Water Center, The

 

Date of this Version

10-2013

Citation

Published in Environmental Science & Technology, 47: 13031-13038; doi: 10.1021/es403150x

Comments

Copyright © 2013 American Chemical Society. Used by permission.

Abstract

The residual buildup and treatment of dissolved contaminants in low permeable zones (LPZs) is a particularly challenging issue for injection-based remedial treatments. Our objective was to improve the sweeping efficiency of permanganate into LPZs to treat dissolved-phase TCE. This was accomplished by conducting transport experiments that quantified the ability of xanthan-MnO4 solutions to penetrate and cover (i.e., sweep) an LPZ that was surrounded by transmissive sands. By incorporating the non-Newtonian fluid xanthan with MnO4, penetration of MnO4 into the LPZ improved dramatically and sweeping efficiency reached 100% in fewer pore volumes. To quantify how xanthan improved TCE removal, we spiked the LPZ and surrounding sands with 14C-lableled TCE and used a multistep flooding procedure that quantified the mass of 14C-TCE oxidized and bypassed during treatment. Results showed that TCE mass removal was 1.4 times greater in experiments where xanthan was employed. Combining xanthan with MnO4 also reduced the mass of TCE in the LPZ that was potentially available for rebound. By coupling a multiple species reactive transport model with the Brinkman equation for non-Newtonian flow, the simulated amount of 14C-TCE oxidized during transport matched experimental results. These observations support the use of xanthan as a means of enhancing MnO4 delivery into LPZs for the treatment of dissolved-phase TCE.

Includes Supplementary Data.