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PAH degradation and redox control in an electrode enhanced sediment cap

Authors

  • Fei Yan,

    1. Department of Civil, Architectural, Environmental Engineering, The University of Texas at Austin, 1 University Station C1786, Austin, TX 78712-0273 USA
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  • Danny D. Reible

    Corresponding author
    1. Department of Civil, Architectural, Environmental Engineering, The University of Texas at Austin, 1 University Station C1786, Austin, TX 78712-0273 USA
    • Department of Civil, Architectural, Environmental Engineering, The University of Texas at Austin, 1 University Station C1786, Austin, TX 78712-0273, USA.
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Abstract

Capping is typically used to control contaminant release from the underlying sediments. However, the presence of conventional sediment caps will often eliminate or slow natural degradation that might otherwise occur at the surface sediment. The objective of this study was to explore the potential of a novel reactive capping, an electrode enhanced cap for the remediation of PAH contaminated sediment. The study on electrode enhanced biodegradation of PAH in slurries showed that naphthalene concentration decreased from ∼1000 to ∼50 µg L−1, and phenanthrene decreased from ∼150 to ∼30 µg L−1 in the ElectroBioReactor within 4 days, and the copy numbers of PAH degrading genes increased by almost two orders of magnitude. In a cap microcosm, two carbon electrodes were placed within a sediment cap with an applied potential of 2 V. The anode was placed at the sediment–cap interface encouraging oxidizing conditions. Oxidation and reduction potential (ORP) profiles showed redox potential approximately 60–100 mV higher at the sediment–cap interface with the application of voltage than in controls. Vertical profiles of phenanthrene porewater concentration were obtained by PDMS-coated fiber, and results showed that phenanthrene at depth 0–0.5 cm below the anode was degraded to ∼70% of the initial concentration within 10 weeks. PAH degrading genes showed an increase of approximately one order of magnitude at the same depth. The no power controls showed no degradation of PAH. These findings suggest that electrode enhanced capping can be used to control redox potential, provide microbial electron acceptors, and stimulate PAH degradation. Copyright © 2012 Society of Chemical Industry

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