906R87110
SUPERFUND INNOVATIVE TECHNOLOGY EVALUATION (SITE) PROGRAM
SUMMARIES OF TECHNOLOGIES SELECTED DURING
THE SECOND SOLICITATION (SITE OO2)
NOVEMBER 16, 1987
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TREATMENT PROCESS: Oxitron Fixed-Film Fluidized Bed
Biological Treatment
DEVELOPER: Air Products and Chemicals, Inc.
Allentown, Pennsylvania
TECHNOLOGY DESCRIPTION
Aerobic biological treatment of wastewater is enhanced in a
fixed-film fluidized bed. This process was originally
developed by Dorr-Oliver. The fixed film is supported on
either an inert medium (sand) or activated carbon. Pure
oxygen is dissolved in the influent stream in a controlled
fashion to ensure that no excess oxygen is released at the
top of the reactor. The use of pure oxygen eliminates the
need for excess aeration and reduces the possibility of
emitting volatile organic compounds (VOC) from the treatment
process. An off-gas carbon adsorption unit is available if
needed.
Research has shown that biodegradation of many hazardous
compounds is possible; however, the rate of degradation in
many cases is extremely slow. Two factors provided in the
system address this problem:
1. The biomass concentration created by this treatment
process is five to ten times that normally maintained
in conventional reactors.
2. Use of activated carbon in the system will help retain
adsorbable and slowly degradable compounds, allowing
additional retention time in the system.
The medium and biomass remain in the system until the
biodegradation is complete. If excessive biomass develops
during the process, it is removed from the system and proper
disposal is required.
The treated effluent may be discharged to a municipal
sewerage system depending on the remaining hazardous
constituents and discharge requirements. The waste biomass
should have a solids concentration of about one percent.
Thr waste biomass must be disposed of properly or treated
further.
The system consists of a reactor unit, an oxygen supply
system, a biomass separating device, pumps, a recycle tank,
and mechanical controls. An off-gas carbon adsorption unit
is available, if needed. The reactor unit is mounted on a
skid which should be placed on level, compacted earth. The
equipment skid contains the oxygenator, pumps, recycle tank,
and control panel. Four concrete pads are required for the
foundation of this unit; one at each corner.
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WASTES TREATED
This process treats wastewaters containing soluble
biodegradable organic compounds including VOCs. This
process does not remove solids or inorganics. High
concentrations of heavy metals, PCBs, and other biologically
inhibitory constituents require pretreatment.
Following is a list of compounds that may be treatable:
phenol acrylonitrile
hexacholoroethane carbon tetrachloride
naphthalene ethylbenzene
toluene benzene
methylene chloride methyl ethyl ketone
other ketones
Concentrations from 0.01 to 200 mg/1 of the following
compounds may be treatable:
trichloroethylene
tetrachloroethylene
1,2-dichlorobenzene
1,2,4 trichlorobenzene
bis (2-ethylhexyl) phthalate
pentachlorophenol
The following concentrations should be treatable by the
system without pretreatment:
oil and grease 500 mg/1
suspended solids 1000 mg/1
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TREATMENT PROCESS: Solvent Extraction with Liquified Gas
DEVELOPER: CF Systems Corporation
Cambridge, Massachusetts
TECHNOLOGY DESCRIPTION
Liquified gases (carbon dioxide or propane) at high pressure
are used to extract oils and organic solvents from
wastewater and sludge in a continuous process. Waste is ex-
tracted with the fluidized gas in high pressure reactors.
The high pressure liquifies the gases, and the organic con-
taminants dissolve into the liquified gas. When the ex-
traction is complete, the liquids are separated, and the
gases are evaporated from the organic liquid contaminants by
reducing the pressure. The evaporated gases are
recompressed, condensed, and recycled to the extraction
reactor. Energy is conserved by using the heat generated by
gas recompression and condensation to heat the gas
evaporation step.
The technology is similar to the supercritical fluid ex-
tractions being developed by the food and drug industries.
One method of decaffeinating coffee uses liquified carbon
dioxide. The gases are nontoxic and inexpensive, and
special design provides for the construction of the high
pressure reactors. Liquified gases also provide
improvements in extraction efficiency over some solvent
extraction processes. Two different types of units are
available for wastewater and sludge treatment.
(1) Dissolved and emulsified organics can be extracted from
aqueous waste (leachate, groundwater, wastewater, surface
water) using carbon dioxide at ambient temperature and 950
psi. A full-scale (20 gpm) unit is available in Braintree,
MA. Bench-scale test results for two wastewaters extracted
with fluidized carbon dioxide have been submitted to EPA.
In both tests, methylene chloride, 1,1,1 trichloroethane,
trichloroethene, toluene, chlorobenzene, and xylenes were
extracted from concentrations of 50 to 400 ppm in the feed
to below detection limits in the treated wastewater.
Acetone, methanol, ethanol, and isopropanol feed
concentrations of 670 to 140,000 ppm were reduced by 70 to
95 percent during these tests.
(2) A pilot (1 gpm) sludge deoiling unit is available for
the extraction of heavy oil from sludge. Liquified propane
at 150°F and 100 to 300 psi is used to perform the
extraction. In addition, CF Systems is building a
full-scale (30 gpm) unit. The pilot-scale (1 gpm) sludge
deoiling unit is mounted on one truck trailer. The trailer
also contains a propane compressor and a cooling water
system. A separate trailer contains a small wet chemistry
laboratory. The
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trailer can be ready to operate in two to three days. The
system is operated on a continuous basis by two operators,
and an additional operator can serve as a laboratory
technician.
The two byproducts of both systems are a concentrated
organic-liquid extract and the feed material residue. The
concentrated organic liquid is composed of the organic
compounds that are extracted from the waste, and maximum
quantities can be predicted from feed composition. The
residue contains the nonextracted material, which is mostly
water and solids depending on feed composition.
WASTES TREATED
Dissolved and emulsified oils and organic solvents are
extracted from aqueous or sludge wastes depending on which
unit is used. Materials which are primarily contaminated
with heavy metals or inorganic compounds are not appropriate
for this technology. A wide range of organic compounds are
applicable, including:
carbon tetrachloride phenol toluene
chloroform oil & grease methyl acetate
benzene furfural acetone
napthalene butyric acid butanol
gasoline dichloroethane propanol
vinyl acetate xylene
high molecular weight organic acids heptane
high molecular weight alcohols
(1) In the wastewater treatment unit, aqueous wastes
(wastewater, groundwater, leachate, lagoon wastewater, etc.)
with total organic carbon (TOC) concentrations between 1000
ppm and 30 percent can be treated. For this unit, the
liquid feed must be able to pass through a 60-mesh (0.0097
inches or 0.246 mm) strainer, and a total solids loading
below 2.0 percent is desirable. If the waste is corrosive
to 316 stainless steel, it must be neutralized, inhibited,
or a system made of Hastelloy must be used. Wastes that are
reactive to carbon dioxide must be pretreated to eliminate
the reactive nature. Nonpolar higher molecular weight
organic compounds with low water solubility are extracted
more efficiently than compounds with high water solubility.
(2) For the extraction of oil from sludge using the deoiling
unit, water content up to 50 percent and oil concentrations
up to 40 percent are acceptable. Oversized materials in the
feed must be removed or ground, so that the waste can be
pumped into the reactor against the extraction pressure.
Pretreatment will be required if the waste is reactive with
propane. Organic liquids cannot be extracted from dry soil
at this time. CF Systems is developing a system which
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slurries solid wastes and soils with water so they can be
pumped into the extraction reactor. Aqueous based oil
sludges (API separator sludge, DAF sludge, tank bottoms) or
PCB contaminated surface impoundment sludges can be treated,
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TREATMENT PROCESS: Chemical Fixation/Stabilization
DEVELOPER: Chemfix Technologies, Inc.
Metairie, Louisiana
TECHNOLOGY DESCRIPTION
Soluble silicate reagents and silicate setting agents are
added to contaminated soil or sludge. Three classes of
reactions occur: (1) soluble silicates react with cations
in the waste mixture to form insoluble silicates; (2) the
silicious setting agents react with the remaining soluble
silicates to produce a gel structure; and (3) hydrolysis,
hydration, and neutralization occur to stabilize the final
product. For the treatment of certain organic constituents
and certain heavy metals, an additive is introduced with the
silicate setting agent. According to Chemfix, this process
does not reduce the volume of waste and may increase the
volume by as much as 20 percent.
Chemfix reports that field data shows processing rates of
500 to 700 gallons per minute. The stabilized material is
deposited into a solidification cell for quality assurance
testing before disposal. The treated material produced each
day is stored in a separate cell. Four or five
solidification cells are used to store the treated product
during the project. According to Chemfix, the required
physical characteristics (low leaching potential and low
permeability) are achieved after 48 hours, and the material
can be land disposed or graded into berms to isolate future
processed material.
Chemfix states that this system has proven successful in the
fixing of heavy metals in several wastes, including
electroplating wastes (F006), refinery waste (K048), con-
taminated soil, electric arc furnace dust (K061), and
municipal sewerage sludge. In one case, the final product
of the treatment of 150 million gallons of refinery waste
was delisted by EPA. Chemfix reports that plastics, resins,
and tars have also been successfully stabilized.
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The basic treatment process with silicates and silicate
setting agents has been applied to full-scale treatment.
The use of additives for certain metal and organic
contaminants has been tested at only bench scale on
artificial wastes. Bench-scale tests have been conducted on
the following heavy metals:
aluminum lead
antimony manganese
arsenic mercury
barium nickel
beryllium selenium
cadmium silver
chromium thallium
iron zinc
Bench-scale tests have also been conducted on PCP and PCB.
The concentrations of these compounds were significantly
reduced, and it is suspected that the chemical structure of
PCP and PCB were changed during treatment. The specific
chemical byproducts of these reactions have not been
identified.
The final treated material is an inert clay-like material
with high total alkalinity and low permeablility. In
previous full-scale treatments of heavy metals, the final
product has been used for the lining or capping of land-
fills. Air emissions may occur during the treatment of
volatile organic compounds. Chemfix states that air
emissions generated during the treatment of refinery waste
have been within acceptable limits.
The system includes a cement feeder, pug mill mixer, pumps,
liquid reagent storage tank, dredging equipment, and mixers.
A small lab trailer is also included with the system. A
prewetting chamber is available for the treatment of dry
solid wastes. A concrete pad with curb is required for the
equipment. A graded area is needed for access to the
treatment system and for the placement of trailers and
support vehicles. An area adjacent to the cleared area is
required for the construction of the solidification cells.
Throughout the treatment process, earth moving equipment is
used for the handling of the final product.
WASTES TREATED
This process is applicable to sludge and contaminated soil
containing nonvolatile organics (PCBs, creosote, etc.) and
heavy metals. The process can also treat the ash remaining
from incineration of wastes that contain both organics and
metals.
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The process can treat the following wastes:
Heavy Metals Maximum Concentration (mg/1 or mg/kg)
aluminum 100,000
antimony 5,000
arsenic 2,000
barium 20,000
beryllium 5,000
cadmium 90,000
chromium 80,000
iron 150,000
lead 100,000
manganese 150,000
mercury 1,000
nickel 40,000
selenium 2,000
silver 10,000
thallium 5,000
zinc 250,000
Other Constituents Acceptable Ranges
polynuclear aromatic <10,000
hydrocarbons
oil and grease <10%
pH 3.5-11.5
semivolatile (base neutral <10,000
and acid extractable) organics
Cyanide <3,000
The presence of certain organic or inorganic constituents
may necessitate the use of an additive in the process.
Chemfix states that this process can treat wastes containing
nonporous rocks, vegetable matter, shells, rubber, or
plastic. Shredding may be required prior to treatment of
wastes containing large anomalous particles or debris.
Wastes with solids content from 8 percent to 50 percent can
be treated without pretreatment. Prewetting may be required
for dry solid wastes. The treatment process is not conducted
in extreme cold conditions because of the potential freezing
of process water or waste materials.
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TREATMENT PROCESS: Liquid Solid Contact Digestion (LSCD)
DEVELOPER: MoTec, Inc.
Mt. Juliet, Tennessee
TECHNOLOGY DESCRIPTION
Biological treatment of liquids, soils, and sludges contam-
inated with organic compounds is accomplished after pre-
mixing the waste with water in a high energy mixing
environment. After treatment in the primary digestion tanks
or inground reactors, the mixture undergoes polishing steps
to further reduce the biodegradable waste concentration.
An auger pump system is used to move the soil or sludge into
the mixing tank. Water is injected at the head of the auger
to create a slurry for pumping and to reduce the generation
of air emissions. Waste is mixed (usually by aerators)
with water in the primary mixing tank to form a slurry with
20 to 25 percent solids. Water can be supplied from a fresh
or contaminated source (e.g., groundwater). Emulsifying
agents are added, and the pH is adjusted to increase the
solubility of organic compounds. This "batch" mixture is
transferred to primary digestion tanks where pH is
controlled, acclimated seed bacteria are added, and
biological oxidation is initiated. When the biodegradable
organic concentration has been reduced by 90 to 99 percent,
the batch is transferred to the polishing reactors where
nutrients are added to maintain the biodegradation process.
The treated supernatant from the polishing cell is recycled
to the primary contact tank.
Sludge from the polishing reactors is allowed to dry in
tanks or inground reactors constructed at the site. Solids
remaining from sludge treatment can be either returned to
the source excavation or disposed of elsewhere depending on
the presence of hazardous constituents. MoTec indicates
that sludge volume is reduced by 30 to 60 percent by this
treatment process, depending upon sludge TOC and water
content.
Treatment time varies with the organic compounds being
treated. When degradation is 90 to 99 percent complete, the
waste is transferred to two sequential polishing reactors.
The use of three reactors reduces treatment time.
Chlorinated polynuclear aromatics and polynuclear aromatic
hydrocarbons require a 14 to 21 day residence time.
Aliphatic compounds require a 6 hour to 10 day residence
time.
MoTec's LSCD equipment includes an auger pump system, mobile
tanks (3 tanks each with 20,000 gallon capacity), and air
emission hoods with carbon adsorption treatment. The
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treatment tanks may be covered with hoods, and air emissions
can be routed to a carbon adsorption treatment unit.
The mobile tanks might not be required if space is available
for the inground construction of primary mixing, digestion,
and polishing reactors. Air-supported buildings or
temporary greenhouses can be constructed to contain air
emissions from the reactors. The sludge treatment reactors
are constructed inground with 80,000 to 100,000 gallon
capacity. The inground reactors are lined with compacted
clay and 60 mil HDPE. The plastic in situ reactor liners
are decontaminated prior to disposal. The clay liners are
analyzed for contamination to determine appropriate disposal
requirements. Other equipment requirements include
bulldozers, backhoes, auger and trash pumps, tanks, and
diesel generators when electric power is not available.
WASTES TREATED
MoTec has been involved in the treatment of creosote and
pentachlorophenol wood preserving wastes. Pentachlorophenol
concentrations of 89,000 ppm and total creosote
concentrations of 500,000 ppm were reduced by more than 99
percent during the treatment of one wood preserving waste.
Motec also reports that oilfield sludges, refinery sludges,
and pesticide wastewaters have been treated.
Full-scale application of this system has been demonstrated
on liquids, sludges, and soils with high concentrations of
organic compounds. Influent waste should contain between 2
and 800,000 ppm of total organic carbon (TOC). If the waste
contains less than 3,000 to 5,000 ppm TOC, a hydrocarbon
supplement is added to support microbial growth. Extremely
high TOC sludges are diluted with water upon introduction to
the primary reactor.
Wastes primarily contaminated with inorganic compounds are
not appropriate for this technology. Full-scale units have
been developed for the treatment of the following organic
waste categories:
nonvolatile halogenated organic compounds
nonvolatile nonhalogenated organic compounds (phenols,
PAHs, etc.)
PCBs and dioxins
pesticides
Volatile Organic Compounds (VOCs) require reactor
modifications
Heavy metals and other inorganic constituents such as
chloride can inhibit microbial metabolism. Depending on the
inorganic speciation, the bacteria can tolerate the follow-
ing concentration levels:
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barium 35,000 ppm
zinc 3 to 5,000 ppm
chromium 6,000 ppm
arsenic 700 ppm
lead 6 to 800 ppm
Treatment temperature should be between 15°F and 100°F, .
although Motec indicates that treatment in cold weather can
be effective after the system has stabilized.
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TREATMENT PROCESS: Centrifugal Reactor
DEVELOPER: Retech, Inc.
Ukiah, California
TECHNOLOGY DESCRIPTION
This process destroys organic wastes and reduces the volume
of both organic and inorganic wastes. Solid and liquid
organic wastes are fed to a rotating reservoir within a
centrifugal reactor. Wastes are indirectly heated via
electrical conductance from a plasma torch. According to
Retech, the high temperature (2,800°F) achieved during this
process volatilizes liquid components of the waste and
achieves high destruction efficiencies on even "hard to
burn" wastes. The high temperature reduces the organic con-
stituents to carbon monoxide, hydrogen, and hydrochloric
acid, and, in some cases, all the way to carbon dioxide and
water. The volatilized components are captured and are
treated in a gas scrubber unit.
Metals and small amounts of solid carbon remain in the
vitrified combustion residue. The process continues until
the reactor fills with residue. The residue is then removed
from the reactor, and the constituents in the residue are
fixed in the vitrified residue during the cooling process.
If sampling determines that hazardous organic compounds
remain in the residue, the residue is recycled and treated
again in the reactor. The residue can be recycled until the
concentrations of hazardous components have been reduced to
a predetermined acceptable level. Some metals such as
mercury and cadmium may volatilize, and off-gas emission
treatment will be required.
Plasma torches of this type are used for metal melting
furnaces in the titanium and zirconium industries. Retech
states that the transferred plasma torch concept was used to
treat a simulated mixed-radioactive waste stream. According
to Retech, the volume of the waste was reduced by a factor
of 20. Other tests on simulated hazardous waste streams
have been conducted, but these results have not been
reviewed.
The system consists of a centrifugal reactor with an
internal rotating reservoir that is heated by a plasma
torch. The system also includes a screw feeder, holding
tanks, and a gas scrubbing system.
WASTES TREATED
This technology is applicable to organic and inorganic
wastes. This process is most appropriate for use in
situations where less expensive technologies, such as
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incineration, do not achieve satisfactory results. The
process has been used for volume reduction of radioactive
waste. Retech states that no compounds have been
encountered that interfere with the process. Retech
envisions that after further development, this technology
will be used to destroy PCB transformers.
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TREATMENT PROCESS: Removal of Metals by Selective
Ion-Exchange Compounds
DEVELOPER: Sanitech, Inc.
Twinsburg, Ohio
TECHNOLOGY DESCRIPTION
Metal bearing wastewater is treated by filtration and ion-
exchange. The wastewater is passed through a bed of silica
particles coated with a selective ion-exchange compound
which removes the metals from the waste stream. The metals
are then recovered by acid regeneration of the ion-exchange
compound.
Sanitech reports that this selective ion exchange process
yields much better removal efficiencies than systems using
commercial cation exchange resins. This is attributed to
the selective nature of the ion-exchange compounds.
Sanitech states that treatment times with commercial
ion-exchange resins may require five to ten years due to the
interference of sodium and calcium. They report that
treatment with their system could be completed in six to
twelve months.
Two units are available. System A can treat 4 gpm and is
loaded with ion-exchange compound to remove nickel, copper,
lead, trivalent chromium, and/or mercury. System B can
treat up to 12 gpm and is prepared for the removal of
cadmium and/or zinc. Other metals can be treated by each
unit after loading the units with the appropriate compound.
Sanitech reports removal efficiencies for chromium +3 and
+6, copper, mercury, nickel, silver, and zinc of more than
99 percent and effluent concentrations below 0.1 ppm.
Influent concentrations ranged from 100 to 1,000 ppm in
these tests.
System A consists of an automatic gravity prefilter for
removing suspended materials and a heavy-metal removal
(ion-exchange) unit. The ion-exchange unit is made up of
two beds containing 100 liters of ion-exchange compound,
pre-filters, a regeneration subsystem, and a control module.
The components of System B are the same as those in
System A, except that the heavy-metal removal beds are
larger containing 200 liters of ion-exchange compound. A
prefilter unit is included.
For small projects, the spent regenerant may be transported
and treated by approved and permitted operations. For large
projects, on-site treatment consisting of neutralization,
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precipitation, and dewatering would be required. Dewatered
sludge would then require disposal. In some instances, it
may be possible to recycle a metal-rich acid waste into a
plating bath solution. According to Sanitech, the effluent
wastewater will be below EPA limits for heavy metal
concentrations. Effluent concentrations should be
acceptable for discharge to a municipal sewage system or to
a surface stream.
WASTES TREATED
This process treats industrial wastewater, contaminated
groundwater, and contaminated surface waters. Sludges and
contaminated soil are not treated by this process. The
following toxic metals are currently treated by this
process:
Nickel Mercury
Copper Cadmium
Lead Zinc
Chromium +3 (trivalent)
Silver, chromium +6 (hexavalent), and arsenic can also be
removed, but additional time is required to prepare
ion-exchange compounds for removal of these metals.
Generally, up to three metals can be removed from the waste
stream using this process. Influent metal concentrations
should be from 0.1 to 200 ppm, although concentrations from
0.01 ppm to 5,000 ppm have been treated with this process.
Suspended oils are not treated by this process, although
soluble oils can be tolerated. High concentrations of
chelating agents including EDTA and cyanide will inhibit
this treatment process.
The influent must be free of rocks, insoluble organic
compounds, fine suspended solid particles (fine metal
precipitates), and slime. Soluble organic compounds can be
tolerated, but if they exceed EPA standards, they must be
removed, preferably before entering this treatment system.
This treatment system is not designed to remove organic
compounds. Sanitech states that sodium, calcium, and
organic species do not interfere with this process. The
influent should have a pH between 4 and 12, and influent
temperature should be between 32° F and 130° F.
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TREATMENT PROCESS: Chemical Stabilization/Solidification
DEVELOPER: Soliditech, Inc.
Houston, Texas
TECHNOLOGY DESCRIPTION
Stabilization and solidificaton is achieved by mixing the
waste with pozzolanic agents, water, and liquid reagents,
including URRICHEM. Microblending occurs in the mixing
process to disperse the reagent throughout the waste. Solid
tech reports that microencapsulation occurs partly by
cross-linking organic and inorganic particles through a
five-phase cementation process. Solid particles are
encapsulated within the concentration product matrix.
The final product is a pasty, thixotropic fluid that is
suitable for casting into final solid shapes. Physical
properties of the mix can vary according to the application.
Solidtech indicates that the solidified waste exhibits low
leaching potential and can achieve an unconfined compressive
strength of 5,500 psi. The final product is then ready for
disposal, and it can pass the paint filter test. According
to Solidtech, the waste volume change during processing can
vary from a 20 percent decrease to a 30 percent increase,
depending on waste characteristics.
Air emissions may be generated during the mixing process if
volatile organics are treated. The mixer can be equipped to
seal emissions in the mixing chamber. Trapped emissions can
then be vented through carbon canisters and baghouses for
particulate control. Dust may be generated during the
pneumatic loading of bulk dry pozzolanic reagents into the
feed hoppers.
Information provided by Solidtech indicates that this
process applies to both inorganic and organic wastes. In one
test, Solidtech reports that a 96 percent organic oily waste
was solidified and passed all TCLP leaching requirements.
In another test, a soil containing 30 percent PCBs was
stabilized, and TCLP extracts showed low ppm organic
concentrations.
The system comprises a 13-cubic-yard ribbon type mixer, a
pozzolanic storage silo, other reagent holding tanks or
hoppers, and multiple pumps. A shredder and a flash mixer
are also available, if needed. A concrete pad may be
required for the process area.
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WASTES TREATED
Waste liquids, slurries, sludges, or contaminated soils are
appropriate for this process. A broad range of organic and
inorganic wastes can be treated. Solidtech reports that
this process can treat wastes containing:
refinery separator sludge
refinery leaded tank bottoms
hazardous sludge
non-hazardous sludge
plating sludge
baghouse dust
liquid wastes
oil/sludge tank bottoms
inorganic sludge
paint sludges
organic oil
organic contaminated soil
acid waste with heavy metals
organic sludge
incinerator ash
inorganic waste
Contaminants are identified by the following EPA Waste
Numbers: F001-6, F019-23, F026-28, K001-11, K013-24,
K093-96, K025-29, K030, K083-87, K103-104, K105, Klll-118,
K136, K071, K073, K106, K031-52, K097-102, K123-126,
K060-62, and K069.
Treatment of wastes containing radioactive nuclides or
explosives requires special regulatory approvals. Highly
acidic or caustic wastes can be treated, but they may
require neutralization pretreatment.
The waste should be free of large anomalous particles and
debris. Pretreatment for large particles would consist of
physically screening and shredding the large materials.
Variations in the influent waste characteristics may reduce
the effectiveness of the treatment process do in part to
ratio variations of the mixing additives.
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TREATMENT PROCESS: Mobile Volume Reduction and
Solidification (VRS) System
DEVELOPER: WasteChem Corporation
Paramus, New Jersey
TECHNOLOGY DESCRIPTION
Organic and metal-bearing wastes are solidified by feeding
the waste and asphalt simultaneously to an extruder/
evaporator. A heated extruder/evaporator is used to
evaporate free water and volatile organic compounds (VOCs),
and to dispense the waste in the asphalt matrix. The
treated material is discharged into an appropriate
container, typically a 55 gallon drum, prior to land
disposal. The waste and asphalt mixture is heated
indirectly while in the evaporator/extruder by steam or
electric elements. The unit's temperature profile is
established to control the evaporation rate and maintain the
mixture in a fluid state. The extruder/evaporator uses
co-rotating self-cleaning screw elements to mix and convey
the materials and to provide efficient evaporation. The
asphalt and waste mixture hardens to form a free standing
monolith when cooled to ambient temperatures. Wastechem
indicates that, heavy metal and nonvolatilized organic
constituents are encapsulated in the solidified mixture.
Waste volume is reduced by evaporation and solids grinding
during the extrusion/evaporation process.
VOCs and water vapor are condensed in three sequential steam
domes. The condensed liquid is treated by carbon adsorption
and HEPA filters prior to discharge. The remaining gases
are discharged to the atmosphere.
The extruder/evaporater temperature is usually 300°F.
Influent waste loading is usually 40 to 60 percent of the
feed. A high-viscosity petroleum based asphalt meeting ASTM
D-312, Type III standards is used because it contains a very
low VOC content. WasteChem states that the volume of the
influent waste is reduced during this process by a factor
ranging from two to twelve. The volume reduction factor and
throughput rate depend on waste feed solids content.
Pilot-plant test programs have investigated the
solidification of arsenic-laden wastes, electroplating
sludge containing heavy metals, uranium raffinate, coal tar
acid sludge, and other selected hazardous wastes. WasteChem
reports that EP toxicity and TCLP leaching tests indicate
that heavy metals and other hazardous wastes can be diluted
through asphalt encapsulation. WasteChem also reports that
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no polynuclear aromatic hydrocarbons were detected in the
leachates.
A mobile system is equipped with a waste batch tank, asphalt
storage tank and recirculation system, extruder/evaporator,
devolatilization domes, condenser, carbon adsorption, and
HEPA filters. The process module contains the extruder/
evaporator, pumps, and filters. The asphalt supply module
contains the asphalt storage, melting, and feed equipment.
The electrical control module can be located remotely from
the process module, and all equipment is transported on one
trailer.
WASTES TREATED
Organic and metal-bearing wastes are treated by this
process. Wastes containing water and/or VOCs are
particularly suitable because of the evaporation of these
constituents and the subsequent volume reduction. Wastechem
reports that the process can also encapsulate dry solid
wastes, contaminated soil, and incinerator ash.
WasteChem indicates that this technique has been
successfully applied to the following categories of haz-
ardous waste: sludges containing Cr, Cu, As, Pb, Hg, Ba,
Zn, phenols, and polynuclear aromatics; incinerator scrubber
waste; coal and tar sludge; incinerator ash containing heavy
metals; electroplating sludges containing Cr, Cu, Fe, Ni,
and Zn; soils and sludges contaminated with VOCs; arsenic
waste sludges; paint and refinery sludges containing
organics and heavy metals; bead and powder resins; residues
from coal coking, liquefaction, and gasification that
contain aromatic hydrocarbons and inorganic acids;
petroleum-based sludges and still bottoms; and baghouse
dust.
WasteChem data indicate that the following influent
compounds and concentrations have been successfully treated
(i.e., TCLP tests indicate leachate concentrations are below
delisting limits):
arsenic 63 ppm
barium 125 ppm
chromium 1,250 ppm
silver 48 ppm
WasteChem is conducting tests on synthetic wastes with
higher concentrations. Pretreatment is required for wastes
containing the following materials:
1. VOCs with flash points below 350°F
2. Thermally unstable materials
BOS22/008
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3. Highly reactive or incompatible materials
4. Solvents in sufficient concentrations to soften the
asphalt
5. No friable particles greater than 1/4 inch in diameter
Typical pretreatment processes include thermally induced
evaporation, chemically induced preciptation, and solids
screening.
BOS22/008
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Technology Summary
In Situ Vitrification
I. General Description
In Situ Vitrification (ISV) has been proposed by Battelle Pacific
Northwest Laboratories (BNW) as a candidate for evaluation under the
Superfund Innovative Technology Evaluation (SITE) Program. ISV technology
is based on the concept of joule-heating to electrically melt soil or
sludge. Melt temperatures are in the range of 1600 to 2000°C and act to
destroy organic pollutants by pyrolysis. Inorganic pollutants are
immobilized within the vitrified mass. Both the airborne organic and
inorganic combustion by-products are collected in a negatively pressurized
hood which draws the contaminants into an off-gas treatment system that
removes particulates and other pollutants of concern.
The ISV system is proposed to be truck mounted on two semi-trailers.
The system is delivered to the site and must be set-up on relatively level
ground for most effective operation. Four electrodes are driven or
pushed into the soil or sludge to be vitrified and current is applied.
Present technology permits the vitrification of a 25 ft x 25 ft x 50 ft
(1 x w x h) volume of soil or sludge over a period of seven to ten days.
(This is called "one setting"). The system is then moved to a second
setting, adjacent to the first setting, and the vitrification process is
repeated. This is continued until the entire soil or sludge volume on
the site has been vitrified by the ISV process. Upon completion of the
vitrification at the site, the vitrified mass is left to cool over a
period of several months to a year.
II. Past Experience
ISV technology has been under development at BNW since 1980 and up
to this point (1987) has been principally oriented to the vitrification
of soils and sludges that are radioactively contaminated. As of July 1987,
.BNW had performed forty-five tests at various scales (bench, engineering,
pilot, field) for the Department of Energy (DOE). According to information
provided by BNW, the type of soil that is vitrified is not a major concern.
All but one of the field-scale tests have been performed on DOE's Hanford
Reservation and included tests on both uncontaminated and radioactively
contaminated soils. Non-radioactive pollutants that have been vitrified
include:
Scale Soil/Waste
bench industrial lime sludge
bench nickel-contaminated soil
bench cyanide-contaminated soil
engineering metal canister
engineering concrete canister
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engineering concrete monoliths
engineering heavy metals and organic contaminated soils
engineering PCB-contaminated soils
pilot -- waste drum with soil & simulated combustible
waste
pilot industrial lime sludge
Bench-scale and engineering-scale testing usually involves current
application for only a few hours, while pilot-scale testing may involve a
current application of a day or more.
In its most basic configuration, the ISV process consists of
an electrical network with four electrodes driven or pushed into the soil
or sludge, a capture hood to collect fumes or gases from the setting
and direct it to an off-gas treatment system, and the off-gas treatment
system itself. The off-gas treatment system currently used in vitrifying
radioactive wastes consists of a wet scrubber system, heat exchanger,
scrub tanks, scrub solution pumps, condenser, mist eliminators, heater,
filter assembly, and a blower system.
III. Range of Wastes
The ISV process can reportedly be used to destroy or volatilize
organics and/or immobilize inorganics in contaminated soils or sludges.
ISV can be performed on saturated soils, but the initial application of
current will be used to volatilize the moisture in the soil or sludge
in the vicinity of a starter path of glass frit and graphite. Once this
is done, the vitrification process begins. Sludges must contain a
sufficient amount of glass forming material (non-volatile, non-destructible
solids) to produce a molten mass that will destroy, remove, or immobilize
the organic and inorganic pollutants.
The limiting nature of the ISV process is related to (1) the presence
of groundwater in a soil of waste that is highly .permeable, (2) the presence
of buried metal , (3) and the pressure that is maintained on the off-gas
treatment system pressure. First, the system as mentioned previously,
can operate in saturated soils and is most effective where permeabilities
are 1 x 10"^ cm/sec or less. Second, the metal limits for a setting are 5%
of the melt weight and less than 90% continuous metal between the electrodes,
Third, the off-gas treatment system must maintain a negative pressure to
prevent loss of contaminants by air emissions around the hood.
The limiting criteria of soil or sludge inclusions with respect to
off-gas treatment system pressure are as follows:
Situation ' Criteria
1. Combustible Liquids 9600 Ib/yd of depth
or 7% by wt
2. Void Volumes 5.6 yd3 or 152 ft3
3. Combustible Packages 1.2 yd3 or 32 ft3
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4. Combustible Solids, with 6400 Ib/yd of depth
30% soil or 4-7% by wt
IV. Detailed Description of Process and Emissions/Residues
Pretreatment of contamined soils or sludges is not always necessary
when using ISV. The materials are treated in-place and high moisture
sludge can be vitrified without pretreatment (a sludge with 70 wt% moisture
has been tested). Conditions exist where restaging or dewatering the
contaminated soils or sludges may be considered for economic reasons,
however. For instance, contamination depths of less than 15 ft could
be more economically vitrified if they were excavated and stockpiled so
that more material could be processed in a single setting. This reduces
the amount of downtime for equipment between settings.
Another example of where staging would be beneficial deals with high
moisture content sludges that exhibit great volume reductions (greater
than a factor of 5) when vitrified. Continuous feeding can greatly
reduce operational costs by vitrifying three or more times the volume of
material in a single setting. Dewatering contaminated soils or sludges
may be considered as an economic alternative to avoid the processing
costs of evaporating moisture from wet soils. If dewatering and treatment
of the waste water can be accomplished at costs less than those for ISV
($200/ton), then they should be considered as a pretreatment alternative
prior to vitrification of residual solids.
A summary of decontamination factors in the soil and off gas system
is given below:
DECONTAMINATION FACTORS*
Contaminant Soil Off-Gas Overall
Mo, Sr, Pu, Am, U 1Q3 to 105 105 108 to 1010
Sb, Te, Ru, Cs 102 to 103 - '"104 106 to 107
Cd, Pb 10 104 105
F 102 l()5 .10?
NOX 10^ 103 105
S02 1 103 to 104
PCBs 103 to 104 >103 >106
light organics 102 to 104 >103 >105
*Decontamination factor is measured as the reciprocal of (1-Rf), where Rf
is the retention or destruction factor, (e.g., 99.999% removal = 105)
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The generation of byproducts may be minimized or eliminated in many
cases with ISV. The only byproducts generated with the process are
approximately 2000 liters of scrub solution for every 400 to 800 tons of
contaminated soil and,.four 2 ft x 2 ft square charcoal adsorbers/filters
for every 4000 to 8000 tons of contaminated soil vitrified. As reported
by BNW, none of the 20 large or pilot scale tests performed to date have
ever produced a regulated, hazardous waste. The byproducts, never contained
any concentrations of regulated material and consequently were disposed
of in the chemical process sewer serving the Hanford Reservation. However
in the event a regulated scrub solution is produced as a result of
vitrification, such as could occur with RGB-contaminated soil, the scrub
solution would be treated through an activated charcoal bed prior to
scrub solution disposal. The charcoal bed and adsorbers/filters would be
disposed of in a future ISV setting on site as part of the processing
operation.
Figure 1. Process Diagram for In Situ Vitrification
(From Battelle Pacific Northwest Labortories)
V. Safety/Honitoring Equi pment
The nature of ISV tends to reduce potential hazards to workers and the
lublic. Handling of the wastes is eliminated or minimized because treatment
s performed in-place. Electrode installation has also been developed
ith pile-driving techniques so that contamination is riot brought to the
irface.
The potential hazards of greatest concern are exposure to gaseous
;ssions during a loss of confinement in the hood and electric shock.
se and other accident scenarios have been analyzed under the Department
Energy's ISV program for transuranic contaminated soils. The analysis
shown that under a maximum release event with a worker breathing off-gas
s directly without protection for five minutes, no significant health
:ts were identified. The potential for electric shock is minimized
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VII. Technology Requirements
o Power Supply - A power supply is needed, provided by a utility or by
on-site electric generators. The current field scale equipment can
operate over a range of 4000 volts (V) to 400V per phase and 450 amps
(A) to 4000 A per phase.
o Water and Sewer - The technology does not require a continuous supply
of water. Water requirements can be met by tanker truck. No sewer
access is needed.
o Roads - A road sufficient to support the semi-trailer mounted system
must be available to reach the site (80,000 Ibs combined weight for each
tractor/trailer assembly).
o Land Area and Characteristics - The system works most effectively on
flat, smooth surfaces which allow for efficient capture of fumes and
gases by the off-gas hood. The staging area for the system (trailer
locations) must be strong enough to support the weight of the equipment.
o Climate and Seasonal Restrictions - None to of although water
tables are usually lower in the summer than winter, thereby providing
a potentially more cost effective and efficient operation.
o Geographical Location - No restrictions provided access by tractor
trailer is possible and sufficient site staging has occurred.
o Hydrological Conditions - In the presence of groundwater the system
works best at a permeability of less than 1 x 10"5 cm/sec. Operation
in the 1 x 10"^ to 1 x 10"^ cm/sec range is marginal unless temporary
groundwater diversion schemes are utilized. In the absence of
groundwater, no restrictions exist.
o Specific Waste Requirements - See Section I,"'II, III, and IV.
o Approximate Land Area for Treatment - The process, as proposed for
soils or sludges that are hazardous, occurs in settings with one
setting vitrifying a 20 ft x 20 ft area. Vitrification depths are
typically 20 ft but the system has been tested to a depth of 24 ft.
o Special Emergency Response Capabilities - The unit is self contained.
No support services are needed.
o Special Work Safety, Public Health, and/or Environmental Concerns That
Might Impact Site Selection - See Section V.
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TREATMENT PROCESS: Biological Treatment Enhanced By
Powdered Activated Carbon Treatment (PACT) With Wet Air
Oxidation (WAO)
DEVELOPER: Zimpro Environmental Control Systems
Rothschild, Wisconsin
TECHNOLOGY DESCRIPTION
Biological treatment of organic wastewater is enhanced by
powdered activated carbon treatment (PACT). Powdered
activated carbon is added to the aeration basin, and
adsorbable organic compounds are retained on the carbon with
the sludge solids. Adsorbed compounds are recycled to the
aeration basin with the carbon and activated sludge. This
provides longer retention time in the treatment system for
improved biodegradation of some organic compounds.
Adsorbable inorganics are also retained on the carbon,
minimizing their impact on the biological process. A
polymer is added to improve solids capture in the clarifier.
Excess solids are removed from the clarifier underflow.
Wet air oxidation is used to oxidize high organic-strength
wastewaters at temperatures of 400°F to 600°F and pressures
of 500 to 1,900 psig. Several configurations combining WAO
with the PACT process are possible. High-strength organic
wastewaters can be pretreated with WAO to improve
biodegradation by the PACT process. Waste activated sludge
and carbon from the PACT process can be treated by WAO. In
one scenario, WAO is used to regenerate the carbon for
recycling to the aeration basin. If the retention of
organic or inorganic contaminants prevents carbon recycle,
high temperature wet air oxidation can be used to treat the
waste solids prior to disposal. High temperature wet air
oxidation uses temperatures of 260°C to 320 °C which are
higher than WAO, and a solid ash residue is produced. The
choice of configuration will depend on site specific
conditions.
The PACT system has been successfully applied to municipal
wastewater, industrial wastewater, and hazardous wastewaters
such as leachate, contaminated groundwater, and process
wastewater. Organic compounds, herbicides, and organic
wastewaters with metals have been treated. Wastes
containing herbicides were pretreated by wet air oxidation.
Metal-bearing wastes have been pretreated by pH adjustment
to precipitate the metals. Zimpro data indicates a 72 to
77 percent reduction in COD during the treatment of
hazardous wastewaters, and an 80 to 90 percent reduction in
the concentration of hazardous constituents.
BOS22/005
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