Drip Irrigation Aided Phytoremediation for Removal of TCE from Groundwater Page: 2 of 9
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DRIP IRRIGATION AIDED PHYTOREMEDIATION FOR REMOVAL OF TCE
E.W. Wilde (email@example.com), R.L. Brigmon, C.J. Berry, D.J. Altman, J. Rossabi, and
S.P. Harris (Westinghouse Savannah River Company, Aiken, SC)
L.A. Newman (Savannah River Ecology Laboratory, Aiken, SC)
ABSTRACT: Groundwater in D-Area at the Savannah River Site (SRS) is contaminated
with trichloroethylene (TCE) and by-products resulting from discharges of this organic
solvent during past disposal practices. This contaminated groundwater occurs primarily at
depths of 9 m to 15 m below ground surface, well below the depths that are typically
penetrated by plant roots. The process investigated in this study involved pumping water
from the contaminated aquifer and discharging the water into overlying test plots two
inches below the surface using drip irrigation. The field treatability study was conducted
from 8/31/00 to 4/18/02 using six 0.08 ha test plots, two each containing pines,
cottonwoods, and no vegetation (controls). The primary objective was to determine the
overall effectiveness of the process for TCE removal and to determine the principal biotic
and abiotic pathways for its removal. Results demonstrated that the process provides a
viable method to remove TCE-contaminated groundwater. The data clearly showed that
the presence of trees reduced volatilization of TCE from the drip irrigation system to the
atmosphere. Influent groundwater TCE concentrations averaging 89 [g/L were reduced
to non-detectable levels (<5 [g/L) within the upper two feet of soil (rhizosphere).
Phytoremediation is an emerging technology that utilizes plants and associated
microbes to remediate contaminated media. Previous studies at the Savannah River Site
(SRS) demonstrated degradation of low concentrations of chlorinated solvents by plants
and associated rhizosphere microorganisms (Anderson et. al., 1993). D-Area at SRS has a
large dilute groundwater plume of TCE (mostly <100 [g/L) that is close to the Savannah
River. Most of the TCE-contaminated groundwater occurs near the bottom of an
approximately 9-15 m thick aquifer, well below the depth of typical tree root penetration.
Thus, the drip irrigation component of the proposed process provided a means to allow
plant and associated microbial communities an opportunity to remediate contaminated
groundwater from depths otherwise unavailable to plant systems. The overall objective of
this project was to evaluate a novel drip irrigation-phytoremediation process (Figure l) for
remediating volatile organic contaminants (VOCs), primarily trichloroethylene (TCE),
from this contaminated groundwater. The process has the potential to be less expensive
and more beneficial to the environment than traditional TCE remediation technologies. It
could safely reduce plumes of TCE in D-Area groundwater to below drinking water
standards (<5 [g/L), while facilitating the growth of plants that can be used in timber
production. The removal of TCE is effectuated by both abiotic (adsorption, absorption,
volatilization) and biotic (phytoremediation) pathways. The phytoremediation pathways
involve three mechanisms: (1) rhizodegradation, or the breakdown of organic
contaminants by microbial activity enhanced by the presence of plant roots, (2)
phytodegradation, the breakdown of contaminants by plant metabolic processes, and (3)
transrespiration, physical processes including volatilization and transpiration. The project
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Wilde, E.W. Drip Irrigation Aided Phytoremediation for Removal of TCE from Groundwater, article, April 24, 2003; South Carolina. (digital.library.unt.edu/ark:/67531/metadc740791/m1/2/: accessed March 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.