Geo-Cleanse International, Inc. has demonstrated, with support from DOE’s Office of Science and Technology, its promising new process for treating soils and ground water contaminated by chlorinated solvents, hydrocarbons, and dense nonaqueous-phase liquids (DNAPLs). The Geo-Cleanse® Process uses Fenton’s chemistry for the oxidation of contaminants in situ. Initial results of the demonstration show that DNAPL concentrations in the ground water decreased from 100 ppm to less than 1 ppm and chloride ions increased, indicating that contaminants were destroyed.

U.S. Department of Energy sites have more than 2,500 plumes of chlorocarbon contamination, and more than 50 records of decision have identified needs to remediate chlorinated solvents in ground water and soils. These residual solvents, primarily DNAPLs, are currently the most significant barrier to successfully completing a majority of large ground-water and soil cleanup efforts. DNAPLs collect in soil, slowly dissolving into surrounding ground water to create large plumes of organic solvent contamination with concentration levels far above regulatory limits. Ground-water pump-and-treat technology can successfully remove dissolved contaminants; but at sites with DNAPLs, cleanup periods of several hundred years are now forecast. The slow dissolution of DNAPLs into surrounding aquifers creates a continually disseminating source for contaminant plumes. Technologies that target DNAPLs will greatly reduce the remediation efforts at many federal, commercial, and international sites.

How it works

The Fenton’s reagent DNAPL treatment process is based on a chemical method developed by H. J. H. Fenton in the 1890s. Fenton oxidized malic acid, using hydrogen peroxide as the oxidant and iron salts as the catalyst. This chemistry has been (and still is) widely used by the wastewater industry for treating organic wastes. The Geo-Cleanse® Process uses specially designed equipment and injectors to diffuse and disperse a powerful solution of oxidizers, catalysts, and other nonhazardous and environmentally safe compounds into the subsurface environment. The patented injectors are specially designed to withstand the elevated temperatures and pressures resulting from the Geo-Cleanse® Process, while achieving maximum dispersion of the reagents through the subsurface.

This in situ oxidation process is capable of complete, nonselective oxidation of organic compounds in soil and ground water. Upon completion of the process, the organic contaminants (chlorinated solvents, hydrocarbons, and/or DNAPLs) are converted to nontoxic end products (carbon dioxide, chloride ion, and water) or reduced to a level below regulatory limits.

Demonstration

Because of the prevalence of DNAPLs throughout the DOE complex, many plumes of organic solvents cannot be remediated effectively until DNAPL destruction or treatment technologies are deployed. The Geo-Cleanse® Process was selected as a FY97 demonstration by OST’s Subsurface Contaminants Focus Area with support from the Characterization, Monitoring, and Sensor Technology Crosscutting Program. In addition, the technology demonstration was conducted under a cooperative research and development agreement between Westinghouse Savannah River Company and Geo-Cleanse International. A site was selected for the demonstration where DNAPL-contaminated sediments were known to be located below the water table at the M-Area of the Savannah River Site in Aiken, South Carolina.

The postdemonstration effects are currently being evaluated by the Savannah River Technology Center, a division of the Westinghouse Savannah River Company. The evaluations will assess the effects of the Geo-Cleanse® Process on aquifer properties, mineralogy, chemistry, and microbial ecology. This evaluation will provide a basis for choosing optimal sites for deploying the Geo-Cleanse® Process for in situ destruction of DNAPLs and for recommending process changes that will allow planners to optimize DNAPL destruction and minimize detrimental effects.

For more information on the Geo-Cleanse® Process, call Matt Dingens, vice president of sales at Geo-Cleanse International, at (908) 686-5959, or visit the company’s Web site at http://www.geocleanse.com.