The process of removing phosphorus from wastewater to prevent eutrophication of water. There are generally two methods: physical and chemical method and biological phosphorus removal method. Physical and chemical methods mainly include adding precipitant into wastewater to precipitate phosphorus into insoluble metal phosphate or metal phosphate. Biological method adopts anaerobic-aerobic treatment process, which uses activated sludge to release phosphorus anaerobically and absorb phosphorus aerobically, and finally realizes phosphorus removal by discharging phosphorus-rich surplus sludge.