Superfund Innovative Technology Evaluation (SITE)
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
Bergmann USA Soil Sediment
Bergmann developed a soil washing technology that separates contaminated particles by grain size and density, concentrating contamination in the fine particle fraction (less than 45 microns, µm). Contaminated soil is screened to remove coarse rock and debris. Water is added to the remaining soil to form a slurry. Surfactants, acids, bases, and chelators may be added to improve contaminant solubility. The slurry is fed into an attrition scrubber followed by other mechanical equipment designed to remove silts and clays from granular particles. Settling tanks and cyclones improve particle separation. Four output streams result: coarse clean fraction (>45 µm), enriched fine fraction, contaminated humic materials (leaves, twigs, roots, etc.), and process wash water. The coarse clean fraction can be backfilled or incorporated into concrete or asphalt. The fine and humic fractions are typically de-watered before treatment or, as appropriate, disposal. The wash water is treated, to remove metals and organics, and recycled to the plant for reuse. A barge-mounted pilot-scale system of the technology was demonstrated over five days in April 1992 in the Saginaw Bay of Lake Huron just offshore of Essexville, Michigan. PCB and metal contaminants were effectively concentrated in the fine-particle fraction.