Vitrification

Soil vitrification is used in both in situ and ex situ treatment. The process involves inserting large graphite electrodes into the soil and applying a high current of electricity to the electrodes (U.S. EPA 1992). The electrodes are typically arranged in 30-foot squares and connected by graphite on the soil surface. The heat causes a melt that gradually works downward through the soil incorporating inorganic contaminants into the melt and paralyzing organic components. After the process is complete and the ground has cooled, the fused waste material is dispersed in a chemically inert, stable, glass-like product with low leaching characteristics.

The technology is potentially effective for halogenated and nonhalogenated volatiles and semivolatiles as well as fuel hydrocarbons, pesticides, and inorganics. The process reduces the mobility of the contaminants, and the vitrified mass resists leaching for geological time periods. The tech nology, however, is energy-intensive, and the off-gases must be collected and treated before release.

—Ahmed Hamidi

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