Analysis on the Application of Several Aerators in Wastewater Treatment

Use of aerator in sewage treatment process

       Biological treatment methods can be divided into two categories: aerobic and anaerobic according to the aerobic conditions
of the microorganisms involved. In the same situation, the aerobic method is more suitable for lower-concentration sewage, such
as ethylene plant sewage;

       The anaerobic method is more suitable for treating sludge and higher concentration sewage. 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, and it is a method of removing organic matter in sewage that relies on activated
sludge. The aerobic microorganisms present in activated sludge can only function in the presence of oxygen. In the aeration tank
of the sewage treatment biochemical system, the oxygenation effect is positively correlated with the growth of aerobic microorganisms.
The supply of dissolved oxygen depends on the number of aerobic microorganisms, physiological characteristics, matrix properties and concentration.

        Considering. In this way, activated sludge can be in the best state of degrading organic matter. According to explorations, it is
advisable to maintain the dissolved oxygen in the aeration tank at 3 to 4 mg/l. If the oxygen supply is insufficient, the performance of
activated sludge will be poor, resulting in a decline in the effectiveness of wastewater treatment. In order to ensure adequate oxygen
supply, it must be done by a device, such as an aerator.

       Aeration principle of various aerators

       Principle of Aeration Aeration is a means to make air and water come into strong contact. Its purpose is to dissolve oxygen in the
air in the water, or to expel unwanted gases and volatile substances in the water to the air. In other words, it is a means of promoting
material exchange between gas and liquid. It also has other important functions, such as mixing and stirring. The oxygen in the air is
transferred to the water through aeration,Oxygen undergoes mass transfer from the gas phase to the liquid phase. This theory of mass
transfer and diffusion is currently most widely used in the double membrane theory proposed by Lewis and Whitman. The double membrane
theory believes that at the "air-water" interface.There are air and liquid films on the air film, air and liquid flow outside the air film and the
liquid film, which is a turbulent state; the air film and the liquid film are in a laminar flow state, there is no convection, and a pressure gradient
will appear under certain conditions And concentration gradient. If the oxygen concentration in the liquid film is lower than the saturation
concentration of oxygen in the water, the oxygen in the air will continue to diffuse inward through the liquid film and enter the water body,
so the liquid film and the gas film will become a barrier to oxygen transmission. This is the double membrane theory. Obviously, overcome
the liquid film barrier. The most effective method is to quickly change the "gas-liquid" interface. This is the case with aeration and stirring.
The specific method is to reduce the size of the bubbles, increase the number of bubbles, increase the turbulence of the liquid, increase the
installation depth of the aerator, and prolong the contact time between the bubbles and the liquid. Aeration equipment is widely used in
sewage treatment based on this approach.