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

Abstract

Provided are a method and a device for producing water for pure water, a method for producing pure water, and a system for producing pure water, which are capable of efficiently removing suspended substances and the like in water, significantly improving the water recovery rate, and suppressing clogging of a membrane filtration device 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 polyaluminum chloride to raw water; and two or more stages of filtration steps in which the first treated water is filtered by the preceding stage filtration membrane device to obtain first concentrated water, and the first concentrated water is filtered by the following stage filtration membrane device, in which pure water, which is the permeated water of the two or more stages of filtration steps, is obtained.

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] As a turbidity removal treatment technology in water treatment such as the manufacture of industrial water from river water, well water, lake water, etc., wastewater treatment, etc., treatment using sand filtration, coagulation sedimentation, etc. has been carried out. However, in the sand filtration method and the coagulation sedimentation method using slow filtration, there are the following problems: a large equipment area is required for the equipment, or strict operation management is required according to the water to be treated. As a technology that can eliminate this disadvantage, a membrane separation method using a filter membrane such as a microfiltration membrane (MF) and an ultrafiltration membrane (UF) is widely used. In this membrane separation method, in order to improve the turbidity removal efficiency, the following process is also carried out before membrane separation: an inorganic coagulant such as polyaluminum chloride (PAC) is added to the water to be treated, a coagulation reaction is carried out to generate a coagulation floc, and the coagulation treated water containing the coagulation floc is filtered with a filter membrane (for example, refer to patent documents 1 and 2).

[0003] In the method of filtering and separating the coagulation treated water with a filtration membrane, there is a problem of fouling of the filtration membrane due to the addition of an inorganic coagulant. In order to suppress this problem, a method of adding an organic anionic substance to the treated water has been proposed (for example, refer to Patent Document 3).

[0004] In the manufacture of pure water and ultrapure water for semiconductor electronics industry and pharmaceuticals, tap water, industrial tap water, etc. are usually 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 membrane device (UF), and then treated by combining an ion exchange resin device, an ultraviolet irradiation device, etc. In the case of using tap water, industrial water, etc. as raw water, in order to remove suspended matter in the raw water, the raw water is supplied to a post-treatment device on the basis of being 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. The reason is that 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 4).

[0005] However, the above-mentioned method of filtering the condensation treated water has the problem of poor water recovery rate compared to the scale of the device. Therefore, the previous method of filtering the condensation treated water is not suitable for the manufacture of a large amount of pure water and ultrapure water for the semiconductor electronics industry and pharmaceuticals. In addition, the use of PAC in the manufacture of pure water and ultrapure water for the semiconductor electronics industry and pharmaceuticals has the following problems: fouling and membrane clogging caused by the attachment of residual aluminum in the water to the membrane. However, in the method using organic anionic substances and iron-based inorganic polymer coagulants, there are the following problems: increased costs and environmental loads caused by the increase in the amount of reagents used. In addition, there is also the following problem: membrane clogging caused by the adsorption of the residues of the polymer coagulant to the membrane surface of the subsequent membrane treatment device.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2014-168729

[0009] Patent Document 2: Japanese Patent Application Publication No. 2005-246157

[0010] Patent Document 3: Japanese Patent Application Publication No. 2022-165279

[0011] Patent Document 4: Japanese Patent Application Publication No. 2008-86966 Summary of the invention

[0012] Problem that the invention aims to solve

[0013] 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, significantly improve the water recovery rate, and can inhibit the clogging of membrane filtration equipment for a long time.

[0014] 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 significantly improving water recovery rate, thereby suppressing clogging of membrane filtration equipment for a long time.

[0015] Technical Solution

[0016] The production method, production apparatus, and pure water production system according to the embodiments of the present invention are as follows.

[0017] [1] A method for producing pure water, comprising: a step of adding polyaluminium chloride to raw water to obtain first treated water; and a two-stage or more filtration step of filtering the first treated water through a front-stage filtration membrane device to obtain first concentrated water, and filtering the first concentrated water through a rear-stage filtration membrane device, wherein pure water is obtained as permeate water of the two or more filtration steps.

[0018] [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.

[0019] [3] The production method according to [1] or [2], wherein the basicity of the polyaluminium chloride is greater than 75%.

[0020] [4] The production method according to any one of [1] to [3], wherein the polyaluminum chloride contains hydroxyaluminum chloride, and the amount of hydroxyaluminum chloride added is 0.25 mg / L or more and 25 mg / L or less relative to the raw water, calculated as the concentration of aluminum oxide (Al2O3).

[0021] [5] The production method according to [1], wherein the alkalinity of the polyaluminium chloride is 75% or less, and the production method further comprises: a pH adjustment step of adjusting the pH of the raw water to which the polyaluminium chloride is to be added.

[0022] [6] The manufacturing method according to any one of [1] to [5], further comprising at least one of the following steps: after adding polyaluminum chloride to the concentrated water of at least one of the two or more stages of filtration membrane devices, supplying it to the subsequent stage filtration membrane device.

[0023] [7] The manufacturing method according to any one of [1] to [6], further comprising: a process of adding polyaluminum chloride to concentrated water of at least the final stage of the filtration membrane device among the two or more stages of filtration membrane devices to thereby obtain second treated water; and a full filtration process of fully filtering the second treated water through the filtration membrane device, wherein the permeate water obtained by the full filtration process is used as the raw water.

[0024] [8] The manufacturing method according to [7] further includes: a cleaning process for cleaning the filtration membrane device that has undergone the full-volume filtration treatment; and a sedimentation concentration process for separating a supernatant from the cleaning wastewater generated in the cleaning process, wherein the supernatant is used as the raw water.

[0025] [9] A method for producing pure water, comprising: a step of adding polyaluminium chloride to raw water to obtain first treated water; a step of producing pure water, comprising: filtering the first treated water through a front-stage filtration membrane device to obtain first concentrated water, and filtering the first concentrated water through a rear-stage filtration membrane device in two or more stages of filtration, wherein pure water is obtained as permeate water of the two or more stages of filtration membrane processes; an ultraviolet oxidation step; and an ion exchange step.

[0026]

[10] A device for producing pure water, comprising: a raw water supply device for supplying raw water; a polyaluminium chloride supply device for adding polyaluminium chloride to the raw water; a two-stage or more filtration membrane device for filtering a first treated water generated by adding polyaluminium chloride to the raw water; a concentrated water pipe for supplying concentrated water from a front-stage filtration membrane device in the two-stage or more filtration membrane devices to a rear-stage filtration membrane device; and a plurality of conveying pipes for conveying permeated water from the two-stage or more filtration membrane devices to obtain pure water.

[0027]

[11] The production apparatus according to

[10] , wherein the basicity of the polyaluminium chloride is greater than 75%.

[0028]

[12] A manufacturing device according to

[10] or

[11] , 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 25 mg / L relative to the raw water in terms of concentration converted to aluminum oxide (Al2O3).

[0029]

[13] The manufacturing device according to

[10] , wherein the alkalinity of the polyaluminium chloride is 75% or less, and the manufacturing device further comprises: a pH adjustment device for adjusting the pH of the raw water to which the polyaluminium chloride is to be added.

[0030]

[14] A manufacturing device according to any one of

[10] to

[13] , further comprising: one or more polyaluminium chloride supply devices for adding polyaluminium chloride to concentrated water of at least one of the two or more filter membrane devices, wherein the latter filter membrane device filters the concentrated water to which the polyaluminium chloride is added.

[0031]

[15] A manufacturing device according to any one of

[10] to

[14] , further comprising: a polyaluminium chloride supply device for adding polyaluminium chloride to concentrated water of at least the final-stage filtration membrane device among the two or more stages of filtration membrane devices; and a filtration membrane device for performing full-volume filtration on second treated water generated by adding polyaluminium chloride to concentrated water of the final-stage filtration membrane device, wherein the manufacturing device comprises: piping for delivering permeate water of the filtration membrane device performing the full-volume filtration to the raw water supply device for use as the raw water.

[0032]

[16] The manufacturing device according to

[15] further comprises: a cleaning device for cleaning the filtration membrane device that performs the full-volume filtration; a sedimentation concentration device for separating the supernatant from the cleaning wastewater generated by the cleaning device; and a piping for delivering the supernatant to the raw water supply device.

[0033]

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

[10] or

[15] ; an ultraviolet oxidation device; and an ion exchange device.

[0034] It should be noted that the symbol “to” represents a numerical range including the numerical values ​​before and after it.

[0035] Beneficial Effects

[0036] According to the method and device for producing pure water of the present invention, suspended matter in raw water can be removed efficiently, the water recovery rate can be significantly improved, and the clogging of the membrane filtration device can be suppressed for a long time.

[0037] In addition, according to the pure water production method and production system of the present invention, by efficiently removing suspended matter in raw water and significantly improving the water recovery rate, the clogging of the membrane filtration device can be suppressed for a long time, and high-quality pure water can be produced for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a diagram schematically showing a production apparatus used in the method for producing pure water according to the embodiment.

[0039] Figure 2 It is schematically represented in Figure 1 The manufacturing apparatus shown also has a diagram of a manufacturing apparatus for an ultrafiltration membrane device that performs total filtration.

[0040] Figure 3 It is schematically represented in Figure 2 The manufacturing apparatus shown is a diagram of a manufacturing apparatus further including a cleaning apparatus for an ultrafiltration membrane device that performs full-volume filtration.

[0041] Figure 4 It is a diagram schematically showing a pure water production system using the pure water production apparatus according to the embodiment.

[0042] Figure 5 This is a diagram schematically showing a pure water production apparatus used in Examples.

[0043] Figure 6 It is a figure which shows schematically the apparatus used in a comparative example.

[0044] Figure 7This is a diagram schematically showing a production apparatus using a system in which treated water is transported to a subsequent stage using a blower and a bubbling tank.

[0045] Figure 8 It is a figure which shows schematically the test apparatus used in the experimental example.

[0046] Description of Reference Numerals

[0047] 1 to 4: pure water production device; 5: ultrapure water production system; 11, 41: raw water supply device; 12, 22, 42, 52: polyaluminium chloride supply device; 13: raw water delivery pipe; 14, 24, 34, 44, 54, 64: ultrafiltration membrane device; 17, 63: reaction tank; 18: pH adjustment device; 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 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 membrane device (UF). DETAILED DESCRIPTION

[0048] Hereinafter, embodiments of the present invention will be described. Figure 1 Schematically shows a manufacturing device 1 used in the method for manufacturing pure water according to the first embodiment. The manufacturing device 1 includes: a raw water supply device 11 for supplying raw water; a polyaluminum chloride supply device 12 for supplying polyaluminum chloride (hereinafter also referred to as "PAC"); and a raw water conveying pipe 13 for conveying raw water. The manufacturing device 1 also includes a first ultrafiltration membrane device 14 as a pre-stage filtration membrane device for filtering raw water (first treated water) to which PAC is added. The first ultrafiltration membrane device 14 includes: a conveying pipe 15 for conveying the permeated water to the subsequent stage; and a concentrated water pipe 16 for discharging the concentrated water.

[0049] The manufacturing apparatus 1 further includes a second ultrafiltration membrane device 24, which is connected to the concentrated water pipe 16 of the first ultrafiltration membrane device 14 and serves as a subsequent filtration membrane device for filtering the concentrated water of the first ultrafiltration membrane device 14. The second ultrafiltration membrane device 24 includes a delivery pipe 25 for delivering the permeated water to the subsequent stage and a concentrated water pipe 26 for discharging the concentrated water.

[0050] The manufacturing device 1 further includes: a reaction tank 17 for accommodating raw water supplied from the raw water supply device 11; and a pH adjusting device 18 for adding a pH adjusting agent to the raw water. The reaction tank 17 may be a mixing tank (microfloc method) for mixing PAC into raw water to form microflocs, or a sedimentation tank for rapid filtration, preferably a mixing tank. The polyaluminium chloride supply device 12 is connected to the reaction tank 17. The reaction tank 17 is provided on the upstream side of the first ultrafiltration membrane device 14 in the path of the raw water delivery pipe 13. The pH adjusting device 18 is provided on the upstream side of the reaction tank 17 in the path of the raw water delivery pipe 13. That is, the pH adjusting device 18, the reaction tank 17, and the first ultrafiltration membrane device 14 are sequentially arranged on the path of the raw water delivery pipe 13. It should be noted that the reaction tank 17 and the pH adjusting device 18 are not essential, and can be provided as needed.

[0051] In the manufacturing device 1, the first ultrafiltration membrane device 14 and the second ultrafiltration membrane device 24 are connected in series (two stages), and each is filtered in a cross-flow manner. Then, the concentrated water of the front-stage ultrafiltration membrane device is filtered by the rear-stage ultrafiltration membrane device, and the permeated water of the front-stage ultrafiltration membrane device and the permeated water of the rear-stage ultrafiltration membrane device are collected as pure water. In this way, the connection scheme of treating the treated liquid obtained from the secondary side (discharge side) of the front-stage device by the rear-stage device is called "series", which is distinguished from the "parallel" connection in which the treated water is branched and supplied to multiple devices and treated separately. That is, in this embodiment, the concentrated water (first concentrated water) of the first ultrafiltration membrane device 14 is filtered by the second ultrafiltration membrane device 24, and the permeated water (first permeated water) of the first ultrafiltration membrane device 14 and the permeated water (second permeated water) of the second ultrafiltration membrane device 24 are collected as pure water. The concentrated water (second concentrated water) of the second ultrafiltration membrane device 24 can be discharged outside the system, or additional treatment can be implemented and returned to the front stage. In the present embodiment, a configuration including two-stage ultrafiltration membrane devices is described, but three or more-stage ultrafiltration membrane devices may be provided to provide the same configuration.

[0052] Here, in the present embodiment, "two or more stages" refers to a multi-stage configuration. Specifically, "two or more stages" refers to a scheme in which two or more filter membrane devices are connected in series, and each filter membrane device filters the front-stage concentrated water, and is called the first stage, the second stage, etc. from the starting point of the series connection (the same below). In addition, it is not limited to the method in which the filter membrane devices arranged in multiple stages filter the concentrated water of the previous stage filter membrane device respectively, and also includes the case where the concentrated water of any filter membrane device on the front-stage side is filtered. In addition, in the present embodiment, the example of the polyaluminum chloride supply device 12 having PAC added to the raw water is described, but it can also be equipped with more than one polyaluminum chloride supply device that adds PAC to the supply water of the filter membrane devices after the second stage. In this case, the more than one polyaluminum chloride supply device can add PAC to all the supply water of the filter membrane devices after the second stage, and can also add PAC to the supply water of a part of the filter membrane devices. The addition of PAC is preferably carried out upstream of the front-stage filter membrane device.

[0053] 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. The raw water is urban water such as municipal water and industrial water, or natural water such as river water, lake water, groundwater, and well 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, and the pH is 4 to 9. Sometimes free chlorine is also added to the raw water during the transportation using the raw water delivery pipe 13. The raw water supply device 11, for example, includes: 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 PAC according to the quality of the raw water, a pre-filter (not shown) may be installed as a pre-treatment device. In addition, when urea or low molecular weight organic matter is mixed in the raw water, chemical oxidation treatment or accelerated oxidation treatment using ultraviolet rays may be performed.

[0054] In the manufacturing device 1, raw water is supplied from the raw water supply device 11 to the reaction tank 17, and PAC is supplied from the polyaluminium chloride supply device 12 to the reaction tank 17. In the reaction tank 17, suspended matter in the raw water interacts with PAC to form flocs, microflocs, nanoflocs, etc. In this case, the order of supplying to the reaction tank 17 may be that either the raw water or the PAC is supplied first, or both are supplied simultaneously, and it is preferred that the PAC is added to the reaction tank 17 supplied with raw water.

[0055] When the manufacturing device 1 does not have a reaction tank 17, the polyaluminium chloride supply device 12 is connected to the raw water delivery pipe 13, and PAC is added to the raw water delivery pipe 13. Thus, the first treated water is generated. When the reaction tank 17 is not used, the manufacturing device 1 can be miniaturized, so it is easy to be installed in a semiconductor manufacturing plant, etc. It should be noted that by providing a pipeline mixer for promoting mixing of raw water and PAC in the raw water delivery pipe 13 after PAC is supplied, clogging of the subsequent equipment can be further suppressed.

[0056] The polyaluminium chloride supply device 12 includes, for example, a chemical tank storing PAC and a chemical injection pump for adding PAC in the chemical tank to the reaction tank 17 . The chemical injection pump measures PAC in the chemical tank to a predetermined concentration and adds the PAC to the reaction tank 17 .

[0057] At this time, the pH adjusting device 18 adds an acid and a base as a pH adjusting agent to the raw water according to the alkalinity of the PAC to adjust the pH of the raw water. The addition of the acid and the base may be either one or both. Specifically, when using a PAC with a low alkalinity described later, the pH adjusting agent is added to the reaction tank 17 by the pH adjusting device 18 to adjust the pH of the raw water before the addition of the PAC. The pH adjusting device 18 includes, for example, an acid storage tank for storing an acid, and an acid injection pump for adding the acid in the acid storage tank to the reaction tank 17. In addition, the pH adjusting device 18 includes an alkali storage tank for storing an alkali, and an alkali injection pump for adding the alkali in the alkali storage tank to the reaction tank 17. Then, the acid injection pump and the alkali injection pump measure the acid in the acid storage tank and the alkali in the alkali storage tank so that the raw water has a predetermined pH, and add them to the reaction tank 17. The acid used here is typically sulfuric acid, and the alkali is typically sodium hydroxide (aqueous solution). It should be noted that, when the production apparatus 1 does not include the reaction tank 17 , the pH adjustment device 18 is connected to the raw water transport pipe 13 to add a pH adjuster into the raw water transport pipe 13 .

[0058] PAC in the present embodiment contains polyaluminum chloride represented by the following chemical formula (1).

[0059] [Al2(OH) n Cl 6-n ] m (1≤n≤5, m≤10)……(1)

[0060] As the PAC of this embodiment, any of low-alkalinity PAC and high-alkalinity PAC can be used. As the PAC of this embodiment, it is preferred to use any of low-alkalinity PAC and high-alkalinity PAC. When using low-alkalinity PAC (hereinafter referred to as "low-alkalinity PAC"), it is preferred to set the above-mentioned pH adjustment device to adjust the pH of the raw water. Alkalinity is a value calculated as n / 6×100 (%) in the above chemical formula (1).

[0061] The basicity of low-basicity PAC is preferably 75% or less, more preferably 60% or more and 70% or less. Low-basicity PAC can be produced, for example, by the method described in Japanese Patent Publication No. 2009-203125. As low-basicity PAC, only one type can be used, or two or more types can be used in combination. When two or more types are used in combination, the basicity of the two or more low-basicity PACs may be the same or different, but the basicity of the low-basicity PACs used is preferably 75% or less, more preferably 60% or more and 70% or less.

[0062] The amount of low-alkalinity PAC is preferably 0.03 mg / L or more in terms of Al2O3 relative to the turbidity 1NTU in the raw water. Usually, the amount of PAC added is determined according to the water quality of the treated water, and the optimal amount of addition is determined by performing a jar test. Specifically, the amount of low-alkalinity PAC is preferably 0.05 mg / L or more in terms of Al2O3 and 25 mg / L or less in terms of Al2O3 relative to the amount of raw water, and more preferably 0.1 mg / L or more in terms of Al2O3 and 20 mg / L or less in terms of Al2O3.

[0063] When PAC is used, the optimal pH for forming coagulated flocs (microflocs and flocs larger than microflocs) is in the range of 6 to 8, preferably in the range of 6.5 to 7.5. When PAC is dissolved in water, it is divided into positively charged alkaline components and hydrogen ions. The positively charged alkaline components are consumed during coagulation, so the more coagulated flocs are generated, the lower the pH. When the pH of the raw water to which PAC is added is less than 6 or greater than 8, aluminum derived from PAC and turbidity components derived from suspended matter may leak into the treated water of the downstream device.

[0064] Therefore, in particular, when using low-alkalinity PAC, it is preferable to set a pH measuring device for measuring the pH of the treated liquid in the reaction tank 17, and use the pH value measured by the pH measuring device to feedback control the amount of pH adjuster supplied by the pH adjusting device, thereby controlling the pH of the treated liquid in the reaction tank 17. When the reaction tank 17 is not used, the pH measuring device can be provided in the raw water conveying pipe 13. When the pH measuring device is used, it is preferable that the pH measuring device is provided in two or more places, preferably in the front stage of each filter membrane device, to adjust the pH of the supply water of each filter membrane device. That is, in the manufacturing device 1 of the embodiment, when the pH measuring device is used, it is preferable to have a pH measuring device in the front stage of the first ultrafiltration membrane device 14 and the front stage of the second ultrafiltration membrane device 24. The arrangement of the pH measuring device is not limited to this, and it can also be provided at any place in the path until the treated liquid to which the PAC is added is supplied to the filtration device.

[0065] In the present embodiment, as PAC, it is preferred to use a high-alkalinity PAC (hereinafter referred to as "high-alkalinity PAC"). When a high-alkalinity PAC is used, the pH also decreases with the formation of microflocs, but the amount of decrease is so small that it does not cause a problem. The alkalinity of the high-alkalinity PAC is preferably greater than 75%, and more preferably greater than 83%. The upper limit of the alkalinity is usually less than about 84%. The high-alkalinity PAC can be manufactured, for example, by the method described in Japanese Patent No. 4104773. As a high-alkalinity 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 alkalinity of the two or more high-alkalinity PACs may be the same or different, but the alkalinity of the high-alkalinity PACs used is preferably greater than 75%, and more preferably greater than 83%.

[0066] If high alkalinity PAC is used, suspended matter in the raw water interacts with high alkalinity PAC to selectively form microflocs. By passing through the microflocs, the adhesion of residual aluminum to the membrane in the first ultrafiltration membrane device 14 and the second ultrafiltration membrane device 24 can be significantly reduced, and the performance of the ultrafiltration membrane can be maintained for a long time. In addition, the microflocs are not easily destroyed during the transportation process in the piping, pumps, etc., so the turbidity removal rate is not easily reduced in the multi-stage filtration membrane treatment. Microflocs are aggregates of suspended matter and high alkalinity PAC with a size of about 1 to 10 μm. High alkalinity PAC easily forms microflocs, but it is not easy to form coarse flocs larger than microflocs 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 ultrafiltration membrane can be prevented for a long time.

[0067] 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.

[0068] The amount of high-alkalinity PAC is preferably 0.125 mg / L or more in terms of Al2O3 relative to the turbidity 1NTU in the raw water. Usually, the amount of PAC added is determined according to the water quality of the treated water, and the optimal amount of addition is determined by performing a cup test. Specifically, the amount of high-alkalinity PAC is preferably 0.25 mg / L or more in terms of Al2O3 and 25 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 22 mg / L or less in terms of Al2O3. In particular, when hydroxyaluminum chloride (Al2Cl(OH)5) is used as a high-alkalinity PAC, the amount of hydroxyaluminum chloride is preferably 0.25 mg / L or more in terms of Al2O3 and 20 mg / L or less in terms of Al2O3 relative to the total amount of raw water. Even if the amount of high-alkalinity PAC is as small as described above, it can micro-flocculate 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 subsequent ultrafiltration membrane device. It should be noted that the expression "in terms of Al2O3" means a value converted into alumina (Al2O3) concentration.

[0069] When using high alkalinity PAC, by rapidly stirring the raw water and high alkalinity PAC in the reaction tank 17, nano-flocs are not generated and more homogeneous micro-flocs are easily formed. The stirring speed is preferably 150 s 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.

[0070] When PAC is added, an inorganic coagulant or an organic polymer coagulant other than PAC may be used as a coagulant aid. The amount of the coagulant aid added in this case can be determined by performing a cup test.

[0071] Next, the first treated water is supplied to the first ultrafiltration membrane device 14 for filtration treatment. By providing a water supply pump in the raw water delivery pipe 13 on the downstream side of the reaction tank 17, the first treated water can be supplied to the first ultrafiltration membrane device 14 by the water supply pump. From the perspective of suppressing the reduction of the permeation flux in the first ultrafiltration membrane device 14, the pressure difference between the inlet pressure and the outlet pressure of the first ultrafiltration membrane device 14 at this time is preferably 0.004MPa to 0.04MPa. In order to improve the water recovery rate of the entire manufacturing device 1, the water recovery rate in the first ultrafiltration membrane device 14 is preferably 75% to 95%, more preferably 80% to 95%, and further preferably 90% to 95%. Thus, the permeated water (first permeated water) and concentrated water (first concentrated water) of the first ultrafiltration membrane device 14 are obtained. It should be noted that a scale inhibitor or an antibacterial agent may be appropriately added to the first treated water just before it is supplied to the first ultrafiltration membrane device 14.

[0072] Next, the first concentrated water is supplied to the second ultrafiltration membrane device 24 for filtration treatment. From the perspective of suppressing the reduction of the permeation flux in the second ultrafiltration membrane device 24, the pressure difference between the inlet pressure and the outlet pressure of the second ultrafiltration membrane device 24 at this time is preferably 0.004MPa to 0.04MPa. In order to improve the water recovery rate of the entire manufacturing device 1, the water recovery rate in the second ultrafiltration membrane device 24 is preferably 75% to 95%, more preferably 80% to 95%, and further preferably 90% to 95%. Thus, permeated water (second permeated water) and concentrated water (second concentrated water) of the second ultrafiltration membrane device 24 are obtained. The first permeated water and the second permeated water thus obtained are appropriately collected and supplied to pure water production as pure water.

[0073] The pre-filter membrane device is equipped with a filter membrane capable of capturing microflocculation as a filter element. As such a filter membrane, for example, a filter membrane with a nominal pore size of 0.1 μm to 5 μm can be used. As such a filter membrane, ultrafiltration membranes and microporous filter membranes can be listed. In the present embodiment, an ultrafiltration membrane device is used. In the present embodiment, the filter element is preferably an ultrafiltration membrane with a nominal pore size of 0.001 to 0.1 μm. As the ultrafiltration membrane possessed by the first ultrafiltration membrane device 14, there are hollow fiber membranes, spiral membranes, and flat membranes formed of materials such as cellulose acetate, aromatic polyamide, polyvinyl alcohol, polysulfone, and polyvinylidene fluoride. Among them, hollow fiber membranes formed of fluorine-based materials such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) are preferred. As the first ultrafiltration membrane device 14, an external pressure ultrafiltration membrane device using the hollow fiber membrane is preferred.

[0074] As the front-stage and rear-stage filter membrane devices, any type of independent or immersed filter membrane devices can also be used. The independent filter membrane device is also called a pressurized type. It is a device that fills a filter membrane in a pressure-resistant container and performs high-pressure filtration. It is suitable for low-turbidity water treatment. The independent filter membrane device has a large membrane area and can achieve high-flow operation. Therefore, it has the advantage of being able to treat a large amount of water with a small installation area. The membrane possessed by the independent filter membrane is preferably a ceramic membrane or a membrane formed of a fluorine-based material such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). The supply pressure of the independent filter membrane device can be set to an arbitrary value in a manner that the pressure difference between the inlet pressure and the outlet pressure of the filter membrane device is 0.004MPa to 0.04MPa. The supply pressure to the independent filter membrane device is preferably greater than 0.03MPa and less than 0.1MPa.

[0075] According to the independent type filtration membrane device, the outflow of nano-flocs to the downstream side is small, so it is effective in preventing the clogging of the filtration membrane device on the rear stage side. In particular, when the method of this embodiment is used to manufacture ultrapure water for manufacturing semiconductors, etc., by using an independent type filtration membrane device, two or more independent type filtration membrane devices are first arranged in parallel in each stage, and regeneration such as backwashing and module replacement are performed one by one among the multiple devices, and the other devices are continuously operated (so-called carousel operation), thereby continuously manufacturing ultrapure water without stopping the device.

[0076] It is preferred to use an independent type ultrafiltration membrane device as the first ultrafiltration membrane device 14. As the ultrafiltration membranes provided by the independent type ultrafiltration device, there are hollow fiber membranes, spiral membranes, and flat membranes formed of materials such as cellulose acetate, aromatic polyamide, polyvinyl alcohol, polysulfone, and polyvinylidene fluoride, among which hollow fiber membranes formed of fluorine-based materials such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) are preferred.

[0077] As independent ultrafiltration membrane devices, there can be listed cylindrical devices and modular devices. The cylindrical device is, for example, constructed as follows: a cylinder containing an ultrafiltration membrane in a shell, a pipe is connected to a water inlet and a drain outlet opened in the shell, and water is passed into the cylinder through the opening. The cylindrical device has the following advantages: when the ultrafiltration membrane deteriorates, only the cylinder can be replaced. In the case of using an independent ultrafiltration membrane device, by setting a water supply pump on the primary side (water supply side) of the first-stage ultrafiltration membrane device, the filtration treatment in the second-stage ultrafiltration membrane device can be carried out. Therefore, compared with the case where a water supply pump is set on the primary side of each ultrafiltration membrane device, the destruction of flocs caused by the pump can be suppressed to a minimum. In this way, when a two-stage independent ultrafiltration membrane device is operated by a water supply pump on the primary side, considering the pressure loss in the process of passing through the pipe and the filter membrane, it is preferred to set the supply pressure of the pump to be higher than the desired pressure to be achieved in each ultrafiltration membrane device. In addition, in order to prevent the pressure applied to the filter membrane of each ultrafiltration membrane device from becoming too high, it is preferred to set a pressure regulating valve such as a pressure reducing valve on the secondary side of each ultrafiltration membrane device (for example, a conveying pipe for permeated water). As a pump set on the primary side of an independent ultrafiltration device, a floc decomposition suppressing pump such as a Hidrostal pump, a Hidrostal Chemical pump, a hose pump, or a Mohno pump that can suppress the destruction of flocs is preferably used.

[0078] The modular device is constructed as follows: the ultrafiltration membrane is arranged inside the housing, and the module is connected to the piping, thereby passing water to the ultrafiltration membrane. The modular device has the following advantages: each module can be replaced when the filter element deteriorates, and the deteriorated ultrafiltration membrane can be cleaned for each module.

[0079] The immersion type filtration membrane device is a device configured for tank immersion, and is suitable for filtering raw water with high turbidity. The immersion type filtration membrane device is immersed in the bottom of the reaction tank 17, and has the following advantages: the first treated water added with PAC can be directly filtered without using piping. In this embodiment, when using high alkalinity PAC, by forming microflocs in water, it is possible to directly perform filtration treatment without precipitation removal using a coagulation sedimentation tank as used in coarse flocs. Therefore, the filtration membrane device can be immersed in the reaction tank 17 and integrated, and the overall structure of the device can be simplified. When using an immersion type filtration membrane device, a low-pressure suction pump is provided downstream of the multi-stage filtration membrane device, and the treated liquid can be supplied to the multi-stage ultrafiltration membrane device through the low-pressure suction pump for filtration. In this case, the pump is present on the downstream side of the membrane treatment device, so it has the following advantages: the collapse of the flocs caused by the impact during the operation of the pump is not likely to occur. Therefore, when using low alkalinity PAC and high alkalinity PAC, an immersion type membrane filtration device can be used. In addition, a water head difference can be set on the secondary side (discharge side) of the multi-stage filtration membrane device to filter by gravity to obtain permeate water. This can avoid consuming a lot of energy due to pump operation and reduce operating costs.

[0080] When using an ultrafiltration device as an immersion type filtration membrane device, the filtration membrane of the ultrafiltration membrane device is preferably made of ceramics or fluorine-based materials such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). In addition, the suction pressure is preferably 0.004 MPa or more and 0.03 MPa or less.

[0081] As the second ultrafiltration membrane device 24, the same ultrafiltration membrane device as the first ultrafiltration membrane device 14 can be used, and the preferred embodiment is also the same. The characteristics of the first ultrafiltration membrane device 14 and the second ultrafiltration membrane device 24 may be the same or different. As the first ultrafiltration membrane device 14 and the second ultrafiltration membrane device 24, commercial products can be used. As commercial products, for example, HSU-1515 manufactured by TORAY, hollow fiber membrane Microza UNA620A manufactured by Asahi Kasei Corporation, hollow fiber membrane Microza UHS-620A manufactured by Asahi Kasei Corporation, etc. can be used.

[0082] The water quality of the first permeated water and the second permeated water thus obtained is, for example, turbidity of 0.01 NTU to 0.4 NTU, aluminum concentration of 0 mg / L to 0.02 mg / L, pH of 5.9 to 7.5, and conductivity of 140 μS / cm to 270 μS / cm.

[0083] According to the manufacturing device 1 described above, the concentrated water of the first ultrafiltration membrane device 14 is filtered by the second ultrafiltration membrane device 24, thereby obtaining permeate water with good purity and dramatically improving the water recovery rate in the manufacturing device 1. The water recovery rate in the manufacturing device 1 obtained in this way is, for example, 98% or more, preferably 99% or more, and more preferably 99.5% or more.

[0084] Next, a method for producing pure water according to a second embodiment will be described. Figure 2 This is a diagram schematically showing a production apparatus 2 used in a method for producing pure water according to a second embodiment. Figure 2 The manufacturing device 2 shown is provided with a third ultrafiltration membrane device 34 as a third-stage filtration membrane device at the rear stage of the concentrated water pipe 26, and the second concentrated water is filtered by the third ultrafiltration membrane device 34. In addition, the manufacturing device 2 is provided with a polyaluminum chloride supply device 22, which supplies polyaluminum chloride to the second concentrated water flowing through the concentrated water pipe 26. A permeate water delivery pipe 35 is connected to the third ultrafiltration membrane device 34. The end of the permeate water delivery pipe 35 on the opposite side to the third ultrafiltration membrane device 34 is connected to the raw water delivery pipe 13 at the upstream side of the pH adjustment device 18. The other configurations are the same as those of the manufacturing device 1, and therefore a detailed description of the configurations common to the manufacturing device 1 is omitted.

[0085] The production of pure water using the production device 2 is performed as follows. As in the production device 1, raw water is contained in the reaction tank 17 via the raw water delivery pipe 13, and after PAC is added to the raw water, it is sequentially supplied to the first ultrafiltration membrane device 14 and the second ultrafiltration membrane device 24. Then, as described above, in the production device 2, the polyaluminum chloride supply device 22 adds PAC to the second concentrated water during the flow of the second concentrated water in the concentrated water pipe 26. It should be noted that if a pipeline mixer or the like for promoting the mixing of the second concentrated water and PAC is provided in the concentrated water pipe 26 after the PAC is supplied, the clogging of the subsequent equipment is further suppressed.

[0086] The concentrated water of the first ultrafiltration membrane device 14 is filtered through the second ultrafiltration membrane device 24. In the second concentrated water, the floccules and microflocules composed of suspended matter and PAC derived from the raw water are concentrated to a high concentration. These floccules and microflocules sometimes collapse during the circulation process in the pipes and pumps (not shown). Therefore, if the second concentrated water is directly filtered through the third ultrafiltration membrane device 34, the aluminum derived from PAC and the suspended matter derived from the raw water contained in the floccules may cause rapid clogging of the ultrafiltration membrane.

[0087] Therefore, in the manufacturing device 2 of the present embodiment, the second treated water obtained by adding polyaluminium chloride to the second concentrated water is supplied to the third ultrafiltration membrane device 34. The types and preferred embodiments of PAC at this time are the same as those of the manufacturing device 1. In addition, as in the manufacturing device 1, a reaction tank may be provided in the front stage of the third ultrafiltration membrane device 34, the polyaluminium chloride supply device 22 may be connected to the reaction tank, the second concentrated water may be contained in the reaction tank, and PAC may be added to the second concentrated water in the reaction tank.

[0088] When low-alkalinity PAC is used, it is preferred that a pH adjusting device is provided on the upstream side of the polyaluminium chloride supply device 22, as in the manufacturing device 1, and a pH adjusting agent is added to the second concentrated water. Thus, the pH adjusting device can adjust the pH of the second concentrated water by appropriately adding acid and alkali to the second concentrated water according to the alkalinity of the low-alkalinity PAC (providing a pH adjusting step). The amount of pH adjusting agent added at this time can also be the same as in the manufacturing device 1, by providing a pH measuring device, thereby measuring the pH of the second concentrated water before adding PAC, and performing feedback control based on the measured value.

[0089] When high alkalinity PAC is used, the pH of the second concentrated water does not need to be adjusted. By adding high alkalinity PAC to the second treated water, the suspended matter in the second treated water interacts with the high alkalinity PAC to form microflocs. By passing through the microflocs, the clogging of the membrane of the third ultrafiltration membrane device 34 is significantly suppressed, so the performance of the ultrafiltration membrane can be maintained for a long time. In addition, the inventors have found through experiments that if high alkalinity PAC is used, the TOC (total organic carbon) in the third permeate water is reduced compared to the case where low alkalinity PAC is used.

[0090] Next, the second treated water is filtered through the third ultrafiltration membrane device 34. The filtering process in the third ultrafiltration membrane device 34 is a dead-end filtration (full filtration), so it can improve the water recovery rate in the manufacturing device 2. It should be noted that in the present embodiment, full filtration refers to a range that is substantially equivalent to full filtration, that is, almost no concentrated water is generated, for example, indicating a water recovery rate of more than 98%. The pressure difference between the inlet pressure and the outlet pressure of the third ultrafiltration membrane device 34 is preferably 0.004MPa to 0.04MPa. In addition, the water supply pressure to the third ultrafiltration membrane device 34 is preferably 0.03MPa to 0.1MPa. In this way, the third permeate water as the permeate water of the third ultrafiltration membrane device 34 is obtained.

[0091] As the third-stage filtration membrane device, for example, a filtration membrane with a nominal pore size of 0.001 to 0.1 μm is provided as a filter element. As such a filtration membrane, ultrafiltration membranes and microporous filtration membranes can be listed. In the present embodiment, an ultrafiltration membrane device is used. In the present embodiment, the filter element is preferably an ultrafiltration membrane with a nominal pore size of 0.001 to 0.1 μm. As the ultrafiltration membrane provided by the third ultrafiltration membrane device 34, 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 third ultrafiltration membrane device 34, an external pressure ultrafiltration membrane device using the hollow fiber membrane is preferred.

[0092] As the third ultrafiltration membrane device 34, it is preferred to use an independent ultrafiltration membrane device. By using an independent ultrafiltration membrane device, two or more independent ultrafiltration membrane devices are pre-connected in parallel in the third-stage third ultrafiltration membrane device 34, and regeneration such as backwashing and module replacement are performed one by one among the multiple devices, and the device is continuously operated (so-called merry-go-round operation), thereby continuously producing ultrapure water without stopping the device. In addition, as a pump provided on the primary side of the independent ultrafiltration device, it is preferred to use a floc decomposition inhibition pump such as a Hidrostal pump, a Hidrostal Chemical pump, a hose pump, a Mohno pump, etc. that can inhibit the destruction of flocs.

[0093] Next, the third permeated water is returned to the upstream side of the reaction tank 17 through the transport pipe 35 and is treated again as the raw water 11 .

[0094] According to the manufacturing device 2 described above, the second concentrated water to which PAC is added is filtered by the third ultrafiltration membrane device 34, thereby obtaining the third permeated water of good purity, and dramatically improving the water recovery rate in the manufacturing device 2. The water recovery rate in the manufacturing device 2 obtained in this way is, for example, 99% or more, preferably 99.5% or more. In addition, by using PAC, floccules are formed from the suspended matter remaining in the second concentrated water, so that the residual aluminum and residual suspended matter in the third permeated water can be greatly reduced. Moreover, if high-alkalinity PAC is used, the TOC (total organic carbon) in the third permeated water can be reduced. In this way, the quality of the raw water treated by the manufacturing device 2 can be improved, so the amount of chemicals used can be reduced, and pure water with good water quality can be efficiently produced.

[0095] It should be noted that the reason why TOC is efficiently reduced by the filtration membrane device after the second stage is speculated as follows. In the first stage ultrafiltration membrane device, turbidity components react preferentially with PAC to form flocs. The reason is that the reaction rate of turbidity components with PAC is faster than the reaction rate of TOC with PAC. Then, it can be considered that when PAC is added to the upstream side of the ultrafiltration membrane device after the second stage, most of the turbidity components in the concentrated water of the first stage filtration membrane device are in the state of flocs, so TOC in the concentrated water combines with PAC and is removed by the filtration membrane.

[0096] Next, another embodiment of the present invention will be described. Figure 3 The manufacturing device 3 used in the method for manufacturing pure water of the present embodiment is schematically shown in the figure. The manufacturing device 3 is a device for reusing the cleaning wastewater when the third ultrafiltration membrane device 34 is cleaned. The manufacturing device 3 comprises: a sedimentation and concentration device 191, which separates the cleaning wastewater into a high-concentration waste liquid and a supernatant; and a conveying device 192, which stores the supernatant and supplies it to the raw water conveying pipe 13. In addition, the manufacturing device 3 comprises: a tank TK, which stores cleaning (backwashing) water; a backwashing piping 193, which supplies the cleaning water in the tank TK to the third ultrafiltration membrane device 34; a backwashing piping 194, which sends the cleaning wastewater discharged from the third ultrafiltration membrane device 34 to the sedimentation and concentration device 191; and a valve V, which is clamped on the backwashing piping 194. The others are Figure 2 The production apparatus 2 shown has the same configuration, and therefore duplicate descriptions are omitted. The transport device 192 is composed of, for example, a tank for storing the supernatant liquid, and a pump and a pipe for transporting the supernatant liquid.

[0097] In the manufacturing device 3, a part of the second concentrated water is collected by the concentrated water pipe 26 as washing (backwashing) water and stored in the tank TK. The remaining part of the second concentrated water is sent to the next stage as treated water, and the polyaluminum chloride supply device 22 adds PAC to the treated water. In the state of closing the valve V, the third ultrafiltration membrane device 34 continues to filter the second concentrated water (treated water) added with PAC in full. After continuing to filter the second concentrated water (treated water), when the blockage is aggravated, the third ultrafiltration membrane device 34 is subjected to chemical cleaning. Chemical cleaning is performed, for example, as described below. First, by adding sodium hydroxide (NaOH) to the washing water in the tank TK, alkaline washing water with sodium hydroxide as the main component is generated, and then the valve V is opened to pass the alkaline washing water from the secondary side during the filtration treatment to the ultrafiltration membrane device. Then, by adding phosphoric acid (H3PO4) to the washing water in the tank TK, acid washing water with phosphoric acid as the main component is generated, and the acid washing water is passed from the secondary side during the filtration treatment to the ultrafiltration membrane device. As chemicals, in addition to the above, potassium hydroxide and ammonia can be used as alkaline cleaning water, sulfuric acid, hydrochloric acid, oxalic acid, and citric acid can be used as substitutes for acid cleaning water. In addition, sodium hypochlorite can be used as an oxidant depending on the membrane attachment to be cleaned. Chemical cleaning is carried out using alkaline cleaning water, acid cleaning water, etc. obtained by mixing chemicals into the cleaning water collected in the above. The frequency of chemical cleaning is usually about once every 14 to 21 days. The cleaning wastewater thus generated is passed through the backwashing pipe 194 and contained in the sedimentation concentration device 191, and is separated into a supernatant and a concentrated liquid in the sedimentation concentration device 191. After the separated supernatant is temporarily stored in the conveying device 192, it is supplied to the raw water conveying pipe 13 for reprocessing.

[0098] According to the manufacturing device 3 of this embodiment, the blockage of the third ultrafiltration membrane device 34 in the case of full filtration is quickly eliminated by chemical cleaning, and the cleaning wastewater is used as raw water, thereby reducing the amount of wastewater. It should be noted that in the first ultrafiltration membrane device 14 and the second ultrafiltration membrane device 24, a device for cleaning each device and reusing the cleaning wastewater can also be provided.

[0099] Next, the production apparatus 8 using the blower and the bubbling tank will be described. Figure 7Schematically shows a manufacturing device 8 that uses a method of conveying treated water to which PAC is added to a subsequent stage using a blower and a bubbling tank. The manufacturing device 8 includes: a reaction tank 471 that contains raw water; a polyaluminum chloride supply device 42 that supplies PAC to the reaction tank 471; and a raw water conveying pipe 13 that conveys raw water. The manufacturing device 8 has a bubbling tank 472 at the subsequent stage of the reaction tank 471. A diffuser pipe 47a is provided at the bottom of the bubbling tank 472. The manufacturing device 8 has a blower B that conveys air to the diffuser pipe, and the blower B is connected to the diffuser pipe 47a by a pipe.

[0100] The manufacturing device 8 is further provided with a first-stage ultrafiltration membrane device 44 for filtering raw water (first treated water) to which PAC is added. The first-stage ultrafiltration membrane device 44 is connected with a delivery pipe 15 for delivering the permeated water to the subsequent stage and a concentrated water pipe 16 for discharging the concentrated water. A suction pump P is interposed in the delivery pipe 15.

[0101] The manufacturing device 8 further includes a bubbling tank 441 for accommodating concentrated water (first concentrated water) from the first-stage ultrafiltration membrane device 44. An air diffusion pipe 44a is provided at the bottom of the bubbling tank 441. The manufacturing device 8 includes a blower B for sending air to the air diffusion pipe 44a, and the blower B is connected to the air diffusion pipe 44a by a pipe.

[0102] The manufacturing device 8 further includes a second-stage ultrafiltration membrane device 54 for filtering the first concentrated water. The second-stage ultrafiltration membrane device 54 is connected to a delivery pipe 25 for delivering the permeated water to the next stage and a concentrated water pipe 26 for discharging the concentrated water. A suction pump P is interposed in the delivery pipe 25.

[0103] The first-stage ultrafiltration membrane device 44 and the second-stage ultrafiltration membrane device 54 are each composed of an immersion tank and an ultrafiltration membrane immersed in the immersion tank. The bubbling tank 472 is connected to the immersion tank in which the first-stage ultrafiltration membrane device 44 is immersed through the delivery pipe 13b, and the bubbling tank 441 is connected to the second-stage ultrafiltration membrane device 54 through the concentrated water pipe 16b. The delivery pipe 13b and the concentrated water pipe 16b are both inclinedly arranged in a manner that the front stage side is located at a higher position than the rear stage side, so that water flows from the front stage to the rear stage by its own weight.

[0104] In the bubbling tank 472, air supplied from the blower B is bubbled by the air diffusion pipe 47a. In the bubbling tank 472, air bubbles float in the water, thereby floating the floccules to the vicinity of the water surface of the bubbling tank 472. By connecting the delivery pipe 13b to the vicinity of the water surface of the bubbling tank, the treated water containing the floccules is delivered to the first-stage ultrafiltration membrane device 44 by its own weight through the delivery pipe 13b that makes the rear stage tilted lower. In the first-stage ultrafiltration membrane device 44, the permeated water is sucked by the suction pump P, and the concentrated water is delivered to the bubbling tank 441 through the concentrated water pipe 16.

[0105] In the bubbling tank 441, air supplied from the blower B is bubbled by the air diffusion pipe 44a. In the bubbling tank 441, air bubbles float in the water, thereby floating flocs to the vicinity of the water surface of the bubbling tank 441. By connecting the delivery pipe 16b to the vicinity of the water surface of the bubbling tank 441, the treated water containing flocs is sent to the second-stage ultrafiltration membrane device 54 by its own weight through the delivery pipe 16b that makes the rear stage tilted lower. In the second-stage ultrafiltration membrane device 54, the permeated water is sucked by the suction pump P, and the concentrated water is sent to the rear stage through the concentrated water pipe 26.

[0106] There is a method in which treated water containing flocs generated by adding PAC to raw water is sucked or transported by a pump and transported to a subsequent stage. Figure 7 In the manufacturing device 8 shown in the figure, which uses a blower to transport to the subsequent stage, the treated water containing flocs can be bubbled to make the flocs float to the upper part of the reaction tank, and the treated water containing flocs can flow to the subsequent stage by gravity through the pipe connected to the upper part of the reaction tank and inclined in a manner that becomes lower toward the subsequent stage. This method is particularly suitable for the case of using low-alkalinity PAC, and can also be appropriately applied when using high-alkalinity PAC that generates micro-flocs that are not easily destroyed. It should be noted that in the manufacturing device 8, the same figure marks are given to the common structures of the manufacturing devices 1 to 3 and the manufacturing device 4 described later, and detailed descriptions are omitted.

[0107] Next, refer to Figure 4 , an ultrapure water production system 5 according to an embodiment using the above-described production apparatus 1 will be described. Figure 4 1 is a block diagram schematically showing the structure of an ultrapure water production system 5 using the production apparatus 1. Figure 4 In the above description, the production apparatus 1 can be changed to any one of the production apparatuses 2 to 3.

[0108] like Figure 4 As shown, the ultrapure water manufacturing system 5 manufactures pure water or ultrapure water using the pure water obtained by the manufacturing device 1. The ultrapure water manufacturing system 5 sequentially comprises a pretreatment system 50, a primary pure water system (pure water manufacturing 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, and the ultrapure water manufactured by the ultrapure water manufacturing system 5 is supplied to the POU 53.

[0109] 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.

[0110] The ultrapure water production system 5 includes a tank TK1 at a subsequent stage of the pretreatment system 50 , and 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 .

[0111] 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.

[0112] 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.

[0113] 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. Boron adsorbing ion exchange resin can also be used as the ion exchange resin.

[0114] The primary pure water obtained by the primary pure water system 51 has, for example, a resistivity of 17 MΩμcm or more and a TOC concentration of 10 μgC / L or less.

[0115] The ultrapure water production system 5 is provided in order after the primary pure water system 51: a primary pure water tank TK2 for storing primary pure water; and a secondary pure water system 52. 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) for non-regenerative ultrapure water production 522, a membrane degassing device (MDG) 523, and an ultrafiltration membrane device (UF) 524.

[0116] 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.

[0117] 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 membrane device 524 performs filtration processing through 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 above 0.05 μm to about 250 Pcs. / L or less.

[0118] 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 by the secondary pure water system is supplied to the use point 53.

[0119] 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.

[0120] Turbidity: A measure of light scattering.

[0121] Aluminum concentration: ICP luminescence analysis.

[0122] pH: electrode method.

[0123] Electrical conductivity: Electrical conductivity meter (HE-960CW manufactured by Horiba, Ltd.).

[0124] Total organic carbon (TOC) concentration: TOC meter (except ultrapure water: Sievers M9e manufactured by SUEZ Corporation).

[0125] Example

[0126] Next, examples will be described. The present invention is not limited to the following examples.

[0127] Figure 5 Schematically shows a pure water production device 4 used in the present embodiment and the comparative example. Figure 5The manufacturing device 4 shown in the figure is provided with: a raw water supply device 41 for supplying raw water; polyaluminium chloride supply devices 42 and 52 for supplying PAC; and a reaction tank 47 for supplying raw water and high alkalinity PAC inside. The manufacturing device 4 is further provided with: an ultrafiltration membrane device 44; an ultrafiltration membrane device 54 for treating concentrated water of the ultrafiltration membrane device 44; and an ultrafiltration membrane device 64 for treating concentrated water of the ultrafiltration membrane device 54 on the downstream side of the reaction tank 47. A reaction tank 63 for accommodating concentrated water of the ultrafiltration membrane device 54 as a second-stage filtration membrane device is provided in the front stage of the ultrafiltration membrane device 64. In the manufacturing device 4, the polyaluminium chloride supply device 42 supplies PAC into the reaction tank 47, and the polyaluminium chloride supply device 52 supplies PAC into the reaction tank 63.

[0128] The specifications of each device used in the Examples and Experimental Examples are as follows.

[0129] Reaction tank 47: Capacity 1m 3 .

[0130] Ultrafiltration membrane devices 44 and 54: ZeeWeed 500 Membrane manufactured by VEOLIA (impregnated PVDF membrane, nominal pore size 0.04 μm).

[0131] Ultrafiltration membrane device 64: Pyuria GL manufactured by Kuraray Co., Ltd. (pressurized membrane, PVDF membrane, nominal pore size 0.02 μm).

[0132] Determination of aluminum concentration: high frequency inductively coupled plasma (ICP) luminescence analysis.

[0133] Turbidity measurement: Turbidimeter (Hach2100P, manufactured by TOADKK Co., Ltd.).

[0134] pH measurement: Water quality meter (Horiba D200, manufactured by Horiba Corporation).

[0135] Determination of TOC: TOC meter (Suez M9e).

[0136] The water quality of raw water (lake water): turbidity 2.2NTU, pH=8.0, aluminum concentration 0.019mg / L, conductivity 250μS / cm, TOC is 2mg / L.

[0137] (Example 1)

[0138] The raw water was supplied to the reaction tank 47. Then, an aqueous solution of hydroxyaluminum chloride (Al2Cl(OH)5) (a trial product of Nomura Microscience Co., Ltd., alkalinity 83.33%) was supplied to the reaction tank 47 as a high alkalinity PAC through the polyaluminum chloride supply device 42, and stirred in such a manner that the aluminum concentration in the raw water was 2 mg / L in terms of Al2O3. 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 200 μm). ) and observed the particles captured by the membrane. 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 they contained Al. In addition, for the membrane with a nominal pore size of 0.45 μm (large ) When the same amount of water was passed, there was almost no pressure difference. Based on the above results, it was confirmed that microflocculation was formed in this example.

[0139] The treated water in the reaction tank 47 is passed to the ultrafiltration membrane device 44 for filtration, and the first permeated water and the first concentrated water are obtained. The first concentrated water is passed to the ultrafiltration membrane device 54 for filtration, and the second permeated water and the second concentrated water are obtained. The first permeated water and the second permeated water are recovered via the piping. Next, the second concentrated water is contained in the reaction tank 63, and the same high alkalinity PAC is added through the polyaluminum chloride supply device 52 in such a way that the aluminum concentration in the water is 20 mg / L in terms of Al2O3, and the water is passed to the ultrafiltration membrane device 64 for full filtration, and the third permeated water is obtained. The third permeated water is mixed with the raw water for reprocessing, and this process is repeated. The water recovery rate of the ultrafiltration membrane device 44 (first stage) and the ultrafiltration membrane device 54 (second stage) are both set to 90%, and the suction pressure is set to 10 kPa in the first stage and 5 kPa in the second stage.

[0140] (Example 2)

[0141] In Example 1, low alkalinity PAC (trade name PAC250A, manufacturer: Taki Chemical Co., Ltd., alkalinity 51%) was used instead of high alkalinity PAC, and the aluminum concentration in the raw water was 2 mg / L in terms of Al2O3, and the aluminum concentration in the second concentrated water (the water supplied to the ultrafiltration membrane device 64 (third stage)) after the addition of PAC was 20 mg / L in terms of Al2O3. In addition, the treatment was repeated in the same manner as in Example 1 except that a pH adjuster (sulfuric acid and an aqueous solution of aluminum hydroxide) was added to the raw water and the second concentrated water when PAC was added to adjust the pH to 6.5 to 7.5.

[0142] (Comparative Example 1)

[0143] In Example 2, the treatment was repeated in the same manner as in Example 2 except that the pH adjustment was not performed. The pH of the feed water to the ultrafiltration membrane device 64 (third stage) was 5.8.

[0144] In Comparative Example 1, the aluminum concentration of the third permeated water is about 25 times that of the raw water, the turbidity component is about 17 times, and the TOC concentration is 1.5 times, and the water quality is worse than that of the raw water. Therefore, the third permeated water cannot be returned to the upstream side of the reaction tank 47. The reason is that if the third permeated water with a water quality worse than that of the raw water is returned to the upstream side of the reaction tank 47, the quality of the raw water is likely to gradually deteriorate, and the membrane is likely to be blocked by the turbidity components derived from the raw water. In addition, in the preliminary experiment conducted before this comparative example, when the water recovery rate of the entire two-stage ultrafiltration membrane device was set to 99% and the treatment was performed, the membrane was frequently blocked in the ultrafiltration membrane device 44, especially the ultrafiltration membrane device 54. Therefore, based on the results of the preliminary experiment, in this comparative example, the operation was performed in a manner in which the water recovery rate of the entire two-stage ultrafiltration membrane device was 90%.

[0145] (Comparative Example 2)

[0146] Figure 6 6 shows a conventional pure water production device used in this comparative example. Production device 6 is different from production device 4 in that it does not include ultrafiltration membrane device 54 and ultrafiltration membrane device 64. Using production device 6, sulfuric acid as a pH adjuster is added to raw water, and the pH of the water supplied to ultrafiltration membrane device 44 is adjusted to 7.2, and then the water is passed through ultrafiltration membrane device 44 for filtration in the same manner as in comparative example 1, thereby obtaining first permeated water and first concentrated water. Other treatments were repeated in the same manner as in comparative example 1.

[0147] The turbidity (NTU) and aluminum concentration in the mixed water of the first permeated water and the second permeated water in Examples 1 and 2 and Comparative Example; the TOC concentration, turbidity and aluminum concentration in the third permeated water; and the water recovery rate of the entire device were measured. The results are shown in Table 1. In Table 1, the mixed water of the first permeated water and the second permeated water is represented as "first permeated water and second permeated water". It should be noted that the value of "the quality of the first permeated water and the second permeated water" in Comparative Example 2 only represents the quality of the "first permeated water" because Comparative Example 2 is a treatment using a primary ultrafiltration membrane device.

[0148] [Table 1]

[0149]

[0150] (Experimental example)

[0151] The TOC concentrations of permeated water obtained by adding high-alkalinity PAC to the raw water, the first concentrated water, and the second concentrated water of Example 1 and filtering the water with an ultrafiltration device were compared.

[0152] Figure 8 Schematically shows a test device 7 used in this experimental example. Figure 8 The test device shown is equipped with: a supply device 71 for supplying treated water; a reaction tank 77 for containing treated water and PAC; a polyaluminium chloride supply device 72 for adding a specified amount of high alkalinity PAC to the reaction tank 77; and a stirrer S for stirring the treated water in the reaction tank 77. The test device 7 also includes: a pump P for conveying the treated water in the reaction tank 77 to the subsequent stage; and an ultrafiltration membrane device 74 for filtering the treated water added with high alkalinity PAC through an ultrafiltration membrane. The ultrafiltration membrane device 74 is connected with: a conveying pipe 75 for conveying its permeated water; and a concentrated water pipe 76 for discharging its concentrated water. In addition, the test device 7 is equipped with: an air compressor (not shown) for conveying air to the ultrafiltration membrane device during air cleaning.

[0153] (Experimental Example 1)

[0154] The raw water of Example 1 was used as the treated water and contained in the reaction tank 77, and a high alkalinity PAC with a concentration of 20 mg / L converted to Al2O3 was added to the treated water. Then, the treated water in the reaction tank 77 was passed to the ultrafiltration membrane 74, and filtered with a water recovery rate of 90%. Then, the water flow was stopped, the ultrafiltration membrane was backwashed, and the treatment was restarted after backwashing. This process was repeated several times to collect the permeated water. Backwashing was carried out by air backwashing and air bubbling in the component. It should be noted that as an ultrafiltration membrane device, an ultrafiltration device having an ultrafiltration (UF) membrane made of PDVF (polyvinylidene fluoride) was used. The ultrafiltration (UF) membrane made of PDVF (polyvinylidene fluoride) is a test prototype component with a hollow fiber added, an external pressure type, and a membrane area of ​​10 cm 2 , nominal pore size 0.02 μm, and the supply pressure of raw water to the ultrafiltration membrane device was set to 0.06 MPa.

[0155] (Experimental Example 2, Experimental Example 3)

[0156] In Experimental Example 2, the treated water was used as the first concentrated water of Example 1 and high alkalinity PAC was added thereto. In Experimental Example 3, the treated water was used as the second concentrated water and the test was conducted in the same manner as in Experimental Example 1. That is, after adding PAC, water was passed through the ultrafiltration membrane and filtered. Then, as in Experimental Example 1, the water was stopped and the ultrafiltration membrane was backwashed, and the treatment was restarted after backwashing. This process was repeated several times and permeated water was collected.

[0157] (Experimental Example 4, Experimental Example 5)

[0158] In Experimental Examples 2 and 3, except that high alkalinity PAC was not added, the first concentrated water and the second concentrated water of Example 1 as the treated water were passed through the ultrafiltration membrane in the same manner as in Experimental Examples 2 and 3. After filtration, the water passing was stopped and the ultrafiltration membrane was backwashed. After backwashing, the treatment was restarted. This process was repeated several times.

[0159] The results of measuring the TOC concentration in the collected permeated water are shown in Table 2. In Experimental Examples 1, 4, and 5, TOC was hardly removed, but in Experimental Examples 2 and 3, the TOC removal rates were approximately 68% and 73%, respectively.

[0160] [Table 2]

[0161] TOC concentration of treated water (mg / L) UF membrane permeate water TOC concentration (mg / L) TOC removal rate (%) Experimental Example 1 2.0 1.7 15 Experimental Example 2 4.7 1.5 68 Experimental Example 3 8.3 2.2 73 Experimental Example 4 4.7 4.3 9 Experimental Example 5 8.3 7.8 6

[0162] According to the embodiments and comparative examples, by adding PAC to the raw water and the second concentrated water and filtering the entire amount of the second concentrated water to which PAC is added through an ultrafiltration membrane device, clogging of the three-stage ultrafiltration membrane device can be suppressed, and the water recovery rate using the three-stage ultrafiltration membrane device can be obtained to be above 99.0%.

[0163] In addition, the turbidity in Example 2 was slightly increased compared to Example 1. This is considered to be because, in the case of low-alkalinity PAC, the flocs were slightly broken when transported from the first-stage ultrafiltration membrane device to the second-stage ultrafiltration membrane device, so the turbidity removal rate was reduced and aluminum leakage to the subsequent stage occurred.

[0164] Furthermore, according to the experimental examples, by adding high alkalinity PAC to the first concentrated water and the second concentrated water and filtering through an ultrafiltration membrane device, the total organic carbon (TOC) in the water can be reduced. Therefore, when applied to a pure water or ultrapure water manufacturing system, it is installed in the later stage to reduce the TOC removal load of the device (ultraviolet oxidation device and its later stage ion exchange device, etc.).

Claims

1. A method for producing pure water, comprising: A step of adding polyaluminium chloride to raw water to obtain first treated water; as well as The first concentrated water is obtained by filtering the first treated water through the front-stage filtration membrane device, and the first concentrated water is filtered through the rear-stage filtration membrane device in two or more filtration steps to obtain pure water as permeate water of the two or more filtration steps.

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 basicity of the polyaluminium chloride is greater than 75%.

4. 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 25 mg / L or less relative to the raw water in terms of the concentration of aluminum oxide Al 2 O 3 .

5. The manufacturing method according to claim 1, wherein: The basicity of the polyaluminium chloride is below 75%, The manufacturing method further comprises: a pH adjustment step of adjusting the pH of the raw water to which the polyaluminium chloride is to be added.

6. The manufacturing method according to claim 1 or 2, wherein: The invention further comprises at least one of the following steps: adding polyaluminium chloride to concentrated water of at least one stage of the two or more stage filtration membrane devices, and then supplying the concentrated water to the subsequent stage filtration membrane device.

7. The manufacturing method according to claim 1 or 2, wherein: The process also includes: adding polyaluminium chloride to concentrated water of at least the final stage of the filtration membrane device in the two or more stages of filtration membrane devices, thereby obtaining second treated water; and The second treated water is subjected to a full filtering process through a filtering membrane device, wherein: The permeated water obtained in the total amount filtration step is used as the raw water.

8. The manufacturing method according to claim 7, wherein: The invention also includes: a cleaning process of cleaning the filtration membrane device after the full amount filtration treatment; and A sedimentation and concentration step for separating a supernatant from the cleaning wastewater generated in the cleaning step, wherein: The supernatant was used as the raw water.

9. A method for producing pure water, comprising: A step of adding polyaluminium chloride to raw water to obtain first treated water; The process of producing pure water comprises: filtering first treated water through a front-stage filtration membrane device to obtain first concentrated water, and filtering the first concentrated water through a rear-stage filtration membrane device in two or more filtration steps to obtain pure water as permeate water of the two or more filtration membrane steps; UV oxidation process; and 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 for adding polyaluminium chloride to raw water; A two-stage or more filtration membrane device is used to filter the first treated water generated by adding polyaluminium chloride to the raw water; A concentrated water pipe for supplying concentrated water from the front-stage filter membrane device in the two or more-stage filter membrane devices to the rear-stage filter membrane device; as well as A plurality of delivery pipes are used to deliver the permeated water of the two or more stages of filtration membrane devices to obtain pure water.

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

12. 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 25 mg / L or less in terms of the concentration of aluminium oxide Al 2 O 3 relative to the raw water.

13. The manufacturing device according to claim 10, wherein: The basicity of the polyaluminium chloride is below 75%, The production device further comprises: a pH adjusting device for adjusting the pH of raw water to which the polyaluminium chloride is to be added.

14. The manufacturing device according to claim 10 or 11, wherein: It also has: one or more polyaluminium chloride supply devices, which add polyaluminium chloride to the concentrated water of at least one of the two or more filter membrane devices, wherein: The post-filtration membrane device filters the concentrated water added with the polyaluminium chloride.

15. The manufacturing device according to claim 10 or 11, wherein: It also includes: a polyaluminium chloride supply device for adding polyaluminium chloride to concentrated water of at least the final stage of the filtration membrane device in the two or more stages of filtration membrane devices; as well as The filtration membrane device filters the entire amount of the second treated water generated by adding polyaluminium chloride to the concentrated water of the final stage filtration membrane device. The production device includes a pipe for sending permeated water of the filtration membrane device that performs the total filtration to the raw water supply device to be used as the raw water.

16. The manufacturing device according to claim 15, wherein: It also has: a cleaning device for cleaning the filter membrane device for performing the full-volume filtration; A sedimentation and concentration device for separating a supernatant from the cleaning wastewater generated by the cleaning device; as well as A pipe is provided to deliver the supernatant liquid to the raw water supply device.

17. A pure water production system, comprising: The device for producing pure water according to claim 10 or 15; UV oxidation devices; and Ion exchange device.

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