The invention relates to a device (1) for the treatment of a biological fluid, comprising at least three chambers, wherein a first chamber (3), which is provided for receiving the biological fluid, and a second chamber (7), which is provided for receiving a gas, are separated from each other by at least one gas-permeable and liquid-impermeable membrane (9), said membrane (9) being used to transfer gas molecules between the first and second chambers (3, 7), and wherein the first chamber (3) and a third chamber (13) are separated from each other by at least one liquid-permeable membrane (15) which is used to transfer one or more components between the first and third chambers (3, 13). The second chamber (7) is delimited or enclosed by the at least one gas-permeable and liquid-impermeable membrane (9) and is located inside the first chamber (3) or is substantially enclosed by the first chamber (3) such that the biological fluid surrounds the second chamber (7). Similarly, the third chamber (13) is delimited or enclosed by the at least one liquid-permeable membrane (15) and is located inside the first chamber (3) or is substantially enclosed by the first chamber (3) such that the biological fluid surrounds the third chamber (13).