In Situ Steam Extraction Treatment 1
In situ steam extraction removes volatile and semivolatile hazardous contaminants from soil and ground water without excavation of the hazardous waste. Waste constituents are removed in situ by the technology and are not actually treated. The use of steam enhances the stripping of volatile contaminants from soil and can be used to displace contaminated ground water under some conditions. The resultant condensed liquid contaminants can be recycled or treated prior to disposal. The steam extraction process is applicable to organic wastes but has not been used for removing insoluble inorganics and metals. Steam is injected into the ground to raise the soil temperature and drive off volatile contaminants. Alternatively, steam can be injected to form a displacement front by steam condensation to displace ground water. The contaminated liquid and steam condensate are then collected for further treatment.
In situ steam extraction is a developing technology that has had limited use in the United States. In situ steam extraction is currently being considered as a component of the remedy for only one Superfund site, the San Fernando Valley (Area 1), California site [l] 2 . 3 However, a limited number of commercial-scale in situ steam extraction systems are in operation. Two types of systems are discussed in this chapter: the mobile system and the stationary system. The mobile system consists of a unit that volatilizes contaminants in small areas in a sequential manner by injecting steam and hot air through rotating cutter blades that pass through the contaminated medium. The stationary system uses steam injection as a means to volatilize and displace contaminants from the undisturbed subsurface. Each system has specific applications; however, the lowest cost alternative will be determined by site-specific considerations. This chapter provides information on the technology applicability, limitations, a description of the technology, types of residuals produced, site requirements, the latest performance data, the status of the technology, and sources for further information.