(374c) Integrated Reductive/Oxidative Treatment of Nitroaromatic Contaminated Groundwater

Many nitroaromatic compounds (NACs) are considered toxic and potential carcinogens. Years of improper wastewater techniques at United States Department of Defense ammunition plants led to NACs groundwater contamination. Specific NACs include 2,4,6-trinitrotoluene, 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene, and nitrobenzene. At some sites the contaminated groundwater poses a threat to domestic drinking water sources. Presently, the chemical and biological processes applied for treating waters contaminated with these compounds generate persistent by-products that are still of environmental concern. Applying more aggressive reaction conditions or multiple treatment technologies in series can degrade these persistent compounds. However, the capital and operating costs of treating these waters increases significantly. A one step technology capable of efficiently and cost effectively degrading water contaminants is necessary to promptly return billions of gallons of this essential resource to farmers, private companies, and the public. The purpose of this study was to develop an integrated reductive/oxidative process for treating NACs contaminated waters. The process consists of the combination of zero-valent manganese or iron and a hydroxyl radical based treatment technique. Corrosion promoters are added to the contaminated water to minimize passivation of the metallic species. Water contaminated with 2,4-DNT was treated with the integrated process using a recirculated batch reactor. It was demonstrated that addition of corrosion promoters to the contaminated water enhances the rate of reaction of 2,4-DNT with zero-valent iron or manganese. Results show that iron provided greater reduction of 2,4-DNT than manganese. Hydroxyl radicals generated combining ozone and hydrogen peroxide oxidized these products. The degree of mineralization was measured analyzing the samples for total organic carbon and nitrates. These results will be presented along with proposed reaction and corrosion mechanisms and developed rate expressions.