Remediation: Techniques and Cost - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 385

Water reused

Water and
detergent

Wash
water

Treatment
plant

Clean water

Scrubbing unit

Polluted
soil (sifted)

Polluted soil
to second cleanup
method or landfill

Clean soil

FIGURE 11.8
Example of soil washing. (From United States Environmental Protection Agency (USEPA), A Citizen's Guide to
Soil Washing , EPA 542-F-01-008, Office of Solid Waste and Emergency Response, Washington, DC, 2001c.)

Steam injection
Gases and polluted water
removed and cleaned up

Steam Steam

Collection well

Ground surface

Polluted
soil and
groundwater

Steam Steam Steam Steam

Groundwater level

FIGURE 11.9
Example of in situ thermal treatment. (From United States Environmental Protection Agency (USEPA), A
Citizen's Guide to In Situ Thermal Treatment , EPA 542-F-01-0012, Office of Solid Waste and Emergency Response,
Washington, DC, 2001d.)

An added benefit of thermal technologies occurs when the heat destroys certain contami-
nants. In most cases, the added heat energy acts to evaporate the contaminants, and makes
collecting the contaminants using SVE much more efficient (Figure 11.9).

11.3.11 Ex Situ Thermal Treatment

Ex situ thermal treatment is similar to in situ thermal treatment with the key distinctions
being the contaminated soil is excavated and treated thermally at the surface. After treat-
ment, the soil is either returned into the ground or transported to a landfill.