Engineering Technical Support Center (ETSC)
- Biological Technologies
- Physical/Chemical Technologies
Thermal treatments employ heat to vaporize and collect contaminants for safe disposal. Thermal treatments are mostly used in locations high in organic material, rather than to treat mining contamination. Given the complex nature of thermal systems, they are active treatment systems.
Table of Contents
- Thermal Desorption (TD)
- Electrical Resistance Heating
- Steam Injection
- Conductive Heating
- Radio-Frequency Heating
Thermal desorption uses heat to transform chemicals into gases for collection, after they go through a process that removes a targeted substance according to the principles of adsorption-desorption. TD is most useful to clean soils polluted by coal tar, solvents, and wood-preserving chemicals and can be a fast, effective method of cleaning heavily polluted soils. For more information about TD, see A Citizen's Guide to Thermal Desorption (PDF) (2 pp, 65K, EPA/542/F-01/003).
Electrical resistance heating passes an electrical current through moist soil to heat the area and vaporize contaminants for collection and treatment. The soil's resistance produces the polluted heat and steam, and an SVE system most often captures the removed contaminants.
This process involves the introduction of steam into the ground for the purpose of increasing the vapor pressure of the volatile contaminants in the soil. These contaminants then become part of the air/water vapor that rises to the soil's surface. The vapors are then collected, condensed through cooling, and treated. Variables such as soil permeability and chemical volatility may limit steam injection's ability to remove contaminants.
Conductive heating uses heating blankets or heating wells (i.e. steel pipes) to vaporize water; the vaporized water carries contaminants to the surface for collection and subsequent treatment.
Electrodes placed in the soil create a high-frequency, alternating electric field that heats the area, and a vapor extraction system (using SVE wells) collects the harmful substances for treatment. A grounded, metal buffer over and around the area prevents local radio interference and assures safe operation for neighboring communities.
You will need the free Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more, and for a link to the free Acrobat Reader.