Dissolved air fine bubble diffuser flotation is to make the air dissolved in water under a certain pressure, and reach a saturated state, and then suddenly reduce the dissolved air water to the atmospheric pressure state, which is dissolved in the water of the air, it escapes from the water in the form of smiling bubbles, and the air flotation has been carried out. The bubbles formed by the dissolved air flotation are small, and their initial particle size may be about 80um. In addition, during the operation of dissolved air flotation, the contact time between bubbles and wastewater can also be artificially controlled. Therefore, the purification effect of dissolved air flotation is high, and it has been widely used in wastewater treatment, especially for oily wastewater and fiber-containing wastewater. According to the different pressures of the bubbles precipitating in the water, dissolved air flotation can be divided into two types: pressurized dissolved air flotation and dissolved gas true air flotation. The former air dissolves like water under pressurized conditions and precipitates under atmospheric pressure. Pressurized dissolved air flotation disc air diffuser is a commonly used air flotation method at home and abroad.
Reflux pressurized dissolved gas flotation process: it is to return the effluent to pressurize, and the inflow wastewater is directly into the flotation tank, and the reflux water after the pressurized dissolved gas is in contact with the wastewater in the flotation tank by the pressure reducing valve to separate the solid and liquid. After passing through the pressure reducing valve, the pressure of the pressurized water is reduced to normal pressure, and the dissolved gas in the water will be released in the form of fine bubbles. These fine bubbles adhere to the suspended particles and float to the surface. The scum can be scraped out using a scraper set on the surface, and the clarified water is drawn out by the water collection system at the bottom of the floating separation pool. Due to the large additional flow of the flotation pool caused by the return flow, the volume of the flotation pool should be larger than that of the two systems of total dissolved gas and partial rapid sand filters dissolved gas.