NCD980602163_19840606_Warren County PCB Landfill_SERB C_Intergovernmental Work Group for of PBC Detoxification 6 June 1984 Meeting and Reports-OCR

1:30 p.m.
5:00 p.m.
INTERGOVERNMENTAL WORK GROUP FOR DETOXIFICATION OF PCB
Wednesday, June 6, 1984
Transportation Board Room
Highway Building
Raleigh, North Carolina
1:30 p.m. -5:00 p.m.
Proposed Agenda
Call to Order
Roll Call
Approval of Minutes
Announcements
Site Maintenance
Reports by Members
Confidentiality Agreement
Review Galson/Polybac
Engineering Aspects Plan
Committee Work Session
Report to Governor
Other Business
Adjournment
Dr. Daniel A. Okun
Chairman
M. C. Adams
Maintenance & Equipment Branch
Department of Transportation
ENGINEERING ASPECTS OF WARREN COUNTY LANDFILL DECONTAMINATION
Detailed discussion of the p~ocedures for cleanup of the Warren
County landfill will require development of a treatment protocol
and consideration of such factors as reaction rates, ease of ex-
cavation, decontamination procedures for equipment and personnel
protective equipment, availability of utilities, etc. Some of
this information, particularly reaction rate data and efficiency
of the washing step, will need to be generated during laboratory
testing. However, the general outline of the process can be dis-
cussed.
The GALSON/Polybac process for decontamination of PCB contaminated
soil consists of 4 steps:
1. Place soil from landfill into reactor vessels.
2. Treat soil -reaction
reagent recovery
soil washing
treat wash water by distillation and/or by
biological treatment.
3. Biological treatment of soil to complete degradation of any
material not removed by water wash.
4. Replace soil in landfill.
The engineering aspects of each step will be discussed separately.
Excavate soil and place in reactors:
At the start of the cleanup the topsoil will be removed from
the site and placed in a location for eventual replacement.
The clay cap will be removed from the landfill by sections.
After each section is processed, the soil will be replaced.
This will limit the amount of contaminated soil exposed at
any one time. A holding area will be required for treated
soil awaiting repla cemen~ in the landfill. The size of
the holding area wi ll depend on the amount of soil removed
in each section. If the landfill is divided into four
sections, then a holding area of 250 feet on a side may
be adequate. A smaller area could be used by piling the
soil higher, if necessary.
Soil will probably be taken directly from the landfill to
the reactors. If dust fugitive emission is a problem, the
soil may be wetted before excavation. This moisture can
be removed from the soil at the start of processing.
A possible problem with the excavation step will be col-
lection of rainwater in the excavated area. If the exist-
ing leachate collection and treatment system is inadequate
to handle this amount of water, an additional treatment
system may be required.
Soil Treatment:
The excavated soil will be placed into a series of 18
cubic yard capacity reactors. Current design options call
for a series of 3 reactors linked to a utility trailer con-
taining reagent handling equipment, electrical generators
and possibly a distillation unit. If a bio-treatment unit
is used for wash water cleanup, distillation will not be
required. If 3 reactors are used on a 24 hour/day sched-
ule, the decontami nation of 45,000 cubic yards of soil
will require about 14 months (assuming 70% operation and
an 8 hour cycle time). A six reactor system would cut
this time to 7 months, as would reducing the cycle time
to 4 hours/batch.
At the end of the reaction the reagent is reclaimed by
volatilizat ion. The soil is then washed to remove any
remaining reagent and the reaction products. The wash
water is then either distilled to recover reagent or
treated in a CTX Biotreatment unit. The selection of
the water treatment process will depend on the effec-
tiveness of the reagent recovery step as determined
during preliminary laboratory testing. If the distil-
lation option is chosen, the residual materials will
probably be sent out for incineration as PCBs.
The soil treatment system will involve six or seven
trailers (assuming a 3 react or system). This would
include the three reactor trailers, a utility and dis-
tillation trailer, a control/lunchroom trailer, a tank
tra iler for reagent and a CTX Biotreatment trailer. A
six reactor system would require four additional trail-
ers. Six trailers would require a 50' by 50' area,
although a larger area would be desirable.
The soil washing step will require a large amount of
water. This water will be either biotreated or dis-
tilled for reuse. A three reactor system, with each
batch of soil washed three times would require a water
storage system of about 40,000 gallons. This could be
handled using four 10,000 gallon modular tanks assem-
bled on site. The wash water tank farm will require
an area of about 30' by 40'.
Biological Treatment:
Biological treatment will occur in two areas, if the
laboratory tests on the landfill soil so indicate.
The first will be the wash water. The wash water con-
taining reagents or reaction products may prove more
economical to biologically treat than to recover the
..
chemicals. The water could be cleaned sufficiently
to recycle. This treatment process would occur in
a CTX Biotreatment Unit. The unit is portable, re-
quires only electricity for blower and pump operation
and could be easily located in an area 10' x 30'.
The washed soil may be treated in two different man-
ners. The first by landfarming and the second by spray-
ing the biomass onto the washed soil and recycling the
effluent through the CTX Biotreatment Unit. The treat-
ed soil in either case would be replaced in the land-
fill. The treated effluent would be discharged ulti-
mately.
Replace Soil in Landfill:
The treated soil will be moved from a staging area
back into the landfill. After all of the soil has
been replaced, the clay cap will be replaced and
cove red with topsoil and seeded to avoid erosion.
Other Considerations:
Utilities such as electrical power and water will
be required for the site. These may be either sup-
plied by trailer mounted generators
or by connection to local systems.
term nature of the cleanup effort,
cost effective to connect to local
for telephone service.
Proposed Course of Action:
and water
Given the
it may not
utilities,
tanks,
short
be
except
There are 3 critical variables which must be assessed
before a cleanup of the Warren County landfill can be
..
designed and costed. These variables include the
following:
1. Rate of reaction of landfill soil.
This determines in large part the time required
for the cleanup.
2. Effectiveness of reagent recovery step.
This determines the choice of method for wash
water cleanup and recycle. If almost all of
the reagent is recovered in this step, then a
biological treatment becomes attractive. If
large amounts of reagent end up in the washwater,
the reagent recovery by distillation becomes
cost effective.
3. Effectiveness of soil washing procedure.
This determines the acceptable residuals limit
in the soil and the degree of biological treat-
ment needed.
These factors must be studied in laboratory tests on
actual or simulated landfill soil, since soil charac-
teristics have a major effect on process performance.
Therefore the next step in decontamination of the
Warren County landfill is to design and carry out a
laboratory study on soil from the landfill.
• ' I -
A layout of one proposed site configuration is shown in fig 1, below
FIG 1 -PROPOSED LAYOUT FOR DECONTAMINATION OF WARREN COUNTY LANDFILL
INTERIM STORAGE FOR
DECONTAMINATED SOIL
REAGENT TANKS
UTILITY TRAILER
I
ODO
REACTORS
CONTROL ROOM
BIOTREATMENT
UNIT
D
WASH WATER TANKS
LANDFILL
In Situ Vitrification-
A Potential Remedial Action
Technique for Hazardous Waste
V. F. FitzPatrick
J. L. Buell
K. H. Oma
C. L. Timmerman
June 1984
Presented at
the Hazardous Material Conference Exhibit
in Philadelphia, Pennsylvania June 5, 1984
Pacific Northwest Laboratory
Operated for the U.S. Department of Energy
by Battelle Memorial Institute
()Battelle
PNL-SA-12316
IN SITU VITRIFICATION -A POTENTIAL REMEDIAL
ACTION TECHNIQUE FOR HAZARDOUS WASTES
V. F. FitzPatrick, J. L. Buelt, K. H. Oma, and C. L. Timmerman
Pacific Northwest Laboratory
Richland, Washington 99352
INTRODUCTION
In situ vitrification (ISV) is an innovative technology being developed as
a potential method for stabilizing transuranic (TRU) contaminated wastes in
place. Although the process is being developed for TRU contaminated wastes, it
is envisioned that the process could also be applied to hazardous chemical
wastes.
In situ vitrification (ISV) is the conversion of contaminated soil into a
durable glass and crystalline waste form through melting by joule heating. The
technology for in situ vitrification is based upon electric melter technology
developed at the Pacific Northwest Laboratory (PNL) for the immobilization of
high-level nuclear waste.1 In situ vitrification was initially testerl by
researchers at PNL in August 1980 (U.S. Patent 4,376,598).2 Since then ISV has
grown from a concept to an emerging technology through a series of 21
engineering-scale (laboratory) tests and 7 pilot-scale (field) tests. A large-
scale system is currently being fabricaterl for testing. The program has been
sponsored by the U.S. Department of Energy's (DOE's) Richland Operations
Office* for potential application to Hanford TRU contaminated soil sites.
The ISV development program is utilizing three sizes of vitrification sys-
tems. The distinguishing characteristics of each system are power level, elec-
trode spacing, and mass of block produced, as shown below:
Electrode Vitrified Mass
St stem Power kW S~aci ng (m) Per Setting ( t)
Engineering 30 0.23-0.36 0.05-1.0
Pilot 500 1.2 10
Large 3750 3.5-5.5 400-800
Major advantages of in situ vit ri fi cation as a means of stabilizing radio-
active waste are:
~ safety in terms of minimizing worker and public exposure
~ long term durability of the waste form
~ cost effectiveness
~ applicability to different kinds of soils.
* Under Contract DE-AC06-76RL0-1830.
1
This paper describes the present status of ISV technology.
PROCESS DESCRIPTION
In situ vitrification is a process for stabilizing and immobilizing con-
taminated soils. To begin the process, which is shown in Figure 1, graphite
electrodes are inserted vertically in the ground in a square array. Graphite
is placed on the surface of the soil between the electrodes to form a conduc-
tive path, and an electrical current is passed between the electrodes, creating
temperatures high enough to melt the soil. The molten zone grows downward,
encompassing the contaminated soil and producing a vitreous mass. Convective
currents distribute the contaminants uniformly within the melt. During the
process, gaseous effluents emitted from the molten mass are collected by a hood
over the area and routed through a line to an off gas treatment system. When
power to the system is turned off, the molten volume begins to cool. The pro-
duct is a block of glasslike material resembling natural obsidian. Any subsi-
dence can be covered with uncontaminated backfill to the original grade level.
The principle of operation is joule heating, which occurs when an electri-
cal current passes through the molten mectia. As this molten mass grows, resis-
tance decreases; so to maintain the power level high enough to continue melting
the soil, the current must be increased. This is accomplished by a transformer
equipped with multiple voltage taps. The multiple taps allow more efficient
use of the power system by maintaining the power factor (the relationship
between current and voltage) near maximum. The process continues until the
appropriate depth is reached. Melt depth is limited as the heat losses from
the melt approach the energy deliverable to the molten soil by the electrodes.
To contain off gases that are released from the melting process, an off-
gas hood that is operated uncter a slight vacuum covers the vitrification
zone. The hood also provides support for the electrodes. The off gases are
routed from the hood to a treatment system, which scrubs and filters hazardous
components.
4
. .
~ . . . . .. . . , ... ....... . ·. .. . ' .
, .· . . . . . ~ -.
·7 . .· .. . ·.· :·· .. ~:-... ~ :~ ..
ELECTRODE• MELTING ZONE . ... . VITRIFIED SOIL/WASTE
Figure 1. In situ vitrification process sequence.
2
A more detailed description outlining the power system design and the off-
gas treatment system follows.
Power System Design
The power system design is similar for all three scales of the ISV pro-
gram. A transformer connection converts three-phase alternating current elec-
trical power to two single-phase loads. The single-phase loads are connected
to two of the electrodes, which are arranged in a square pattern, creating a
balanced electrical load on the secondary. The even distribution of current
within the molten soil produces a vitrified product almost square in shape to
minimize overlap among adjacent settings. Multiple voltage taps and a halanced
load allow a near constant power operation, which shortens run time and thus
minimizes cost.
Off-Gas Treatment System
In both the pilot-and large-scale systems, the hood collects the off gas,
provides a chamber for the combustion of released pyrolyzed organics, and sup-
ports the four electrodes embedded in the soil. Much of the heat generated
during the ISV process is released to the off-gas stream. This heat is removed
in the off-gas treatment system, so that the temperature of the gas which exits
after treatment is close to ambient.
There are three major kinds of treatment for the off-gas system (see Fig-
ure 2). First, the gases are scrubbed in two stages, with a quencher and tan-
dem nozzle scrubber. These scrubbers remove particles down through the
r----------------------------------------------------------~
COOLING
PARALLEL QUENCHER .
.---+I SCRUBBER. VANE
SEPARATOR. AND TANK
TRAPS
-Of-------'----~
3000 LITER TANK
A
HEATER y
,.. ___________ ..,
: HEPA Fil TEAS INLET BYPASS
I
I : ~ - - - - - - - - - - - - - - - - - - - - - - - - ---- - - - - - - - - - - - - - - -...J CONTAINMENT MODULE
Figure 2. Schematic for the large-scale off-gas system.
3
STACK
r
submicron range. Second, the water in the saturated gas stream is removed by a
vane separator and condensor followed by another vane separator. Third, the
off gas is heated, insuring an unsaturated gas stream at a temperature well
above the dewpoint, and then it is filtered with two banks of high efficiency
particulate air (HEPA) filters. Both the pilot-and large-scale systems are
trailer mounted and therefore mobile.
The off gas-treatment system required for ISV application to hazardous
chemical wastes will probably be simpler than that required for radioactive
application. Specifically, the requirements for dewatering and filtering the
gas stream would probably not be necessary. In some special applications,
where one of the contaminants becomes a toxic gas, it may be necessary to add a
special treatment stage such as a charcoal bed.
PERFORMANCE ANALYSIS
The ability of the waste form to retain the encapsulated or incorporated
radionuclides (some with very long half-lives) is of prime importance to the
usefulness of the ISV process.
Vitrified soil blocks have been analyzed to determine their chemical dura-
bilities with a series of tests including 24 hour soxhlet leach tests. The
soxhlet leach rate for all elements was less than 1 x 10-sg/cm2/day, an accep-
table value. These rates were comparable to those of Pyrex® or granite, and
much less than those of marble or bottle glass, as shown in Figure 3.
PYREX
VITRIFIED
HANFORD SOIL
GRANITE
MARBLE
BOTTLE GLASS
:==J
I
0
I
I
I
I I I I I
2 3 4 5 6
SOXHLET CORROSION RATE, g/cm2-d x 105
Figure 3. Leach resistances of selected materials.
® Pyrex is a registered trademark of Corning Glass Works, Corning, New York.
4
A 28 day Materials Characterization Center test (MCC-1)3 was also conduc-
ted on a contaminated soil sample that had been vitrified in the laboratory at
1600°C. The overall leach rate of the vitrified soil is comparable to the
PNL 76-68 waste glass developed for high-level nuclear wastes.4 The measured
release rate of Pu from the vitrified soil was 2 x 10-7 g/cm 2/day. Higher
vitrification temperatures like those experienced in the field (~1700 to
2000°C) are expected to lower the Pu leach rate.
Another indication of the durability of the ISV waste form is found in a
study of the weathering of obsidian, a glasslike material physically and chem-
ically similar to the ISV waste form.5 In the natural environment, obsidian
has a hydration rate constant of 1 to 20 µm 2 per 1000 years.6 A value of
10 µm 2 per 1000 years, assuming a linear hydration rate, yields a conservative
estimate of a 1 mm hydrated depth for the ISV waste form over a 10,000 year
time span. Since hydration is also the initial mechanism of weathering, the
ISV block is expected to maintain its integrity at least through this
10,000 year time period.
Another important factor to consider in the waste form evaluation is the
migration of the radionuclides once they are a part of the molten waste form.
In the pilot-scale field tests, the radionuclides did not move beyond the
vitrified block. Furthermore, analysis of the blocks from the tests revealed
that the radionuclides did not concentrate in the block, but instead were uni-
formly distributed. These factors are very important considerations for appli-
cation of ISV to chemical wastes, containing toxic or heavy metals.
Far term (10,000 year) performance assessments have been made to determine
the effectiveness of selective vitrification for immobilizing high TRU concen-
tration zones at a reference waste site at Hanford. Scenarios evaluated
included inadvertent and intentional human intrusion, transients and permanent
residents in the vicinity of the waste site. For these scenarios, the vitri-
fied zone was covered by an engineered barrier and this combination was com-
pared to sites with no remedial action and sites with just an engineered
barrier. Results of the analysis showed that the amount of radioactive mate-
rial available for human ingestion was reduced by up to 10 5 for the site that
was selectively vitrified and had engineered barriers. It was concluded that
vitrification cannot prevent human intrusion into old or abandoned waste sites,
but it can moderate its consequences. The groundwater pathway was not consid-
ered for this analysis because of the characteristics of the Hanford Site.
Insight into far term performance when the groundwater pathway may be signifi-
cant can be obtained from the leach data presented in the preceding paragraphs.
Specific data on the leach rate of heavy metals are beyond the current
scope of the ISV program; however, the data for radioactive contaminated soils
indicate the potential for using ISV to isolate toxic and heavy metals from the
biosphere.
Also studied was the release of elements from the soil to the off-gas
stream during processing. This partitioning is usually described as the decon-
tamination factor. The higher the decontamination factor (the mass of an ele-
ment in the soil divided by the mass released to the off-gas treatment system),
5
the smaller the amount of an element that is released from the soil during pro-
cessing. Based on results from the pilot-scale system, it is estimated that
for the large-scale system, soil-to-off-gas-hood DFs for less volatile elements
such as Pu, Sr, and U will be 1 x 10 3 to 1 x 10 4 • More volatile elements such
as Cs, Co, and Te should have DFs of about 1 x 10 2 • Low boiling heavy metals
such as Pb and Cd should have DFs about 10. (Additional data on heavy metals
presented later in the paper.) Element retention increases with depth of
burial and the presence of a cold cap and decreases with the presence of gas
generating materials. Decontamination factors for the off-gas treatment system
(hood to stack) are as follows: for the semivolatiles (Cs, Co, and Te), 1 x
10 4 and for the less volatile nuclides Sr and Pu, 1 x 10 5 • Therefore, the soii-to-stack DFs are 1 x 10 6 for the semivolatiles and 1 x 108 to 1 x 10 9 for
less volatile materials. For particulates the DFs are about 1 x 10 11 •
PROCESS PARAMETERS
PNL studied nine soils from waste sites all over the U.S. to determine how
varying soil properties affect the vitrification process. None of the normal variations in properties such as electrical and thermal conductivities, fusion
temperature, viscosity, and chemical composition significantly impact ISV
operation. While soil moisture increases the power requirements and run time
of the ISV process, it is not a barrier to its use, having only a small effect
on the attainable melt depth. Soil moisture is an economic penalty propor-
tional to the amount of heat required to evaporate the water.
The effect of materials buried with the waste itself, particularly those
that are commonly found in waste sites, has been considered. These materials
include metals, cements and ceramics, combustibles, and sealed containers.
While there are some limitations to the ISV process due to waste inclusions,
they are not significant. The most significant consideration is sealed con-
tainers housing highly combustible organics. A large number of such containers
could potentially increase the flow rate requirements of the off-gas system.
The processing capabilities of the large-scale ISV system are depicted in
Figure 4. The width per setting ranges from 3.5 to 5.5 m, with attainable
depths of 10 to 13 m. The depths are calculated on a conservative basis using
nominally high heat losses. Metals can occupy 70 percent of the linear dis-
tance between electrodes, with only a 10 percent decrease in voltage. This
value represents process testing to date rather than the limit for the system.
The void volume of 4.3 m3 and combustible packages of 0.9 m3 reflect the capac-
ity of the off-gas treatment system. The solid combustible concentration of
3,200 kg/m/setting represents a situation that might be encountered in a typi-cal land fill disposal operation. The combustible liquid concentration of
4,800 kg/m/setting again reflects the capacity of the off-gas treatment
system. There is a design factor of two associated with all of the void volume
and combustible loading numbers. The design factor will be verified by field
testing the large-scale system in FY 1985.
6
J: I-Q. w 0
1-w1DTH-I
WIDTH
DEPTH
.. METALS= 70 LINEAR %
-·,,-,:-AND 5 WT% i.i~ •·••·· > .. •••... i t :( ~•g~;?,;~.~~~i;IBLE
. . . . . . . .
LARGE-SCALE
3.5 m -5.5 m
10 • 13 m
3.85 m
4800 kg/m/SETTING
4.3 m3
0.9 m3
3200 kg/m/SETTING
Figure 4. Large-scale ISV system capabilities.
ECONOMIC ANALYSIS
The cost of using ISV as an in-place stabilization technique has been
estimated.7 The cost estimate includes expenses from the following four cate-
gories: site preparation activities, annual equipment charges, operational
costs (labor), and consumable supplies such as electrical power and ~olyhrlenum
electrodes. Five different configurations were evaluated which include varia-
tions in operating manpower levels, power source costs, and heat loss assump-
tions used by the mathematical model to predict processing efficiency. The
cost comparison for vi tri fyi ng to a depth of 5 m for a reference conta1ni nated
zone configuration is given in Table 1. The process efficiency for vitrifying
to a greater depth and a different contaminated zone configuration is lower.
TABLE 1. COST ESTIMATES FOR FIVE ISV LARGE-SCALE CONFIGURATI ON S
Total Cost Total Cost
of Soil of Soil
~1anpov1er Vitrified, Vitrified,
Number Site Power Heat Loss Level 1982 '.!i/m 3 1982 $/ft 3
1 Hanford Local High Average 187 5.30
2 Hanford Local Average Average 161 4.60
3 Hanford Local Average Above Avg. 183 5.20
4 Generic Local Average Average 180 5 .1 0
5 Generic Portable Average Average 224 6.30
7
Cost of electrical power and the amount of soil moisture in the area being
vitrified can affect the economics of the process significantly. Figure 5
illustrates the influence of these two parameters on cost. At low electrical
rates (i.e., $0.029/kWh), power costs account for only 20% of the total opera-
tional cost. However, at $0.049 kWh and $0.0825 kWh, power costs account for
30% and 40% of the total cost, respectively. The energy cost has a ceiling at
$0.0825/kWh; above this electrical rate, a portable generator can be leased and
operated at an equivalent electrical rate of $0.0825 kWh.2 Soil moisture
increases the operating cost of the process by requiring more energy to vitrify
a given volume of contaminated soil because the water in the soil must be
evaporated. This adds to the electrical energy costs and the time required to
complete the process, which in turn increases the cost contribution from labor.
" E ;,
.;
0 u
ii 0 I-
400.-------------------------
300
200
100
2 4 6
Utility ~ I ~ Portable
Power Generator
I
I
I
8 10
Electrical Rates (¢/kWh!
12
Figure 5. Cost of in situ vitrification as functions of electrical
rates and soil moisture.
EXPERIENCE WITH HAZARDOUS/ORGANIC MATERIALS
During process evaluation with the 21 engineering-and 7 pilot-scale
tests, various hazardous, simulated hazardous and organic materials have been
added to the test area to determine system performance. Some of these mate-
rials are Co, Mo, Sr, Cd, Cs, Pb, Ce, La, Te and Nd as nitrates; chlorides and
oxides; organic solvents such as carbon tetrachloride, tributyl phosphate and
dichlorobenzene; and combustibles such as cotton and rubber gloves, wood chips
and paper. The three main conclusions drawn from these tests are 1) burial
depth attenuates release; e.g. 1 to 1-1/2 meters of uncontaminated overburden
lowers release fractions significantly; 2) gaseous releases associated with
combustibles result in a significantly higher release fraction; and 3) organics
are pyrolyzed, resulting in combustion in the hood directly above the molten
zone.
8
The importance of burial depth during pilot-and engineering-scale testing
is illustrated in Figures 6 and 7, respectively.
Gaseous releases enhance the release fraction. Once the material is
vitrified and incorporated into the vitreous mass, it is not available for fur-
ther release except in direct proportion to its vapor pressure and in inversely
proportion to its solubility in molten glass. However, gaseous release, which
is usually associated with combustion, provides an additional release
mechanism--entrainment--for those contaminants associated with the combusti-
bles. This can be seen comparing Figure 7 with Figure 8, with respect to Pb
and Cd. It should be noted that the process temperature is in the range of
1700 to 2000°C, so for low boiling, insoluble heavy metals the release fraction
can be up to several percent compared to semi-and non-volatile elements.
Again, the release fraction will be dependent upon the vapor pressure and the
solubility in the glass.
Combustibles testing has included up to 50 kg of solid combustibles and
23 kg of tributylphosphate in a single experiment. Chromatographic, sample
bomb and mass spectrometric analyses of the effluent from both the hood and
stack indicate less than 5 x 10-3 volume percent release for light hydrocarbon,
indicating nearly complete pyrolysis and combustion.
99. 99 ,---,--,-----r---.------.--~~---.----.,----.---,---,---...-r---,
~ 99.9
(!) z ;::
..I w :E
(!)
~ 99
=> C
z a ;:: z w t;; 90
a:
Sb
Te
0 ..._____.__..____.___......___._ _ _.____. _ _,_ ___ .___,__.____._ _ _._____.
0 0.2 0.4 0.6 0.8 1.0 1 .2 1.4
BURIAL DEPTH (ml
Figure 6. Element retention versus burial depth during pilot scale tests.
9
100
Cl 99.9 z j:::
-' w
:l?
Cl 99.8 z a: ::,
C
C w 99.7 z < I-w a:
"# 99.6
99.5
100
Cl 99 z j:::
-' w :l?
Cl 98 z a: ::,
C
C 97 w z < I-w a:
~ 96
95
0 4 8 12 16 20 24 28
AVERAGE BURIAL DEPTH FROM SURFACE (cml
Figure 7. Element retention versus burial depth during
engineering scale tests.
10
"' "' "' ff
30 , FIELD TEST 3
20 ,,,,,,...-------/
10 / _ _,,, ,,-
~ / 0 ,,
en 0
<! FIELD TEST 4A (!) "'"' "'"' u. 30 u. 0
0 --Cd I-20 w --Pb (/)
<! "' ACTIVE GAS w RELEASE PERIODS ..J 10 w a:
w ...,---> 0 ----~ <! FIELD TEST 4B ..J "' "' "' "' :::> ~ 30 :::> u
20
10 ---------/
0 ..... --
0 10 20 30 40 50
RUN TIME. h
Figure 8. Cd and Pb release as a function of run time.
SUMMARY AND CONCLUSIONS
The following conclusions may be drawn from the evaluation of ISV
technology:
• In situ vitrification is a developing technology that may have
significant potential for selected hazardous waste disposal.
~ Organic compounds are pyrolyzed during ISV. Subsequent combustion
and off-gas treatment hold potential for permanent disposal of
selected toxic organic wastes.
o Process economics for contaminated soil sites at Hanford are in the
range of $4 to $6.5O/ft 3 of soil vitrified. Differences in site
geometry, electrical power costs, soil moisture and other factors
can influence these costs. For a soil moisture 25 percent, an d
using a portable power supply, costs would be about $9/ft 3 of soil
vitrified.
11
~ Far term (10,000 year) performance analysis for TRU contaminants
leads to the belief that ISV may minimize the effects of persistent
toxic and/or heavy metal wastes.
When viewing the potential for ISV technology transfer from the nuclear to
the hazardous waste arena, it is prudent to remember that ISV appears to he an
excellent specific remedial action technique--it is not a panacea, but judici-
ously applied the process holds promise to mitigate the effects of unprocessed
buried chemically hazardous wastes.
REFERENCES
1 Buelt, J. L. et al. 1979. 11 A Review of Continuous Ceramic-Lined Melters
and Associatect Experience at PNL.11 PNL-SA-7590, Pacific Northwest
Laboratory, Richland, Washington.
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