Why does the use of polyaluminium chloride to remove phosphorus in domestic sewage cause total phosphorus to rise

Domestic sewage is a complex and diverse sewage, mainly produced by our daily life, so we call it domestic sewage. There are many pollutants in this kind of water, and phosphorus is a headache pollution. Therefore, in recent years, domestic sewage treatment plants have paid great attention to the treatment of phosphorus pollution in water bodies, and the technology of water treatment and phosphorus removal has increased research efforts. .

At present, the commonly used methods for phosphorus removal in domestic sewage plants in China include chemical precipitation and biological methods, mainly because these two methods are relatively cost-effective and specific. However, there has been a reaction from sewage treatment plants recently that PAC was added to the process of treating domestic sewage to remove phosphorus, but it was unexpected that the total phosphorus would increase. Then why adding PAC to the domestic sewage to remove phosphorus, but increase the total phosphorus, what is the reason?

Sewage plants generally add polyaluminum chloride, calcium chloride, and aluminum sulfate to remove phosphorus. In theory, it may be brought in by polyaluminium chloride or other chemicals. Gongyi Xinqi Chemical Plant found a problem through experiments in the laboratory, and found that the phosphorus content in PAC and aluminum sulfate reached 20,000 ppm. Therefore, when you add polyaluminium chloride to the domestic sewage, a certain phosphorus removal effect can be achieved at about 50ppm at the beginning, but when you add the chemical dosage to 100ppm or even higher, you will find that the phosphorus in the sewage does not drop but rises. The main reason is that the raw materials used to make polyaluminium chloride and aluminum sulfate contain phosphate rock. Moreover, if polyaluminium chloride is put into the biochemical system to make the system disorder, it will also increase the total phosphorus in the short term.