Sludge Filter Press for Dewatering

Filter Press can be used as an efficient method to dewater the sludge generated from wastewater treatment plant before sending for disposal. The mode of operation involves forcing the wet sludge under high pressure using a pump and when it passes through the recessed plates covered in filter cloth, most of the solid particles will be captured and trapped in between the gap.

By using sludge filter press, it is possible to achieve much drier and more concentrated cake and this offers an alternative to using sand drying beds for dewatering purpose. However unlike drying beds, sludge filter press requires more attention and constant human intervention to monitor and clear the sludge cake. Other than that, there are also additional costs involved in chemical purchase and filter cloth changing. In order to achieve better efficiency on removal of water, usually the sludge mixture is first dosed with a certain percentage of polymers before going through the filter press. The filtration cycle time can be anywhere between an hour to three hours as long as the pressure remains constant throughout the whole process.

There are basically two different types of filter press for sludge dewatering, one is the fixed volume recessed plate and another is the variable volume type. A fixed volume sludge filter is generally made up of a series of rectangular plates, recessed at both ends and then compacts together by a hydraulic ram. In between each plate, there will be a piece of filter cloth hung on top of it to cover the plate surface. For variable volume recessed plate filter press, there will be a flexible membrane that will actually expand in order to achieve pressure squeeze and thus this helps to reduce the cake volume. All in all, it is possible to achieve final moisture concentration of between 50 to 70 percent depending on how well the system is operated and maintained.

Other than the plate and frame type, there is also another type of dewatering device using a belt operated sludge drying filter press. Thus, depending on different factors such as sludge concentration & characteristics, loading rate and also cost considerations, selection of either plate and frame or belt filter press will offer its own advantages.

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