JP2011020032A - Treatment method of reverse osmosis membrane and reverse osmosis membrane apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method of a reverse osmosis membrane easily and uniformly increasing the rejection of a reverse osmosis membrane of a reverse osmosis membrane apparatus formed by disposing a plurality of reverse osmosis membrane modules in parallel and in multiple stages, and to provide the reverse osmosis membrane apparatus to the method. <P>SOLUTION: First stage reverse osmosis membrane modules 11, 12, 13 are connected in parallel to a manifold 10, second stage reverse osmosis membrane modules 21, 22 are connected in parallel to a manifold 20, and a third stage reverse osmosis membrane module 31 is connected to a manifold 30. Rejection enhancing agent solution in a rejection enhancing agent solution tank 40 is fed to the manifold 10, 20 or 30 and is uniformly fed to each of the modules. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for improving the blocking rate of a reverse osmosis membrane and a reverse osmosis membrane device suitable for the method.

  Permeation membranes used for water treatment, especially nanofiltration membranes, reverse osmosis membranes and other selective permeation membranes with respect to separation targets such as inorganic electrolytes and water-soluble organic substances are oxidizing substances and reducing substances present in water The required quality of treated water cannot be obtained due to the deterioration of the raw material polymer due to the influence of the above and other causes. This change may occur little by little during long-term use, or it may happen suddenly due to an accident. In order to improve the rejection rate of the permeable membrane having such a reduced rejection rate and restore the performance, a rejection rate improver is used.

  In general, an ultrapure water production system for producing high-purity pure water includes a reverse osmosis membrane device, and an electric regenerative deionization device or other ion exchange device for advanced treatment of the permeated water of the reverse osmosis membrane device. Is incorporated.

  In such an ultrapure water production system, it has been proposed to treat a reverse osmosis membrane with a blocking rate improver (for example, Patent Documents 1 and 2). Specifically, the blocking rate improving agent-containing water is passed through the reverse osmosis membrane module to improve the blocking rate of the reverse osmosis membrane of the module. Patent Document 1 describes polyvinyl methyl ether, polyvinyl alcohol, and the like as the blocking rate improver. In Patent Document 2, polyalkylene glycol having a weight average molecular weight of 1,000 to 10,000 is shown as a blocking rate improver.

  Further, in Patent Document 1, in a reverse osmosis membrane device in which reverse osmosis membrane modules are arranged in parallel and in multiple stages, the reverse osmosis of the module is performed by passing water containing a blocking rate improver only through a specific reverse osmosis membrane module. It describes that only the film is subjected to a treatment for improving the rejection.

JP 2008-155123 A JP2009-22886

  The present invention provides a reverse osmosis membrane treatment method capable of easily and evenly improving the rejection rate of a reverse osmosis membrane device of a reverse osmosis membrane device in which a plurality of reverse osmosis membrane modules are arranged in parallel and in multiple stages, and suitable for this Another object of the present invention is to provide a reverse osmosis membrane device.

  The method for treating a reverse osmosis membrane according to claim 1 is characterized in that the reverse osmosis membrane module of the reverse osmosis membrane device in which the reverse osmosis membrane modules are arranged in multiple stages and the reverse osmosis membrane modules are arranged in parallel at least in some stages. In the improvement treatment method, the reverse osmosis membrane device is provided with a manifold on the inflow side of the water to be treated in the stage where the reverse osmosis membrane module is installed in parallel, and the manifold is subjected to the treatment from the manifold to each reverse osmosis membrane module. The reverse osmosis membrane of the reverse osmosis membrane module is constructed by introducing water, supplying a rejection rate improver to the manifold, and introducing water containing the rejection rate improver from the manifold into the reverse osmosis membrane module. It is characterized in that a rejection rate improvement process is performed.

  The method for treating a reverse osmosis membrane according to claim 2 is the method according to claim 1, wherein the water containing the blocking rate improving agent that has passed through the reverse osmosis membrane module is not passed through the reverse osmosis membrane module in the next stage. It is characterized by being discharged.

  The reverse osmosis membrane device according to claim 3 is a reverse osmosis membrane device in which reverse osmosis membrane modules are installed in multiple stages, and at least some of the reverse osmosis membrane modules are installed in parallel. In this stage, a manifold is provided on the inflow side of the water to be treated in the stage, and the water to be treated is introduced from the manifold to each reverse osmosis membrane module so that the rejection rate improver has a target concentration in the manifold. A means for adding is provided.

  In the reverse osmosis membrane treatment method and reverse osmosis membrane device of the present invention, a manifold is arranged on the inflow side of the reverse osmosis membrane module in the stage where the reverse osmosis membrane modules are installed in parallel, and water is treated from the manifold to each module. The reverse osmosis membrane device is configured so as to introduce the above. Then, when the reverse osmosis membrane of the reverse osmosis membrane module is subjected to the treatment for improving the rejection rate, water containing the rejection rate improving agent is supplied to the manifold.

  By supplying water containing the blocking rate improver to the manifold in this way, the blocking rate improving agent-containing water having a predetermined concentration can be evenly supplied from the manifold to each module in the same stage, and the reverse osmosis membrane of each module can be provided. It is possible to uniformly improve the rejection rate.

  In addition, when manifolds are provided for each of the plurality of stages, by supplying each manifold with water containing the same concentration of blocking rate improver so that the amount of water passing through each module is the same, the reverse of each stage is achieved. The permeation membrane module can be uniformly processed to improve the rejection rate.

  It is preferable that the blocking rate improver-containing water that has passed through the reverse osmosis membrane module is discharged out of the reverse osmosis membrane device without passing through the reverse osmosis membrane module in the next stage. This is because the reverse osmosis membrane module of the next stage is also subjected to the rejection improvement process with the rejection concentration improver-containing water having the target concentration.

It is a flowchart of the reverse osmosis membrane apparatus which concerns on embodiment. It is a flowchart which shows the blocking ratio improvement processing method of the module of the 1st step. It is a flowchart which shows the rejection rate improvement processing method of the module of the 2nd step. It is a flowchart which shows the rejection rate improvement processing method of the 3rd step | paragraph module. It is a flowchart which shows the rejection rate improvement processing method of the module of all the stages.

  The embodiment will be described below with reference to FIGS. In this embodiment, three reverse osmosis membrane modules are installed in parallel in the first stage, two reverse osmosis membrane modules are installed in parallel in the second stage, and one reverse osmosis membrane module is installed in the third stage. However, the number of stages and the number of parallel reverse osmosis membrane modules in each stage are not limited to this.

<Flow during reverse osmosis membrane separation treatment of raw water>
First, with reference to FIG. 1, the structure which carries out reverse osmosis membrane processing of raw | natural water is demonstrated. The raw water is introduced from the raw water tank 1 into the first manifold 10 through the raw water pump 2, the raw water pipe 3, and the valve 3a. The raw water in the first manifold 10 is introduced into the reverse osmosis membrane modules 11, 12, 13 via the pipes 11a, 12a, 13a. The permeated water of the reverse osmosis membrane modules 11, 12, 13 is sent to the permeated water collecting pipe 4 through the permeated water extraction pipes 11d, 12d, 13d. The concentrated water from each module 11, 12, 13 is introduced into the second manifold 20 via the concentrated water pipes 11b, 12b, 13b and the valves 11c, 12c, 13c.

  The water in the second manifold 20 is introduced into the reverse osmosis membrane modules 21 and 22 through the pipes 21a and 22a. The permeated water of the reverse osmosis membrane modules 21 and 22 is sent to the extraction collecting pipe 4 through the permeated water extraction pipes 21d and 22d. The concentrated water from the modules 21 and 22 is introduced into the third manifold 30 through the concentrated water pipes 21b and 22b and the valves 21c and 22c.

  The water in the third manifold 30 is introduced into the reverse osmosis membrane module 31 through the pipe 31a. The permeated water of the reverse osmosis membrane module 31 is sent to the extraction collecting pipe 4 through the permeated water extraction pipe 31d. The concentrated water of the module 31 is taken out through the pipe 31b and the valve 31c. The modules 11 to 13, 21, 22, and 31 are the same.

  During the reverse osmosis treatment of the raw water, the valves 3a, 11c, 12c, 13c, 21c, 22c and 31c are opened and the valves 11f, 12f, 13f, 21f, 22f, 42, 46, 47, 51a, 52a and 53a are opened. Is closed. By operating the pump 2 in this state, the raw water is supplied with the first-stage reverse osmosis membrane modules 11 to 13 and the second-stage reverse osmosis membrane connected in three stages in series as shown by the thick solid line in FIG. The reverse osmosis membrane treatment is performed by the modules 21 and 22 and the third-stage reverse osmosis membrane module 31, and the permeated water is taken out from the pipe 4 and the concentrated water is taken out from the pipe 31b.

  Next, a water flow system for the rejection rate improver-containing water (in this embodiment, an aqueous solution) will be described.

  The aqueous solution for improving the rejection rate in the rejection rate improving agent tank 40 can be supplied to the raw water piping 3 through the piping 43 having the pump 41 and the valve 42. In addition, an aqueous solution for improving the rejection rate can be introduced into the manifold 10 from the raw water pipe 3. Further, the raw water pipe 3 can supply the blocking ratio improver aqueous solution to the manifolds 20 and 30 through the pipe 45 and the valves 46 and 47.

  Moreover, in this embodiment, the pipes 11e, 12e, and 13e branch from the concentrated water pipes 11b, 12b, and 13b from the first stage modules 11 to 13, and the pipe 51, the valve 51a, the collective pipe 53, and the valve 56a are connected. The blocking rate improver drainage from the first stage modules 11 to 13 can be drained out of the system. In addition, adjustment valves 11f, 12f, and 13f are provided in the pipes 11e, 12e, and 13e, respectively, so that the supply amount of the inhibition rate improving agent aqueous solution to each of the modules 11 to 13 can be adjusted.

  Similarly, the pipes 21e and 22e branch from the concentrated water pipes 21b and 22b from the second stage modules 21 to 23, and the second stage modules 21 and 22 are connected via the pipe 52, the valve 52a, the collective pipe 53, and the valve 56a. The rejection rate improver drainage from the plant can be drained out of the system. The piping 21e and 22e are provided with regulating valves 21f and 22f, respectively, so that the supply amount of the blocking rate improving agent aqueous solution to the modules 21 and 22 can be adjusted.

  Part of the concentrated water from each of the modules 11 to 13, 21, 22, and 31 can be returned to the raw water tank 1 through the pipes 53 and 54 and the valve 54 a.

  The flow of water flow when the reverse osmosis membrane module of each stage is subjected to a rejection improvement process is as follows.

<Flow at the time of the rejection improvement process of the first stage reverse osmosis membrane modules 11 to 13 (FIG. 2)>
The valves 3a, 42, 51a and 56a are opened, and the valves 11c, 12c, 13c, 21c, 22c, 31c, 46, 47, 53a and 54a are closed. In this state, the pump 41 is operated and the opening degree of the regulating valves 11f, 12f, and 13f is adjusted, and as shown by the thick solid line in FIG. , 12 and 13 are supplied equally. The blocking ratio improver aqueous solution that has not permeated the reverse osmosis membranes of the reverse osmosis membrane modules 11, 12, 13 is discharged out of the reverse osmosis membrane device through the pipes 11 b, 12 b, 13 b, 51, 53. Part of the aqueous solution for improving the rejection rate introduced into the modules 11, 12, 13 passes through the reverse osmosis membrane and is taken out of the reverse osmosis membrane device through the pipes 11 d, 12 d, 13 d, 4.

  In this way, the reverse osmosis membranes of the modules 11 to 13 are equally treated by passing the aqueous solution of the inhibition ratio improving agent having the same concentration evenly through the manifold 10 to the modules 11 to 13. In addition, when the rejection rate improving agent aqueous solution permeates the reverse osmosis membrane, the rejection rate improvement treatment is performed even inside the reverse osmosis membrane. The permeate taken out from the pipe 4 during the rejection improvement process may be used as permeate, returned to the raw water tank, or discarded.

<Flow at the time of the rejection improvement process of the second-stage reverse osmosis membrane modules 21 and 22 (FIG. 3)>
The valves 42, 46, 52a and 56a are opened, and the valves 3a, 11c, 12c, 13c, 21c, 22c, 31c, 47, 51a, 53a and 54a are closed. In this state, the pump 41 is operated and the opening degree of the regulating valves 21f and 22f is adjusted, and the reverse osmosis membrane modules 21 and 22 are supplied with the blocking rate improver aqueous solution via the manifold 20 as shown by the thick solid lines in FIG. Evenly. The blocking ratio improver aqueous solution that has not permeated through the reverse osmosis membranes of the reverse osmosis membrane modules 21 and 22 is discharged out of the reverse osmosis membrane device through the pipes 21b, 22b, 52, and 53. Part of the aqueous solution of the blocking rate improving agent introduced into the modules 21 and 22 passes through the reverse osmosis membrane and is taken out of the reverse osmosis membrane device through the pipes 21d, 22d and 4. In this way, the reverse osmosis membranes of the modules 21 and 22 are uniformly treated by improving the rejection rate by passing the aqueous solution of the rejection rate improving agent having the same concentration uniformly through the manifold 20 to the modules 21 and 22.

<Flow at the time of the rejection improvement process of the third-stage reverse osmosis membrane module 31 (FIG. 4)>
The valves 42, 47, 53a and 56a are opened, and the valves 3a, 21c, 22c, 31c, 46, 51a, 52a and 54a are closed. When the pump 41 is operated in this state, the aqueous solution for improving the rejection rate is supplied to the reverse osmosis membrane module 31 through the manifold 30 as shown by a thick solid line in FIG. The aqueous solution of the blocking rate improving agent that has not permeated through the reverse osmosis membrane of the reverse osmosis membrane module 31 is discharged out of the reverse osmosis membrane device through the pipe 53. A part of the aqueous solution for improving the blocking rate introduced into the module 31 passes through the reverse osmosis membrane and is taken out of the reverse osmosis membrane device through the pipes 31d and 4. Note that one third-stage reverse osmosis membrane module 31 is connected to the manifold 30, but when a plurality of third-stage reverse osmosis membrane modules are connected to the manifold 30, the manifold 30 and the regulating valve are connected. The reverse osmosis membrane of each module is uniformly treated to improve the rejection rate by passing the aqueous solution of the rejection rate improving agent having the same concentration evenly through each of the third-stage reverse osmosis membrane modules.

<Flow at the time of blocking rate improvement processing of all-stage reverse osmosis membrane modules 11, 12, 13, 21, 22, and 31 (FIG. 5)>
As described above, the module of each stage can be subjected to the rejection rate improving process for each stage, but as described below, the module of all stages can also be subjected to the rejection ratio improving process at a time.
In order to improve the rejection rate for all the modules at a time, first, the valves 3a, 42, 46, 47, 51a, 52a, 53a, 56a are opened, and the valves 11c, 12c, 13c, 21c, 22c, 31c, 54a are opened. Is closed. In this state, the pump 41 is operated and the opening degree of the regulating valves 11f, 12f, 13f, 21f, 22f and the valve 53a is adjusted, and as shown by the thick solid line in FIG. , 30 to the reverse osmosis membrane modules 11, 12, 13, 21, 22, 31. The blocking rate improver aqueous solution that did not permeate the reverse osmosis membranes of the reverse osmosis membrane modules 11, 12, 13, 21, 22, 31 passes through the pipes 11 b, 12 b, 13 b, 51, 21 b, 22 b, 52, 53. It is discharged out of the reverse osmosis membrane device. A portion of the aqueous solution for improving the rejection rate introduced into the modules 11, 12, 13, 21, 22, 31 permeates the reverse osmosis membrane, and the piping 11 d, 12 d, 13 d, 21 d, 22 d, 31 d, 4
Through the reverse osmosis membrane device. In this way, each of the modules 11, 12, 30, 30, 30, 30 is passed through each manifold 11, 12, 13, 21, 22, 31 evenly by passing the aqueous solution of the rejection improving agent having the same concentration equally. The reverse osmosis membranes 13, 21, 22, and 31 are uniformly processed to improve the rejection rate.

[Explanation of preferred examples of reverse osmosis membrane and blocking rate improver]
A reverse osmosis membrane (RO membrane) 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 solutes and permeate the solvent.

  Examples of the membrane structure of the reverse osmosis membrane include polymer membranes such as composite membranes and phase separation membranes. Examples of the material for the reverse osmosis membrane include polyamide-based materials such as aromatic polyamides, aliphatic polyamides, and composite materials thereof. Among these, the rejection improvement process according to the present invention can be suitably applied to the aromatic polyamide film. The reverse osmosis membrane to be subjected to the rejection improvement process may be an unused reverse osmosis membrane or a reverse osmosis membrane whose performance is reduced by use.

  There is no restriction | limiting in particular about the format of a reverse osmosis membrane module, For example, a tubular membrane module, a flat membrane module, a spiral membrane module, a hollow fiber membrane module etc. are applicable.

  In the case of an unused reverse osmosis membrane, the rejection rate improvement treatment may be performed as it is, but in the case of a reverse osmosis membrane whose performance has deteriorated due to use, it is necessary to perform chemical cleaning after performing chemical cleaning. preferable. By removing the contaminants on the surface of the film by chemical cleaning, the blocking rate improver is easily adsorbed on the film itself. Cleaning chemicals include acids (hydrochloric acid, nitric acid, oxalic acid, citric acid, etc.), alkalis (potassium hydroxide, sodium hydroxide, etc.), surfactants (sodium dodecyl sulfate, sodium dodecylbenzene sulfate, etc.), oxidizing / reducing agents ( Hydrogen peroxide, percarbonate, peracetic acid, sodium bisulfite, etc.) are used. The membrane can be washed by passing an aqueous solution of these chemicals through the module or immersing the reverse osmosis membrane in the chemical.

  Preferable blocking rate improvers include compounds having a polyalkylene glycol chain, polyphenols such as tannic acid, particularly compounds having a polyalkylene glycol chain. The weight average molecular weight of the blocking rate improver such as a compound having a polyalkylene glycol chain is preferably 1,000 to 10,000, more preferably 2,000 to 6,000, and still more preferably 3,000 to 5,000. It is. If the weight average molecular weight of the rejection rate improving agent is too small, the rejection rate of the reverse osmosis membrane is not sufficiently improved, and the fixability of the rejection rate improving agent after processing may be lowered. If the weight average molecular weight of the blocking rate improver is too large, the permeation flux of the reverse osmosis membrane after treatment may be lowered.

  The weight average molecular weight can be determined by analyzing an aqueous solution of the compound of the blocking rate improver 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.

  Examples of the polyalkylene glycol chain include a polyethylene glycol chain, a polypropylene glycol chain, a polytrimethylene glycol chain, and a polytetramethylene glycol chain. These glycol chains can be formed by, for example, ring-opening polymerization of ethylene oxide, propylene oxide, oxetane, tetrahydrofuran or the like.

  Examples of the compound having a polyalkylene glycol chain include polyethylene glycol, polypropylene glycol, polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene sorbitan monolaurate, etc. is not. Examples of this alkyl include methyl, ethyl, propyl and the like. These compounds having a polyalkylene glycol chain may be used alone or in combination of two or more. Moreover, it may mix and use as one liquid, and may prepare and use each separately. From a practical viewpoint, it is preferable to use one liquid.

  The concentration of the aqueous solution for improving the blocking rate supplied from the blocking rate improver tank 40 to each manifold 10, 20 or 30 is preferably about 0.01 to 50 mg / L. The more preferable concentration of the aqueous solution for increasing the rejection rate varies depending on the type of the rejection rate improving agent used. For example, in the case of the compound having a polyalkylene glycol chain having a weight average molecular weight of 1000 to 10000, 0.01 to 20 mg / L is used. preferable. If the concentration is lower than this, it may take a long time to improve the rejection rate. When the concentration exceeds 50 mg / L, the viscosity of the aqueous solution increases, and there is a possibility that the water resistance to the reverse osmosis membrane increases. On the other hand, if the concentration exceeds 50 mg / L, an unnecessarily thick adsorption layer is formed on the surface of the reverse osmosis membrane, and the effect of improving the rejection rate may be weakened due to concentration polarization.

  Only one type of blocking rate improver may be used, or a plurality of blocking rate improvers may be used in combination. In the latter case, the liquids may be mixed and passed, or the liquids may be passed separately at different times.

  The time per one time that the aqueous solution of the blocking rate improving agent is passed through the reverse osmosis membrane module in one stage is preferably about 0.1 to 50 hours, particularly 0.2 to 24 hours, especially 30 minutes to 10 hours.

  In addition, you may make the rejection rate improving agent aqueous solution contain the rejection rate confirmation tracer which consists of an inorganic electrolyte or a water-soluble organic compound. By passing the aqueous solution containing the tracer-containing blocking rate improver through the reverse osmosis membrane module and detecting the tracer concentration in the permeated water, the blocking rate of the reverse osmosis membrane is confirmed over time, and the blocking rate improvement process is continued. Or a stop can be judged. For example, when the tracer concentration of the permeated water reaches a predetermined value, it is determined that the rejection rate of the reverse osmosis membrane has been increased to a predetermined value, and the rejection rate improving process is terminated. According to this method, the contact time (water passage time) between the aqueous solution for improving the rejection rate and the reverse osmosis membrane can be made to the minimum necessary length. 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, sodium nitrate, and boric acid. Examples of the water-soluble organic compound used as the tracer include isopropyl alcohol, glucose, urea and the like, and isopropyl alcohol is preferable because it is easy to handle. The concentration of the tracer is preferably about 1 to 500 mg / L, particularly about 10 to 100 mg / L in the case of an inorganic strong electrolyte such as sodium chloride. In the case of an inorganic weak electrolyte such as boric acid or a water-soluble organic substance such as isopropyl alcohol, the amount is preferably about 1 to 5000 mg / L, particularly about 5 to 1000 mg / L.

  In the embodiment described above, the rejection rate improver aqueous solution in the rejection rate improver tank 40 is supplied to the manifold 10, 20 or 30, but the suction side of the pump 2 and the piping 3 are supplied to the raw water from the raw water tank 1. In FIG. 2, a rejection rate improver is added to form a rejection rate improver aqueous solution, and this rejection rate improver aqueous solution is supplied from the pipe 3 to the manifold 10, 20 or 30 according to the flow of FIG. 2, FIG. 3 or FIG. Also good. Alternatively, a blocking rate improver aqueous solution may be prepared by pumping water from a water tank storing reverse osmosis membrane permeated water or pure water and adding a blocking rate improver thereto.

  Examples will be described below, but the present invention is not particularly limited thereto.

[Example 1]
Nine reverse osmosis membrane modules are connected to the first stage manifold 10, five reverse osmosis membrane modules are connected to the second stage manifold 20, and two reverse osmosis membrane modules are connected to the third stage manifold 30. In the reverse osmosis membrane apparatus configured in the same manner as in FIG. 1 except that it was configured as described above, the reverse osmosis membrane rejection rate improving process was performed according to the method of the present invention. Each reverse osmosis membrane module is one in which four new membrane modules of Nitto Denko's 8-inch ultra-low pressure aromatic polyamide RO membrane ES20 are loaded in one pressure vessel.

In accordance with the method shown in FIG. 5, the regulating valves 11f, 12f are adjusted so that the water supply pressure to the manifolds 10, 20, 30 at each stage is 0.6 MPa and the water supply amount per reverse osmosis membrane module is 5 m ³ / h. , 13f, 21f, 22f and the opening of the valve 53a were adjusted, and the rejection rate improver aqueous solution in the rejection rate improver tank 40 was passed through the reverse osmosis membrane module. A 20 mg / L aqueous solution of polyethylene glycol having a weight average molecular weight of 3000 was used as the blocking rate improver. After passing through each reverse osmosis membrane module for 2 hours, brushing was performed with pure water to finish the treatment.

The reverse osmosis membrane after the treatment was extracted, and the IPA (isopropyl alcohol) removal rate and flux were measured. The results are shown in Table 1. In addition, IPA removal rate measures IPA of concentrated water, permeated water, and raw water with a TOC meter,
Removal rate = [1- (permeated water TOC)] / [{(raw water TOC) + (concentrated water TOC)} / 2]
It calculated in. The flux (permeated water amount) was calculated in terms of 0.74 MPa and 25 ° C.

[Comparative Example 1]
In the first embodiment, the manifold 10 is supplied with an aqueous solution of the same rejection rate as that of the first embodiment when the water supply pressure is 0.6 MPa and the water supply amount per first-stage module is 5 m ³ / h. The water was supplied so as to be supplied to 20 and 30, and the rejection improvement process was performed for 2 hours, flushing with pure water was performed, and the process was completed. The performance of the element after treatment was measured in the same manner as in Example 1, and is shown in Table 1.

  As shown in Table 1, it was confirmed that the difference in performance between the reverse osmosis membrane extracted from the first stage and the reverse osmosis membrane extracted from the third stage was smaller in Example 1.

DESCRIPTION OF SYMBOLS 1 Raw water tank 10, 20, 30 Manifold 11, 12, 13, 21, 22, 31 Reverse osmosis membrane module 40 Blocking rate improver tank

Claims (3)

In a method for improving the rejection rate of a reverse osmosis membrane module of a reverse osmosis membrane device in which reverse osmosis membrane modules are arranged in multiple stages and at least in some stages, the reverse osmosis membrane modules are installed in parallel.
In the stage where the reverse osmosis membrane device is installed in parallel, a manifold is provided on the inflow side of the treated water of the stage, and the treated water is introduced from the manifold to each reverse osmosis membrane module. Configure
A rejection rate improver is supplied to the manifold, and water containing the rejection rate improver is introduced from the manifold into the reverse osmosis membrane module, thereby improving the rejection rate of the reverse osmosis membrane of the reverse osmosis membrane module. A reverse osmosis membrane treatment method.   The reverse osmosis membrane according to claim 1, wherein the water containing the blocking rate improving agent that has passed through the reverse osmosis membrane module is discharged out of the reverse osmosis membrane device without passing through the reverse osmosis membrane module in the next stage. Processing method. In a reverse osmosis membrane device in which reverse osmosis membrane modules are arranged in multiple stages, and at least some of the stages are equipped with reverse osmosis membrane modules in parallel,
In the stage where the reverse osmosis membrane modules are installed in parallel, a manifold is provided on the inflow side of the treated water of the stage, and the treated water is introduced from the manifold to each reverse osmosis membrane module,
A reverse osmosis membrane device comprising means for adding a blocking rate improver to the manifold so as to achieve a target concentration.

Images