Remediation techniques

What is thermal desorption?

Thermal desorption is an innovative treatment technology that treats soils contaminated with hazardous wastes by heating them to high temperatures so that contaminants with low boiling points will vaporise (turn into gas) and consequently separate from the soil. (The other soil contaminants, if any, are treated by other methods.) The vaporised contaminants are collected and treated, typically by an air emissions treatment system.

Thermal desorption is a different treatment process than incineration. Thermal desorption uses heat to physically separate the contaminants from the soil. The contaminants then require further treatment. Incineration uses heat to destroy the contaminants.

Why consider thermal desorption?

Thermal desorption is effective at separating organics from refining wastes, coal tar wastes, waste from wood treatment and paint wastes. It can separate solvents, pesticides, PCBs, dioxins and fuel oils from contaminated soil. Finally, the lower temperatures require less fuel than other treatment methods.

Will it work at every site?

Thermal desorption is not applicable to most metals, although mercury can be removed by the process. Other metals will either remain in the treated soil, in which case the soil must be retreated, or vaporise. The presence of metals and their fate must be determined before the soil is processed. Thermal desorption is not equally efficient at treating all types of soil. If the soil is wet, water will vaporise along with the contaminants. Because of the additional substance (water) being vaporised, more fuel is required to vaporise all of the contaminants in the wet soil. Thermal desorption is not a good choice for treating contaminants such as heavy metals (since they do not separate easily from the soil) and strong acids (since they can corrode the treatment equipment).