Process of bubbles attach to particles in dissolved air flotation

Flotation is a physical separation process that is widely used in various industries, including wastewater treatment, mineral processing, and oil recovery. The process you’ve described outlines the fundamental steps involved in the flotation of particles, which are typically less dense than the surrounding liquid. Here’s a brief explanation of each step, with a focus on Dissolved Air Flotation (DAF):

1. Introduction of Gas Bubbles: The process begins with the introduction of fine gas bubbles into the wastewater. In DAF systems, these bubbles are introduced by dissolving air under pressure into the wastewater, which is then released into the treatment tank, causing the air to come out of solution in the form of tiny bubbles.
2. Collision: The gas bubbles collide with suspended matter in the wastewater. This suspended matter can include both solid particles and oil droplets. The collision is a critical step as it increases the likelihood of bubble-particle attachment.
3. Attachment: Once the bubbles come into contact with the suspended matter, they attach to the surface of the particles or oil droplets. This attachment is facilitated by the surface properties of the particles and the gas bubbles, as well as the presence of any surfactants or collectors that may be added to enhance the process.
4. Agglomeration: After attachment, the gas-attached particles collide with each other, leading to the formation of larger agglomerates. These agglomerates are more buoyant due to the reduced effective density caused by the entrapped air bubbles.
5. Further Entrapment: As the agglomerates grow, they can entrap more gas bubbles, which further reduces their effective density and increases their buoyancy.
6. Sweep Flocculation: The final step is the upward rise of the floc structures, which is a sweeping action that helps to separate the agglomerates from the liquid. This process is known as “sweep flocculation” and is effective in removing a wide range of particles, including those that are too small to be removed by sedimentation.
7. In the context of DAF, the effectiveness of the flotation process depends on several factors, including the size and concentration of the particles, the size and distribution of the gas bubbles, the chemistry of the wastewater, and the operating conditions of the flotation unit. By optimizing these factors, the DAF process can be tailored to achieve high separation efficiencies for a variety of applications.
8. Dissolved Air Flotation is particularly effective in treating wastewater with high concentrations of suspended solids or emulsified oils. The use of DAF allows for the efficient removal of these contaminants by creating a stable froth layer that can be easily skimmed off the surface of the water, leaving behind clearer water that can be further treated or discharged.