Belt Thickener Process Description

Chemical Dosing

An Or-Tec Blend emulsion polymer feed system automatically makes up and delivers the polymer and water solution to the injection site. As an alternate, a solution of suitable polymer is made up in a stainless steel chemical mixing / storage tank. The tank is usually designed with a capacity for one day's operation of the system.


Sludge is pumped to a stainless steel flocculation tank by a variable capacity pump. Prepared polymer is simultaneously injected to the inlet of the flocculation tank by a variable speed chemical dosing pump. Here a thorough mixing occurs that is aided by a variable speed flocculator fitted in the tank. Speed adjustments are manual.

Thickening Area

Flocculated sludge flows from the flocculator down a sludge feed chute. This chute provides a gentle, even distribution of sludge over the gravity drainage section and a uniform thickness on the thickening belt. The drainage area allows for the separation of the free water contained within the sludge and its consequent discharge into the drainage tray. Capillary action takes place as the thickening belt moves across stainless steel supported UHMW belt supports. The drainage area is sealed by polypropylene skirting that is bolted to the top trays and rests on the filter cloth.

Sludge Discharge

Thickened sludge is continuously removed by a fixed scraper blade acting against the final roller. A thickened sludge pump or screw auger can be used to the convey the thickened sludge.

Filter Belt Washing

The filter belt is continually washed by pump generated high pressure water sprayed through fine nozzles. Belt wash water and filtrate are collected in a stainless steel drainage tray. This runoff is funneled to the customer's drainage system via the supplied 4" diameter flanged outlet in the tray. In most cases, the filtrate is acceptable as reuse for wash water, as is the final effluent of the W.W.T.P.


The system can be automatically controlled. Start-up is simple and requires a minimum of time. The unit's design, incorporating variations in both speed of the belt, sludge pump, polymer dosing and flocculation mixer offer a high degree of flexibility to the end user.