Extracorporeal blood treatment device for operation with a single patient connection, which is connected to an arterial and a venous blood line of an extracorporeal blood circuit, wherein the blood treatment device comprises: a first apparatus for conveying blood, a second apparatus for conveying blood, which comprises means for collecting blood that flows in the venous blood line from a blood treatment unit and means for establishing an overpressure in the means for collecting blood, so that blood collected in the means for collecting blood flows to the patient connection, an arterial closure element or interrupting the flow of liquid in the arterial blood line and a venous closure element or interrupting the flow of liquid in the venous blood line, a control unit for actuating the first and second apparatuses (6, 7) for conveying blood, as well as actuating the arterial and venous closure elements (12A, 12B), wherein the control unit is configured so that the first apparatus for conveying blood and the means for establishing an overpressure in the means for collecting blood as well as the arterial and venous closure element (12A, 12B) are actuated so that in an arterial phase, the first apparatus for conveying blood is operated with open arterial closure element and closed venous closure element at a predetermined first delivery rate, so that blood flows at a predetermined first flow rate (Q a) from the patient connection via the blood treatment unit into the means for collecting blood, and characterised in that the control unit is further configured so that in a venous phase following the arterial phase, the first apparatus for conveying blood is operated with open arterial and closed venous closure element (12A, 12B) at a predetermined second delivery rate, so that blood flows at a predetermined second flow rate (Q v) from the patient connection via the blood treatment unit into the means for collecting blood, and in the venous phase, overpressure is established in the means for collecting blood with the means for establishing overpressure, so that blood flows at a predetermined third flow rate from the means for collecting blood to the patient connection, wherein there is continuous switching between the arterial and venous phases. a first apparatus for conveying blood, a second apparatus for conveying blood, which comprises means for collecting blood that flows in the venous blood line from a blood treatment unit and means for establishing an overpressure in the means for collecting blood, so that blood collected in the means for collecting blood flows to the patient connection, an arterial closure element or interrupting the flow of liquid in the arterial blood line and a venous closure element or interrupting the flow of liquid in the venous blood line, a control unit for actuating the first and second apparatuses (6, 7) for conveying blood, as well as actuating the arterial and venous closure elements (12A, 12B), wherein the control unit is configured so that the first apparatus for conveying blood and the means for establishing an overpressure in the means for collecting blood as well as the arterial and venous closure element (12A, 12B) are actuated so that in an arterial phase, the first apparatus for conveying blood is operated with open arterial closure element and closed venous closure element at a predetermined first delivery rate, so that blood flows at a predetermined first flow rate (Q a) from the patient connection via the blood treatment unit into the means for collecting blood, and characterised in that the control unit is further configured so that in a venous phase following the arterial phase, the first apparatus for conveying blood is operated with open arterial and closed venous closure element (12A, 12B) at a predetermined second delivery rate, so that blood flows at a predetermined second flow rate (Q v) from the patient connection via the blood treatment unit into the means for collecting blood, and in the venous phase, overpressure is established in the means for collecting blood with the means for establishing overpressure, so that blood flows at a predetermined third flow rate from the means for collecting blood to the patient connection, wherein there is continuous switching between the arterial and venous phases.