SEPA
United States
Environmental Protection
Agency
EPA/540/M5-91/009
February 1992
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
Slurry Biodegradation
International Technology Corporation
Technology Description: This technology uses a slurry-phase
bioreactor in which the soil is mixed with water to form a slurry.
Microorganisms and nutrients are added to the slurry to enhance
the biodegradation process, which converts organic wastes into
relatively harmless byproducts of microbial metabolism and inor-
ganic salts. Figure 1 is a schematic of a slurry biodegradation
process.
After the contaminated waste material is collected and screened
to remove oversized material, it is mixed with water to form a
slurry. The slurry is then passed through a milling process to
achieve a slurry with a grain size distribution suitable for charging
to the reactors. The slurry is fed to a continuously stirred tank
reactor which is supplemented with oxygen (air), nutrients, and
when necessary, a specific inoculum of microorganisms to en-
hance the biodegradation process. The residence time in the
bioreactor varies with the soil or sludge matrix; physical/chemical
nature of the contaminant, including concentration; and the bio-
degradability of the contaminants. Once biodegradation of the
contaminants is completed, the treated slurry is sent to a separa-
tion/dewatering system.
The solids may be further treated if they still contain organic
contaminants. The process water can be treated in an onsite
treatment system prior to discharge or it can be recycled to the
Waste
Pretreatment
Water
Oxygen
Nutrients
Bio Reactors
front end of the system for slurrying. Air emissions are possible
during operation of the system; hence, depending on the waste
characteristics, air pollution control, such as activated carbon,
may be necessary.
The reactor selected for the SITE Demonstration was a 60-liter
EIMCO Biolift™ reactor. These reactors are made of stainless
steel and equipped with agitation, aeration, and temperature
controls. These reactors can be sampled from the three sam-
pling ports located along the side of the reactor at three vertical
penetrations through the reactor wall.
Waste Applicability: Slurry biodegradation has been shown to
be effective in treating highly contaminated soils and sludges that
have contaminant concentrations ranging from 2,500 mg/kg to
250,000 mg/kg. It has the potential to treat a wide range of
organic contaminants such as pesticides, fuels, creosote, penta-
chlorophenol, and polychlorinated biphenyls (PCBs). It has been
used to treat coal tars, refinery wastes, hydrocarbons, and wood-
preserving wastes. Slurry biodegradation is not effective in
treating inorganics, including heavy metals.
Demonstration Results: The pilot-scale demonstration of slurry
biodegradation technology was conducted at the U.S. EPA Test
Emissions
Control
Treated
Emissions
Dewatering
Water
->• Solids
-^ Oversized Rejects
Figure 1. Slurry Biodegradation Process.
Printed on Recycled Paper
-------
United States
Environmental Protection
Agency
EPA/540/M5-91/009
February 1992
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
Slurry Biodegradation
International Technology Corporation
Technology Description: This technology uses a slurry-phase
bioreactor in which the soil is mixed with water to form a slurry.
Microorganisms and nutrients are added to the slurry to enhance
the biodegradation process, which converts organic wastes into
relatively harmless byproducts of microbial metabolism and inor-
ganic salts. Figure 1 is a schematic of a slurry biodegradation
process.
After the contaminated waste material is collected and screened
to remove oversized material, it is mixed with water to form a
slurry. The slurry is then passed through a milling process to
achieve a slurry with a grain size distribution suitable for charging
to the reactors. The slurry is fed to a continuously stirred tank
reactor which is supplemented with oxygen (air), nutrients, and
when necessary, a specific inoculum of microorganisms to en-
hance the biodegradation process. The residence time in the
bioreactor varies with the soil or sludge matrix; physical/chemical
nature of the contaminant, including concentration; and the bio-
degradability of the contaminants. Once biodegradation of the
contaminants is completed, the treated slurry is sent to a separa-
tion/dewatering system.
The solids may be further treated if they still contain organic
contaminants. The process water can be treated in an onsite
treatment system prior to discharge or it can be recycled to the
Waste
Pretreatment
Water
Oxygen
Nutrients
Bio Reactors
front end of the system for slurrying. Air emissions are possible
during operation of the system; hence, depending on the waste
characteristics, air pollution control, such as activated carbon,
may be necessary.
The reactor selected for the SITE Demonstration was a 60-liter
EIMCO Biolift™ reactor. These reactors are made of stainless
steel and equipped with agitation, aeration, and temperature
controls. These reactors can be sampled from the three sam-
pling ports located along the side of the reactor at three vertical
penetrations through the reactor wall.
Waste Applicability: Slurry biodegradation has been shown to
be effective in treating highly contaminated soils and sludges that
have contaminant concentrations ranging from 2,500 mg/kg to
250,000 mg/kg. It has the potential to treat a wide range of
organic contaminants such as pesticides, fuels, creosote, penta-
chlorophenol, and polychlorinated biphenyls (PCBs). It has been
used to treat coal tars, refinery wastes, hydrocarbons, and wood-
preserving wastes. Slurry biodegradation is not effective in
treating inorganics, including heavy metals.
Demonstration Results: The pilot-scale demonstration of slurry
biodegradation technology was conducted at the U.S. EPA Test
Emissions
Control
Treated
Emissions
Dewatering
Water
Solids
Oversized Rejects
Figure 1. Slurry Biodegradation Process.
Printed on Recycled Paper
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