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Batch tests to determine activity distribution and kinetic parameters for acetate utilization in expanded-bed
1Department of Civil Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, and Department of Civil Engineering, University of Cincinnati, Cincinnati, Ohio 45221.
Applied and Environmental Microbiology
|April 1, 1990
Summary
This study analyzed acetate utilization in reactors, finding activity evenly distributed in granular activated carbon (GAC) but concentrated in sludge blankets in sand reactors. This informs microbial activity modeling in wastewater treatment.
Area of Science:
- Environmental Microbiology
- Biochemical Engineering
- Wastewater Treatment Technologies
Background:
- Understanding microbial activity distribution is crucial for optimizing bioreactor performance in wastewater treatment.
- Aceticlastic methanogens, like Methanothrix sp., play a key role in anaerobic digestion.
- Expanded-bed reactors, using sand or granular activated carbon (GAC), are employed for efficient wastewater treatment.
Purpose of the Study:
- To determine the distribution of acetate-utilizing methanogens in expanded-bed sand and GAC reactors.
- To investigate the kinetics of acetate utilization and the influence of 3-ethylphenol on Monod parameters.
- To develop and validate a kinetic model for acetate utilization in these reactors.
Main Methods:
- Batch tests were conducted to measure maximum acetate utilization rates.
- Tests were performed on both whole reactor contents and removed media (sand/GAC).
- Steady-state data combined with batch test results were used to determine kinetic parameters, including the Monod half-velocity constant (K(s)) and inhibition constant (K(i)).
Main Results:
- Acetate-utilizing activity was evenly distributed throughout the GAC reactors.
- In sand reactors, approximately 50% of the activity was localized in a sludge blanket atop the sand bed.
- The Monod half-velocity constant (K(s)) was dependent on effluent 3-ethylphenol concentration, necessitating a competitive inhibition term in the model. A K(s) of 8.99 mg/L and K(i) of 2.41 mg/L were determined.
Conclusions:
- The distribution of microbial activity differs significantly between sand and GAC expanded-bed reactors.
- A modified Monod model incorporating competitive inhibition accurately predicts acetate utilization kinetics in the presence of 3-ethylphenol.
- Combining batch activity tests with steady-state data effectively reduces uncertainty in kinetic parameter estimation for bioreactor modeling.