For municipal sludge with low solids content it may be necessary to thicken the sludge on a belt thickener or drum thickener before dewatering on a belt press. Some types of belt presses have a sufficiently long gravity dewatering zone and therefore do not need to thicken the sludge before the belt press. Filter belts for gravity thickener should usually have high dewatering speed, but the size of the holes in the fabric may also be an important parameter with respect to the desired filtrate purity.
These requirements must be taken into account when selecting the appropriate type of filter belt.
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