(Electrokinetic Remediation Process)
The Electrokinetic Remediation (ER) process removes metals and organic contaminants from soil, mud, sludge, and marine dredgings. ER uses electrochemical and electrokinetic processes to desorb and remove metals and polar organics. The technology may be applied in situ or in the batch mode.
The figure below is a flow diagram of the batch reactor. Waste material is placed into the batch reactor, between Ebonex® ceramic electrodes that are divided into a cathode array and an anode array. A direct current is then applied, causing ions and water to move toward the electrodes. Metal ions, ammonium ions, and positively charged organic compounds move toward the cathode. Anions such as chloride, cyanide, fluoride, nitrate, and negatively charged organic compounds move toward the anode. Two primary mechanisms transport contaminants through the soil: electromigration and electroosmosis. In electromigration, charged particles are transported through the substrate. In contrast, electroosmosis is the movement of a liquid containing ions relative to a stationary charged surface. Of the two, electromigration is much faster and it is the principle mechanism for the ER process.
The electrodes are positioned inside permeable casings that are inserted into the waste material. After the annulus of each casing is filled with water, the current is turned on. The water passes from the anode casing into the waste and toward the cathode. This procedure (1) supports electrokinetic movement of the contaminants through the soil; (2) helps maintain soil moisture, thereby sustaining the electric field; and (3) enables various chemicals that enhance contaminant removal to be added as required.
As the water accumulates in the annulus of the cathode casing, it is pumped out for processing. Processing involves removal of contaminants by electrochemical means, producing a concentrated contaminant brine that can be either further processed or disposed of as hazardous waste. The water is then returned to the annulus of the anode casing.
ER is designed to remove heavy metals, anions, and polar organics from soil, mud, sludge, and dredgings. Treatable concentrations range from a few parts per million (ppm) to tens of thousands ppm. The batch technology is most appropriate for sites with contaminated estuarine and river muds and dredgings, sewage processing sludges, and fines remaining after soil washing. The process can be used with virtually any substrate. ER's effectiveness is sharply reduced for wastes with a moisture content of less than 10 percent.
This technology was accepted into the SITE Demonstration Program in 1994. A demonstration of the process will be conducted at the Alameda Naval Air Station in California. The ER process has been used successfully at several European sites (see table below) on soils contaminated with metals.
EPA PROJECT MANAGER:
Jack Hubbard
U.S. EPA
National Risk Management Research
Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7507
Fax: 513-569-7620
TECHNOLOGY DEVELOPER CONTACT:
Steven Schwartzkopf
Lockheed Martin Missiles and Space Co.
Research and Development Divisions
3251 Hanover Street, ORG 93-50/B204
Palo Alto, CA 94304-1191
415-424-3176
Fax: 415-354-5795