Modeling aerobic biodegradation in the capillary fringe

Area of Science:

• Environmental Science
• Environmental Microbiology
• Geochemistry

Background:

• Volatile subsurface contaminants pose risks through vapor intrusion.
• Aerobic biodegradation is a potential natural attenuation strategy.
• Understanding contaminant degradation in the capillary fringe is crucial.

Purpose of the Study:

• To investigate the mitigation of volatile subsurface contaminants via aerobic biodegradation.
• To characterize contaminant degradation kinetics and transport processes.
• To develop a model for predicting biodegradation in the capillary fringe.

Main Methods:

• Laboratory column studies using chlorobenzene and dichlorobenzene mixtures.
• Development of a biodegradation model incorporating oxygen, substrate, and biomass kinetics.
• Derivation of an analytical solution for steady-state conditions.

Main Results:

• Rapid degradation of contaminants in thin reactive zones with high biomass.
• Model accurately characterized biodegradation behavior.
• Increased contaminant mass flux led to thinner, oxygen-boundary-proximal reactive zones.

Conclusions:

• Aerobic biodegradation in the capillary fringe is effective for preventing contaminant migration.
• The model supports the simplification of reaction kinetics and reactive zone approximation.
• Microbial communities can achieve near-instantaneous degradation of contaminants.