Belt presses are designed for use in municipal, industrial or specialized applications where removal of a liquid (usually water) from a solid-liquid suspension, slurry, is desirable. A Belt Filter Press does this through the use of two or three porous belts, which allow both gravity and pressurized dewatering. In the gravity stage, the sludge is allowed to thicken and most of the filtrate, water, is removed. During the pressure filtration stage, the sludge is also exposed to shear forces that greatly increase filtration. The filtrate removed is captured and piped to the base of the machine. This water which has a very low solids is often drained back to the head of the plant. In some instances, the filtrate may be recycled as belt wash water. The discharge of the machine is a friable cake with greatly increased solids content. When equipped with three belts they can be operated as a gravity belt thickener or belt filter press.