Environmental Engineering Reference
In-Depth Information
A
Mix M
200
150
100
50
0
1234
567
B
200
150
100
50
0
0
Mix M + NY05
NY05
200
150
100
50
0
6
12
Time, h
18
24
1234
567
200
150
100
50
0
0
Mix M + RHA1
RAH1
200
150
100
50
0
6
12
Time, h
18
24
1234
567
200
150
100
50
0
0
Mix M + LB400
LB400
200
150
100
50
0
6
12
Time, h
18
24
1234
567
Figure 6.7
Degradation of
m
ix M by three BP degraders.
ring. From 70 to 95% of depleted chlorobiphenyls were recovered as chlo-
robenzoates. In the only comparable investigation, albeit using much lower
concentration of PCBs,
Alcaligenes eutrophus
strain H850, also an
ortho-directed strain (Bedard et al., 1987a), was reported to deplete 81% of
Aroclor 1242 anaerobic dechlorination products in Hudson River sediments
(10 ppm, pattern C). The production of chlorobenzoates was not monitored
in that work (Bedard et al., 1987b).
These experiments showed that degradation of several congeners is
affected when PCBs supplied in complex mixtures, primarily less efficient
degradation of 2,4,4-CB, 2,2-CB, and 2,6-CB. Strains LB400 and RHA1 with
preference toward hydroxylation of ortho-chlorinated biphenyl ring
appeared more efficient PCB degraders compared to NY05 with preference
toward para-chlorinated ring. We have identified several intermediate prod-
ucts of aerobic PCB oxidation with potential biotoxic effects, among them
meta-cleavage products; chlorinated HOPDAs and dihydrodiols and mono-
and dihydroxybiphenyls. The amount of (Cl)HOPDA produced by
