Summary and Conclusions
The waste immobilization techniques are those proposed to prevent
the free movement of contaminants in waste. Three major
groups of immobilization techniques are described in detailed.
They are the temporary containment techniques, cost effective
solidification/stabilization techniques, and the permanent vitrifi-
cation techniques. Several basic techniques such as pumping, capping,
draining, and employment of slurry barrier walls are discussed.
The selection of a containment system is based on the
type of waste materials, geohydrological, and geoenvironmental
conditions of waste site. The containment techniques are usually
used to ‘‘buy time’’ under emergency or temporary conditions.
Stabilization refers to a chemical technique used to render a waste
less toxic or less harmful to the surrounding environment. Solidi-
fication is used to transform the waste ~as is! into a durable and
suitable physical form that is more compatible for storage, land-
fill, or reuse. Solidification/stabilization techniques can be either
chemical or nonchemical. Chemical methods are very popular and
cost effective. Contaminated soils can be effectively solidified
and stabilized using chemical methods, but the resulting products
may not always be reused as construction materials or consumable
materials. Vitrification is an innovative technology that incorporates
the hazardous contaminated waste into a chemical durable
glass-like product. Waste glass is so stable that the
Environmental Protection Agency has declared vitrification to be
the ‘‘best demonstrated available technology’’ for heavy metals
and high-level radioactive waste. However, it is the most expensive
immobilization technique. The unit cost of treatment can be
between $60–200. There is a large volume reduction with vitrifi-
cation. During vitrification of waste, metal oxides are reduced to
metals. The liquefied metals are separated and recycled. Vitrification
can be either in-situ or ex-situ. Vitrification technology is
continuously perfected to permanently dispose-of highly radioactive
waste.