Enviroquip® Gravity Belt Thickener
The Enviroquip® Gravity Belt Thickener concentrates sludge using gravity-induced settling and compaction of sludge solids alongside simultaneous dewatering or decanting.
Gravity thickening processes vary depending on the solids to be thickened. Generally sludge is stirred for a relatively long period (8 to 12 hours) in a thickener unit. This forms channels or passageways in the sludge mass, allowing water to escape and a more cohesive floc mass, with a reduced moisture content, to form.
Thickening may be carried out in a specially equipped tank, similar to a clarifier. Thickening units consist of a series of upright chambers, called pickets, attached to the raking arms. The successful operation of this method of thickening relies on the continuous addition and mixing of dissolved oxygen-bearing water with the dilute sludge from the secondary clarifiers and the over flow of excess sludge from the digester. The continued flocculation of this aerobic mixture, followed by settling of the sludge particles and retention of the settled material for a sufficient length of time cause an appreciable compaction of sludge particles. All of these successive phases take place in the same tank; a pre-mix basin may also be used.
Compaction of the sludge blanket at the bottom of the tank occurs by two means: compression due to weight of the solids themselves, and the release of occluded water. The arms of the mechanism pass continually through the sludge mass, opening up channels within the mixture and permitting water to escape.