Device for treating slurry by separating the solids from the liquids in the slurry, said device comprising: - a frame for supporting the elements of the machine; - at least one compartment for separating said solids and liquids, said compartment comprising a base that is concavely curved according to a cylindrical portion having a transverse axis and is formed of a sieve; - at least one idler roller that is mounted transversely on a pair of arms , said pair of arms rotating about a first transverse shaft , a rotational interface also being defined between said pair of arms and said idler roller , which interface allows said idler roller to rotate freely about a second transverse shaft, such that a contact interface is defined between an outer surface of the idler roller and said sieve; - driving means which rotate said pair of arms about the first transverse shaft , and - resilient means for adjusting the pressure exerted by the idler roller on the sieve, such that the rotation of the arm presses the slurry entering the machine against the sieve, and said liquids pass through the corresponding sieve, - a bar being articulated on both ends of each pair of arms , wherein said bars are subjected to the action of resilient means, wherein the contact interface between the sieve and the idler roller is made of a non-metal material on at least one of the two contacting surfaces that form said interface, such that, at said interface, there is no metal-on-metal contact between surfaces moving relative to one another, characterised in that the idler roller , on at least one of the ends thereof, has a shaft portion that is inserted into a hole or recess in a subcomponent which is made of a non-metal material and attached to said arm , said shaft portion coming into contact with said subcomponent at the surface of said hole or recess , the shaft portion rotating with respect to said subcomponent inside said hole , and that said sub-component comprises two additional holes for connecting said sub-component to mating projections on said arm . - a frame for supporting the elements of the machine; - at least one compartment for separating said solids and liquids, said compartment comprising a base that is concavely curved according to a cylindrical portion having a transverse axis and is formed of a sieve; - at least one idler roller that is mounted transversely on a pair of arms , said pair of arms rotating about a first transverse shaft , a rotational interface also being defined between said pair of arms and said idler roller , which interface allows said idler roller to rotate freely about a second transverse shaft, such that a contact interface is defined between an outer surface of the idler roller and said sieve; - driving means which rotate said pair of arms about the first transverse shaft , and - resilient means for adjusting the pressure exerted by the idler roller on the sieve, such that the rotation of the arm presses the slurry entering the machine against the sieve, and said liquids pass through the corresponding sieve, - a bar being articulated on both ends of each pair of arms , wherein said bars are subjected to the action of resilient means, <EOS>