Filter Presses for Sludge Treatment

For treatment of sludge that is produced by waste water management, the most widely used method is filtration. This method can be used as a part of drainage through sand beds, or it can be utilised as a mechanical means under vacuum with middle or high pressure conditions and these may require using more sophisticated equipment. Filter presses, when they operate apply a very high pressure to the cake which may range from 5 to 15 bars or even more sometimes.

PLATE FILTER PRESS: this pressing technique has high investment cost but despite its intermittent operative functionality, it is the most widely used pressing technique.

DESCRIPTION: a set of vertical plates, which are juxtaposed recessed against each other and using hydraulic jacks is pressed against each other – makes up a filter press. The mechanism ensures that there is optimal pressure applied to the joint face of each of the filtering plate that the plates are able to withstand pressure. The internal pressure is built by the chamber in the sludge pumping system. The plates are placed vertically and this layout of the plates, ensures a watertight filtration chamber which permits an easy mechanism for the cakes discharge. The grooved surfaces of the plates are fitted with finely or tightly meshed filter clothes. The sludge that is to be filtered is pushed through the orifices under pressure in the filtration chamber. The orifices are posited in the center of the plates – this is to ensure a proper uniform distribution of flow and right pressure which results in an improved and better sludge drainage within the chamber. Thus slowly the solid sludge starts accumulating in the chamber and finally the compact cake is formed inside the chamber. The internal ducts help in carrying away this filtrate which is collected at the back of the filtration support. Steps in the filtration cycle:

Filter press is a dewatering process which is performed in an intermittent fashion. It involves the following steps:

1. Press closing: the plates are clamped by the moving jack, when the filter is completely empty. Closing pressure is self regulated through filtration.
2. Filling: flow of the feeding pump regulates the filling. This filling of sludge is done in a short phase. This process has to be quick, so as to avoid the cake formation in the first chamber before the last of the chambers has been filled.
3. Filtration: As the chamber is filled with sludge, an increasing thick layer of sludge forms on the cloth. This leads to a rise in pressure which leads to filtration as the compressed air purges the liquid sludge. This filtration process can be controlled manually.
4. Filter Opening: this process starts from the first chamber, when the moving head is drawn back to disengage the 1st filtration chamber. The cake is disengaged and falls as result of its weight and gravity. The plates are pulled out one by one through a mechanised system. To manipulate the texture of the cake, the speed of plate separation can be adjusted.
5. Washing: the filter clothes should ideally be washed post every 15 – 30 processing operations.

Filter press can be used to process, almost all types of sludge, like hydrophilic organic sludge, hydrophilic inorganic sludge, hydrophobic inorganic sludge, and oily sludge. The scaffolding suppliers in Australia also stock of a range of filter presses and filter fabrics.

Australia based New Bridge Services is a licensed manufacturer and direct supplier of a wide range of industrial and construction- support products. These include skip bins, hook lift bins, and scaffolding equipment.