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Bioenhancement of NAPL pool dissolution: experimental evaluation
Eric A Seagren1, Bruce E Rittmann, Albert J Valocchi
1Department of Civil and Environmental Engineering, University of Maryland, College Park 20742, USA. eseagren@eng.umd.edu
Journal of Contaminant Hydrology
|May 10, 2002
Summary
Biodegradation can enhance nonaqueous phase liquid (NAPL) pool dissolution, particularly at low contaminant concentrations. However, higher concentrations may lead to toxicity, reducing this bioenhancement effect.
Area of Science:
- Environmental Science
- Bioremediation
- Geochemistry
Background:
- Nonaqueous phase liquids (NAPLs) pose persistent groundwater contamination challenges.
- Understanding NAPL dissolution and biodegradation is crucial for effective remediation strategies.
Purpose of the Study:
- To quantify the dissolution of nonaqueous phase liquid (NAPL) pools.
- To assess the enhancement of NAPL dissolution by in situ biodegradation.
- To investigate the impact of contaminant concentration on bioenhancement.
Main Methods:
- Experiments utilized glass-bead packed column reactors with a toluene-in-dodecane NAPL pool.
- 14C-carbon mass-balance approach was employed to determine toluene dissolution fluxes.
- Water flushing experiments were conducted with and without biodegradation at varying pore water velocities.
Main Results:
- A statistically significant bioenhancement of toluene dissolution flux, up to twofold, was observed at low toluene mole fractions (approximately 0.02).
- Little to no bioenhancement occurred at a higher toluene mole fraction (approximately 0.09).
- Biodegradation effectively reduced effluent toluene concentrations, irrespective of bioenhancement.
Conclusions:
- In situ biodegradation can significantly enhance NAPL pool dissolution, especially at lower contaminant concentrations.
- Higher dissolved toluene concentrations may inhibit biodegradation due to potential toxicity effects.
- Biodegradation remains a valuable tool for reducing contaminant levels in effluents, even when dissolution is not directly enhanced.