Environmental Engineering Reference
In-Depth Information
incineration because of minimal soil excavation, material handling, and
energy costs.
4.3.3 PCBs
The PCB project has been very successful in cloning genes in bacteria that
combine cometabolism of PCBs to chlorobenzoates, and the dechlorination
and mineralization of chlorobenzoates, as a growth substrate. Microbiolog-
ical, biochemical, and physiological characterization of the selected biphenyl
degraders was completed. Based on the growth on PCB mixtures, toxicity
testing, and survival in soil microcosms, a combination of two GEMs,
Rhodo-
coccus
RHA1 tfcb and
Burkholdena
K W, were the most effective for achieving
PCB degradation. The use of surfactants increased the solubility and reme-
diation rates of the contaminant. Molecular probes were developed and used
to track the bacteria in Picatinny arsenal soils and river sediments, using
both genetic and polymerase chain reaction (PCR)-based techniques. The
recombinant organisms survived in nonsterile sediment from Red Cedar
River contaminated with Aroclor 1242 and maintained degradative activity,
evidenced by reducing PCB levels by 78%.
A pilot-scale study involving three different soil loadings (low, medium,
and high solids reactors) is ongoing at ERDC. This study will evaluate the
effects of different moisture contents on PCB bioremediation and application
of GEMs, as well as determine the maximum soil loading rate optimum for
GEMs' activity to avoid or offset the subsequent costs of disposing of the
stabilized soil.
Bioremediation of PCBs is effective and offers lower energy and opera-
tions costs than other technologies, but it may take longer to remediate the
soil, and desorption kinetics may limit degradation rates.
References
Balkwill, D.L., Leach, F.R., Wilson, J.T., McNabb, J.F., and White, D.C. 1988. Equiva-
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sediments.
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Hansen, L.D., Nestler, C., and Ringelberg, D. 2000. Bioremediation of PAH/PCP
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, G.B. Wickramanayake, A.R. Gavaskar, J.T. Gibbs, and J.L. Means,
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