Abstract: In a centrifuge of the type in which the solids are continuously discharged through nozzles, the nozzles are dimensioned to ensure that the volume of solids discharged from them is smaller than the volume of solids fed into the centrifuge through a feed line. The solids space in the centrifuge accordingly fills up gradually and, when it is full, the clarified phase begins to get turbid. The level of turbidity is determined by a photocell and the flow of clarified phase returned to the feed line through a diversion valve. Since the amount of liquid being fed into the centrifuge is maintained at a constant level, the volume of new liquid flowing into the centrifuge is decreased by an amount equal to the volume of clarified phase being recirculated.