Environmental Engineering Reference
In-Depth Information
exudate appears to favor selection of microorganisms that degrade the con-
taminant.
Plants can be incorporated into current treatment strategies in several
ways. The most recent development is an alternative agricultural technique,
plant-based biotechnology. The goal of this “molecular farming” is to pro-
duce large quantities of root exudate to be used as a soil amendment. As
these exudates vary between species and soil conditions, a systematic study
needs to be undertaken before this technology is feasible.
The most promising method of incorporating phytoremediation into soil
PAH remediation is to develop a new paradigm of treatment that utilizes
rhizospheric degradation as part of a treatment train. Once contaminated
soil has been treated by land farming, for example, a plant cover would be
established. The advantages are:
•
Plant cover reduces both wind and water erosion from the treated
soil.
•
The improved soil structure allows continued bioremediation.
•
Naturally occurring nitrogen-fixing microorganisms reduce the need
for chemical fertilizers, reducing costs.
•
The roots establish an optimal environment and furnish energy for
growth of microorganisms.
•
The exudate contains oxidative enzymes that contribute to PAH deg-
radation.
Current research indicates that the establishment of plants on contami-
nated sites may be an economic, effective, low-maintenance approach to
complete soil PAH remediation.
8.3 Chlorinated solvents
The Solvent Extraction Residual Biotreatment (SERB) technology developed
here has been specifically targeted for contamination at sites containing
separate phase dense nonaqueous phase liquids (DNAPLs). Molecular
probes for two microorganisms capable of reductive dechlorination of chlo-
roethenes have been developed. The experience over the last two decades
with recalcitrant compounds suggests that there are perhaps many more
microorganisms in nature capable of reductive dechlorination that have so
far not been discovered. The techniques developed and described here can
be used to continue to search for such potential microorganisms and for their
isolation, cultivation, and monitoring.
Since chloroethenes are still commonly used, the potential for fresh spills
and environmental contaminations exists. These being mostly man-made
chemicals, the fresh sites are not likely to possess extensive dechlorination
capability. In such cases, it may be desirable to deliver known dechlorinators
in the environment. In order to ensure successful introduction of the
microbes in the surface and confidently utilize the SERB technology, it is
