*2.2.1 Ex situ thermal processes*

Ex situ thermal treatments convert pollutants from the soil to a gas phase. The pollutants are released by vaporisation and then burned at high temperatures. Ex situ thermal remediation depends on three factors: type and amounts of chemicals present, size and depth of the polluted area, and type of soil and conditions present [18]. In order to start the treatment process, the soil condition is required to be broken into small grains and sieved in preparation for thermal treatment. A low temperature range of 350–550°C is selected to heat the contaminated soil. Burning of the gases takes place at the top of the surface, but the VOC or SVOC are not destroyed. The gases at approximately 1200°C can be then combusted in an after-burner chamber; however, dioxins are destroyed [18, 19]. Moreover, ex situ thermal remediation processes are ideal for removing hydrocarbon compounds.

#### *2.2.2 In situ thermal processes*

The process involves injecting a steam-air mixture at 60–100°C into the contaminated soil to avoid the shifting of pollutants to the groundwater; the steam-air mixture should stay in that temperature range. After the injection, VOC and SVOC get converted from the soil to the gas phase. The gases are then removed from the subsurface using a soil vapour extraction (SVE) system and then remediated at the surface. Furthermore, in situ thermal remediation is used for homogeneous soils with high permeability and low organic content. In situ thermal processes are only appropriate for destroying pollutants, which can be stripped in the lower temperature range (e.g. BTEX) [10–18].

#### **2.3 Physical and chemical remediation**

Physical remediation method aims to rehabilitate and remediate contaminants by separating contaminants from soil. This method is focused on the physical differences between the contaminants and soil (e.g. volatility, behaviour in electric field) or among their physical properties (e.g. particle size, density, etc.) and soil properties [10–18]. There are several physical and chemical remediation techniques available for soil remediation which are described in the following section.

#### *2.3.1 Solidification/stabilisation*

Solidification/ Stabilisation (S/S) process is considered as an in-situ fixation or immobilization, which aims to alter the condition of contamination compounds to innocuous, and/or immobilize condition by using stabilizing agents into an area of contaminated soil. This process make the status of the contamination soil to be in lowpermeability mass (solidification), or chemical reactions between the contaminants and stabilising agent which able to decrease their mobility (stabilisation) or physically bound. It is vital to have good knowledge of the hydrological regime, and it can be used to moderate- to high-permeability soils as well as different types of contaminants.

**155**

*2.3.4 Soil washing*

*2.3.5 Geosynthetic applications*

*The Assessment Strategy for Selecting and Evaluating Geoenvironmental Remediation*

Electro-remediation is an in situ remediation system which requires the use of low-intensity direct electrical current across pairs of electrode which is placed into the ground of the contaminated site. This ion migration are depending on their charge therefore, contaminates shifted towards respective electrodes. The remediation process can be supported using surfactant to accelerate the separation of contaminants at the electrodes. This technology is primarily a separation and removal procedure for extracting contaminants from various soils such as saturated or unsaturated soil, sludge, and sediment; additionally, this method is limited for

Soil venting and air sparging or SVE are used in treatment approaches by inject-

ing gas (usually air or oxygen) into the saturated zone to volatile contaminants and stimulating biodegradation by augmenting subsurface oxygen concentrations [10–23]. The remediation system of SVE can be applied successfully for VOCs in relatively moderate- to high-permeability geologic soil. Among others, soil vapour is useful to extract compounds with high vapour pressure for low molecular weight (LMW) compounds. Nevertheless, this method is not suitable for organic compounds with low volatility, for example, polycyclic aromatic hydrocarbons (PAH), and unable to expel super heavy oil pollutants which contain high concentrations of resins and bituminous materials [24]. After airflow is switched off, contamination may transfer from these less accessible spots of contamination to recontaminate the soil atmosphere. Under high pressure of injection, it is easy to fracture the soil material which leads to pathways of air transfer to decrease the side effect of the treatment. In addition sparging must be activated with venting to detain the emissions of VOCs in air leaving the saturated zone. Treated soil, either from SVE in conjunction with air sparging or SVE alone, is usually collected for subsequent treatment, probably catalytic oxidation [25]. SVE has been conducted successfully to treat and rehabilitate soils contaminated with VOC, SVOC, or any chemical contaminants that can be aerobically biodegraded [19]; various factors need to be controlled during the remediation process such as moisture, heat, nutrients,

Soil washing aims to use liquids such as water, occasionally combined with detergent or surfactant with mechanical processes, to separate the contaminants from soils. Frequently, the higher contaminated part of the soil is the fine fractions of soil. Moreover, if the fine fraction content is more than 30–40%, it may not be cost-effective to conduct the separation as a further remediation stage [26].

As geoenvironmental applications are considered as a potential for rehabilitating contaminated soil, geosynthetic materials become vital in the industrial field, particularly geomembranes. The main role of a geomembrane is to reduce the migration of contaminants whether existing as liquid or vapour, either existing as a composite or a single liner barrier system, via base liners and into the surrounding environment [27]. Previous researches deduced that geomembranes could be used as protective layers nearby diesel tanks, in temporary containment barriers, landfill

*DOI: http://dx.doi.org/10.5772/intechopen.88166*

sites where the soil is wet or saturated with water [22].

oxygen, and pH to enhance the bioremediation process.

*2.3.2 Electro-remediation*

*2.3.3 Soil venting and air sparging*

*The Assessment Strategy for Selecting and Evaluating Geoenvironmental Remediation DOI: http://dx.doi.org/10.5772/intechopen.88166*

#### *2.3.2 Electro-remediation*

*Geopolymers and Other Geosynthetics*

*2.2.1 Ex situ thermal processes*

removing hydrocarbon compounds.

*2.2.2 In situ thermal processes*

ture range (e.g. BTEX) [10–18].

*2.3.1 Solidification/stabilisation*

**2.3 Physical and chemical remediation**

which is considered as fast method nevertheless; this method is classified as the most expensive remediation process. It is possible for contaminants such as VOC or SVOC to be vaporised and then rise to the unsaturated zone where they are collected using vacuum system to start another treatment procedure. For geological materials with moderate to high permeability, it is recommended to apply steam. The time it takes depends on three major factors: type and amounts of chemicals present, size and

Ex situ thermal treatments convert pollutants from the soil to a gas phase. The pollutants are released by vaporisation and then burned at high temperatures. Ex situ thermal remediation depends on three factors: type and amounts of chemicals present, size and depth of the polluted area, and type of soil and conditions present [18]. In order to start the treatment process, the soil condition is required to be broken into small grains and sieved in preparation for thermal treatment. A low temperature range of 350–550°C is selected to heat the contaminated soil. Burning of the gases takes place at the top of the surface, but the VOC or SVOC are not destroyed. The gases at approximately 1200°C can be then combusted in an after-burner chamber; however, dioxins are destroyed [18, 19]. Moreover, ex situ thermal remediation processes are ideal for

The process involves injecting a steam-air mixture at 60–100°C into the contaminated soil to avoid the shifting of pollutants to the groundwater; the steam-air mixture should stay in that temperature range. After the injection, VOC and SVOC get converted from the soil to the gas phase. The gases are then removed from the subsurface using a soil vapour extraction (SVE) system and then remediated at the surface. Furthermore, in situ thermal remediation is used for homogeneous soils with high permeability and low organic content. In situ thermal processes are only appropriate for destroying pollutants, which can be stripped in the lower tempera-

Physical remediation method aims to rehabilitate and remediate contaminants

Solidification/ Stabilisation (S/S) process is considered as an in-situ fixation or immobilization, which aims to alter the condition of contamination compounds to innocuous, and/or immobilize condition by using stabilizing agents into an area of contaminated soil. This process make the status of the contamination soil to be in lowpermeability mass (solidification), or chemical reactions between the contaminants and stabilising agent which able to decrease their mobility (stabilisation) or physically bound. It is vital to have good knowledge of the hydrological regime, and it can be used to moderate- to high-permeability soils as well as different types of contaminants.

by separating contaminants from soil. This method is focused on the physical differences between the contaminants and soil (e.g. volatility, behaviour in electric field) or among their physical properties (e.g. particle size, density, etc.) and soil properties [10–18]. There are several physical and chemical remediation techniques

available for soil remediation which are described in the following section.

depth of the polluted area, type of soil and situations present [21].

**154**

Electro-remediation is an in situ remediation system which requires the use of low-intensity direct electrical current across pairs of electrode which is placed into the ground of the contaminated site. This ion migration are depending on their charge therefore, contaminates shifted towards respective electrodes. The remediation process can be supported using surfactant to accelerate the separation of contaminants at the electrodes. This technology is primarily a separation and removal procedure for extracting contaminants from various soils such as saturated or unsaturated soil, sludge, and sediment; additionally, this method is limited for sites where the soil is wet or saturated with water [22].

#### *2.3.3 Soil venting and air sparging*

Soil venting and air sparging or SVE are used in treatment approaches by injecting gas (usually air or oxygen) into the saturated zone to volatile contaminants and stimulating biodegradation by augmenting subsurface oxygen concentrations [10–23]. The remediation system of SVE can be applied successfully for VOCs in relatively moderate- to high-permeability geologic soil. Among others, soil vapour is useful to extract compounds with high vapour pressure for low molecular weight (LMW) compounds. Nevertheless, this method is not suitable for organic compounds with low volatility, for example, polycyclic aromatic hydrocarbons (PAH), and unable to expel super heavy oil pollutants which contain high concentrations of resins and bituminous materials [24]. After airflow is switched off, contamination may transfer from these less accessible spots of contamination to recontaminate the soil atmosphere. Under high pressure of injection, it is easy to fracture the soil material which leads to pathways of air transfer to decrease the side effect of the treatment. In addition sparging must be activated with venting to detain the emissions of VOCs in air leaving the saturated zone. Treated soil, either from SVE in conjunction with air sparging or SVE alone, is usually collected for subsequent treatment, probably catalytic oxidation [25]. SVE has been conducted successfully to treat and rehabilitate soils contaminated with VOC, SVOC, or any chemical contaminants that can be aerobically biodegraded [19]; various factors need to be controlled during the remediation process such as moisture, heat, nutrients, oxygen, and pH to enhance the bioremediation process.

### *2.3.4 Soil washing*

Soil washing aims to use liquids such as water, occasionally combined with detergent or surfactant with mechanical processes, to separate the contaminants from soils. Frequently, the higher contaminated part of the soil is the fine fractions of soil. Moreover, if the fine fraction content is more than 30–40%, it may not be cost-effective to conduct the separation as a further remediation stage [26].

#### *2.3.5 Geosynthetic applications*

As geoenvironmental applications are considered as a potential for rehabilitating contaminated soil, geosynthetic materials become vital in the industrial field, particularly geomembranes. The main role of a geomembrane is to reduce the migration of contaminants whether existing as liquid or vapour, either existing as a composite or a single liner barrier system, via base liners and into the surrounding environment [27]. Previous researches deduced that geomembranes could be used as protective layers nearby diesel tanks, in temporary containment barriers, landfill and treatment walls, or in mining applications [28–30]. Geomembranes have been employed and evaluated for the first time in the soil remediation area, as a layer for biopile method in the composite liner barrier system used for treating hydrocarboncontaminated soil [31]. Geomembranes have been used for a variety of applications during remediation of heavily contaminated sand with polychlorinated biphenyls (PCBs), hydrocarbons, and metal [32, 33]. They proposed to construct geomembranes in the landfill site as the base barrier system to filter and treat the contaminants from the spring thaw. This technique is required when contaminated soil or landfill needs to be isolated from the surrounding groundwater or ecological system to prevent the release of hazardous gases or liquids. Furthermore, Various advantage can be obtained by using geomembrane such as protecting people from contacting with hazards or reduce the impact of discharge water through the contaminated land which allow to decrease in leachate of these hazardous to the groundwater.
