Sludge filtration device comprising a filter piston, and sludge treatment plant and sludge filtration process thereof

Sludge treatment plant for liquid manure, comprising at least one filtration device which comprises:

• a first filter (1) placed over an approximately horizontal box (4) which can be moved from a filtering position to a cleaning position and vice versa, wherein the filtering position is a position where the first filter (1) constitutes a bottom of a filter chamber (8) of essentially vertical axis,
• a piston (10) suitable for closing the filter chamber at a top part,
• means (3, 11) for causing relative movement between the box (4) provided with the first filter (1) and the piston (10) in order, as the piston and box are being moved closer together, for pressure to be exerted on a volume of a sludge introduced into the filter chamber (8), so that a liquid filtrate flows downwards through the first filter (1) and so that a cake (G) of solid matter remains on the first filter (1),
• and a scraper device (31) provided for removing this cake when the first filter (1) is placed in its cleaning position,
• wherein the piston is made in the form of a filter piston (10) so that an effluent passes through the filter piston (10) as the volume of the filter chamber (8) is being decreased and in that a suction pumping means (P) is provided for removing the effluent above the filter piston (10).