Thermal Treatments of Contaminated Soils

Thermal treatment technologies play an essential role in the treatment of contaminated soils because they can meet remediation demands rapidly and effectively. However, their high energy demand and their potential harmful effects on soil qualities raise concerns about the sustainability of these technologies. The aim of this thesis is to examine common thermal treatment methods for contaminated soils , assess their possible adverse impacts on the environment, and identify strategies for their low-impact and sustainable implementation based on a comprehensive analysis of energy efficiency and land reuse. The operational principles, benefits, and limitations of every thermal treatment technology, as well as their possible combinations are discussed. A wide range of contaminants, including VOCs. CVOCs, SVOCs, PAHs, PCBs, Dioxins, miscible VOCs (e.g., 1,4-Dioxane), TPH, creosote, coal tar, oils, LNAPL, DNAPL, PFAS, radioactive wastes, mercury, cadmium, and hexavalent chromium can be treated with thermal treatments technologies. The thermal treatment technologies addressed in this review are in situ thermal treatment (ISTT) technologies that include thermal conduction heating (TCH) or in situ thermal desorption (ISTD), smoldering, steam enhanced extraction (SEE) and the combined method known as large-diameter auger mixing with steam injection (LDA), hot air injection, in situ vitrification (ISV), electrical resistance heating (ERH), and radio frequency heating (RFH). This thesis examines Ex situ thermal treatment (ESTT) technologies, which comprise Ex Situ Thermal Desorption (ESTD), In-Pile Thermal Desorption (IPTD), Incineration, Pyrolysis, and Microwave Heating (MWH). ISTT technologies proved to be very useful in sites where it is impossible to conduct excavations or where contaminants are found at great depths. These are major advantages of ISTT over ESTT, along with the reduction of the “secondary pollution”, that frequently occurs during the stockpiling and transportation of contaminants. Additionally, ISTT methods minimize human exposure to contaminants during the treatment. The choice and design of suitable thermal treatment technologies for the successful remediation of contaminants must take into consideration the spatial distribution of contaminants and site-specific characteristics, such as water availability, along with the effect of the treatment temperature on soil properties. Based on this review, heating below 250 °C does not have a significant effect on most soil characteristics and can also make nutrients more available and release dissolved organic carbon to help plants and microbes grow. On the other hand, heating above this temperature will likely damage soil fertility.