Environmental Engineering Reference
In-Depth Information
OK) at 500 ml/l, distilled water at 500 ml/l, and (NH
4
)
2
HPO
4
at 1.32 g/l,
and this supplied the basic nutrients to the sample's microbial community.
Different concentrations of ethanol, ranging from 0.05 to 70% v/v, were used
for the study. Anaerobic microcosms were prepared in a glove box with a
nitrogen-hydrogen atmosphere, and the aerobic microcosms were prepared
in a laminar flow hood. Samples from each microcosm were withdrawn at
regular intervals to determine the degradation of added ethanol. Degrada-
tion of ethanol was expressed in terms of attenuation rates of ethanol and
was measured with different electron acceptors (O
2
, NO
3
-
, SO
4
2-
, and PCE)
and different stressor levels. Exposure time to the stressor for the different
microcosms was also varied and can be divided into two groups: (1)
long-term exposure and (2) transient exposure. Spent microcosms were fro-
zen and sent for PLFA analysis.
5.4.2 Field studies
5.4.2.1 Groundwater sampling and analysis
Groundwater samples were collected prior to the implementation of the
cosolvent extraction technology to provide background conditions. Follow-
ing the cosolvent extraction test, groundwater samples were collected and
analyzed quarterly over a 2
1
/
2
-year period for nutrients, chloroethenes, eth-
anol, dissolved gases, and volatile fatty acids.
Samples for ethanol and alcohol tracer analysis and for PCE and daugh-
ter product analysis were collected in 40-ml volatile organic analysis (VOA)
vials without headspace. The alcohol compounds were separated by gas
chromatography on a DB624 capillary column and detected with a flame
ionization detector. Chlorinated compounds were analyzed by
purge-and-trap gas chromatography, which utilized a 0.32 mm × 60 m
RESTEK Rtx-Volatiles column for separation and a flame ionization detector
for detection.
Samples for chloride and sulfate analysis were collected in 100-ml poly-
ethylene bottles and analyzed using Waters capillary electrophoresis method
N-601. Samples for nitrate, phosphate, and dissolved organic carbon analy-
ses were collected in 100-ml polyethylene bottles and preserved with con-
centrated sulfuric acid. Nitrate and phosphate were analyzed using a Lachat
system. Dissolved organic carbon samples were analyzed with a Dohrman
Carbon Analyzer.
Subsamples for volatile fatty acid analysis were collected from the 100-ml
nonacidified polyethylene bottle described above. These samples were ana-
lyzed by high-performance liquid chromatography (HPLC) with a Dionex
system utilizing a Dionex ICE-AS1 IonPac column and AMMS-ICE
MicroMembrane Suppressor. A Waters 431 conductivity detector was used
for analyte detection.
Dissolved gas samples were collected in 100-ml glass serum bottles
without headspace and sealed with Teflon-lined septa and crimp caps.
