Particularly in the manufacture of German "Hefeweizenbier" (beer brewed from wheat), it is important to present the customer a product with a consistent quality of the turbidity. Problems occur particularly in high storage tanks because the yeast concentration varies due to sedimentation. The use of separators is suitable in this case to compensate the concentration. The stored beer is separated. Simultaneously, unseparated beer is added through a bypass to ensure constant turbidity values throughout the entire production cycle. For this purpose, the turbidity is measured at the outlet of the separator and after mixing. The control valve in the bypass pipe is then controlled by these two values and the nominal value.