In-situ Chemical Oxidation of Residual TCE by Permanganate in Epikarst

Authors: Nihat Hakan Akyol, Irfan Yolcubal

Abstract:

In-situ chemical oxidation (ISCO) has been widely used for source zone remediation of Dense Nonaqueous Phase Liquids (DNAPLs) in subsurface environments. DNAPL source zones for karst aquifers are generally located in epikarst where the DNAPL mass is trapped either in karst soil or at the regolith contact with carbonate bedrock. This study aims to investigate the performance of oxidation of residual trichloroethylene found in such environments by potassium permanganate. Batch and flow cell experiments were conducted to determine the kinetics and the mass removal rate of TCE. pH change, Cl production, TCE and MnO4 destruction were monitored routinely during experiments. Nonreactive tracer tests were also conducted prior and after the oxidation process to determine the influence of oxidation on flow conditions. The results show that oxidant consumption rate of the calcareous epikarst soil was significant and the oxidant demand was determined to be 20 g KMnO4/kg soil. Oxidation rate of residual TCE (1.26x10-3 s-1) was faster than the oxidant consumption rate of the soil (2.54 - 2.92x10-4 s-1) at only high oxidant concentrations (> 40 mM KMnO4). Half life of TCE oxidation ranged from 7.9 to 10.7 min. Although highly significant fraction of residual TCE mass in the system was destroyed by permanganate oxidation, TCE concentration in the effluent remained above its MCL. Flow interruption tests indicate that efficiency of ISCO was limited by the rate of TCE dissolution and the rate-limited desorption of TCE. The residence time and the initial concentration of the oxidant in the source zone also controlled the efficiency of ISCO in epikarst.

Keywords: Epikarst, in-situ chemical oxidation, permanganate.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1085621

References:

[1] S.-R. Cline, O. R. West, Siegrist, S. R, W. L. Holden., 1997. Performance of in situ chemical oxidation field demonstration at DOS sites. Proceedings of In Situ Remediation of the Geoenvironment Conference. Minneapolis, MI, USA.
[2] D. D. Gates, R.L Siegrist, S. R. Cline., 1995. "Chemical oxidation of contaminants in clay or sandy soil. J. Environ. Eng. 121, pp. 582-588.
[3] K. C. Huang, G. E. Hoag, P. Chheda, B. A. Woody, G. M. Dobbs., 1999. Kinetic study of oxidation of trichloroethylene by potassium permanganate. Environ. Eng. Sci. 1116, 265-274.
[4] K. C. Huang, G. E. Hoag, P. Chheda, B. A. Woody, G. M. Dobbs., 2000. A pilot scale study of oxidation of trichloroethylene by sodium permanganate. Proceedings of the Second International Conference on Remediation of Chlorinated and Recalcitrant Compounds. Monterey, CA, USA, pp. 145-152.
[5] K. C. Huang, G. E. Hoag, P. Chheda, B. A. Woody, G. M. Dobbs., 2002. Chemical oxidation of trichloroethylene with potassium permanganate in a porous medium. Advances in Environmental Research. 7, 217-229.
[6] X. D. Li, F. W. Schwartz, 2004. DNAPL mass transfer and permeability reduction during in situ chemical oxidation with permanganate. Geophysical Research Letters.,31.
[7] M. Schnar, C. Truax, G. Farquhar, E. Hood, T. Gonulla, B. Stickney., 1998. Laboratory and controlled field experiments using potassium permanganate to remediate trichloroethylene and tetrachloroethylene DNAPLs in porous media. J. Contam. Hydrol. 29, 205-224.
[8] R. L. Siegrist, K. S. Lowe, L. C. Murdoch, T. L. Case, D. A. Pickerging., 1999. In situ oxidation by fracture emplaced reactive solids. J. Environ. Eng. 125, 429-440.
[9] P. G. Tratnyek, T. M. Johnson, S. D. Warner,. H. S. Clarke, J. A. Baker., 1998. In situ treatment of organics by sequential reduction and oxidation. . Proceedings of the Second International Conference on Remediation of Chlorinated and Recalcitrant Compounds. CI-5, pp. 371-376.
[10] C. T. Truax., 1993. Investigation of the in-situ potassium permanganate oxidation of residual DNAPLs located below the groundwater table. M.S. Thesis. University of Waterloo, Ontorio, Canada.
[11] P. A. Vella, B. Veronda., 1992. Oxidation of trichloroethylene: a comparison of potassium permanganate and Fenton-s reagent. Chemical Oxidation: Technology for the Nineties in Proceedings of the Third International Symposium. PA, USA, pp. 75-82.
[12] R. F. Weston., 2000. Summary report for the In situ chemical oxidation remediation pilot study of the bedrock aquifer at the Southeastern (SE) disposal area. Letterkenny Army Depot, Chambersburg, PA.
[13] Y. E. Yan, F. W. Schwartz, 1998. Oxidative degradation of chlorinated ethylenes by potassium permanganate. Environ. Sci. Tcehnol. 34, 2535- 2541.