BIOAUGMENTATION FOR THE IN SITU AEROBIC COMETABOLISM OF CHLORINATED SOLVENTS - Bioaugmentation for Groundwater Remediation - page 235

for bioaugmentation. The culture was added to the injected groundwater to achieve a
concentration of 10 9 cells/mL. TCE and cis -DCE concentrations were reduced to below
detectable levels after 24 h of injection, and the levels did not increase until PR1 injection
was stopped. PR1 was observed 30 cm from the injection well 8 days following injection, which
coincided with a decrease in DO concentrations at the same monitoring well.
In a second phase of testing, the cells were added at different concentrations to determine
the minimum concentration for effective TCE and cis -DCE removal and to avoid plugging. The
addition of 10 7 cells/mL achieved partial CAH removal, while increasing the concentration to
10 8 cells/mL brought contaminant concentrations to non-detectable levels. Glucose and nutri-
ents were then added, but the population could not be maintained through glucose addition. The
researchers concluded that bioaugmentation with PR1 could effectively degrade TCE and cis -
DCE at cell injection concentrations of 10 8 cells/mL. PR1 was not effectively transported in the
aquifer, and plugging was evident. Oxygen transport problems were also an issue at the site.

8.4.2.4 Bioaugmentation with Burkholderia cepacia G4 with Lactate

Addition: Field Study
A pilot-scale field study at the Moffett Test Facility also was conducted to evaluate
bioaugmentation with PR1 301 grown in situ through lactate addition. Three seasons of field
studies were conducted where PR1 301 was bioaugmented on a daily basis into the test plot, with
doses in the range of 3.5-5.0 g/day in years 1 and 2, and 10.5 g/day in year 3. Lactate was fed as
the primary substrate three times a day (every 8 h) with a high concentration pulse over a period
of 15-30 min, which resulted in an average injection concentration of 13 mg/L. In year 1, lactate
was the primary substrate, while in years 2 and 3 there were periods when either lactate or
phenol were fed. In all the tests, TCE was continuously added at concentrations ranging from
80 to 100 m g/L.
The first season of testing showed lactate was consumed below non-detectable levels at all
monitoring locations after 103 h of injection. Even though lactate was consumed by the first
monitoring well (1 m from the injection well), there was no evidence of excessive bioclogging,
based on injection pressure measurements. Most of the decrease in dissolved oxygen (about
16 mg/L) occurred between the injection well and the first monitoring wells, and was in good
agreement with the 15 mg/L of DO calculated to be required for the complete oxidation of
13 mg/L of injected lactate. Over a period of 280-450 h, TCE concentrations increased to about
80% of the injection concentrations. At the other monitoring locations, TCE concentration
reached about 50% of the injection concentration over the 600 h of the test, indicating partial
removal of the TCE. Using molecular methods, PR1 301 was detected at the first monitoring well
during the first 6 days after bioaugmentation, but not at the second or third monitoring wells.
Detection of PR1 301 was very limited throughout the test.
In the second season of testing, the primary substrate was varied between lactate, then
phenol, and back to lactate. The results of the second season of testing are shown in Figure 8.5 .
During the early period with lactate fed, TCE concentrations at the monitoring locations
approached about 50% of the injection concentration. At 125 h, the substrate was changed,
and phenol was injected at a pulse-averaged concentration 6 mg/L. The approach here was to
determine if bioaugmentation would permit the rapid development of a biostimulated zone so
that if phenol or toluene were used in field scale systems they would not migrate. About 70%
removal of TCE was achieved and removal remained effective during the 250 h period phenol
was added. The degree of treatment was similar to that achieved when indigenous phenol
utilizers were stimulated at the site on 6 mg/L of phenol (Hopkins et al., 1993b ). By the second
day of addition, phenol was reduced to below the detection limit of 1 m g/L. The test