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Phytoremediation Technology: A Growing Field
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| A
Quick Look |
| An aesthetically pleasing,
passive cleanup technology powered by solar energy. |
| A technology that is most
useful at sites at which shallow, low levels of contamination are
present. |
| A cost-effective technology
that has the potential to clean up a wide variety of brownfields sites.
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| Can also be used for other
functions related to site cleanup, such as erosion control and runoff
control. |
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Phytoremediation includes the use of plants and natural processes to
remediate or stabilize hazardous wastes in soil, sediments, surface water,
or groundwater. By acting as filters or traps, plants can degrade organic
pollutants, extract metal contaminants, or contain and stabilize the movement
of contaminants. Phytoremediation first was tested actively at waste sites
in the early 1990s, and use of the approach has been increasing. Phytoremediation
has been implemented on a full or demonstration scale at more than 200
sites nationwide. As the number of projects grows, new information about
the cost and performance of phytoremediation will become available.
Phytoremediation provides many advantages because it has the potential
to work at a broad variety of sites and on myriad contaminants involving
potentially less costs than other options. Types of sites at which phytoremediation
has been applied with some degree of success in cleaning up the sites
include pipelines, industrial and municipal landfills, agricultural fields,
wood treatment sites, military installations, fuel storage tank farms,
army ammunition plants, sewage treatment plants, and mining sites.
Phytoremediation is being tested and evaluated for its effectiveness
in treating a wide array of contaminants found at brownfields sites. Current
results indicate that plants have the potential to enhance remediation
of petroleum hydrocarbons, BTEX, polycyclic aromatic hydrocarbons (PAH),
PCBs, chlorinated solvents, heavy metals, and pesticide waste. In addition
to providing a long-term solution, phytoremediation is an excellent option
for providing an interim solution for containing the spread of contaminants
and beginning the treatment process. Phytoremediation does not require
the excavation of soil, and its application may require only minimal material
handling. Further, phytoremediation can have a positive effect on the
aesthetic character of a site, may be an attractive alternative for use
at large sites at which other methods of remediation are not cost-effective
or practical, and can be used in conjunction with other technologies when
the redevelopment and land use plans for the site include the use of vegetation.
Decision-makers at brownfields sites at which there are relatively low
concentrations of contaminants (that is, organics, nutrients, or metals)
over a large cleanup area and in shallow soils, streams, and groundwater
should consider the use of phytoremediation. Phytoremediation also may
be considered for use in conjunction with other technologies when redevelopment
and land use plans for a site include the use of vegetation. Among the
types of plants used for phytoremediation are hybrid poplar, willow, and
cottonwood trees; rye, Bermuda, sorghum, and fescue grasses; legumes (clover,
alfalfa, and cowpeas); aquatic and wetland plants (water hyacinth and
bullrush); and hyperaccumulators for metals (such as alpine pennycress
for zinc or alyssum for nickel). If levels of contamination are so high
that the concentrations of contaminants are toxic to plants (phytotoxic),
phytoremediation may not be an effective treatment option.
Because phytoremediation has been used more frequently on a demonstration-scale
basis, site owners may find it necessary to show its potential applicability
and efficacy on a site-specific basis. Doing so may require an up-front
commitment of time and resources to demonstrate that the performance of
phytoremediation is comparable to the performance of traditionally accepted
technology options. However, such an investment ultimately could save
site owners significant amounts of money when they clean up their properties
for redevelopment. In recent years, EPA has compiled new information to
assist site decision-makers who may be reluctant to use phytotechnology
because of the limited amount of information about its use at actual field-scale
projects. In a recent paper, Use of Field-Scale Phytotechnology for
Chlorinated Solvents, Metals, Explosives and Propellants, and Pesticides
STATUS UPDATE (April 2005), EPA provides information on phytotechnology
applications and identifies such examples as the Edward Sears property
that was used from the mid-1960s to the early 1990s for the repackaging
and sale of paints, adhesives, paint thinners, and various military surplus
materials. Groundwater at the site was contaminated with a variety of
solvents, including methylene chloride, trimethylbenzene, TCE, and xylenes.
A field demonstration of phytotechnology using hybrid poplars to clean
up shallow groundwater at the site was performed beginning in 1996. Substantial
reductions in contaminant concentrations have been reported. For example,
data covering the period from 1995 to 2004 shows that concentrations of
methylene chloride was reduced from as high as 6,700 ìg/L to below detection;
trimethylbenze from as high as 1,890 to 730 ìg/L; and TCE from as high
as 510 to 46 ìg/L. Groundwater monitoring is ongoing at the site.
In addition to the document discussed above, other resources are available
at www.epa.gov/tio/pubitech.htm
including:
- Brownfields Technology Primer: Selecting and Using Phytoremediation
for Site Cleanup (EPA 542-R-01-006), July 2001
- Phytoremediation Resource Guide (EPA 542-B-99-003), June 1999
For more information see the following resources:
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Sunday, September 7, 2008
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