PURE WATER PRODUCTION METHOD, PURE WATER PRODUCTION DEVICE, AND ULTRAPURE WATER PRODUCTION SYSTEM

• Main Authors: YAMADA KENGO, NOGUCHI YUKIO
• Format: Patent
• Language: English; Japanese
• Published: 13.05.2024
• Subjects: CHEMISTRY; METALLURGY; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; SEPARATION; TRANSPORTING; TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

To provide a pure water production method and a pure water production device that can reduce an amount of a chemical used and efficiently produce pure water in which boron concentration has been reduced, by reducing the processing load of a three-stage reverse osmosis membrane device on a front stage.SOLUTION: There is provided a method for producing pure water in which boron is removed from raw water by treating it with at least three stages of an ultra-low pressure reverse osmosis membrane device, in which all reverse osmosis membranes are negatively charged membranes that have a skin layer made of crosslinked aromatic polyamide, and the raw water contains 1 to 100 mg/L of carbonic acid and 150 μg/L or less of boron. The method includes the steps for: treating the raw water with a first-stage reverse osmosis membrane device; obtaining alkaline water to be treated; treating the alkaline water to be treated with a second-stage reverse osmosis membrane device; and treating the permeated water with a third-stage reverse osmosis membrane device to obtain pure water with a boron concentration of 3 to 20 μg/L and an electrical conductivity of 0.3 to 40 μS/cm.SELECTED DRAWING: Figure 4 【課題】前段側で３段の逆浸透膜装置の処理負荷を軽減することで、薬剤使用量を低減することができ、効率よくホウ素濃度の除去された純水を製造することのできる純水製造方法及び純水製造装置の提供。【解決手段】原水を、少なくとも３段の超低圧型の逆浸透膜装置で処理して原水中のホウ素を除去する純水製造方法であって、逆浸透膜は、いずれも、架橋芳香族ポリアミドからなるスキン層を有する負電荷膜であり、原水が、炭酸を１～１００ｍｇ／Ｌ、ホウ素を１５０μｇ／Ｌ以下含有し、原水を第１段目の逆浸透膜装置で処理する工程と、アルカリ性の被処理水を得る工程と、アルカリ性の被処理水を第２段目の逆浸透膜装置で処理する工程と、その透過水を第３段目の逆浸透膜装置で処理して、ホウ素濃度が３～２０μｇ／Ｌ、導電率が、０．３～４０μＳ／ｃｍの純水を得る工程と、を有する。【選択図】図４