A device for separating the solid fraction from the liquid fraction of a slurry, comprising a) a container, which defines a chamber for containing said slurry, said chamber having a top and a bottom; b) a filter plate located on the bottom of said chamber to retain the solid fraction of said slurry; c) a conduit for inflow of said slurry into said chamber; d) a conduit for outflow of the filtered liquid through said filter medium; e) a gas inflow conduit for increasing pressure in said chamber; f) a conduit for inflow of washing liquids into said container; g) a shaft installed in said container, which supports a plurality of blades (61, 61); said shaft being adapted to rotate about a substantially and/or generally vertical axis, g1) said shaft being adapted to rotate in both directions about said axis of rotation, g2) the distance of said blades (61, 61) from said filter plate being adjustable, g3) said blades (61, 61) being so conformed as to be able to scrape the solid fraction deposited on said filter plate, when said shaft rotates in one direction of rotation, said blades (61, 61) being adapted to press the solid fraction deposited on said filter plate when said shaft rotates in a second direction of rotation, opposite to said first direction of rotation; h) means (207, 208) for removing the solid fraction retained by said filter medium; characterized in that i) means (24, 240, 25, 250, 26, 260, 29, 290) are provided for withdrawing clarified liquid resulting from gravity sedimentation of the slurry from said container at an adjustable level. a) a container, which defines a chamber for containing said slurry, said chamber having a top and a bottom; b) a filter plate located on the bottom of said chamber to retain the solid fraction of said slurry; c) a conduit for inflow of said slurry into said chamber; d) a conduit for outflow of the filtered liquid through said filter medium; e) a gas inflow conduit for increasing pressure in said chamber; f) a conduit for inflow of washing liquids into said container; g) a shaft installed in said container, which supports a plurality of blades (61, 61); said shaft being adapted to rotate about a substantially and/or generally vertical axis, g1) said shaft being adapted to rotate in both directions about said axis of rotation, g2) the distance of said blades (61, 61) from said filter plate being adjustable, g3) said blades (61, 61) being so conformed as to be able to scrape the solid fraction deposited on said filter plate, when said shaft rotates in one direction of rotation, said blades (61, 61) being adapted to press the solid fraction deposited on said filter plate when said shaft rotates in a second direction of rotation, opposite to said first direction of rotation; g1) said shaft being adapted to rotate in both directions about said axis of rotation, g2) the distance of said blades (61, 61) from said filter plate being adjustable, g3) said blades (61, 61) being so conformed as to be able to scrape the solid fraction deposited on said filter plate, when said shaft rotates in one direction of rotation, said blades (61, 61) being adapted to press the solid fraction deposited on said filter plate when said shaft rotates in a second direction of rotation, opposite to said first direction of rotation; h) means (207, 208) for removing the solid fraction retained by said filter medium; characterized in that i) means (24, 240, 25, 250, 26, 260, 29, 290) are provided for withdrawing clarified liquid resulting from gravity sedimentation of the slurry from said container at an adjustable level.