United States
Environmental Protection
Agency
EPA/540/M5-90/003
February 1990
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
In-Situ Steam/Hot-Air Soil Stripping
Toxic Treatment (USA) Inc.
TECHNOLOGY DESCRIPTION: This technology
uses steam and hot air to strip volatile organics from
contaminated soil. The treatment equipment is mobile
and treats the soil in-situ without need for soil
excavation or transportation. The organic
contaminants volatilized from the soil are condensed
and collected by the process treatment train, resulting
in a small volume of concentrated organic liquid waste
for transportation, disposal, or recycle.
A process tower supports and controls a pair of hollow
augers (Figure 1) which are moved vertically through
the soil. The augers are rotated synchronously in
opposite directions during the treatment process to
break up the soil and ensure through-flow of gases.
Steam, at 400°F, and compressed air, at 275°F, are
piped through the augers to nozzles located on the
cutter blades. Heat from the injected steam and hot
air vaporizes the volatile organics, and the gas flow
carries the contaminants to the soil surface. A steel
shroud (a 10' by 6' by 7' box) covers the 7'4" by 4'
area of soil undergoing treatment. The suction port of
a blower keeps the area underneath the shroud at a
COMPRESSOR
vacuum to assist the flow of gases from the soil, and
to ensure against leakage to the outside environment.
The off-gases are pulled by the blower from the
shroud to the treatment train, where water and
organics are removed by condensation in coolers and
carbon adsorption beds. The air is filtered and
recycled to the soil by a compressor. Water is
removed from the liquid stream with a 4-stage
separator followed by batch distillation, and is then
recycled to a cooling tower. The condensed organics
are collected and held for removal and transportation.
WASTE APPLICABILITY: This technology is
designed to be used on soil contaminated with volatile
organics to a maximum depth of 30 feet. Semivolatiles
may potentially be removed by this technology.
DEMONSTRATION RESULTS: Demonstration of this
technology was conducted at the Annex Terminal site
in San Pedro, California, in September 1989 as part of
an extensive testing program. Site characterization
investigations indicated that the soil was contaminated
Organios
Treatment/
Disposal
Figure 1. Process Flow Diagram.
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with significant amounts of chlorobenzene,
trtchloroethene, tetrachloroethene, phthalates, and
other volatile and semivolatile organics. Twelve soil
blocks (7'4" by 4') were treated to 5-foot depth during
the SITE Demonstration. Pre- and post-treatment
composite soil samples were collected from 5-foot
vertical corings. Fluorescein dye was added to four
blocks to evaluate migration of contaminants from the
treated blocks. In addition, air emission monitoring
was conducted at the soil surface for potential off-gas
emissions. Extensive process operating data were
collected, such as steam and air flow rates, and
organic concentration in the gases collected in the
shroud. Laboratory activities conducted for the
Demonstration included analysis of volatile and
semivolatile organic compounds, soil physical
characteristics, and dye concentrations.
The Demonstration showed that:
" Removal efficiencies of volatile organic
compounds were greater than 90%.
* Semivolatile organic compounds were also
removed, but at a lower efficiency.
* Downward migration of compounds is not
significant.
* Fugitive emissions around the area being
treated and previously treated areas are low.
A Technical Evaluation Report describing the
complete Demonstration will be available in the Fall of
1990.
For Further Information:
EPA PROJECT MANAGER
Paul R. de Percin
USEPA
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
~ Cincinnati, OH 45268
(513) 569-7797 (FTS 684-7797)
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. Q-35
Official Business
Penalty for Private Use $300
EPA/540/M5-90/003
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