An integrated evaluation of bioenhanced in situ LNAPL dissolution

Area of Science:

• Environmental Science
• Geochemistry
• Microbiology

Background:

• Field evaluation of in situ bioremediation is hindered by heterogeneity, sampling costs, and measurement limitations.
• Assessing light nonaqueous-phase liquid (LNAPL) bioremediation effectiveness requires robust evaluation strategies.
• Understanding microbial activity and contaminant degradation is crucial for effective in situ bioremediation.

Purpose of the Study:

• To develop and demonstrate a rational strategy for evaluating in situ bioremediation of LNAPL.
• To quantify bioenhanced LNAPL dissolution using integrated analytical methods.
• To simulate and assess intrinsic in situ bioremediation in controlled intermediate-scale flow-cell (ISFC) experiments.

Main Methods:

• Utilized intermediate-scale flow-cell (ISFC) experiments simulating LNAPL (naphthalene in dodecane) contaminated aquifers.
• Integrated multiple analyses: contaminant loss, electron acceptor consumption, alkalinity, pH, dissolved inorganic carbon, stable isotopes, microbial counts, and metabolite analysis.
• Employed mass-flux modeling and mass-balance analyses to interpret data and assess bioremediation performance.

Main Results:

• Demonstrated a significant acceleration of in situ naphthalene biodegradation in the bioremediation scenario compared to the control.
• Quantified bioenhanced LNAPL dissolution by a factor of approximately 2 due to intrinsic bioremediation.
• Showcased the effectiveness of the integrated strategy in providing consistent evidence of bioenhancement.

Conclusions:

• The developed integrated strategy effectively evaluates in situ bioremediation performance and quantifies bioenhancement.
• Intrinsic bioremediation significantly accelerates LNAPL dissolution, particularly at the pool/water interface.
• This approach offers a reliable method for assessing the success of bioremediation strategies in contaminated aquifers.