Environmental Engineering Reference
In-Depth Information
1600
1400
Ks/om = 0.5
1200
Ks/om = 1.0
1000
800
Ks/om = 1.5
600
Ks/om = 2.0
400
Ks/om = 2.5
200
0
0
500
1000
Tergitol NP-15 Concentration (mg/L)
Figure 6.23
Effect of variations in values of Ks/om
on the overall distribution
coefficient.
Tergitol NP-15 that contained monochlorinated biphenyl (4-CBP). To address
the fate of both the surfactants and the chlorinated biphenyls, a series of
batch reactor experiments was performed to monitor the disappearance of
4-CBP from liquid batch cultures. The transformation experiments were
conducted in 300-ml glass culture flasks that were sterilized and coated with
4-CBP. An aqueous nutrient solution (K1 media) or solution of surfactant,
either Tergitol NP-15 or Tween 80, was added to the prepared flasks and
allowed to mix at 150 rpm for 10 to 13 h at 30˚C. Resting cells of strain NY05,
which had been rinsed three times to remove residual biphenyl, were sus-
pended in K1 media at a biomass concentration of 0.2 g/ml. Samples were
transferred from the flasks to 26-ml glass serum tubes, to which was added
sulfuric acid (2
N
H
2
SO
4
) to lower the pH to approximately 3.5 in order to
halt microbial activity. Additional sample preparation included hexane
extraction for treatments that did not contain surfactant solutions and cen-
trifugation to remove biomass, after which the samples were transferred to
glass autosampler vials for analysis by GC/ECD.
In order to confirm that the disappearance of 4-CBP was microbially
mediated, controls were included in the transformation experiments, in
which flasks, both with and without surfactant solutions, were not inocu-
lated with NY05 resting cells. These controls enabled detection of possible
abiotic influences, such as volatilization and adsorption losses, which would
appear as 4-CB degradation. Typical results of the abiotic controls, for solu-
tions of both surfactants, are presented in Figure 6.24 with the respective
surfactant solution.
The transformation of 4-CBP by strain NY05 has been shown to result
in the production of stoichiometric amounts of the corresponding chlori-
nated benzoic acid, 4-CBA. The detection of this degradation metabolite
provided additional confirmation of the microbially mediated disappearance
of 4-CB. The appearance of 4-CBA over time for a representative degradation
