Diffusion and reaction within porous packing media: a phenomenological model
W L Jones1, J D Dockery, C R Vogel
1Department of Civil and Agricultural Engineering, Montana State University, Bozeman, MT, USA.
Biotechnology and Bioengineering
|April 25, 1993
Summary
A model describes Pseudomonas aeruginosa growth in diatomaceous earth pellets. Substrate conversion is limited by internal mass transfer, with only the outer 5% of pellets actively converting nutrients.
Area of Science:
- Biotechnology
- Environmental Engineering
- Microbial Ecology
Background:
- Understanding microbial behavior in porous media is crucial for bioreactor design.
- Pseudomonas aeruginosa colonization of diatomaceous earth (DE) pellets presents complex mass transfer challenges.
Purpose of the Study:
- To develop and validate a phenomenological model for biomass distribution and substrate depletion in DE pellets colonized by Pseudomonas aeruginosa.
- To identify rate-limiting steps in substrate conversion within the pellets.
Main Methods:
- Developed a mathematical model incorporating diffusion, biomass attachment/detachment, and mass transfer.
- Used a bench-scale reactor with DE pellets and P. aeruginosa, feeding glucose as the limiting nutrient.
- Measured effluent glucose concentrations and in-situ biomass distribution.
Main Results:
- The model accurately predicted biomass distribution by fitting attachment and detachment parameters.
- Internal mass transfer resistance was identified as the rate-limiting step for substrate conversion.
- External mass transfer and microbial kinetics were found to be negligible; only the outer 5% of pellets contributed to conversion.
Conclusions:
- Phenomenological modeling provides insights into microbial processes within porous materials.
- Substrate conversion in DE pellets is primarily governed by internal mass transfer limitations.
- Optimized bioreactor design should consider the limited active biomass volume within pellets.
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