Interactions between flocs and bubbles in the separation zone of dissolved air flotation system

Area of Science:

• Environmental Engineering
• Chemical Engineering
• Water Treatment Technologies

Background:

• The dissolved air flotation (DAF) process relies on the interaction between flocs and bubbles for efficient separation.
• Understanding these micro-scale interactions is key to optimizing DAF performance.

Purpose of the Study:

• To investigate the interaction dynamics between flocs and bubbles in the DAF separation zone.
• To determine the influence of floc size on collision, adhesion, coalescence, and desorption (CACD) processes.

Main Methods:

• Establishment of a micro-scale observation system for real-time analysis.
• Application of Stokes' law and Reynolds experiments to predict collision probabilities.
• Computational Fluid Dynamics (CFD) simulations using Fluent software to analyze drag forces.

Main Results:

• Four key interactions (collision, adhesion, coalescence, desorption) were identified.
• Small flocs exhibit higher unit buoyancy and a greater collision probability with bubbles.
• Low-pressure drag on small flocs facilitates high collision rates, enabling rapid buoyancy accumulation.

Conclusions:

• Small flocs are more effective in DAF due to their higher collision probability and lower buoyancy requirements for flotation.
• The limited bubble attachment on small flocs reduces desorption and coalescence, further improving efficiency.
• Optimizing floc size is critical for maximizing separation efficiency in dissolved air flotation processes.