WATER TREATMENT PROCESS AND WATER TREATMENT SYSTEM
A water treatment method and a water treatment system that are capable of treating water containing salts to allow recovery of treated water at a high ion removal rate and a high water recovery rate, and allow recovery of high quality gypsum are provided. In the water treatment system, the water to be treated containing Ca 2+ and SO 4 2− is separated into concentrated water in which Ca 2+ and SO 4 2− are concentrated and treated water containing CO 2 in a first demineralizer so that the treated water is recovered. The concentrated water in the first demineralizer is adjusted to a pH at which calcium carbonate can be dissolved and the scale inhibition function of a scale inhibitor is reduced, and then is delivered to a crystallizing tank. In the crystallizing tank, gypsum is crystallized from the concentrated water in the first demineralizer. The gypsum is separated and recovered in a separating section.
1 . A water treatment process comprising:
a scale inhibitor supplying step of supplying a scale inhibitor to water to be treated containing Ca ions, SO 4 ions and carbonate ions;
an upstream side separating step of separating the water to be treated into concentrated water in which the Ca ions and the SO 4 ions are concentrated and treated water containing CO 2 , in a first demineralizer, and recovering the treated water;
a first pH adjusting step of adjusting the concentrated water in the first demineralizer to a pH at which calcium carbonate is soluble and a scale inhibiting function of the scale inhibitor is reduced so that gypsum is deposited from the concentrated water in the first demineralizer;
a crystallizing step of crystallizing crystals of the gypsum from the concentrated water in the first demineralizer having the adjusted pH; and
a recovering step of separating and recovering the crystals from the concentrated water in the first demineralizer.
2 . The water treatment process according to claim 1 , further comprising a second pH adjusting step of adjusting the water to be treated to a pH at which the calcium carbonate is soluble and the scale inhibitor is capable of suppressing the deposition of a scale containing Ca, on an upstream side of the first demineralizer.
3 . The water treatment process according to claim 1 , wherein seed crystals of the gypsum are supplied to the concentrated water in the first demineralizer in the crystallizing step.
4 . The water treatment process according to claim 3 , wherein the separated and recovered gypsum is supplied, as the seed crystals, into the concentrated water in the first demineralizer in the crystallizing step.
5 . The water treatment process according to claim 1 , wherein gypsum having a predetermined size, in the gypsum deposited in the crystallizing step, is separated and recovered in the recovering step.
6 . The water treatment process according to claim 1 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
7 . The water treatment process according to claim 6 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
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15 . The water treatment process according to claim 2 , wherein seed crystals of the gypsum are supplied to the concentrated water in the first demineralizer in the crystallizing step.
16 . The water treatment process according to claim 15 , wherein the separated and recovered gypsum is supplied, as the seed crystals, into the concentrated water in the first demineralizer in the crystallizing step.
17 . The water treatment process according to claim 2 , wherein gypsum having a predetermined size, in the gypsum deposited in the crystallizing step, is separated and recovered in the recovering step.
18 . The water treatment process according to claim 3 , wherein gypsum having a predetermined size, in the gypsum deposited in the crystallizing step, is separated and recovered in the recovering step.
19 . The water treatment process according to claim 4 , wherein gypsum having a predetermined size, in the gypsum deposited in the crystallizing step, is separated and recovered in the recovering step.
20 . The water treatment process according to claim 15 , wherein gypsum having a predetermined size, in the gypsum deposited in the crystallizing step, is separated and recovered in the recovering step.
21 . The water treatment process according to claim 16 , wherein gypsum having a predetermined size, in the gypsum deposited in the crystallizing step, is separated and recovered in the recovering step.
22 . The water treatment process according to claim 2 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
23 . The water treatment process according to claim 3 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
24 . The water treatment process according to claim 4 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
25 . The water treatment process according to claim 5 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
26 . The water treatment process according to claim 15 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
27 . The water treatment process according to claim 16 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
28 . The water treatment process according to claim 17 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
29 . The water treatment process according to claim 18 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
30 . The water treatment process according to claim 19 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
31 . The water treatment process according to claim 20 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
32 . The water treatment process according to claim 21 , comprising a downstream side separating step of separating the concentrated water in the first demineralizer after the crystallizing step into concentrated water and treated water in a second demineralizer, and recovering the treated water.
33 . The water treatment process according to claim 22 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
34 . The water treatment process according to claim 23 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
35 . The water treatment process according to claim 24 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
36 . The water treatment process according to claim 25 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
37 . The water treatment process according to claim 26 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
38 . The water treatment process according to claim 27 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
39 . The water treatment process according to claim 28 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
40 . The water treatment process according to claim 29 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
41 . The water treatment process according to claim 30 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
42 . The water treatment process according to claim 31 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.
43 . The water treatment process according to claim 32 , wherein, on a downstream side of the concentrated water in the second demineralizer, water is evaporated from the concentrated water in the second demineralizer so that a solid is recovered.