The shallow air flotation equipment has changed the static water inlet and dynamic water outlet methods of traditional air flotation, and has become a new dynamic water inlet and static water outlet method. When the suspended matter with microbubbles mixed with sewage enters the air flotation tank , let the outflow device move, so that the horizontal flow rate of the mixed sewage becomes zero relative to the outflow device, so as to control the turbulent flow in the tank, so that a stable solid-liquid separation can be carried out ("Shallow Theory" "Zero Velocity" Principle”), the rising speed of the flotation body reaches or is close to the theoretical rising speed, which greatly improves the treatment efficiency, and reduces the residence time of wastewater in the shallow air flotation tank from the traditional 30-60 min to 3 min, and the agglomeration , slag skimming, drainage and sludge discharge are integrated, which is a kind of waste water treatment device.
Features of shallow air flotation equipment:
1. The residence time of the water to be treated is short, only 3min.
2. High treatment efficiency, especially for high turbidity water.
3. The processing capacity per unit area is 250 m3/(m2·d), and the processing capacity is large.
4. It can be set as multi-layer, and can be set directly on the ground or overhead, with a small footprint.
5. The effective water depth is about 0.4m, which is basically irrelevant to the processing capacity, and the total height of the structure is reduced.
In the traditional air flotation device, the scum scraper regularly removes the scum layer, which cannot be selectively cleaned according to the floating time of the scum. Therefore, it not only disturbs the water body, but also reduces the moisture content of the scum. Larger; in the shallow air flotation device, the screw skimmer is installed in the front of the water distribution system, and the removed scum is always the scum that floats for a long time (2~3 min) in the air flotation tank, that is, solid-liquid separation Thorough, low moisture content scum.
In the traditional air flotation device, the residence time of the water body is generally controlled at 10-20 minutes; while in the shallow air flotation device, the residence time is only 2-3 minutes. In the traditional air flotation device, the dissolved air system is equipped with a dissolved air tank. If calculated according to the actual volume of the dissolved air tank, its hydraulic retention time is 2-4 min; while in the shallow air flotation device, the dissolved air system adopts the dissolved air tank. It is a gas-dissolving pipe, which eliminates the filler, so that the volume utilization rate of the gas-dissolving pipe is 100%, and its hydraulic retention time is only 10~15 s. Among them, the design of the pressure dissolved gas tank is particularly important. There are generally two ways to determine its volume. One is to determine the overflow rate of the cross section, that is, the load rate. The other is to determine the residence time of the dissolved gas water in the tank. The latter is adopted, and the diameter is obtained after determining the height according to factors such as the height of the filler and the requirements of the sensor, with a residence time of 1 minute.
In the traditional air flotation device, the depth of the pool is generally 2.0~2.5 m, because the equipment is static and the water body is moving. When the water body enters the contact area from the reaction chamber, the flow direction will change and the flow rate will be redistributed, that is, the water flow will be transformed into a uniform upward flow, which requires a certain time and height to complete this change, and its height is generally not low. at 1.5 m. However, due to the application of the "zero velocity" principle, the shallow air flotation realizes that the equipment is moving and the water body is static, which eliminates the impact of the disturbance of the water body on the separation of suspended particles and water, and reduces the height requirements. In the traditional air flotation device, it is inevitable that mud sand or floc particles will settle at the bottom of the pool. In order to prevent the mud sand from being carried out of the bottom of the pool, the outlet pipe is generally suspended 300 mm high. device, so there is no need to set up a suspended section. Through the above analysis, the effective water depth of the shallow air flotation device is generally 400-500 mm.
