A six-compartment electrodialysis cell with univalent ion selective membranes was used to remove sodium chloride from human urine for Advanced Life Support applications that will be used in long-term space travel. To study the feasibility of this system, the first variable under study was the limiting current density (i(lim).). Working at current densities lower than i(lim) allows obtaining better efficiency of sodium chloride removal and extends the membrane's useful life. The i(lim) data were obtained at four fluid velocities ranging from 0.015 to 0.083 m/s and four urine dilution ratios ranging from 3,200 to 12,800 ppm, based on chloride salts concentration. The i(lim) was found to be a power function of fluid velocity and Cl- salts concentration correlated by the model i(lim) = 4105U(0.9)C. An average current efficiency of 50% based on Na+ ion removal indicated that half of the applied current was used in sodium chloride transport. Higher and more stable current efficiencies than those of continuous flow mode of operation were found for batch recirculation experiments.