Water for use in a self-contained water using unit, such as an aircraft, watercraft, ground conveyance, or stationary unit, is treated so that water of different qualities can be distributed to different use locations in the self-contained unit. The treatment is performed by a process using a combined high temperature fuel cell (1) operating at temperatures above 500 C. and a turbine (6) with a reformer process (2) integrated into the fuel cell. The reformer process is operated by the heat of the fuel cell which uses a hydrocarbon fuel to which contaminated and/or fresh water is admixed. The heat of the fuel cell is used for a water purification process. Purified water is filtered in an active charcoal filter and distributed by a distribution system. At least a portion of the purified water available for distribution is automatically salified.