BIOAUGMENTATION FOR THE IN SITU AEROBIC COMETABOLISM OF CHLORINATED SOLVENTS - Bioaugmentation for Groundwater Remediation - page 237

bioaugmentation, but not at the further monitoring wells. After 6 days, PR1 301 was no longer
detected through most of the field season, and was not detected on glass bead coupon samples
removed at the end of the field season. Similar observations were obtained in the second season
of testing. The monitoring for PR1 301 in the field tests was generally consistent with the field
observations. When the culture was initially present, effective TCE removal was achieved. The
rapid loss of transformation activity coincided with the loss of detection of PR1 301 , and likely
resulted from the lack of survival of PR1 301 in the subsurface environment present.
8.4.3 Bioaugmentation Approach III
Bioaugmentation Approach III focuses on developing effective strains to transform con-
taminants that were not effectively transformed by indigenous microorganisms when fed a
cometabolic substrate such as methane. Strain selection has focused on microbes that grow on
butane and are able to transform chlorinated ethanes, chlorinated methanes and 1,1-DCE
(Kim et al., 2000 , 2002 ). Isolated strains often were found to be in the Rhodococcus sp.
group. A number of microcosm studies have been performed to evaluate bioaugmentation
using this approach (Table 8.3 ) along with field demonstrations (Semprini et al., 2007a , b , 2009 )
where butane was added as the growth substrate (Table 8.4 ).
8.4.3.1 Bioaugmentation with Butane Utilizers
A microcosm study with the butane enrichment culture of Kim et al. ( 2002 ) was conducted
by Jitnuyanont et al. ( 2001 ) to study the transformation of 1,1,1-TCA in bioaugmented and non-
augmented microcosms constructed with aquifer and groundwater from the Moffett Test
Facility. The non-bioaugmented microcosm required 80 days of incubation before butane
utilization was observed while the bioaugmented microcosm required only 3 days. Initially the
augmented microcosms were effective in transforming 1,1,1-TCA, but their transformation
ability decreased with prolonged incubation (400 days). The non-augmented microcosms
showed limited transformation ability in the beginning, but improvement occurred after
400 days of incubation. After 400 days, both the non-bioaugmented microcosms and the
bioaugmented had similar transformation yields of 0.04 mg 1,1,1-TCA/mg butane. DNA finger-
prints showed the microbial composition after 400 days was similar in the bioaugmented and
non-bioaugmented microcosms. The microcosms with the bioaugmented culture and 50%
mineral media effectively utilized butane and transformed 1,1,1-TCA, while those with only
5% mineral media in groundwater lost their 1,1,1-TCA transformation ability. Microbial finger-
prints indicated shifts in the microbial population with the different media combinations. The
authors indicated that the most successful bioaugmentation was achieved by enriching butane
utilizers from the Moffett Test Facility microcosms that were effective in groundwater with no
mineral media added. The authors suggested that in situ bioremediation might be achieved by
adding enriched cultures that perform well under the subsurface nutrient conditions of the site.
These microcosm studies were continued by Semprini et al. ( 2007a , b ) where a butane-
grown culture was enriched from previously bioaugmented Moffett Test Facility microcosms
that performed well. The enrichment consisted of Rhodococcus sp . microorganisms that
transformed mixtures of 1,1,1-TCA, 1,1-DCA and 1,1-DCE under the groundwater nutrient
conditions of the Moffett Test Facility. Microcosm and modeling studies showed rapid
transformation of 1,1-DCE with high transformation product toxicity and weak inhibition by
butane, while 1,1,1-TCA was much more slowly transformed and was strongly inhibited by
butane. The microcosms were repeatedly stimulated on butane and transformed the mixture of
CAHs over a period of 100 days. More rapid uptake and transformation of the butane and the