Floatation and separation process of flocs with air in air flotation machine of sewage treatment equipment

      After the balance of buoyancy, gravity and flow resistance in the contact chamber, the air flotation machine of sewage treatment equipment with air flocs achieves an upward speed of U. After entering the separation zone, it is affected by two forces: one is the horizontal velocity u generated by the horizontal thrust after the water flow diffuses; the other is the downward velocity u caused by the bottom outflow. The combined velocity and direction of the two flow rates determine whether the aerated flocs are removed by floating or carried out with the flow. The ascending or descending velocity depends on the projection of the resultant velocity u on the longitudinal axis. This speed affects the treatment effect of the air flotation machine. The size of flocs, the size of bubbles and the downward velocity of water flow in the flotation tank directly affect the upward velocity of synthesis. The higher the synthesis upward speed is, the higher the removal efficiency of air flotation is, the smaller the air flotation tank body is, and the lower the whole project cost is. In order to make the floating effect good, first try to reduce the U under the pool body. It can be realized by enlarging the outflow area at the bottom or improving the uniformity of the effluent. With the uniform concentration and outflow of the bottom, the U level of the water flow to the end of the tank is about zero, which is conducive to the separation of the aerated flocs with less buoyancy. If the floating removal is to be realized in advance, the U level should be reduced as much as possible, which can be achieved by expanding the cross section of the atmospheric floating tank. Then, the size of flocs should be well treated, which can be completed by dosing, mixing and flocculation reaction. Attention should be paid to the following points: the type of agents, the dosage, the mixing time and intensity of the chemicals and sewage, the dosing points of the reagents, the reaction time and intensity of the reagents and sewage, and the size of the generated flocs. In addition, the bubble size in the dissolved gas system should be controlled.

     The movement of particles in the separation zone of vertical flow flotation tank is similar to that of horizontal flow flotation tank. However, the horizontal velocity is much smaller, and with the increase of radial distance, the cross-section expands rapidly and the U-plane decreases rapidly. In particular, the vertical flow has little change in the direction of velocity, and the flocculation is mainly affected by the inertial action of upward flow driving force, and the upward fractional velocity of particles increases, which makes the separation conditions of aerated flocs and water body much better than that of horizontal flow. However, what form should be adopted should be determined after comprehensive evaluation of various conditions.

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