The main technology of density sedimentation tank is carrier flocculation technology, which is a rapid precipitation technology. It is characterized by adding high density insoluble medium particles (such as fine sand) in the coagulation stage, and using the gravity sedimentation of the medium and the adsorption of the carrier to speed up the "growth" and precipitation of the flocs.

Under the rapid stirring of the fast mixer, the sewage reacts with the hard agent (lime, sodium carbonate, sodium hydroxide), the silicon agent (sodium aluminate, magnesium agent), the fluoride agent (calcium chloride, calcium hydroxide, special fluoride agent), and the coagulant agent (PAC, PFS) to form alum flower in a short time. The addition of reflux sludge can accelerate the growth of alum flowers and increase the density of alum flowers, so as to improve the flocculation effect and sedimentation effect in the sedimentation tank.