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4.5 Overview of available containment (CT) and source removal (SRT) remediation techniques

In Table 4.6, Table 4.7 and Table 4.8, an overview of available containment and removal remediation techniques is given together with an indication of the groups of substances for which they are suitable. These tables are taken from [IAEA-2006b] and combine both techniques for recovering contaminants from soils and groundwater, as well as techniques for concentrating and conditioning contaminants.

The Tables 4.6, 4.7 and 4.8 have to be seen as three different cross-reference tables:

  • In Table 4.6 remediation techniques are sorted according to their planning approach or principle. Principles of removal remediation techniques are divided into 4 groups: physical, chemical, biological and thermal;
  • In Table 4.7 remediation techniques are sorted according to the effective media (groundwater, soil, sludge) the techniques are usable for;
  • In Table 4.8 remediation techniques are sorted according to the radioactive contaminants the techniques are usable for.

It must be emphasized that almost certainly and for almost all practical cases any of the methods and technologies discussed will not ‘remediate’ a given contamination on its own. Owing to physicochemical properties, behaviour and initial conditions, any one technology will leave behind a certain residual level of contamination. Other remediation technologies, more appropriate and effective for this residual contamination level, will then have to be applied.

Table 4.9 provides an overview of the remediation technologies discussed further in this document. These technologies are divided in two main groups:

  • Containment technologies (CT);
  • Source term removal technologies (STRT)

In both main groups sub groups exist that can be based on e.g. physical techniques, chemical techniques, biological techniques, in-situ or ex-situ, etc.
.

Technology Medium Conta-
minant
Brief characterization Detailed
description
Planning approach
or principle
In-situ bioremediation Soil Organic compounds Enzyme activity of natural soil microbes to break down contaminants is stimulated by the injection of nutrient, oxygen (for aerobic microbes) or surfactant containing solutions.

Section 4.5.8.2 Biological removal
Biodegradation Soil Organic compounds The generic process utilized in composting, land farming and other bioremediation processes.

Section 4.5.9 Biological removal
Composting Soil Organic compounds Contaminated soil is excavated and placed in specialized facilities. Cellulose, biomass, nutrients and sometimes additional indigenous microbes are added to promote degradation. Specialized bacteria may be added to break down a particular compound.

Section 4.5.9.1 Biological removal
Bioventing Soil Organic compounds In-situ process of injecting air into contaminated soil at an optimal rate, increasing soil O2 concentration and thereby stimulating the growth of indigenous aerobic bacteria. Low injection rates keep volatilization to a minimum.

Section 4.5.8.2 Biological removal
Ex-situ bioremediation Soil Organic compounds The enzyme activity of natural soil microbes to break down contaminants is stimulated in bioreactors, treatment beds and lagoons by the addition of nutrients, oxygen (for aerobic microbes), surfactant, etc. to soils or surface water and groundwater. The process is similar to composting or sewage treatment.

Section 4.5.9.1 Biological removal
Land farming Soil Organic compounds Once excavated, contaminated soils are spread over a clean area. The soil is aerated by regular turning or tilling to promote biodegradation.

Section 4.5.9.1 Biological removal
Slurry phase bioremediation Soil and sludge Organic compounds An engineered process for treating contaminated soils or sludge that relies upon the mobilization of contaminants to the aqueous phase, where they are susceptible to microbial degradation.

Section 4.5.9.1 Biological removal
Biosorption Surface water and groundwater Radionuclides and heavy metals Certain micro-organisms take up metal ions in their cell walls or on their surface, a process which can be used to concentrate these contaminants. Facilities can be designed as bioreactors or like sewage treatment plants (organic stationary phase).

Section 4.5.9.1 Biological removal
Constructed wetlands Surface water and groundwater Radionuclides and heavy metals Contaminated waters are routed into artificial ‘swamps’, where the metals are taken up by plant tissue. The plants are harvested and incinerated. The resulting ashes are disposed off.

Section 4.5.5.3 Biological removal
Biological wastewater treatment Surface water and groundwater Organic compounds (radionuclides and heavy metals) Biological sewage treatment plants will also destroy certain organic contaminants. Bacterial populations specialized for certain contaminants may be used. The resulting sludge will also contain the majority of radionuclides and heavy metals and can be collected for further treatment.

N/A Biological removal
Reactive barriers Groundwater Organic compounds, heavy metals and radionuclides This is an in situ method of funnelling the natural or enhanced groundwater flow through a physical barrier containing reactive chemicals (oxidation or precipitation), metal catalysts (redox reactions), bacteria (biodegradation) or adsorbents.

Section 4.5.1.9 Containment
Isolation Soil All types Physical barriers, such as slurry walls or sheet piling, are installed to prevent movement of contaminants.

Sections 4.5.1.1 to 4.5.1.8 Containment
In-situ chemical oxidation Soil and groundwater Organic compounds (heavy metals and radionuclides) The injection of ozone (O3), hydrogen peroxide (H2O2) or chlorine compounds induces a redox reaction that chemically converts contaminants into less toxic compounds. This may reduce the mobility of contaminants throughout a plume.

Section 4.5.4 Containment
In-situ solidification Soil and sludge Radionuclides and heavy metals The aim is to lower the mobility of contaminants by injecting binding materials (cement, organic or inorganic polymers) that react with the contaminant, the water and/or the soil to produce a low solubility solid.

Section 4.5.2 Containment
Vitrification Soil and sludge Radionuclides and heavy metals The contaminated material is mixed with glass forming constituents and fluxes to produce solid glass blocks or slag-like products.

N/A Containment
In-situ vitrification (ISV) Soil and sludge Radionuclides and heavy metals Soil is vitrified in situ to immobilize contaminants by applying electrical resistance or inductive melting.

Sections 4.5.3 to 4.5.3.3 Containment
Ex-situ solidification Soil or sludge Radionuclides and heavy metals (organic compounds) A low solubility solid is produced from contaminated soil by mixing it with a reactive binder (cement, gypsum, organic or inorganic polymer). The solid material may be disposed off in-situ or at a designated repository.

Section 4.3.3.4 Containment
Biosorption Surface water and groundwater Radionuclides and heavy metals Certain microorganisms take up metal ions in their cell walls or on their surface; the processes involved can be used to concentrate these contaminants. Facilities can be designed as bioreactors or like sewage treatment plants (organic stationary phase).

Section 4.5.9 Containment
Ex-situ oxidation Groundwater Organic compounds Organic contaminants are oxidatively destroyed in extracted groundwater by UV irradiation, ozone (O3) sparging and/or hydrogen peroxide (H2O2). Off-gases are generally treated by ozonation.

Section 4.5.9 Chemical removal
Ex-situ chemical treatment Groundwater Radionuclides and heavy metals (organic compounds) Ion exchange, precipitation, reverse osmosis, etc. are applied to concentrate contaminants for further conditioning.

Section 4.5.9 Chemical removal
Ex-situ dehalogenation Soil Halogenated volatile organic compounds Contaminants in excavated soils are dehalogenated using one of two processes. Base catalysed dehalogenation involves mixing the soils with sodium hydroxide (NaOH) and a catalyst in a rotary kiln. In glycolate dehalogenation, an alkaline polyethylene glycol (APEG) reagent dehalogenates the volatile organic compounds in a batch reactor. The resulting compound from either reaction is either non-hazardous or less toxic.

N/A Chemical removal
Pump and treat systems Groundwater All types Groundwater is pumped to the surface and treated by a variety of methods. The efficiency depends on the type of contaminant and the concentration.

Section 4.5.6 Physical removal
Funnel and gate systems Groundwater All types The pump and treat methods and reactive barriers can be improved by constructing impervious walls, funnelling the water flow towards the well or the reactive barrier.

Section 4.5.1.9 Physical removal
Ex-situ filtration Groundwater Radionuclides and heavy metals Contaminated ground or surface water is passed through a filter column to remove contaminated suspended solids. The resulting filter cake requires further treatment and disposal.

N/A Physical removal
Membrane separation Groundwater Volatile organic compounds A vapour-air separation method is used that involves the diffusion of volatile organic compounds through a non-porous gas separation membrane.

Section 4.5.9 Physical removal
Ex-situ air stripping Groundwater Volatile organic compounds and organic compounds Removes volatiles in pumped surface or groundwater. Stripping towers (e.g., packed columns) have a concurrent flow of gas and liquid. The waste airstream may undergo further treatment by, for example, activated carbon or incineration.

Section 4.5.9 Physical removal
Vacuum extraction Groundwater Volatile organic compounds A vacuum created inside a well forces the groundwater to rise, allowing additional groundwater to flow in. Once in the well, the airflow causes some of the trapped volatile contaminants to vaporize, thus enabling the capture of volatile organic compounds through vapour extraction.

Section 4.5.8.6 Physical removal
Free product recovery Groundwater Organic compounds A non-miscible, liquid phase organic compound, either lighter or heavier than the groundwater, is removed by pumping from a defined horizon.

N/A Physical removal
Air sparging Groundwater and soil Volatile organic compounds and organic compounds A method is used that promotes volatilization of organic compounds by air injection into the saturated zone; also promotes natural aerobic biodegradation.

Section 4.5.7.2 Physical removal
Vapour phase carbon adsorption Off-gases Volatile organic compounds and organic compounds Off-gases collected from ex situ or in situ stripping methods are routed through canisters containing granular activated carbon.

N/A Physical removal
Physical segregation Soil Radionuclides and heavy metals Often contaminants (including radionuclides) adsorb to fine grain size fractions in the soil. Size fractionation by sieving or flotation may thus result in a much smaller volume of contaminated material to be treated.

Section 4.5.9 Physical removal
In-situ soil washing Soil All types This technique consists of flushing contaminated material in situ. It entails the injection and extraction of acidic or basic solutions, with added surfactants, chelates, etc., to dissolve, desorb and remove contaminants.

N/A Physical removal
Ex-situ soil washing Soil All types This ex-situ technique uses pH controlled solutions with the addition of acids or bases, surfactants or chelates to dissolve, desorb and remove contaminants. Organic solvents may be used for organic contaminants. A preceding size fractionation improves efficiency and reduces the volumes of material to be treated.

Section 4.5.9 Physical removal
Soil vapour extraction (SVE) Soil Volatile organic compounds Removes volatile organic compounds from the unsaturated zone by creating a zone of low vapour pressure. Soil vapour extraction is most effective in highly permeable soils.

Section 4.5.8.6 Physical removal
Excavation Soil and sludge All types Contaminated materials are removed from the site and transferred to a designated disposal site. Conditioning may be required before disposal.

Section 4.3.3.3 Physical removal
Rhizo-filtration Groundwater and surface water Metals and radionuclides Process goal: contaminant extraction and capture.
Plants: sunflowers, Indian mustard and water hyacinth.
Status: laboratory and pilot scales.

Section 4.5.8.5 Phyto-remediation
Hydraulic control (plume control) Groundwater and surface water Water soluble organic compounds and inorganic compounds Process goal: contaminant degradation or containment.
Plants: hybrid poplars, cottonwood and willow.
Status: field demonstrations.

N/A Phyto-remediation
Phyto-volatilization Groundwater, soil, sediment and sludge Chlorinated solvents, phyto-volatilization releases (some inorganic compounds (Se, As and Hg) to air) Process goal: contaminant extraction from media and release to air.
Plants: poplars, alfalfa black locust and Indian mustard.
Status: laboratory and field applications.

N/A Phyto-remediation
Phyto-stabilization Soil and sediment As, Cd, Cr, Cu, Hs, Pb and Zn Process goal: contaminant containment.
Plants: Indian mustard, hybrid poplars and grasses.
Status: field applications.

Section 4.5.5.2 Phyto-remediation
Phyto-extraction Soil, sediment and sludge Metals: Ag, Gd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Zn; Radionuclides: 90Sr, 137Cs, 239Pu, 238U, 234U

Process goal: contaminant extraction and capture.
Plants: Indian mustard, pennycress, alyssum, sunflowers and hybrid poplars.
Status: laboratory, pilot and field applications.
Section 4.5.8.4 Phyto-remediation
Vegetative cover (evapo-transpiration cover) Soil, sediment and sludge Organic and inorganic compounds Process goal: contaminant containment and erosion control.
Plants: poplars and grasses.
Status: field applications.

N/A Phyto-remediation
Rhizo-degradation Soil, sediment, sludge and groundwater Organic compound degradation (TPH, PAHsa , pesticides, chlorinated solvents and PCBs)

Process goal: contaminant destruction.
Plants: red mulberry, grasses, hybrid poplar, cat’s tail and rice.
Status: field applications.
N/A Phyto-remediation
Phyto-degradation Soil, sediment, sludge, groundwater and surface water Organic compounds, sludge, chlorinated solvents, groundwater phenols, herbicides and munitions

Process goal: contaminant destruction.
Plants: algae, stonewort, hybrid poplars, black willow and bald cypress.
Status: field demonstrations.
N/A Phyto-remediation
Riparian corridors (non-point source control) Surface water and groundwater Water soluble organic and inorganic compounds Process goal: contaminant destruction.
Plants: poplars.
Status: field applications.

N/A Phyto-remediation
Thermally enhanced soil vapour extraction Soil Volatile organic compounds and organic compounds Contaminated soil is heated by the injection of hot air or steam, or by electrical resistance or microwave heating, thereby volatilizing contaminants. Off-gases are captured for further treatment.

Section 4.5.8.6 Thermal removal
Catalytic oxidation Soil Organic compounds The use of a catalyst helps to lower the reaction temperature, and thus the energy input, for thermal treatment methods.

Section 4.5.9 Thermal removal
Thermal desorption (ex-situ) Soil and sludge Volatile organic compounds and organic compounds Excavated soils and sludge’s are heated to approximately 425°C (high temperature thermal desorption) or to approximately 200°C (low temperature thermal desorption) in an effort to volatilize organic contaminants. An off-gas treatment system is attached to capture and treat vapour phase contaminants.

Section 4.5.9 Thermal removal
Incineration Soil and sludge Organic compounds This process involves the combustion of excavated soils and sludge’s in, for example, rotary kilns or fluidized bed incinerators for the thermal destruction of contaminants. Often conducted off-site, but also on-site in mobile facilities.

Section 4.5.9 Thermal removal
Pyrolysis Soil and sludge Organic compounds This process involves anaerobic thermal decomposition of organic contaminants in excavated soil or sludge.

Section 4.5.9 Thermal removal

Table 4.6 Remediation techniques sorted by planning approach or principle (column 6)
.
.

Technology Medium Conta-
minant
Brief characterization Detailed
description
Planning approach
or principle
Ex-situ air stripping Groundwater Volatile organic compounds and organic compounds Removes volatiles in pumped surface or groundwater. Stripping towers (e.g., packed columns) have a concurrent flow of gas and liquid. The waste airstream may undergo further treatment by, for example, activated carbon or incineration.

Section 4.5.9 Physical removal
Ex-situ chemical treatment Groundwater Radionuclides and heavy metals (organic compounds) Ion exchange, precipitation, reverse osmosis, etc. are applied to concentrate contaminants for further conditioning.

Section 4.5.9 Chemical removal
Ex-situ filtration Groundwater Radionuclides and heavy metals Contaminated ground or surface water is passed through a filter column to remove contaminated suspended solids. The resulting filter cake requires further treatment and disposal.

N/A Physical removal
Ex-situ oxidation Groundwater Organic compounds Organic contaminants are oxidatively destroyed in extracted groundwater by UV irradiation, ozone (O3) sparging and/or hydrogen peroxide (H2O2). Off-gases are generally treated by ozonation.

Section 4.5.9 Chemical removal
Free product recovery Groundwater Organic compounds A non-miscible, liquid phase organic compound, either lighter or heavier than the groundwater, is removed by pumping from a defined horizon.

N/A Physical removal
Funnel and gate systems Groundwater All types The pump and treat methods and reactive barriers can be improved by constructing impervious walls, funnelling the water flow towards the well or the reactive barrier.

Section 4.5.1.9 Physical removal
Membrane separation Groundwater Volatile organic compounds A vapour-air separation method is used that involves the diffusion of volatile organic compounds through a non-porous gas separation membrane.

Section 4.5.9 Physical removal
Pump and treat systems Groundwater All types Groundwater is pumped to the surface and treated by a variety of methods. The efficiency depends on the type of contaminant and the concentration.

Section 4.5.6 Physical removal
Reactive barriers Groundwater Organic compounds, heavy metals and radionuclides This is an in situ method of funnelling the natural or enhanced groundwater flow through a physical barrier containing reactive chemicals (oxidation or precipitation), metal catalysts (redox reactions), bacteria (biodegradation) or adsorbents.

Section 4.5.1.9 Containment
Vacuum extraction Groundwater Volatile organic compounds A vacuum created inside a well forces the groundwater to rise, allowing additional groundwater to flow in. Once in the well, the airflow causes some of the trapped volatile contaminants to vaporize, thus enabling the capture of volatile organic compounds through vapour extraction.

Section 4.5.8.6 Physical removal
Air sparging Groundwater and soil Volatile organic compounds and organic compounds A method is used that promotes volatilization of organic compounds by air injection into the saturated zone; also promotes natural aerobic biodegradation.

Section 4.5.7.2 Physical removal
Phyto-volatilization Groundwater, soil, sediment and sludge Chlorinated solvents, phyto-volatilization releases (some inorganic compounds (Se, As and Hg) to air) Process goal: contaminant extraction from media and release to air.
Plants: poplars, alfalfa black locust and Indian mustard.
Status: laboratory and field applications.

N/A Phyto-remediation
Hydraulic control (plume control) Groundwater and surface water Water soluble organic compounds and inorganic compounds Process goal: contaminant degradation or containment.
Plants: hybrid poplars, cottonwood and willow.
Status: field demonstrations.

N/A Phyto-remediation
Rhizo-filtration Groundwater and surface water Metals and radionuclides Process goal: contaminant extraction and capture.
Plants: sunflowers, Indian mustard and water hyacinth.
Status: laboratory and pilot scales.

Section 4.5.8.5 Phyto-remediation
Vapour phase carbon adsorption Off-gases Volatile organic compounds and organic compounds Off-gases collected from ex situ or in situ stripping methods are routed through canisters containing granular activated carbon.

N/A Physical removal
Biodegradation Soil Organic compounds The generic process utilized in composting, land farming and other bioremediation processes.

Section 4.5.9 Biological removal
Bioventing Soil Organic compounds In-situ process of injecting air into contaminated soil at an optimal rate, increasing soil O2 concentration and thereby stimulating the growth of indigenous aerobic bacteria. Low injection rates keep volatilization to a minimum.

Section 4.5.8.2 Biological removal
Catalytic oxidation Soil Organic compounds The use of a catalyst helps to lower the reaction temperature, and thus the energy input, for thermal treatment methods.

Section 4.5.9 Thermal removal
Composting Soil Organic compounds Contaminated soil is excavated and placed in specialized facilities. Cellulose, biomass, nutrients and sometimes additional indigenous microbes are added to promote degradation. Specialized bacteria may be added to break down a particular compound.

Section 4.5.9.1 Biological removal
Ex-situ bioremediation Soil Organic compounds The enzyme activity of natural soil microbes to break down contaminants is stimulated in bioreactors, treatment beds and lagoons by the addition of nutrients, oxygen (for aerobic microbes), surfactant, etc. to soils or surface water and groundwater. The process is similar to composting or sewage treatment.

Section 4.5.9.1 Biological removal
Ex-situ dehalogenation Soil Halogenated volatile organic compounds Contaminants in excavated soils are dehalogenated using one of two processes. Base catalysed dehalogenation involves mixing the soils with sodium hydroxide (NaOH) and a catalyst in a rotary kiln. In glycolate dehalogenation, an alkaline polyethylene glycol (APEG) reagent dehalogenates the volatile organic compounds in a batch reactor. The resulting compound from either reaction is either non-hazardous or less toxic.

N/A Chemical removal
Ex-situ soil washing Soil All types This ex-situ technique uses pH controlled solutions with the addition of acids or bases, surfactants or chelates to dissolve, desorb and remove contaminants. Organic solvents may be used for organic contaminants. A preceding size fractionation improves efficiency and reduces the volumes of material to be treated.

Section 4.5.9 Physical removal
In-situ bioremediation Soil Organic compounds Enzyme activity of natural soil microbes to break down contaminants is stimulated by the injection of nutrient, oxygen (for aerobic microbes) or surfactant containing solutions.

Section 4.5.8.2 Biological removal
In-situ soil washing Soil All types This technique consists of flushing contaminated material in situ. It entails the injection and extraction of acidic or basic solutions, with added surfactants, chelates, etc., to dissolve, desorb and remove contaminants.

N/A Physical removal
Isolation Soil All types Physical barriers, such as slurry walls or sheet piling, are installed to prevent movement of contaminants.

Sections 4.5.1.1 to 4.5.1.8 Containment
Land farming Soil Organic compounds Once excavated, contaminated soils are spread over a clean area. The soil is aerated by regular turning or tilling to promote biodegradation.

Section 4.5.9.1 Biological removal
Physical segregation Soil Radionuclides and heavy metals Often contaminants (including radionuclides) adsorb to fine grain size fractions in the soil. Size fractionation by sieving or flotation may thus result in a much smaller volume of contaminated material to be treated.

Section 4.5.9 Physical removal
Soil vapour extraction (SVE) Soil Volatile organic compounds Removes volatile organic compounds from the unsaturated zone by creating a zone of low vapour pressure. Soil vapour extraction is most effective in highly permeable soils.

Section 4.5.8.6 Physical removal
Thermally enhanced soil vapour extraction Soil Volatile organic compounds and organic compounds Contaminated soil is heated by the injection of hot air or steam, or by electrical resistance or microwave heating, thereby volatilizing contaminants. Off-gases are captured for further treatment.

Section 4.5.8.6 Thermal removal
In-situ chemical oxidation Soil and groundwater Organic compounds (heavy metals and radionuclides) The injection of ozone (O3), hydrogen peroxide (H2O2) or chlorine compounds induces a redox reaction that chemically converts contaminants into less toxic compounds. This may reduce the mobility of contaminants throughout a plume.

Section 4.5.4 Containment
Phyto-stabilization Soil and sediment As, Cd, Cr, Cu, Hs, Pb and Zn Process goal: contaminant containment.
Plants: Indian mustard, hybrid poplars and grasses.
Status: field applications.

Section 4.5.5.2 Phyto-remediation
Phyto-extraction Soil, sediment and sludge Metals: Ag, Gd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Zn; Radionuclides: 90Sr, 137Cs, 239Pu, 238U, 234U

Process goal: contaminant extraction and capture.
Plants: Indian mustard, pennycress, alyssum, sunflowers and hybrid poplars.
Status: laboratory, pilot and field applications.
Section 4.5.8.4 Phyto-remediation
Vegetative cover (evapo-transpiration cover) Soil, sediment and sludge Organic and inorganic compounds Process goal: contaminant containment and erosion control.
Plants: poplars and grasses.
Status: field applications.

N/A Phyto-remediation
Phyto-degradation Soil, sediment, sludge, groundwater and surface water Organic compounds, sludge, chlorinated solvents, groundwater phenols, herbicides and munitions

Process goal: contaminant destruction.
Plants: algae, stonewort, hybrid poplars, black willow and bald cypress.
Status: field demonstrations.
N/A Phyto-remediation
Rhizo-degradation Soil, sediment, sludge and groundwater Organic compound degradation (TPH, PAHsa , pesticides, chlorinated solvents and PCBs)

Process goal: contaminant destruction.
Plants: red mulberry, grasses, hybrid poplar, cat’s tail and rice.
Status: field applications.
N/A Phyto-remediation
Excavation Soil and sludge All types Contaminated materials are removed from the site and transferred to a designated disposal site. Conditioning may be required before disposal.

Section 4.3.3.3 Physical removal
Ex-situ solidification Soil or sludge Radionuclides and heavy metals (organic compounds) A low solubility solid is produced from contaminated soil by mixing it with a reactive binder (cement, gypsum, organic or inorganic polymer). The solid material may be disposed off in-situ or at a designated repository.

Section 4.3.3.4 Containment
Incineration Soil and sludge Organic compounds This process involves the combustion of excavated soils and sludge’s in, for example, rotary kilns or fluidized bed incinerators for the thermal destruction of contaminants. Often conducted off-site, but also on-site in mobile facilities.

Section 4.5.9 Thermal removal
In-situ solidification Soil and sludge Radionuclides and heavy metals The aim is to lower the mobility of contaminants by injecting binding materials (cement, organic or inorganic polymers) that react with the contaminant, the water and/or the soil to produce a low solubility solid.

Section 4.5.2 Containment
In-situ vitrification (ISV) Soil and sludge Radionuclides and heavy metals Soil is vitrified in situ to immobilize contaminants by applying electrical resistance or inductive melting.

Sections 4.5.3 to 4.5.3.3 Containment
Pyrolysis Soil and sludge Organic compounds This process involves anaerobic thermal decomposition of organic contaminants in excavated soil or sludge.

Section 4.5.9 Thermal removal
Slurry phase bioremediation Soil and sludge Organic compounds An engineered process for treating contaminated soils or sludge that relies upon the mobilization of contaminants to the aqueous phase, where they are susceptible to microbial degradation.

Section 4.5.9.1 Biological removal
Thermal desorption (ex-situ) Soil and sludge Volatile organic compounds and organic compounds Excavated soils and sludge’s are heated to approximately 425°C (high temperature thermal desorption) or to approximately 200°C (low temperature thermal desorption) in an effort to volatilize organic contaminants. An off-gas treatment system is attached to capture and treat vapour phase contaminants.

Section 4.5.9 Thermal removal
Vitrification Soil and sludge Radionuclides and heavy metals The contaminated material is mixed with glass forming constituents and fluxes to produce solid glass blocks or slag-like products.

N/A Containment
Biological wastewater treatment Surface water and groundwater Organic compounds (radionuclides and heavy metals) Biological sewage treatment plants will also destroy certain organic contaminants. Bacterial populations specialized for certain contaminants may be used. The resulting sludge will also contain the majority of radionuclides and heavy metals and can be collected for further treatment.

N/A Biological removal
Biosorption Surface water and groundwater Radionuclides and heavy metals Certain micro-organisms take up metal ions in their cell walls or on their surface, a process which can be used to concentrate these contaminants. Facilities can be designed as bioreactors or like sewage treatment plants (organic stationary phase).

Section 4.5.9.1 Biological removal
Biosorption Surface water and groundwater Radionuclides and heavy metals Certain microorganisms take up metal ions in their cell walls or on their surface; the processes involved can be used to concentrate these contaminants. Facilities can be designed as bioreactors or like sewage treatment plants (organic stationary phase).

Section 4.5.9 Containment
Constructed wetlands Surface water and groundwater Radionuclides and heavy metals Contaminated waters are routed into artificial ‘swamps’, where the metals are taken up by plant tissue. The plants are harvested and incinerated. The resulting ashes are disposed off.

Section 4.5.5.3 Biological removal
Riparian corridors (non-point source control) Surface water and groundwater Water soluble organic and inorganic compounds Process goal: contaminant destruction.
Plants: poplars.
Status: field applications.

N/A Phyto-remediation

Table 4.7 Remediation techniques sorted by effective medium (column 2)
.
.

Technology Medium Conta-
minant
Brief characterization Detailed
description
Planning approach
or principle
Excavation Soil and sludge All types Contaminated materials are removed from the site and transferred to a designated disposal site. Conditioning may be required before disposal.

Section 4.3.3.3 Physical removal
Isolation Soil All types Physical barriers, such as slurry walls or sheet piling, are installed to prevent movement of contaminants.

Sections 4.5.1.1 to 4.5.1.8 Containment
Ex-situ soil washing Soil All types This ex-situ technique uses pH controlled solutions with the addition of acids or bases, surfactants or chelates to dissolve, desorb and remove contaminants. Organic solvents may be used for organic contaminants. A preceding size fractionation improves efficiency and reduces the volumes of material to be treated.

Section 4.5.9 Physical removal
Funnel and gate systems Groundwater All types The pump and treat methods and reactive barriers can be improved by constructing impervious walls, funnelling the water flow towards the well or the reactive barrier.

Section 4.5.1.9 Physical removal
In-situ soil washing Soil All types This technique consists of flushing contaminated material in situ. It entails the injection and extraction of acidic or basic solutions, with added surfactants, chelates, etc., to dissolve, desorb and remove contaminants.

N/A Physical removal
Pump and treat systems Groundwater All types Groundwater is pumped to the surface and treated by a variety of methods. The efficiency depends on the type of contaminant and the concentration.

Section 4.5.6 Physical removal
Phyto-stabilization Soil and sediment As, Cd, Cr, Cu, Hs, Pb and Zn Process goal: contaminant containment.
Plants: Indian mustard, hybrid poplars and grasses.
Status: field applications.

Section 4.5.5.2 Phyto-remediation
Phyto-volatilization Groundwater, soil, sediment and sludge Chlorinated solvents, phyto-volatilization releases (some inorganic compounds (Se, As and Hg) to air) Process goal: contaminant extraction from media and release to air.
Plants: poplars, alfalfa black locust and Indian mustard.
Status: laboratory and field applications.

N/A Phyto-remediation
Ex-situ dehalogenation Soil Halogenated volatile organic compounds Contaminants in excavated soils are dehalogenated using one of two processes. Base catalysed dehalogenation involves mixing the soils with sodium hydroxide (NaOH) and a catalyst in a rotary kiln. In glycolate dehalogenation, an alkaline polyethylene glycol (APEG) reagent dehalogenates the volatile organic compounds in a batch reactor. The resulting compound from either reaction is either non-hazardous or less toxic.

N/A Chemical removal
Phyto-extraction Soil, sediment and sludge Metals: Ag, Gd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Zn; Radionuclides: 90Sr, 137Cs, 239Pu, 238U, 234U Process goal: contaminant extraction and capture.
Plants: Indian mustard, pennycress, alyssum, sunflowers and hybrid poplars.
Status: laboratory, pilot and field applications.

Section 4.5.8.4 Phyto-remediation
Rhizo-filtration Groundwater and surface water Metals and radionuclides Process goal: contaminant extraction and capture.
Plants: sunflowers, Indian mustard and water hyacinth.
Status: laboratory and pilot scales.

Section 4.5.8.5 Phyto-remediation
Biodegradation Soil Organic compounds The generic process utilized in composting, land farming and other bioremediation processes.

Section 4.5.9 Biological removal
Bioventing Soil Organic compounds In-situ process of injecting air into contaminated soil at an optimal rate, increasing soil O2 concentration and thereby stimulating the growth of indigenous aerobic bacteria. Low injection rates keep volatilization to a minimum.

Section 4.5.8.2 Biological removal
Catalytic oxidation Soil Organic compounds The use of a catalyst helps to lower the reaction temperature, and thus the energy input, for thermal treatment methods.

Section 4.5.9 Thermal removal
Composting Soil Organic compounds Contaminated soil is excavated and placed in specialized facilities. Cellulose, biomass, nutrients and sometimes additional indigenous microbes are added to promote degradation. Specialized bacteria may be added to break down a particular compound.

Section 4.5.9.1 Biological removal
Ex-situ bioremediation Soil Organic compounds The enzyme activity of natural soil microbes to break down contaminants is stimulated in bioreactors, treatment beds and lagoons by the addition of nutrients, oxygen (for aerobic microbes), surfactant, etc. to soils or surface water and groundwater. The process is similar to composting or sewage treatment.

Section 4.5.9.1 Biological removal
Ex-situ oxidation Groundwater Organic compounds Organic contaminants are oxidatively destroyed in extracted groundwater by UV irradiation, ozone (O3) sparging and/or hydrogen peroxide (H2O2). Off-gases are generally treated by ozonation.

Section 4.5.9 Chemical removal
Free product recovery Groundwater Organic compounds A non-miscible, liquid phase organic compound, either lighter or heavier than the groundwater, is removed by pumping from a defined horizon.

N/A Physical removal
Incineration Soil and sludge Organic compounds This process involves the combustion of excavated soils and sludge’s in, for example, rotary kilns or fluidized bed incinerators for the thermal destruction of contaminants. Often conducted off-site, but also on-site in mobile facilities.

Section 4.5.9 Thermal removal
In-situ bioremediation Soil Organic compounds Enzyme activity of natural soil microbes to break down contaminants is stimulated by the injection of nutrient, oxygen (for aerobic microbes) or surfactant containing solutions.

Section 4.5.8.2 Biological removal
Land farming Soil Organic compounds Once excavated, contaminated soils are spread over a clean area. The soil is aerated by regular turning or tilling to promote biodegradation.

Section 4.5.9.1 Biological removal
Pyrolysis Soil and sludge Organic compounds This process involves anaerobic thermal decomposition of organic contaminants in excavated soil or sludge.

Section 4.5.9 Thermal removal
Slurry phase bioremediation Soil and sludge Organic compounds An engineered process for treating contaminated soils or sludge that relies upon the mobilization of contaminants to the aqueous phase, where they are susceptible to microbial degradation.

Section 4.5.9.1 Biological removal
Vegetative cover (evapo-transpiration cover) Soil, sediment and sludge Organic and inorganic compounds Process goal: contaminant containment and erosion control.
Plants: poplars and grasses.
Status: field applications.

N/A Phyto-remediation
Biological wastewater treatment Surface water and groundwater Organic compounds (radionuclides and heavy metals) Biological sewage treatment plants will also destroy certain organic contaminants. Bacterial populations specialized for certain contaminants may be used. The resulting sludge will also contain the majority of radionuclides and heavy metals and can be collected for further treatment.

N/A Biological removal
In-situ chemical oxidation Soil and groundwater Organic compounds (heavy metals and radionuclides) The injection of ozone (O3), hydrogen peroxide (H2O2) or chlorine compounds induces a redox reaction that chemically converts contaminants into less toxic compounds. This may reduce the mobility of contaminants throughout a plume.

Section 4.5.4 Containment
Phyto-degradation Soil, sediment, sludge, groundwater and surface water Organic compounds, sludge, chlorinated solvents, groundwater phenols, herbicides and munitions

Process goal: contaminant destruction.
Plants: algae, stonewort, hybrid poplars, black willow and bald cypress.
Status: field demonstrations.
N/A Phyto-remediation
Reactive barriers Groundwater Organic compounds, heavy metals and radionuclides This is an in situ method of funnelling the natural or enhanced groundwater flow through a physical barrier containing reactive chemicals (oxidation or precipitation), metal catalysts (redox reactions), bacteria (biodegradation) or adsorbents.

Section 4.5.1.9 Containment
Rhizo-degradation Soil, sediment, sludge and groundwater Organic compound degradation (TPH, PAHsa , pesticides, chlorinated solvents and PCBs)

Process goal: contaminant destruction.
Plants: red mulberry, grasses, hybrid poplar, cat’s tail and rice.
Status: field applications.
N/A Phyto-remediation
Biosorption Surface water and groundwater Radionuclides and heavy metals Certain microorganisms take up metal ions in their cell walls or on their surface; the processes involved can be used to concentrate these contaminants. Facilities can be designed as bioreactors or like sewage treatment plants (organic stationary phase).

Section 4.5.5 Containment
Biosorption Surface water and groundwater Radionuclides and heavy metals Certain micro-organisms take up metal ions in their cell walls or on their surface, a process which can be used to concentrate these contaminants. Facilities can be designed as bioreactors or like sewage treatment plants (organic stationary phase).

Section 4.5.9.3 Biological removal
Constructed wetlands Surface water and groundwater Radionuclides and heavy metals Contaminated waters are routed into artificial ‘swamps’, where the metals are taken up by plant tissue. The plants are harvested and incinerated. The resulting ashes are disposed off.

Section 4.5.5.3 Biological removal
Ex-situ filtration Groundwater Radionuclides and heavy metals Contaminated ground or surface water is passed through a filter column to remove contaminated suspended solids. The resulting filter cake requires further treatment and disposal.

N/A Physical removal
In-situ solidification Soil and sludge Radionuclides and heavy metals The aim is to lower the mobility of contaminants by injecting binding materials (cement, organic or inorganic polymers) that react with the contaminant, the water and/or the soil to produce a low solubility solid.

Section 4.5.2 Containment
In-situ vitrification (ISV) Soil and sludge Radionuclides and heavy metals Soil is vitrified in situ to immobilize contaminants by applying electrical resistance or inductive melting.

Sections 4.5.3 to 4.5.3.3 Containment
Physical segregation Soil Radionuclides and heavy metals Often contaminants (including radionuclides) adsorb to fine grain size fractions in the soil. Size fractionation by sieving or flotation may thus result in a much smaller volume of contaminated material to be treated.

Section 4.5.9 Physical removal
Vitrification Soil and sludge Radionuclides and heavy metals The contaminated material is mixed with glass forming constituents and fluxes to produce solid glass blocks or slag-like products.

N/A Containment
Ex-situ chemical treatment Groundwater Radionuclides and heavy metals (organic compounds) Ion exchange, precipitation, reverse osmosis, etc. are applied to concentrate contaminants for further conditioning.

Section 4.5.9 Chemical removal
Ex-situ solidification Soil or sludge Radionuclides and heavy metals (organic compounds) A low solubility solid is produced from contaminated soil by mixing it with a reactive binder (cement, gypsum, organic or inorganic polymer). The solid material may be disposed off in-situ or at a designated repository.

Section 4.3.3.4 Containment
Membrane separation Groundwater Volatile organic compounds A vapour-air separation method is used that involves the diffusion of volatile organic compounds through a non-porous gas separation membrane.

Section 4.5.9 Physical removal
Soil vapour extraction (SVE) Soil Volatile organic compounds Removes volatile organic compounds from the unsaturated zone by creating a zone of low vapour pressure. Soil vapour extraction is most effective in highly permeable soils.

Section 4.5.8.6 Physical removal
Vacuum extraction Groundwater Volatile organic compounds A vacuum created inside a well forces the groundwater to rise, allowing additional groundwater to flow in. Once in the well, the airflow causes some of the trapped volatile contaminants to vaporize, thus enabling the capture of volatile organic compounds through vapour extraction.

Section 4.5.8.6 Physical removal
Air sparging Groundwater and soil Volatile organic compounds and organic compounds A method is used that promotes volatilization of organic compounds by air injection into the saturated zone; also promotes natural aerobic biodegradation.

Section 4.5.7.2 Physical removal
Ex-situ air stripping Groundwater Volatile organic compounds and organic compounds Removes volatiles in pumped surface or groundwater. Stripping towers (e.g., packed columns) have a concurrent flow of gas and liquid. The waste airstream may undergo further treatment by, for example, activated carbon or incineration.

Section 4.5.9 Physical removal
Thermal desorption (ex-situ) Soil and sludge Volatile organic compounds and organic compounds Excavated soils and sludge’s are heated to approximately 425°C (high temperature thermal desorption) or to approximately 200°C (low temperature thermal desorption) in an effort to volatilize organic contaminants. An off-gas treatment system is attached to capture and treat vapour phase contaminants.

Section 4.5.9 Thermal removal
Thermally enhanced soil vapour extraction Soil Volatile organic compounds and organic compounds Contaminated soil is heated by the injection of hot air or steam, or by electrical resistance or microwave heating, thereby volatilizing contaminants. Off-gases are captured for further treatment.

Section 4.5.8.6 Thermal removal
Vapour phase carbon adsorption Off-gases Volatile organic compounds and organic compounds Off-gases collected from ex situ or in situ stripping methods are routed through canisters containing granular activated carbon.

N/A Physical removal
Riparian corridors (non-point source control) Surface water and groundwater Water soluble organic and inorganic compounds Process goal: contaminant destruction.
Plants: poplars.
Status: field applications.

N/A Phyto-remediation
Hydraulic control (plume control) Groundwater and surface water Water soluble organic compounds and inorganic compounds Process goal: contaminant degradation or containment.
Plants: hybrid poplars, cottonwood and willow.
Status: field demonstrations.

N/A Phyto-remediation

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Table 4.8 Remediation techniques sorted by radioactive contaminant (column 3)
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In table 4.9 (see below) an overview of the containment (CT) and source removal technologies (SRT) are discussed in the following sections.

Containment technologies

  • Subsurface barriers
  • Bored piles
  • Slurry walls or trenches
  • Keyed rammed piles
  • Sheet piles
  • Injection walls
  • Injection curtains
  • Ground freezing
  • Permeable reactive barriers
  • Immobilisation/solidification
    • Chemical immobilization
    • Bio-chemical or biological immobilisation
    • Thermal immobilisation
  • In-situ vitrification
  • Traditional in-situ vitrification
  • Planar in-situ vitrification
  • Plasma arc in-situ vitrification
  • In-situ chemical oxidation
  • Biological barrier walls (bio-walls)
  • Phyto-stabilisation
  • Constructed wetlands
    • Free water surface systems, or soil substrate systems
    • Subsurface flow systems
    • Aquatic plant systems

Removal of the source term

  • Pump and treat for surface water and groundwater
  • Enhanced recovery
  • Enhanced recovery chemical agent methods
    • Displacement by inert electrolytes
    • Co-solvent solubilization
    • Surfactants and micro-emulsions
      • Micellar solubilization
      • Mobilization
  • Enhanced recovery physical methods
    • Hydraulic and pneumatic fracturing
    • Air sparging and venting
    • In-well aeration
  • In-situ treatment for contaminant destruction and removal
  • In-situ biological remediation
  • Phyto-remediation
  • Phyto-extraction treatment
    • Overview
    • Uranium removal
    • Strontium removal
    • Caesium removal
    • Phyto-extraction project in Belarus
  • Rhizo-filtration treatment
  • Non-biological in-situ treatment
    • Dynamic Underground Stripping and Hydrous Pyrolysis Oxidation
    • Soil Vapour Extraction
    • Thermal Methods
      • Electrical resistance heating
      • Microwave heating
      • Thermal Conductance
  • Ex-situ treatment
    • Physical ex-situ techniques
      • Physical segregation
      • Segmented Gate Systems
      • Soil Washing
    • Chemical ex-situ techniques
      • Chemical/solvent extraction
      • Heap leaching
      • Enhanced soil washing
      • Chemical precipitation
      • Ion exchange
      • Adsorption
      • Aeration
      • Ozonation and peroxide application
    • Biological ex-situ techniques
      • Land-farming and bio-piles
      • Bio-reactors
      • Bio-leaching
      • Bio-sorption
    • Thermal ex-situ techniques
      • Distillation
      • Incineration
      • Pyrolysis
      • Thermal desorption
      • Fluid bed steam reforming

Table 4.9 Overview of the technologies discussed in this document