Exploring the Influence of Bioremediation on Dissolution in DNAPL Source Zones
Abstract
Microbial reductive dechlorination has emerged as a promising technology for remediation of chlorinated solvent contaminated source zones. Bioremediation of dense nonaqeuous phase liquid (DNAPL) source zones can be undertaken as a sole treatment technology or as a "polishing" step following the application of a more aggressive treatment method, such as surfactant flushing. A quantitative assessment of the potential effectiveness of in situ source zone bioremediation requires an understanding of the influence of aggressive treatment on subsequent DNAPL bioavailability, as well as the potential bio-enhancement of DNAPL dissolution under natural gradient conditions. This presentation provides an overview of laboratory and modeling investigations designed to explore bioavailability and the influence of bioactivity on DNAPL dissolution in contaminated sandy media. A novel mathematical model was developed to simulate the interplay between DNAPL architecture, DNAPL dissolution, constituent transport, reductive dechlorination kinetics, and concentration inhibition. Model formulation and parameterization were based on results of batch experiments conducted with selected tetrachloroethene (PCE) -to- cis-1,2-dichloroethene (cis-DCE) dechlorinating isolates. Experiments to explore microbial activity and dissolution enhancement in the vicinity of PCE-NAPL in one dimensional sand columns containing a pure or mixed NAPL (0.25 mol/mol PCE in hexadecane) source zone were used to assess model performance. Experimental results demonstrated PCE to cis-DCE dechlorination in the vicinity of the NAPL, with a four-fold dissolution enhancement. These observations are consistent with numerical model predictions. A model sensitivity analysis reveals that dechlorination kinetics, substrate concentrations, and DNAPL saturation and distribution can each affect the extent of dissolution enhancement. The potential influence of bioactivity on source zone longevity and toxicity is also addressed through example model simulations.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.H33I..01A
- Keywords:
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- 0409 Bioavailability: chemical speciation and complexation;
- 0418 Bioremediation;
- 1831 Groundwater quality;
- 1832 Groundwater transport