Biomedical Engineering Reference
In-Depth Information
10.5.2 MC-100 (Connecticut, USA)
Equilon reported a full scale bioaugmented biobarrier installation at a retail service station
in western Connecticut (Spinnler et al.,
2001
). For 2 years prior to the biobarrier installation, the
average MTBE groundwater concentrations ranged from 7,000-40,000
m
g/L, with a target
MTBE cleanup level of 70
g/L. Low concentrations of BTEX also were observed, with average
total concentrations less than 1,000
m
g/L. The dissolved oxygen concentrations in the plume
were less than 1 mg/L prior to bioaugmentation. Oxygen was introduced by pulsed injection.
MC-100 injections were spaced approximately 2 ft (0.7 m) laterally and over the vertical range
of 12-30 ft (3.7-9.1 m) bgs. Approximately 100 gallons (380 L) of suspension was injected into
each boring. The total mass of MC-100 injected at the site was 175 kilograms (kg) dry wt
(385 pounds [lb]).
The mean MTBE concentration from monitoring wells in the vicinity of the biobarrier
before the system was operational was 12,000
m
m
g/L. After approximately 16 months of
operation, the mean concentration was 8
g/L, a 99.9% reduction. Mean concentrations of
MTBE in the “upgradient” wells not affected by the activity of the biobarrier remained
relatively constant over the observation period, with a mean concentration of 11,000
m
m
g/L
(Spinnler et al.,
2001
).
10.5.3 MC-100 (California, USA)
Equilon reported a full-scale treatment system at a retail service station site in California,
using a biobarrier that was 150 ft (46 m) long. This application used pulsed oxygen injections in
order to create an aerobic zone. Five gallons (19 L) of microbe suspension (MC-100) was
injected at 3, 5, 7 and 9 ft bgs. Injection points were located at 2-ft (0.7-m) intervals. Difficulties
in homogeneous distribution of oxygen and organisms were encountered due to tight site soils,
and additional injections were necessary in some locations (Gaarder,
2001
).
Evaluation of the mean of biobarrier well concentrations revealed ~99% reduction of
MTBE concentrations within 6 months. Although there was no control, the project demon-
strated that MTBE degraders could be readily injected and a successful MTBE biobarrier could
be established even in relatively tight subsurface materials.
10.5.4 Propane Oxidizing Bacteria (Camden, New Jersey, USA)
A full scale propane-oxidizing bacteria augmentation study was performed by Shaw
Environmental, Inc. at a retail gas station in Camden, New Jersey. This technology incorporated
the introduction of constant-sparge air (at 13 cfm), propane (0.5 lbs per day, or approximately
0.2 kg per day), propane-oxidizing bacteria (a single seeding of 17 L at ~10
11
cells/mL)
R. ruber
ENV425), and additions of 120 gallons, or roughly 450 L of sodium bicarbonate into the
impacted zone. MTBE concentration reductions of 85% (to below 70
m
g/L) were reported
over 5 months of operation by the vendor.
10.6 LESSONS LEARNED
The results from the bioaugmentation applications performed between 1998 and 2004 have
provided several valuable lessons for MTBE bioaugmentation, as well as for other potential
bioaugmentation scenarios. These key lessons include:
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