Modelling reactive CAH transport using batch experiment degradation kinetics.

Area of Science:

• Environmental microbiology
• Geochemistry
• Biogeochemical processes

Background:

• Predictive models for organic substance transport in porous media rely on biodegradation kinetics.
• Extrapolation of batch biodegradation rates to reactive transport in porous media is seldom validated.
• Assessing cell-specific activity differences between liquid cultures and porous media is crucial for model accuracy.

Purpose of the Study:

• To evaluate the extrapolation of biodegradation kinetics from liquid batch assays to reactive transport in porous media.
• To assess the influence of microbial biomass and transport on predicting trichloroethene (TCE) degradation in columns.
• To identify rate-limiting processes in reactive transport through model prediction failures.

Main Methods:

• Column experiments simulating anaerobic TCE transport and degradation at varying flow rates.
• Modeling TCE transport and degradation using biodegradation kinetics derived from liquid cultures.
• Incorporating Monod kinetics to predict biomass growth and chlorinated aliphatic hydrocarbon (CAH) degradation.

Main Results:

• Column data for TCE transport and degradation were accurately predicted (factor 1.4) when microbial biomass was an input parameter.
• Models incorporating Monod kinetics overestimated CAH degradation without accounting for microbial transport and biomass adjustments.
• Including microbial transport and biomass adjustments allowed models to predict microbial numbers (factor 4.3) and dechlorination (factor 1.2).

Conclusions:

• Batch-to-column extrapolation is validated for this setup, provided microbial biomass in columns is accurately predicted.
• Mass transfer limitations and microbial ecology differences had minor impacts on dechlorination in this specific setup.
• TCE degradation in reactive transport is most sensitive to degradation kinetics and residence time, followed by microbial growth.