The Orbal oxidation ditch water treatment process originated in South Africa, and has been continuously improved and promoted, and has been widely used worldwide. After the urban sewage is concentrated by the pipeline, the water flow first passes through the coarse grid to remove the coarse garbage, and then the sewage is raised by the lift pump (high head is required in the later process), and then passes through the fine grid and the swirling grit chamber to further The small garbage and mud are removed, and the sewage enters the main structure of the water treatment, the oxidation ditch. The sewage is adjusted by the aerator in the "O" type oxidation ditch, so that the sewage can be reacted by anoxia, oxidation, nitrification, denitrification In this process, BOD (biological oxygen consumption), COD (chemical oxygen consumption) removal and wastewater denitrification functions are completed, and preparations are made for the next step of water precipitation. The water treated by the oxidation ditch flows into the final sink. In the pond, Fe3 + or Al3 + is added to precipitate (PO4) 3- in the water. After sufficient precipitation, the clear water is finally disinfected by chlorine dioxide and discharged into the Yangtze River. The precipitated sludge is filtered and dried by a dehydrator and then incinerated.