Patent ID: 6991733

Claim:
A method for removing trace amount of organic matter from ultrapure water, which comprises the following steps: a) contacting ultrapure water containing less than 100 ppb of total organic carbon (TOC) with ozone, and irradiating the resulting ozone-containing water with an ultraviolet light (UV); b) performing a degassing treatment on the ozone-containing and UV-irradiated water to remove the dissolved oxygen, carbon dioxide and volatile organic matters in therefrom; c) contacting the degassed water from Step b) with an ion adsorption unit in order to reduce the TOC therein; and d) subjecting an effluent from the ion adsorption unit in Step c) to an ozone contact treatment and a UV irradiation treatment in sequence, until the TOC value in the resulting treated water is less than a specified value.