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Kunshan Pinhong EPT Co.,Ltd
Kunshan Pinhong EPT Co.,Ltd
Add : (Qiandeng Yuanchuang Base) No. 125, Jinxing South Road, Qiandeng Town, Kunshan, Jiangsu, China
Tel : （0086）15995617314
Fax : +86-512-50130524
E-mail :lvfang@ksphxs.com
1 Application of aerator in sewage treatment
Biological treatment methods can be divided into two categories: aerobic and anaerobic according to the aerobic conditions of the microorganisms involved. In general, the aerobic method is more suitable for lower-concentration sewage, such as ethylene plant sewage; while the anaerobic method is more suitable for the treatment of sludge and higher-concentration sewage. The aerobic biological treatment method 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 the main body of 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 efficiency is positively correlated with the growth of aerobic microorganisms. The supply of dissolved oxygen should be comprehensively considered according to the number of aerobic microorganisms, physiological characteristics, substrate properties and concentration.
In this way, the activated sludge can be in the best state of degrading organic matter. According to experiments, 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 decrease in wastewater treatment effect. In order to ensure sufficient oxygen supply, it must rely on a device, such as an aerator.
2 The 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 from the water to the air. In other words, it is a means to promote the exchange of substances 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, and the oxygen undergoes mass transfer from the gas phase to the liquid phase. This theory of mass transfer and diffusion is currently widely used in the double membrane theory proposed by Lewis and Whitman.
The double-membrane theory believes that there are air and liquid films at the "air-water" interface. There are air and liquid flows outside the air and liquid films, which are in a turbulent state; the air and liquid films are in a laminar flow state. There is no convection, and pressure gradients and concentration gradients will appear under certain conditions. 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 an obstacle to oxygen transmission.
This is the double membrane theory. Obviously, the most effective way to overcome the barrier of liquid film is to quickly change the "gas-liquid" interface.
This is the case with aeration and stirring. The specific methods are: 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.