Soil Washing Processes and How They Work (Or Don't Work)

David W. Bieber, John Y. Mason, Robert H. Wohleb

Soil washing is a young technology for the remediation of contaminated soils. Typical washing schemes have relied on three basic processes to accomplish their remediation goals. These three processes are contaminant concentration, contaminant destruction through chemical oxidation, and surfactant activated bio-enhanced contaminant destruction.

Soil washing processes that focus on concentration, isolate the soil fraction containing the majority of the contaminants (i.e. clays). They are most practical for the remediation of non-organic-contaminants. Soil Washing using chemical oxidation relies on the destruction of contamination by strong oxidizing agents such as hydrogen peroxide. Surfactant activated bio-enhanced destruction operates on the principle of solubilizing contamination to increase its surface area, which dramatically increases bioremediation rates. The chemical oxidation process has traditionally been used to remediate organic contaminants Chemical oxidation is loosing favor as surfactant activated bio-enhanced destruction becomes more common.

Like all emerging technologies, soil washing has had its share of growing-pains. Initial soil washing efforts suffered from high costs and inefficient equipment. As the actual chemical, biological, and mechanical processes involved in soil washing were understood, the initial problems were overcome. Current generation, transportable soil washing systems are capable of washing over 500 metric tons of soil per day. The primary limiting factor on the quantity of soil that can be processed in a day is the percent of material less than 100 microns present in the soil. When properly applied, soil washing is a quick and cost effective method for remediating contaminated soil.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995