The combined air flotation machine is mainly used for solid-liquid or liquid-liquid separation. By using a gas dissolution and release system to generate a large number of fine bubbles in water, they adhere to the state of wastewater with a density lower than water, and rely on buoyancy to rise to the water surface, thereby achieving the purpose of solid-liquid or liquid-liquid separation. In the field of water treatment, air flotation machines are applied in the following areas: 1. Separation of fine suspended solids, algae and other micro aggregates in surface water. 2. Recycling useful substances from industrial wastewater, such as pulp in papermaking wastewater. 3. Replace the separation and concentration of suspended solids such as sludge in secondary sedimentation tanks. Air flotation mainly utilizes the microbubbles generated by the dissolved air system in the dissolved water, which adhere to the suspended flocs in the water. The suspended solids rise to the water surface along with the microbubbles, forming floating slag and removing the suspended flocs in the water.