Contaminated Soil Treatment Information and Services

Contaminated soil treatment is a phrase applied to many different types of soil treatment technologies. Of these contaminated soil treatment technologies, thermal treatment consists fundamentally of a two-step process, as illustrated below, heat is applied to a contaminated material, such as soil, sediment, sludge, or filter cake, to vaporize the contaminants into a gas stream that, in Step 2, is treated to meet regulatory requirements prior to discharge. A variety of gas treatment technologies are used to collect, condense, or destroy these volatized gases.

Thermal desorption is fundamentally a contaminated soil treatment process that thermally induces physical separation. Contaminants are vaporized from a solid matrix and are transferred into a gas stream where they can be more easily managed in Step 2. Options used to manage or treat the contaminant-laden gas stream may consist of condensation, collection, or combustion. For the first of these two options, the condensed or collected contaminants usually are treated off site at some time subsequent to Step 1. For the third option, combustion, treatment occurs on site, immediately after the gases exit Step 1 of the process.

In addition to volatilizing organic contaminants contained in the waste feed, moisture is volatilized and leaves with the off-gas. As a result, the thermal desorption system also functions as a dryer. In fact, many vendors refer to the primary treatment chamber of their system as a “rotary dryer,” highlighting its effect on the material, although the principal purpose is to evaporate and separate out the contaminants.

In the basic thermal desorption process, application is limited to nonchlorinated contaminants with relatively low boiling points (i.e., below 600°F). The material typically is heated to between 300°F and 600°F, and the process is sometimes referred to as “low-temperature thermal desorption” (LTTD). Thermal desorption was eventually applied to material having boiling points higher than 600°F. As a result, these systems have evolved so they are able to heat materials to temperatures in the range of 600°F to 1,200°F. In this case, the system is sometimes called “high-temperature thermal desorption” (HTTD). In either case, the treated material essentially retains its physical properties, although they may be modified somewhat when heated to higher temperatures. Thermal desorption technologies have not only been modified to treat high-boiling-point contaminants, but are also capable of treating a variety of chlorinated compounds.