METHOD AND APPARATUS FOR TREATING RECOVERED WATER TO OBTAIN RECYCLED WATER

PURPOSE:To provide a method for recycling effectively used high purity water by ionizing a nonionic silica component, which does not react with a molybdic acid reagent, contained in the water recovered from the used high purity water and removing the ionized silica component with a reverse osmosis membrane apparatus. CONSTITUTION:In a method for treating recovered water, an ionization apparatus 1 oxidizes the recovered water by a method in which the water recovered from ultra- high purity water used for washing semiconductor and others is introduced into an ozone diffusing tank 11 from its lower part while ozone gas being injected from the lower part. The recovered water from the upper part of the tank 11 is then introduced into an ultraviolet irradiation apparatus 12 from its lower part and irradiated with an ultraviolet lamp set in a transparent glass tube 13. In this way, a nonionic silica component, which does not react with a molybdic acid reagent, contained in the recovered water is ionized, while organic compounds in the recovered water is decomposed. The recovered water from the ionization apparatus 1 is fed into a reverse osmosis membrane apparatus 2, so that the water passed through the membrane is used as recycled water.