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EPA/540/AR-93/508
The volume reduction unit
(VRU) is a pilot-scale, mobile soil washing system designed to
remove organic contaminants from the soil through particle size
separation and solubilization. The VRU removes contaminants by
suspending them in a wash solution and by reducing the volume
of contaminated material through particle size separation. Most
contaminants tend to bind to the fine-sized clay and silt particles;
soil washing separates these clay and silt particles from the
coarser sand and gravel particles. The VRU was designed to be
extremely flexible in terms of equipment and wash water additives;
however, it was not designed to be a commercial treatment unit.
The VRU was demonstrated at the Escambia Superfund site in Pensacola
in 1992. The site, used to treat wood products, was contaminated
with polynuclear aromatic hydrocarbons and pentachlorophenol.
The VRU successfully separated the contaminated soil into two
streams: washed soil and fines slurry. The washed soil was returned
to the site while the fines slurry, which carried the majority
of pollutants from the feed soil, underwent additional treatment
to separate the fines from the water. The demonstration also showed
positive impacts of surfactant, pH adjustment, and increased temperature.
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