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Particle visualisation--a tool for determination of rise velocities
M Ljunggren1, L Jönsson, J la Cour Jansen
1Department of Water and Environmental Engineering, Lund Institute of Technology, 221 00 Lund, Sweden. Michael.Ljunggren@vateknik.lth.se
Summary
Dissolved Air Flotation (DAF) effectively removes larger particles by utilizing particle/bubble aggregates. Larger aggregates with multiple bubbles rise faster, enhancing separation efficiency for bigger particles in wastewater treatment.
Area of Science:
- Environmental Engineering
- Water Treatment Technologies
- Particle Science
Background:
- Kaldnes Moving Bed (KMB) process is used in wastewater treatment.
- Dissolved Air Flotation (DAF) is a key separation technology.
- Understanding particle behavior in DAF is crucial for optimizing removal efficiency.
Purpose of the Study:
- To investigate the separation mechanism of particles during Dissolved Air Flotation (DAF).
- To analyze the characteristics and rise rates of particle/bubble aggregates.
- To correlate particle size with DAF removal efficiency.
Main Methods:
- Utilized an optical borescope for visualization of particle/bubble aggregates.
- Estimated rise rates of aggregates formed post-Kaldnes Moving Bed process.
- Conducted particle size analysis to determine removal efficiency across different size categories.
Main Results:
- Observed significant variability in the rise rates of particle/bubble aggregates.
- Distinguished two aggregate groups: small flocs (<100 µm) with slow rise rates and large flocs (>100 µm) with fast rise rates.
- Demonstrated increased DAF separation efficiency with increasing particle size.
Conclusions:
- Fast rise rates of large particle/bubble aggregates likely explain effective separation of large particles in DAF.
- Particle size is a critical factor influencing DAF performance.
- The study provides insights into optimizing DAF processes for enhanced particle removal.