text: Belt filter designs are crafted using manufacturer design and performance data, operating installations, pilot testing, surveys of similar plants and testing of the wastewater solids to obtain a desired dewatered solid percentage from the sludge or slurry to be processed.
  Belt filters press have 4 main zones: preconditioning zone, gravity drainage zone, linear compression (low-pressure) zone and roller compression (high-pressure) zone. Preconditioned slurry, which is flocculated and/or coagulated depending on the feed and process, is thickened in the gravity drainage zone. The gravity drainage zone is a flat or inclined belt where gravity drainage of free water occurs The gravity drainage area is sized according to feed solid concentrations. The standard size can be used for solids concentrations of 1.5 percent or greater, but a setup with a longer drainage area or extended size should be used for 1.5 to 2.5 percent feed solids for more free water drainage before compression. For dilute sludge with feed solids of less than 1.5 percent, an independent gravity drainage belt can be used. This belt is used only in the gravity drainage area, not in the pressure zones. The pressure or wedge zones use two belts, upper and lower, to sandwich the feed together, but an independent gravity zone has its own separate belt, making the belt filter a three-belt system. Depending on the required conditions of the cake, belt filters can have added washing stages and, infrared, hot gas or even microwave drying stages.
  Belt filters are very versatile and are made to suit the sludges, slurries or mashed fruit to be processed. For a feed or treatment process which produces unpleasant odours, volatile emissions, pathogens and hazardous gases like hydrogen sulphide the belt filter can include fume hoods or even be completely enclosed in a gas tight housing.  Due to the reduced visibility and increased corrosion associated with enclosure, the belt filter process can also be automated. Large filtration areas, additional rollers and a variable belt speed can be found in advanced belt press filter designs.