Treatment units for ISTT include (1) vertical or horizontal heat injection points
(vapor, hot air, or electrodes depending on the variant); (2) vertical or horizontal
extraction points, extraction networks; (3) extraction units; and (4) gas treatment
plants and/or water treatment plants (for treatment in unsaturated zones) (Hiester
et al. 2013; Johnson et al. 2009; Kingston et al. 2014; Unified Facilities Criteria
2006; U.S. Army Corps of Engineers 2014).
The pollution source’s characteristics (size, concentration, boiling temperature,
Henry’s constant, etc.), pollution cleanup thresholds, and the geological context (air
permeability, presence of organic materials, heterogeneity, etc.) are used to determine: (1) the radius of influence for the injection wells and heat production; (2) the
number, spacing, and characteristics of the injection and heat production points
(depth, diameter, trenches, wells, etc.); (3) the radius of influence for the extraction
wells as a function of the pressure drop generated by the extractor; (4) the number,
spacing, and characteristics of the extraction points (depth, diameter, trenches, wells,
etc.); (5) extractor type and power; treatment unit size (Unified Facilities Criteria
2006; U.S. Army Corps of Engineers 2014).
As for the processing of extracted gases, the design of the gas treatment plant
depends on the remediation rate, temperature, flow rates, and pollutant concentrations. It may be composed of washing columns, flares, catalytic oxidation units,
cooling and adsorption units (generally with activated carbon), biofilters, etc. For
high-temperature processes, the common techniques are thermal oxidation, cooling,
and activated carbon (USEPA 2006). The treatment of extracted water most often
includes a recovery system for free NAPL products (skimmer), and if necessary, a
treatment system of the dissolved phase. Depending on the temperature, the chemical structure of pollutants, their concentrations, and the cleanup objectives, these
treatments may include stripping, activated carbon, catalytic oxidation, reduction,
flotation, precipitation, flocculation, decantation, membranes, resins, or evaporation
treatment processes (Colombano et al. 2010).
3.2 Influence of Temperature on the Physical and Chemical
Properties of Organic Pollutants
3.2.1 Effect of Temperature on Solubilization
Dissolution is the mechanism whereby organic compounds are transferred from the
pure phase to the aqueous phase. Water solubility is a measure of the amount of a
chemical substance that can dissolve in water at a specific temperature.
Chlorinated Volatile Organic Compounds (CVOCs) are poorly soluble in water
(Lemière et al. 2008). The effects of temperature on CVOCs solubility must be
known in order to predict how CVOCs will distribute during a thermal remediation
process. Figure 3.2 shows the results reported in field literature regarding the
3 In Situ Thermal Treatments and Enhancements: Theory and Case Study
153
(vapor, hot air, or electrodes depending on the variant); (2) vertical or horizontal
extraction points, extraction networks; (3) extraction units; and (4) gas treatment
plants and/or water treatment plants (for treatment in unsaturated zones) (Hiester
et al. 2013; Johnson et al. 2009; Kingston et al. 2014; Unified Facilities Criteria
2006; U.S. Army Corps of Engineers 2014).
The pollution source’s characteristics (size, concentration, boiling temperature,
Henry’s constant, etc.), pollution cleanup thresholds, and the geological context (air
permeability, presence of organic materials, heterogeneity, etc.) are used to determine: (1) the radius of influence for the injection wells and heat production; (2) the
number, spacing, and characteristics of the injection and heat production points
(depth, diameter, trenches, wells, etc.); (3) the radius of influence for the extraction
wells as a function of the pressure drop generated by the extractor; (4) the number,
spacing, and characteristics of the extraction points (depth, diameter, trenches, wells,
etc.); (5) extractor type and power; treatment unit size (Unified Facilities Criteria
2006; U.S. Army Corps of Engineers 2014).
As for the processing of extracted gases, the design of the gas treatment plant
depends on the remediation rate, temperature, flow rates, and pollutant concentrations. It may be composed of washing columns, flares, catalytic oxidation units,
cooling and adsorption units (generally with activated carbon), biofilters, etc. For
high-temperature processes, the common techniques are thermal oxidation, cooling,
and activated carbon (USEPA 2006). The treatment of extracted water most often
includes a recovery system for free NAPL products (skimmer), and if necessary, a
treatment system of the dissolved phase. Depending on the temperature, the chemical structure of pollutants, their concentrations, and the cleanup objectives, these
treatments may include stripping, activated carbon, catalytic oxidation, reduction,
flotation, precipitation, flocculation, decantation, membranes, resins, or evaporation
treatment processes (Colombano et al. 2010).
3.2 Influence of Temperature on the Physical and Chemical
Properties of Organic Pollutants
3.2.1 Effect of Temperature on Solubilization
Dissolution is the mechanism whereby organic compounds are transferred from the
pure phase to the aqueous phase. Water solubility is a measure of the amount of a
chemical substance that can dissolve in water at a specific temperature.
Chlorinated Volatile Organic Compounds (CVOCs) are poorly soluble in water
(Lemière et al. 2008). The effects of temperature on CVOCs solubility must be
known in order to predict how CVOCs will distribute during a thermal remediation
process. Figure 3.2 shows the results reported in field literature regarding the
3 In Situ Thermal Treatments and Enhancements: Theory and Case Study
153