United States
Environmental Protection
Agency
Solid Waste And
Emergency Response
(OS-220)
Directive 9200 5-251FS
November 1989
,EPA
Innovative Technology
In-Situ 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-
aLing 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 generaLor are
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
Effectiveness
0
Haiogonated volatfies
Hatogenated seml-volatiies
Non-halogenaied volaties
Non-haJogenaied serni-voiatiles
PCBs
Pesticides
Dioxlnslfurans
Organic cyanides
Organic corrosees
•
‘
Volatde nietals
Q
Non-volatile rneiais
Asbestos
Radioactive materials
•
inorgartic corrosives
inorganic cyanidos
T
Oxidizers
Reducers
O.monaos.d Eflect .nse No E*poct.d ES scxvenezn 0
Po ereat EffecOven.se Q Potenbaily Deti,rnental X
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
handleconditionsatmostsites. Ifnecessary,
the treatment system may be modified to
meet specific site reqwrements. 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
Nan ata ed irom aarlona Paic Northeast L oratorlas ioi Boos. Azen & HarriSon inc
inserted into the soil Because soil typically
has low electrical conductivity, flaked graph-
ite 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 bums 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 pressurized 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 tobe 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/media being

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The presence of significant amowus 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
linear distance between electrodes. Table 2 lists those factors that
affect ISV feasibility.
TECHNOLOGY CONSIDERATiONS
Currently, ISV technology can be used to treat a maximum area
of 30 ft. x 30 ft.; the maximum depth of treatment is 30 ft. Note that
the maximum mass ofcontaminated material that can be treated per
sening 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, ills impossible to reach all three maximums simultane-
ously. Conversely, the minimum area that can be treated is lOft. x
10 ft.; the recommended minimum depth of treatment is 5 to 7 ft.
Most soil types contain sufficient glass-forming materials
(e.g., silicon and aluminum oxides) for treatment to be effective;
however, it may be necessary to add a fluxing material (e.g., sodium
carbonate) to supply adequate amounts of monovalent cations to
provide sufficient electric conductivity. Dunng ISV, the soil vol-
ume decreases 20 to 40 percent necessitating the backfilling of the
subsided area with clean soil.
During full-scale operation, ISV processes 4 to 6 tons of soil
per hour, requiring 0.3 to 0.5 kwh per pound of soil. The power level
required is 1.9 Mw/phase.
The base price of a typical treatabiity study, conducted in
Geosafe Corporations laboratory, is estimated to be $25,000. Ana-
lytical costs, however, can raise the total cost to between $35,000
and $100,000.
TECHNOLOGY STATUS
Bauelle Memorial Institute is exclusively licensed by the U.S
Department of Energy (DOE) to perform ISV. Geosafe Corpora-
tion, primarily owned by Battelle, holds the exclusive sublicense to
perform ISV commercially. More information concerning Geosafe
is found in Table 3. Battelle and Geosafe have cumulatively per-
formed more than 70 tests of various scales for DOE and other
clients. At the DOE Hanford Site in Washington State, ISV success-
fully treated soils contaminated with radioactive wastes.
The ISV process has been selected for evaluation under the
SITE Program. Formal demonstration and testing of the process has
been 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
Company
Contact
Address
Geosafe Corporalon
James Hansen
DaJe Timmons
303 Parkplace Suite 126
Kirkland, WA 98033
(206) 822-4000
Notw Geosafe Corporaflon is the exdusive cemmercial sublicensee of
the ISV process
Table 2
She-specific Characteristics and Impacts on In-Situ
Vitrification Treatment
characteristics
Impacting Process
Fsa&bfllty
Reasons for
Potential
Impact
Actions to
MInimize
impacts
Presence of ground water
Waler affects the efficiency of
the vrl4rcatpon process, limits
ecorcm practicality
Oewaler before treatment
or p niip to lower water
table
Sod permeabthty greater
than 1 a 10 aTi/soc
Soil a re-eaturaled faster than
waier can be evaporated
mateS ground waler
diversion system
Buned metals (eg . drums),
grealerihan 5to 15 percent
of the rne weight between
etedrodes
Bimed metals can result in a
condictivepathihalwould
leaf to shorting between
electrodes
Use feeding electrodes
Loosely packed rubbish
and/or buned coal
May start underground Ire
Install barriar wals or
sheei piling
Combustible Iquds, greater
than 9,600 Ib/yd of depth or
5 to 10 percent by weight
lime-ordered tuna to the
capacity of the off-gas system
to contan combustion gas,
(riot cumulative capacity)
Increase hood capacity,
process at a slower rate,
or employ smaller process
setting volumes
Combustible sol (e g,
wood), greater than
6,400 Iblyd of depth or
47 perceil by weight
lime-ordered Imits to the
capacity of the off-gas system
to cordan combustion gas,
(not cumulative capacity)
mo-ease hood capacity,
process at a slower rate,
or employ smaller process
setting volumes
Combustible packages
(e g, boxes of dothing
packaged for disposai),
greater thai 3211
lime-ordered tuna to the
capacity of the on-gas system
to conan combustion gas,
(net cumulative capacity)
Increase hood capacity,
process at a slower rate,
or employ smaller process
setting volumes
Volatile metal content and
depth
Relent’on 01 votalle metals in
meftislessnearsurfacathan
further below
Before treatment, place
cleansodontopto
increase met depth
Void volumes greater than
152ft 3
lime-ordered Imits to the
capacityoftheofl-gassystem
to contan combustion gas,
(net cumulative capacity)
Increase hood capaaty,
processat astowermie,
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
lonia 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 ISV process may be obtained
from Steve James, U.S. EPA, Risk Reduction Engineering Labora-
tory, Cincinnati, Ohio 45268, (513) 569-7877 orFTS (684-7877),
Table 4
in-Situ Vitrification Status at CERCLA Sites
SELECTED:
Reglon 5-lone Landfill, MI 9/89
Regton 5- Parsons/ElM, MI
(Removal on) FY90
Regmonlo-Northwesttransformers,
WA 9(89
Heavy me ls, organtcs In
So!
Pestctdes, heavy metals
iow-Iev oxtns in Soil
PCBs in Soil
5000 cubic
yards
Not Provided
Not Provided

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