Belt Filter Press Basics and Troubleshooting

06 May.,2024

 

Belt Filter Press Basics and Troubleshooting

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If you are having trouble installing lacing wire through the belt clips, try straightening the first foot of wire and file the end to a point. Hand-feed what you can, then attach a drill to the end of the wire. Use the slow speed. It should spin with ease.

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Belt filter presses for sludge dewatering

Belt filter presses for sludge dewatering

Posted on

18 June 2020

How belt filter presses work

A belt filter press (BFP) provides sludge dewatering by pressing the sludge to force the water through a permeable medium. The process produces a cake (the dewatered product) having a dry solids (DS) content of 30% or more in the case of primary sludge. This is to be distinguished from the lower-energy gravity belt thickener process which achieves a maximum DS content of ~10%.

A BFP combines drainage and mechanical pressure sequentially to remove water. The equipment normally comprises 2−3 recirculating belts, with two belts combining at some point to compress the sludge and squeeze water from it.

The conditioned sludge feed is first conveyed along a gravity drainage section of one of the porous belts, as with a gravity belt thickener. It is then subject to pressure as it is passed between two recirculating belts, forming a wedge zone at the inlet, which travel over a roller. This squeezing action from the two belts in this pressure zone releases more water.

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Example arrangement of belts and rollers for a belt filter press, dual-belt system

Credit: Judd Water & Wastewater Consultants

Example arrangement of belts and rollers for a belt filter press, dual-belt system

Credit: Judd Water & Wastewater Consultants

Many belt filter press technologies contain a second pressure zone comprising a series of rollers through which the two belts pass with the sludge solids retained between them. The rollers in this high pressure zone apply tensioning (i.e. stretching) to the belts, exerting both shearing and compressive forces on the sludge which further release more water.

Some BFP technologies are based on a three-belt system, where the gravity belt is independent of the two pressurising belts. This allows the recirculation rate for the thickening operation to be separately adjusted from the dewatering operation.

In common with the gravity belt thickener, the belts are subject to cleaning with water spray to limit the plugging of the filter belt pores. The waste washwater is combined with the filtrate.

The overall performance of the BFP is dependent on the feed sludge source and characteristics and the dosing conditions. As with all other thickening and dewatering technologies, primary sludges – both raw and anaerobically digested – are more readily filtered than waste activated sludge (WAS).

Dewatered sludge generated from a belt filter press

Dewatered sludge generated from a belt filter press

Belt filter press Alfa Laval

Belt filter press Alfa Laval

Source: Alfa Laval / YouTube

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Table 1. BFP dewatering DS concentration of feed and dewatered sludge (cake), polymer dose, liquid and sludge solids and solids recovered (Metcalf & Eddy, 2014; Andreoli et al, 2007) Sludge origin % DS content − Feed % DS content − Cake / Typical % DS content − Cake / Range Loading/m belt width − liquid m3/h Loading/m belt width − solids kg/h Polymer dose − g/kg DSPrimary4−83026-3514−381130−15901.5−2.5Waste activated sludge (WAS)1−21612-2011−23180−3405−10Sequencing batch reactor (SBR)1−21612-1911−22250−3605−7.5Membrane bioreactor (MBR)1−21511-1816−25230−3205.5−10Anaerobically-digested (AD) primary2−52824-3514−37680−9102−5Anaerobically-digested WAS2−32013-236.6−20230−4104−10Mixed, primary + WAS3−52315-259.0−27340−8203−5.5Mixed, AD primary + WAS2−42415-289.0−27320−5404−8.5