A filter press, a pressing method and a pressing plant for treating sludge and separating a liquid fraction from a solid mass includes a filtration column having a loading/pressing module for the sludge, fixed and extending vertically, the loading/pressing module including a cylindrical outer shell, a perforated collector tube positioned inside the outer shell and disposed vertically, an impermeable membrane deformable under pressure and disposed between the outer shell and the perforated collector tube, and a pressing chamber defined by that surface of the membrane facing the perforated collector tube, wherein a filter is provided inside the pressing chamber about the outer wall of the collector tube, said the membrane is deformable by the inner wall of the outer shell towards the filter. and a shutter is provided in the bottom of the pressing chamber.