TECHNOLOGY UPDATE Electrochemical oxidation on organic wastes Scientists are preparing for June field trials of a cerium-mediated means of destroying organic wastes by using catalyzed electrochemical oxidation. Developed at the Pacific Northwest National Laboratory, the technology has been licensed to EOSystems of San Jose, Calif., which hopes to market it as a low-cost alternative to incineration for on-site industrial waste treatment. The process uses an anode composed of cerium with a nitric acidbased electrolyte solution. The solvent is also the reactant, and it oxidizes Ce3+ into Ce4+ at the anode. The metal ion reacts with the organic species or water to form a reactive intermediate, such as the hydroxyl radical. This intermediate, in turn, rapidly oxidizes any organic material. As the material reacts, it becomes less and less volatile. The reactions operate at atmospheric pressure and near room temperature. The cerium is recovered by precipitation with carbonate. The method was first devised in the 1960s to treat radioactive wastes. The process can be conducted with several heavier metals, including silver, cobalt, and iron. The advantages of using cerium include its lack of reactivity with water and its disinclination to form precipitates with chloride. Cerium's low toxicity was established, according to EOSystems, after extensive testing when the element was being considered as a replacement fuel additive for lead. EOSystems has designed an electrochemical cell to drive and contain the reaction. The reactor tank is made of injection-molded plastic. A unit designed to destroy 300 lb of organic waste per day includes 60 pairs of 11 x 20 in. electrodes. The company estimates mat the new technology will cost 2-10 times less than the cost of current methods of disposing of hazardous organic materials. The catalyzed electrochemical oxidation method will be field tested
The catalyzed electrochemical oxidation method, originally created to treat radioactive wastes, is being adapted as an alternative to incineration for on-site industrial wastes. (Courtesy EOSystems, Inc.)
at a university and a power company. EOSystems expects the technology to be useful for treating processed chemical wastes from hospitals, research laboratories, and chemical and pharmaceutical companies. —KELLYN S. BETTS
TPH soil cleanup aided by ground cover Early results of a field demonstration project indicate that phytoremediation may be a promising method for the degradation of petroleum products. After a year's growth in a biotreatment cell, vegetated plots show statistically significant improvements in the dissipation rates of total petroleum hydrocarbons (TPH) compared with unvegetated plots, according to Kansas State University researcher Kathy Banks. Banks is a principal investigator of the demonstration, which is funded by Rice University and the Department of Defense's Advanced Applied Technology Demonstration
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Facility program. The project is being conducted at the Navy's Craney Island Fuel Terminal in Norfolk, Va. The team of researchers, among them KSU professors Paul Schwab and Rao Govindaraju, has 24 plots in a biotreatment cell contaminated with petroleum products, including polycyclic aromatic hydrocarbons (PAHs). They have set up plots with different types of ground cover— white clover, fescue, and Bermuda grass and unvegetated controls. The plots 3X6 statistically designed to ensure replication of the results. Between November 1995 and 1996, the researchers saw more than 35% dissipation of TPH in the vegetated plots and 23% dissipation in the unvegetated controls. "That's encouraging," said Banks. "It indicates that if you have an area that's been properly managed and vegetated with an aggressive plant species, you could enhance the dissipation or degradation of organic contaminants." The levels of PAHs in the test area have not been completely characterized, but there were "very low concentrations in the leachate" from the planted plots Compared with composting and land farming methods also being tested in the biotreatment cell, the KSU methods use very little labor. "We fertilize at rates predetermined to be optimal, and we irrigate during dry periods," Banks said. Phytoremediation was first shown to significantly enhance petroleum dissipation during cleanup of a Gulf Coast oil spill in 1993 that contaminated an agricultural area, said Banks. Over a 21-month period, EPA-funded researchers, including Banks, saw 46% dissipation in places where St. Augustine grass was planted, and 50% dissipation in plots with annual rye grass. The unvegetated areas had 21% dissipation during the same period. However, because the researchers in that project weren't allowed to have replicant plots the results cannot be considered statistically significant. —KELLYN S. BETTS
0013-936X/97/0931-214A$14.00/0 © 1997 American Chemical Society
