DRAINAGE WATER VOLUME REDUCTION PROCESS

• Main Authors: TAKEUCHI, KAZUHISA, KAMITO, RYO, KIYOSAWA, MASASHI, ITO, YOSHIAKI, MATSUKAWA, KYOHEI
• Format: Patent
• Language: Chinese; English
• Published: 01.07.2023
• Subjects: CHEMISTRY; METALLURGY; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; SEPARATION; TRANSPORTING; TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

A method for treatment of water having high water hardness, comprising (V) subjecting a raw water to a separation treatment using a reverse osmosis membrane to divide the raw water into a permeated water and a concentrated water, (I) adding an alkali metal hydroxide to a high hardness water (for example, a wastewater from desulfurization, a seawater, etc.) so that the pH is 9.5 to 11.5 to obtain a precipitated product, and removing the precipitated product, (II) adding an inorganic acid and a part of the concentrated water to a liquid from which the precipitated product has been removed so that the pH is not less than 2.5 to obtain a crystallized product and removing the crystallized product, (III) adding an iron-based flocculant to a liquid from which the crystallized product has been removed so that the pH is 2.5 to 4.5 to obtain a first floc and removing the first floc, and if necessary, (IV) adding an alkali metal hydroxide to a liquid from which the first floc has been removed so that the pH is 4.5 to 6.