The sludge enters into the dynamic(static)state mixer through the mud pump,and is mixed with the concentration of 0.05-0.1% anion(cation)ion flocculent solution and fully reacted.Then the fine solid particles in the slag(mud)slurry(or suspended matter) coagulates into a bulky flocculent mass,and the bound water and surface water of the sludge is separated into free water.When the sludge is transported and spreaded on the filter line of the extended gravity pre-dewatering zone(or belt concentrator),free water permeates the back of the filter,it is oozed and separated under the action of gravity,forming non-flowing sludge.After reaching the pressing-dewatering zone,The sludge is subjected to the maximum pressure and clamped between the upper and lower mesh belts as the mesh belts moves.Then the rollers run slowly,and the sludge pass the filter belt which can adjust tension and are subjected to extrusion force and shear force by the rollers and the pressure roller whose diameter are gradually decrease and pressure is increase continuously.Water of the sludge is transported to the wedge zone,the low pressure zone,the medium pressure zone,the high pressure zone and the strong pressure zone,and is squeezed continuously with the increasing pressure.Finally the low moisture sludge cakes are discharged and scraped off by the scraper.The upper and lower filter belts are separated,and the small particles of sludge are cleaned up by high pressure water which blockes on the filter mesh.And then the machine will continue to the next dewatering cycle.