
trations, respond better to bioaugmentation than petroleum products, which have existed at
high concentrations in natural systems for millennia. The genes to degrade newly introduced
xenobiotics may not have yet evolved or be widespread, and thus only a few bacteria are
capable of their degradation. The energy yield available to an organism from metabolizing the
chemical also may be important, as competition may be more intense for higher-energy
substrates. For example, the yield from chlorinated ethene respiration decreases as the number
of chlorines decrease, and the number of indigenous bacteria that can gain energy from