WATER TREATMENT METHOD, AND WATER TREATMENT SYSTEM

摘要

Provided are a water treatment system and a water treatment method with which salt-containing water can be recycled with a high water recovery rate. This water treatment system includes: a first desalinization unit for separating water to be treated including Ca ions, SO4 ions, and carbonate ions, into treated water and concentrated water in which the Ca ions, SO4 ions, and carbonate ions are concentrated; a crystallization unit which is provided at a downstream side of the first desalination unit, and which is provided with a first crystallization tank (21) for inducing crystallization of gypsum from the concentrated water, and a seed-crystal supply unit (22) for supplying gypsum seed crystals to the first crystallization tank (21); a first pH measurement unit (543) for measuring the pH of first concentrated water inside the first crystallization tank (21); and a control unit (24) which, in cases when the pH measured by the first pH measurement unit (543) is in a pH range in which scale-inhibiting function of a calcium-scale inhibitor is reduced, reduces a supply amount of the gypsum seed crystals, and, in cases when the pH measured by the first pH measurement unit (543) is higher than said pH range, increases the supply amount of the gypsum seed crystals.