Environmental Engineering Reference
In-Depth Information
5
4
3
Control
Silver Lake Inoculum
Hudson River Inoculum
Hudson River & Silver Lake Inocula
Silver Lake, then Hudson River Inocula
2
1
0
10
20
30
40
50
60
Incubation Time (Weeks)
Figure 6.3
Extent of Aroclor 1260 dechlorination obtained using mixed and sequen-
tial inoculations with Hudson River and Silver Lake microorganisms.
experiment are depicted in Figure 6.3. The progress of Aroclor 1260 dechlo-
rination in various treatments is compared by plotting the average number
of chlorines remaining in the meta- or para-positions vs. time. The most
extensive dechlorination occurred with sequential inoculations with Silver
Lake sediments, followed by Hudson River microorganisms.
Process N microorganisms in Silver Lake sediments are much more
effective in dechlorinating the heavily chlorinated congeners in Aroclor 1260
than are the microorganisms in Hudson River sediments, which are mainly
process M and Q microorganisms. The extent of dechlorination achievable
by Silver Lake microorganisms alone is limited because process N removes
only flanked meta-chlorines. Hudson River microorganisms (M and Q
together), however, have the potential to remove all meta- and para-chlo-
rines, whether or not there is an adjacent chlorine.
Combined activities could not be achieved by simply mixing micro-
organisms from the two sediments apparently because of incompatibility,
but we were able to achieve enhanced activity through sequential inocula-
tions, first with Hudson River microorganisms and then with Silver Lake
microorganisms. A possible explanation can be gleaned from examining the
chromatographic profiles of the PCBs generated in the various treatments
(Figure 6.4). The profiles for Hudson River microorganisms alone and mixed
with Silver Lake microorganisms are similar, and indicate that dechlorination
was limited to the meta-positions. In other words, process Q or para-dechlo-
rination activity was lost, and even N activity was diminished. The profile
for Silver Lake microorganisms alone indicates that high levels of ortho- and
para-substituted congeners, notably 24-26-CB (peak 21), 24-24-CB (peak 26),
and 246-24-CB (peak 34), were formed. These congeners could serve as a
substrate for process Q microorganisms in the subsequent inoculation with
Hudson River microorganisms. It is possible that the accumulation of these
congeners even selected for, or primed, this para-dechlorination activity. In
