Environmental Engineering Reference
In-Depth Information
80
Fluoranthene + Rhamnolipid
Fluoranthene + Triton X-100
Phenanthrene + Rhamnolipid
Phenanthrene + Triton X-100
Pyrene + Rhamnolipid
Pyrene + Triton X-100
Benzo[a]pyrene + Rhamnolipid
Benzo[a]pyrene + Triton X-100
Chrysene + Rhamnolipid
Chrysene + Triton X-100
60
40
20
0
0
10
20
30
40
Surfactant Concentration (X CMD)
Figure 7.8
The solubilization of PAHs (n = 3) by
P. aeruginosa
strain 64 rhamnolipid
and by Triton X-100.
The solubilization of phenanthrene, fluoranthene, pyrene, chrysene, and
benzo(a)pyrene by rhamnolipid and Triton X-100 is shown in Figure 7.8. The
difference in effectiveness between rhamnolipid and Triton X-100 for
phenanthrene became less obvious when other PAHs were examined. The
ability of each surfactant to solubilize each PAH is directly correlated with
the size of the PAH. The four- and five-ring PAHs were poorly solubilized
with either surfactant.
7.2 Objectives
Land farming of hydrocarbon-contaminated soils may provide a cost-effec-
tive alternative to other methods of contaminant removal. However, the
HMW PAHs have been found to be resistant to biodegradation in these
systems. Sites that contain high levels of these compounds are especially
challenging. Data presented in this report indicate that by carefully aug-
menting the metabolic capabilities of the existing soil bacterial communi-
ties, normally insoluble compounds can be rendered more available to
these communities for degradation. These initial steps can lead to a
cost-effective means for removing these dangerous chemicals from the
environment.
Our objective was to demonstrate improved bioremediation of the more
toxic, higher-molecular-weight PAHs through land farming with bioaug-
mentation and biostimulation. The use of known surfactant-producing bac-
teria should increase the availability of PAHs in the soil to the degrading
bacterium. The use of biostimulation with bulking agents and slow-release
nitrogen will sustain microbial growth.
