Abstract: A two-stage water treatment process. In a first stage, an incoming stream of water is processed to remove impurities and produce an outgoing stream of water usable for a first purpose and a waste stream of water not suitable for the first purpose. In a second stage, the waste stream of water is processed to remove hardness and alkalinity and produce a second outgoing stream of water suitable for a second purpose. In an exemplary embodiment, the first stage is a forward osmosis or nanofiltration process, and the first purpose includes production of potable water. The second stage includes the use of a weak acid cation resin system.