A
demonstration of Six-Phase Heating (SPH) was conducted at NASA’s
Launch Complex 34 groundwater cleanup site on Cape Canaveral Air Force
Station. The site geology consists of several
stratigraphic units containing layered, heterogeneous lithology with
permeability contrasts of two orders of magnitude. The purpose of the
demonstration
was to test the effectiveness of SPH at remediating trichloroethylene
(TCE) as a dense nonaqueous-phase liquid (DNAPL).
SPH passes an electrical current through the soil and groundwater
that require treatment. The electrical current warms the soil
and then boils
a portion of the soil moisture (typically 10 to 20 percent by volume)
into steam. This in situ steam generation occurs in all soil types,
regardless of permeability. Electricity evaporates the target
contaminant and provides
steam as a carrier gas to sweep the volatile organic compounds (VOC’s)
to recovery wells. After the steam is condensed and the extracted air
is cooled to ambient conditions, the vapors are treated using conventional
vapor treatment methods. Because in situ steam generation is governed
by
the passage of electrical current (not the fluid flow within the soil
matrix), SPH remediation is not significantly affected by low-permeability
or heterogeneous
soils.
The SPH design employed at Launch Complex 34 included preferentially
heating the deep sections of the site’s aquifer and then sweeping
TCE upward into the vadose zone for extraction and treatment on the surface
using
granular activated carbon (GAC). This process worked effectively at the
site until two intense storms virtually eliminated the vadose zone (more
than 4 feet of vadose zone lost to rainwater infiltration) where TCE
extraction was occurring.
After several system shutdowns, the system did run continuously for
several months, removing 90 percent of the TCE from the demonstration
plot.
Key accomplishments:
- 2000: Field-deployed
SPH.
- 2001: Collected
postdemonstration performance data.
Key milestone:
- 2002: Cost and performance
data evaluation.
Contact: Dr. J.W. Quinn (Jacqueline.Quinn-1@ksc.nasa.gov), YA-C3-C,
(321) 867-8410
Participating Organizations: Thermal Remediation Services
(G. Beyke) and Current Environmental Solutions (B. Heath)
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