Water treatment process and water treatment system

A water treatment system, comprising:

• a scale inhibitor supplying section that supplies a calcium scale inhibitor which is a scale inhibitor for inhibiting the deposition of a scale containing calcium to water containing Ca2+ ions, SO42− ions, and carbonate ions;
• a demineralizing section that is positioned on a downstream side of the scale inhibitor supplying section and separates the water fed from the scale inhibitor supplying step into concentrated water in which the Ca2+ ions, the SO42− ions, and the carbonate ions are concentrated and treated water;
• a crystallizing section which is positioned on a downstream side of the demineralizing section and which includes a crystallizing tank that crystallizes gypsum from the concentrated water and a seed crystal supplying section that supplies seed crystals of gypsum to the crystallizing tank;
• a pH measuring section that measures the pH of the concentrated water in the crystallizing tank;
• and
• a controlling section that reduces the amount of the seed crystals of gypsum to be supplied when the pH measured in the pH measuring section falls within a pH range of 6.0 or less in which a scale inhibiting function of the calcium scale inhibitor is reduced, and increases the amount of the seed crystals of gypsum to be supplied when the pH measured in the pH measuring section is greater than the pH range.

A water treatment process comprising:

• a first scale inhibitor supplying step of supplying a calcium scale inhibitor which is a scale inhibitor for inhibiting the deposition of a scale containing calcium to water containing Ca2+ ions, SO42− ions, carbonate ions and silica;
• a first pH adjusting step of adjusting the water fed from the first scale inhibitor supplying step to a pH of 10 or more at which the silica is soluble in the water,
• a first demineralizing step of separating the water fed from the first pH adjusting step into first concentrated water in which the Ca2+ ions, the SO42− ions, the carbonate ions and the silica are concentrated and treated water after the first scale inhibitor supplying step and the first pH adjusting step;
• a first crystallizing step of supplying seed crystals of gypsum to the first concentrated water so that gypsum is crystallized from the first concentrated water;
• a first pH measuring step of measuring the pH of the first concentrated water in the first crystallizing step;
• and
• a first supplied amount controlling step of reducing the amount of the seed crystals of gypsum to be supplied when the measured pH falls within a pH range of 6.0 or less in which a scale inhibiting function of the calcium scale inhibitor is reduced, and increasing the amount of the seed crystals of gypsum to be supplied when the measured pH is greater than the pH range.

A water treatment process, comprising:

• a first scale inhibitor supplying step of supplying a calcium scale inhibitor which is a scale inhibitor for inhibiting the deposition of a scale containing calcium and a silica scale inhibitor which is a scale inhibitor for inhibiting the deposition of silica to water containing Ca2+ ions, SO42− ions, carbonate ions and silica;
• a first demineralizing step of separating the water fed from the first scale inhibitor supplying step into first concentrated water in which the Ca2+ ions, the SO42− ions, the carbonate ions and the silica are concentrated and treated water after the first scale inhibitor supplying step;
• a first crystallizing step of supplying seed crystals of gypsum to the first concentrated water so that gypsum is crystallized from the first concentrated water;
• a first pH measuring step of measuring the pH of the first concentrated water in the first crystallizing step;
• and
• a first supplied amount controlling step of reducing the amount of the seed crystals of gypsum to be supplied when the measured pH falls within a pH range of 6.0 or less in which a scale inhibiting function of the calcium scale inhibitor is reduced, and increasing the amount of the seed crystals of gypsum to be supplied when the measured pH is greater than the pH range.

A water treatment system comprising:

• a first scale inhibitor supplying section that supplies a calcium scale inhibitor which is a scale inhibitor for inhibiting the deposition of a scale containing calcium to water containing Ca2+ ions, SO42− ions, carbonate ions and silica;
• a first pH adjusting section that supplies a pH adjuster to the water fed from the first scale inhibitor supplying section to adjust the pH of the water to 10 or more at which the silica is soluble in the water,
• a first demineralizing section that is positioned on a downstream side of the first scale inhibitor supplying section and the first pH adjusting section and separates the water fed from the first pH adjusting step into first concentrated water in which the Ca2+ ions, the SO42− ions, the carbonate ions and the silica are concentrated and treated water;
• a first crystallizing section which is positioned on a downstream side of the first demineralizing section and which includes a first crystallizing tank that crystallizes gypsum from the first concentrated water and a first seed crystal supplying section that supplies seed crystals of gypsum to the first crystallizing tank;
• a first pH measuring section that measures the pH of the first concentrated water in the first crystallizing tank;
• and
• a first controlling section that reduces the amount of the seed crystals of gypsum to be supplied when the pH measured in the first pH measuring section falls within a pH range of 6.0 or less in which a scale inhibiting function of the calcium scale inhibitor is reduced, and increases the amount of the seed crystals of gypsum to be supplied when the pH measured in the first pH measuring section is greater than the pH range.

A water treatment system, comprising:

• a first scale inhibitor supplying section that supplies a calcium scale inhibitor which is a scale inhibitor for inhibiting the deposition of a scale containing calcium and a silica scale inhibitor which is a scale inhibitor for inhibiting the deposition of silica to water containing Ca2+ ions, SO42− ions, carbonate ions and silica;
• a first demineralizing section that is positioned on a downstream side of the first scale inhibitor supplying section and separates the water fed from the first scale inhibitor supplying section into first concentrated water in which the Ca2+ ions, the SO42− ions, the carbonate ions and the silica are concentrated and treated water;
• a first crystallizing section which is positioned on a downstream side of the first demineralizing section and which includes a first crystallizing tank that crystallizes gypsum from the first concentrated water and a first seed crystal supplying section that supplies seed crystals of gypsum to the first crystallizing tank;
• a first pH measuring section that measures the pH of the first concentrated water in the first crystallizing tank;
• and
• a first controlling section that reduces the amount of the seed crystals of gypsum to be supplied when the pH measured in the first pH measuring section falls within a pH range of 6.0 or less in which a scale inhibiting function of the calcium scale inhibitor is reduced, and increases the amount of the seed crystals of gypsum to be supplied when the pH measured in the first pH measuring section is greater than the pH range.