Another advantage of using cationic polyacrylamide in urban sewage is that when the sewage is treated to the terminal, the sludge needs to be dehydrated, adding an appropriate amount of cationic polyacrylamide products can achieve a better mud-water separation effect, and the water content of the dehydrated mud cake will be about 80%. This advantage of cationic polyacrylamide products is that any flocculant can not exceed the effect. Under normal circumstances, after the mud is treated with cationic polyacrylamide, its mud cake moisture content can be reduced by 55 percent to 80 percent, if the matching equipment is perfect, and the moisture content of these mud cakes can reach about 10 percent.