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Air flotation devices effectively separate pollutants from water through a series of well - defined mechanisms, with different types of devices employing unique approaches.
Dissolved air flotation (DAF) devices are among the most common. In pressure DAF, air is dissolved in water under high pressure, typically 3 - 5 bar. When the pressurized water is released into the flotation tank at normal pressure, tiny bubbles with diameters of 20 - 100 μm are formed. These microbubbles attach to suspended solids, oil droplets, and other pollutants. Since the combined density of the bubbles and contaminants is less than that of water, they float to the surface, where they can be skimmed off. Vacuum DAF, on the other hand, creates a vacuum environment to release dissolved air, achieving a similar separation effect.
Induced air flotation (IAF) devices, such as cavitation air flotation (CAF) units, use mechanical means. High - speed rotating impellers generate a negative pressure zone, drawing air into the water. The impellers then shear the air into relatively large bubbles, which attach to pollutants. These buoyant bubbles carry the contaminants to the surface, enabling separation.
Shallow - depth air flotation machines use a combination of a shallow - pool design and a rotating water distributor. The rotating distributor injects air into the water, forming bubbles that attach to pollutants. The short retention time in the shallow pool allows for quick separation.
Electrolytic air flotation devices electrolyze water to produce hydrogen and oxygen microbubbles. These bubbles adsorb charged pollutants due to their electrostatic interaction. The bubbles, along with the attached pollutants, rise to the surface, facilitating separation.
Nano - bubble air flotation devices generate nanoscale bubbles. Their large specific surface area enhances the adsorption of pollutants. The nanobubbles attach to fine particles and colloidal substances, lifting them to the surface for removal.
