This water treatment system for effluent generated within a plant facility comprises an exhaust gas treatment system (18) that treats boiler exhaust gas (12) from a boiler (11), and a spray drying device (23) that has a spraying means for spraying the effluent (22) generated in a plant facility, in a cooling tower (21) for example, and that performs spray drying by using a portion (12a) of the boiler exhaust gas (12). Separate treatment of effluent (22) with industrial waste water treatment equipment can be eliminated and discharge of effluent (22) generated within the plant can be eliminated because the discharged effluent (22) is introduced into the spray drying device (23) and the spray liquid is dried by way of the heat from a portion (12a) of the exhaust gas (12).
