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IN-SITU OXIDATION OF 1,4-DIOXANE (LABORATORY RESULTS)
Citation:
SADEGHI, V. M., D. J. GRUBER, J. BRACKIN, M. A. SIMON, AND E. YUNKER. IN-SITU OXIDATION OF 1,4-DIOXANE (LABORATORY RESULTS). Presented at Fifth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, CA, May 22 - 25, 2006.
Description:
Interest in the solvent stabilizer, 1,4-dioxane, is increasing because analytical detection limits have decreased indicating its presence at chlorinated volatile organic compound contaminated sites. The most common method for removing 1,4-dioxane from contaminated water is advanced oxidation, such as mixing ozone and hydrogen peroxide, which produce the hydroxyl radical. Ozone, alone, has been reported to have destruction rates of 1,4-dioxane that are orders of magnitude slower than the hydroxyl radical. Whereas, advanced oxidation processes are commonly used for ex situ treatment of wastewater contaminated with 1,4-dioxane, in situ application of the process for remediation of this chemical in groundwater is innovative.
Laboratory testing in support of the application of in situ oxidation at the Copper Drum Superfund site in South Gate, Los Angeles County, California, demonstrated that ozone alone was as effective as a mixture of ozone and hyrogen peroxide at destroying 1,4-dioxane present in site groundwater. Sparging site groundwater with 26 mg/L ozone (in air) for 3 hours at a flowrate of 200 mL/minute reduced the aqueous concentration of 1,4-dioxane from 680 ìg/L to < 3ìg/L. the same results were achieved with sparging ozone combined with hydrogen peroxide.
In fact, sparging ozone (32 mg/L ozone in air at 200-250 mL/min for three hours) through deionized water spiked with 1,4-dioxane resulted in a 75% destruction of 1,4-dioxane. Sparging ozone under the same conditions through mixtures of deionized water, dioxane, and one additive produced the complete destruction of 1,4-dixoane. The additives tested were constituents of the site groundwater and included ferrous iron (2 mg/L), chelated iron (2 mg/L iron) and alkalinity (1000 mg/L as CaCO3). This implies that although ozone, alone, can partially destroy 1,4-dioxane, several compounds naturally present in this site's groundwater can enhance the effectiveness of ozone in the same manner as hydrogen peroxide. Based on the results of the bench-scale laboratory testing, ozone was chosen for pilot testing at the site.