| Technology |
Description |
| Soil,
Sediment, and Sludge Technologies |
| 3.1 In Situ
Biological Treatment |
| Bioventing |
Oxygen is delivered to contaminated
unsaturated soils by forced air movement (either
extraction or injection of air) to increase oxygen
concentrations and stimulate biodegradation. |
| Enhanced
Biodegradation |
The activity of naturally occurring
microbes is stimulated by circulating water-based
solutions through contaminated soils to enhance in situ
biological degradation of organic contaminants.
Nutrients, oxygen, or other amendments may be used to
enhance biodegradation and contaminant desorption from
subsurface materials. |
| Landfarming |
Contaminated soils are periodically turned over or
tilled into the soil to aerate the waste. |
| Natural Attenuation |
Natural subsurface processes - such as dilution,
volatilization, biodegradation, adsorption, and chemical
reactions with subsurface materials - are allowed to
reduce contaminant concentrations to acceptable levels. |
| Phytoremediation |
Phytoremediation is a set of processes that use
plants to clean contamination in soil, ground water,
surface water, sediment, and air. |
| 3.2 In Situ
Physical/Chemical Treatment |
| Electrokinetic Separation |
The Electrokinetic Remediation (ER) process removes
metals and organic contaminants from low permeability
soil, mud, sludge, and marine dredging. ER uses
electrochemical and electrokinetic processes to desorb,
and then remove, metals and polar organics. This in situ
soil processing technology is primarily a separation and
removal technique for extracting contaminants from soils. |
| Fracturing |
Pressurized air is injected beneath the
surface to develop cracks in low permeability and
over-consolidated sediments, opening new passageways that
increase the effectiveness of many in situ processes and
enhance extraction efficiencies. |
| Soil Flushing |
Water, or water containing an additive to
enhance contaminant solubility, is applied to the soil or
injected into the ground water to raise the water table
into the contaminated soil zone. Contaminants are leached
into the ground water, which is then extracted and
treated. |
| Soil Vapor Extraction |
Vacuum is applied through extraction
wells to create a pressure/concentration gradient that
induces gas-phase volatiles to diffuse through soil to
extraction wells. The process includes a system for
handling off-gases. This technology also is known as in
situ soil venting, in situ volatilization, enhanced
volatilization, or soil vacuum extraction. |
| Solidification/Stabilization |
Contaminants are physically bound or
enclosed within a stabilized mass (solidification), or
chemical reactions are induced between the stabilizing
agent and contaminants to reduce their mobility
(stabilization). |
| 3.3 In Situ
Thermal Treatment |
| Thermal
Treatment |
Steam/hot air injection or
electromagnetic/fiber optic/radio frequency/electrical
conduction heating is used to increase the mobility of
volatiles and facilitate extraction. The process includes
a system for handling off-gases. |
| Technology |
Description |
| Soil,
Sediment, and Sludge Technologies |
| 3.4 Ex Situ Biological Treatment |
| Biopiles |
Excavated soils are mixed with soil amendments and
placed in aboveground enclosures. Processes include
prepared treatment beds, biotreatment cells, soil piles,
and composting. |
| Composting |
Contaminated soils are excavated and mixed with
bulking agents and organic amendments such as wood chips,
animal and vegetative wastes, which are added to enhance
the porosity and organic content of the mixture to be
decomposed. |
| Genetically Engineered Organisms |
Genetically engineered organisms refer to
microorganisms that have undergone external processes by
which its basic set of genes has been altered. |
| Landfarming |
Contaminated soils are applied onto the soil surface
and periodically turned over or tilled into the soil to
aerate the waste. |
| Slurry Phase Biological Treatment |
An aqueous slurry is created by combining soil or
sludge with water and other additives. The slurry is
mixed to keep solids suspended and microorganisms in
contact with the soil contaminants. Upon completion of
the process, the slurry is dewatered and the treated soil
is disposed of. |
| 3.5 Ex Situ Physical/Chemical
Treatment |
| Chemical Extraction |
Waste contaminated soil and extractant are mixed in
an extractor, dissolving the contaminants. The extracted
solution is then placed in a separator, where the
contaminants and extractant are separated for treatment
and further use. |
| Chemical Reduction/Oxidation |
Reduction/oxidation chemically converts hazardous
contaminants to non-hazardous or less toxic compounds
that are more stable, less mobile, and/or inert. The
oxidizing agents most commonly used are ozone, hydrogen
peroxide, hypochlorites, chlorine, and chlorine dioxide. |
| Dehalogenation |
Reagents are added to soils contaminated with
halogenated organics. The dehalogenation process is
achieved by either the replacement of the halogen
molecules or the decomposition and partial volatilization
of the contaminants. |
| Separation |
Separation techniques concentrate contaminated solids
through physical and chemical means. These processes seek
to detach contaminants from their medium (i.e., the soil,
sand, and/or binding material that contains them). |
| Soil Washing |
Contaminants sorbed onto fine soil particles are
separated from bulk soil in an aqueous-based system on
the basis of particle size. The wash water may be
augmented with a basic leaching agent, surfactant, pH
adjustment, or chelating agent to help remove organics
and heavy metals. |
| Soil Vapor Extraction |
A vacuum is applied to a network of aboveground
piping to encourage volatilization of organics from the
excavated media. The process includes a system for
handling off-gases. |
| Solar Detoxification |
Solar detoxification is a process that destroys
contaminants by using the ultraviolet energy in sunlight.
|
| Solidification/Stabilization |
Contaminants are physically bound or enclosed within
a stabilized mass (solidification), or chemical reactions
are induced between the stabilizing agent and
contaminants to reduce their mobility (stabilization). |
| Technology |
Description |
| Soil,
Sediment, and Sludge Technologies |
| 3.6 Ex Situ Thermal Treatment |
| Hot Gas Decontamination |
The process involves raising the temperature of the
contaminated equipment or material for a specified period
of time. The gas effluent from the material is treated in
an afterburner system to destroy all volatilized
contaminants. |
| Incineration |
High temperatures, 871-1,204 °C (1,600- 2,200 °F),
are used to combust (in the presence of oxygen) organic
constituents in hazardous wastes. |
| Open Burn/Open Detonation |
In open burn operations, explosives or munitions are
destroyed by self-sustained combustion, which is ignited
by an external source, such as flame, heat, or a
detonatable wave (that does not result in a detonation).
In open detonation operations, detonatable explosives and
munitions are destroyed by a detonation, which is
initiated by the detonation of a disposal charge. |
| Pyrolysis |
Chemical decomposition is induced in organic
materials by heat in the absence of oxygen. Organic
materials are transformed into gaseous components and a
solid residue (coke) containing fixed carbon and ash. |
| Thermal Desorption |
Wastes are heated to volatilize water and organic
contaminants. A carrier gas or vacuum system transports
volatilized water and organics to the gas treatment
system. |
| 3.7 Containment |
| Landfill Cap |
Landfill caps are used for contaminant source
control. |
| Water Harvesting Vegetative Cover |
Water harvesting vegetative cover is a land cover
that, through engineered vegetative design, enhances
evaporation, plant transpiration, and moisture removal
from the soil. |
| 3.8 Other Treatment Technologies |
| Excavation, Retrieval, and Off-Site
Disposal |
Contaminated material is removed and transported to
permitted off-site treatment and disposal facilities.
Pretreatment may be required. |
| Technology |
Description |
| Ground Water,
Surface Water, and Leachate Technologies |
| 3.9 In Situ Biological Treatment |
| Co-metabolic Treatment |
Injection of a dilute solution of liquids and/or
gases (e.g., toluene, methane or oxygen) into the
contaminated ground water zone to enhance the rate of
methanotrophic biological degradation of organic
contaminants. |
| Enhanced Biodegradation |
The rate of biodegradation of organic contaminants by
microbes is enhanced by increasing the concentration of
electron acceptors in ground water. Oxygen is the main
electron acceptor for aerobic biodegradation. Nitrate can
serve as an alternative electron acceptor under anaerobic
conditions. |
| Natural Attenuation |
Natural subsurface processes—such as dilution,
volatilization, biodegradation, adsorption, and chemical
reactions with subsurface materials—are allowed to
reduce contaminant concentrations to acceptable levels. |
| Phytoremediation of Organics |
Phytoremediation is a set of processes that uses
plants to clean contamination, particularly organic
substances, in ground water and surface water. |
| 3.10 In Situ Physical/Chemical
Treatment |
| Aeration |
Aeration is the process by which the area of contact
between water and air is increased, either by natural
methods or by mechanical devices. |
| Air Sparging |
Air is injected into saturated matrices to remove
contaminants through volatilization. |
| Bioslurping |
Bioslurping combines the two remedial approaches of
bioventing and vacuum-enhanced free-product recovery.
Bioventing stimulates the aerobic bioremediation of
hydrocarbon-contaminated soils. Vacuum-enhanced
free-product recovery extracts LNAPLs from the capillary
fringe and the water table. |
| Directional Wells |
Drilling techniques are used to position wells
horizontally, or at an angle, to reach contaminants not
accessible by direct vertical drilling. |
| Dual Phase Extraction |
A high vacuum system is applied to simultaneously
remove various combinations of contaminated ground water,
separate-phase petroleum product, and hydrocarbon vapor
from the subsurface. |
| Fluid/Vapor Extraction |
A high vacuum system is applied to simultaneously
remove liquid and gas from low permeability or
heterogeneous formations. |
| Hot Water or Steam
Flushing/Stripping |
Steam is forced into an aquifer through injection
wells to vaporize volatile and semivolatile contaminants.
Vaporized components rise to the unsaturated zone where
they are removed by vacuum extraction and then treated. |
| Hydrofracturing |
Injection of pressurized water through wells cracks
low permeability and over-consolidated sediments. Cracks
are filled with porous media that serve as avenues for
bioremediation or to improve pumping efficiency. |
| In-Well Air Stripping |
Air is injected into a double screened well, lifting
the water in the well and forcing it out the upper
screen. Simultaneously, additional water is drawn in the
lower screen. Once in the well, some of the VOCs in the
contaminated ground water are transferred from the
dissolved phase to the vapor phase by air bubbles. The
contaminated air rises in the well to the water surface
where vapors are drawn off and treated by a soil vapor
extraction system. |
| Passive/Reactive Treatment
Walls |
These barriers allow the passage of water while
prohibiting the movement of contaminants by employing
such agents as chelators (ligands selected for their
specificity for a given metal), sorbents, microbes, and
others. |
| Technology |
Description |
| Ground Water,
Surface Water, and Leachate Technologies |
| 3.11 Ex Situ Biological
Treatment |
| Bioreactors |
Contaminants in extracted ground water are put into
contact with microorganisms in attached or suspended
growth biological reactors. In suspended systems, such as
activated sludge, contaminated ground water is circulated
in an aeration basin. In attached systems, such as
rotating biological contractors and trickling filters,
microorganisms are established on an inert support
matrix. |
| Constructed Wetlands |
The constructed wetlands-based treatment technology
uses natural geochemical and biological processes
inherent in an artificial wetland ecosystem to accumulate
and remove metals and other contaminants from influent
waters. |
| 3.12 Ex Situ Physical/Chemical
Treatment |
| Adsorption/ Absorption |
In liquid adsorption, solutes concentrate at the
surface of a sorbent, thereby reducing their
concentration in the bulk liquid phase. |
| Air Stripping |
Volatile organics are partitioned from ground water
by increasing the surface area of the contaminated water
exposed to air. Aeration methods include packed towers,
diffused aeration, tray aeration, and spray aeration. |
| Granulated Activated
Carbon (GAC)/Liquid Phase Carbon Adsorption |
Ground water is pumped through a series of canisters
or columns containing activated carbon to which dissolved
organic contaminants adsorb. Periodic replacement or
regeneration of saturated carbon is required. |
| Ion Exchange |
Ion exchange removes ions from the aqueous phase by
exchange with innocuous ions on the exchange medium. |
Precipitation/
Coagulation/Flocculation |
This process transforms dissolved contaminants into
an insoluble solid, facilitating the contaminant's
subsequent removal from the liquid phase by sedimentation
or filtration. The process usually uses pH adjustment,
addition of a chemical precipitant, and flocculation. |
| Separation |
Separation techniques concentrate contaminated waste
water through physical and chemical means. |
| Sprinkler Irrigation |
Wastewater is distributed over the top of the filter
bed through which wastewater is trickled. The organic
contaminants in wastewater are degraded by the
microorganisms attached to the filter medium. |
| Ultraviolet Oxidation |
Ultraviolet (UV) radiation, ozone, and/or hydrogen
peroxide are used to destroy organic contaminants as
water flows into a treatment tank. An ozone destruction
unit is used to treat off-gases from the treatment tank. |
| 3.13 Containment |
| Deep
Well Injection |
Deep well injection is a liquid waste disposal
technology. This alternative uses injection wells to
place treated or untreated liquid waste into underground
reservoirs where it will not cause environmental harm. |
| Ground Water Pumping |
Ground water pumping is a component of many
pump-and-Treat processes, which are some of the most
commonly used ground water remediation technologies at
contaminated sites. |
| Slurry Walls |
These subsurface barriers consist of vertically
excavated trenches filled with slurry. The slurry,
usually a mixture of bentonite and water, hydraulically
shores the trench to prevent collapse and retards ground
water flow. |
| Technology |
Description |
| Air
Emissions/Off-Gas Treatment Technologies |
| 3.14 Air Emissions/Off-Gas
Treatment |
| Biofiltration |
Vapor-phase organic contaminants are pumped through a
soil bed and sorb to the soil surface where they are
degraded by microorganisms in the soil. |
| High Energy Corona |
The HEC process uses high-voltage electricity to
destroy VOCs at room temperature. |
| Membrane Separation |
This organic vapor/air separation technology involves
the preferential transport of organic vapors through a
nonporous gas separation membrane (a diffusion process
analogous to putting hot oil on a piece of waxed paper). |
| Oxidation |
Organic contaminants are destroyed in a high
temperature 1,000°C (1,832 °F) combustor. Trace
organics in contaminated air streams are destroyed at
lower temperatures, 450 °C (842 °F), than conventional
combustion by passing the mixture through a catalyst. |
| Vapor Phase Carbon
Adsorption |
Off-gases are pumped through a series of canisters or
columns containing activated carbon to which organic
contaminants adsorb. Periodic replacement or regeneration
of saturated carbon is required. |