JP2008036605A - Apparatus for producing purified water and method for producing purified water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce stably and efficiently purified water having a low silica concentration by reducing a silica load of water supplying to a subsequent deionizing device when treating by introducing raw water to a reverse osmosis membrane treatment device, and supplying the water permeated from the reverse osmosis membrane treatment device to an electrically regenerating deionizing device or an ion exchange device. <P>SOLUTION: An apparatus for producing purified water includes the reverse osmosis membrane treatment device provided with a reverse osmosis membrane treated with a rejection rate improving agent composed of a polymer as a principal constituent. An apparatus for producing purified water includes the reverse osmosis membrane treatment device having a means for supplying the rejection rate improving agent composed of the polymer as a principal constituent at its primary side. A method for producing purified water includes a process of treating the reverse osmosis membrane of the reverse osmosis membrane treatment device with the rejection rate improving agent composed of the polymer as a principal constituent periodically or when the rejection rate of the reverse osmosis membrane treatment device is decreased. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pure water production apparatus and a pure water production method suitably incorporated in an ultrapure water production system and the like, and more particularly to a pure water production apparatus and a pure water production method for producing pure water having a low silica concentration.

  Conventionally, an ultrapure water production system for producing high-purity pure water generally includes a reverse osmosis membrane treatment device (hereinafter referred to as “RO device”) and an electric device for advanced treatment of permeated water of this RO device. A regenerative deionization apparatus or an ion exchange apparatus (hereinafter referred to as “deionization apparatus”) is incorporated.

  In such ultrapure water production system, silica contained in about 10 to 50 mg / L of water used as raw water for city water, industrial water and groundwater is a reverse osmosis membrane (hereinafter referred to as “RO membrane”). However, it is difficult to remove, for example, even RO membranes with a sodium chloride rejection rate of 99% or more cause silica permeation of about 0.2 to 1 mg / L. It is a load of the ion device.

  On the other hand, in recent years, it has become possible to fabricate a circuit having a line width of 65 nm or less due to progress in semiconductor circuit formation technology. Along with this, the required water quality for ultrapure water is also increasing, and it is desired to develop a pure water production apparatus and a pure water production method that reduce the load of post-treatment and realize pure water production at a higher level.

  2. Description of the Related Art Conventionally, in order to reduce the silica load of water supply to a deionization apparatus such as an electric regeneration type deionization apparatus subsequent to the RO apparatus, a method in which the previous RO apparatus is installed in multiple stages (for example, JP, 2004-33976, A, etc.). However, providing the RO apparatus in multiple stages in this way has a problem such as an increase in equipment size.

  By the way, the applicant of the present application has previously proposed an RO membrane in which the blocking rate of inorganic electrolytes and water-soluble organic substances is improved by treating with an ionic polymer (Japanese Patent Application Laid-Open No. 2006-110520). However, this publication describes that the RO membrane is treated with an ionic polymer, thereby improving the rejection of completely dissociated inorganic electrolytes such as NaCl and water-soluble organic substances such as isopropyl alcohol. However, there is no description about removal of inorganic components that are difficult to ionize such as silica.

Further, there is no description or suggestion about using an RO membrane treated with a rejection improving agent in combination with an electric regeneration type deionization apparatus or ion exchange apparatus.
JP 2004-33976 A JP 2006-110520 A

  The present invention solves the above-mentioned conventional problems, introduces raw water into the RO device, supplies the permeated water of the RO device to the electric regeneration type deionization device or ion exchange device, and processes the latter. An object of the present invention is to provide an apparatus and a method for producing pure water having a low silica concentration stably and efficiently by reducing the silica load of water supplied to the water.

  The pure water production apparatus according to claim 1 has a reverse osmosis membrane treatment device and an electric regeneration type deionization device or an ion exchange device, and the permeated water of the reverse osmosis membrane treatment device is supplied to the electric regeneration type deionization device or In the apparatus for producing pure water supplied to an ion exchange device, the reverse osmosis membrane treatment device includes a reverse osmosis membrane treated with a blocking rate improver mainly composed of a polymer.

  The pure water production apparatus according to claim 2 includes a reverse osmosis membrane treatment device and an electric regeneration deionization device or an ion exchange device, and the permeated water of the reverse osmosis membrane treatment device is supplied to the electric regeneration type deionization device or In the pure water production apparatus supplied to the ion exchange apparatus, the reverse osmosis membrane treatment apparatus has a rejection rate improver supply means for supplying a rejection rate improver mainly composed of a polymer to the primary side thereof. It is characterized by having.

  A pure water production apparatus according to a third aspect is characterized in that, in the first or second aspect, the apparatus includes a silica concentration measuring means for measuring the silica concentration in the permeated water of the reverse osmosis membrane treatment apparatus.

  The pure water production method according to claim 4 introduces raw water into a reverse osmosis membrane treatment device, and supplies the permeate from the reverse osmosis membrane treatment device to an electric regenerative deionization device or ion exchange device for treatment. In the production method, the step of treating the reverse osmosis membrane of the reverse osmosis membrane treatment device with a rejection rate improver mainly composed of a polymer, periodically or when the rejection rate of the reverse osmosis membrane treatment device decreases. It is characterized by having.

  According to the present invention, the silica rejection of the RO membrane can be increased by treating the RO membrane with a rejection rate improver mainly composed of a polymer, and the electric regeneration deionization device or ion exchange device in the subsequent stage can be increased. Pure water with a low silica concentration can be produced stably and efficiently by reducing the silica load of the water supply to the water.

  Hereinafter, embodiments of a pure water production apparatus and a pure water production method of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system diagram showing an embodiment of a pure water production apparatus and a pure water production method of the present invention. 2 and 3 are system diagrams showing an example of the RO apparatus cleaning and rejection rate improvement processing means according to the present invention.

  In the pure water production apparatus and the pure water production method of the present invention, the raw water is subjected to reverse osmosis membrane treatment (hereinafter referred to as “RO treatment”) with the RO device, and then the permeated water of the RO device is electrically regenerated deionization device or ion. The pure water is produced by supplying it to the exchange device. For the purpose of preventing clogging and fouling of the RO device, as shown in FIG. 2 is preferably provided. As the filtration device 2, a sand filtration device, an ultrafiltration membrane device, a microfiltration membrane device, a small filtration device or the like can be used. As the pretreatment device, a prefilter may be further provided, or an agglomeration treatment device may be provided.

  Further, the water supplied to the RO device 3 (RO water supply) is adjusted to have a pH of 5 to 8, particularly by adding a pH adjuster as necessary in order to prevent the scale from being generated by the concentration in the RO device 3. It is preferable to adjust the pH to 5.5 to 7.8, particularly pH 6 to 7.

  Further, in order to remove carbonic acid in the permeated water (RO permeated water) of the RO device, as shown in FIG. 1, a membrane deaerator is provided between the RO device 3 and the electric regeneration deionizer 5 at the subsequent stage. It is preferable to provide a decarboxylation device such as 4. This decarboxylation device may be provided in front of the RO device, but is preferably provided between the RO device 3 and the electric regenerative deionization device 5 for the purpose of efficiently removing carbonic acid.

  The RO device 3 is normally used in one stage, but may be provided in two or more stages to improve water quality.

  Since the electric regeneration type deionization apparatus 5 does not require a chemical for regeneration, it is preferably used in the field of pure water production. Instead of the electric regeneration type deionization apparatus 5, an ion exchange apparatus (ion exchange resin tower) is used. ) May be provided. Moreover, when it is necessary to perform deionization processing highly, such a deionization apparatus may be provided in multiple stages. When the deionization apparatus is provided in multiple stages, the same apparatus may be provided in multiple stages, or different apparatuses may be provided in multiple stages. For example, an electric regeneration type deionization device may be provided at the front stage and an ion exchange device may be provided at the rear stage.

Furthermore, it is preferable to provide a silica concentration measuring means for measuring the silica concentration of RO permeated water supplied to the electric regeneration type deionization apparatus 5 not shown in FIG. This is because by monitoring the silica removal rate of the RO device 3, the RO membrane can be appropriately replaced or the rejection rate improving process according to the present invention can be performed. The silica concentration measuring means, _0.01~1mg-SiO 2 / L measurable up, molybdenum blue method, can be suitably employed molybdenum yellow method.

  1 is a sub-system (usually a pure water tank, an ultraviolet sterilizer, a non-regenerative ion exchanger, an ultrafiltration membrane) normally used in an ultrapure water production apparatus. Comprised of devices).

  In the present invention, the RO membrane of the RO device in the previous stage of the electric regeneration type deionization apparatus (or ion exchange apparatus) of such a pure water production apparatus is treated with a blocking rate improver mainly composed of a polymer (hereinafter referred to as “reaction rate improving agent”). This processing is referred to as “blocking rate improvement processing”.)

  The RO membrane loaded in the RO device is a liquid separation membrane that applies a pressure higher than the osmotic pressure difference between solutions through the membrane to the high concentration side to block the solute and permeate the solvent. Examples of the membrane structure of the RO membrane include polymer membranes such as asymmetric membranes and composite membranes. Examples of the RO membrane material applied to the present invention include aromatic polyamides, aliphatic polyamides, polyamide materials such as composite materials thereof, and cellulose materials such as cellulose acetate. Among these, the rejection improvement process according to the present invention can be particularly suitably applied to the aromatic polyamide RO membrane.

  There is no restriction | limiting in particular about the form of RO membrane module, For example, a tubular membrane module, a planar membrane module, a spiral membrane module, a hollow fiber membrane module etc. are applicable.

  As a blocking rate improver for treating such an RO membrane, a polymer having a polyalkylene glycol chain having a weight average molecular weight of 2000 to 6000 or an ionic polymer having a weight average molecular weight of 100,000 or more is suitable. Can be used.

  The polymer polyalkylene glycol chain having a polyalkylene glycol chain having a weight average molecular weight of 2000 to 6000 has a structure that is considered to be formed by dehydration polycondensation of alkylene glycol. It can be produced by cationic polymerization with proton initiation.

  Examples of the polymer polyalkylene glycol chain having a polyalkylene glycol chain having a weight average molecular weight of 2000 to 6000 include a polyethylene glycol chain, a polypropylene glycol chain, a polytrimethylene glycol chain, and a polytetramethylene glycol chain. . Among these, as the polyalkylene glycol chain, a polyethylene glycol chain is preferable. That is, since a polymer having a polyethylene glycol chain is highly water-soluble, it is easy to handle as a blocking rate improver and has a high affinity for the composite membrane surface, so that there is little degradation in performance over time after treatment.

  These polyalkylene glycol chains can be formed, for example, by ring-opening polymerization of ethylene oxide, propylene oxide, oxetane, tetrahydrofuran or the like.

  The polymer having a polyalkylene glycol chain has a weight average molecular weight of 2000 to 6000, preferably 3000 to 5000. When the weight average molecular weight of the polyalkylene glycol chain is less than 2000, the effect of improving the rejection rate cannot be sufficiently obtained, and the fixability after the processing may be lowered. When the weight average molecular weight of the polyalkylene glycol chain exceeds 6000, the permeation flux of the RO membrane is greatly reduced by the treatment, and the operation pressure may be increased. This weight average molecular weight can be obtained by analyzing an aqueous solution of a polymer comprising a polyalkylene glycol chain by gel permeation chromatography (GPC) and converting the obtained chromatogram to the molecular weight of a polyethylene oxide standard product. .

As the polymer having a polyalkylene glycol chain, a polymer in which an ionic group is introduced into the polyalkylene glycol chain can be used. Examples of the ionic group to be introduced include a sulfo group (—SO ₃ H), a carboxyl group (—COOH), an amino group (—NH ₂ ), a quaternary ammonium group (—N ⁺ R ₃ X ⁻ ), and the like. In order to prevent the occurrence of scale, RO membranes often pass water under weakly acidic conditions, and in that case, they become anion-rich, so that a strong anionic sulfo group is introduced. Is effective.

  The method for introducing a sulfo group into the polyalkylene glycol chain is not particularly limited. For example, by adding epoxypropanol and sodium sulfite to a polyethylene glycol aqueous solution and reacting under a reflux condition of 70 to 90 ° C., the following formula Examples thereof include a method of synthesizing a sulfonated polyethylene glycol represented by [1] or formula [2].

In the above formulas [1] and [2], (X, Y) is (H, CH ₂ OH) or (CH ₂ OH, H).

  The sulfonated polyethylene glycol is not limited to those represented by the above formula [1] or [2]. For example, a polymer represented by the following formula [3], a polymer represented by the following formula [4] Etc. can be illustrated.

  As the ionic polymer having a weight average molecular weight of 100,000 or more, a cationic polymer or an anionic polymer can be suitably used. In the case of an amphoteric polymer, it is preferable that the number of cationic structural units or anionic structural units is larger than that of other structural units, and the whole is biased toward cationic or anionic properties.

  Examples of the cationic polymer include primary amine compounds such as polyvinylamine, polyallylamine, polyacrylamide, and chitosan, secondary amine compounds such as polyethyleneimine, poly (dimethylaminoethyl acrylate), and poly (methacrylic acid). Tertiary amine compounds such as dimethylaminoethyl), quaternary ammonium compounds such as those obtained by adding a quaternary ammonium group to polystyrene, compounds having a heterocyclic ring such as polyvinylamidine, polyvinylpyridine, polypyrrole, polyvinyldiazole, etc. Can be mentioned. As the cationic polymer, copolymers having a plurality of these structures can also be used. Among these, compounds having a heterocyclic ring can be preferably used, and polyvinylamidine can be particularly preferably used.

Polyvinylamidine is a cationic polymer having a structural unit represented by the following general formula [5]. However, in General formula [5], R < ¹ > -R < ⁴ > is respectively independently C1-C3 alkyl groups, such as hydrogen or a methyl group.

  The cationic polymer having the structural unit represented by the general formula [5] includes acrylonitrile or methacrylonitrile, N-vinylcarboxylic acid amide, N-isopropenylcarboxylic acid amide, N-vinylcarboxylic acid imide, or N- It can be produced by copolymerizing isopropenylcarboxylic acid imide, hydrolyzing the resulting copolymer, and amidineating. In addition to the structural unit represented by the general formula [5], the polyvinylamidine produced by such a method includes a cyano group derived from acrylonitrile and the like, a carbamoyl group generated by hydrolysis of the cyano group, and N-vinylcarboxylic acid. It may have an amino group generated by hydrolysis of an acid amide unit or the like. As a commercial product, a cationic polymer flocculant “Diaflock (registered trademark) KP7000” manufactured by Dianitics can be used. Polyvinylamidine has a high cation density since the nitrogen atom of the heterocyclic ring and the nitrogen atom of the primary amine have a cationic property, and a high blocking rate improving effect is exhibited against the cationic species in water. In the case of a polymer having another heterocyclic ring, the cation density can be increased by adding a cationic functional group such as a primary amine.

  Examples of the anionic polymer include polymers having a carboxyl group such as polyacrylic acid and polymethacrylic acid, and polymers having a sulfonic acid group such as polystyrene sulfonic acid, dextran sulfate and polyvinyl sulfonic acid. it can. As the anionic polymer, a copolymer having a plurality of these structures can also be used. Since the sulfonic acid group of polystyrene sulfonic acid has strong anionic property, it can be stably adsorbed on the surface of the RO membrane to improve the blocking performance, hold it long, and greatly reduce the permeation flux. Absent.

  These ionic polymers can also be used as salts having a counter ion. Examples of the salt having a counter ion include polyvinylamidine hydrochloride, polyacrylic acid sodium salt, and polystyrenesulfonic acid sodium salt.

  The weight average molecular weight of these ionic polymers is 100,000 or more, more preferably 300,000 or more, and still more preferably 1,000,000 or more. When the weight average molecular weight of the ionic polymer is less than 100,000, it is difficult to stably adsorb the ionic polymer to the RO membrane and maintain the state for a long time, and the treatment rate improvement treatment effect is sufficiently obtained. There is a risk of not. The weight average molecular weight is obtained by analyzing an aqueous solution of an ionic polymer by gel permeation chromatography and converting the obtained chromatogram into the molecular weight of a polyethylene oxide standard product. In a high molecular weight region where a polyethylene oxide standard product cannot be obtained, the weight average molecular weight can be determined by a light scattering method, an ultracentrifugation method, or the like.

  By treating the RO membrane with such a blocking rate improver and adsorbing the above-described polymer of the blocking rate improving agent to the RO membrane surface, the silica blocking rate of the RO membrane can be increased.

  In addition, the rejection rate improvement agent which has as a main component the polymer used by this invention can contain the rejection rate confirmation tracer which consists of an inorganic electrolyte or a water-soluble organic compound. By passing water containing the tracer together with the polymer described above through the RO membrane, the blocking rate of the RO membrane can be confirmed over time, and the continuation or stop of the treatment can be determined. That is, when the tracer concentration of the permeated water reaches a predetermined value, it is determined that the RO membrane rejection rate has reached a predetermined value, and the rejection rate improvement process ends. According to this method, the contact time (water passage time) between the aqueous solution for improving the rejection rate and the RO membrane can be controlled to a necessary and sufficient minimum length, and normal operation of the RO membrane can be started immediately. it can. Moreover, also when performing the rejection rate improvement process of multiple times using different rejection rate improvement agents, the process of multiple times can be performed efficiently, without losing the timing of switching.

  Examples of the inorganic electrolyte used as the tracer include sodium chloride. Examples of the water-soluble organic compound used as the tracer include isopropyl alcohol. The concentration of the tracer in the water passing through the RO membrane is preferably 100 to 1,000 mg / L, and more preferably 300 to 700 mg / L.

  There is no particular limitation on the RO membrane rejection rate improving method, for example, an aqueous solution containing the rejection rate improving agent can be passed through a module equipped with the RO membrane, or the RO membrane can be added to the aqueous solution containing the rejection rate improving agent. Can also be immersed. When the RO membrane is attached to the module or when the aqueous solution containing the blocking rate improver is passed with the RO membrane attached to the module, the aqueous solution containing the blocking rate improver is pure water or RO. It can be prepared from the permeated water of the membrane, or it can be prepared from water to be treated that passes through the RO membrane. When preparing an aqueous solution containing a rejection rate improver from the treated water that passes through the RO membrane, confirm the change in the rejection rate over time by measuring the rejection rate of the components contained in the treated water. Can do. It is also possible to always inject the rejection rate improver into the water to be treated.

  The above-mentioned polymer concentration of the aqueous solution for improving the rejection rate used for the RO membrane rejection rate improving treatment is preferably about 0.05 to 50 mg / L. The more preferable polymer concentration of the aqueous solution for increasing the rejection rate varies depending on the type of polymer used. For example, in the case of the polymer having a polyalkylene glycol chain having a weight average molecular weight of 2000 to 6000, 0.1 to 1 mg / L. The cationic polymer having a molecular weight of 100,000 or more is preferably 0.1 to 5 mg / L, and the anionic polymer having a molecular weight of 100,000 or more is preferably 0.1 to 20 mg / L. If the polymer concentration is lower than this, it may take a long time to improve the rejection rate. When the polymer concentration exceeds 50 mg / L, the viscosity of the aqueous solution increases, and there is a possibility that the water flow resistance to the RO membrane increases. On the other hand, when the polymer concentration exceeds 50 mg / L, an unnecessarily thick adsorbing layer is formed, and the effect of improving the rejection rate may be weakened due to concentration polarization.

  It is preferable that the time per one time of passing the aqueous solution containing the rejection rate improver is 2 to 24 hours. If the polymer concentration in the aqueous solution is increased, the water passing time can be shortened, but the permeation flux may be greatly reduced.

  During this water flow, the permeated water discharge valve of the RO device can be closed, but by performing the treatment while taking out the permeated water, the device can be efficiently treated without stopping the device.

  The timing of the rejection rate improvement processing can be performed periodically, but may be performed when the silica rejection rate of the RO membrane is reduced. Also, in the RO device, chemical cleaning of the RO device is performed regularly or when the membrane flux decreases. However, since the blocking rate improver adsorbed on the RO membrane is also removed by chemical cleaning, Is preferably treated with a rejection improving agent.

  As the chemical cleaning treatment, a combined treatment of acid washing at pH 4 or less, preferably pH 1 to 3, and alkali washing at pH 10 or more, preferably pH 10 to 13 is suitable. Acids include hydrochloric acid and nitric acid. Citric acid and oxalic acid can be used, and sodium hydroxide or the like can be used as the alkali.

  In addition, it is preferable that the pressure at the time of water flow of a rejection rate improving agent aqueous solution is made into the same grade as the pressure used at the time of carrying out normal water treatment. By doing so, adsorption of the polymer to the film surface can be promoted.

  In the rejection rate processing according to the present invention, the RO membrane can be processed a plurality of times using the aforementioned rejection rate improver. By performing the rejection improvement process a plurality of times, it is possible to improve the improvement effect of the silica rejection, the stability of the improved rejection ratio, and the resistance to film contaminants. In the treatment of a plurality of times, as the RO membrane rejection rate improver, the same rejection rate improver can be used repeatedly, or different rejection rate improvers can be used sequentially.

  In order to improve the silica rejection of the RO membrane, the membrane surface is preferably anionic. Therefore, in the above-described treatment for alternately adsorbing the cationic polymer and the anionic polymer, it is preferable to finally treat with the anionic polymer. In the treatment using the cationic polymer and the anionic polymer in combination, the treatment with the cationic polymer / the treatment with the anionic polymer is performed once, and this treatment is preferably performed a plurality of times, preferably 6 times or less. This is because the rejection rate can be further improved by carrying out a plurality of times, but even if the number is more than 6 times, the effect is not improved much.

  When processing with a different polymer, it is preferable to rinse with pure water (RO permeated water) at the time of change.

  In the present invention, by treating the RO membrane with a blocking ratio improver mainly composed of a polymer, treated water having a silica concentration of 0.5 mg / L or less, particularly 0.3 mg / L or less is used as RO permeate. It is preferable to improve the silica rejection of the RO membrane so that it can be obtained. By obtaining such low-silica RO permeated water, it can be treated with an electric regeneration deionizer or ion exchanger to obtain high-quality pure water with a silica concentration of 0.1 mg / L or less. .

  Next, with reference to FIGS. 2 and 3, the procedure for cleaning the RO membrane and improving the rejection rate of the RO device according to the present invention will be described.

2 and 3, 11 is a treated water tank, 12 is a treated water tank, 13 is an alkaline cleaning liquid tank, 14 is an acidic cleaning liquid tank, 15 is an anionic polymer aqueous solution tank, and 16 is a cationic polymeric aqueous solution. Tank 20, RO membrane module, P ₁ is a high pressure pump, P ₂ is a pump for cleaning liquid, P ₃ is a pump for anionic polymer aqueous solution, and P ₄ is a pump for cationic polymer aqueous solution. V _{1 to} V ₂₂ are valves. 2 and 3 show main pipes and valves, and other valves, gauges and pipes are not shown.

2 and 3, when the treated water is RO-treated, the valves V ₁ , V ₂ , V ₅ , V ₄ , V ₂₂ , V ₃ are opened, the other valves are closed, and the high-pressure pump P ₁ is turned on. By operating, the treated water in the treated water tank 11 is supplied to the RO membrane module 20 to separate the RO membrane, and the permeated water is taken out of the system. Further, the concentrated water in order to prevent the concentration of the portion of RO water with returning to the treatment water tank 11 is discharged to the outside of the system concentrated water valve V ₃ is opened. Further, the valves V ₆ and V ₁₇ are opened, and the permeate is stored in the treated water tank 12. In some cases, the valves V ₁₈ , V ₁₉ , V ₂₀ , V ₂₁ are opened, and the permeate is used for the alkaline cleaning liquid tank 13, the acidic cleaning liquid tank 14, the anionic polymer aqueous solution tank 15, and the cationic polymer aqueous solution. It can be fed to the tank 16 and used for dilution, preparation, etc. of a cleaning liquid or a polymer aqueous solution.

When performing chemical cleaning when the RO membrane permeation flux is reduced by performing RO treatment, the high-pressure pump P ₁ is stopped, the valves V ₈ , V ₂ , V ₄ , V ₁₃ are opened, etc. And the cleaning liquid pump P ₂ is operated to introduce the alkaline cleaning liquid in the alkaline cleaning liquid tank 13 to the primary side of the RO membrane module 20, and then circulate back to the tank 13 again. At this time, the valve V ₅ is opened, a part of the cleaning liquid by membrane permeation may be discharged out of the system. Alternatively, the valves V ₆ and V ₁₈ may be opened to return the cleaning liquid that has passed through the membrane to the tank 13. A predetermined time, after circulating the alkaline washing solution, a certain time chemical stops the washing liquid pump P ₂ after standing held in some cases, the drain pipe provided in the alkaline washing solution tank 13 the alkaline washing solution (FIG. (Not shown).

Next, V ₉ , V ₂ , V ₄ , V ₁₄ are opened, the other valves are closed, and the acidic cleaning liquid in the acidic cleaning liquid tank 14 is introduced to the primary side of the RO membrane module 20, and then returned to the tank 14 again. To circulate. At this time, the valve V ₅ is opened, a part of the cleaning liquid by membrane permeation may be discharged out of the system. Alternatively, the valves V ₆ and V ₁₉ may be opened to return the cleaning liquid that has passed through the membrane to the tank 14. A predetermined time, after circulating the acidic cleaning solution, a certain time chemical stops the washing liquid pump P ₂ after standing held in some cases, the drain tube provided with an acidic cleaning solution is acidified solution tank 14 (Fig. (Not shown).

Next, the valves V ₇ , V ₂ , V ₄ , V ₃ are opened, the other valves are closed, the primary side of the RO membrane module 20 is washed with the treated water in the treated water tank 12, and the washing drainage is supplied to the valve V ₃ to be discharged out of the system. The cleaning drainage may be discharged from drain pipes provided in the cleaning liquid tanks 13 and 14. This cleaning (rinsing) with the treated water can be performed between the cleaning with the alkaline cleaning liquid and the cleaning with the acidic cleaning liquid. Further, either the cleaning with the alkaline cleaning liquid or the cleaning with the acidic cleaning liquid may be performed first, or may be repeated twice or more alternately.

In FIG. 2, in the case of performing the rejection improvement process with the aqueous polymer solution, V ₁₀ , V ₂ , V ₄ , V ₁₅ are opened, the other valves are closed, and the cleaning liquid pump P ₂ is operated to anionic. The anionic polymer aqueous solution in the polymer aqueous solution tank 15 is introduced to the primary side of the RO membrane module 20 and then circulated back to the tank 15 again. At this time, the valve V ₅ may be opened to allow a part of the polymer aqueous solution to pass through the membrane and be discharged out of the system. However, the valves V ₆ and V ₂₀ may be opened to pass the membrane aqueous solution through the tank. It is preferable to return to 15. After the anionic polymer aqueous solution is circulated for a predetermined time, the anionic polymer aqueous solution is discharged out of the system through a drain pipe (not shown) provided in the anionic polymer aqueous solution tank 15.

Next, after V ₁₁ , V ₂ , V ₄ , V ₁₆ are opened and the other valves are closed, the cationic polymer aqueous solution in the cationic polymer aqueous solution tank 16 is introduced to the primary side of the RO membrane module 20. Circulate to return to the tank 16 again. At this time, the valve V ₅ may be opened to allow a part of the polymer aqueous solution to permeate the membrane and be discharged out of the system. However, the valves V ₆ and V ₂₁ may be opened and the membrane permeated polymer aqueous solution may be stored in the tank. It is preferable to return to 16. After circulating the cationic polymer aqueous solution for a predetermined time, the cationic polymer aqueous solution is discharged out of the system from a drain pipe (not shown) provided in the cationic polymer aqueous solution tank 16.

Next, the valve V ₇ , V ₂ , V ₃ , V ₆ and the valve V ₂₀ or V ₂₁ are opened, the other valves are closed, and the primary side of the RO membrane module 20 is washed with treated water in the treated water tank 12. , a portion of the wash effluent out of the system via a valve V _3, the remainder is discharged therefrom through one of the polymer solution tank 15 or 16 to the outside of the system. This washing (rinsing) with the treated water is preferably performed between the treatment with the anionic polymer aqueous solution and the treatment with the cationic polymer aqueous solution. As described above, either the treatment with the anionic polymer aqueous solution or the treatment with the cationic polymer may be performed first, or may be repeated two or more times alternately. It is preferable to use a treatment with an aqueous solution.

In FIG. 3, when performing the rejection improvement process with the polymer aqueous solution, first, the valve V ₁₀ is opened, the pump P ₃ is operated, and the anionic polymer aqueous solution in the anionic polymer aqueous solution tank 15 is removed. After introducing into the water tank 11 to be treated, the high pressure pump P ₁ is operated, the valves V ₂ , V ₄ , V ₂₂ are opened, and the other valves are closed. Is introduced to the primary side of the RO membrane module 20 and then circulated back to the tank 11 again. At this time, the valves V ₅ and V ₃ are opened to allow a part of the polymer aqueous solution to pass through the membrane to be supplied to the electric regeneration deionization device 5 and to discharge a part of the polymer aqueous solution out of the system. It is preferable. By doing in this way, the time which stops operation | movement of an apparatus can be shortened. A predetermined time, after circulating the anionic polymer solution, a pump P ₃ stop closes the valve V _10, to stop the introduction of the anionic polymer solution.

Then, the valve V ₁₁ is opened, the pump P ₄ is operated, the cationic polymer solution in the cationic aqueous polymer solution tank 16 is introduced into the treated water tank 11, then actuates the high-pressure pump P ₁ Then, the valves V ₂ , V ₄ , V ₂₂ are opened and the other valves are closed, and the cationic polymer aqueous solution in the water tank 11 to be treated is introduced to the primary side of the RO membrane module 20 and then returned to the tank 11 again. So that it circulates. At this time, the valves V ₅ and V ₃ are opened to allow a part of the polymer aqueous solution to pass through the membrane to be supplied to the electric regeneration deionization device 5 and to discharge a part of the polymer aqueous solution out of the system. It is preferable. By doing in this way, the time which stops operation | movement of an apparatus can be shortened. After circulating the cationic polymer aqueous solution for a predetermined time, the valve V ₁₁ is closed and the pump P ₄ is stopped to stop the introduction of the cationic polymer aqueous solution.

Next, the valves V ₇ , V ₂ , V ₃ are opened, the other valves are closed, the high-pressure pump P ₁ is stopped, and the pump P ₂ is operated to treat the RO membrane module 20 with the treated water in the treated water tank 12. with washing the primary side, the wash effluent is discharged out of the system via a valve V _3. This washing (rinsing) with treated water can be performed between the treatment with the anionic polymer aqueous solution and the treatment with the cationic polymer aqueous solution, but after stopping the introduction of the polymer aqueous solution, The RO treatment can be omitted by carrying out the predetermined time (about three times the residence time of the water tank 11 to be treated). Either the treatment with the anionic polymer aqueous solution or the treatment with the cationic polymer aqueous solution may be performed first, or may be repeated twice or more, but finally the treatment with the anionic polymer aqueous solution. It is preferable that

  2 and 3 show an example of the procedure for cleaning the RO device and improving the rejection rate according to the present invention, and the present invention is not limited to the illustrated method.

  In FIG. 2, chemical cleaning and rejection rate improvement processing are performed using RO permeated water. In FIG. 3, chemical cleaning is performed using RO permeated water, and rejection rate improvement processing is performed using treated water. Separately produced pure water or soft water may be used. In addition, the tank can be shared or omitted. Further, the rinsing step after the rejection rate improving process can be omitted, and the polymer aqueous solution may be injected into a pipe connecting the water tank 11 to be treated and the RO membrane module 2.

  Hereinafter, the present invention will be described more specifically with reference to experimental examples, examples and comparative examples.

Experimental example 1
Using an electric regenerative deionization device (“KCDI-04” manufactured by Kurita Kogyo Co., Ltd.), deionization treatment was performed by changing the silica concentration of the feed water, and the silica concentration of the feed water was determined from the silica concentration of the obtained treated water. Table 1 shows the relationship between the water concentration and the silica concentration of the treated water.

  As is apparent from Table 1, when the silica concentration of the feed water exceeds 0.35 mg / L, the quality of the treated water starts to deteriorate, and when the concentration exceeds 0.5 mg / L, the silica concentration of the treated water becomes 0.1 mg / L. Exceed. From this, it can be said that it is important to maintain the high treated water quality to make the silica concentration of the feed water of the electric regeneration type deionizer 0.5 mg / L or less, desirably 0.3 mg / L or less.

Experimental example 2
Three 4-inch spiral RO membranes “ES20-D4” manufactured by Nitto Denko Corporation were arranged in series in the same vessel, and the RO treatment was performed by a method in which the concentrated water was sequentially supplied to the next stage.

  The recovery rate (= permeated water amount / treated water amount) was 50%, and tap water (pH 5.9) treated with activated carbon was used as RO water supply. The silica concentration in the water to be treated was 14 to 20 mg / L.

  Prior to this RO treatment, the apparatus shown in FIG. 2 was used to add the aqueous solution containing 4 mg / L of polyvinylamidine having a weight average molecular weight of 3.5 million and 400 mg / L of sodium chloride to the 3-stage RO apparatus, and the recovery rate was 50%. And then rinsing with pure water twice, and thereafter, an aqueous solution containing 5 mg / L of polystyrene sulfonate with a weight average molecular weight of 1,000,000 and 400 mg / L of sodium chloride is 0.75 MPa, and the recovery rate is 50%. After passing water for 20 hours, rinsing with pure water was performed twice to perform the RO membrane blocking rate improvement treatment with a cationic polymer and an anionic polymer.

  Here, the pure water rinsing is a process of passing pure water obtained by treating RO water supply with an RO membrane at a supply pressure of 0.25 MPa for 0.25 hours.

  For comparison, the RO treatment was performed in the same manner for the case of using an RO membrane that has not been subjected to the inhibition rate improvement treatment.

  Table 2 shows the water temperature, inlet (RO treated water), and outlet when using a normal membrane (RO membrane not subjected to the rejection improvement process) and a rejection improvement membrane (RO membrane subjected to the rejection improvement process). The silica concentration of (permeated water), the silica removal rate determined from these silica concentrations, and the effective membrane surface pressure are shown.

  As is clear from Table 2, when the blocking rate improving membrane is used, a higher value is required as the effective membrane surface pressure because the polymer is adsorbed, but the outlet silica concentration is 0.3 mg / L. Hereinafter, good results with a silica removal rate of 98% or more are obtained.

Comparative Example 1
In a pure water production system having a microfiltration membrane device, an activated carbon tower, an RO device, a membrane deaeration device, and an electric regenerative deionization device in this order, the RO device is an 8-inch spiral RO membrane “ES20-” manufactured by Nitto Denko Corporation. Using an RO apparatus loaded with “D8”, the system was operated at an operation pressure of 0.70 MPa and a recovery rate (= permeated water amount / raw water amount) of 60%.

  Although the silica concentration of raw water is 36 mg / L, since the RO concentrated water is partially circulated, the silica concentration of the RO water supply (pH 6.3) is 45 mg / L.

  At this time, the silica concentration of the permeated water of the RO device was about 0.5 mg / L, and the silica concentration of the treated water of the electric regeneration type deionizer was 0.08 to 0.15 mg / L.

Example 1
After the treatment in Comparative Example 1, the RO membrane of the RO device was subjected to the same treatment with polyvinylamidine and sodium polystyrene sulfonate three times as in Experimental Example 2 to perform a rejection rate improving treatment. Thereafter, when the treatment was performed at a recovery rate of 60% in the same manner as in Comparative Example 1, the operating pressure increased by about 9% to 0.76 MPa. The silica concentration of RO feed water is 36 mg / L as in Comparative Example 1.

  FIG. 4 shows the silica concentration of the RO water supply, RO permeated water, and RO concentrated water at this time. The silica concentration in the RO membrane permeated water was around 0.1 mg / L, and was lowered to the level of the treated water in the electric regeneration type deionizer in Comparative Example 1.

  As a result, the silica concentration of the treated water of the electric regeneration type deionizer could be 0.03 mg / L or less.

Example 2
For the RO membrane after treatment in Comparative Example 1, sodium sulfite and 2,3-epoxy-1-propanol were reacted with polyethylene glycol having a weight average molecular weight of 4000 using the apparatus of FIG. An inhibition rate improvement treatment was performed by passing an aqueous solution containing 0.1 mg / L of molecules and 400 mg / L of sodium chloride for 15 hours at an operating pressure of 0.75 Pa and a recovery rate of 50%. Thereafter, when the treatment was carried out at a recovery rate of 60% as in Comparative Example 1, the operating pressure increased by about 20% to 0.85 MPa. The silica concentration of RO feed water is 36 mg / L as in Comparative Example 1.

  At this time, the silica concentrations of RO water supply, RO concentrated water, and RO permeated water were 45 mg / L, 90 mg / L, and 0.12 mg / L, respectively.

  From this result, it is understood that when polyethylene glycol having a sulfone group introduced is used, the increase in operating pressure is increased, but the effect of improving the rejection rate equivalent to that in Example 1 can be obtained by a single polymer aqueous solution water treatment. .

Comparative Example 2
In a pure water production system having a prefilter, activated carbon column, RO device, membrane degassing device, and ion exchange resin column in this order, a 4-inch spiral RO membrane “ES20-D4” manufactured by Nitto Denko Corporation is loaded as the RO device. The RO treatment was performed at an operating pressure of 0.7 MPa and a recovery rate (= permeated water amount / treated water amount) of 52 to 53%. As a result, the silica concentration of RO permeated water was 0.4 to 0.6 mg / L with respect to the silica concentration of 45 to 46 mg / L in the water to be treated (pH 6.2).

Example 3
The RO membrane of the RO device after treatment in Comparative Example 2 is improved by the same treatment with polyvinylamidine and sodium polystyrene sulfonate as in Experimental Example 2, except that the device of FIG. Processed. Thereafter, when the treatment was performed at a recovery rate of 52 to 53% as in Comparative Example 2, the operating pressure increased to 0.75 MPa, but the silica concentration of RO permeated water became 0.21 mg / L.

  Under these conditions, continuous operation was performed for 5000 hours, and the silica concentration of the permeated water was stable at around 0.2 mg / L. However, since the operation pressure slightly increased to 0.82 MPa, the operation was stopped and the RO membrane was washed by immersing in a pH 2 hydrochloric acid aqueous solution and a pH 12 sodium hydroxide aqueous solution for 20 hours. The silica concentration of the permeated water was 0.44 mg / L with respect to the same treated water.

  Therefore, using the apparatus of FIG. 3, after passing an aqueous solution containing 1 mg / L of polyvinylamidine having a weight average molecular weight of 3.5 million and 400 mg / L of sodium chloride at 0.75 MPa and a recovery rate of 50% for 20 hours, rinsing with pure water After that, after passing an aqueous solution containing 1 mg / L of polystyrene sulfonate having a weight average molecular weight of 1 million and 400 mg / L of sodium chloride at 0.75 MPa and a recovery rate of 50% for 20 hours, rinsing with pure water The RO membrane rejection rate improvement treatment was performed with a cationic polymer and an anionic polymer. Here, the pure water rinsing is a process of passing pure water obtained by treating RO water supply with an RO membrane at a supply pressure of 0.25 MPa for 0.25 hours.

  As a result, the silica concentration of the permeated water of the RO device was 0.20 mg / L, the operating pressure was 0.76 MPa, and high silica blocking performance could be obtained again.

It is a systematic diagram showing an embodiment of a pure water production apparatus and a pure water production method of the present invention. It is a systematic diagram which shows an example of the washing | cleaning of RO apparatus which concerns on this invention, and a rejection rate improvement process means. It is a systematic diagram which shows the other example of the washing | cleaning of RO apparatus which concerns on this invention, and a rejection rate improvement process means. 3 is a graph showing the results of Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Activated carbon tower 2 Filtration apparatus 3 RO apparatus 4 Membrane deaeration apparatus 5 Electric regeneration type deionization apparatus 11 Water tank 12 To-be-treated water tank 13 Tank for alkaline washing liquid 14 Tank for acidic washing liquid 15 Tank for anionic polymer aqueous solution 16 Cation Polymeric Polymer Aqueous Tank 20 RO Membrane Module

Claims (4)

A pure osmosis treatment device and an electric regeneration deionization device or ion exchange device, and the permeated water of the reverse osmosis membrane treatment device is supplied to the electric regeneration deionization device or ion exchange device. In water production equipment,
The reverse osmosis membrane treatment apparatus comprises a reverse osmosis membrane treated with a blocking rate improver composed mainly of a polymer, and a pure water production apparatus. A pure osmosis treatment device and an electric regeneration deionization device or ion exchange device, and the permeated water of the reverse osmosis membrane treatment device is supplied to the electric regeneration deionization device or ion exchange device. In water production equipment,
The reverse osmosis membrane treatment apparatus has a rejection rate improver supply means for supplying a rejection rate improver mainly composed of a polymer on the primary side thereof.   3. The pure water production apparatus according to claim 1, further comprising silica concentration measuring means for measuring the silica concentration in the permeated water of the reverse osmosis membrane treatment apparatus. In a method for producing pure water in which raw water is introduced into a reverse osmosis membrane treatment apparatus, and the permeated water of the reverse osmosis membrane treatment apparatus is supplied to an electric regeneration type deionization apparatus or ion exchange apparatus for treatment.
Having a step of treating the reverse osmosis membrane of the reverse osmosis membrane treatment device with a rejection rate improver mainly composed of a polymer periodically or when the rejection rate of the reverse osmosis membrane treatment device decreases. A method for producing pure water.

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