Method and device for producing water for pure water, and method and system for producing pure water

Abstract

Provided are a method and device for producing water for pure water, and a method and system for producing pure water using the same, with which it is possible to efficiently remove suspended substances in raw water and to suppress a decrease in the permeation flux of a reverse osmosis membrane device due to residual aluminum over a long period of time. A method for producing water for pure water, the method comprising: a step for obtaining first treated water by adding high-alkalinity polyaluminum chloride to raw water; a step for obtaining second treated water by subjecting the first treated water to activated carbon treatment with spherical activated carbon; and a reverse osmosis membrane step in which the second treated water is subjected to a reverse osmosis membrane treatment.

Description

Technical Field

[0001] The present invention relates to a method and device for producing pure water, a method for producing pure water, and a system for producing pure water. Background Art

[0002] In water treatment such as the manufacture of industrial water and wastewater treatment from river water, well water, lake water, etc., coagulation treatment is performed to remove suspended solids, dissolved organic matter, colloidal silica and other suspended substances. In this coagulation treatment, polyaluminium chloride (PAC) is used as a coagulant. PAC has become popular because of its low cost and wide pH range for coagulation.

[0003] As a method for using PAC in the production of industrial water and wastewater treatment, the following method is known: PAC with a low alkalinity (less than 75%) is mixed into wastewater to form coarse aggregates of suspended matter, and the coarse aggregates are removed by dead-end filtration (for example, refer to Patent Document 1). However, this method requires a slow-rate filtration device, and therefore requires a large area for installing the slow-rate filtration device. For example, assuming that 100 m 3 When treating raw water of 1000 liters / h, a circular slow-rate filtration device with a radius of 12 m is required. In addition, there is no equipment for further treatment of the treated water. Therefore, it is difficult to apply it to extremely limited facilities such as water purification plants, and it is difficult to apply it to the production of pure water and ultrapure water used in the manufacturing processes of semiconductors, liquid crystals, etc.

[0004] In the production of pure water and ultrapure water, tap water, industrial tap water, etc. are used as raw water, and the raw water is passed through a membrane treatment device such as a reverse osmosis membrane device (RO) and an ultrafiltration device (UF), and then a treatment is performed by combining an ion exchange resin device, an ultraviolet irradiation device, etc. In order to remove suspended matter from the raw water, tap water, industrial water, etc. are supplied after the raw water is treated with PAC, but since it contains residual aluminum derived from PAC, a method of removing it using an iron-based inorganic polymer coagulant is also known. This is because the residual aluminum in the raw water adheres to the membrane of the reverse osmosis membrane device, etc., thereby significantly reducing the permeation flux of the membrane treatment device (for example, refer to Patent Document 2).

[0005] In addition, a microfloc method using PAC is also used. This method is a method in which PAC is directly injected into tap water, industrial tap water, etc., or rapidly stirred after injection to form microflocs, which are filtered and removed without precipitation treatment (for example, see Patent Document 3). However, in this method, when a reverse osmosis membrane device is provided in the later stage, the permeation flux of the reverse osmosis membrane device is significantly reduced as described above. Prior art literature Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-086149 Patent Document 2: Japanese Patent Application Publication No. 2008-86966 Patent Document 3: Japanese Patent Application Publication No. 2022-165279 Summary of the invention

[0007] As mentioned above, the use of PAC in the production of pure water and ultrapure water has the following problems: the permeation flux of the reverse osmosis membrane device is reduced due to the attachment of residual aluminum in the water to the membrane. However, in the method of removing residual aluminum using an iron-based inorganic polymer coagulant, there are the following problems: the cost increase and environmental load caused by the increase in the amount of reagents used.

[0008] The present invention is completed to solve the above-mentioned problems, and its purpose is to provide a method and a manufacturing device for pure water, which can efficiently remove suspended matter in raw water and suppress the reduction of permeation flux of reverse osmosis membrane device caused by residual aluminum for a long time. In addition, the object of the present invention is to provide a pure water production method and production system, which can produce high-quality pure water for a long time by efficiently removing suspended matter in raw water and suppressing the reduction in permeation flux of a reverse osmosis membrane device caused by residual aluminum.

[0009] [1] A method for producing pure water, comprising: a step of adding high-alkalinity polyaluminium chloride to raw water to obtain first treated water; a step of subjecting the first treated water to activated carbon treatment by passing it through spherical activated carbon to obtain second treated water; and a step of subjecting the second treated water to reverse osmosis membrane treatment. [2] The production method according to [1], wherein high-basicity polyaluminium chloride is added to the raw water to obtain first treated water containing microflocs. [3] The production method according to [1] or [2], wherein the turbidity of the raw water is greater than or equal to 1 NTU and less than or equal to 100 NTU.

[0010] [4] The production method according to any one of [1] to [3], wherein the basicity of the polyaluminium chloride is greater than 75%. [5] The production method according to [1] to [4], wherein the polyaluminum chloride contains hydroxyaluminum chloride, and the amount of hydroxyaluminum chloride added is 0.25 mg / L or more and 5 mg / L or less relative to the raw water, calculated as the concentration of aluminum oxide (Al2O3). [6] The production method according to any one of [1] to [5], wherein the average particle size of the spherical activated carbon is 0.5 mm or more and 4.0 mm or less.

[0011] [7] A manufacturing method according to any one of [1] to [6], which includes: a filtration step, filtering the first treated water, the filtration treatment including one or more selected from sand filtration, multi-media filter (MMF) filtration, microfiltration (MF) device and ultrafiltration, and the treated water obtained in the filtration step is subjected to the activated carbon treatment. [8] The production method according to [7], wherein the turbidity of the treated water obtained in the filtration step is 0.01 to 0.17 NTU. [9] A method for producing pure water, comprising: a step of supplying high-alkalinity polyaluminium chloride to raw water to obtain first treated water; a step of subjecting the first treated water to activated carbon treatment by passing it through spherical activated carbon to obtain second treated water; a reverse osmosis membrane step of subjecting the second treated water to reverse osmosis membrane treatment; an ultraviolet oxidation step; and an ion exchange step.

[0012]

[10] A device for producing pure water, comprising: a raw water supply device for supplying raw water; a polyaluminium chloride supply device for adding high-alkalinity polyaluminium chloride to the raw water; an activated carbon filtration device for bringing first treated water generated by adding high-alkalinity polyaluminium chloride to the raw water into contact with spherical activated carbon; and a reverse osmosis membrane device for performing reverse osmosis membrane treatment on second treated water generated in the activated carbon filtration device.

[11] The production apparatus according to

[10] , wherein the turbidity of the raw water is greater than or equal to 1 NTU and less than or equal to 100 NTU.

[12] The production apparatus according to

[10] or

[11] , wherein the basicity of the high-basicity polyaluminium chloride is greater than 75%.

[13] A manufacturing device according to any one of

[10] to

[12] , wherein the polyaluminum chloride contains hydroxyaluminum chloride, and the polyaluminum chloride supply device supplies hydroxyaluminum chloride in an amount of 0.25 mg / L to 5 mg / L relative to the raw water in terms of concentration converted to aluminum oxide (Al2O3).

[14] A manufacturing device according to any one of

[10] to

[13] , wherein between the polyaluminium chloride supply device and the activated carbon filtration device, there is one or more selected from a sand filtration device, a multi-media filter (MMF) filtration device, a microfiltration (MF) device and an ultrafiltration device.

[15] A pure water production system comprising, in order: a pure water production device as described in

[14] ; an ultraviolet oxidation device; and an ion exchange device. It should be noted that the symbol “to” represents a numerical range including the numerical values ​​before and after it.

[0013] According to the present invention, a method and apparatus for producing pure water can be provided, which can efficiently remove suspended matter in raw water and suppress the reduction in permeation flux of a reverse osmosis membrane device caused by residual aluminum. In addition, the present invention can provide a pure water production method and production system, which can produce high-quality pure water for a long time by efficiently removing suspended matter in raw water and suppressing the reduction in the permeation flux of the reverse osmosis membrane device caused by residual aluminum. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram schematically showing a production apparatus used in the method for producing pure water according to the embodiment. Figure 2 It is schematically represented in Figure 1 The manufacturing apparatus shown is also a diagram of a manufacturing apparatus having a mixing tank. Figure 3 This is a diagram schematically showing a production apparatus used in a method for producing pure water according to another embodiment. Figure 4 It is schematically represented in Figure 3 The manufacturing apparatus shown is also a diagram of a manufacturing apparatus having a mixing tank. Figure 5 It is a diagram schematically showing a pure water production system using the pure water production apparatus according to the embodiment. Figure 6 This is a diagram schematically showing a pure water production apparatus used in Examples. Figure 7 This is a graph showing the change over time of the permeation flux of the reverse osmosis membrane device. Figure 8 It means to Figure 6 The graph shows the relationship between the space velocity (SV) in the activated carbon filtration device and the turbidity of the permeated water after water has been passed through the device for 5 years. Fig. 9 It means to Figure 6 The graph shows the relationship between the space velocity (SV) and the free chlorine concentration in the activated carbon filtration device after water has been passed through the device for 5 years. Fig.10 This is a diagram schematically showing a batch test apparatus used in Examples. Description of Reference Numerals 1 to 4, 6: pure water production device; 5: ultrapure water production system; 11, 61: raw water supply device; 12, 62: polyaluminium chloride supply device; 13: raw water delivery pipe; 14, 64: reverse osmosis membrane device; 17: spherical activated carbon filtration device; 23, 63: mixing tank; 31: filtration unit; 65: ultrafiltration device; 66: activated carbon filtration device; 50: pre-treatment system; 51: primary pure water system (pure water production system); 52: secondary pure water system (subsystem); 53: point of use (POU); 513: ultraviolet oxidation device (TOC-UV); 514: ion exchange device; TK1, TK2: box; 521: ultraviolet oxidation device (TOC-UV); 522: non-regenerative ultrapure water production ion exchange device (Polisher); 523: membrane degassing device (MDG); 524: ultrafiltration device (UF). DETAILED DESCRIPTION

[0015] Hereinafter, embodiments of the present invention will be described. Figure 1 The manufacturing device 1 used in the manufacturing method of pure water of this embodiment is schematically shown. The manufacturing device 1 includes: a raw water supply device 11 for supplying raw water; a polyaluminum chloride supply device 12 for supplying high-alkalinity polyaluminum chloride (hereinafter also referred to as "high-alkalinity PAC"); a raw water delivery pipe 13 for delivering raw water; and an activated carbon filter device 17 for passing raw water (first treated water) to which high-alkalinity PAC is added through spherical activated carbon. The manufacturing device 1 also includes: a reverse osmosis membrane device 14 for performing reverse osmosis membrane treatment on the second treated water obtained in the activated carbon filter device 17.

[0016] The method for producing pure water using the embodiment of the production device 1 is as follows. First, raw water is supplied from the raw water supply device 11 to the raw water delivery pipe 13. Raw water is urban water such as municipal water, industrial water, river water, lake water, groundwater, well water and other natural water. As for the water quality of the raw water, for example, the turbidity is 1NTU to 100NTU, the suspended solids mass (SS) is 5mg / L to 500mg / L, the total organic carbon (TOC) is 0.5mg / L to 7mg / L, the aluminum concentration is 0.01mg / L to 5mg / L, the residual chlorine concentration is 0.1mg / L to 2mg / L in terms of Cl2, and the pH value is 4 to 9. It should be noted that residual chlorine is sometimes added to the raw water during the transportation using the raw water delivery pipe 13. The raw water supply device 11 includes, for example: a raw water tank for storing raw water and a water supply pump for conveying the raw water in the raw water tank, and the water supply pump supplies the raw water in the raw water tank to the raw water delivery pipe 13. It should be noted that in order to pre-treat the raw water before adding the high alkalinity PAC according to the quality of the raw water, a pre-filter (not shown) may be installed as a pre-treatment device. In addition, in order to adjust the pH of the raw water as needed, an acid or alkali injection device may be installed.

[0017] Next, the polyaluminium chloride supply device 12 adds high alkalinity PAC into the raw water delivery pipe 13. The polyaluminium chloride supply device 12 includes, for example, a chemical tank storing high alkalinity PAC and an injection pump for adding the high alkalinity PAC in the chemical tank to the raw water delivery pipe 13. The injection pump measures the high alkalinity PAC in the chemical tank to a predetermined concentration and adds it to the raw water delivery pipe 13.

[0018] Here, when PAC with lower alkalinity than high alkalinity PAC (hereinafter referred to as "low alkalinity PAC") is added to raw water, suspended matter in the raw water interacts with low alkalinity PAC and condenses to generate fine flocs and coarse flocs. These flocs can be separated by precipitation using a coagulation sedimentation tank, but aluminum ions are prone to leak out of the flocs, or a large number of nano-flocs smaller than micro-flocs are formed. Therefore, if the treated water to which low alkalinity PAC is added is subjected to reverse osmosis membrane treatment, the aluminum in the treated water adheres to the reverse membrane surface, so that the reverse osmosis membrane is easily clogged, and the permeation flux of the reverse osmosis membrane device is reduced in advance.

[0019] In contrast, in the manufacturing method of this embodiment, by supplying high-alkalinity PAC to raw water, suspended matter in the raw water interacts with high-alkalinity PAC to form microflocculates. Passing through the microflocculates can significantly reduce the adhesion of residual aluminum to the membrane of the reverse osmosis membrane device 14, and maintain the performance of the reverse osmosis membrane device for a long time.

[0020] Microflocs are aggregates of suspended matter and high-basicity PAC with a size of about 1 to 10 μm. High-basicity PAC easily forms microflocs, but it is difficult to form coarse flocs or flocs finer than microflocs (nanoflocs). Aluminum ions are not easy to leak out of microflocs, so by passing through the microflocs, the clogging of the reverse osmosis membrane can be prevented for a long time.

[0021] The high basicity PAC in this embodiment comprises polyaluminium chloride represented by the following chemical formula (1). The high basicity PAC in this embodiment preferably has a basicity greater than 75%, more preferably greater than 83%. The upper limit of the basicity is usually less than about 84%. The basicity is a value calculated by n / 6×100(%). [Al2(OH) n Cl 6-n ] m (1≤n≤5, m≤10)……(1)

[0022] High basicity PAC can be produced by the method described in Japanese Patent No. 4104773, for example. As high basicity PAC, only one kind may be used, or two or more kinds may be used in combination. When two or more kinds are used in combination, the basicity of the two or more high basicity PACs may be the same or different, but the basicity of the high basicity PACs used is preferably greater than 75%, more preferably greater than 83%.

[0023] As a high basicity PAC, hydroxyaluminum chloride (Al2Cl(OH)5) is preferably used. Hydroxyaluminum chloride is a polyaluminum chloride in which n=5 and m=1 in the above chemical formula (1) and has a basicity of 83.3%. Hydroxyaluminum chloride is more likely to form more uniform microflocculates. This is believed to be due to the high basicity and small molecular weight of hydroxyaluminum chloride.

[0024] The amount of high basicity PAC is preferably 0.125 mg / L or more in terms of Al2O3 relative to the turbidity 1NTU in the raw water. Specifically, the amount of high basicity PAC is preferably 0.25 mg / L or more in terms of Al2O3 and 5 mg / L or less in terms of Al2O3 relative to the amount of raw water, and more preferably 0.3 mg / L or more in terms of Al2O3 and 3 mg / L or less in terms of Al2O3. In particular, when hydroxyaluminum chloride (Al2Cl(OH)5) is used as high basicity PAC, the amount of hydroxyaluminum chloride is preferably 0.25 mg / L or more in terms of Al2O3 and 2 mg / L or less in terms of Al2O3 relative to the total amount of raw water. Even if the amount of high basicity PAC is a small amount as described above, it can microflocculate the suspended matter in the raw water. In addition, since high basicity PAC works even in a small amount as described above, it is easy to prevent clogging of the reverse osmosis membrane device 14 in the rear section. It should be noted that the expression "in terms of Al 2 O 3 " indicates a value converted into the concentration of aluminum oxide (Al 2 O 3 ). It should be noted that, before or after the addition of the high-basicity PAC, a polymer coagulant, other inorganic coagulants, or the like may be added as an aggregation-promoting auxiliary agent as necessary.

[0025] Here, Figure 2 A pure water production device 2 having a mixing tank 23 for adding high alkalinity PAC to raw water is schematically shown. The production device 2 is different from the above-mentioned production device 1 in that the mixing tank 23 is provided on the path of the raw water conveying pipe 13, but the other structures are the same. In this embodiment, the detailed description of the same structure and function as the production method using the production device 1 is omitted.

[0026] In the manufacturing device 2, raw water is supplied from the raw water supply device 11 to the mixing tank 23, and high alkalinity PAC is supplied from the polyaluminium chloride supply device 12 to the mixing tank 23. In the mixing tank 23, suspended matter in the raw water interacts with high alkalinity PAC, thereby forming microflocculates. In this case, the order of supplying to the mixing tank 23 may be that either the raw water or the high alkalinity PAC is supplied first, or both are supplied simultaneously, and it is preferred that the high alkalinity PAC is added to the mixing tank 23 supplied with raw water.

[0027] Figure 2 The manufacturing device 2 shown in the figure rapidly stirs the raw water and the high alkalinity PAC in the mixing tank 23, so that nano-flocs are not generated and more homogeneous micro-flocs are easily formed. The stirring speed is preferably 150s in terms of G value. -1 More than 150 s, more preferably 150 to 250 s -1 , more preferably 250s -1 In addition, the stirring time by the rapid stirring machine is 2 minutes or more, preferably 3 minutes or more, and more preferably 6 minutes or more. The greater the G value of the rapid stirring, the shorter the stirring time can be.

[0028] Next, the first treated water containing microflocs is supplied to Figure 1 or Figure 2 In the activated carbon filter device 17, the activated carbon is used for filtering. Thus, as the permeated water of the activated carbon filter device 17, the second treated water is obtained.

[0029] The activated carbon filter device 17 has spherical activated carbon as a filter material. The spherical activated carbon is, for example, a spherical activated carbon with an average particle size of about 0.5 mm or more and about 4.0 mm or less and a high uniformity of size. The inventors of the present invention have found that by allowing the first treated water containing microflocs to be treated by spherical activated carbon, the reduction in the permeation flux of the reverse osmosis membrane device 14 in the rear section is significantly reduced compared with the case of using granular activated carbon or powdered activated carbon. In addition, it is found that by using spherical activated carbon, the removal performance of residual chlorine can be maintained for a long time compared with the case of using granular activated carbon or powdered activated carbon, thereby also suppressing the membrane degradation of the reverse osmosis membrane device 14 in the rear section. In addition, by using spherical activated carbon, the water pressure difference of the spherical activated carbon filter device after backwashing is excellent, which is related to reducing the frequency of backwashing and further reducing the amount of washing water. It should be noted that the average particle size of the spherical activated carbon can be evaluated according to JIS K 1474. That is, based on the results obtained by the operation of JISK 1474, a cumulative line graph of the particle size of spherical activated carbon is prepared. The mesh size (mm) of the sieve indicated by the intersection of the vertical line at the 50% point on the horizontal axis and the cumulative line graph of the particle size is obtained by drawing a horizontal line to the vertical axis. The value of the mesh size is taken as the average particle size of the spherical activated carbon. It should be noted that granular activated carbon is, for example, a shape obtained by crushing activated carbon into granules, and powdered activated carbon is, for example, a shape obtained by crushing activated carbon into a powder of 0.5μm to 30μm.

[0030] The hardness of the spherical activated carbon is preferably above 90, more preferably above 93, and further preferably above 94. The hardness of the spherical activated carbon is, for example, below 99. The high hardness of the spherical activated carbon can maintain the removal performance of residual chlorine for a long time, and thus can help maintain the permeation flux of the reverse osmosis membrane device in the rear section. The uniformity coefficient of the spherical activated carbon is preferably below 2.0, more preferably below 1.8, and further preferably below 1.4. The uniformity coefficient of the spherical activated carbon is generally greater than 1.0. The smaller the uniformity coefficient, the easier it is to recover the water pressure difference after backwashing, and the more suitable it is for long-term water treatment. It should be noted that the hardness and uniformity coefficient of the spherical activated carbon can be evaluated according to JIS K 1474.

[0031] As the spherical activated carbon, a commercially available product can be used, for example, the spherical Shirasagi series manufactured by Osaka Gas Chemical Co., Ltd., BAC manufactured by Kureha Co., Ltd., etc. can be used.

[0032] In the manufacturing method of this embodiment, by using the spherical activated carbon as described above, water can be preferably passed at a space velocity (SV) of 5 to 100 (1 / h) in the activated carbon filter 17, and water can be more preferably passed at a SV of 30 to 100 (1 / h). In particular, if the SV is 30 to 100 (1 / h), the space velocity can be increased, so that sufficient water quality can be obtained with a small amount of activated carbon used, so that the activated carbon filter 17 can be made compact, and treated water with low turbidity and low residual chlorine concentration can be stably produced.

[0033] As the activated carbon filter 17, an independent type filter can be used. As the independent type filter, similar to the filter unit described later, a cylindrical type activated carbon filter or a modular type activated carbon filter can be used. According to the independent type activated carbon filter 17, the outflow of nano-flocs to the downstream side is small, so it is effective in preventing the clogging of the reverse osmosis membrane device 14. In particular, in the case of using the method of this embodiment to manufacture ultrapure water for manufacturing semiconductors, etc., by using an independent type activated carbon filter 17, a plurality of independent type activated carbon filter devices 17 are preliminarily arranged in parallel, and regeneration such as backwashing and module replacement are performed one by one among the plurality of devices, and continuous operation is performed by other devices (so-called carousel operation), thereby being able to continue the manufacture of ultrapure water without stopping the device.

[0034] The water quality of the second treated water obtained in this way is, for example, a turbidity of 0.01 NTU to 1 NTU and a free chlorine concentration of 0.01 mg / L to 0.1 mg / L in terms of Cl 2 .

[0035] Next, the second treated water filtered by the spherical activated carbon is supplied to the reverse osmosis membrane device 14 for reverse osmosis membrane treatment. In order to suppress the decrease in the permeation flux in the reverse osmosis membrane device 14, the water supply pressure to the reverse osmosis membrane device 14 is preferably 0.5MPa to 3MPa, and the water recovery rate in the reverse osmosis membrane device 14 is preferably 75% to 95%. It should be noted that, before being supplied to the reverse osmosis membrane device 14, a scale inhibitor or an antibacterial agent may be appropriately added to the second treated water.

[0036] As the reverse osmosis membrane device 14, any type of reverse osmosis membrane device in the ultra-low pressure type, ultra-low pressure type, low pressure type, medium pressure type, and high pressure type can be used. As the reverse osmosis membrane possessed by the reverse osmosis membrane device 14, a spiral reverse osmosis membrane with aromatic polyamide as the constituent material is preferred. In addition, as the reverse osmosis membrane device 14, there are positive charge membranes with positive charges on the surface of the reverse osmosis membrane, negative charge membranes with negative charges on the surface, and non-charged membranes with no charges on the surface, among which the negative charge membrane is not prone to blockage caused by flocculants of the reverse osmosis membrane, so it is preferred. As the reverse osmosis membrane device 14, an ultra-low pressure or low pressure type negative charge membrane is preferred. As a reverse osmosis membrane device with an ultra-low pressure or low pressure type negative charge membrane, a commercially available product can be used, for example, "ES20" manufactured by Nitto Denko Corporation, "SU series", "TM series", "TBW series" manufactured by Toray Industries, Ltd., and "BW series" manufactured by Dow Corporation can be used.

[0037] A permeate water delivery pipe 15 is connected to the permeate side of the reverse osmosis membrane device 14, and the permeate water is delivered to the downstream section via the delivery pipe 15. A concentrated water discharge pipe 16 is connected to the concentrated water side of the reverse osmosis membrane device 14. The concentrated water can be discharged to the outside of the system of the manufacturing device 1 via the discharge pipe 16, or returned to the upstream section of the reverse osmosis membrane device 14 for reprocessing. The water quality of the permeate water obtained in this way is, for example, turbidity of 0.01 NTU to 0.2 NTU, aluminum concentration of 0 mg / L to 0.002 mg / L, pH of 5.9 to 6.5, and conductivity of 3 μS / cm to 6 μS / cm.

[0038] Next, another embodiment of the present invention will be described. Figure 3 The production device 3 used in the method for producing pure water of this embodiment is schematically shown. The production device 3 is similar to the production device 3 in that it includes a filter unit 31 between the installation position of the polyaluminum chloride supply device 12 and the activated carbon filter device 17 on the path of the raw water conveying pipe 13. Figure 1 The manufacturing apparatus 1 shown is different, but the other structures are the same. In this embodiment, the detailed description of the same structure and function as the manufacturing method using the manufacturing apparatus 1 is omitted.

[0039] Used Figure 3 The method for producing pure water in the embodiment of the production device 3 shown is as follows. First, raw water is supplied from the raw water supply device 11 to the raw water delivery pipe 13. Then, high-basicity PAC is added to the raw water delivery pipe 13 supplied with raw water by the polyaluminium chloride supply device 12. The preferred embodiment of the high-basicity PAC used here is Figure 1 The manufacturing method of the manufacturing device 1 shown is the same.

[0040] By supplying raw water and high alkalinity PAC into the raw water delivery pipe 13, the suspended matter in the raw water interacts with the high alkalinity PAC to form microflocs. By passing through the microflocs, the adhesion of residual aluminum to the membrane of the reverse osmosis membrane device 14 can be significantly reduced, and the performance of the reverse osmosis membrane device can be maintained for a long time. The first treated water containing microflocs in the raw water delivery pipe 13 is then supplied to the filter 31 and the activated carbon filter 17 in sequence. At this time, by providing a water supply pump on the path of the raw water delivery pipe 13, the first treated water can be supplied to the filter 31 by the water supply pump. In this embodiment, a mixing tank is not used, so the device becomes compact and is easy to be installed in a semiconductor manufacturing plant or the like. It should be noted that if a pipeline mixer or the like is provided in the delivery pipe 13 after the high alkalinity PAC is supplied in order to promote mixing, the formation of microflocs can be performed more reliably, thereby further suppressing the clogging of the equipment in the later stage.

[0041] The filter unit 31 includes one or more filter devices selected from a sand filter device, a multi-media filter (MMF) filter device, an ultrafiltration device, and a microfiltration (MF) device, and performs a filtration treatment on the first treated water. Thus, microflocculates mainly containing suspended matter in the water are removed to obtain third treated water. The obtained treated water is then supplied to the activated carbon filter device 17.

[0042] The sand filter device has, for example, supporting gravel or sand (filter sand) as filter material. The multi-media filter (MMF) filtration device includes, for example, a filter material having a three-layer structure in which anthracite, sand, and garnet are stacked from bottom to top in order of particle size. The ultrafiltration (UF) device includes an ultrafiltration membrane with a nominal pore size of 0.001 to 0.1 μm as a filter material, and may be either a full-flow filtration method or a cross-flow filtration method. The ultrafiltration (UF) device is preferably an external pressure ultrafiltration device using a hollow fiber membrane. The microfiltration (MF) device includes, for example, a microfiltration membrane having a nominal pore size of 0.1 to 5 μm, and is capable of full volume filtration.

[0043] The filter section 31 may have one of the above-mentioned filter devices selected from the group consisting of a sand filter device, a multi-media filter (MMF) filter device, a microporous filter (MF) device, and an ultrafiltration (UF) device, or a combination of two or more filter devices, depending on the quality of the raw water. In the case of a combination of two or more filter devices, it is preferred to configure a sand filter device and a multi-media filter (MMF) filter device on the upstream side, and a microporous filter (MF) device and an ultrafiltration device on the downstream side. The filter section 31 is further preferably provided with only an ultrafiltration device. By providing the filter section 31, microflocs in the first treated water can be removed with high precision, thereby reducing the load of the reverse osmosis membrane device 14 in the rear section, and thus obtaining high-quality permeate water for a long time.

[0044] exist Figure 3 In the manufacturing device 3 shown, the filter section 31 is an independent filter section having an independent filter device. As independent filter devices, a cartridge filter device and a modular filter device can be listed. The cartridge filter device is, for example, constructed as follows: a cartridge containing filter material in a shell, a pipe connected to a water inlet and a drain outlet opened in the shell, and water is passed into the cartridge through the opening. The cartridge filter device has the following advantages: when the filter material deteriorates, only the cartridge can be replaced. The modular filter device is constructed as follows: the filter material is arranged inside the shell, and the module is connected to the pipe, thereby passing water to the filter material. In the modular filter device, there are the following advantages: each module can be replaced when the filter material deteriorates, and the deteriorated filter material can be cleaned for each module. According to the independent filter section 31, the outflow of nanoflocs to the downstream side is small, so it is effective in preventing the clogging of the reverse osmosis membrane device 14. In particular, when the method of this embodiment is used to manufacture ultrapure water for manufacturing semiconductors, etc., by using an independent filter unit 31, a plurality of independent filter units 31 are pre-arranged in parallel, and regeneration such as backwashing and module replacement are performed one by one among the plurality of units (so-called carousel operation), thereby continuously manufacturing ultrapure water without stopping the device.

[0045] As for the water quality of the treated water (treated water of the filter unit 31) thus obtained, for example, the turbidity is 0.01NTU to 0.4NTU, preferably 0.01NTU to 0.17NTU, the free chlorine concentration is 0.01mg / L to 0.1mg / L in terms of Cl2, the aluminum concentration is 0.01mg / L to 0.04mg / L, the pH is 7.2 to 8.3, and the conductivity is 140μS / cm to 270μS / cm. In the method of this embodiment, by using high-alkalinity PAC, regardless of the pH value of the raw water to which the high-alkalinity PAC is added, homogeneous microflocs can be stably formed, so there is no need to add a pH adjuster, and the amount of chemicals used can be reduced. Therefore, although the pH of the third treated water (treated water of the filter unit 31) sometimes changes, the aluminum concentration remains low and stable.

[0046] Figure 4 The schematic diagram shows a pure water production device 4 having a mixing tank 23 for adding high alkalinity PAC to raw water and a filtration unit 31. The production device 4 is different from the pure water production device 4 in that the mixing tank 23 is provided on the route of the raw water conveying pipe 13. Figure 3 The manufacturing apparatus 3 shown is different, but the other configurations are the same. In this embodiment, detailed description of the same configurations and functions as those of the manufacturing method using the manufacturing apparatus 3 is omitted.

[0047] In the manufacturing device 4, raw water is supplied from the raw water supply device 11 to the mixing tank 23, and high alkalinity PAC is supplied from the polyaluminium chloride supply device 12 to the mixing tank 23. In the mixing tank 23, the suspended matter in the raw water interacts with the high alkalinity PAC, thereby forming microflocs. In particular, by using the mixing tank 23, the formation of microflocs based on the high alkalinity PAC is fully carried out, thereby further suppressing the clogging of the equipment in the subsequent stage. In this case, the order of supplying to the mixing tank 23 may be that either the raw water or the high alkalinity PAC is supplied first, or both are supplied simultaneously, and it is preferred that the high alkalinity PAC is added to the mixing tank 23 supplied with raw water. It should be noted that, as described above, in the method of this embodiment, the adjustment of the pH of the raw water in the mixing tank 23 is not necessary.

[0048] Figure 4 The manufacturing apparatus 4 shown has an independent type filtering unit 31 which is separate and independent from the mixing tank 23 at the rear stage of the mixing tank 23. The configuration of the independent type filtering unit 31 is the same as that of the manufacturing apparatus 3 described above.

[0049] In addition, as the filter unit 31, an immersion type filter device configured for tank immersion can be used. The immersion type filter device configured for tank immersion is immersed in the bottom of the mixing tank 23, which has the following advantages: the first treated water added with high alkalinity PAC can be filtered directly by the filter device without using piping. As the immersion type filter device, an ultrafiltration device or an MMF type filter device is preferred. In the manufacturing device 4 of the present embodiment, microflocs are formed in water by using high alkalinity PAC, and filtering treatment can be directly performed without precipitation removal using a coagulation sedimentation tank as used in coarse flocs. Therefore, the filter unit 31 can be immersed in the mixing tank 23 and integrated, which can simplify the overall structure of the device.

[0050] In the filtration unit 31, when a plurality of filtration devices are used, only the immersed type or only the independent type may be used, or both the immersed type and the independent type may be used. In this embodiment, it is preferred to use only the independent type filtration device, and it is more preferred to use the independent type ultrafiltration device. As the ultrafiltration membranes possessed by independent ultrafiltration devices, there are hollow fiber membranes, spiral membranes, and flat membranes made of materials such as cellulose acetate, aromatic polyamide, polyvinyl alcohol, polysulfone, and polyvinylidene fluoride. Among them, hollow fiber membranes made of fluorine-based materials such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) are preferred. As the filtration membrane provided in the immersion type ultrafiltration device, a flat membrane made of ceramic or a fluorine-based material such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE) is preferable.

[0051] By utilizing Figure 3 or Figure 4The first treated water is filtered by the filter unit 31, and the microflocs containing suspended matter in the water are removed to obtain the third treated water. The third treated water is then treated by the activated carbon filter device 17 to generate the second treated water, which is supplied to the reverse osmosis membrane device 14 for treatment.

[0052] Next, refer to Figure 5 A pure water production system 5 according to an embodiment using the above-described production apparatus 1 will be described. Figure 5 1 is a block diagram schematically showing the structure of an ultrapure water production system 5 using the production apparatus 1. Figure 5 In the above description, the production apparatus 1 can be changed to any one of the production apparatuses 2 to 4 .

[0053] like Figure 5 As shown, the ultrapure water production system 5 sequentially includes a pretreatment system 50, a primary pure water system (pure water production system) 51, and a secondary pure water system (subsystem) 52. The secondary pure water system 52 is connected to a point of use (POU) 53 via piping, so that the ultrapure water produced by the ultrapure water production system 5 is supplied to the POU 53.

[0054] The pretreatment system 50 includes the production apparatus 1 of the above-described embodiment and, if necessary, a prefilter, a heat exchanger for temperature control, and the like.

[0055] The ultrapure water production system 5 includes a tank TK1 at the downstream of the pretreatment system 50 . The treated water pretreated by the pretreatment system 50 is introduced into the tank TK1 and temporarily stored, and then supplied to the primary pure water system 51 .

[0056] The primary pure water system 51 removes organic matter, ion components, and dissolved gases from pre-treated water to produce primary pure water. The primary pure water system 51 includes an ultraviolet oxidizing device (TOC-UV) 513 and an ion exchange device 514 in this order.

[0057] The ultraviolet oxidizing device 513 has, for example, an ultraviolet lamp that radiates ultraviolet rays with a wavelength of about 185 nm and ultraviolet rays with a wavelength of about 254 nm. By irradiating the water to be treated with ultraviolet rays from the ultraviolet lamp, the total organic carbon component (TOC) in the water to be treated is oxidized and decomposed. The ultraviolet rays radiated by the ultraviolet oxidizing device 513 decompose the water to generate OH radicals, and the organic matter in the water to be treated is oxidized and decomposed into organic acids by the OH radicals. The amount of ultraviolet irradiation in the ultraviolet oxidizing device 513 of the primary pure water system can be appropriately changed according to the water quality of the water to be treated.

[0058] The ion exchange device 514 is one or more of an ion exchange resin device and an electrodeionization device. As the ion exchange resin device, one or more selected from a cation exchange resin device, an anion exchange resin device, a mixed bed ion exchange resin device and a multiple bed ion exchange resin device can be used in combination according to the required water quality. The cation exchange resin used in the cation exchange resin device can be a strongly acidic cation exchange resin or a weakly acidic cation exchange resin. The anion exchange resin used in the anion exchange resin device can be a strongly basic anion exchange resin or a weakly basic anion exchange resin. As the ion exchange resin, a boron adsorbing ion exchange resin can also be used.

[0059] The primary pure water obtained by the primary pure water system 51 has, for example, a resistivity of 17 MΩ·cm or more and a TOC concentration of 10 μgC / L or less.

[0060] The ultrapure water production system 5 is provided with a primary pure water tank TK2 for storing primary pure water and a secondary pure water system 52 in the subsequent stage of the primary pure water system 51. The primary pure water produced by the primary pure water system is temporarily stored in the primary pure water tank TK2 and then sent to the secondary pure water system 52. The secondary pure water system 52 is provided with an ultraviolet oxidizing device (TOC-UV) 521, an ion exchange device (Polisher) 522 for non-regenerative ultrapure water production, a membrane degassing device (MDG) 523, and an ultrafiltration device (UF) 524.

[0061] The structure of the ultraviolet oxidation device 521 in the secondary pure water system 52 is the same as that of the ultraviolet oxidation device 513 in the primary pure water system 51. The non-regenerative ultrapure water production ion exchange device 522 is a mixed bed ion exchange resin device in which a strongly acidic cation exchange resin and a strongly basic anion exchange resin are mixed and filled in a container such as a gas cylinder. The non-regenerative ultrapure water production ion exchange device 522 adsorbs and removes ion components generated by decomposing organic matter by the ultraviolet oxidation device 521.

[0062] The membrane degassing device 523 removes dissolved gas via a degassing membrane. The membrane degassing device 523 removes trace dissolved oxygen in the primary pure water, reducing the dissolved oxygen concentration to, for example, about 1 μg / L or less. The ultrafiltration device 524 performs filtration processing using an ultrafiltration membrane to remove trace elutions and particulate components from the ion exchange resin on the upstream side, for example, reducing the number of particles larger than 0.05 μm to about 250 Pcs. / L or less.

[0063] In this way, the secondary pure water system 52 processes the primary pure water to produce ultrapure water with higher purity. As for the quality of the ultrapure water, for example, the total organic carbon (TOC) concentration is less than 1 μgC / L, the resistivity is more than 18 MΩ·cm, and the boron concentration is less than 0.1 ppb (μg / L). The ultrapure water produced in the secondary pure water system is supplied to the use point 53.

[0064] It should be noted that, in each of the above-mentioned embodiments, the water quality of raw water and treated water can be measured by the following methods or devices, respectively. Turbidity: A measure of light scattering. Aluminum concentration: ICP luminescence analysis. pH: electrode method. Electrical conductivity: Electrical conductivity meter (HE-960CW manufactured by Horiba, Ltd.). Total organic carbon (TOC) concentration: TOC meter (except ultrapure water: Sievers M9e manufactured by VEOLIA). Example

[0065] Next, examples will be described. The present invention is not limited to the following examples.

[0066] Figure 6 The pure water production apparatus 6 used in the present example and the comparative example is schematically shown. Figure 6 The manufacturing device 6 shown in the figure includes: a raw water supply device 61 for supplying raw water; a polyaluminium chloride supply device 62 for supplying high alkalinity PAC; and a mixing tank 63 for supplying raw water and high alkalinity PAC inside. The manufacturing device 6 also includes an ultrafiltration device 65, an activated carbon filtration device 66, and a reverse osmosis membrane device 64 in sequence on the downstream side of the mixing tank 63. In the examples and comparative examples, as described below, a predetermined amount of PAC of a predetermined alkalinity is added to raw water, and the treatment is continuously performed in sequence using the ultrafiltration device 65, the activated carbon filtration device 66, and the reverse osmosis membrane device 64, and the time-dependent change of the permeation flux in the reverse osmosis membrane device 64 is measured.

[0067] The specifications of each device used in the examples are as follows. Mixing tank 63: capacity 1m 3 . Ultrafiltration device 65: Purear GL manufactured by Kuraray Corporation (PVDF membrane, nominal pore size 0.02 μm). Reverse osmosis membrane device 64: TM710 manufactured by Toray Industries, Inc. (low-pressure type, load-electric membrane) Water recovery rate 85%. Determination of aluminum concentration: high frequency inductively coupled plasma (ICP) luminescence analysis. Turbidity measurement: Turbidimeter (Hach2100P, manufactured by TOADKK Co., Ltd.). pH measurement: Water quality meter (Horiba D200, manufactured by Horiba Corporation). Measurement of TOC: TOC meter (Sievers M9e, manufactured by VEOLIA). The quality of raw water (lake water): turbidity 4NTU, pH=7.2, conductivity 250μS / cm, TOC 4mg / L.

[0068] (Example 1) Hypochlorous acid was added to the raw water in such a manner that the free chlorine concentration was 2 mg / L in terms of Cl2, and the mixture was supplied to the mixing tank 63. Then, an aqueous solution of hydroxyaluminum chloride (Al2Cl(OH)5) (a trial product of Nomura Microscience Co., Ltd., with an alkalinity of 83.33%) was added as a high-alkalinity PAC, and the aluminum concentration in the raw water was 1.2 mg / L in terms of the concentration converted to Al2O3, and the mixture was stirred. After stirring, the raw water was sampled, and 80 ml of the raw water was passed through a membrane with a nominal pore size of 0.2 μm (size 47 mmφ), and the particles captured by the membrane were observed. As a result, particles of about 1 to 10 μm were observed. The elemental composition of the particles was confirmed by energy dispersive X-ray fluorescence spectroscopy (EDX), and the results showed that the particles contained Al. Moreover, when the same amount of water was passed through a membrane with a nominal pore size of 0.45 μm (size 47 mmφ), there was almost no pressure difference. From the above results, it was confirmed that microflocculates were formed in this example.

[0069] The treated water in the mixing tank 63 is filtered by passing through the ultrafiltration device 65 and the activated carbon filter device 66 in sequence. Next, the treated water of the activated carbon filter device 66 is supplied to the reverse osmosis membrane device 64 for reverse osmosis membrane treatment. The activated carbon used in the activated carbon filter device 66 is spherical activated carbon (NOMULITE Beads-AC (prototype), particle size 1.2 mm, hardness 98%, uniformity coefficient 1.4), and the SV of the activated carbon filter device 66 is 30 (1 / h).

[0070] (Example 2) In Example 1, except that high-basicity PAC (basicity 76%) produced by the method described in Japanese Patent No. 4104773 was used as high-basicity PAC, the treatment was continued in the same manner as in Example 1 using the ultrafiltration device 65, the activated carbon filtration device 66, and the reverse osmosis membrane device 64 in this order. In Example 2, the formation of microflocs was also confirmed.

[0071] (Comparative Example 1) In Example 1, granular activated carbon (Diahope M006LFA, manufactured by Mitsubishi Chemical Calgon Co., Ltd., average particle size 1.1-1.4 mm, hardness 94%, uniformity coefficient 1.8) was used in the activated carbon filter 66, and the SV of the activated carbon filter 66 was set to 10 (1 / h). In the same manner as in Example 1, the treatment was continuously performed using the ultrafiltration device 65, the activated carbon filter 66, and the reverse osmosis membrane device 64 in this order. In Comparative Example 1, the formation of microflocculates was also confirmed.

[0072] (Comparative Example 2) In Comparative Example 1, low alkalinity PAC (PAC250A, manufactured by Taki Chemical Co., Ltd., alkalinity 50%) was used as PAC so that the aluminum concentration in the raw water was 0.3 to 0.4 mg / L in terms of Al2O3, and the same spherical activated carbon as in Example 1 was used in the activated carbon filter 66, and the SV of the activated carbon filter 66 was set to 30 (1 / h). In the same manner as in Comparative Example 1, the treatment was continuously performed using the ultrafiltration device 65, the activated carbon filter 66, and the reverse osmosis membrane device 64 in sequence. The formation state of the flocs was the same as in Comparative Example 1.

[0073] (Comparative Example 3) In Example 1, low alkalinity PAC (PAC250A, manufactured by Taki Chemical Co., Ltd., alkalinity 50%) was used as PAC so that the aluminum concentration in the raw water was 0.3 to 0.4 mg / L in terms of Al2O3, and the same granular activated carbon as in Comparative Example 1 was used in the activated carbon filter 66, and the SV of the activated carbon filter 66 was set to 10 (1 / h). In the same manner as in Example 1, the treatment was continuously performed using the ultrafiltration device 65, the activated carbon filter 66, and the reverse osmosis membrane device 64 in sequence. In this comparative example, the raw water after adding low alkalinity PAC and stirring was sampled, and 80 ml of the raw water was passed through a membrane with a nominal pore size of 0.2 μm (size 47 mmφ), and the particles captured by the membrane were observed. As a result, particles of about 1 to 10 μm were observed. The elemental composition of the particles was confirmed by EDX, and the results showed that Al was contained. Furthermore, when the same amount of water was passed through a membrane with a nominal pore size of 0.45 μm (47 mmφ), a sudden pressure difference was generated. From the above results, it was confirmed that, although fine flocs were formed, coarse aggregates with a size of 0.45 μm or more were also formed.

[0074] The types and basicities of PAC used in Examples 1 and 2 and Comparative Examples 1 to 3 are shown in Table 1. Figure 7 The graph shows the change over time of the permeate flux (flow rate) in the reverse osmosis membrane device 64 .

[0075]

Table 1

[0076] In Examples 1 and 2 and Comparative Examples 1 to 3, the free chlorine concentration and turbidity of the permeate water (treated water) of the activated carbon filter device 66 after 5 years of water flow were investigated. The results are shown in Table 1. In addition, for Example 1 and Comparative Example 1, the relationship between the space velocity (SV) in the activated carbon filter device 66 after 5 years of water flow and the turbidity and free chlorine concentration of the permeate water of the activated carbon filter device 66 was investigated. The results are shown in Table 1. Figure 8 , 9 .

[0077] According to the above-mentioned embodiments and comparative examples, it can be seen that by using high-alkalinity PAC to make suspended matter into microflocculates and then filtering with spherical activated carbon, the reduction in the permeation flux of the reverse osmosis membrane device 64 in the rear stage can be significantly suppressed. It can also be seen that when spherical activated carbon is used, although the space velocity of the activated carbon filtration device is greater than that of granular activated carbon, it can still exert sufficient free chlorine removal performance. In addition, it can be seen that compared with the case of using granular activated carbon, the use of spherical activated carbon can not only remove free chlorine with high accuracy for a long time, but also suppress turbidity to a low level.

[0078] (Examples 3 to 5) In this example, the types of reverse osmosis membrane devices and the degree of clogging difficulty of the reverse osmosis membranes were investigated. Disassemble the reverse osmosis membrane modules shown below and take out the reverse osmosis membranes respectively, with an effective membrane area of ​​23.7 cm 2 Cut out the flat membrane. Load film: TM710 manufactured by Toray Industries, Inc. Positively charged membrane: ES10C manufactured by Nitto Denko. Neutral charged membrane: LFC3-LD-4040 manufactured by Nitto Denko.

[0079] Fig.10 A batch test apparatus 9 used in this example is schematically shown. Fig.10 The batch test apparatus shown in the figure includes: a container 91 for containing test water 92; a test membrane 93 provided at an opening at the bottom of the container 91; a measuring cylinder 94 for containing permeated water W filtered through the test membrane 93; a nitrogen gas cylinder 96 for supplying nitrogen into the container 91 and pressurizing it; and a pressure gauge 95. In this embodiment, the flat membrane cut out in the above-mentioned method was provided as the test membrane 93 of the batch test apparatus 9, and water flow tests were performed respectively.

[0080] The water flow conditions are as follows. Test water (raw water): water permeated through the ultrafiltration device 65 of Example 1. Test water volume (raw water volume): 300 ml. Filtration concentration ratio: 10 times. Water pressure (pressure after the pressure reducing valve of the gas cylinder 96 reduces pressure): 15kgf / cm 2 . Water passing method: The container 91 was pressurized by the pressure of the gas cylinder 96, and the test water 92 was stirred by a stirrer (not shown) while collecting the permeated water that passed through the test membrane 93. After obtaining 270 ml of permeated water, the remaining part of the test water was discharged from the test water discharge valve (not shown). After that, 300 ml of test water was replenished and the water was passed again. This operation was repeated 20 times to confirm the clogging.

[0081] The clogging rate was determined as follows by measuring the amount of permeated water per unit time using a measuring cylinder 94 . A: The 20th water flow rate is 95% of the initial water flow rate. B: The 20th water flow rate is greater than 90% and less than 95% of the initial water flow rate. C: The 20th water flow rate is 80% or more and 90% or less of the initial water flow rate.

[0082]

Table 2

[0083] According to the above results, it can be seen that the reverse osmosis membrane device with a charged membrane is not easily clogged by microflocs. It should be noted that the test water (raw water) used in Examples 3 to 5 is the permeate water of the ultrafiltration membrane, so the particulate components in the raw water are removed. Therefore, it can be considered that the reduction in the flow rate of the reverse osmosis membrane is not caused by the particulate components in the water, but by the influence of the microflocs remaining in the permeate water of the ultrafiltration membrane. Here, since the coagulant used to form flocs is usually positively charged, it is expected that the negatively charged membrane is more likely to be clogged, but it is an unexpected result that the negatively charged membrane is less likely to be clogged.

[0084] According to the experimental examples, embodiments and comparative examples described above, it can be seen that according to the manufacturing device and manufacturing method of pure water of the embodiment, since high-alkalinity PAC is added to raw water and then reverse osmosis membrane treatment is performed, suspended solids can be fully removed, and the reduction in the permeation flux of the reverse osmosis membrane device can be significantly suppressed. As a result, high-purity pure water and ultrapure water can be manufactured efficiently and for a long time, so the manufacturing device and manufacturing method of pure water of the embodiment are suitable for mass production of pure water or ultrapure water.

Claims

1. A method for producing pure water, comprising: A step of adding high-basicity polyaluminium chloride to raw water to obtain first treated water; a step of subjecting the first treated water to activated carbon treatment by passing it through spherical activated carbon to obtain second treated water; and A reverse osmosis membrane step of subjecting the second treated water to reverse osmosis membrane treatment.

2. The manufacturing method according to claim 1, wherein: High-alkalinity polyaluminium chloride is added to the raw water, thereby obtaining first treated water containing microflocs.

3. The manufacturing method according to claim 1 or 2, wherein: The turbidity of the raw water is greater than or equal to 1 NTU and less than or equal to 100 NTU.

4. The manufacturing method according to claim 1 or 2, wherein: The basicity of the polyaluminium chloride is greater than 75%.

5. The manufacturing method according to claim 1 or 2, wherein: The polyaluminium chloride comprises hydroxyaluminium chloride, The amount of the hydroxyaluminum chloride added is 0.25 mg / L or more and 5 mg / L or less relative to the raw water in terms of the concentration of aluminum oxide Al 2 O 3 .

6. The manufacturing method according to claim 1 or 2, wherein: The spherical activated carbon has an average particle size of 0.5 mm or more and 4.0 mm or less.

7. The manufacturing method according to claim 1 or 2, wherein: include: A filtration step, filtering the first treated water, wherein the filtration treatment includes one or more selected from sand filtration, multi-media filter MMF filtration, microporous filtration MF device and ultrafiltration, The treated water obtained in the filtration step is subjected to the activated carbon treatment.

8. The manufacturing method according to claim 7, wherein: The turbidity of the treated water obtained in the filtration step is 0.01 NTU or more and 0.17 NTU or less.

9. A method for producing pure water, comprising: A step of supplying high-alkalinity polyaluminium chloride to raw water to obtain first treated water; The process of subjecting the first treated water to activated carbon treatment by passing it through spherical activated carbon to obtain second treated water; a reverse osmosis membrane process for performing reverse osmosis membrane treatment on the second treated water; UV oxidation process; as well as Ion exchange process.

10. A device for producing pure water, comprising: A raw water supply device for supplying raw water; A polyaluminium chloride supply device is used to add high-alkalinity polyaluminium chloride to the raw water; An activated carbon filtration device is used to contact the first treated water generated by adding high-alkalinity polyaluminium chloride to the raw water with the spherical activated carbon; as well as The reverse osmosis membrane device performs reverse osmosis membrane treatment on the second treated water generated in the activated carbon filtration device.

11. The manufacturing device according to claim 10, wherein: The turbidity of the raw water is greater than or equal to 1 NTU and less than or equal to 100 NTU.

12. The manufacturing device according to claim 10 or 11, wherein: The basicity of the high-basicity polyaluminium chloride is greater than 75%.

13. The manufacturing device according to claim 10 or 11, wherein: The polyaluminium chloride comprises hydroxyaluminium chloride, The polyaluminium chloride supply device supplies aluminium hydroxy chloride in an amount of 0.25 mg / L or more and 5 mg / L or less in terms of the concentration of aluminium oxide Al 2 O 3 relative to the raw water.

14. The manufacturing device according to claim 10 or 11, wherein: Between the polyaluminium chloride supply device and the activated carbon filter device, there is one or more selected from a sand filter device, a multi-media filter MMF filter device, a microporous filter MF device and an ultrafiltration device.

15. A pure water production system, comprising: The device for producing pure water as claimed in claim 14; UV oxidation devices; and Ion exchange device.

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