The so-called screen is different from general mesh products. Instead, there is a strict series of mesh sizes. In addition, there are mesh products that meet the industry, agency, and standard classification and screening functions of object particles. The sieve does not say "mesh number", "mesh number" is just a habit for people to describe the screen, which is difficult to overcome for a while. The screen is different from ordinary mesh products in that it has a strict mesh size instead of "mesh number". The size of the screen is not isolated. It consists of a series of mesh sizes for the purpose of hierarchical screening. The screen is woven with metal wire or fiber wire, and the aperture is 0.15 ~ 1mm. Can remove and recover different types and small suspended matter. Screen separation has the advantages of simplicity, high efficiency, and low operating cost. Generally used for small-scale wastewater treatment. There are many types of screens. The two main types are vibrating screens and hydraulic screens.