Municipal sewage and domestic sewage are relatively stable, slightly alkaline, The content of nitrogen and phosphorus is high, generally free of toxic substances, but turbid and malodorous. At the same time, domestic sewage is suitable for the reproduction of various microorganisms, so it often contains a large number of bacteria (including pathogenic bacteria), viruses and parasitic eggs. This kind of wastewater has good biodegradability and is relatively easy to treat. Cationic polyacrylamide is generally used, and its ionicity is about 40-50.

The reclaimed water in municipal wastewater treatment is a kind of water source with great changes in water quality and very difficult treatment. The concentrations of total dissolved solids, COD, BOD, total silicon, ammonia and some other pollutants change very frequently. In addition, the wastewater before treatment contains high concentrations of organic matter, microorganisms and so on. Therefore, any product designed to treat reclaimed water must be able to tolerate this variability and contaminant high concentration of organic matter and living organisms.

In the stage of primary sedimentation tank and secondary sedimentation tank, cationic polyacrylamide is used to accelerate the settlement of suspended solids, most of the sludge dewatering filters are belt filter presses, and medium strong cationic polyacrylamide is generally used, the molecular weight is 9-12 million, the dispensing concentration is 1-2‰ and the dosage per ton of dry sludge is 1.8-3.8kg.