Devices and methods for regenerating dialysate are disclosed. In certain aspects, the present disclosure provides a multi-stage dialysate regenerating device comprising a first stage having a filter membrane for filtering a dialysate solution into a first fluid flow and a second fluid flow and a second stage having an osmotic membrane for allowing transfer of solvent from one of the first or second fluid flow into the other. Multi-stage dialysate regenerating devices with at least one stage operating by forward-osmosis are also disclosed.
