United States
Environmental Protection
Agency
Solid Waste And
Emergency Response
(OS-220)
Directive 9200.5-251FS
November 1989
&EPA Innovative Technology
In-S'rtu Vitrification
TECHNOLOGY DESCRIPTION
In-situ vitrification (ISV) can be used
to treat soils and sludges contaminated with
mixtures of various waste types (e.g., radio-
active, inorganic, and/or organic). The pro-
cess electrically melts the waste media, cre-
ating an extremely stable glass-like solid.
A schematic diagram of a typical ISV
treatment facility is shown in Figure 1. Four
electrodes connected to a utility distribution
system or to an on-site diesel generator are
over the process area collects both organic
and inorganic gases, which are treated be-
fore being released into the atmosphere. An
off-gas treatment system is designed to
handle conditions at most sites. If necessary,
the treatment system may be modified to
meet specific site requirements. The off-gas
treatment may include any of the following
units: a wet scrubber system, a heat ex-
changer with a glycol cooling system, a
heater, a filter, and/or an activated charcoal
assembly. The hood draws in large amounts
Figure 1: Schematic Diagram of a Typical In-SItu Vitrification
Treatment Facility
To Treatment
Note. adapted Irom Banana Pacific Northeast Laboratories, tor 8002. Allan & Hamrton Inc
inserted into the soil. Because soil typically
has low electrical conductivity, flaked graph-
i te and glass frit are deposited between elec-
trodes to provide a starter path for the elec-
trical current. As the current flows between
electrodes, the adjacent soil is heated to
1600 - 2000°C, well above a typical soil's
melting temperature. The graphite starter
path eventually burns off and the current is
transferred to the now highly conductive
melted soil.
Within the melt, organic contaminants
are vaporized and pyrolyzed (i.e., thermally
decomposed); the pyrolysis products rise to
the surface and combust in the presence of
oxygen. Non-volatile inorganic elements
are dissolved or incorporated into the melt.
volatile metals may vaporize and rise to the
surface along with the pyrolysis products.
Table 1 lists the effectiveness of ISV on
general contaminant groups.
A negatively pressurize-d hood placed
of outside air which helps to oxidize com-
bustible vapors and pyrolysis products. All
equipment involved with the ISV process,
including the off-gas treatment system, are
contained in three mobile trailers.
When the treatment is completed, the
power is shut off and the equipment (i.e.,
electrodes and hood) is moved to another
treatment area where the treatment process
is repeated. Following treatment, the sur-
face of the vitrified area is covered with
clean soil, and the melt is allowed to cool
slowly, producing an amorphous solid re-
sembling obsidian. Several months are
required for the treated area to cool to ambi-
ent temperature; however, after four to five
days, the melt has cooled sufficiently for
equipment to be moved onto the treated area.
The advantages of ISV include the
potential ability to destroy, remove, or
immobilize all contaminant groups and to
reduce the volume of the waste/mediabeing
treated. The need for off-gas collection and
treatment, however, is a disadvantage.
SITE CHARACTERISTICS AFFECTING
TREATMENT FEASIBILITY
Generally, the acceptable levels for
treatment of contaminants in soil are 5 to 10
weight percent organics and 5 to 15 weight
percent inorganics. Due to the need to con-
sider several other factors (e.g., soil type) in
determining feasibility, treatability tests are
required.
The ISV process can be used to treat
saturated soils; however, the water must be
evaporated first, requiring additional energy
and further expense. If the soil permeability
is high and the soils are recharged by an
aquifer, a ground water diversion system
may need to be installed, adding additional
expense.
Table 1
Effectiveness of In-Situ Vitrification
Treatment on General Contaminant
Groups for Soil and Sludge
Treatability Groups
O
Inorganic*
Rcactlv*
Halogenated volatiles
Halogenated semi-volatiles
Non-halogenated volatiles
Non-halogenated semi-volaules
PCBs
Pesiicides
Dioxins/Furans
Organic cyanides
Organic corrosives
Volatile metals
Non-volatile metals
Asbestos
Radioactive materials
Inorganic corrosives
Inorganic cyanides
Cbudizers
Reducers
Effectiveness
e
Q
o
o
Q
e
o
Q
Ol
o
Q
O
•
o
Q
Q
o
D«*TXjnsJrai*d EfiecOveness
No Expeded EflecSverwss
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The presence of significant amounts of buried metals (e.g.,
drums) may cause shorting between electrodes, therefore, the metal
concentration limit is 5 to 16 percent of the melt weight. Addition-
ally, metals cannot occupy more than 90 percent of the continuous
lir ear distance between electrodes. Table 2 lists those factors that
affect ISV feasibility.
TECHNOLOGY CONSIDERATIONS
Currently, IS V technology can be used to treat amaximum area
of 30 ft. x 30 ft.; the maximum depth of treatment is 30 ft Note that
the maximum mass of contaminated material that can be treated per
setting is 800 to 1,000 tons. When processing a 30 ft x 30 ft. area,
the mass limit will be reached before the depth reaches 30 ft.; con-
sequently, it is impossible to reach all three maximums simultane-
ously. Conversely, the minimum area that can be treated is 10 ft. x
10 ft.; the recommendeen postponed until the developer has obtained funding for a dem-
onstration at an appropriate site.
Currently, EPA's Emergency Response Division in Region 5
Table 3
Vendor Information
Table 2
Site-specific Characteristics and Impacts on In-Sttu
Vitrification Treatment
Company
Geosafe Corporation
Contact
James Hansen
Dale Timmons
Address
303 Parkplace Suite 126
Kirkland, WA 98033
(206) 822-4000
Note: Geosafe Corporation is the exclusive commercial sublicensee of
the ISV process.
Characteristics
Impacting Process
Feasibility
Presence of ground water
Soil permeability greater
than 1 x 10'5cnVsec
Buried metals (e.g., drums),
greater than 5 to 1 5 percent
of the melt weight between
electrodes
Loosely packed rubbish
and/or buried coal
Combustible liquids, greater
than 9,600 Ib/yd of depth or
5 to 10 percent by weight
Combustible solids (e.g.,
wood), greater than
6.400 Ib/yd of depth or
4.7 percent by weight
Combustible packages
(e.g., boxes of clothing
packaged lor disposal),
greater than 32 It3
Volatile melal content and
depth
Void volumes greater than
152ft3
Reasons for
Potential
Impact
Water affects the efficiency of
the vitrification process, limits
economic practicality
Soil is re-saturated faster than
water can be evaporated
Buried metals can result in a
conductive path that would
lead to shorting between
electrodes
May start underground fire
Time-oitdared limits to the
capacity of the off-gas system
to contain combustion gas,
(not cumulative capacity)
Time-ordered limits to the
capacity of the off-gas system
to contain combustion gas,
(not cumulative capacity)
Time-ordered limits to the
capacity of the oil-gas system
to contain combustion gas,
(not cumulative capacity)
Retention of volatile metals in
melt is less near surface than
further below
Time-ordered limits to the
capacity of the off-gas system
to contain combustion gas,
(not cumulative capacity)
Actfonsto fl
Minimize ; ^
Impacts
Oewater before treatment
or pump to lower water
table
Install ground water
diversion system
Use feeding electrodes
Install barrier walls or
sheet piling
Increase hood capacity,
process at a slower rale,
or employ smaller process
setting volumes
Increase hood capacity,
process at a slower rate.
or employ smaller process
setting volumes
Increase hood capacity,
process at a slower rate,
or employ smaller process
setting volumes
Before treatment, place]
dean soil on top to
increase melt depth
Increase hood capacity,
process at a slower rate,
or employ smaller process
setting volumes
has selected ISV to treat pesticides, heavy metals, and low-level
dioxins. ISV has also been selected to treat contaminated soils at the
Ionia Landfill in Region 5 and the Northwest Transformers site in
Region 10. The status of ISV application at CERCLA sites is sum-
marized in Table 4.
OFFICE OF RESEARCH AND DEVELOPMENT CONTACTS
Further information regarding the IS V process may be obtained
from Steve James, U.S. EPA, Risk Reduction Engineering Labora-
tory, Cincinnati, Ohio 45268. (513) 569-7877 or FTS (684-7877).
Table 4
In-Situ Vitrification Status at CERCLA Sites
SELECTED:
Region 5 -Ionia Landfill, Ml 9/89
Region 5 - Parsons/ETM, Ml
(Removal Action) FY90
Region 10 - Northwest Transformers,
WA9/89
Heavy metals, organics in
Soil
Pesticides, heavy metals.
low-level dioxins in Soil
PCBsinSoil
5000 cubic
yards
NotProvida
Not Provided
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