Cooling tower blowdown water recycling method

PURPOSE: A method for re-treating cooling tower blowdown water is provided to save costs required for installation by purifying and recycling blowdown water without a decarbonizing tower. CONSTITUTION: A method for re-treating cooling tower includes the following: a condensing agent is introduced into at least part of blowdown water discharged from a cooling tower(100); phosphoric acid components and suspended materials in the blowdown water are condensed; an anti-slime agent is introduced into the condensed blowdown water; the condensed blowdown water is filtered, and the suspended materials are eliminate to introduce a residual chlorine reducing agent into the filtered blowdown water; a scale preventive agent is introduced into the blowdown water without the suspended materials; carbonate ions or bicarbonate ions are separated from the blowdown water; and the blowdown water is filtered through a reverse osmosis membrane separator(170).