At present, the phenomenon of water eutrophication has attracted much attention, and the deterioration of water quality caused by it has seriously affected people's production and life. Eutrophication means that under the influence of human activities, a large amount of nutrients such as nitrogen and phosphorus required by organisms enter slow-flowing water bodies such as lakes and rivers, causing algae and other plankton to multiply rapidly, reducing dissolved oxygen in water bodies, deteriorating water quality, and causing fish. and mass mortality of other organisms. The sources of phosphorus in eutrophic water bodies mainly include phosphorus entering the water body from outside (agricultural fertilization, non-standard discharge of phosphorus-containing industrial wastewater, etc.), and phosphorus released from the sediments inside the water body. Among them, exogenous pollution is the main source of phosphorus, and 80% of phosphorus in lakes, reservoirs and rivers comes from sewage discharge.

Phosphorus is usually present in wastewater in the form of low-concentration phosphates, including organic phosphates, inorganic phosphates (mainly orthophosphates) and polyphosphates, of which orthophosphates and polyphosphates are the main forms. Of course, different sources of wastewater have different levels of phosphorus in various forms. The total phosphorus content in typical domestic sewage is 3-15 mg·L-1 (calculated as phosphorus);

In fresh raw domestic sewage, the distribution of phosphate (as phosphorus) is roughly as follows: orthophosphate 5 mg·L-1, tripolyphosphate 3 mg·L-1, pyrophosphate 1 mg·L-1 and organophosphorus

Studies have shown that phosphorus is the controlling factor for the eutrophication of most water bodies, so it is particularly important to control the concentration of phosphorus. my country's comprehensive sewage discharge standard (GB8978-1996) [3], the primary standard is phosphate (calculated by P) ≤ 0.5 mg·L-1, and the secondary standard phosphate (calculated by P) ≤1.0 mg·L-1 . Therefore, further research on phosphorus removal technology from wastewater and control of phosphorus discharge has become an urgent problem to be solved. At the same time, due to the demand for the use of agricultural chemical fertilizers, natural phosphorus resources are constantly decreasing. Therefore, the recycling and utilization of phosphorus by advanced treatment is also a major issue that people are extremely concerned about in the future.