Water treatment device and water treatment method

Abstract

Provided are a water treatment device and a water treatment method making it possible to stably obtain highly-concentrated ammonium sulfate solution from ammonia-containing water. A water treatment device (1) comprises: a gas-liquid separation device (12), which is a distilling means for separating ammonia out of ammonia-containing water and causing sulfuric acid to absorb the separated ammonia, thus obtaining an ammonium sulfate solution; a pressurizing pump (26), which is a pressurizing means for pressurizing the ammonium sulfate solution; and a semipermeable membrane treatment device (5), which is a semipermeable membrane treating means for using a semipermeable membrane module (18) comprising a first space (30) and a second space (32) that are partitioned by a semipermeable membrane (34) to flush the ammonium sulfate solution into the first space (30), pressurizing the first space (30), and causing the water contained in the ammonium sulfate solution to permeate through the semipermeable membrane (34), thereby obtaining semipermeable membrane-concentrated water, and also to flush some of the ammonium sulfate solution or at least some of the semipermeable membrane-concentrated water into the second space (32) to obtain semipermeable membrane-diluted water.

Description

Water treatment device and water treatment method

[0001] The present invention relates to a water treatment device and a water treatment method for recovering ammonia as ammonium sulfate from ammonia-containing water.

[0002] In recent years, methods for separating ammonia from water in ammonia-containing water discharged from a factory or the like have been proposed, such as membrane separation using a gas-liquid separation membrane and stripping, as described in Patent Documents 1 and 2, for example.

[0003] Patent Document 1 describes a method in which ammonia-containing wastewater is passed through a primary side of a gas-liquid separation membrane and a sulfuric acid solution is passed through a secondary side, and the ammonia in the ammonia-containing wastewater permeates the gas-liquid separation membrane and comes into contact with the sulfuric acid solution to produce ammonium sulfate. The separation method using a gas-liquid separation membrane described in Patent Document 1 is a method in which ammonia in wastewater is separated as a gas and removed using a hydrophobic porous membrane that is permeable to ammonia, which is gas but not to liquid.

[0004] Patent Document 2 describes recovering ammonia-containing wastewater in the form of ammonia gas using a membrane distillation apparatus or a stripping apparatus and dissolving it in water. The method described in Patent Document 2 is a method of separating ammonia as a gas from water from ammonia-containing wastewater using a membrane distillation apparatus or a stripping apparatus.

[0005] In these methods for separating ammonia by distillation, ammonia gas can be absorbed into water or sulfuric acid to produce aqueous ammonia or ammonium sulfate (also called ammonium sulfate), and the ammonia in the ammonia-containing water can be recovered.

[0006] However, in these methods of separating ammonia by distillation, particularly when recovering ammonia as ammonium sulfate, if the ammonia nitrogen concentration of the ammonia-containing water is low, the ratio of the amount of water evaporated to the amount of ammonia in the ammonia-containing water becomes high, making it difficult to sufficiently increase the concentration of ammonium sulfate to be recovered. Also, in the case of separation methods using gas-liquid separation membranes, the amount of water permeating increases due to deterioration of the gas-liquid separation membrane, making it even more difficult to increase the concentration of ammonium sulfate.

[0007] Furthermore, in the method of treating ammonia by gasification, some ammonia may remain in the treated water. In particular, when treating wastewater containing a high concentration of ammonia, in order to remove ammonia from the wastewater until the concentration is sufficiently low, it is necessary to use multiple gas-liquid separation membranes, increase the number of stripping towers, or circulate the treated water for retreatment, which poses the problem of large-scale facilities. In addition, a lot of energy is required for heating.

[0008] JP 2017-159233 A Patent No. 7112196 A

[0009] An object of the present invention is to provide a water treatment apparatus and a water treatment method that can stably obtain a high-concentration ammonium sulfate solution from ammonia-containing water.

[0010] The present invention provides a water treatment device comprising: distillation means for separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution; pressurization means for pressurizing the ammonium sulfate solution; and semipermeable membrane treatment means for using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, passing the ammonium sulfate solution through the first space, pressurizing the first space by the pressurization means, and causing water contained in the ammonium sulfate solution to permeate through the semipermeable membrane to obtain semipermeable membrane concentrated water, and passing a portion of the ammonium sulfate solution or at least a portion of the semipermeable membrane concentrated water through the second space to obtain semipermeable membrane diluted water.

[0011] The present invention provides a water treatment device comprising: distillation means for separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution; pressurizing means for pressurizing the ammonium sulfate solution; and semipermeable membrane treatment means for using semipermeable membrane modules connected in multiple stages, each having a first space and a second space partitioned by a semipermeable membrane, wherein the ammonium sulfate solution is passed through the first space of the semipermeable membrane module of a first stage, the first space is pressurized by the pressurizing means, and water contained in the ammonium sulfate solution is permeated through the semipermeable membrane to obtain semipermeable membrane concentrated water, and the semipermeable membrane concentrated water is further obtained using a semipermeable membrane module of a subsequent stage or later to obtain semipermeable membrane concentrated water, and wherein the semipermeable membrane diluted water is obtained by passing a portion of the ammonium sulfate solution, at least a portion of the semipermeable membrane concentrated water, or at least a portion of the semipermeable membrane diluted water obtained from another semipermeable membrane module, through the second space of the semipermeable membrane module of each stage.

[0012] In the water treatment device, the distillation means preferably has a gas-liquid separation membrane.

[0013] In the water treatment apparatus, the ammonia-containing water is preferably wastewater discharged from a semiconductor factory.

[0014] In the water treatment device, the sulfuric acid is preferably waste sulfuric acid discharged from a semiconductor factory.

[0015] In the water treatment device, the ammonia nitrogen concentration of the ammonia-containing water is preferably in the range of 300 mg / L or more and 7000 mg / L or less.

[0016] In the water treatment device, it is preferable that the ammonium sulfate concentration of the ammonium sulfate solution passed through the semipermeable membrane treatment means is in the range of 20,000 mg / L or more and 100,000 mg / L or less, and the ammonium sulfate concentration of the semipermeable membrane concentrated water obtained by the semipermeable membrane treatment means is 25 mass% or more.

[0017] The water treatment device preferably further includes a circulation tank that stores the ammonium sulfate solution, a circulation line that returns the ammonium sulfate solution discharged from the circulation tank to the circulation tank via the distillation means, a circulation means that circulates the ammonium sulfate solution from the circulation tank to the circulation line, a pH measurement means that measures the pH of the ammonium sulfate solution, and a specific gravity measurement means that measures the specific gravity of the ammonium sulfate solution, and when the measured value of the pH measurement means exceeds a predetermined value, sulfuric acid is replenished to the circulation tank, and when the measured value of the specific gravity measurement means exceeds a predetermined range, at least a part of the ammonium sulfate solution is discharged.

[0018] The present invention is a water treatment method comprising: a distillation step of separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution; a pressurizing step of pressurizing the ammonium sulfate solution; and a semipermeable membrane treatment step of using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, passing the ammonium sulfate solution through the first space, pressurizing the first space by the pressurization in the pressurizing step, and causing water contained in the ammonium sulfate solution to permeate through the semipermeable membrane to obtain semipermeable membrane concentrated water, and passing a portion of the ammonium sulfate solution or at least a portion of the semipermeable membrane concentrated water through the second space to obtain semipermeable membrane diluted water.

[0019] The present invention is a water treatment method comprising: a distillation step of separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution; a pressurizing step of pressurizing the ammonium sulfate solution; and a semipermeable membrane treatment step of using semipermeable membrane modules connected in multiple stages, each having a first space and a second space separated by a semipermeable membrane, passing the ammonium sulfate solution through the first space of a first-stage semipermeable membrane module, pressurizing the first space by the pressurization in the pressurizing step, and causing the water contained in the ammonium sulfate solution to permeate through the semipermeable membrane to obtain semipermeable membrane concentrated water, and further using a semipermeable membrane module in a subsequent stage or later to obtain semipermeable membrane concentrated water, and passing a portion of the ammonium sulfate solution or at least a portion of the concentrated water, or at least a portion of semipermeable membrane diluted water obtained from another semipermeable membrane module, through the second space of the semipermeable membrane module in each stage to obtain semipermeable membrane diluted water.

[0020] According to the present invention, it is possible to provide a water treatment device and a water treatment method that can stably obtain a high-concentration ammonium sulfate solution from ammonia-containing wastewater.

[0021] Fig. 1 is a schematic configuration diagram showing an example of a water treatment device according to an embodiment of the present invention. Fig. 2 is a schematic configuration diagram showing another example of a water treatment device according to an embodiment of the present invention. Fig. 3 is a schematic configuration diagram showing another example of a semipermeable membrane treatment device in a water treatment device according to an embodiment of the present invention. Fig. 4 is a schematic configuration diagram showing another example of a semipermeable membrane treatment device in a water treatment device according to an embodiment of the present invention. Fig. 5 is a schematic configuration diagram showing another example of a semipermeable membrane treatment device in a water treatment device according to an embodiment of the present invention.

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present invention. The embodiment is an example of implementing the present invention, and the present invention is not limited to the embodiment.

[0023] An example of a water treatment device according to an embodiment of the present invention is outlined in Fig. 1, and its configuration will be described. The water treatment device 1 shown in Fig. 1 is a device that treats ammonia-containing water using a gas-liquid separation membrane and treats the ammonium sulfate solution treated by the gas-liquid separation membrane with a semipermeable membrane.

[0024] The water treatment device 1 includes a gas-liquid separator 12 having a gas-liquid separation membrane 28 as distillation means for separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution, a pressure pump 26 as pressurization means for pressurizing the ammonium sulfate solution, and a semipermeable membrane treatment device 5 having a semipermeable membrane module 18 as semipermeable membrane treatment means for passing the ammonium sulfate solution through the first space 30 using a semipermeable membrane module having a first space 30 and a second space 32 partitioned by a semipermeable membrane 34, pressurizing the first space 30 by the pressure applied by the pressure pump 26, thereby causing the water contained in the ammonium sulfate solution to permeate through the semipermeable membrane 34, thereby obtaining semipermeable membrane concentrated water, and passing a portion of the ammonium sulfate solution or at least a portion of the semipermeable membrane concentrated water through the second space 32.

[0025] The water treatment device 1 may include one or more of an ammonia-containing water tank 10 for storing ammonia-containing water, a circulation tank 14 for storing an ammonium sulfate solution, a semipermeable membrane treated water tank 16 for storing water to be treated in the semipermeable membrane module 18, and a semipermeable membrane diluted water tank 20 for storing semipermeable membrane diluted water obtained in the semipermeable membrane module 18. The water treatment device 1 may include a reverse osmosis membrane treatment device 22 as reverse osmosis membrane treatment means that performs reverse osmosis membrane treatment on the semipermeable membrane diluted water obtained in the semipermeable membrane module 18 to obtain reverse osmosis membrane permeate and reverse osmosis membrane concentrated water.

[0026] In the water treatment device 1 of Figure 1, an ammonia-containing water pipe 40 is connected to the inlet of the ammonia-containing water tank 10. The outlet of the ammonia-containing water tank 10 and the inlet of the primary side 36 of the gas-liquid separation device 12 are connected by an ammonia-containing water supply pipe 42. A primary-side treated water pipe 44 is connected to the outlet of the primary side 36 of the gas-liquid separation device 12. The outlet of the secondary side 38 of the gas-liquid separation device 12 and the ammonium sulfate solution inlet of the circulation tank 14 are connected by a circulation pipe 46. The ammonium sulfate solution outlet of the circulation tank 14 and the inlet of the secondary side 38 of the gas-liquid separation device 12 are connected by a circulation pipe 48. A sulfuric acid supply pipe 66 is connected to the sulfuric acid inlet of the circulation tank 14. An ammonium sulfate solution pipe 50 branched from the circulation pipe 48 is connected to the ammonium sulfate solution inlet of the semipermeable membrane treated water tank 16. The semipermeable membrane treated water outlet of the semipermeable membrane treated water tank 16 and the inlet of the first space 30 of the semipermeable membrane module 18 are connected by a semipermeable membrane treated water supply pipe 52 via a pressure pump 26. A semipermeable membrane concentrated water pipe 54 is connected to the outlet of the first space 30 of the semipermeable membrane module 18. A semipermeable membrane concentrated water pipe 56 branching from the semipermeable membrane concentrated water pipe 54 is connected to the inlet of the second space 32 of the semipermeable membrane module 18. The outlet of the second space 32 of the semipermeable membrane module 18 and the inlet of the semipermeable membrane dilution water tank 20 are connected by a semipermeable membrane dilution water pipe 58. The outlet of the semipermeable membrane dilution water tank 20 and the inlet of the reverse osmosis membrane treatment device 22 are connected by a reverse osmosis membrane treated water supply pipe 60. A reverse osmosis membrane permeate water pipe 62 is connected to the reverse osmosis membrane permeate outlet of the reverse osmosis membrane treatment device 22. The reverse osmosis membrane concentrated water outlet of the reverse osmosis membrane treatment device 22 and the reverse osmosis membrane concentrated water inlet of the semipermeable membrane treated water tank 16 are connected by a reverse osmosis membrane concentrated water pipe 64 .

[0027] In the water treatment device 1, the gas-liquid separator 12, the circulation tank 14, the sulfuric acid supply pipe 66, and the like function as a distillation means for separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution.

[0028] The pressure pump 26 is a pressure pump that is driven, for example, at a rotational speed corresponding to an input drive frequency, and sucks in the ammonium sulfate solution and pressurizes and discharges it to the semipermeable membrane module 18. The pressure pump 26 is equipped with, for example, an inverter that outputs to the pressure pump 26 a drive frequency corresponding to an input command signal.

[0029] The semipermeable membrane module 18 has a first space 30 (concentration side) and a second space 32 (permeation side) separated by a semipermeable membrane 34, and is an apparatus in which an ammonium sulfate solution is passed through the first space 30 from the first space inlet of the semipermeable membrane module 18, and at least a portion of the semipermeable membrane concentrate discharged from the first space outlet of the first space 30 of the semipermeable membrane module 18 is passed through the second space inlet of the semipermeable membrane module 18 to the second space 32, thereby pressurizing the first space 30, causing the water contained in the ammonium sulfate solution in the first space 30 to permeate into the second space 32 via the semipermeable membrane 34, thereby concentrating the water. That is, in the water treatment device 1, the ammonium sulfate solution is concentrated using the semipermeable membrane 34. The semipermeable membrane module 18 is an apparatus in which an ammonium sulfate solution is supplied to the first space 30 of the semipermeable membrane module 18, and at least a portion of the semipermeable membrane concentrate obtained from the outlet of the first space 30 is supplied to the second space 32 of the semipermeable membrane module 18, thereby performing a concentration treatment.

[0030] The water treatment method and the operation of the water treatment device 1 according to this embodiment will be described.

[0031] Ammonia-containing water containing ammonia is stored in the ammonia-containing water tank 10 as needed through the ammonia-containing water pipe 40 and supplied to the primary side 36 of the gas-liquid separation device 12 through the ammonia-containing water supply pipe 42. A supply pump for supplying ammonia-containing water to the primary side 36 of the gas-liquid separation device 12 may be provided in the ammonia-containing water supply pipe 42. Meanwhile, sulfuric acid is supplied to the circulation tank 14 through the sulfuric acid supply pipe 66, and sulfuric acid is circulated from the circulation tank 14 through the circulation pipe 48 and the circulation pipe 46 to the secondary side 38 of the gas-liquid separation device 12. In the gas-liquid separation device 12, ammonia is separated from the ammonia-containing water on the primary side 36 by passing it through the gas-liquid separation membrane 28 to the secondary side 38, and the separated ammonia is absorbed by sulfuric acid on the secondary side 38 to obtain an ammonium sulfate solution (distillation process). The obtained ammonium sulfate solution is stored in the circulation tank 14 through the circulation pipe 46 and circulated to the secondary side 38 of the gas-liquid separation device 12 through the circulation pipe 48. The gas-liquid separation membrane primary-side treated water, with a reduced amount of ammonia obtained on the primary side 36 of the gas-liquid separator 12, is discharged through primary-side treated water piping 44. A circulation pump may be provided in the circulation piping 48 to supply the sulfuric acid or ammonium sulfate solution in the circulation tank 14 to the secondary side 38 of the gas-liquid separator 12.

[0032] A portion of the ammonium sulfate solution circulated from the secondary side 38 of the gas-liquid separator 12 through the circulation pipe 46, the circulation tank 14, and the circulation pipe 48 is stored in the semipermeable membrane treated water tank 16 as needed through an ammonium sulfate solution pipe 50 branched from the circulation pipe 48, and is pressurized and fed by the pressure pump 26 through a semipermeable membrane treated water supply pipe 52 from the first space inlet of the semipermeable membrane module 18 to the first space 30, where it is passed. A portion of the water contained in the pressurized ammonium sulfate solution permeates from the first space 30 to the second space 32 through the semipermeable membrane 34. At this time, most of the ions and the like cannot permeate the semipermeable membrane 34, so the water in the first space 30 that did not permeate the semipermeable membrane 34 is concentrated. Meanwhile, in the second space 32, a portion of the semipermeable membrane concentrated water passed through the semipermeable membrane concentrated water pipes 54 and 56 and the permeate with a low ion concentration that permeated the semipermeable membrane 34 join together, resulting in a dilution effect. The semipermeable membrane concentrated water obtained in the first space 30 is discharged from the first space outlet through the semipermeable membrane concentrated water piping 54, and at least a part of the semipermeable membrane concentrated water is sent through the semipermeable membrane concentrated water piping 56 branched from the semipermeable membrane concentrated water piping 54 to the second space 32 from the second space inlet of the semipermeable membrane module 18 and passed through (semipermeable membrane treatment process).

[0033] The semipermeable membrane diluted water obtained in the second space 32 may be discharged from the second space outlet through a semipermeable membrane diluted water pipe 58, or may be stored in the semipermeable membrane diluted water tank 20 as needed and further processed, for example, sent to the reverse osmosis membrane treatment device 22 through a reverse osmosis membrane treated water supply pipe 60 for further reverse osmosis membrane treatment. When reverse osmosis membrane treatment is performed, the semipermeable membrane diluted water is treated using a reverse osmosis membrane in the reverse osmosis membrane treatment device 22, and reverse osmosis membrane permeate and reverse osmosis membrane concentrate are obtained (reverse osmosis membrane treatment step). The reverse osmosis membrane permeate obtained by the reverse osmosis membrane treatment is discharged through a reverse osmosis membrane permeate pipe 62. The discharged reverse osmosis membrane permeate may be reused as industrial water, etc. The reverse osmosis membrane concentrate may be discharged through a reverse osmosis membrane concentrate pipe 64, or may be returned through the reverse osmosis membrane concentrate pipe 64 to an upstream stage of the semipermeable membrane module 18, for example, the semipermeable membrane treated water tank 16 (return step).

[0034] In this way, gas-liquid separation membrane primary treated water with a reduced amount of ammonia and a concentrated ammonium sulfate solution (semipermeable membrane concentrated water) with a highly concentrated and reduced volume are recovered from the ammonia-containing water to be treated. The recovered gas-liquid separation membrane primary treated water and ammonium sulfate solution can be reused. Examples of reuse include industrial water for the gas-liquid separation membrane primary treated water, and raw materials for fertilizers and water treatment chemicals (nutrients for biological treatment) for the ammonium sulfate solution.

[0035] In the water treatment method and water treatment device according to this embodiment, the nitrogen load in the ammonia-containing water is reduced by separating ammonia from the ammonia-containing water, and the separated ammonia is absorbed into sulfuric acid to produce ammonium sulfate, which is then concentrated to a high concentration and reduced in volume, thereby obtaining a concentrated ammonium sulfate solution in the form of semipermeable membrane concentrated water.

[0036] The ammonia-containing water to be treated is water containing ammonia, and is not particularly limited, but examples thereof include wastewater discharged from semiconductor factories, such as scrubber wastewater from semiconductor factories and ammonia / hydrogen peroxide cleaning wastewater.

[0037] The ammonia-containing water may be subjected to activated carbon treatment or concentration treatment using a reverse osmosis membrane before distillation. By pre-concentrating the water using a reverse osmosis membrane, the amount of water supplied to the gas-liquid separation membrane can be reduced, allowing for downsizing of the equipment. Furthermore, obtaining permeate water through the reverse osmosis membrane can increase the water recovery rate of the entire equipment. However, there is a risk of increased chemical costs due to pH adjustment to maintain the treatment performance of the reverse osmosis membrane, and a decrease in the amount of ammonia recovered due to leakage of some ammonia to the permeate side of the reverse osmosis membrane. In particular, when the ammonia-containing water is alkaline, the increase in chemical costs due to pH adjustment is significant, so a reverse osmosis membrane need not be installed upstream of the distillation treatment.

[0038] The pH of the ammonia-containing water is, for example, 9 or more and 12 or less. If the pH of the ammonia-containing water is less than 9, the ammonia-containing water may be adjusted to an alkaline pH of 9 or more using a pH adjuster such as an alkali, such as an aqueous sodium hydroxide solution, as necessary. The ammonia-containing water may also be heated to, for example, 30 to 50°C and then flowed into the primary side 36 of the gas-liquid separator 12.

[0039] As the gas-liquid separation membrane, a hydrophobic porous membrane such as polypropylene that is almost impermeable to liquids but permeable to ammonia gas can be used.

[0040] The treated water on the primary side of the gas-liquid separation membrane may be discharged to the outside of the system, or may be circulated to a stage upstream of the gas-liquid separation device 12, for example, to the ammonia-containing water tank 10, and subjected to distillation again. A dispersant such as an acrylic acid-based chelating agent may be added to the ammonia-containing water to inhibit scale formation.

[0041] When the ammonia-containing water has a relatively low ammonia nitrogen concentration (e.g., 1000 mg / L or less), installing two or more gas-liquid separators 12, e.g., two to three stages, makes it possible to treat the ammonia nitrogen concentration on the primary side of the gas-liquid separator to a low concentration. The ammonia nitrogen concentration in the ammonia-containing water may be, for example, 7000 mg / L or less, preferably 300 mg / L to 7000 mg / L, and more preferably 300 mg / L to 2000 mg / L, from the viewpoint of reducing the ammonia nitrogen concentration of the treated water on the primary side of the gas-liquid separation membrane as much as possible without excessively large equipment. With the water treatment method and water treatment device according to this embodiment, even if the ammonia nitrogen concentration of the ammonia-containing water is low (e.g., 1000 mg / L or less), a high-concentration ammonium sulfate solution can be stably obtained from the ammonia-containing water.

[0042] Sulfuric acid is circulated on the secondary side 38 of the gas-liquid separator 12. The sulfuric acid may be waste sulfuric acid used for other purposes within the factory in which the water treatment device according to this embodiment is installed, such as waste sulfuric acid discharged from a semiconductor factory. The sulfuric acid concentration is, for example, in the range of 30 to 50 mass %, preferably 40 to 50 mass %, from the viewpoint of being able to sufficiently absorb ammonia.

[0043] The ammonium sulfate solution concentrated on the secondary side 38 of the gas-liquid separator 12 is sent to and stored in the semipermeable membrane treated water tank 16 at a predetermined timing (for example, when the pH, specific gravity, and concentration described below reach predetermined values).

[0044] For example, the circulation tank 14 or the circulation pipes 46, 48 may be provided with a pH measuring device 24 as a pH measuring means for measuring the pH of the sulfuric acid or ammonium sulfate solution, and the pH of the sulfuric acid or ammonium sulfate solution may be measured (pH measuring step).

[0045] Ammonia in the ammonia-containing water permeates through the gas-liquid separation membrane 28 and is absorbed by sulfuric acid, thereby gradually increasing the pH of the ammonium sulfate solution. When the pH measured by the pH measuring device 24 exceeds a predetermined pH, for example, when the pH exceeds pH 3, a portion of the ammonium sulfate is discharged through the ammonium sulfate solution pipe 50, and the pH of the ammonium sulfate solution may be adjusted, for example, to pH 3 or less, by newly supplying sulfuric acid to the ammonium sulfate solution in the circulation tank 14 through, for example, the sulfuric acid supply pipe 66 (pH adjustment step).

[0046] The circulation tank 14 or the circulation pipes 46, 48 may be provided with a specific gravity measuring device 25 as specific gravity measuring means for measuring the specific gravity of the sulfuric acid or ammonium sulfate solution, thereby measuring the specific gravity of the sulfuric acid or ammonium sulfate solution (specific gravity measuring step), or may be further provided with a concentration measuring device as concentration measuring means for measuring the concentration of sulfuric acid or ammonium sulfate in the sulfuric acid or ammonium sulfate solution, thereby measuring the concentration of sulfuric acid or ammonium sulfate (concentration measuring step).

[0047] Ammonia in the ammonia-containing water permeates through the gas-liquid separation membrane 28 and is absorbed by sulfuric acid, gradually increasing the specific gravity of the ammonium sulfate solution. If the specific gravity measured by the specific gravity measuring device 25 exceeds a predetermined specific gravity, for example, if the specific gravity exceeds 1.14 (corresponding to approximately 25% by mass of sulfuric acid), part of the ammonium sulfate is discharged through the ammonium sulfate solution pipe 50, and the specific gravity of the ammonium sulfate solution may be adjusted by newly supplying sulfuric acid to the ammonium sulfate solution in the circulation tank 14 through, for example, the sulfuric acid supply pipe 66 so that the specific gravity becomes 1.14 or less (specific gravity adjustment step).

[0048] Furthermore, the concentration of ammonium sulfate in the ammonium sulfate solution gradually increases as ammonia in the ammonia-containing water permeates through the gas-liquid separation membrane 28 and is absorbed by sulfuric acid. When the concentration of ammonium sulfate measured by the concentration measuring device exceeds a predetermined concentration, for example, when the concentration of ammonium sulfate exceeds 25% by mass, a portion of the ammonium sulfate is discharged through the ammonium sulfate solution pipe 50, and the concentration of the ammonium sulfate solution may be adjusted by newly supplying sulfuric acid to the ammonium sulfate solution in the circulation tank 14 through, for example, the sulfuric acid supply pipe 66 so that the concentration becomes 25% by mass or less (concentration adjustment step).

[0049] When controlling concentration by specific gravity, the change in specific gravity relative to concentration is smaller than with measurement methods such as conductivity, making concentration control difficult. Furthermore, there is an operational management issue of withdrawing ammonium sulfate solution at a lower concentration to prevent ammonium sulfate from reaching a saturation concentration, making it difficult to stably recover a practically suitable high-concentration ammonium sulfate solution, such as 25% by mass. For example, the specific gravity of an ammonium sulfate solution is 1.14 and the ammonium sulfate concentration is approximately 25% by mass, while the specific gravity of an ammonium sulfate solution is 1.13 and the ammonium sulfate concentration is approximately 23% by mass. Therefore, controlling the ammonium sulfate concentration in 1% by mass increments requires a precise hydrometer. However, in the water treatment method and water treatment apparatus according to this embodiment, high concentration is performed in the semipermeable membrane module 18 (semipermeable membrane treatment process) downstream of the gas-liquid separator 12 (distillation process). Therefore, even if the ammonium sulfate concentration of the ammonium sulfate solution obtained in the upstream gas-liquid separator 12 (distillation process) varies somewhat, the ammonium sulfate concentration of the finally obtained concentrated ammonium sulfate solution (semipermeable membrane concentrated water) can be adjusted.

[0050] The pH of the ammonium sulfate solution obtained in the gas-liquid separator 12 may be adjusted to, for example, a range of pH 5 to 8 using a pH adjuster such as an acid such as hydrochloric acid or sulfuric acid, or an alkali such as an aqueous sodium hydroxide solution. A dispersant such as an acrylic acid-based chelating agent and a disinfectant such as hypochlorous acid or a stabilized hypobromous acid composition containing a bromine-based oxidizing agent and a sulfamic acid compound may be added to the ammonium sulfate solution obtained in the gas-liquid separator 12.

[0051] The ammonium sulfate concentration of the ammonium sulfate solution obtained in the gas-liquid separator 12 and passed through the semipermeable membrane module 18 of the semipermeable membrane treatment device is, for example, in the range of 20,000 mg / L to 100,000 mg / L, and preferably in the range of 30,000 mg / L to 100,000 mg / L. If the ammonium sulfate concentration of the ammonium sulfate solution passed through the semipermeable membrane module 18 is less than 20,000 mg / L, the number of membranes required for concentration may increase, and if it exceeds 100,000 mg / L, the benefit of concentration using a semipermeable membrane treatment device may decrease.

[0052] In concentration using a semipermeable membrane, water is passed through and concentrated, so scale-causing substances are also concentrated, making it easy for scaling to occur. However, in the water treatment method and water treatment device according to this embodiment, scale components are hardly concentrated in the gas-liquid separator 12 that uses a gas-liquid separation membrane in the upstream stage, so there is an advantage that scale is less likely to form compared to when ammonia-containing water is directly concentrated using a semipermeable membrane.

[0053] The first space 30 side of the semipermeable membrane module 18 is pressurized, for example, to 0.1 MPa or more, preferably in the range of 1 to 7 MPa, and the permeated water moves to the second space 32. At least a portion of the semipermeable membrane concentrated water is supplied to the second space 32 of the semipermeable membrane module 18, and the remainder is discharged outside the system to be discarded or recovered. The semipermeable membrane concentrated water supplied to the second space 32 mixes with the permeated water and becomes semipermeable membrane diluted water, which is discharged from the outlet of the second space 32 of the semipermeable membrane.

[0054] Examples of the semipermeable membrane 34 included in the semipermeable membrane module 18 include a reverse osmosis membrane (RO membrane), a forward osmosis membrane (FO membrane), a nanofiltration membrane (NF membrane), etc. The semipermeable membrane is preferably a reverse osmosis membrane.

[0055] The material for forming the semipermeable membrane 34 is not particularly limited, but examples thereof include cellulose-based resins such as cellulose acetate-based resins, polysulfone-based resins such as polyethersulfone-based resins, and polyamide-based resins.

[0056] The shape of the semipermeable membrane 34 may be a flat membrane, a hollow fiber membrane, a spiral membrane, etc. A hollow fiber membrane is preferred because it allows the surface area of ​​the semipermeable membrane to be increased.

[0057] The concentration of ammonium sulfate in the semipermeable membrane concentrated water obtained in the semipermeable membrane module 18 is, for example, 25% by mass or more, and preferably in the range of 30% by mass or more and 35% by mass or less.

[0058] A membrane treatment device having a nanofiltration membrane (NF membrane) or the like for treating the semipermeable membrane diluted water may be provided instead of the reverse osmosis membrane treatment device 22, or at a stage preceding the reverse osmosis membrane treatment device 22. The semipermeable membrane diluted water discharged from the semipermeable membrane module 18 may be stored in the semipermeable membrane diluted water tank 20 as necessary and supplied to the reverse osmosis membrane treatment device 22 or a membrane treatment device having a nanofiltration membrane (NF membrane) or the like to obtain clear reverse osmosis membrane permeate or NF membrane permeate, and the reverse osmosis membrane concentrated water may be returned to a stage preceding the semipermeable membrane module 18 (semipermeable membrane treatment step).

[0059] Another example of a water treatment device according to an embodiment of the present invention is outlined in Fig. 2, and its configuration will be described. The water treatment device 3 shown in Fig. 2 is a device that treats ammonia-containing water by a stripping method using a stripping tower and treats the ammonium sulfate solution treated by the stripping method using a semipermeable membrane.

[0060] The water treatment device 3 includes a stripper column 70 as distillation means for separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution, a pressure pump 26 as pressurizing means for pressurizing the ammonium sulfate solution, and a semipermeable membrane treatment device 5 having a semipermeable membrane module 18 as semipermeable membrane treatment means for passing the ammonium sulfate solution through the first space 30 using a semipermeable membrane module having a first space 30 and a second space 32 partitioned by a semipermeable membrane 34, and pressurizing the first space 30 by the pressure applied by the pressure pump 26 to cause water contained in the ammonium sulfate solution to permeate through the semipermeable membrane 34, thereby obtaining semipermeable membrane concentrated water, and for passing a part of the ammonium sulfate solution or at least a part of the semipermeable membrane concentrated water through the second space 32.

[0061] In order to recover heat, the water treatment device 3 may include a vapor compression device 72, a reboiler 74, and a gas-liquid separation tank 76 as compression means for compressing the treatment gas from the stripper tower 70.

[0062] The water treatment device 3 may include one or two of an ammonia-containing water tank 10 for storing ammonia-containing water, a semipermeable membrane treated water tank 16 for storing water to be treated from the semipermeable membrane module 18, and a semipermeable membrane diluted water tank 20 for storing semipermeable membrane diluted water obtained in the semipermeable membrane module 18. The water treatment device 3 may include a reverse osmosis membrane treatment device 22 as reverse osmosis membrane treatment means that performs reverse osmosis membrane treatment on the semipermeable membrane diluted water obtained in the semipermeable membrane module 18 to obtain reverse osmosis membrane permeate and reverse osmosis membrane concentrated water.

[0063] In the water treatment apparatus 3 of Figure 2, the ammonia-containing water pipe 40 is connected to the inlet of the ammonia-containing water tank 10. The outlet of the ammonia-containing water tank 10 and the inlet of the stripper tower 70 are connected by an ammonia-containing water supply pipe 80. The treated gas outlet of the stripper tower 70 and the treated gas inlet of the vapor compression device 72 are connected by a treated gas pipe 82. The treated gas outlet of the vapor compression device 72 and the treated gas inlet of the reboiler 74 are connected by a treated gas pipe 84. The treated gas outlet of the reboiler 74 and the treated gas inlet of the gas-liquid separation tank 76 are connected by a treated gas pipe 92. The treated water outlet of the reboiler 74 and the treated water inlet of the stripper tower 70 are connected by a treated water pipe 86. The separated liquid outlet of the gas-liquid separation tank 76 and the ammonia-containing water supply pipe 80 are connected by a separated liquid pipe 94. The separated gas outlet of the gas-liquid separation tank 76 and the separated gas inlet of the semipermeable membrane treated water tank 16 are connected by a separated gas pipe 96. The stripper tower treated water outlet of the stripper tower 70 and the stripper tower treated water inlet of the reboiler 74 are connected by a stripper tower treated water pipe 88. A stripper tower treated water pipe 90 branches off from the stripper tower treated water pipe 88.

[0064] A sulfuric acid supply pipe 67 is connected to the sulfuric acid inlet of the semipermeable membrane treatment water tank 16. The semipermeable membrane treatment water outlet of the semipermeable membrane treatment water tank 16 and the inlet of the first space 30 of the semipermeable membrane module 18 are connected by a semipermeable membrane treatment water supply pipe 52 via a pressure pump 26. A semipermeable membrane concentrate pipe 54 is connected to the outlet of the first space 30 of the semipermeable membrane module 18. A semipermeable membrane concentrate pipe 56 branched from the semipermeable membrane concentrate pipe 54 is connected to the inlet of the second space 32 of the semipermeable membrane module 18. The outlet of the second space 32 of the semipermeable membrane module 18 and the inlet of the semipermeable membrane dilution water tank 20 are connected by a semipermeable membrane dilution water pipe 58. The outlet of the semipermeable membrane dilution water tank 20 and the inlet of the reverse osmosis membrane treatment device 22 are connected by a reverse osmosis membrane treatment water supply pipe 60. A reverse osmosis membrane permeate pipe 62 is connected to the reverse osmosis membrane permeate outlet of the reverse osmosis membrane treatment device 22. The reverse osmosis membrane concentrated water outlet of the reverse osmosis membrane treatment device 22 and the reverse osmosis membrane concentrated water inlet of the semipermeable membrane treated water tank 16 are connected by a reverse osmosis membrane concentrated water pipe 64 .

[0065] In the water treatment device 3, the stripper tower 70, the gas-liquid separation tank 76, the semipermeable membrane treated water tank 16, the sulfuric acid supply pipe 67, and the like function as distillation means for separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution.

[0066] The pressure pump 26 is a pressure pump that is driven, for example, at a rotational speed corresponding to an input drive frequency, and sucks in the ammonium sulfate solution and pressurizes and discharges it to the semipermeable membrane module 18. The pressure pump 26 is equipped with, for example, an inverter that outputs to the pressure pump 26 a drive frequency corresponding to an input command signal.

[0067] The semipermeable membrane module 18 has a first space 30 and a second space 32 separated by a semipermeable membrane 34, and is an apparatus in which an ammonium sulfate solution is passed through the first space 30 from the first space inlet of the semipermeable membrane module 18, and at least a portion of the semipermeable membrane concentrated water discharged from the first space outlet of the first space 30 of the semipermeable membrane module 18 is passed through the second space inlet of the semipermeable membrane module 18 to the second space 32, and the first space 30 is pressurized, thereby causing the water contained in the ammonium sulfate solution in the first space 30 to permeate into the second space 32 via the semipermeable membrane 34, thereby concentrating the water. That is, in the water treatment device 1, the ammonium sulfate solution is concentrated using the semipermeable membrane 34. The semipermeable membrane module 18 is an apparatus in which an ammonium sulfate solution is supplied to the first space 30 of the semipermeable membrane module 18, and at least a portion of the semipermeable membrane concentrated water obtained from the outlet of the first space 30 is supplied to the second space 32 of the semipermeable membrane module 18, thereby performing a concentration treatment.

[0068] The water treatment method and the operation of the water treatment device 3 according to this embodiment will be described.

[0069] Ammonia-containing water containing ammonia is stored in the ammonia-containing water tank 10 as needed through the ammonia-containing water piping 40 and supplied to the stripper tower 70 through the ammonia-containing water supply piping 80. A supply pump for supplying the ammonia-containing water to the stripper tower 70 may be provided on the ammonia-containing water supply piping 80. In the stripper tower 70, steam or air is blown into the ammonia-containing water by a stripping method to react ammonium ions with hydroxide ions, thereby separating the ammonia-containing water into a treated gas containing ammonia gas and stripper tower treated water (distillation process). The treated gas obtained in the stripper tower 70 is sent to the vapor compression device 72 through a treated gas piping 82, and after being compressed by the vapor compression device 72, is sent to the reboiler 74 through a treated gas piping 84. The stripper tower treated water obtained in the stripper tower 70 is sent to the reboiler 74 through a stripper tower treated water piping 88. A portion of the stripper-tower-treated water obtained in the stripper tower 70 is discharged through a stripper-tower-treated water pipe 90 branching off from a stripper-tower-treated water pipe 88. Heat exchange occurs in the reboiler 74, and the treated gas is sent through a treated gas pipe 92 to the gas-liquid separation tank 76, where gas-liquid separation occurs. The separated separated gas is sent through a separated gas pipe 96 to the semipermeable membrane-treated water tank 16. The separated separated liquid is returned to the stripper tower 70 through a separated liquid pipe 94 and an ammonia-containing water supply pipe 80. The treated water obtained in the reboiler 74 is sent to the stripper tower 70 through a treated water pipe 86.

[0070] Sulfuric acid is supplied to the semipermeable membrane treated water tank 16 through the sulfuric acid supply pipe 67, and ammonia in the separated gas is absorbed by the sulfuric acid to produce an ammonium sulfate solution. The ammonium sulfate solution is pressurized and pumped from the semipermeable membrane treated water tank 16 by the pressure pump 26 through the semipermeable membrane treated water supply pipe 52 and from the first space inlet of the semipermeable membrane module 18 to the first space 30, where it is passed. A portion of the water contained in the pressurized ammonium sulfate solution permeates from the first space 30 to the second space 32 through the semipermeable membrane 34. At this time, most of the ions and the like cannot permeate the semipermeable membrane 34, so the water in the first space 30 that did not permeate the semipermeable membrane 34 is concentrated. Meanwhile, in the second space 32, a portion of the semipermeable membrane concentrated water passed through the semipermeable membrane concentrated water pipes 54, 56 and the permeate with a low ion concentration that permeated the semipermeable membrane 34 join together, resulting in a dilution effect. The semipermeable membrane concentrated water obtained in the first space 30 is discharged from the first space outlet through the semipermeable membrane concentrated water piping 54, and at least a part of the semipermeable membrane concentrated water is sent through the semipermeable membrane concentrated water piping 56 branched from the semipermeable membrane concentrated water piping 54 to the second space 32 from the second space inlet of the semipermeable membrane module 18 and passed through (semipermeable membrane treatment process).

[0071] The semipermeable membrane diluted water obtained in the second space 32 may be discharged from the second space outlet through a semipermeable membrane diluted water pipe 58, or may be stored in the semipermeable membrane diluted water tank 20 as needed and further processed, for example, sent to the reverse osmosis membrane treatment device 22 through a reverse osmosis membrane treated water supply pipe 60 for further reverse osmosis membrane treatment. When reverse osmosis membrane treatment is performed, the semipermeable membrane diluted water is treated using a reverse osmosis membrane in the reverse osmosis membrane treatment device 22, and reverse osmosis membrane permeate and reverse osmosis membrane concentrate are obtained (reverse osmosis membrane treatment step). The reverse osmosis membrane permeate obtained by the reverse osmosis membrane treatment is discharged through a reverse osmosis membrane permeate pipe 62. The reverse osmosis membrane concentrate may be discharged through a reverse osmosis membrane concentrate pipe 64, or may be returned through the reverse osmosis membrane concentrate pipe 64 to an upstream stage of the semipermeable membrane module 18, for example, the semipermeable membrane treated water tank 16 (return step).

[0072] In this manner, the primary-side treated water of the gas-liquid separation membrane, in which the amount of ammonia has been reduced, and the concentrated ammonium sulfate solution, which has been concentrated to a high concentration and reduced in volume, are recovered from the ammonia-containing water to be treated. The recovered primary-side treated water of the gas-liquid separation membrane and the ammonium sulfate solution can be reused.

[0073] In the water treatment method and water treatment device according to this embodiment, ammonia-containing water is concentrated as ammonium sulfate and separated from water, thereby reducing the nitrogen load in the ammonia-containing water and obtaining a concentrated ammonium sulfate solution that has been highly concentrated and reduced in volume as semipermeable membrane concentrated water.

[0074] As the distillation treatment in the distillation step, in addition to a gas-liquid separation treatment using a gas-liquid separation membrane and an ammonia stripping treatment, a membrane distillation treatment or the like may be used.

[0075] In the water treatment device 1 shown in Fig. 1 and the water treatment device 3 shown in Fig. 2, the semipermeable membrane treatment device may be configured to pass a part of the ammonium sulfate solution through the second space 32. An example of such a semipermeable membrane treatment device is shown in Fig. 3.

[0076] 3, a semipermeable membrane treatment water supply pipe 52 from the semipermeable membrane treatment water outlet of the semipermeable membrane treatment water tank 16 is connected to the first space inlet of the semipermeable membrane module 18, as in Fig. 1 or 2, and a semipermeable membrane treatment water supply pipe 53 branched from the semipermeable membrane treatment water supply pipe 52 is connected to the second space inlet of the semipermeable membrane module 18. A semipermeable membrane concentrated water pipe 54 is connected to the first space outlet of the semipermeable membrane module 18, and a semipermeable membrane dilution water pipe 59 is connected to the second space outlet of the semipermeable membrane module 18. The semipermeable membrane dilution water pipe 59 from the second space outlet of the semipermeable membrane module 18 is connected to the inlet of the semipermeable membrane dilution water tank 20, as in Fig. 1 or 2.

[0077] The semipermeable membrane module 18 has a first space 30 (concentration side) and a second space 32 (permeation side) separated by a semipermeable membrane 34, and is an apparatus for concentrating water by passing an ammonium sulfate solution through the first space 30 from the first space inlet of the semipermeable membrane module 18 and through the second space inlet of the semipermeable membrane module 18 to the second space 32, and pressurizing the first space 30, thereby causing the water contained in the ammonium sulfate solution in the first space 30 to permeate into the second space 32 through the semipermeable membrane 34. That is, in the semipermeable membrane treatment device 6, the ammonium sulfate solution is concentrated using the semipermeable membrane 34. The semipermeable membrane treatment device 6 is an apparatus for performing a concentration treatment by supplying ammonium sulfate solution to both the first space 30 and the second space 32 of the semipermeable membrane module 18.

[0078] The ammonium sulfate solution is pressurized and fed from the first space inlet of the semipermeable membrane module 18 to the first space 30 through the semipermeable membrane treated water supply pipe 52 by the pressure pump 26, and is passed through. A portion of the water contained in the pressurized ammonium sulfate solution permeates from the first space 30 toward the second space 32 through the semipermeable membrane 34. At this time, most of the ions and the like cannot permeate the semipermeable membrane 34, so the water in the first space 30 that did not permeate the semipermeable membrane 34 is concentrated. Meanwhile, in the second space 32, a portion of the ammonium sulfate solution passed through the semipermeable membrane treated water supply pipe 53 and the permeate with a low ion concentration that permeated the semipermeable membrane 34 merge, resulting in a dilution effect. The semipermeable membrane concentrated water obtained in the first space 30 is discharged from the first space outlet through the semipermeable membrane concentrated water pipe 54 (semipermeable membrane treatment process).

[0079] The semipermeable membrane diluted water obtained in the second space 32 may be discharged from the second space outlet through the semipermeable membrane diluted water piping 59, or may be sent to the reverse osmosis membrane treatment device 22 as shown in FIG. 1 or 2 and further subjected to reverse osmosis membrane treatment.

[0080] In the water treatment method and water treatment device according to this embodiment, a semipermeable membrane treatment device having a multistage semipermeable membrane module may be used. An example of a semipermeable membrane treatment device having such a configuration is shown in Figure 4. The semipermeable membrane treatment device 7 shown in Figure 4 has a structure in which semipermeable membrane modules are combined in series in three stages, and is a device that passes water through the first space side and the second space side in series.

[0081] The semipermeable membrane treatment device 7 shown in Figure 4 uses semipermeable membrane modules 18 connected in multiple stages, each having a first space 30 (concentration side) and a second space 32 (permeation side) separated by a semipermeable membrane 34. Ammonium sulfate solution is passed through the first space 30 of the first-stage semipermeable membrane module 18, and the first space 30 is pressurized to cause the water contained in the ammonium sulfate solution to permeate through the semipermeable membrane 34, thereby obtaining semipermeable membrane concentrated water. This semipermeable membrane concentrated water is then further obtained using the semipermeable membrane modules 18 in subsequent stages, and at least a portion of the semipermeable membrane concentrated water is passed through the second space 32 of the semipermeable membrane modules 18 in each stage to obtain semipermeable membrane diluted water. For example, the semipermeable membrane treatment means includes a first-stage semipermeable membrane module 18a, a second-stage semipermeable membrane module 18b, and a third-stage semipermeable membrane module 18c. Each semipermeable membrane module has a first space 30 and a second space 32 separated by a semipermeable membrane 34. The semipermeable membrane module 18 is an apparatus for carrying out a concentration treatment by supplying an ammonium sulfate solution to the first space of the first-stage membrane module and then sequentially supplying the semipermeable membrane concentrated water to the first space 30 of the next-stage membrane module.

[0082] In the semipermeable membrane treatment device 7 of Fig. 4, as in Fig. 1 or 2, a semipermeable membrane treated water supply pipe 52 from the semipermeable membrane treated water outlet of the semipermeable membrane treated water tank 16 is connected to the first space inlet of the first-stage semipermeable membrane module 18a. The first space outlet of the first-stage semipermeable membrane module 18a and the first space inlet of the second-stage semipermeable membrane module 18b are connected by a semipermeable membrane concentrated water pipe 100. The first space outlet of the second-stage semipermeable membrane module 18b and the first space inlet of the third-stage semipermeable membrane module 18c are connected by a semipermeable membrane concentrated water pipe 102. A semipermeable membrane concentrated water pipe 104 is connected to the first space outlet of the third-stage semipermeable membrane module 18c. A semipermeable membrane concentrated water pipe 106 branched from the semipermeable membrane concentrated water pipe 104 is connected to the first space inlet of the third-stage semipermeable membrane module 18c. The second space outlet of the third-stage semipermeable membrane module 18c and the second space inlet of the second-stage semipermeable membrane module 18b are connected by a semipermeable membrane dilution water piping 108. The second space outlet of the second-stage semipermeable membrane module 18b and the second space inlet of the first-stage semipermeable membrane module 18a are connected by a semipermeable membrane dilution water piping 110. A semipermeable membrane dilution water piping 112 is connected to the second space outlet of the first-stage semipermeable membrane module 18a. The semipermeable membrane dilution water piping 112 from the second space outlet of the first-stage semipermeable membrane module 18a is connected to the inlet of the semipermeable membrane dilution water tank 20 as shown in Figure 1 or Figure 2.

[0083] The semipermeable membrane module 18 is a device that uses a multistage membrane module having a first space 30 and a second space 32 separated by a semipermeable membrane 34, in which an ammonium sulfate solution is supplied to the first space 30a of the first-stage semipermeable membrane module 18a, the resulting semipermeable membrane concentrated water is passed in series through the first space 30 of the semipermeable membrane module 18 of the next stage, at least a portion of the semipermeable membrane concentrated water of the final-stage semipermeable membrane module 18c is supplied to its own second space 32c, the resulting semipermeable membrane diluted water is passed in series through the second space 32 of the semipermeable membrane module 18 of the previous stage, and the first space 30 of each stage is pressurized to cause the water contained in the first space 30 to permeate into the second space 32 through the semipermeable membrane 34, thereby concentrating the water. That is, in the semipermeable membrane module 18, the ammonium sulfate solution is concentrated using the semipermeable membrane 34, and the semipermeable membrane concentrated water is further concentrated using the semipermeable membrane 34 of the next stage.

[0084] 1 or 2, the ammonium sulfate solution is sent to the first space 30a of the first-stage semipermeable membrane module 18a through the semipermeable membrane treated water supply pipe 52 by the pressure pump 26. Meanwhile, semipermeable membrane dilution water sent via the second space 32c of the third-stage semipermeable membrane module 18c described below and the second space 32b of the second-stage semipermeable membrane module 18b is sent to the second space 32a of the first-stage semipermeable membrane module 18a through the semipermeable membrane dilution water pipe 110. In the first-stage semipermeable membrane module 18a, the first space 30a is pressurized, and the water contained in the first space 30a permeates into the second space 32a through the semipermeable membrane 34a (concentration process (first stage)), and semipermeable membrane dilution water is obtained in the second space 32a (dilution process (first stage)). The semipermeable membrane concentrated water obtained in the first space 30a of the first-stage semipermeable membrane module 18a is sent to the first space 30b of the second-stage semipermeable membrane module 18b through a semipermeable membrane concentrated water piping 100. The semipermeable membrane diluted water obtained in the second space 32a of the first-stage semipermeable membrane module 10a may be discharged from the second space outlet through a semipermeable membrane diluted water piping 112, or may be sent to a reverse osmosis membrane treatment device 22 as shown in Figure 1 or Figure 2 and further subjected to reverse osmosis membrane treatment.

[0085] In the second-stage semipermeable membrane module 18b, the semipermeable membrane dilution water sent via the second space 32c of the third-stage semipermeable membrane module 18c (described later) is sent to the second space 32b of the second-stage semipermeable membrane module 18b through the semipermeable membrane dilution water piping 108. The first space 30b is pressurized, and the water contained in the first space 30b is permeated into the second space 32b through the semipermeable membrane 34b (concentration step (second stage)), and semipermeable membrane dilution water is obtained in the second space 32b (dilution step (second stage)). The semipermeable membrane concentrated water obtained in the first space 30b of the second-stage semipermeable membrane module 18b is sent to the first space 30c of the third-stage semipermeable membrane module 18c through the semipermeable membrane concentrated water piping 102. The semipermeable membrane dilution water obtained in the second space 32b of the second-stage semipermeable membrane module 18b is sent through the semipermeable membrane dilution water piping 110 to the second space 32a of the first-stage semipermeable membrane module 18a.

[0086] In the third-stage semipermeable membrane module 18c, the semipermeable membrane concentrated water obtained in the first space 30c of the third-stage semipermeable membrane module 18c is sent to the second space 32c through the semipermeable membrane concentrated water pipes 104, 106 as described below. The first space 30c is pressurized, and the water contained in the first space 30c is permeated into the second space 32c through the semipermeable membrane 34c (concentration process (third stage)), and semipermeable membrane diluted water is obtained in the second space 32c (dilution process (third stage)) (these are referred to as semipermeable membrane treatment processes). The semipermeable membrane concentrated water obtained in the first space 30c of the third-stage semipermeable membrane module 18c is discharged through the semipermeable membrane concentrated water pipe 104. The semipermeable membrane concentrated water branched from the semipermeable membrane concentrated water pipe 104 is sent to the second space 32c of the third-stage semipermeable membrane module 18c through the semipermeable membrane concentrated water pipe 106. The semipermeable membrane dilution water obtained in the second space 32c of the third-stage semipermeable membrane module 18c is sent through the semipermeable membrane dilution water piping 108 to the second space 32b of the second-stage semipermeable membrane module 18b.

[0087] In the semipermeable membrane treatment device 7 of Fig. 4, as in the semipermeable membrane treatment device 6 of Fig. 3, an ammonium sulfate solution may be supplied to the first space 30a and the second space 32a of the first-stage semipermeable membrane module 18a, and the semipermeable membrane concentrated water may be sequentially supplied to the first space of the next-stage semipermeable membrane module and the semipermeable membrane diluted water may be sequentially supplied to the second space of the next-stage semipermeable membrane module, and the first space 30 of each stage may be pressurized to cause the water contained in the first space 30 to permeate into the second space 32 through the semipermeable membrane 34, thereby concentrating the water. That is, in the semipermeable membrane module 18, the ammonium sulfate solution is concentrated using the semipermeable membrane 34, and the semipermeable membrane concentrated water is further concentrated using the semipermeable membrane 34 of the next stage.

[0088] In such a semipermeable membrane treatment device or the semipermeable membrane treatment device 7 of FIG. 4, water may be passed through the second spaces in series, or a portion of the semipermeable membrane diluted water obtained in the second spaces 32a, 32b, 32c of the semipermeable membrane modules 18a, 18b, 18c of each stage may be discharged outside the system, or may be sent to a semipermeable membrane diluted water tank and stored therein as necessary, and then discharged outside the system.

[0089] The semipermeable membrane treatment devices in Figures 1, 2, 3, and 4 are examples of device configurations, and the arrangement of the semipermeable membrane modules, the method of supplying feed water, and the like may be changed as appropriate. For example, a multi-stage semipermeable membrane module may be used, and a semipermeable membrane module unit having a plurality of semipermeable membrane modules connected in parallel may be used as the semipermeable membrane module in each stage. An example of a semipermeable membrane treatment device having such a configuration is shown in Figure 5. Figure 5 is an example of device configuration, and the number of stages, number of parallel connections, and arrangement of the semipermeable membrane modules, the method of supplying feed water, and the like may be changed as appropriate.

[0090] The semipermeable membrane treatment device 8 shown in FIG. 5 uses semipermeable membrane modules connected in multiple stages, each having a first space 30 (concentration side) and a second space 32 (permeation side) separated by a semipermeable membrane 34, and passes an ammonium sulfate solution through the first space 30 of the semipermeable membrane module of the first stage, pressurizes the first space 30, and causes the water contained in the ammonium sulfate solution to permeate through the semipermeable membrane 34, thereby obtaining concentrated water. This concentrated water is further obtained using semipermeable membrane modules of subsequent stages and thereafter, and at least a portion of the concentrated water or at least a portion of dilution water obtained from another semipermeable membrane module is passed through the second space 32 of the semipermeable membrane module of each stage to obtain dilution water. The semipermeable membrane treatment device 8 includes, for example, a first-stage semipermeable membrane module unit 120a, a second-stage semipermeable membrane module unit 120b, a third-stage semipermeable membrane module unit 120c, and a fourth-stage semipermeable membrane module unit 120d. The first-stage semipermeable membrane module unit 120a, for example, comprises four semipermeable membrane modules connected in parallel, the second-stage semipermeable membrane module unit 120b, for example, comprises four semipermeable membrane modules connected in parallel, the third-stage semipermeable membrane module unit 120c, for example, comprises two semipermeable membrane modules connected in parallel, and the fourth-stage semipermeable membrane module unit 120d, for example, comprises two semipermeable membrane modules connected in parallel. Each semipermeable membrane module 18 has a first space 30 and a second space 32 separated by a semipermeable membrane 34. The semipermeable membrane module unit 120 is an apparatus for performing a concentration treatment by supplying an ammonium sulfate solution to the first space of a first-stage membrane module and sequentially supplying the concentrated water thereof to the first space of a subsequent-stage membrane module.

[0091] In the semipermeable membrane treatment device 8 of Figure 5, as in Figure 1 or Figure 2, a semipermeable membrane treated water supply pipe 52 from the semipermeable membrane treated water outlet of the semipermeable membrane treated water tank 16 is connected to the first space inlet of the first-stage semipermeable membrane module unit 120a. The first space outlet of each semipermeable membrane module of the first-stage semipermeable membrane module unit 120a and the first space inlet of each semipermeable membrane module of the second-stage semipermeable membrane module unit 120b are connected by a semipermeable membrane concentrated water pipe 124. The first space outlet of each semipermeable membrane module of the second-stage semipermeable membrane module unit 120b and the first space inlet of each semipermeable membrane module of the third-stage semipermeable membrane module unit 120c are connected by a semipermeable membrane concentrated water pipe 126. The first space outlet of each semipermeable membrane module of the third-stage semipermeable membrane module unit 120c and the first space inlet of each semipermeable membrane module of the fourth-stage semipermeable membrane module unit 120d are connected by a semipermeable membrane concentrated water pipe 128. A semipermeable membrane concentrated water pipe 130 is connected to the first space outlet of each semipermeable membrane module in the fourth-stage semipermeable membrane module unit 120d. A semipermeable membrane concentrated water pipe 132 branching from the semipermeable membrane concentrated water pipe 130 is connected to the second space inlet of each semipermeable membrane module in the fourth-stage semipermeable membrane module unit 120d. The second space outlet of each semipermeable membrane module in the fourth-stage semipermeable membrane module unit 120d and the second space inlet of each semipermeable membrane module in the third-stage semipermeable membrane module unit 120c are connected by a semipermeable membrane dilution water pipe 134. The second space outlet of each semipermeable membrane module in the third-stage semipermeable membrane module unit 120c and the second space inlet of each semipermeable membrane module in the second-stage semipermeable membrane module unit 120b are connected by a semipermeable membrane dilution water pipe 136. The second space outlet of each semipermeable membrane module of the second-stage semipermeable membrane module unit 120b and the second space inlet of each semipermeable membrane module of the first-stage semipermeable membrane module unit 120a are connected by a semipermeable membrane dilution water piping 138. A semipermeable membrane dilution water piping 140 extending from the second space outlet of each semipermeable membrane module of the first-stage semipermeable membrane module unit 120a is connected to the inlet of the semipermeable membrane dilution water tank 20 as shown in Figure 1 or Figure 2.

[0092] The semipermeable membrane module unit 120 is an apparatus that uses a multistage semipermeable membrane module unit equipped with semipermeable membrane modules 18 having a first space 30 and a second space 32 separated by a semipermeable membrane 34, supplies an ammonium sulfate solution to the first space of each semipermeable membrane module of a first-stage semipermeable membrane module unit, passes the concentrated water successively in series through the first spaces of each semipermeable membrane module of the semipermeable membrane module unit of the next stage, supplies at least a portion of the concentrated water of each semipermeable membrane module of the final-stage semipermeable membrane module unit to its own second space, passes the resulting diluted water in series through the second spaces 32 of each semipermeable membrane module of the preceding stage semipermeable membrane module unit, and concentrates the water by pressurizing the first spaces 30 of each stage, causing the water contained in the first spaces 30 to permeate into the second space 32 through the semipermeable membrane 34. That is, in the semipermeable membrane module unit 120, the ammonium sulfate solution is concentrated using the semipermeable membrane 34, and the concentrated water is further concentrated using the semipermeable membrane 34 of the next stage.

[0093] The ammonium sulfate solution is sent to the first space 30 of each semipermeable membrane module of the first-stage semipermeable membrane module unit 120a through the semipermeable membrane treated water supply pipe 52 by the pressure pump 26 as shown in Figure 1 or Figure 2. Meanwhile, the semipermeable membrane dilution water sent via the second space 32 of each semipermeable membrane module of the fourth-stage semipermeable membrane module unit 120d (described later), the second space 32 of each semipermeable membrane module of the third-stage semipermeable membrane module unit 120c, and the second space 32 of each semipermeable membrane module of the second-stage semipermeable membrane module unit 120b is sent to the second space 32 of each semipermeable membrane module of the first-stage semipermeable membrane module unit 120a through the semipermeable membrane dilution water pipe 138. In each semipermeable membrane module of the first-stage semipermeable membrane module unit 120a, the first space 30 is pressurized, and the water contained in the first space 30 is permeated into the second space 32 through the semipermeable membrane 34 (concentration process (first stage)), and semipermeable membrane diluted water is obtained in the second space 32 (dilution process (first stage)). The semipermeable membrane concentrated water obtained in the first space 30 of each semipermeable membrane module of the first-stage semipermeable membrane module unit 120a is sent through a semipermeable membrane concentrated water piping 124 to the first space 30 of each semipermeable membrane module of the second-stage semipermeable membrane module unit 120b. The semipermeable membrane diluted water obtained in the second space 32 of each semipermeable membrane module of the first-stage semipermeable membrane module unit 120a may be discharged from the second space outlet through a semipermeable membrane diluted water piping 140, or may be sent to a reverse osmosis membrane treatment device 22 as shown in FIG. 1 or 2 and further subjected to reverse osmosis membrane treatment.

[0094] In each semipermeable membrane module of the second-stage semipermeable membrane module unit 120b, the semipermeable membrane dilution water sent via the second space 32 of each semipermeable membrane module of the fourth-stage semipermeable membrane module unit 120d (described later) and the second space 32 of each semipermeable membrane module of the third-stage semipermeable membrane module unit 120c is sent to the second space 32 of each semipermeable membrane module of the second-stage semipermeable membrane module unit 120b through the semipermeable membrane dilution water piping 136. The first space 30 is pressurized, and the water contained in the first space 30 permeates into the second space 32 through the semipermeable membrane 34 (concentration process (second stage)), and semipermeable membrane dilution water is obtained in the second space 32 (dilution process (second stage)). The semipermeable membrane concentrated water obtained in the first space 30 of each semipermeable membrane module of the second-stage semipermeable membrane module unit 120b is sent to the first space 30 of each semipermeable membrane module of the third-stage semipermeable membrane module unit 120c through the semipermeable membrane concentrated water piping 126. The semipermeable membrane diluted water obtained in the second space 32 of each semipermeable membrane module of the second-stage semipermeable membrane module unit 120b is sent through the semipermeable membrane diluted water piping 138 to the second space 32 of each semipermeable membrane module of the first-stage semipermeable membrane module unit 120a.

[0095] In each semipermeable membrane module of the third-stage semipermeable membrane module unit 120c, the semipermeable membrane dilution water sent via the second space 32 of each semipermeable membrane module of the fourth-stage semipermeable membrane module unit 120d (described later) is sent to the second space 32 of each semipermeable membrane module of the third-stage semipermeable membrane module unit 120c through a semipermeable membrane dilution water piping 134. The first space 30 is pressurized, and the water contained in the first space 30 permeates into the second space 32 through the semipermeable membrane 34 (concentration process (third stage)), and semipermeable membrane dilution water is obtained in the second space 32 (dilution process (third stage)). The semipermeable membrane concentrated water obtained in the first space 30 of each semipermeable membrane module of the third-stage semipermeable membrane module unit 120c is sent through a semipermeable membrane concentrated water piping 128 to the first space 30 of each semipermeable membrane module of the fourth-stage semipermeable membrane module unit 120d. The semipermeable membrane diluted water obtained in the second space 32 of each semipermeable membrane module of the third-stage semipermeable membrane module unit 120c is sent through the semipermeable membrane diluted water piping 136 to the second space 32 of each semipermeable membrane module of the second-stage semipermeable membrane module unit 120b.

[0096] In each semipermeable membrane module of the fourth-stage semipermeable membrane module unit 120d, the semipermeable membrane concentrated water obtained in the first space 30 of each semipermeable membrane module of the fourth-stage semipermeable membrane module unit 120d is sent to the second space 32 through semipermeable membrane concentrated water piping 130, 132 as described below. The first space 30 is pressurized, and the water contained in the first space 30 permeates into the second space 32 through the semipermeable membrane 34 (concentration step (fourth stage)), and semipermeable membrane diluted water is obtained in the second space 32 (dilution step (fourth stage)) (these are referred to as semipermeable membrane treatment steps). The semipermeable membrane concentrated water obtained in the first space 30 of each semipermeable membrane module of the fourth-stage semipermeable membrane module unit 120d is discharged through the semipermeable membrane concentrated water piping 130. The semipermeable membrane concentrated water branched from the semipermeable membrane concentrated water pipe 130 is sent to the second space 32 of each semipermeable membrane module of the fourth-stage semipermeable membrane module unit 120d through the semipermeable membrane concentrated water pipe 132. The semipermeable membrane diluted water obtained in the second space 32 of each semipermeable membrane module of the fourth-stage semipermeable membrane module unit 120d is sent to the second space 32 of each semipermeable membrane module of the third-stage semipermeable membrane module unit 120c through the semipermeable membrane diluted water pipe 134.

[0097] In order to concentrate the ammonium sulfate solution to a desired concentration in the semipermeable membrane module, it is preferable to arrange multiple semipermeable membrane modules in series. When using a multi-stage semipermeable membrane module, the number of stages of the semipermeable membrane module may be determined depending on the target concentration of the semipermeable membrane concentrate, etc. For example, if it is desired to obtain a semipermeable membrane concentrate with a higher concentration from an ammonium sulfate solution with a lower concentration, the number of stages of the semipermeable membrane module unit may be increased.

[0098] When a semipermeable membrane module unit having a plurality of semipermeable membrane modules connected in parallel is used as the membrane module of each stage, the number of semipermeable membrane modules in each semipermeable membrane module unit may be determined depending on the flow rate of the ammonium sulfate solution, etc.

[0099] A semipermeable membrane concentration tank and a semipermeable membrane dilution tank may be provided in one or more stages of semipermeable membrane modules, or a semipermeable membrane concentration tank and a semipermeable membrane dilution tank may be provided in each stage of semipermeable membrane module.

[0100] This specification includes the following embodiments: (1) A water treatment device comprising: distillation means for separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution; pressurization means for pressurizing the ammonium sulfate solution; and semipermeable membrane treatment means for using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, passing the ammonium sulfate solution through the first space, pressurizing the first space by the pressurization means to cause water contained in the ammonium sulfate solution to permeate through the semipermeable membrane to obtain semipermeable membrane concentrated water, and passing a portion of the ammonium sulfate solution or at least a portion of the semipermeable membrane concentrated water through the second space to obtain semipermeable membrane diluted water.

[0101] (2) A water treatment device comprising: a distillation means for separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution; a pressurizing means for pressurizing the ammonium sulfate solution; and a semipermeable membrane treatment means for using semipermeable membrane modules connected in multiple stages, each having a first space and a second space partitioned by a semipermeable membrane, in which the ammonium sulfate solution is passed through the first space of the semipermeable membrane module of the first stage, the first space is pressurized by the pressurizing means, and water contained in the ammonium sulfate solution is permeated through the semipermeable membrane to obtain semipermeable membrane concentrated water, and the semipermeable membrane concentrated water is further obtained using a semipermeable membrane module of a subsequent stage or later to obtain semipermeable membrane concentrated water, and the semipermeable membrane diluted water is obtained by passing a portion of the ammonium sulfate solution, at least a portion of the semipermeable membrane concentrated water, or at least a portion of the semipermeable membrane diluted water obtained from another semipermeable membrane module, through the second space of the semipermeable membrane module of each stage.

[0102] (3) The water treatment device according to (1) or (2), wherein the distillation means has a gas-liquid separation membrane.

[0103] (4) The water treatment device according to any one of (1) to (3), wherein the ammonia-containing water is wastewater discharged from a semiconductor factory.

[0104] (5) The water treatment device according to any one of (1) to (4), wherein the sulfuric acid is waste sulfuric acid discharged from a semiconductor factory.

[0105] (6) The water treatment device according to any one of (1) to (5), wherein the ammonia nitrogen concentration of the ammonia-containing water is in the range of 300 mg / L or more and 7000 mg / L or less.

[0106] (7) The water treatment device according to any one of (1) to (6), wherein the ammonium sulfate concentration of the ammonium sulfate solution passed through the semipermeable membrane treatment means is in the range of 20,000 mg / L or more and 100,000 mg / L or less, and the ammonium sulfate concentration of the semipermeable membrane concentrated water obtained by the semipermeable membrane treatment means is 25 mass% or more.

[0107] (8) The water treatment device according to any one of (1) to (7), further comprising: a circulation tank that stores the ammonium sulfate solution; a circulation line that returns the ammonium sulfate solution discharged from the circulation tank to the circulation tank via the distillation means; a circulation means that circulates the ammonium sulfate solution from the circulation tank to the circulation line; a pH measurement means that measures a pH of the ammonium sulfate solution; and a specific gravity measurement means that measures a specific gravity of the ammonium sulfate solution, wherein the water treatment device replenishes sulfuric acid to the circulation tank when a measurement value of the pH measurement means exceeds a predetermined value, and discharges at least a portion of the ammonium sulfate solution when a measurement value of the specific gravity measurement means exceeds a predetermined range.

[0108] (9) A water treatment method comprising: a distillation step of separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution; a pressurizing step of pressurizing the ammonium sulfate solution; and a semipermeable membrane treatment step of using a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane, passing the ammonium sulfate solution through the first space, pressurizing the first space by the pressurization in the pressurizing step, and causing water contained in the ammonium sulfate solution to permeate through the semipermeable membrane to obtain semipermeable membrane concentrated water, and passing a part of the ammonium sulfate solution or at least a part of the semipermeable membrane concentrated water through the second space to obtain semipermeable membrane diluted water.

[0109] (10) A water treatment method comprising: a distillation step of separating ammonia from ammonia-containing water and absorbing the separated ammonia into sulfuric acid to obtain an ammonium sulfate solution; a pressurizing step of pressurizing the ammonium sulfate solution; and a semipermeable membrane treatment step of using semipermeable membrane modules connected in multiple stages, each having a first space and a second space separated by a semipermeable membrane, passing the ammonium sulfate solution through the first space of a first-stage semipermeable membrane module, pressurizing the first space by the pressurization in the pressurizing step, and causing the water contained in the ammonium sulfate solution to permeate through the semipermeable membrane to obtain semipermeable membrane concentrated water, and further using a semipermeable membrane module in a subsequent stage or later to obtain semipermeable membrane concentrated water, and passing a portion of the ammonium sulfate solution, at least a portion of the concentrated water, or at least a portion of semipermeable membrane diluted water obtained from another semipermeable membrane module, through the second space of the semipermeable membrane module in each stage to obtain semipermeable membrane diluted water.

[0110] (11) The water treatment method according to (9) or (10), wherein a gas-liquid separation membrane is used in the distillation step.

[0111] (12) The water treatment method according to any one of (9) to (11), wherein the ammonia-containing water is wastewater discharged from a semiconductor factory.

[0112] (13) The water treatment method according to any one of (9) to (12), wherein the sulfuric acid is waste sulfuric acid discharged from a semiconductor factory.

[0113] (14) The water treatment method according to any one of (9) to (13), wherein the ammonia nitrogen concentration of the ammonia-containing water is in the range of 300 mg / L or more and 7000 mg / L or less.

[0114] (15) The water treatment method according to any one of (9) to (14), wherein the ammonium sulfate concentration of the ammonium sulfate solution passed through the semipermeable membrane treatment step is in the range of 20,000 mg / L or more and 100,000 mg / L or less, and the ammonium sulfate concentration of the semipermeable membrane concentrated water obtained in the semipermeable membrane treatment step is 25 mass% or more.

[0115] (16) The water treatment method according to any one of (9) to (15), further comprising: a circulation step of returning the ammonium sulfate solution discharged from a circulation tank storing the ammonium sulfate solution to the circulation tank via the distillation step; a pH measurement step of measuring a pH of the ammonium sulfate solution; and a specific gravity measurement step of measuring a specific gravity of the ammonium sulfate solution, wherein the circulation tank is replenished with sulfuric acid when the measured value in the pH measurement step exceeds a predetermined value, and at least a part of the ammonium sulfate solution is discharged when the measured value in the specific gravity measurement step exceeds a predetermined range.

[0116] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0117] Example 1 Distillation Treatment Using a Gas-Liquid Separation Membrane Ammonia-containing water was treated under the following test conditions. The experimental equipment consisted of the ammonia-containing water tank 10 and the gas-liquid separator 12 shown in FIG. 1 , and a heating device was installed in the ammonia-containing water tank 10. The treated water obtained on the primary side of the gas-liquid separation membrane was collected and passed through the gas-liquid separator again, and this operation was repeated three times. In addition, the ammonia obtained on the secondary side of the gas-liquid separation membrane was absorbed into sulfuric acid to obtain an ammonium sulfate solution.

[0118] The ammonia nitrogen concentration (NH ４The ammonium sulfate concentration (% by mass) in the ammonium sulfate solution was calculated by converting the ammonia nitrogen concentration determined by the same method into an ammonium sulfate concentration. The results are shown in Table 1.

[0119] (Test conditions) Ammonia-containing water: Ammonium sulfate reagent was added to pure water to adjust the concentration to the predetermined concentration shown in Table 1 (Example 1-1: 2000 mg / L, Example 1-2: 4000 mg / L, Example 1-3: 7000 mg / L). Gas-liquid separation membrane of gas-liquid separator: Polypropylene, porous hollow fiber membrane module. Membrane area: 1.4 m ２ ×3 ・Water flow rate: 0.0385m ３ / h Water temperature: 38°C In the ammonia-containing water tank 10, an aqueous sodium hydroxide solution was added to adjust the pH of the ammonia-containing water to greater than 12. Sulfuric acid: 50% by mass

[0120]

[0121] As can be seen from Table 1, the gas-liquid separation membrane alone could not increase the concentration of ammonium sulfate in the resulting ammonium sulfate solution to 25 mass %. Therefore, the resulting ammonium sulfate solution was subsequently subjected to semipermeable membrane treatment.

[0122] [Semipermeable membrane treatment using a semipermeable membrane] The ammonium sulfate solution having the concentration obtained above was concentrated using a semipermeable membrane module using a semipermeable membrane under the following test conditions. The experimental apparatus was configured as shown in Figure 1, consisting of the semipermeable membrane treated water tank 16, semipermeable membrane module 18, and semipermeable membrane dilution water tank 20, and the semipermeable membrane diluted water in the semipermeable membrane dilution water tank 20 was circulated to the semipermeable membrane treated water tank 16.

[0123] (Test conditions) Semipermeable membrane: Hollosep mini (manufactured by Toyobo) Membrane area: 1.1 m ２ Water flow rate: 20 L Supply pressure: 5 MPa Circulation flow rate: 200 mL / min Water temperature: 30° C. In the semipermeable membrane treated water tank 16, sulfuric acid was added to adjust the pH of the ammonium sulfate solution to 5.

[0124] As a result of concentration using a semipermeable membrane module, a 33% by mass ammonium sulfate solution was obtained under all three conditions of Example 1-1 to Example 1-3.

[0125] As in the examples, it was found that by subjecting an ammonium sulfate solution obtained by distilling ammonia-containing water to semipermeable membrane treatment, a highly concentrated ammonium sulfate solution can be stably obtained from the ammonia-containing water.

[0126] 1, 3 Water treatment device, 5, 6, 7, 8 Semipermeable membrane treatment device, 10 Ammonia-containing water tank, 12 Gas-liquid separation device, 14 Circulation tank, 16 Semipermeable membrane treated water tank, 18 Semipermeable membrane module, 20 Semipermeable membrane dilution water tank, 22 Reverse osmosis membrane treatment device, 24 pH measurement device, 25 Specific gravity measurement device, 26 Pressure pump, 28 Gas-liquid separation membrane, 30 First space, 32 Second space, 34 Semipermeable membrane, 36 Primary side, 38 Secondary side, 40 Ammonia-containing water piping, 42, 80 Ammonia-containing water supply piping, 44 Primary side treated water piping, 46, 48 Circulation piping, 50 Ammonium sulfate solution piping, 52, 53 Semipermeable membrane treated water supply piping, 54, 56, 100, 102, 104, 106, 124, 126, 128, 130, 132 Semipermeable membrane concentrated water piping, 58, 59, 108, 110, 112, 134, 136, 138, 140 Semipermeable membrane diluted water piping, 60 Reverse osmosis membrane treated water supply piping, 62 Reverse osmosis membrane permeate water piping, 64 Reverse osmosis membrane concentrated water piping, 66, 67 Sulfuric acid supply piping, 70 Stripper tower, 72 Vapor compression device, 74 Reboiler, 76 Gas-liquid separation tank, 82, 84, 92 Treated gas piping, 86 Treated water piping, 88, 90 Stripper tower treated water piping, 94 Separated liquid piping, 96 Separated gas piping, 120, 120a, 120b, 120c, 120d Semipermeable membrane module unit.

Claims

1. A water treatment apparatus comprising: a distillation means for separating ammonia from ammonia-containing water and absorbing the separated ammonia in sulfuric acid to obtain an ammonium sulfate solution; a pressurizing means for pressurizing the ammonium sulfate solution; and a semipermeable membrane treatment means for passing the ammonium sulfate solution through the first space of a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, pressurizing the first space by the pressurization by the pressurizing means to permeate water contained in the ammonium sulfate solution through the semipermeable membrane to obtain semipermeable membrane concentrated water, and passing at least a part of the ammonium sulfate solution or at least a part of the semipermeable membrane concentrated water through the second space to obtain semipermeable membrane diluted water.

2. A water treatment apparatus comprising: a distillation means for separating ammonia from ammonia-containing water and absorbing the separated ammonia in sulfuric acid to obtain an ammonium sulfate solution; a pressurizing means for pressurizing the ammonium sulfate solution; and a semipermeable membrane treatment means for passing the ammonium sulfate solution through the first space of a first-stage semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, pressurizing the first space by the pressurization by the pressurizing means to permeate water contained in the ammonium sulfate solution through the semipermeable membrane to obtain semipermeable membrane concentrated water, obtaining semipermeable membrane concentrated water by further using the subsequent-stage semipermeable membrane modules for the concentrated water, and passing at least a part of the ammonium sulfate solution or at least a part of the semipermeable membrane concentrated water or at least a part of the semipermeable membrane diluted water obtained from another semipermeable membrane module through the second space of each stage of the semipermeable membrane module to obtain semipermeable membrane diluted water.

3. The water treatment apparatus according to claim 1 or 2, wherein the distillation means has a gas-liquid separation membrane.

4. The water treatment apparatus according to any one of claims 1 to 3, wherein the ammonia-containing water is wastewater discharged from a semiconductor factory.

5. The water treatment apparatus according to any one of claims 1 to 4, wherein the sulfuric acid is waste sulfuric acid discharged from a semiconductor factory.

6. The water treatment apparatus according to any one of claims 1 to 5, wherein the ammonia nitrogen concentration of the ammonia-containing water is in the range of 300 mg / L or more and 7000 mg / L or less.

7. The water treatment apparatus according to any one of claims 1 to 6, wherein the concentration of ammonium sulfate in the ammonium sulfate solution passed through the semipermeable membrane treatment means is in the range of 20000 mg / L or more and 100000 mg / L or less, and the concentration of ammonium sulfate in the semipermeable membrane concentrated water obtained by the semipermeable membrane treatment means is 25% by mass or more.

8. The water treatment apparatus according to any one of claims 1 to 7, further comprising a circulation tank for storing the ammonium sulfate solution, a circulation line for returning the ammonium sulfate solution discharged from the circulation tank to the circulation tank via the distillation means, a circulation means for circulating the ammonium sulfate solution from the circulation tank to the circulation line, a pH measurement means for measuring the pH of the ammonium sulfate solution, and a specific gravity measurement means for measuring the specific gravity of the ammonium sulfate solution. When the measured value of the pH measurement means exceeds a predetermined value, sulfuric acid is replenished to the circulation tank, and when the measured value of the specific gravity measurement means exceeds a predetermined range, at least a part of the ammonium sulfate solution is discharged.

9. A water treatment method comprising: a distillation step of separating ammonia from ammonia-containing water and absorbing the separated ammonia in sulfuric acid to obtain an ammonium sulfate solution; a pressurization step of pressurizing the ammonium sulfate solution; and a semipermeable membrane treatment step of passing the ammonium sulfate solution through the first space having a first space and a second space partitioned by a semipermeable membrane, pressurizing the first space by the pressurization in the pressurization step to permeate the water contained in the ammonium sulfate solution through the semipermeable membrane to obtain concentrated water, and passing at least a part of the ammonium sulfate solution or at least a part of the concentrated water through the second space to obtain semipermeable membrane diluted water.

10. A distillation step of separating ammonia from ammonia-containing water and absorbing the separated ammonia in sulfuric acid to obtain an ammonium sulfate solution; a pressurization step of pressurizing the ammonium sulfate solution; using a semipermeable membrane module connected in multiple stages having a first space and a second space partitioned by a semipermeable membrane, passing the ammonium sulfate solution through the first space of the first-stage semipermeable membrane module, pressurizing the first space by the pressurization in the pressurization step to allow water contained in the ammonium sulfate solution to permeate through the semipermeable membrane to obtain concentrated water, obtaining concentrated water using the concentrated water in subsequent stages of the semipermeable membrane module, and passing at least a part of the ammonium sulfate solution or at least a part of the concentrated water or at least a part of the semipermeable membrane dilution water obtained from another semipermeable membrane module through the second space of each stage of the semipermeable membrane module to obtain semipermeable membrane dilution water; a water treatment method characterized by including the above steps.

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