A sludge or filter press is commonly used to dewater sludge from water or waste water treatment operations.
Sludge/filter presses operate applying very high pressures to the cake (from 5 to 15 bars and sometimes even more). Different techniques are used for different types of sludge/filter presses, to apply the pressure towards the sludge. Filtration time depends on sludge thickness, concentration, specific resistance and compressibility coefficient.
There is a residue (= cake) from the process which accumulates gradually in the filtration chamber until the final compacted cake is formed.