JP2020157273A - Water treatment apparatus and water treatment method - Google Patents

Abstract

To provide a water treatment apparatus and a water treatment method for obtaining treated water that can be used as raw water for pure water production, water for facilities, or the like.SOLUTION: A water treatment apparatus, comprising first pretreatment means 2 that adjusts the pH of wastewater w1 containing fluorine and ammonium to a range of 9 to 11, and adds thereto a scale dispersant Sc; a first reverse osmosis membrane 3 that is installed at the rear of the first pretreatment means, and separates wastewater w1 into primary permeated water w11 and primary concentrated water w12; second pretreatment means 4 that adjusts the pH of the primary permeated water w11 that has passed through the first reverse osmosis membrane 3 to a range of 5 to 9, and adds thereto a slime inhibitor Slm; and a second reverse osmosis membrane 5 that is installed at the rear of the second pretreatment means 4, and separates the primary permeate water w11 into a secondary permeated water w21 and a secondary concentrated water w22.SELECTED DRAWING: Figure 1

Description

The present invention relates to a water treatment apparatus and a water treatment method.

In the semiconductor manufacturing process, treatments such as etching and film formation are performed, and pure water is used for these treatments. Pure water after use is discharged as wastewater. In addition, exhaust gas cleaning equipment such as scrubbers may be installed in semiconductor manufacturing plants, and in this case, wastewater from scrubbers is also generated.

In a semiconductor manufacturing plant, these wastewaters are collected in one place and purified by a water treatment device. The purified purified water is supplied to the pure water production apparatus, supplied to the scrubber as water for the scrubber, or discharged to the outside. The purified water supplied to the pure water production equipment and scrubber becomes pure water or water for scrubber and is reused in the semiconductor factory.

The wastewater discharged from the semiconductor manufacturing process contains fluorine, ammonia and the like. Further, in the scrubber, a part of the scrubber water evaporates, so that the impurity component in the scrubber water is concentrated. Examples of such impurity components include calcium. Therefore, the water treatment equipment of the semiconductor manufacturing factory is required to have the ability to remove these substances.

Patent Document 1 contains fluoride as a method for treating fluorine-containing wastewater, which is adjusted to pH 8 or higher by adding an alkali metal hydroxide when the wastewater is separated into permeated water and concentrated water by a reverse osmosis membrane. A treatment method for separating a reverse osmosis membrane by passing wastewater through a reverse osmosis membrane is described. Further, Patent Document 1 describes that a denitrification step of removing ammoniacal nitrogen remaining in the permeated water is performed after the reverse osmosis membrane is separated.

However, the method for treating fluorine-containing wastewater described in Patent Document 1 does not assume the treatment of wastewater from equipment in which the water used is concentrated by evaporation. For example, in the wastewater from the scrubber, Ca is concentrated by evaporating a part of the water used, but in the wastewater containing Ca and fluorine, CaF ₂ is precipitated, and this CaF ₂ clogs the reverse osmosis membrane. There is a risk that it will end up.

Further, in the method for treating fluorine-containing wastewater described in Patent Document 1, the pH of the wastewater is adjusted to 8 or more at the time of reverse osmosis membrane separation, but at this time, ammonia in the wastewater is gasified and released. May be done.

Further, as a method for treating wastewater containing fluorine other than the treatment method described in Patent Document 1, it is conceivable to add Ca to the wastewater to coagulate and precipitate fluorine as CaF ₂ . However, when the treated water treated by this method is reused in a pure water production apparatus or a scrubber, it is necessary to remove the high concentration Ca contained in the treated water, for example, a Ca removing facility such as a water softener. You will need a new one. The water softener in this case is expected to be quite large, and the treatment cost may increase significantly.

Japanese Unexamined Patent Publication No. 2003-103260

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a water treatment apparatus and a water treatment method for obtaining treated water that can be used as raw water for pure water production, water for equipment, and the like. ..

In order to solve the above problems, the present invention adopts the following configuration.
[1] For wastewater containing fluorine and ammonium, a first pretreatment means for adjusting the pH in the range of 9 to 11 and adding a scale dispersant, and
A first reverse osmosis membrane, which is installed after the first pretreatment means and separates the wastewater into primary permeated water and primary concentrated water.
With respect to the primary permeated water that has permeated the first reverse osmosis membrane, a second pretreatment means for adjusting the pH in the range of 5 to 9 and adding a slime inhibitor, and
It is characterized by being provided after the second pretreatment means and provided with a second reverse osmosis membrane that separates the primary permeated water into secondary permeated water and secondary concentrated water. Water treatment equipment.
[2] The water treatment apparatus according to [1], further comprising a fluorine removing means for removing fluorine in the primary concentrated water.
[3] A water tank for storing the secondary permeated water in order to supply the secondary permeated water to the use point, and
Calcium removing means for producing Ca-free water by removing at least calcium in raw water,
A control unit for supplying the Ca-free water produced by the calcium removing means to the water tank when the amount of the secondary permeated water is less than the demand amount of the use point is further provided. The water treatment apparatus according to [1] or [2].

[4] The first pretreatment step of adjusting the pH to the range of 9 to 11 and adding a scale dispersant to the wastewater containing fluorine and ammonium by the first pretreatment means.
A first reverse osmosis membrane separation step of separating the wastewater after the first pretreatment step into primary permeated water and primary concentrated water by a first reverse osmosis membrane.
A second pretreatment step of adjusting the pH to the range of 5 to 9 and adding a slime inhibitor to the primary permeated water after the first reverse osmosis separation step by a second pretreatment means.
A second reverse osmosis membrane separation step of separating the primary permeated water after the second pretreatment step into secondary permeated water and secondary concentrated water by a second reverse osmosis membrane is sequentially performed. A water treatment method characterized by.
[5] The water treatment method according to [4], wherein the fluorine removing step of removing fluorine in the primary concentrated water is further performed by a fluorine removing means.
[6] When the amount of the secondary permeated water is less than the demand for the use point of the secondary permeated water
Ca-free water is produced by removing at least calcium in the raw water by a calcium removing means.
The water treatment method according to [4] or [5], wherein the step of supplying the Ca-free water to the use point is further performed.
[7] The water treatment method according to any one of [4] to [6], wherein the wastewater contains the water used at the use point.

In the water treatment apparatus of the present invention, by flowing the wastewater to which the pH adjustment and the scale dispersant have been added to the first reverse osmosis membrane by the first pretreatment means, fluorine is discharged without causing clogging of the reverse osmosis membrane. Can be removed. In addition, ammonium can be removed by flowing the primary permeated water to which the pH adjustment and the slime inhibitor have been added by the second pretreatment means through the second reverse osmosis membrane. As a result, it is possible to obtain secondary permeated water that can be used as raw water for pure water production equipment and water for equipment. Further, in the water treatment apparatus of the present invention, it is not necessary to install a large-scale water softener because it is not necessary to add Ca when removing fluorine from wastewater. Further, in the water treatment apparatus of the present invention, since ammonium is removed by the second reverse osmosis membrane after adjusting the pH, ammonium can be removed without vaporizing ammonium into ammonia. Further, according to the water treatment apparatus of the present invention, even wastewater containing organic substances can be treated without performing biological treatment such as the activated sludge method.

Further, the water treatment apparatus of the present invention is provided with a fluorine removing means for removing fluorine in the primary concentrated water, and the fluorine removing means may remove fluorine in the primary concentrated water having a smaller amount of water than wastewater. , The treatment capacity required for the fluorine removing means becomes relatively small, and the water treatment device can be made smaller.

Further, in the water treatment apparatus of the present invention, when the amount of secondary permeated water is less than the demand for use points, a control unit that supplies Ca-free water produced by the calcium removing means to the secondary permeated water tank is provided. It is provided so that Ca-free water can be replenished in the water treatment device when the secondary permeated water is insufficient for the demand amount. As a result, when the water circulation system is composed of the water treatment device and the point of use, the Ca concentration of the water flowing in the water circulation system is suppressed to a low level, scale generation is prevented, and the reverse osmosis membrane of the water treatment device is clogged. It is possible to prevent the occurrence of scale at the use point.

Next, according to the water treatment method of the present invention, the reverse osmosis membrane is clogged by flowing the wastewater to which the pH adjustment and the scale dispersant have been added to the first reverse osmosis membrane by the first pretreatment means. Fluorine can be removed without producing it. In addition, ammonium can be removed by flowing the primary permeated water to which the pH adjustment and the slime inhibitor have been added by the second pretreatment means through the second reverse osmosis membrane. As a result, it is possible to obtain secondary permeated water that can be used as raw water for pure water production equipment and water for equipment. Further, in the water treatment method of the present invention, it is not necessary to install a large-scale water softener because it is not necessary to add Ca when removing fluorine from wastewater. Further, in the water treatment method of the present invention, since ammonium is removed by a second reverse osmosis membrane after adjusting the pH, ammonium can be removed without vaporizing ammonium into ammonia. Further, according to the water treatment method of the present invention, even wastewater containing organic substances can be treated without performing biological treatment such as the activated sludge method.

Further, in the water treatment method of the present invention, a fluorine removing step of removing fluorine in the primary concentrated water is performed, and the fluorine removing step may remove fluorine in the primary concentrated water having a smaller amount of water than wastewater. The treatment capacity required for fluorine can be relatively small, and the energy required for water treatment can be reduced.

Further, according to the water treatment method of the present invention, when the amount of secondary permeated water is less than the demand amount of the use point, Ca-free water produced by the calcium removing means is supplied to the use point. Ca-free water can be replenished when the next permeated water is insufficient for the demand. As a result, the Ca concentration of water flowing in the water circulation system composed of the water treatment device and the point of use is suppressed to a low level, scale generation is prevented, clogging of the reverse osmosis membrane of the water treatment device and scale generation at the point of use. Can be prevented.

Further, according to the water treatment method of the present invention, since the wastewater contains the water used at the point of use, the Ca concentration of the water circulating in the water circulation system composed of the water treatment device and the point of use is low. It can be suppressed, scale generation can be prevented, clogging of the reverse osmosis membrane of the water treatment device, and scale generation at the point of use can be prevented.

The schematic diagram which shows the water treatment apparatus which is an embodiment of this invention.

An embodiment of the present invention will be described with reference to the drawings.

The wastewater w1 to be treated by the water treatment apparatus and the water treatment method of the present embodiment is wastewater containing fluorine and ammonium. The waste water w1 contains, for example, pure water used for processing such as etching and film formation in the semiconductor manufacturing process. Further, the wastewater w1 also includes wastewater discharged from an exhaust gas cleaning facility such as a scrubber, and may include wastewater from the use point 31 to which the secondary permeated water w21 is supplied, as will be described later in this embodiment. In addition to fluorine and ammonium, the wastewater w1 may contain phosphate, hydrogen peroxide, calcium, organic substances and the like. For example, fluorine may be contained in an amount of about 1 to 100 ppm, ammonium in an amount of about 10 to 500 ppm, hydrogen peroxide in an amount of about 0 to 300 ppm, calcium in an amount of about 1 ppm, and an organic substance in an amount of about 1 to 100 ppm as a total organic carbon content. In addition, ammonium in the present specification means ammonium ion, but when it is present in the form of ammonia in wastewater, ammonia is also included in ammonium.

In the present embodiment, such wastewater w1 is treated by the water treatment device 1 shown in FIG. Hereinafter, the water treatment apparatus 1 and the water treatment method of the present embodiment will be described.

As shown in FIG. 1, the water treatment apparatus 1 of the present embodiment includes a first pretreatment means 2, a first reverse osmosis membrane 3, a second pretreatment means 4, and a second reverse osmosis membrane. 5 and are provided. Further, the water treatment device 1 of the present embodiment is provided with the fluorine removing means 11. Further, in the water treatment device 1 of the present embodiment, the first water tank 6 and the second water tank 7 (water tank) for storing the secondary permeated water, the calcium removing means 21, and the raw water supply for sending the raw water to the calcium removing means 21. A unit 20 and a control unit 22 are provided. The first water tank 6 is connected to another use point 32, and the second water tank 7 is connected to the use point 31. Further, the water treatment apparatus 1 of the present embodiment is provided with the neutralization treatment means 41. Furthermore, the water treatment apparatus 1 of the present embodiment is provided with hydrogen peroxide removing means 51 for removing hydrogen peroxide in waste water. However, if hydrogen peroxide is not contained in the waste water w1, the hydrogen peroxide removing means 51 may be omitted.

Further, the water treatment device 1 of the present embodiment is provided with a water channel for flowing water between the devices. That is, as shown in FIG. 1, the hydrogen peroxide removing means 51 and the first reverse osmosis membrane 3 are connected by the water channel L1, and the first reverse osmosis membrane 3 and the second reverse osmosis membrane 5 are connected by the water channel L2. Is connected, and the second reverse osmosis membrane 5 and the first water tank 6 are connected by the water channel L3.

Further, the first reverse osmosis membrane 3 and the fluorine removing means 11 are connected by the water channel L4, the fluorine removing means 11 and the neutralization treatment means 41 are connected by the water channel L5, and the second reverse osmosis film 5 is connected by the water channel L6. And the neutralization treatment means 41 are connected.

Further, the first water tank 6 and the second water tank 7 are connected by the water channel L7, the raw water supply unit 20 and the calcium removing means 21 are connected by the water channel L8, and the calcium removing means 21 and the second water tank 7 are connected by the water channel L9. It is connected, the second water tank 7 and the use point 31 are connected by the water channel L10, and the first water tank 6 and another use point 32 are connected by the water channel L11.

The hydrogen peroxide removing means 51 is used when treating the waste water w1 containing hydrogen peroxide. Since hydrogen peroxide is bactericidal and serves as a COD source by itself, it cannot be directly discharged into public water bodies, and hydrogen peroxide must be decomposed. Examples of the hydrogen peroxide removing means 51 include means for adding a reducing agent such as sodium bisulfite and an activated carbon tower capable of continuous water flow. When the waste water w1 contains hydrogen peroxide, it is preferable to first remove the hydrogen peroxide by the hydrogen peroxide removing means 51.

The first pretreatment means 2 adjusts the pH of the wastewater w1 flowing through the water channel L1 to the range of 9 to 11, and adds the scale dispersant Sc. As the first pretreatment means 2, for example, one provided with a primary pH adjusting unit 2a and a primary drug injection unit 2b can be exemplified. The primary pH adjusting unit 2a adjusts the pH of the waste water w1 to the range of 9 to 11 with potassium hydroxide or the like. Further, the primary agent injection unit 2b adds the scale dispersant Sc to the wastewater w1 after adjusting the pH.

The first reverse osmosis membrane 3 separates the wastewater w1 to which the pH adjustment and the scale dispersant Sc has been added into the primary permeated water w11 and the primary concentrated water w12. Fluorine is removed from the wastewater w1 by passing water through the first reverse osmosis membrane 3, and phosphate, calcium and organic substances are also removed to obtain primary permeated water w11. The removed fluorine and the like are contained in the primary concentrated water w12. The first reverse osmosis membrane 3 may be operated, for example, in a state where the recovery rate is adjusted so that the total amount of organic carbon in the primary concentrated water w12 is less than 100 mg / L.

As the first reverse osmosis membrane 3, a spiral type module in which a permeable membrane (membrane) is layered and wound in a seaweed roll shape and housed in a container can be preferably used, but the first is not limited thereto. Further, the first reverse osmosis membrane 3 is connected to a water channel L2 that sends the primary permeated water w11 to the second reverse osmosis film and a water channel L4 that sends the primary concentrated water w12 to the fluorine removing means 11.

Since the fluorine in the waste water w1 is concentrated in the primary concentrated water w12 by the first reverse osmosis membrane 3, the volume of the target water to be treated by the fluorine removing means 11 is reduced. As a result, the scale of the fluorine removing means 11 can be reduced, and the processing capacity required for the fluorine removing means 11 is reduced.

The second pretreatment means 4 adjusts the pH of the primary permeated water w11 flowing through the water channel L2 to the range of 5 to 9, and adds a slime inhibitor Slm. As the second pretreatment means 4, for example, those provided with a secondary pH adjusting unit 4a and a secondary drug injection unit 4b can be exemplified. The secondary pH adjusting unit 4a adjusts the pH of the primary permeated water w11 in the range of 5 to 9 with sulfuric acid or the like. Further, the secondary agent injection unit 4b adds the slime inhibitor Slm to the primary permeated water w11 after adjusting the pH.

The second reverse osmosis membrane 5 separates the primary permeated water w11 to which the pH adjustment and slime inhibitor Slm is added into the secondary permeated water w21 and the secondary concentrated water w22. Ammonium is mainly removed from the primary permeated water w11 by passing through the second reverse osmosis membrane 5, to obtain the secondary permeated water w21. The removed ammonium and the like are contained in the secondary concentrated water w22. The second reverse osmosis membrane 5 may be operated, for example, in a state where the recovery rate is adjusted so that the total amount of nitrogen in the secondary concentrated water w22 is equal to or less than the emission standard.

As the second reverse osmosis membrane 5, a spiral type module in which osmosis membranes (membranes) are stacked in multiple layers and wrapped in a seaweed roll can be preferably used, but the second reverse osmosis membrane 5 is not limited thereto. Further, the second reverse osmosis membrane 5 is connected to a water channel L3 that sends the secondary permeated water w21 to the first water tank 6 and a water channel L6 that sends the secondary concentrated water w22 to the neutralization treatment means 41.

The amount of Ca in the secondary permeated water w21 is preferably less than 1 mg / L.

The first water tank 6 stores the secondary permeated water w21 sent from the second reverse osmosis membrane 5 via the water channel L3. A water channel L11 for supplying the secondary permeated water w21 to another use point 32 is connected to the first water tank 6.

The second water tank 7 stores the secondary permeated water w21 sent from the first water tank 6 via the water channel L7. Further, the second water tank 7 is connected to the water channel L9, and Ca-free water w4 sent from the calcium removing means 21 via the water channel L9 can also be stored. Further, a water channel L10 for supplying the secondary permeated water w21 and Ca-free water w4 to the use point 31 is connected to the second water tank 7.

The fluorine removing means 11 is for removing fluorine contained in the primary concentrated water w12. As the fluorine removing means 11, for example, an equipment in which the pH of the primary concentrated water w12 is adjusted to 8 or more and calcium is added to convert fluorine into CaF ₂ and the CaF ₂ is coagulated and separated can be exemplified. Further, the fluorine removing means 11 is connected to a water channel L5 that sends the treated water w40 treated by the fluorine removing means 11 to the neutralizing treatment means 41.

Next, the raw water supply unit 20, the calcium removing means 21, and the control unit 22 will be described.
The raw water supply unit 20 is a source of raw water w3 composed of clean water or industrial water. The raw water supply unit 20 supplies the raw water w3 to the calcium removing means 21 via the water channel L8.

The calcium removing means 21 removes calcium contained in the raw water w3 to obtain Ca-free water w4. Specifically, a reverse osmosis membrane or a deionizing device can be used as the calcium removing means 21. Further, the calcium removing means 21 is connected to a water channel L9 for sending the Ca-free water w4 to the second water tank 7. When the calcium removing means 21 is a reverse osmosis membrane, the permeated water is sent to the second water tank 7 as Ca-free water w4, and the concentrated water is sent to the neutralization treatment means 41 via the water channel L12. When the calcium removing means 21 is a deionizing device, the water channel L12 becomes unnecessary, and the Ca-free water w4 after the deionizing treatment is sent to the second water tank 7.

The calcium removing means 21 is preferably capable of reducing the amount of Ca in Ca-free water w4 to less than 1 mg / L. That is, Ca-free water w4 refers to water in which the amount of Ca is reduced to less than 1 mg / L.

When the supply amount of the secondary permeated water w21 is less than the demand amount of the use point 31, the control unit 22 supplies the Ca-free water w4 produced by the calcium removing means 21 to the second water tank 7. The control unit 22 monitors the amount of water stored in the second water tank 7 and the amount of water used in the use point 31. Then, based on these monitoring results, a command is issued to the calcium removing means 21 and the raw water supply unit 20 to produce Ca-free water w4, which is supplied to the second water tank 7.

Specifically, as the control unit 22, for example, a data input unit that receives the amount of water stored in the second water tank 7 and the amount of water used in the use point 31, a central processing unit, a memory device, and monitoring results of the raw water supply unit 20 and calcium. A computer provided with a data output unit for outputting to the removing means 21 and a display unit can be used. A computer program for operating the control unit 22 may be held in the memory device, and the computer program may be executed by the central processing unit. Further, the second water tank 7, the use point 31, the calcium removing means 21, the raw water supply unit 20, and the control unit 22 may be connected by a wired line or a wireless line.

The neutralization treatment means 41 stores the treated water w40 treated by the fluorine removing means 11, the secondary concentrated water w22 sent from the second reverse osmosis membrane 5, and the like, and adjusts the pH of the stored water to 6 to 8. It is a facility that adjusts to neutrality. The treated water w41 neutralized by the neutralizing means 41 can be discharged into a sewer or a public water area.

The use point 31 is a facility or facility in which the secondary permeated water w21 or Ca-free water w4 can be used as facility water. As an example of such equipment, an exhaust gas cleaning equipment from a semiconductor manufacturing process (hereinafter, simply referred to as “exhaust gas cleaning equipment”), a cooling tower, and the like can be exemplified. It is preferable that the secondary permeated water w21 used at the use point 31 is treated again by the water treatment device 1 as a part of the wastewater w1. Therefore, a water channel for sending the wastewater from the use point 31 may be provided in front of the hydrogen peroxide removing means 51 or before the first pretreatment means 2 from the use point 31.

Another use point 32 is a facility or facility that uses the secondary permeated water w21. As such a use point 32, for example, a pure water production apparatus in which the secondary permeated water w21 can be used as raw water for pure water production can be exemplified.

The water treatment device 1 of the present embodiment mainly supplies the secondary permeated water w21 to the use point 31. If there is a surplus in the secondary permeated water w21, the secondary permeated water w21 may be supplied to another use point 32. Therefore, the water treatment device 1 may be provided with a supply control unit that adjusts the supply destination of the secondary permeated water w21 or the Ca-free water w4. For example, the supply control unit monitors the amount of water stored in the first water tank 6 and the second water tank 7, and also monitors the amount of water used at each of the use points 31 and 32, and based on these monitoring results, in the waterways L10 and L11. Those that control the amount of water flow are preferable. The control unit 22 may be provided with the function of the supply control unit.

Next, the water treatment method of the present embodiment will be described with reference to FIG. In the water treatment method of the present embodiment, a first pretreatment step is performed on the wastewater w1, followed by a first reverse osmosis membrane separation step on the wastewater w1, a second pretreatment step on the primary permeated water w11, and a first. The reverse osmosis membrane separation step 2 is sequentially performed. Further, in the water treatment method of the present embodiment, a fluorine removing step may be performed on the primary concentrated water w12. Further, the water treatment method of the present embodiment includes a step of supplying Ca-free water w4 to the use point 31 when the amount of the secondary permeated water w21 is less than the demand amount at the use point 31 of the secondary permeated water w21. You may go. Hereinafter, each step will be described.

First, when the waste water w1 contains hydrogen peroxide, the hydrogen peroxide removing means 51 removes the hydrogen peroxide from the waste water w1. When the waste water w1 does not contain hydrogen peroxide, the treatment in the hydrogen peroxide removing means 51 may be omitted.

Next, in the first pretreatment step, the pH of the wastewater w1 is adjusted in the range of 9 to 11 by the primary pH adjusting unit 2a, and the scale dispersant Sc is added to the wastewater w1. By adjusting the pH of the waste water w1 to the range of 9 to 11, blockage of the first reverse osmosis membrane 3 due to organic substances contained in the waste water w1 is prevented. That is, if the wastewater w1 remains neutral, microorganisms that decompose organic matter may propagate, and the organic matter and microorganisms may block the first reverse osmosis membrane 3. Therefore, the pH is raised to suppress the growth of microorganisms. .. When the pH is low, it becomes difficult to suppress the growth of microorganisms. Further, if the pH is too high, a metal hydroxide or a metal oxide may precipitate in the waste water w1 to block the first reverse osmosis film 3, so that the pH of the waste water w1 is set in the first pretreatment step. To the range of 9-11.

Further, in the first pretreatment step, the scale dispersant Sc is added to the wastewater w1 after adjusting the pH. As a result, scale formation due to the calcium metal contained in the wastewater w1 is suppressed, and clogging of the first reverse osmosis membrane 3 is suppressed, so that a decrease in the amount of the primary permeated water w11 is prevented. As the scale dispersant Sc, for example, a chelating agent such as ethylenediaminetetraacetic acid salt, a polymer dispersant such as polymaleic acid, or a mixture thereof can be preferably used.

Next, in the first reverse osmosis membrane separation step, the wastewater w1 is separated into the primary permeated water w11 and the primary concentrated water w12 by the first reverse osmosis membrane 3. Fluorine is removed from the wastewater w1 by the first reverse osmosis membrane 3, and phosphate, calcium and organic substances are also removed to obtain primary permeated water w11. The removed fluorine and the like are contained in the primary concentrated water w12. The primary permeated water w11 is sent to the water channel L2, and the primary concentrated water w12 is sent to the fluorine removing means 11 via the water channel L4.

By the first reverse osmosis membrane separation step, the fluorine in the waste water w1 is concentrated in the primary concentrated water w12, and the volume of the target water to be treated in the fluorine removal step is reduced. This makes it possible to suppress the energy to be input when performing the fluorine removing step.

Next, in the second pretreatment step, the pH of the primary permeated water w11 is adjusted to the range of 5 to 9 by the secondary pH adjusting unit 4a, and the slime inhibitor Slm is added to the primary permeated water w11. By adjusting the pH of the primary permeated water w11 to the range of 5 to 9, the ammonia remaining in the primary permeated water w11 is changed to ammonium, thereby preventing the scattering of ammonia gas. That is, since the pH of the wastewater w1 was raised in the first pretreatment step, ammonium in the wastewater w1 may change to ammonia and scatter as ammonia gas. Therefore, primary permeation after the first reverse osmosis membrane separation step. Ammonia is changed to ammonium by lowering the pH of water w11. If the pH is low, slime may be generated and block the second reverse osmosis membrane 5, and if the pH is too high, ammonia may remain. Therefore, in the second pretreatment step, the pH of the primary permeated water w11 is adjusted to the range of 5-9.

Further, in the second pretreatment step, the slime inhibitor Slm is added to the pH-adjusted primary permeated water w11. As a result, by suppressing the formation of slime derived from organic substances and microorganisms remaining in the primary permeated water w11, clogging of the second reverse osmosis membrane 5 is suppressed, and the amount of water in the secondary permeated water w21 is reduced. To prevent. Examples of the slime inhibitor Slm include stabilized halogens such as chlorosulfamate and other halogens such as chlorine and bromine, 5-chloro-2-methyl-4-isothiazolin-3-one, and 2-methyl-. Isothiazolone compounds such as 4-isothiazolin-3-one and halocyanoacetamide compounds such as 2,2-dibromo-3-nitrilopropionamide are preferable.

Next, in the second reverse osmosis membrane separation step, the primary permeated water w11 is separated into the secondary permeated water w21 and the secondary concentrated water w22 by the second reverse osmosis membrane 5. Ammonium is removed from the primary permeated water w11 by the second reverse osmosis membrane 5, and phosphate, calcium and organic substances are also removed to obtain the secondary permeated water w21. The removed ammonium and the like are contained in the secondary concentrated water w22. The secondary permeated water w21 is sent to the first water tank 6 by the water channel L3, and the secondary concentrated water w22 is sent to the neutralization treatment means 41 by the water channel L6.

The amount of Ca in the secondary permeated water w21 is preferably less than 1 mg / L.

The secondary permeated water w21 sent to the first water tank 6 is stored in the first water tank 6 and then sent to the second water tank 7. Then, it is sent from the second water tank 7 to the use point 31 and used as equipment water. When the use point 31 is an exhaust gas cleaning facility, the secondary permeated water w21 is discharged as drainage after being used as scrubber water in the exhaust gas cleaning facility. The wastewater discharged from the exhaust gas cleaning facility is sent to the water treatment device 1 together with other wastewater discharged from the semiconductor manufacturing process, and is again used in the water treatment method of the present embodiment.

Further, when the amount of secondary permeated water w21 produced exceeds the amount of water demand at use point 31, the secondary permeated water w21 becomes surplus, so the surplus secondary permeated water w21 is used in the first water tank 6. May be supplied to another use point 32. This control may be controlled by the supply control unit described above. When the use point 31 is a pure water production apparatus, the secondary permeated water w21 is made pure water by the pure water production apparatus. Pure water is discharged as wastewater after being used, for example, in a semiconductor manufacturing process. The wastewater discharged from the semiconductor manufacturing process is sent to the water treatment apparatus 1 and again used for the water treatment method of the present embodiment.

Next, the fluorine removing step will be described.
The primary concentrated water w12 produced in the first reverse osmosis membrane separation step is sent to the fluorine removing means 11 via the water channel L4 and is used in the fluorine removing step. In the fluorine removing step, fluorine is removed from the primary concentrated water w12. As the fluorine removing step, for example, a step of adjusting the pH of the primary concentrated water w12 to 8 or more and then adding calcium to convert fluorine into CaF ₂ and coagulating and separating the CaF ₂ can be exemplified. The treated water w40 after the fluorine removing step is sent to the neutralization treatment means 41 by the water channel L5, and the neutralization step is performed.

In the neutralization step, the treated water w40, the secondary concentrated water w22 sent from the second reverse osmosis membrane 5, and the like are collected, the pH is adjusted to 6 to 8 neutral, and then the water is treated outside the water treatment device 1. Release. It may be discharged into sewers or public water bodies.

Next, a step of supplying Ca-free water w4 to the use point 31 will be described.
In the water treatment method of the present embodiment, when the supply amount of the secondary permeated water w21 to the use point 31 is less than the demand amount of the use point 31, Ca-free water w4 is produced and supplied to the use point 31. More specifically, the control unit 22 monitors the amount of water stored in the second water tank 7 and the amount of water used in the use point 31. Then, when the water storage amount in the second water tank 7 continues to decrease due to the water supply to the use point 31, it is determined that the supply amount of the secondary permeated water w21 is less than the demand amount of the use point 31, and the control unit 22 Issue a command to the raw water supply unit 20 and the calcium removing means 21.

The raw water supply unit 20 supplies the raw water w3 composed of clean water or industrial water to the calcium removing means 21. The calcium removing means 21 removes calcium contained in the raw water w3 to obtain Ca-free water w4, and then supplies the calcium to the second water tank 7. Then, the secondary permeated water w21 and Ca-free water w4 stored in the second water tank 7 are sent to the use point 31. When the secondary permeated water w21 of the second water tank 7 is small, only Ca-free water w4 may be sent to the use point 31. The amount of Ca in the Ca-free water w4 is preferably less than 1 mg / L.

As described above, in the water treatment apparatus 1 of the present embodiment, the wastewater w1 to which the pH adjustment and the scale dispersant has been added is flowed through the first reverse osmosis membrane 3 by the first pretreatment means 2. Fluorine can be removed without causing clogging in the reverse osmosis membrane 3 of 1. In addition, ammonium can be removed by flowing the primary permeated water w11 to which the pH adjustment and the slime inhibitor have been added by the second pretreatment means 4 through the second reverse osmosis membrane 5. As a result, it is possible to obtain secondary permeated water that can be used as raw water for pure water production equipment and water for equipment. Further, in the water treatment device 1 of the present embodiment, it is not necessary to install a large-scale water softener because it is not necessary to add Ca when removing fluorine from the waste water w1. Further, in the water treatment apparatus 1 of the present embodiment, since ammonium is removed by the second reverse osmosis membrane 5 after adjusting the pH, ammonium can be removed without vaporizing ammonium into ammonia. Further, according to the water treatment apparatus 1 of the present embodiment, even wastewater containing organic substances can be treated without performing biological treatment such as the activated sludge method.

Further, the water treatment apparatus 1 of the present embodiment is provided with a fluorine removing means 11 for removing fluorine in the primary concentrated water w12, and the fluorine removing means 11 is a primary concentrated water having a smaller amount of water than the wastewater w1. Fluorine in w12 may be removed, and the treatment capacity required for the fluorine removing means 11 becomes relatively small, and the water treatment device 1 can be made smaller.

Further, in the water treatment device 1 of the present embodiment, when the amount of water in the secondary permeated water w21 is less than the demand amount of the use point 31, Ca-free water w4 produced by the calcium removing means 21 is introduced into the second water tank 7. A control unit 22 for supplying water is provided, and when the secondary permeated water w21 is insufficient with respect to the demand amount, Ca-free water w4 can be replenished in the water treatment device 1. As a result, when the water circulation system is configured by the water treatment device 1 and the use point 31, the Ca concentration of the water flowing in the water circulation system can be suppressed to a low level, for example, less than 1 mg / L, and scale generation can be prevented. Therefore, it is possible to prevent clogging of the reverse osmosis membranes 3 and 5 of the water treatment apparatus 1 and generation of scale at the use point 31.

Next, according to the water treatment method of the present embodiment, the wastewater to which the pH adjustment and the scale dispersant has been added is flowed through the first reverse osmosis membrane 3 by the first pretreatment means 2, thereby causing the first reverse. Fluorine can be removed without causing clogging in the osmosis membrane 3. In addition, ammonium can be removed by flowing the primary permeated water w11 to which the pH adjustment and the slime inhibitor have been added by the first pretreatment means 2 through the second reverse osmosis membrane 5. As a result, it is possible to obtain the secondary permeated water w21 that can be used as raw water for the pure water production apparatus or water for equipment. Further, in the water treatment method of the present embodiment, it is not necessary to install a large-scale water softener because it is not necessary to add Ca when removing fluorine from the waste water w1. Further, in the water treatment method of the present embodiment, since ammonium is removed by the second reverse osmosis membrane 5 after adjusting the pH, ammonium can be removed without vaporizing ammonium into ammonia. Further, according to the water treatment method of the present embodiment, even wastewater containing organic substances can be treated without performing biological treatment such as the activated sludge method.

Further, in the water treatment method of the present embodiment, a fluorine removing step of removing fluorine in the primary concentrated water w22 is performed, and the fluorine removing step removes fluorine in the primary concentrated water w12 having a smaller amount of water than the wastewater w1. As a result, the treatment capacity required for removing fluorine is relatively small, and the energy required for water treatment can be reduced.

Further, according to the water treatment method of the present embodiment, when the amount of the secondary permeated water w21 is less than the demand amount of the use point 31, the Ca-free water w4 produced by the calcium removing means 21 is used as the use point 31. By supplying the water, Ca-free water w4 can be replenished when the secondary permeated water w21 is insufficient with respect to the demand amount. As a result, the Ca concentration of the water circulating in the water circulation system composed of the water treatment device 1 and the use point 31 can be suppressed to a low level, for example, less than 1 mg / L, scale generation is prevented, and the water treatment device is used. It is possible to prevent clogging of the reverse osmosis membranes 3 and 5 of 1 and scale generation at the use point 31.

Further, according to the water treatment method of the present embodiment, since the wastewater w1 contains the water used at the use point 31, the water circulated in the water circulation system composed of the water treatment device 1 and the use point 31. Ca concentration can be suppressed to a low level, for example, less than 1 mg / L, scale generation can be prevented, clogging of the reverse osmosis membranes 3 and 5 of the water treatment device 1 and scale generation at the use point 31 can be prevented.

1 ... Water treatment device, 2 ... First pretreatment means, 2a ... Primary pH adjusting section, 2b ... Primary drug injection section, 3 ... First reverse osmosis membrane, 4 ... Second pretreatment means, 4a ... secondary pH adjusting unit, 4b ... secondary drug injection unit, 5 ... second reverse osmosis membrane, 6 ... first water tank, 7 ... second water tank (water tank), 11 ... fluorine removing means, 20 ... raw water supply unit , 21 ... Calcium removing means, 22 ... Control unit, 31 ... Use point, 32 ... Another use point, 41 ... Neutralization means, Sc ... Scale dispersant, Slm ... Slime inhibitor, w1 ... Wastewater, w3 ... Raw water , W4 ... Ca-free water, w5 ... Ca concentrated water, w11 ... primary permeated water, w12 ... primary concentrated water, w21 ... secondary permeated water, w22 ... secondary concentrated water, w40, w41 ... treated water.

[4] The first pretreatment step of adjusting the pH to the range of 9 to 11 and adding a scale dispersant to the wastewater containing fluorine and ammonium by the first pretreatment means.
A first reverse osmosis membrane separation step of separating the wastewater after the first pretreatment step into primary permeated water and primary concentrated water by a first reverse osmosis membrane.
With respect to the primary permeated water after the first reverse osmosis membrane separation step, a second pretreatment step of adjusting the pH to a range of 5 to 9 and adding a slime inhibitor by a second pretreatment means. ,
A second reverse osmosis membrane separation step of separating the primary permeated water after the second pretreatment step into secondary permeated water and secondary concentrated water by a second reverse osmosis membrane is sequentially performed. A water treatment method characterized by.
[5] The water treatment method according to [4], wherein the fluorine removing step of removing fluorine in the primary concentrated water is further performed by a fluorine removing means.
[6] When the amount of the secondary permeated water is less than the demand for the use point of the secondary permeated water,
Ca-free water is produced by removing at least calcium in the raw water by a calcium removing means.
The water treatment method according to [4] or [5], wherein the step of supplying the Ca-free water to the use point is further performed.
[7] The water treatment method according to [6], wherein the wastewater contains the water used at the use point.

Claims (7)

For wastewater containing fluorine and ammonium, a first pretreatment means for adjusting the pH to the range of 9 to 11 and adding a scale dispersant, and
A first reverse osmosis membrane, which is installed after the first pretreatment means and separates the wastewater into primary permeated water and primary concentrated water.
With respect to the primary permeated water that has permeated the first reverse osmosis membrane, a second pretreatment means for adjusting the pH in the range of 5 to 9 and adding a slime inhibitor, and
It is characterized by being provided after the second pretreatment means and provided with a second reverse osmosis membrane that separates the primary permeated water into secondary permeated water and secondary concentrated water. Water treatment equipment. The water treatment apparatus according to claim 1, further comprising a fluorine removing means for removing fluorine in the primary concentrated water. A water tank that stores the secondary permeated water to supply the secondary permeated water to the point of use, and
Calcium removing means for producing Ca-free water by removing at least calcium in raw water,
A control unit for supplying the Ca-free water produced by the calcium removing means to the water tank when the amount of the secondary permeated water is less than the demand amount of the use point is further provided. The water treatment apparatus according to claim 1 or 2. For wastewater containing fluorine and ammonium, the first pretreatment step of adjusting the pH to the range of 9 to 11 and adding a scale dispersant by the first pretreatment means, and the first pretreatment step.
A first reverse osmosis membrane separation step of separating the wastewater after the first pretreatment step into primary permeated water and primary concentrated water by a first reverse osmosis membrane.
A second pretreatment step of adjusting the pH to the range of 5 to 9 and adding a slime inhibitor to the primary permeated water after the first reverse osmosis separation step by a second pretreatment means.
A second reverse osmosis membrane separation step of separating the primary permeated water after the second pretreatment step into secondary permeated water and secondary concentrated water by a second reverse osmosis membrane is sequentially performed. A water treatment method characterized by. The water treatment method according to claim 4, wherein the fluorine removing step of removing fluorine in the primary concentrated water is further performed by the fluorine removing means. When the amount of the secondary permeated water is less than the demand for the use point of the secondary permeated water,
Ca-free water is produced by removing at least calcium in the raw water by a calcium removing means.
The water treatment method according to claim 4 or 5, wherein the step of supplying the Ca-free water to the use point is further performed. The water treatment method according to any one of claims 4 to 6, wherein the wastewater contains the water used in the use point.

Images