METHOD FOR TREATING CMP WASTE WATER CONTAINING SUSPENDED SILICA

摘要

PROBLEM TO BE SOLVED: To separate CMP waste water containing suspended silica into the concentrated water containing all of the suspended materials contained in the CMP waste water and the condensed water of steam vaporized by vaporizing/ concentrating the CMP waste water containing suspended silica while the generation of scale due to silica is controlled and the volume of the concentrated water is reduced. SOLUTION: The pH value of the CMP waste water containing suspended silica is adjusted to 8-10 by adding alkali, which is then introduced into an evaporator. The introduced CMP waste water is circulated between the evaporator and a heating vessel. The water content of the CMP waste water is vaporized in the evaporator by heating the circulated CMP waste water indirectly through the heat transfer surface of the heating vessel so that the CMP waste water in the evaporator is concentrated.