Chlorinated solvent contaminated soils and groundwater: field application of the solvent extraction residual biotreatment technology - Bioremediation of Recalcitrant Compounds - page 95

~28 Months Post-Flush

~25 Months Post-Flush

C7

C7

C3

C3

C4 C4

MW-512 MW-512

MW-513 MW-514

MW-513 MW-514

16000 mg/L

C2

C2 MW-505

MW-505

C1 C1

14000 mg/L

MW-506 MW-506

MW-509
MW-510
MW-511

MW-509
MW-510
MW-511

12000 mg/L

MW-507 MW-507

10000 mg/L

8000 mg/L

6000 mg/L

~31 Months Post-Flush

4000 mg/L

2000 mg/L

0 mg/L

C7

C3

C4

MW-512

MW-513 MW-514

C2

MW-505

C1

MW-506

MW-509
MW-510
MW-511

MW-507

Figure 5.13 Ethanol contour plots over the groundwater monitoring period (12,000
mg/l = 260 m M = 1.2%).

C1, C2, and C3 showed an increase in ethanol concentrations over this same
period. The contour plots of the PCE data show dramatically decreasing
concentrations in the groundwater over the monitoring period (Figure 5.15
to Figure 5.17).
TCE and cis-DCE concentrations, which are daughter products that form
by dechlorination of PCE, increased in the groundwater following the cosol-
vent flushing test. Prior to the introduction of ethanol to the subsurface,
concentrations of TCE and cis-DCE were extremely low. TCE concentrations
increased in all wells during the first 19 months of monitoring up to as high
as 15 mg/l and then decreased to relatively low concentrations (<4 mg/l)
(Figure 5.18). Prior to the cosolvent flushing test, cis-DCE was detected in
the C-wells at concentrations of up to 50 μg/l and in MW-511 at 250 μg/l,
whereas the other IW-, RW-, and MW-wells contained none to less than 20
μg/l. After 6 months, significant cis-DCE concentrations (up to 4 mg/l) had
formed in the area of the cosolvent extraction and immediately downgradi-
ent. After 19 months, significant cis-DCE formation (>10 mg/l) was detected
in the farther downgradient MW- and C-wells (Figure 5.19). Contour plots
of the TCE and cis-DCE concentrations over time give a good visualization
of the daughter product formation at the site (Figure 5.20 to Figure 5.25).
Groundwater samples were also analyzed for the isomers of cis-DCE,
trans-1,2-DCE, and 1,1-DCE. These compounds were detected at low levels
and made up less than 10% of the DCE analyzed. This ratio is indicative of
biological transformations that seem to favor cis-DCE as the predominant
product under most conditions.
Vinyl chloride was not detected in any groundwater samples
collected from the site during the monitoring period. Vinyl chloride is the