1. The sewage to be treated enters the filter unit from the water inlet;
2. Water flows from the outside of the filter disc group to the inside of the filter disc group;
3. When the water flows through the channel formed by the ring-shaped ribs, the particles larger than the height of the ribs are intercepted and stored in the space formed by the curved ribs and the gap between the filter disc group and the shell;
4. After filtration, the clean water enters the ring-shaped filter disc and is led out through the outlet.