Since the 1960s, all countries have studied and developed various new technologies and methods to control water pollution, and the control of pollution has begun to enter a higher stage, that is, a new stage of comprehensive prevention and control of environmental pollution. Due to the diversity of industrial wastewater components, treatment systems often require several methods to achieve the required discharge standards. Biological method is a method that utilizes the metabolic action of microorganisms in wastewater to decompose degradable organic matter in water. It has the advantages of large treatment capacity, low investment, and? The characteristic of economic reliability is that it is the most common water treatment method in the world today.

Aeration is a method of making air come into strong contact with water, with the aim of dissolving oxygen in the air in water or expelling unwanted gases and volatile substances from the water into the air. In other words, it is a means of promoting the exchange of substances between gases and liquids. It also has other important functions, such as mixing and stirring. The oxygen in the air is transferred to water through aeration, and the oxygen undergoes mass transfer from the gas phase to the liquid phase. Currently, the theory of mass transfer and diffusion is widely applied, which is the double membrane theory proposed by Lewis and Whitman. There are gas and liquid films on the "gas water" interface, with air and liquid flowing outside the gas and liquid films, belonging to a turbulent state; The gas film and liquid film belong to a laminar flow state, and there is no convection. Under certain conditions, there will be pressure gradients and concentration gradients.

Biological treatment methods can be divided into two categories based on the oxygen demand of the participating microorganisms: aerobic and anaerobic methods. In general, aerobic method is more suitable for lower concentration wastewater, such as ethylene plant wastewater; The anaerobic method is more suitable for treating sludge and high concentration wastewater. Aerobic biological treatment methods can be divided into two categories: activated sludge method and biofilm method. Activated sludge method is an artificial enhancement method for water self purification, which relies on the active sludge as the main body to remove organic matter from wastewater. Aerobic microorganisms present in activated sludge must be present in the presence of oxygen to function. In the aeration tank of the sewage treatment biochemical system, the aeration efficiency is positively correlated with the growth of aerobic microorganisms. The supply of dissolved oxygen should be comprehensively considered based on the number, physiological characteristics, substrate properties, and concentration of aerobic microorganisms. In this way, activated sludge can be in the optimal state for degrading organic matter.

If the concentration of oxygen in the liquid film is lower than the saturation concentration of oxygen in water, the oxygen in the air will continue to diffuse inward through the liquid film and enter the water body. Therefore, the liquid film and gas film will become obstacles to oxygen transfer?, This is the double film theory. Obviously, overcoming liquid film barriers? The most effective method is to quickly transform the "gas liquid" interface. Aeration stirring is exactly like this. The specific method is to reduce the size of bubbles, increase the number of bubbles, improve the turbulence level of the liquid, increase the installation depth of the aerator, and extend the contact time between bubbles and the liquid. Aeration equipment is widely used in sewage treatment based on this approach.