Production method and production device of water for pure water, pure water production method and pure water production system

Abstract

To provide a production method and a production device of water for pure water capable of efficiently removing suspended substances in raw water, while capable of preventing a transmission flow rate of a reverse osmosis membrane device from lowering by residual aluminum for a long period of time, and also to provide a pure water production method and a production system.SOLUTION: A production method of water for pure water includes: a step of adding a poly aluminum chloride of high alkalinity to raw water to obtain first treatment water; a step of passing the first treatment water to spherical active carbon and applying an active carbon treatment to obtain second treatment water; and a reverse osmosis membrane step of applying a reverse osmosis membrane treatment to the second treatment water.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for producing water for pure water, and a method and system for producing pure water. [Background technology]

[0002] In water treatment such as the production of industrial water from river water, well water, and lake water, and in wastewater treatment, coagulation treatment is carried out to remove suspended solids such as suspended solids, dissolved organic matter, and colloidal silica. In this coagulation treatment, polyaluminum chloride (PAC) is used as a coagulant. PAC is popular because it is inexpensive and has a wide pH range for coagulation.

[0003] A known method of using PAC in the production of industrial water and wastewater treatment is to mix PAC, which has a relatively low basicity (75% or less), with wastewater to form coarse aggregates of suspended solids, and then remove these coarse aggregates by dead-end filtration (see, for example, Patent Document 1). However, this method requires a slow sand filtration device, and therefore requires a large site area for the installation of the slow sand filtration device. For example, if this method is used on a 100m 3 To treat raw water of 10000ml / h, a circular slow sand filtration device with a radius of 12 m would be required. In addition, no facilities for further treatment of the treated water are envisaged. Therefore, it is difficult to apply this method to anything other than very limited facilities such as water purification plants, and it is difficult to apply it to the production of pure water or ultrapure water used in the manufacturing processes of semiconductors, liquid crystals, etc.

[0004] In the production of pure water or ultrapure water, raw water such as tap water or industrial tap water is passed through a membrane treatment device such as a reverse osmosis membrane device (RO) or an ultrafiltration device (UF), and then treated using a combination of an ion exchange resin device, an ultraviolet irradiation device, etc. Tap water, industrial water, etc. are treated with PAC to remove suspended solids from the raw water before being supplied, but the raw water contains residual aluminum derived from the PAC, and a method of removing this using an iron-based inorganic polymer flocculant is also known. This is because residual aluminum in the raw water adheres to the membrane of a reverse osmosis membrane device or the like, significantly reducing the permeation flux of the membrane treatment device (see, for example, Patent Document 2).

[0005] A microfloc method using PAC is also used. This is a method in which PAC is directly injected into tap water or industrial tap water, or the water is rapidly stirred after injection to form microflocs, which are then removed by filtration without precipitation treatment (see, for example, Patent Document 3). However, in this method, if a reverse osmosis membrane device is installed in the downstream, the permeation flux of the reverse osmosis membrane device will be significantly reduced, as described above. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2012-086149 A [Patent Document 2] JP 2008-86966 A [Patent Document 3] JP 2022-165279 A Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, the use of PAC in the production of pure water or ultrapure water has the problem of a decrease in the permeation flux of the reverse osmosis membrane device due to adhesion of residual aluminum in the water to the membrane. However, the method of removing residual aluminum using an iron-based inorganic polymer flocculant has the problems of increased costs and environmental load due to the increased amount of chemical used.

[0008] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method and apparatus for producing pure water that can efficiently remove suspended solids from raw water and suppress a decrease in the permeation flux of a reverse osmosis membrane device caused by residual aluminum over a long period of time. Another object of the present invention is to provide a method and system for producing pure water that can efficiently remove suspended solids from raw water and suppress the permeation flux of a reverse osmosis membrane device caused by residual aluminum, thereby producing high-quality pure water over a long period of time. [Means for solving the problem]

[0009] [1] A method for producing water for pure water, comprising the steps of: A step of obtaining a first treated water by adding high basicity polyaluminum chloride to the raw water; A step of passing the first treated water through spherical activated carbon to perform activated carbon treatment to obtain a second treated water; and a reverse osmosis membrane process for treating the second treated water using a reverse osmosis membrane. [2] The method according to [1], wherein a first treated water containing microflocs is obtained by adding high basicity polyaluminum chloride to the raw water. [3] The manufacturing method described in [1] or [2], wherein the turbidity of the raw water is 1 NTU or more and 100 NTU or less.

[0010] [4] The method according to any one of [1] to [3], wherein the basicity of the polyaluminum chloride is greater than 75%. [5] The polyaluminum chloride comprises aluminum chloride pentahydroxide; The manufacturing method according to any one of [1] to [4], wherein the amount of the aluminum chloride pentahydroxide added is an amount equivalent to a concentration of 0.25 mg / L or more and 5 mg / L or less in terms of aluminum oxide (Al2O3) relative to the raw water. [6] The 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 filtration step of filtering the first treated water using one or more filters selected from sand filtration, multimedia filter (MMF) filtration, microfiltration (MF) equipment, and ultrafiltration; The process according to any one of [1] to [6], wherein the treated water obtained in the filtration step is treated with the activated carbon. [8] The 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 the steps of: supplying high-basicity polyaluminum chloride to raw water to obtain a first treated water; A step of passing the first treated water through spherical activated carbon to perform activated carbon treatment to obtain a second treated water; a reverse osmosis membrane process for treating the second treated water with a reverse osmosis membrane; A manufacturing method comprising an ultraviolet oxidation step and an ion exchange step in this order.

[0012]

[10] A pure water manufacturing apparatus comprising: a raw water supply device for supplying raw water; a polyaluminum chloride supplying device for adding high basicity polyaluminum chloride to raw water; an activated carbon filtration device that brings a first treated water produced by adding high-basicity polyaluminum chloride to raw water into contact with spherical activated carbon; and a reverse osmosis membrane device that performs reverse osmosis treatment on the second treated water produced in the activated carbon filtration device.

[11] The manufacturing apparatus described in

[10] , wherein the turbidity of the raw water is 1 NTU or more and 100 NTU or less.

[12] The manufacturing apparatus according to

[10] or

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

[13] The manufacturing apparatus according to any one of

[10] to

[13] , wherein the polyaluminum chloride contains aluminum chloride pentahydroxide, and the polyaluminum chloride supplying device supplies aluminum chloride pentahydroxide to raw water in an amount of 0.25 mg / L or more and 5 mg / L or less, calculated as an aluminum oxide (Al2O3) concentration.

[14] Between the polyaluminum chloride supply device and the activated carbon filtration device, there is provided one or more devices selected from a sand filtration device, a multimedia filter (MMF) filtration device, a microfiltration (MF) device and an ultrafiltration device; The manufacturing apparatus according to any one of

[10] to

[14] .

[15] An apparatus for producing pure water according to

[14] , A pure water production system comprising an ultraviolet oxidation device and an ion exchange device in this order. The symbol "~" indicates a numerical range including the numerical values ​​before and after it. Effect of the Invention

[0013] According to the present invention, it is possible to provide a method and apparatus for producing pure water that can efficiently remove suspended solids from raw water and suppress a decrease in the permeation flux of a reverse osmosis membrane device caused by residual aluminum. Furthermore, the present invention can provide a pure water production method and system that can efficiently remove suspended solids from raw water and suppress a decrease in the permeation flux of a reverse osmosis membrane device caused by residual aluminum, thereby producing high-quality pure water over a long period of time. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating a manufacturing apparatus used in a method for manufacturing pure water according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a production apparatus further including a mixing tank in addition to the production apparatus shown in FIG. [Diagram 3] FIG. 13 is a schematic diagram showing a production apparatus used in a method for producing pure water according to another embodiment. [Figure 4]FIG. 4 is a schematic diagram showing a production apparatus further including a mixing tank in addition to the production apparatus shown in FIG. 3. [Diagram 5] 1 is a diagram showing a schematic diagram of a pure water production system using an apparatus for producing pure water according to an embodiment; [Figure 6] FIG. 2 is a schematic diagram showing a pure water production apparatus used in the examples. [Figure 7] 1 is a graph showing the change over time in permeation flux of a reverse osmosis membrane device. [Figure 8] 7 is a graph showing 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 shown in FIG. 6 for five years. [Figure 9] 7 is a graph showing the relationship between space velocity (SV) and free chlorine concentration in an activated carbon filtration device after water has been passed through the device shown in FIG. 6 for five years. [Figure 10] FIG. 2 is a schematic diagram showing a batch-type test apparatus used in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described. Fig. 1 shows a schematic diagram of a production apparatus 1 used in the method for producing pure water of this embodiment. The production apparatus 1 includes a raw water supply device 11 for supplying raw water, a polyaluminum chloride supply device 12 for supplying high basicity polyaluminum chloride (hereinafter also referred to as "high basicity PAC"), a raw water transfer pipe 13 for transferring raw water, and an activated carbon filtration device 17 for passing the raw water (first treated water) to which the high basicity PAC has been added through spherical activated carbon. The production apparatus 1 further includes a reverse osmosis membrane device 14 for performing reverse osmosis membrane treatment on the second treated water obtained in the activated carbon filtration device 17.

[0016] The method for producing pure water in the embodiment using the production apparatus 1 is as follows. First, raw water is supplied from the raw water supply device 11 into the raw water transfer pipe 13. The raw water is natural water such as city water, urban water such as industrial water, river water, lake water, groundwater, and well water. The quality of the raw water is, for example, turbidity of 1 NTU to 100 NTU, suspended solids (SS) of 5 mg / L to 500 mg / L, total organic carbon (TOC) of 0.5 mg / L to 7 mg / L, aluminum concentration of 0.01 mg / L to 5 mg / L, residual chlorine concentration of 0.1 mg / L to 2 mg / L as Cl2, and pH of 4 to 9. Note that residual chlorine may be added to the raw water during transportation through the raw water transfer pipe 13. The raw water supply device 11 includes, for example, a raw water tank for storing raw water and a feed water pump for transferring the raw water in the raw water tank, and the feed water pump supplies the raw water in the raw water tank into the raw water transfer pipe 13. Depending on the quality of the raw water, a prefilter (not shown) may be installed as a pretreatment device to pretreat the raw water before the addition of the high basicity PAC. Also, an acid or alkali injection facility may be installed to adjust the pH of the raw water as necessary.

[0017] Next, the polyaluminum chloride supplying device 12 adds the high basicity PAC to the raw water transfer pipe 13. The polyaluminum chloride supplying device 12 is equipped with, for example, a chemical tank for storing the high basicity PAC and a chemical injection pump for adding the high basicity PAC in the chemical tank to the raw water transfer pipe 13, and the chemical injection pump measures the high basicity PAC in the chemical tank so as to achieve a predetermined concentration and adds it to the raw water transfer pipe 13.

[0018] When a PAC with a lower basicity than the high basicity PAC (hereinafter referred to as "low basicity PAC") is added to raw water, the low basicity PAC interacts with suspended solids in the raw water, coagulates, and generates fine and coarse flocs. These flocs can be precipitated and separated using a coagulation and sedimentation tank, but aluminum ions are likely to leak from the flocs, or nanoflocs, which are smaller than microflocs, are formed in large quantities. Therefore, when treated water to which a low basicity PAC has been added is treated with a reverse osmosis membrane, aluminum in the treated water adheres to the surface of the reverse membrane, which makes it very likely that the reverse osmosis membrane will become clogged, and the permeation flux of the reverse osmosis membrane device will decrease early.

[0019] In contrast, in the production method of this embodiment, a high basicity PAC is supplied to the raw water, and the high basicity PAC interacts with suspended solids in the raw water to form microflocs. Through the process of these microflocs, adhesion of residual aluminum to the membrane of the reverse osmosis membrane device 14 is significantly reduced, and the performance of the reverse osmosis membrane device can be maintained for a long period of time.

[0020] Microflocs are aggregates of suspended solids and high basicity PAC with sizes of about 1 to 10 μm. High basicity PAC easily forms microflocs, but does not easily form coarse flocs or flocs (nano flocs) that are finer than microflocs. Aluminum ions do not easily leak out of microflocs, so by passing through them, reverse osmosis membrane blockage can be prevented for a long period of time.

[0021] The high basicity PAC of this embodiment contains polyaluminum chloride represented by the following chemical formula (1). The high basicity PAC of this embodiment has a basicity of preferably more than 75%, more preferably more 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] The high basicity PAC can be produced, for example, by the method described in Japanese Patent No. 4104773. As the high basicity PAC, only one type may be used, or two or more types may be used in combination. When two or more types are used in combination, the basicity of the two or more high basicity PACs may be the same or different, but the basicity of each of the high basicity PACs used is preferably greater than 75%, more preferably greater than 83%.

[0023] As the high basicity PAC, it is preferable to use aluminum chloride pentahydroxide (Al2Cl(OH)5). Aluminum chloride pentahydroxide is a polyaluminum chloride with n=5 and m=1 in the above chemical formula (1), and has a basicity of 83.3%. Aluminum chloride pentahydroxide is more likely to form more homogeneous microflocs. This is thought to be due to the high basicity and small molecular weight of aluminum chloride pentahydroxide.

[0024] The amount of high basicity PAC is preferably 0.125 mg / L as Al2O3 or more per turbidity of 1 NTU in the raw water. Specifically, the amount of high basicity PAC is preferably 0.25 mg / L as Al2O3 or more and 5 mg / L as Al2O3 or less per amount of raw water, and more preferably 0.3 mg / L as Al2O3 or more and 3 mg / L as Al2O3 or less per amount of raw water. In particular, when aluminum chloride pentahydroxide (Al2Cl(OH)5) is used as the high basicity PAC, the amount of aluminum chloride pentahydroxide is preferably 0.25 mg / L as Al2O3 or more and 2 mg / L as Al2O3 or less per total amount of raw water. Even if the amount of high basicity PAC is small as described above, it is possible to micro-flocculate the suspension in the raw water. In addition, since the high basicity PAC functions even in a small amount as described above, it is easy to prevent clogging of the reverse osmosis membrane device 14 in the downstream stage. The notation "as Al2O3" indicates that the value is converted into aluminum oxide (Al2O3) concentration. If necessary, a polymer flocculant or other inorganic flocculant may be added as a flocculation-promoting assistant just before or just after the addition of the high basicity PAC.

[0025] 2 shows a schematic diagram of a pure water manufacturing apparatus 2 having a mixing tank 23 for adding high basicity PAC to raw water. The manufacturing apparatus 2 differs from the above-mentioned manufacturing apparatus 1 in that it has a mixing tank 23 in the path of the raw water transfer pipe 13, but the other configurations are the same. In this embodiment, detailed explanations of configurations and functions common to the manufacturing method using the manufacturing apparatus 1 will be omitted.

[0026] In the production apparatus 2, raw water is supplied from the raw water supply device 11, and the high basicity PAC is supplied from the polyaluminum chloride supply device 12, into the mixing tank 23. In the mixing tank 23, the suspension in the raw water interacts with the high basicity PAC to form microflocs. In this case, the order of supplying the raw water and the high basicity PAC into the mixing tank 23 may be either first or simultaneously, but it is preferable that the high basicity PAC is added to the mixing tank 23 to which the raw water has been supplied.

[0027] In the manufacturing apparatus 2 shown in FIG. 2, the raw water and the high basicity PAC are rapidly stirred in the mixing tank 23, which makes it easier to form more homogeneous microflocs without generating nanoflocs. The stirring speed is, for example, 150 s in terms of G value. ー1 More than 150 to 250 s is preferable. ー1 More preferably, 250s ー1 It is more preferable that the stirring time is 2 minutes or more, preferably 3 minutes or more, and more preferably 6 minutes or more. The larger the G value of the rapid stirring, the shorter the stirring time can be.

[0028] Next, the first treated water containing the microflocs is supplied to the activated carbon filtration device 17 of Fig. 1 or 2 and filtered by activated carbon. As a result, the second treated water is obtained as the permeate of the activated carbon filtration device 17.

[0029] The activated carbon filtration device 17 has spherical activated carbon as a filter material. The spherical activated carbon is, for example, spherical activated carbon with a highly uniform size, with an average particle diameter of about 0.5 mm to 4.0 mm. The present inventors have found that by passing the first treated water containing microflocs through spherical activated carbon to treat it, the decrease in the permeation flux of the downstream reverse osmosis membrane device 14 is significantly reduced compared to when granular activated carbon or powdered activated carbon is used. In addition, the use of spherical activated carbon allows the residual chlorine removal performance to be maintained for a long period of time compared to when granular activated carbon or powdered activated carbon is used, and therefore membrane deterioration of the downstream reverse osmosis membrane device 14 is also suppressed. In addition, the use of spherical activated carbon provides excellent recovery of the water flow differential pressure of the spherical activated carbon filtration device after backwashing, which leads to a reduction in the frequency of backwashing and therefore a reduction in the amount of washing water. The average particle diameter of the spherical activated carbon can be evaluated in accordance with JIS K 1474. That is, a particle size cumulative line diagram of spherical activated carbon is created from the results obtained from the operation of JIS K 1474. A horizontal line is drawn on the vertical axis from the intersection point of the vertical line at the 50% point on the horizontal axis and the particle size cumulative line diagram, and the mesh size (mm) of the sieve indicated at the intersection point is determined. This mesh size value is regarded as the average particle size of the spherical activated carbon. Note that granular activated carbon is, for example, activated carbon crushed into granules, and powdered activated carbon is, for example, activated carbon crushed into powder of 0.5 μm to 30 μm.

[0030] The hardness of the spherical activated carbon is preferably 90 or more, more preferably 93 or more, and even more preferably 94 or more. The hardness of the spherical activated carbon is, for example, 99 or less. The greater the hardness of the spherical activated carbon, the longer it can maintain the residual chlorine removal performance, which contributes to maintaining the permeation flux of the downstream reverse osmosis membrane device. The uniformity coefficient of the spherical activated carbon is preferably 2.0 or less, more preferably 1.8 or less, and even more preferably 1.4 or less. The uniformity coefficient of the spherical activated carbon is usually greater than 1.0. The smaller the uniformity coefficient, the easier it is to recover the water flow differential pressure after backwashing, and the more suitable it is for long-term water treatment. The hardness and uniformity coefficient of the spherical activated carbon can be evaluated in accordance with JIS K 1474.

[0031] As the spherical activated carbon, commercially available products can be used, such as the Spherical Shirasagi series manufactured by Osaka Gas Chemicals Co., Ltd. and BAC manufactured by Kureha Corporation.

[0032] In the manufacturing method of this embodiment, by using the above-mentioned spherical activated carbon, water can be passed through the activated carbon filtration device 17 at a space velocity (SV) of preferably 5 to 100 (1 / h), and more preferably at an SV of 30 to 100 (1 / h). In particular, since the space velocity can be increased to SV of 30 to 100 (1 / h), sufficient water quality can be obtained with a small amount of activated carbon used, and treated water with low turbidity and low residual chlorine concentration can be stably produced while making the activated carbon filtration device 17 compact.

[0033] An independent type filtration device can be used as the activated carbon filtration device 17. As the independent type filtration device, a cartridge type activated carbon filtration device or a module type activated carbon filtration device can be used, as in the filtration section described later. The independent type activated carbon filtration device 17 is effective in preventing blockage of the reverse osmosis membrane device 14, since nanoflocs are less likely to flow out to the downstream side. In particular, when the method of this embodiment is used to produce ultrapure water for manufacturing semiconductors, etc., by using the independent type activated carbon filtration device 17, it is possible to continue producing ultrapure water without stopping the device by installing multiple independent type activated carbon filtration devices 17 in parallel, performing regeneration such as backwashing or module replacement for each of the multiple devices, and continuing operation with other devices (so-called merry-go-round operation).

[0034] The water quality of the second treated water thus obtained 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 as Cl2.

[0035] Next, the second treated water filtered through the spherical activated carbon is supplied to the reverse osmosis membrane device 14 and treated with a reverse osmosis membrane. In order to suppress a decrease in permeation flux in the reverse osmosis membrane device 14, the water supply pressure to the reverse osmosis membrane device 14 at this time is preferably 0.5 MPa to 3 MPa, and the water recovery rate in the reverse osmosis membrane device 14 is preferably 75% to 95%. A scale inhibitor or bacteriostatic agent may be added to the second treated water as appropriate immediately before it is supplied to the reverse osmosis membrane device 14.

[0036] The reverse osmosis membrane device 14 may be any of ultra-low pressure type, ultra-low pressure type, low pressure type, medium pressure type, and high pressure type reverse osmosis membrane devices. The reverse osmosis membrane provided in the reverse osmosis membrane device 14 is preferably a spiral type reverse osmosis membrane made of aromatic polyamide as a constituent material. The reverse osmosis membrane device 14 may be a positively charged membrane with a positively charged surface, a negatively charged membrane with a negatively charged surface, or an uncharged membrane with an uncharged surface, among which a negatively charged membrane is preferable because it is less likely to cause clogging due to flocs of the reverse osmosis membrane. The reverse osmosis membrane device 14 is preferably a negatively charged membrane of ultra-low or low pressure type. As a reverse osmosis membrane device having a negatively charged membrane of ultra-low or low pressure type, commercially available products may be used, for example, "ES20" manufactured by Nitto Denko Corporation, "SU series", "TM series", "TBW series" manufactured by Toray Industries, Inc., and "BW series" manufactured by Dow.

[0037] A permeate transfer pipe 15 is connected to the permeation side of the reverse osmosis membrane device 14, and the permeate is sent to a subsequent stage via the transfer pipe 15. A concentrated water discharge pipe 16 is connected to the concentration side of the reverse osmosis membrane device 14. The concentrated water can be discharged to the outside of the production apparatus 1 via the discharge pipe 16 or returned to the upstream stage of the reverse osmosis membrane device 14 for reprocessing. The quality of the permeate thus obtained is, for example, a turbidity of 0.01 NTU to 0.2 NTU, an aluminum concentration of 0 mg / L to 0.002 mg / L, a pH of 5.9 to 6.5, and a conductivity of 3 μS / cm to 6 μS / cm.

[0038] Next, another embodiment of the present invention will be described. Fig. 3 shows a schematic diagram of a manufacturing apparatus 3 used in the method for manufacturing pure water of this embodiment. The manufacturing apparatus 3 differs from the manufacturing apparatus 1 shown in Fig. 1 in that a filtration section 31 is provided between the location of the polyaluminum chloride supply device 12 and the activated carbon filtration device 17 in the route of the raw water transfer pipe 13, but the other configurations are the same. In this embodiment, detailed descriptions of the configurations and functions common to the manufacturing method using the manufacturing apparatus 1 will be omitted.

[0039] A method for producing pure water according to an embodiment using the production apparatus 3 shown in Fig. 3 is as follows. First, raw water is supplied from a raw water supply device 11 into a raw water transfer pipe 13. Next, a high basicity PAC is added by a polyaluminum chloride supply device 12 into the raw water transfer pipe 13 to which the raw water has been supplied. A preferred embodiment of the high basicity PAC used here is the same as the production method using the production apparatus 1 shown in Fig. 1.

[0040] By supplying raw water and high basicity PAC into the raw water transfer pipe 13, the suspension in the raw water and the high basicity PAC interact with each other to form microflocs. By passing through these microflocs, adhesion of residual aluminum to the membrane of the reverse osmosis membrane device 14 is significantly reduced, and the performance of the reverse osmosis membrane device can be maintained for a long period of time. The first treated water containing microflocs in the raw water transfer pipe 13 is then supplied to the filtration section 31 and the activated carbon filtration device 17 in that order. At this time, by providing a feed water pump in the route of the raw water transfer pipe 13, the first treated water can be supplied to the filtration section 31 by the feed water pump. In this embodiment, since a mixing tank is not used, the device is compact, and it is easy to install in a semiconductor manufacturing factory, etc. Note that if an in-line mixer or the like is installed in the transfer pipe 13 after the high basicity PAC is supplied in order to promote mixing, the formation of microflocs can be more reliably performed, and clogging of the equipment in the subsequent stages can be more suppressed.

[0041] The filtration unit 31 includes one or more filtration devices selected from a sand filtration device, a multimedia filter (MMF) filtration device, an ultrafiltration device, and a microfiltration (MF) device, and filters the first treated water. This removes mainly suspended microflocs from the water, and the third treated water is obtained. The obtained treated water is then supplied to the activated carbon filtration device 17.

[0042] The sand filter has, for example, supporting gravel or sand (filter sand) as a filter material. A multimedia filter (MMF) filtration device is equipped with a three-layer filter material in which, for example, anthracite, sand, and garnet are layered from the bottom in order of particle size. The ultrafiltration (UF) device is provided with an ultrafiltration membrane having a nominal pore size of 0.001 to 0.1 μm as a filter material, and may be of either dead-end filtration type or cross-flow filtration type. The ultrafiltration (UF) device is preferably an external pressure type ultrafiltration device using a hollow fiber membrane. The microfiltration (MF) device is equipped with a microfiltration membrane having a nominal pore size of, for example, 0.1 to 5 μm, and is capable of performing dead-end filtration.

[0043] The filtration unit 31 may have one type of filtration device selected from the sand filtration device, multimedia filter (MMF) filtration device, microfiltration (MF) device, and ultrafiltration (UF) device, or a combination of two or more types, depending on the raw water quality. When two or more types are combined, it is preferable to arrange the sand filtration device or multimedia filter (MMF) filtration device on the upstream side, and the microfiltration (MF) device or ultrafiltration device on the downstream side. It is more preferable that the filtration unit 31 only has an ultrafiltration device. By providing the filtration unit 31, microflocs in the first treated water can be removed with high accuracy, which reduces the load on the reverse osmosis membrane device 14 in the subsequent stage, making it possible to obtain high-quality permeated water for a long period of time.

[0044] In the manufacturing apparatus 3 shown in FIG. 3, the filtration unit 31 is an independent filtration unit having an independent filtration device. Examples of the independent filtration device include a cartridge type filtration device and a module type filtration device. The cartridge type filtration device is configured, for example, to accommodate a cartridge of filtration material in a housing, connect piping to a water inlet and a drainage port opened in the housing, and pass water through the cartridge through the opening. The cartridge type filtration device has the advantage that only the cartridge can be replaced when the filtration material deteriorates. The module type filtration device is configured such that the filtration material is provided inside the housing, and water is passed through the filtration material by connecting the module to piping. The module type filtration device has the advantage that when the filtration material deteriorates, the entire module can be replaced, and the deteriorated filtration material can be washed for each module. The independent filtration unit 31 is effective in preventing blockage of the reverse osmosis membrane device 14 because there is little outflow of nanoflocs to the downstream side. In particular, when the method of this embodiment is used to produce ultrapure water for manufacturing semiconductors and the like, by using an independent filtration unit 31, multiple independent filtration units 31 can be installed in parallel and regenerated by backwashing or by replacing modules one by one of the multiple units (so-called merry-go-round operation), making it possible to continue producing ultrapure water without stopping the equipment.

[0045] The quality of the treated water (treated water from the filtration unit 31) thus obtained is, for example, turbidity of 0.01 NTU to 0.4 NTU, preferably 0.01 NTU to 0.17 NTU, free chlorine concentration of 0.01 mg / L to 0.1 mg / L as Cl2, aluminum concentration of 0.01 mg / L to 0.04 mg / L, pH of 7.2 to 8.3, and electrical conductivity of 140 μS / cm to 270 μS / cm. In the method of the present embodiment, by using the high basicity PAC, stable and homogeneous microflocs can be formed regardless of the pH value of the raw water to which the high basicity PAC is added, so that addition of a pH adjuster is not required and the amount of chemicals used can be reduced. Therefore, although the pH of the third treated water (treated water from the filtration unit 31) may fluctuate, the aluminum concentration remains low and stable.

[0046] 4 shows a schematic diagram of a pure water production apparatus 4 having a mixing tank 23 for adding high basicity PAC to raw water, and a filtration section 31. The production apparatus 4 differs from the production apparatus 3 shown in FIG. 3 in that it has a mixing tank 23 in the path of the raw water transfer pipe 13, but the other configurations are the same. In this embodiment, detailed explanations of configurations and functions common to the production method using the production apparatus 3 will be omitted.

[0047] In the production apparatus 4, raw water is supplied from the raw water supply device 11, and high basicity PAC is supplied from the polyaluminum chloride supply device 12 into the mixing tank 23. In the mixing tank 23, the suspension in the raw water interacts with the high basicity PAC to form microflocs. In particular, by using the mixing tank 23, the formation of microflocs by the high basicity PAC is sufficiently performed, so that clogging of the downstream equipment is further suppressed. In this case, the order of supplying the raw water and the high basicity PAC into the mixing tank 23 may be either first or simultaneously, but it is preferable that the high basicity PAC is added to the mixing tank 23 to which the raw water has been supplied. As described above, in the method of this embodiment, it is not essential to adjust the pH of the raw water in the mixing tank 23.

[0048] 4 has an independent filtration section 31 that is separate and independent from the mixing tank 23, downstream of the mixing tank 23. The aspect of the independent filtration section 31 is the same as that of the manufacturing apparatus 3 described above.

[0049] As the filtration section 31, a submerged filtration device configured for immersion in a tank can be used. The submerged filtration device configured for immersion in a tank has an advantage that it is submerged in the bottom of the mixing tank 23 and can directly filter the first treated water to which the high basicity PAC has been added without using piping. As the submerged filtration device, an ultrafiltration device or an MMF type filtration device is preferable. In the production apparatus 4 of this embodiment, by forming microflocs in water using the high basicity PAC, it is possible to directly perform filtration treatment without going through precipitation removal in a coagulation sedimentation tank as used for coarse flocs. Therefore, the filtration section 31 can be integrated by immersing it in the mixing tank 23, and the configuration of the entire apparatus can be simplified.

[0050] When a plurality of filtration devices are used in the filtration section 31, only immersion type or only stand-alone type may be used, or immersion type and stand-alone type may be used in combination. In this embodiment, it is preferable to use only stand-alone type filtration devices, and it is more preferable to use stand-alone type ultrafiltration devices. The ultrafiltration membranes that can be provided in the stand-alone ultrafiltration device include hollow fiber membranes, spiral membranes, and flat membranes made of materials such as cellulose acetate, aromatic polyamide, polyvinyl alcohol, polysulfone, and polyvinylidene fluoride. Among these, hollow fiber membranes made of fluorine-based materials such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) are preferable. The filtration membrane provided in the immersion type ultrafiltration device is preferably a flat membrane made of ceramic or a fluorine-based material such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE).

[0051] The first treated water is filtered by the filtration unit 31 in Fig. 3 or 4 to remove microflocs containing suspended matter from the water, and the third treated water is obtained. The third treated water is then treated by the activated carbon filtration device 17 to produce the second treated water, which is then supplied to the reverse osmosis membrane device 14 for treatment.

[0052] Next, a pure water producing system 5 according to an embodiment using the above-mentioned production apparatus 1 will be described with reference to Fig. 5. Fig. 5 is a block diagram showing a schematic configuration of the ultrapure water producing system 5 using the production apparatus 1. In Fig. 5, the production apparatus 1 can be changed to any one of production apparatuses 2 to 4.

[0053] 5, the ultrapure water production system 5 comprises, in this order, 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 by 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 embodiment described above, and, if necessary, a prefilter, a heat exchanger for temperature adjustment, and the like.

[0055] The ultrapure water manufacturing system 5 is equipped with a tank TK1 downstream of the pretreatment system 50, and the water to be treated that has been pretreated by the pretreatment system 50 is introduced into the tank TK1, temporarily stored therein, and then supplied to the primary pure water system 51.

[0056] The primary pure water system 51 produces primary pure water by removing organic matter, ion components, and dissolved gases from the pretreated water. The primary pure water system 51 includes an ultraviolet oxidation device (TOC-UV) 513 and an ion exchange device 514 in this order.

[0057] The ultraviolet oxidation device 513 has an ultraviolet lamp that emits ultraviolet rays with a wavelength of, for example, about 185 nm and ultraviolet rays with a wavelength of about 254 nm, and oxidizes and decomposes the total organic carbon (TOC) in the water to be treated by irradiating the water with ultraviolet rays from the ultraviolet lamp. The ultraviolet rays emitted by the ultraviolet oxidation 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 oxidation device 513 of the primary pure water system can be appropriately changed depending on 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 electric deionization 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 double bed ion exchange resin device can be appropriately combined and used according to the required water quality. The cation exchange resin used in the cation exchange resin device may be a strong acid cation exchange resin or a weak acid cation exchange resin. The anion exchange resin used in the anion exchange resin device may be a strong basic anion exchange resin or a weak basic anion exchange resin. As the ion exchange resin, a boron adsorbent ion exchange resin may 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 this order, downstream of a primary pure water system 51. The primary pure water produced in 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 oxidation device (TOC-UV) 521, a non-regenerative polisher (Polisher) 522, a membrane degasser (MDG) 523, and an ultrafiltration device (UF) 524.

[0061] The ultraviolet oxidation device 521 in the secondary pure water system 52 has the same configuration as the ultraviolet oxidation device 513 in the primary pure water system 51. The non-regenerative polisher 522 is a mixed-bed ion exchange resin device in which a strong acid cation exchange resin and a strong basic anion exchange resin are mixed and filled in a container such as a cylinder. The non-regenerative polisher 522 adsorbs and removes ion components generated by the ultraviolet oxidation device 521 decomposing organic matter.

[0062] The membrane degassing device 523 removes dissolved gases through a degassing membrane. The membrane degassing device 523 removes trace amounts of dissolved oxygen in the primary pure water to reduce the dissolved oxygen concentration, for example, to about 1 μg / L or less. The ultrafiltration device 524 performs a filtration process using an ultrafiltration membrane to remove trace amounts of eluted material and particulate components from the upstream ion exchange resin, and reduces the number of particulates of 0.05 μm or more, for example, 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 of even higher purity. The quality of the ultrapure water is, for example, a total organic carbon (TOC) concentration of 1 μgC / L or less, a resistivity of 18 MΩ·cm or more, and a boron concentration of 0.1 ppb (μg / L) or less. The ultrapure water produced by the secondary pure water system is supplied to a point of use 53.

[0064] In each of the above-mentioned embodiments, the water quality of the raw water and the treated water can be measured by the following methods or devices. Turbidity: Light scattering method Aluminum concentration: ICP emission spectrometry pH:electrode method Conductivity: Conductivity meter (HORIBA HE-960CW) Total organic carbon (TOC) concentration: TOC meter (except ultrapure water: VEOLIA Sievers M9e) EXAMPLES

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

[0066] FIG. 6 is a schematic diagram of a pure water production apparatus 6 used in the present embodiment and comparative examples. The production apparatus 6 shown in FIG. 6 includes a raw water supply device 61 for supplying raw water, a polyaluminum chloride supply device 62 for supplying high basicity PAC, and a mixing tank 63 into which the raw water and high basicity PAC are supplied. The production apparatus 6 further includes an ultrafiltration device 65, an activated carbon filtration device 66, and a reverse osmosis membrane device 64 in this order downstream of the mixing tank 63. In the present embodiment and comparative examples, as described below, a predetermined amount of PAC having a predetermined basicity was added to the raw water, and the treatment was continued in the order of the ultrafiltration device 65, the activated carbon filtration device 66, and the reverse osmosis membrane device 64, and the change over time in the permeation flux in the reverse osmosis membrane device 64 was measured.

[0067] The specifications of the devices used in the examples are as follows. Mixing tank 63: Capacity 1m 3 Ultrafiltration device 65: Puria GL manufactured by Kuraray Co., Ltd. (PVDF membrane, nominal pore size 0.02 μm) Reverse osmosis membrane device 64: Toray Industries, Inc. TM710 (low pressure type, negatively charged membrane) Water recovery rate: 85% Measurement of aluminum concentration: Inductively coupled plasma (ICP) optical emission spectrometry Turbidity measurement: Turbidimeter (Hach2100P, manufactured by Toa Dekk Corporation) pH measurement: Water quality meter (Horiba D200, manufactured by Horiba) TOC measurement: TOC meter (Sievers M9e, VEOLIA) Raw water (lake water) quality: Turbidity 4 NTU, pH = 7.2, conductivity 250 μS / cm, TOC 4 mg / L

[0068] Example 1 Hypochlorous acid was added to the raw water so that the free chlorine concentration was 2 mg / L as Cl2, and the mixture was supplied to the mixing tank 63. Then, an aqueous solution of aluminum chloride pentahydroxide (Al2Cl(OH)5) (Nomura Micro Science Co., Ltd. prototype, basicity 83.33%) was supplied to the mixing tank 63 as a high-basicity PAC so that the aluminum concentration in the raw water was 1.2 mg / L in terms of 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 (size 47 mmφ) with a nominal pore size of 0.2 μm, and the fine particles captured by the membrane were observed, and fine particles of about 1 to 10 μm were observed. The elemental components of these fine particles were confirmed by energy dispersive X-ray fluorescence spectroscopy (EDX), and they contained Al. Furthermore, when the same amount of water was passed through a membrane (size 47 mmφ) with a nominal pore size of 0.45 μm, almost no differential pressure was observed. From the above results, it was confirmed that microflocs were formed in this example.

[0069] The treated water in the mixing tank 63 was filtered by passing it through an ultrafiltration device 65 and an activated carbon filtration device 66 in that order. Then, the treated water from the activated carbon filtration device 66 was supplied to a reverse osmosis membrane device 64 and subjected to reverse osmosis membrane treatment. The activated carbon used in the activated carbon filtration device 66 was 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 filtration device 66 was 30 (1 / h).

[0070] Example 2 In Example 1, high basicity PAC (basicity 76%) produced by the method described in Japanese Patent No. 4104773 was used as the high basicity PAC, and the same procedure as in Example 1 was repeated, with the ultrafiltration device 65, the activated carbon filtration device 66, and the reverse osmosis membrane device 64 being continuously treated in that order. In Example 2 as well, it was confirmed that microflocs were formed.

[0071] Comparative Example 1 In Example 1, granular activated carbon (Diahope M006LFA, manufactured by Mitsubishi Calgon Chemical Corporation, average particle size 1.1 to 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), but other than this, treatment was performed continuously in the ultrafiltration device 65, the activated carbon filter 66, and the reverse osmosis membrane device 64 in that order in the same manner as in Example 1. It was confirmed that microflocs were formed in Comparative Example 1 as well.

[0072] Comparative Example 2 In Comparative Example 1, low basicity PAC (PAC250A, manufactured by Taki Chemical Industry Co., Ltd., basicity 50%) was used as the PAC so that the aluminum concentration in the raw water was 0.3 to 0.4 mg / L in terms of Al2O3, the same spherical activated carbon as in Example 1 was used for the activated carbon filtration device 66, and the SV of the activated carbon filtration device 66 was 30 (1 / h), but otherwise the same treatment was carried out in the same order as in Comparative Example 1, with the ultrafiltration device 65, the activated carbon filtration device 66, and the reverse osmosis membrane device 64. The state of floc formation was equivalent to that in Comparative Example 1.

[0073] Comparative Example 3 In Example 1, low-basicity PAC (PAC250A, manufactured by Taki Chemical Industry Co., Ltd., basicity 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, the same granular activated carbon as in Comparative Example 1 was used for the activated carbon filtration device 66, and the SV of the activated carbon filtration device 66 was set to 10 (1 / h). The same treatment was performed as in Example 1, with the ultrafiltration device 65, the activated carbon filtration device 66, and the reverse osmosis membrane device 64 being continuously treated in sequence. In this comparative example, the raw water after adding low-basicity PAC and stirring was sampled, and 80 ml of the sample was passed through a membrane (size 47 mmφ) with a nominal pore size of 0.2 μm, and the fine particles captured by the membrane were observed, and fine particles of about 1 to 10 μm were observed. The elemental components of these fine particles were confirmed by EDX, and Al was contained. Furthermore, when the same amount of water was passed through a membrane (47 mmφ) with a nominal pore size of 0.45 μm, a sudden pressure difference was observed. From the above results, it was confirmed that microflocs were formed, but also that coarse aggregates with a size of 0.45 μm or more were formed.

[0074] Table 1 shows the type and basicity of the PAC used in the above Examples 1 and 2 and Comparative Examples 1 to 3. Also, Fig. 7 shows the change over time in the permeation flux (flow rate) in the reverse osmosis membrane device 64.

[0075] [Table 1]

[0076] Furthermore, in Examples 1 and 2 and Comparative Examples 1 to 3, the free chlorine concentration and turbidity of the permeated water (treated water) through the activated carbon filtration device 66 after five years of water flow were examined. The results are shown in Table 1. Furthermore, for Example 1 and Comparative Example 1, the relationship between the space velocity (SV) in the activated carbon filtration device 66 and the turbidity and free chlorine concentration of the permeated water through the activated carbon filtration device 66 after five years of water flow was examined. The results are shown in Figures 8 and 9.

[0077] From the above examples and comparative examples, it is understood that by forming suspended solids into microflocs using high basicity PAC and then filtering them with spherical activated carbon, the decrease in the permeation flux of the downstream reverse osmosis membrane device 64 can be significantly suppressed. Furthermore, it is understood that when spherical activated carbon is used, sufficient free chlorine removal performance can be achieved even though the space velocity of the activated carbon filter is higher than that of granular activated carbon. It is also understood that, compared to the use of granular activated carbon, the use of spherical activated carbon not only allows free chlorine to be removed with high accuracy over a long period of time, but also keeps turbidity low.

[0078] (Examples 3 to 5) In this example, the types of reverse osmosis membrane devices and the susceptibility of reverse osmosis membranes to clogging were examined. The reverse osmosis membrane module shown below was disassembled, and each reverse osmosis membrane was removed. The effective membrane area was 23.7 cm. 2 A flat membrane was cut out. Negatively charged film: Toray Industries, Inc. TM710 Positively charged membrane: Nitto Denko ES10C Neutral charged membrane: Nitto Denko LFC3-LD-4040

[0079] Fig. 10 is a schematic diagram of the batch type test apparatus 9 used in this example. The batch type test apparatus shown in Fig. 10 includes a container 91 for containing test water 92, a test membrane 93 provided at the 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 cylinder 96 for supplying nitrogen into the container 91 to apply pressure, and a pressure gauge 95. In this example, the flat membrane cut out above was installed as the test membrane 93 in the batch type test apparatus 9, and a water flow test was performed on each of them.

[0080] The water flow conditions were as follows: Test water (raw water): Ultrafiltration device 65 permeate of Example 1 Test water volume (raw water volume): 300ml Filtration concentration ratio: 10x Water pressure (pressure after pressure reduction by the pressure reducing valve of cylinder 96): 15kgf / cm 2 Water passing method: The inside of the container 91 was pressurized by the pressure of the cylinder 96, and the permeated water permeating the test membrane 93 was collected while stirring the test water 92 with a stirrer (not shown). When 270 ml of permeated water was obtained, the remaining test water was drained from the test water discharge valve (not shown). After that, 300 ml of test water was newly added and the water was passed again. This operation was repeated 20 times to check the degree of clogging.

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

[0082] [Table 2]

[0083] From the above results, it was found that a reverse osmosis membrane device having a negatively charged membrane is less likely to be clogged by microflocs. Note that the test water (raw water) used in Examples 3 to 5 was permeated water of an ultrafiltration membrane, and thus the fine particle components in the raw water were removed. Therefore, the decrease in the flow rate of the reverse osmosis membrane is not due to the fine particle components in the water, but is due to the influence of microflocs remaining in the permeated water of the ultrafiltration membrane. Here, since the coagulant used to form the flocs is usually positively charged, it was expected that a negatively charged membrane would be more likely to clog, but the unexpected result was that a negatively charged membrane was less likely to clog.

[0084] From the experimental examples, examples, and comparative examples described above, it can be seen that the apparatus and method for producing water for pure water according to the embodiment adds high basicity PAC to raw water and then treats it with a reverse osmosis membrane, so that suspended solids are sufficiently removed while the decrease in the permeation flux of the reverse osmosis membrane device is significantly suppressed. As a result, high purity pure water or ultrapure water can be efficiently produced over a long period of time, so the apparatus and method for producing water for pure water according to the embodiment are suitable for mass production of pure water or ultrapure water. [Explanation of symbols]

[0085] 1-4, 6...Pure water production equipment, 5...Ultrapure water production system, 11, 61...Raw water supply equipment, 12, 62...Polyaluminum chloride supply equipment, 13...Raw water transfer pipe, 14, 64...Reverse osmosis membrane equipment, 17...Spherical activated carbon filtration equipment, 23, 63...Mixing tank, 31...Filtration section, 65...Ultrafiltration equipment, 66...Activated carbon filtration equipment, 50...Pretreatment system, 51...Primary pure water system (pure water production system), 52...Secondary pure water system (subsystem), 53...Point of use (POU), 513...Ultraviolet oxidation equipment (TOC-UV), 514...Ion exchange equipment, TK1, TK2...Tank, 521...Ultraviolet oxidation equipment (TOC-UV), 522...Non-regenerative polisher (Polisher), 523...Membrane degassing equipment (MDG) 524...Ultrafiltration equipment (UF)

Claims

1. A method for producing pure water, comprising the steps of: A step of obtaining a first treated water by adding high basicity polyaluminum chloride to the raw water; A step of passing the first treated water through spherical activated carbon to perform activated carbon treatment to obtain a second treated water; and a reverse osmosis membrane step of treating the second treated water with a reverse osmosis membrane.

2. 2. The method according to claim 1, wherein the first treated water containing microflocs is obtained by adding polyaluminum chloride with high basicity to the raw water.

3. The method according to claim 1 or 2, wherein the turbidity of the raw water is 1 NTU or more and 100 NTU or less.

4. 3. The process according to claim 1 or 2, wherein the basicity of the polyaluminum chloride is greater than 75%.

5. the polyaluminum chloride comprises aluminum chloride pentahydroxide; The amount of aluminum chloride pentahydroxide added is aluminum oxide (Al ２ O ３ 3. The method according to claim 1, wherein the concentration of the nitrile in the raw water is 0.25 mg / L or more and 5 mg / L or less in terms of the concentration calculated based on the converted nitrile in the raw water.

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

7. The first treated water, The method includes a filtration step of performing a filtration treatment using one or more filters selected from sand filtration, multimedia filter (MMF) filtration, microfiltration (MF) equipment, and ultrafiltration, The method according to claim 1 or 2, wherein the treated water obtained in the filtration step is treated with the activated carbon.

8. The 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 the steps of: A step of obtaining a first treated water by supplying high basicity polyaluminum chloride to raw water; A step of passing the first treated water through spherical activated carbon to perform activated carbon treatment to obtain a second treated water; a reverse osmosis membrane process for subjecting the second treated water to a reverse osmosis membrane treatment; The method includes an ultraviolet oxidation step and an ion exchange step in this order. Manufacturing method.

10. An apparatus for producing pure water, comprising: A raw water supply device that supplies raw water; a polyaluminum chloride supplying device for adding high basicity polyaluminum chloride to raw water; an activated carbon filtration device that brings a first treated water produced by adding high-basicity polyaluminum chloride to raw water into contact with spherical activated carbon; a reverse osmosis membrane device that performs reverse osmosis membrane treatment on the second treated water produced by the activated carbon filtration device; A manufacturing apparatus having the above structure.

11. The manufacturing apparatus according to claim 10, wherein the turbidity of the raw water is 1 NTU or more and 100 NTU or less.

12. The manufacturing apparatus according to claim 10 or 11, wherein the basicity of the high basicity polyaluminum chloride is greater than 75%.

13. the polyaluminum chloride comprises aluminum chloride pentahydroxide; The polyaluminum chloride supplying device supplies aluminum oxide (Al ２ O ３ 12. The manufacturing apparatus according to claim 10, wherein the aluminum chloride pentahydroxide is supplied in an amount of 0.25 mg / L or more and 5 mg / L or less in terms of a concentration calculated based on the converted aluminum chloride.

14. Between the polyaluminum chloride supply device and the activated carbon filtration device, The apparatus has at least one selected from a sand filter, a multimedia filter (MMF) filter, a microfiltration (MF) device, and an ultrafiltration device; The manufacturing apparatus according to claim 10 or 11.

15. The apparatus for producing pure water according to claim 14, A pure water production system comprising an ultraviolet oxidation device and an ion exchange device in this order.

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