Method for separating a suspension by means of a cross flow filtration into a concentrate and a filtrate, wherein: - the suspension is introduced into a suspension chamber with a plurality of chamber-like modules arranged in series, in each of which at least one annular separating element with a separating surface is provided, - for filtration, a differential pressure is set between the suspension chamber and a filtrate chamber, which is located on a side of the separating element facing away from the suspension chamber, - filtrate which penetrates the separating element due to the existing differential pressure, is removed via a filtrate line, - while the suspension remaining in the suspension chamber is thickened to a concentrate, which is removed from the suspension chamber via an outlet, and - in each module at least one agitating member with radially arranged agitating elements is moved in the suspension chamber in a short distance over the separating surface relative thereto, so that, for carrying out a cross flow filtration, a directed flow transversely to the separating surface is produced in a gap between the agitating member and the separating surface, characterised in that - firstly a sieve is used as a separating element, which has an average pore size that is larger than the average particle size of the solid in the suspension to be filtered, - that, in a build-up phase, a cake-forming filtration is carried out, wherein a permeable target particle layer is specifically filtered and built up from the suspension at the sieve, which is then formed as an actual separating medium to separate particles, - that subsequently, in a usage phase, the cross flow filtration is carried out, wherein filtrate penetrates the target particle layer built-up at the sieve and is removed as pure filtrate via a pure filtrate line, wherein the agitating members effect a removing cross flow across the filtration direction and counteract a further attaching of solids at the sieven, - That, in a cleaning phase, the target particle layer is removed from the sieve at certain cleaning points in time by means of flowing back filtrate from the filtrate chamber through the sieve in the suspension chamber, - that, subsequently the target particle layer is re-built by filtration of particles from the suspension during a further build-up phase, and - that the filtrate is removed during the build-up phase separately as turbid flow via an additional turbid flow line. - the suspension is introduced into a suspension chamber with a plurality of chamber-like modules arranged in series, in each of which at least one annular separating element with a separating surface is provided, - for filtration, a differential pressure is set between the suspension chamber and a filtrate chamber, which is located on a side of the separating element facing away from the suspension chamber, - filtrate which penetrates the separating element due to the existing differential pressure, is removed via a filtrate line, - while the suspension remaining in the suspension chamber is thickened to a concentrate, which is removed from the suspension chamber via an outlet, and - in each module at least one agitating member with radially arranged agitating elements is moved in the suspension chamber in a short distance over the separating surface relative thereto, so that, for carrying out a cross flow filtration, a directed flow transversely to the separating surface is produced in a gap between the agitating member and the separating surface, - firstly a sieve is used as a separating element, which has an average pore size that is larger than the average particle size of the solid in the suspension to be filtered, - that, in a build-up phase, a cake-forming filtration is carried out, wherein a permeable target particle layer is specifically filtered and built up from the suspension at the sieve, which is then formed as an actual separating medium to separate particles, - that subsequently, in a usage phase, the cross flow filtration is carried out, wherein filtrate penetrates the target particle layer built-up at the sieve and is removed as pure filtrate via a pure filtrate line, wherein the agitating members effect a removing cross flow across the filtration direction and counteract a further attaching of solids at the sieven, - That, in a cleaning phase, the target particle layer is removed from the sieve at certain cleaning points in time by means of flowing back filtrate from the filtrate chamber through the sieve in the suspension chamber, - that, subsequently the target particle layer is re-built by filtration of particles from the suspension during a further build-up phase, and - that the filtrate is removed during the build-up phase separately as turbid flow via an additional turbid flow line.