Water splitting membrane separator is positioned between the electrodes in an electrochemical cell for removing ions from a solution stream comprises a housing having first and second electrodes. A water splitting membrane comprises a cation exchange surface facing the first electrode and an anion exchange surface facing the second electrode. A solution stream pathway is defined by the water-splitting membrane. The solution stream pathway comprises an inlet for influent solution stream, a channel that allows influent solution stream to flow past at least one surface of the water-splitting membrane to form one or more treated solution streams and a single outlet that combines the treated solution streams to form a single effluent solution. Preferably, the solution stream pathway comprises a unitary and contiguous channel that flows past both the cation and anion exchange surfaces of the water-splitting membrane, and more preferably is connected throughout in an unbroken sequence and extends substantially continuously from the inlet to the outlet.