The present invention relates to a system for the treatment of blood, in particular a highly efficient system for the safe removal of CO2 and bicarbonates from the blood in a blood circuit connected to a patient by means of a venous-venous connection having at least an inlet or tube line (1) for receiving a flow of blood for CO2 (or bicarbonate) removal and an outlet or tube line (9) for the blood deprived of CO2 (or bicarbonate)； the system comprises:—an hemofilter (or dialyzer) (3), disposed between said inlet (1) and said outlet (9), and provided with means for separating the plasmatic water from the blood and for conveying the same plasmatic water thru a second tube line (4)；—a device (6) for removing bicarbonates and/or CO2, disposed and acting on said second tube line (4), in a position which is downstream of said hemofilter (3) and upstream of a third tube line (8) which brings back the treated plasmatic water in the blood circuit downstream of said hemofilter (3).
