ure in the line used to draw carbon dioxide from
Subsequently, we were unable to perform a mass
the reactors was discovered. At first, this was not
balance on the remediation process.
considered the cause of the stunted remediation,
but, in a later round, we observed again a slowing
CONCLUSION
of the TCE reduction in the water early on during
the cycle. Again, a leak was found in the same sec-
The data from this pilot study showed that the
tion of tubing. The leak was repaired and the sub-
packed adsorbent bed could be loaded in approxi-
sequent data showed that the process resumed its
mately 36 hours at a flow rate of 120 mL/min. The
normal rate.
concentration of TCE in the clay at the end of each
The second factor that seemed to have a direct
loading cycle indicated that the loading process
effect on the rate of remediation was the mainte-
was reproducible. The remediation phase of the
nance of the phenol concentration. The bench-top
process took approximately 13 days. The reduc-
results indicated that the process would continue
tion in the TCE concentration in the clay during
with a phenol concentration as low as 60 mg/L.
each round of the study told us that the sorbent
We observed, though, that when the concentration
was being remediated by the microbiological pro-
of the phenol dropped to that level during the first
cess. The combination of this information illustrat-
few days of the remediation, the microbiological
ed that the adsorbent material could be repeatedly
process seemed to slow down. For the later
loaded and remediated, thus meeting the objective
rounds, we maintained the phenol concentration
of its rejuvenation. Areas that need to be improved
near 300 mg/L for the first few days and we found
are the rate of remediation and the loading capac-
that the total time required for the remediation
ity of the adsorption beds. Currently, each com-
step was shortened.
plete cycle of loading and remediating requires 2
We were also able to make some observations
weeks while only mineralizing 58 mg of TCE per
on the effect of temperature on the remediation.
column.
The skids were originally set up outside, with a
wood and plastic shell around them. The tempera-
LITERATURE CITED
ture inside the structure would vary dramatically,
from less than 0 to 20C ambient air temperature in
the mornings to near 40C in the afternoons when
determine the effect of temperature on the desorp-
the sun was directly shining on the structure.
tion rates of trichloroethylene from plastic clay
Owing to the time of year and the drop of daily
98b. M.S. Thesis, Air Force Institute of Technology,
temperature to below freezing, the skids were
Air Force University, Wright Patterson AFB, Ohio.
moved into a building where the temperature was
Gantzer, C.J., and L.P. Wackett (1991) Reductive
maintained at approximately 4.5 to 7C. The data
dechlorination catalyzed by bacterial transition-
from the remediations carried out at the lower
metal coenzymes. Environmental Science and Tech-
temperature do not indicate that the rate of the
nology, 25(4): 715722.
process was being affected by this.
Gerace-Coles, A. (1991) Chlorinated solvent dis-
The concentration of chloride in the water was
posal regulations, alternative, current practices.
monitored throughout the pilot study for mass
M.S. in Environmental Studies Thesis, California
balancing and to demonstrate the mineralization
State UniversityFullerton.
of the TCE. Based on the mass of TCE being pro-
Lam, T.T. (1994) Adsorption and diffusive trans-
cessed, the expected change in the chloride con-
port of chlorinated aliphatic solvents in unsaturated
centration was approximately 2.6 mg/L. The back-
soil. Ph.D. Dissertation, Rutgers--State University
ground chloride concentration of the groundwater
of New Jersey, New Brunswick.
was approximately 15 3 mg/L. Thus, we were
Shannon, D. (1995) Bioremediation consortium to
unable to measure the small concentration change
tackle chlorinated solvents. Environmental Science
that results from the mineralization of the TCE.
and Technology, 29(9): 402a.
13
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