Well Injection Depth Extraction
(WIDE) System
Description
The
Well Injection Depth Extraction (WIDE) system is a hybrid soil flushing/soil
vapor extraction system that uses Prefabricated Vertical Wells (PVWs) in lieu of
conventional wells or sumps to extract groundwater and inject liquid
flushing agents. The PVWs are installed at relatively close spacing (less than
3 feet apart) to shorten groundwater drainage paths and accelerate the soil
flushing process. Surface treatment, such as Air
Stripping,
Granular Activated Charcoal (GAC), and Ion
Exchange
are used to treat extracted groundwater and soil gas.
The
WIDE system has successfully extracted trichloroethylene
(TCE),
uranium (U), and technetium-99 (99Tc) from the subsurface. Under
extraction-only operation, volatilizing TCE from the soil
enhanced TCE removal.
Injection
of liquids through PVWs, with concurrent extraction, was found to increase
groundwater extraction flow rates and enhance the removal of dissolved contaminants.
Limitations
and Concerns
The
WIDE technology is predominantly a shallow depth (less than 30 feet)
remediation system. Although wells can be installed to depths greater than 90
feet, vacuum extraction of liquids is limited in practice to depths of
approximately 30 feet.
At
the Ashtabula site, the system experienced icing problems at temperatures below
30 degrees F.
When
the system is used to extract dissolved contaminants by flushing, there is
concern that the system will merely dilute the contaminant without extracting
it from the groundwater. Thus robust
monitoring is needed during operation.
Applicability
The
technology is adapted for use in tight soils such as fine clay. This system is
a removal enhancement. It has been field tested for the removal of dense
nonaqueous phase liquids (DNAPLs), light
non-aqueous phase liquids (LNAPLs), and dissolved contaminants such as uranium in
soil and groundwater.
Technology
Development Status
Researchers
from North Carolina State University developed the WIDE system. The Department
of Energy has stated that the system is ready for deployment and commercial
application.
Web
Links
http://www.netl.doe.gov/publications/proceedings/99/99em/quaranta.pdf
http://www.clu-in.org/download/contaminantfocus/dnapl/Treatment_Technologies/DOE-EM-0577.pdf
Other
Resources and Demonstrations
The
WIDE system was demonstrated at a DOE uranium manufacturing site in Ashtabula,
OH. The groundwater and soils are contaminated with TCE, U, and 99Tc as a result
of long-term uranium manufacturing operations. The field-scale demonstration of
the WIDE system included a grid of over 480 PVWs installed to a depth of 15 ft.
The system used vacuum extraction to remove the TCE-contaminated groundwater
and soil gas, which in turn was treated in an above-ground treatment system.
The siteÕs existing wastewater treatment plant was used to treat the
radioactive constituents.
See
http://www.netl.doe.gov/publications/proceedings/00/ind_part00/quaranta.pdf.