What are the physical treatment methods for domestic sewage treatment equipment?

Reactions between some compounds in nature, or the working reactions of some mechanical equipment, are generally divided into three attributes: physical, chemical, and biological. For example, wastewater purification can utilize physical and chemical treatment methods. So, what physical treatment methods are there for wastewater treatment equipment to purify sewage?

1. Skimming.

Some food industry wastewater contains a large amount of grease. This grease must be removed before entering the biological treatment process, otherwise it will cause blockage of pipes, pumps, and some equipment, and will also affect the biological treatment process. In addition, grease removal and recovery have considerable economic value. The grease in wastewater can be divided into two categories according to its physical state: free-floating and emulsified. Generally, grease traps remove floating grease. The removal rate of floating grease by grease traps can reach 90% or more. If there is an equalization tank or sedimentation tank in the treatment process, the grease trap can be combined with the equalization tank or primary sedimentation tank into a unified structure, which can save investment and land. For small treatment systems, an oil-water separator can be used for skimming.

2. Screening (Screening).

Screening is a widely used method in pretreatment. Its main function is to separate coarser dispersed suspended solids from wastewater. The equipment used includes bar screens and screens. Bar screens intercept coarser suspended solids, protecting pumps and subsequent treatment equipment. Commonly used screens in food industry wastewater include fixed screens, rotary screens, and vibrating screens. The commonly used aperture of screens is 10-40 mesh.

3. Sedimentation (Gravity Separation).

When wastewater flows into the tank, due to the reduced flow rate, the solid matter in the wastewater settles under the action of neutrality, separating the solid matter from the water.

This process has good separation effect, is simple and easy to implement, and is widely used, such as the grit chambers and sedimentation tanks in wastewater treatment plants. Grit chambers mainly remove solid particles with higher density from wastewater, while sedimentation tanks are mainly used to remove a large amount of particulate suspended solids from wastewater.

4. Flotation (Floating) 。

For some fine particles with a relative density close to that of water, because their self-weight is difficult to sink or float in water, a flotation device can be used. This method injects air into the wastewater and allows it to be released from the water in the form of tiny bubbles. The fine particulate pollutants (such as emulsified oil) in the wastewater with a density close to that of water adhere to the bubbles and rise to the surface with the bubbles, forming foam scum and being removed. According to the different air injection methods, flotation equipment includes pressure dissolved air flotation, impeller flotation, and jet flotation. To improve the flotation effect, coagulants are sometimes added to the wastewater.

5. Equalization.

For food industry wastewater with large fluctuations in water quality and quantity, equalization tanks are often used to adjust the water quality and quantity of wastewater. The equalization time is generally 6-24 hours, mostly 6-12h around. The capacity of the equalization tank is 15-50 。

The above are the five physical treatment methods of our domestic sewage treatment equipment, which I believe will be very helpful to you. These different treatment methods have resulted in different structural designs and different types of equipment. Moreover, because the types of wastewater treated by the equipment are numerous, different treatment methods have different treatment advantages, which compensate for the shortcomings of other treatment methods. Therefore, we should make good use of them.