NOVELTY - A water treatment system has fuel cell assemblies. Anode and cathode of each assembly, support anode and cathode flow field plates through which fuel and oxidant are circulated to anode and cathode, respectively. A degasifier (45) enables the circulated coolant and oxidant to interact with each other, which are treated by removing contaminants from the coolant and humidifying the oxidant.    USE - For fuel cell assembly.    ADVANTAGE - The water treatment system reduces the levels of contaminants in water circulating throughout fuel cell assembly. The efficiency of fuel cell assembly is improved by preventing the degradation of fuel cell material and decrease in conductivity of proton exchange membrane caused by shunt current corrosion. The damages caused to the functioning of fuel cell assembly are prevented by preventing contamination of water collected and circulated through the fuel cell assembly in the coolant channels.    DETAILED DESCRIPTION - A water treatment system (100) has electrochemical fuel cell assemblies (11) which are electrically connected with each other. The anode and cathode of each assembly having an electrolyte, support anode and cathode flow field plates (18,17) through which fuel and oxidant are circulated to the anode and cathode, respectively. One of the flow field plate supports a coolant channel (21) having elemental exhaust manifold through which coolant is circulated. The circulated coolant is exhausted from fuel cell stack, by a coolant conduit (60). The oxidant is provided to the fuel cell stack by an oxidant source generator (47). A degasifier (45) enables the circulated coolant and oxidant to interact with each other which are treated by removing contaminants from the circulated coolant, and humidifying the oxidant. The treated coolant and oxidant are provided to the fuel cell stack by the degasifier.    An INDEPENDENT CLAIM is also included for the method which provides water treatment system to fuel cell stack.    DESCRIPTION OF DRAWING(S) - The figure shows the structure of water treatment system.    Fuel cell assembly (11)    Cathode and anode flow field plates (17,18)    Coolant channel (21)    Coolant pump (37)    Heat exchanger (39)    Demineralizer (40)    Degasifier (45)    Oxidant source generator (47)    Degasifier portion (51)    Coolant conduit (60)    Oxidant exit conduit (62)    Water treatment system (100)