1. In the pretreatment stage, the solid content of the original slurry is generally very low, so the slurry concentration must be increased by gravity settlement or other means to reduce the treatment cost. The common pretreatment method is: the concentrated sludge and polymer flocculant mixture, the material under the action of flocculant, fine particles agglomerate, and preliminary precipitation, which is the preparation condition of sludge dewatering machine.
2. In the gravity dehydration stage, the flocculated pre-treated sludge is added to the filter belt. Under the action of gravity, the free water outside the flocculation will filter out through the filter belt, reducing the water content of the sludge.
3. In the wedge-shaped pre-compression dehydration stage, the sludge begins to enter the wedge-shaped squeezing section after gravity dehydration, and the filter zone gap gradually shrinks. The extrusion and shearing effect are started to apply to the sludge, so that the sludge is dehydrated again. After this stage, the sludge fluidity is almost completely lost, thus ensuring that the sludge will not be extruded in the dehydrated section under normal circumstances.
4. During the press and dewatering stage, the sludge is repeatedly squeezed and sheared by the well-designed press roll system to remove a large amount of capillary water and gradually reduce the water content of the sludge, forming sludge filter cake. At the separation of the re-selected filter belt, the filter cake is scraped off by the unloading scraper, and the press cloth is cleaned into the next cycle.