Environmental Engineering Reference
In-Depth Information
~25 Months Post-Flush
~22 Months Post-Flush
C7
C7
C3
C3
C4
C4
MW-512
MW-512
MW-513
80 mg/L
MW-513
MW-514
MW-514
C2
MW-505
C2
MW-505
C1
C1
70 mg/L
MW-506
MW-506
MW-509
MW-510
MW-511
MW-509
MW-510
MW-511
60 mg/L
MW-507
MW-507
50 mg/L
40 mg/L
~28 Months Post-Flush
~31 Months Post-Flush
30 mg/L
20 mg/L
10 mg/L
C7
C7
0 mg/L
C3
C3
C4
C4
MW-512
MW-512
MW-513
MW-513
MW-514
MW-514
C2
MW-505
C2
MW-505
C1
C1
MW-506
MW-506
MW-509
MW-510
MW-511
MW-509
MW-510
MW-511
MW-507
MW-507
Figure 5.42
Sulfate contour plots over the groundwater monitoring period (80 mg/l =
833 μ
M
).
5.5.3 Microbial ecology assessment
The only known pure culture that is capable of complete reductive dechlo-
rination of PCE to ethene is the obligately hydrogenotrophic organism
Deh-
alococcoides ethenogenes
. Hydrogen is generally considered the ultimate elec-
tron donor to stimulate the reductive dechlorination of chloroethenes.
Dsulfuromonas
sp. strain BB1 is a dechlorinator that utilizes acetate as an
electron donor to support the reductive dechlorination of PCE and TCE.
Löffler et al. (2000) developed 16S rDNA-based PCR methods for detection
of PCE-dechlorinating
Dehalococcoides
sp. and
Dsulfuromonas
sp. strain BB1
and evaluated their presence in environmental samples.
Aquifer materials collected during installation of MW-510 and IW-001
were utilized in their study along with environmental samples from other
sites. The MW-510 sample resulted in visible amplification in the initial PCR
with the universal primers. Nested PCR with the
Dehalococcoides
-targeted
primers yielded a positive signal with the MW-510 sample.
Microcosm studies conducted with the aquifer materials confirmed the
results obtained with the molecular approach. MW-510 microcosms were the
only aquifer material-based microcosms that indicated the presence of a
hydrogenothrophic PCE-dechlorinating population. Vinyl chloride and
ethene accumulated in the hydrogen-fed microcosms, whereas ace-
tate-amended cultures showed only negligible dechlorination (Löffler et al.,
2000).
The results of the molecular analysis and microcosm studies support the
data from the Sage's site that indicates complete reductive dechlorination of
PCE to ethene. Additional samples collected prior to the cosolvent extraction
