Thermal desorption

Thermal desorption is an environmental remediation technology that utilizes heat to increase the volatility of contaminants such that they can be removed (separated) from the solid matrix (typically soil, sludge or filter cake). Thermal desorption is not incineration. The volatilized contaminants are then either collected or thermally destroyed. A thermal desorption system therefore has two major components; the desorber itself and the offgas treatment system.

Thermal desorption first appeared as an environmental treatment technology in 1985 when it was specified in the Record of Decision (ROD) for the The McKin Company Superfund site within the Royal River watershed in Maine.

It is frequently referred to as "low temp" thermal desorption to differentiate it from high temperature incineration. An early direct fired thermal desorption project was the treatment of 8000 tons of toxaphene (a chlorinated pesticide) contaminated sandy soil at the S&S Flying Services site in Marianna Florida in 1990, with later projects exceeding 170,000 tons at the Cape Fear coal tar site in 1999. A status report from the United States Environmental Protection Agency (USEPA) shows that thermal desorption has been used at 69 Superfund sites through FY2000. In addition, hundreds of remediation projects have been completed using thermal desorption at non-Superfund sites.

For in-situ on-site treatment options, only incineration and stabilization have been used at more Superfund sites. Incineration suffers from poor public acceptance. Stabilization does not provide a permanent remedy, since the contaminants are still on site. Thermal desorption is a widely accepted technology that provides a permanent solution at an economically competitive cost.

The world’s first large-scale thermal desorption for treatment of mercury containing wastes was erected in Wölsau, for the remediation of the Chemical Factory Marktredwitz aka CFM (founded in 1788) was considered to be the oldest in Germany. Operation commenced in October 1993 including the first optimising phase. 50,000 tons of mercury-contaminated solid wastes were treated successfully between August 1993 and June 1996. 25 metric tons of mercury had been recovered from soil and rubble. Unfortunately the Marktredwitz plant is often misunderstood in the literature as a pilot-scale plant only.

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