Method for processing protein-containing suspensions or solutions comprising the steps of: providing a filter module having an interior space divided into a retentate chamber and a filtrate chamber by at least one porous membrane wall, the retentate chamber having at least a first liquid access and a second liquid access, and the filtrate chamber having at least one liquid access, providing at least one source of a protein-containing suspension or solution containing protein-containing particles or dissolved protein-containing substance suspended in a carrier liquid, wherein the source of the protein-containing suspension or solution is connectable via liquid lines (151, 154) at least to the first liquid access at the retentate chamber, providing one or more sources of a rinsing liquid (120, 130), wherein the one or more sources of the rinsing liquid (120, 130) is connectable at least to the first or second liquid access at the retentate chamber (101A, 101B) and to the at least one liquid access at the filtrate chamber via liquid lines (152, 153, 154, 155), providing at least one pump means (140, 141) for conveying protein-containing suspension or solution and rinsing liquid through the liquid lines, conveying the protein-containing suspension or solution in a first conveying step from the source of protein-containing suspension or solution into the retentate chamber of the filter module, wherein the source of protein-containing suspension or solution is connected via liquid lines (151, 154) at least to the first liquid access at the retentate chamber, passing liquid of the protein-containing suspension or solution via the membrane wall into the filtrate chamber, optionally discharging the liquid obtained in the filtrate chamber via the at least one liquid access of the filtrate chamber, wherein in a second conveying step, rinsing liquid is conveyed from the one or more sources of the rinsing liquid into the filtrate chamber and into the retentate chamber, and backwashing liquid containing protein-containing particles or dissolved protein-containing substance is discharged from the retentate chamber via the at least second liquid access, wherein the one or more sources of the rinsing liquid (120, 130) are connected at least to the first or second liquid access at the retentate chamber and to the at least one liquid access at the filtrate chamber via liquid lines (152, 153, 154, 155), and characterized in that in the first conveying step, the at least second liquid access at the retentate chamber of the filter module is blocked in a liquid-tight manner. providing a filter module having an interior space divided into a retentate chamber and a filtrate chamber by at least one porous membrane wall, the retentate chamber having at least a first liquid access and a second liquid access, and the filtrate chamber having at least one liquid access, providing at least one source of a protein-containing suspension or solution containing protein-containing particles or dissolved protein-containing substance suspended in a carrier liquid, wherein the source of the protein-containing suspension or solution is connectable via liquid lines (151, 154) at least to the first liquid access at the retentate chamber, providing one or more sources of a rinsing liquid (120, 130), wherein the one or more sources of the rinsing liquid (120, 130) is connectable at least to the first or second liquid access at the retentate chamber (101A, 101B) and to the at least one liquid access at the filtrate chamber via liquid lines (152, 153, 154, 155), providing at least one pump means (140, 141) for conveying protein-containing suspension or solution and rinsing liquid through the liquid lines, conveying the protein-containing suspension or solution in a first conveying step from the source of protein-containing suspension or solution into the retentate chamber of the filter module, wherein the source of protein-containing suspension or solution is connected via liquid lines (151, 154) at least to the first liquid access at the retentate chamber, passing liquid of the protein-containing suspension or solution via the membrane wall into the filtrate chamber, optionally discharging the liquid obtained in the filtrate chamber via the at least one liquid access of the filtrate chamber, wherein in a second conveying step, rinsing liquid is conveyed from the one or more sources of the rinsing liquid into the filtrate chamber and into the retentate chamber, and backwashing liquid containing protein-containing particles or dissolved protein-containing substance is discharged from the retentate chamber via the at least second liquid access, wherein the one or more sources of the rinsing liquid (120, 130) are connected at least to the first or second liquid access at the retentate chamber and to the at least one liquid access at the filtrate chamber via liquid lines (152, 153, 154, 155), and characterized in that in the first conveying step, the at least second liquid access at the retentate chamber of the filter module is blocked in a liquid-tight manner.