JP2015097990A - Rejection enhancing method of reverse osmosis membrane, reverse osmosis membrane and water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to obtain a high rejection enhancing effect by effectively cleaning an RO membrane with heavy organic contamination before a rejection enhancing treatment of the contaminated membrane when performing the rejection enhancing treatment.SOLUTION: In a rejection enhancing method of a reverse osmosis membrane, the RO membrane is brought into contact with a cleaning fluid comprising an alkaline solution having a pH value of 10 or higher and containing hypochlorous acid and/or hypochlorite or a chloramine compound before performing a rejection enhancing treatment by contacting the RO membrane with a rejection enhancing agent and is cleaned. Organic matter adhered to the RO membrane can be efficiently removed by cleaning the RO membrane using the alkaline solution having a pH value of 10 or higher and containing hypochlorous acid and/or hypochlorite or the chloramine compound before performing the rejection enhancing treatment. In the subsequent rejection enhancing treatment, the rejection rate of the RO membrane is effectively enhanced by a repair effect due to the adsorption of a rejection enhancing component.

Description

  The present invention is a reverse osmosis membrane (RO membrane), particularly an aromatic polyamide-based RO membrane, which is high without significantly lowering the permeation flux, particularly against an RO membrane having a reduced rejection rate in the course of its use. The present invention relates to a rejection rate improving method capable of obtaining a rejection rate improving effect, an RO membrane treated by the rejection rate improving method, and a water treatment method using the RO membrane.

Currently, desalination of seawater and brackish water and water recovery are performed using RO membrane systems in order to make up for the shortage of water supply worldwide. In the RO membrane system, in order to suppress biofouling, oxidizers such as chlorine (sodium hypochlorite) and hydrogen peroxide are added to the raw water (RO membrane treated water) in the pretreatment process. ing.
However, since these oxidants have a strong oxidative decomposition action, if these oxidants are added and the raw water is supplied to the RO membrane with insufficient reduction treatment, the RO membrane will deteriorate. It has been known.
In addition, in order to decompose the oxidizing agent in the raw water, a reducing agent such as sodium bisulfite is often added to the raw water and supplied to the RO membrane, but in a reducing environment where sodium bisulfite is excessively added. It is also known that when metals such as Cu and Co coexist in the raw water, the RO membrane deteriorates and the rejection rate decreases (Patent Document 1, Non-Patent Document 1).

The present inventors proposed the following method as a method for obtaining a high rejection rate improvement effect without greatly reducing the permeation flux of the RO membrane, and filed a patent application earlier than the present applicant.
Patent Document 2: Method of passing an aqueous solution containing a compound having a polyalkylene glycol chain having a weight average molecular weight of 2,000 to 6,000 through an RO membrane Patent Document 3: Hydrophilicity having no hydrophobic group having 8 or more carbon atoms And a water-soluble polymer having a hydrophobic group having 8 or more carbon atoms in contact with a permeable membrane Patent Document 4: a first organic compound having a molecular weight of less than 200 and a first organic compound having a molecular weight of from 200 to less than 500 A method of passing an aqueous solution containing an organic compound of No. 2 and a third organic compound having a molecular weight of 500 or more through an RO membrane Patent Documents 5 and 6: Passing an aqueous solution containing a compound having an amino group and a molecular weight of 1000 or less through the RO membrane How to water

  All of these methods for improving the rejection rate are RO membranes by a mechanism in which a part or all of the effective component of the rejection rate improver (a rejection rate improving component) is adsorbed on the membrane to repair the deteriorated portion of the membrane surface. This improves the rejection rate.

On the other hand, as a method for cleaning RO membranes contaminated with organic substances by use in pure water production, wastewater recovery, etc., it is common to perform alkaline cleaning at pH 10 or higher, preferably pH 12 or higher. And a method of using it together with a chelating agent is also employed (Non-patent Document 2).
In addition, when the contamination is severe, it has been reported that the cleaning effect is improved by performing cleaning in the order of alkali cleaning, acid cleaning, and alkali cleaning (Patent Document 7).

JP-A-7-308671 JP 2007-289922 A JP 2009-022886 JP 2012-187469 A JP 2012-187468 A International Publication WO2011 / 040354 Japanese Patent No. 4631287

M.M. Nagai et al. , Desalination, Vol. 96 (1994), 291-301 "Membrane degradation and fouling countermeasures: From membrane contamination prevention and cleaning methods to troubleshooting" (NTS issue) p142 2008

  Although the blocking rate improvement method proposed in Patent Documents 2 to 5 can effectively improve the blocking rate of the RO membrane, the RO membrane deteriorated by use in pure water production or wastewater recovery is contaminated with organic matter. In many cases, when the blocking rate improvement process is performed with insufficient cleaning, the desired blocking rate improvement effect cannot be obtained. This is because the organic matter, which is a pollutant that has already adsorbed, eliminates the blocking rate improving component that should be adsorbed on the deteriorated portion of the film surface, so that the effect of repairing the film by adsorption of the blocking rate improving component cannot be obtained. it is conceivable that.

  For this reason, it is conceivable to perform the RO membrane cleaning process prior to the rejection rate improving process in the RO rate rate improving process of the RO membrane contaminated with organic matter as described above. In addition, there is a case where a sufficient cleaning effect cannot be obtained even if the cleaning is performed mainly by the alkali cleaning proposed in Patent Document 6 and the subsequent inhibition rate improving process becomes insufficient.

  The present invention provides a method for solving the above-described problems and obtaining a high effect of improving the rejection rate by effectively cleaning the contaminated membrane prior to the improvement rate of the rejection rate in the processing of improving the rejection rate of the RO membrane that is heavily contaminated with organic matter. The task is to do.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that an alkaline solution having a pH of 10 or more containing hypochlorous acid and / or hypochlorite or a chloramine compound prior to the treatment for improving the rejection rate. By cleaning the RO membrane with the use of organic substances, organic substances adhering to the RO membrane can be efficiently removed, and in the subsequent rejection rate improving process, the RO membrane can be repaired by the adsorption effect of the rejection rate improving component. It has been found that the rejection rate can be effectively improved.

  The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] In the reverse osmosis membrane blocking rate improving method of contacting a reverse osmosis membrane with a blocking rate improver, prior to the contact of the reverse osmosis membrane with the blocking rate improver, hypochlorous acid and A method for improving the inhibition rate of a reverse osmosis membrane, comprising contacting a cleaning solution comprising an alkaline solution having a pH of 10 or more, comprising / or a hypochlorite or a chloramine compound.

[2] In [1], the cleaning liquid is prepared by diluting and mixing an aqueous solution of hypochlorous acid and / or hypochlorite (hereinafter referred to as “hypochlorous acid (salt)”) with an alkaline agent and water. An aqueous solution of hypochlorous acid (salt) prepared as described above, wherein the hypochlorous acid (salt) is obtained by calculation based on the effective chlorine concentration and dilution ratio of the hypochlorous acid (salt) aqueous solution before dilution. A method for improving the rejection of a reverse osmosis membrane, wherein the effective chlorine concentration of the alkaline aqueous solution is 10 mg / L or less.

[3] The method for improving the rejection of a reverse osmosis membrane according to [1], wherein the cleaning liquid is an aqueous solution containing a chloramine compound and an alkaline agent.

[4] The reverse osmosis membrane according to any one of [1] to [3], wherein the blocking rate improver is any one or more of the following (1) to (4): How to improve rejection rate.
(1) An aqueous solution containing a compound having a polyalkylene glycol chain having a weight average molecular weight of 2,000 to 6,000 (2) A first organic compound having a molecular weight of less than 200, and a second organic compound having a molecular weight of 200 or more and less than 500 An aqueous solution containing a third organic compound having a molecular weight of 500 or more (3) An aqueous solution containing one or more selected from the group consisting of polyphenols, modified polyvinyl alcohols, polymeric polysaccharides and polyamino acids, or polyphenols An aqueous solution containing an aqueous solution containing one or more selected from the group consisting of a modified polyvinyl alcohol, a polymeric polysaccharide and a polyamino acid (4) An aqueous solution containing a compound having an amino group and a molecular weight of 1000 or less

[5] A reverse osmosis membrane treated by the inhibition rate improving method according to any one of [1] to [4].

[6] A water treatment method using the reverse osmosis membrane according to [5].

  According to the present invention, in the RO membrane rejection rate improving treatment, the RO membrane is washed with an alkaline solution having a pH of 10 or more, which previously contains hypochlorous acid and / or hypochlorite, or a chloramine compound. Even if the RO membrane is heavily contaminated with organic matter, the organic matter adhering to the RO membrane can be oxidized and peeled off for efficient cleaning and removal. For this reason, in the subsequent rejection rate improvement process, the rejection rate improving component can be brought into direct contact with the deteriorated portion of the membrane, and the original repair effect due to adsorption of the rejection rate improving component can be sufficiently obtained. The rejection rate can be improved effectively.

It is a systematic diagram which shows the RO membrane test apparatus used in the Example.

  Hereinafter, embodiments of the present invention will be described in detail.

  In the present invention, prior to the RO membrane rejection rate improving treatment, the RO membrane is treated with hypochlorous acid and / or hypochlorite (hereinafter referred to as hypochlorous acid and / or hypochlorite). Washed by contacting with an alkaline solution having a pH of 10 or higher containing chloric acid (salt)) or a chloramine compound.

Although hypochlorous acid (salt) has a high effect as an oxidizing agent for decomposing organic substances, it has a strong oxidizing power, so that the aromatic polyamide-based material that has become the mainstream in recent years as an RO membrane material is also oxidatively deteriorated. , Causing a decrease in the rejection rate. For this reason, as described above, conventionally, reduction treatment is performed with a reducing agent such as sodium bisulfite so that there is no oxidizing power at the stage of the water to be treated in the RO membrane. The chloramine compound produced by reacting a compound having a primary amine with hypochlorous acid (salt) can reduce free chlorine and suppress the deterioration of the RO membrane. There are cases where a method of existing is taken. However, chloramine compounds are generally used to suppress biofouling by being present in the water to be treated.
In the present invention, hypochlorous acid (salt) is used under alkaline conditions of pH 10 or higher for cleaning the RO membrane. By doing so, it is possible to reduce the existence ratio of HClO, which is said to have strong oxidizing power, to the limit, and it is possible to obtain an oxidation effect and an organic substance peeling effect due to alkaline conditions. Moreover, the chloramine compound can also be used as a cleaning agent having high oxidizing power and high peeling effect by using it under alkaline conditions for the same reason.

[Cleaning liquid and cleaning method]
First, a cleaning liquid composed of an alkaline solution having a pH of 10 or more containing hypochlorous acid (salt) or a chloramine compound used in the present invention and a cleaning method thereof will be described.

Specifically, the cleaning liquid used in the present invention is preferably the following (i) or (ii).
(i) An alkaline aqueous solution of hypochlorous acid (salt) prepared by diluting and mixing an aqueous solution of hypochlorous acid (salt) with an alkaline agent and water, and the hypochlorous acid (salt) aqueous solution before dilution The effective chlorine concentration of the alkaline aqueous solution of hypochlorous acid (salt) obtained by calculation based on the effective chlorine concentration and dilution ratio of the aqueous solution is 10 mg / L or less (hereinafter referred to as “cleaning liquid (i)”).
(ii) An aqueous solution containing a chloramine compound and an alkali agent (hereinafter referred to as “cleaning liquid (ii)”)

<Cleaning liquid (i) and cleaning method thereof>
Hypochlorous acid (salt), for example hypochlorous acid, used as a cleaning agent component in the cleaning liquid (i) is considered to generate chemical reaction species as shown in the following formulas (a) to (f). (Tadahiro Uemura, Yu Kurihara (Toray), Journal of the Seawater Society of Japan, Vol. 57, 498-507 (2003)).
HOCl + HCl⇔H ₂ O + Cl ₂ ⇔H ₂ O + 2Cl ^· (a)
HOCl + H ⁺ ⇔H ₂ O + Cl ⁺ (b)
HOCl⇔OH ⁻ + Cl ⁺ (c)
_{^{HOCl + OH - ⇔H 2 O +}} OCl - (d)
HOCl⇔Cl ^· + OH ^· (e)
HOCl⇔HCl + O (f)

Among the above reactions, the reactions of formulas (a) to (c) proceed under acidic conditions, and the reaction of formula (d) is considered to proceed under alkaline conditions. Thus, in alkaline conditions, is a potent reactive species ^Cl ·, Cl ^+, and the generation of OH ^· is suppressed, there forms in water Hypochlorous acid (HOCl), in pH10 or more, most OCl ^- and Become.
In the present invention, paying attention to this point, it is possible to apply hypochlorous acid (salt) to the RO membrane cleaning under alkaline conditions. Adds sterilization and organic matter decomposition action with chlorous acid (salt) to enhance the alkaline cleaning effect and effectively restore the performance of the contaminated RO membrane.

Hypochlorous acid (salt) is usually provided as an aqueous solution having an effective chlorine (Cl ₂ ) concentration of about 0.25 to 12% by weight. In the present invention, an alkaline agent is added to such an aqueous solution of hypochlorous acid (salt), and diluted with water for use.
As hypochlorite, alkali metal salts of hypochlorous acid such as sodium hypochlorite, alkaline earth metal salts of hypochlorous acid such as calcium hypochlorite, and the like can be used.
Hypochlorous acid (salt) may be used individually by 1 type, and 2 or more types may be mixed and used for it.
In the present invention, the effective chlorine concentration is measured as free chlorine by the OPD method defined in JIS K0400-33-10;

  As the alkaline agent used for adjusting the pH of the cleaning liquid (i), sodium hydroxide, potassium hydroxide and the like can be used. These may be used alone or in combination of two or more.

  The cleaning liquid (i) prepared by adding an alkaline agent and water to the above-mentioned hypochlorous acid (salt) aqueous solution must have a pH of 10 or more. If the pH of the cleaning liquid (i) is less than 10, a sufficient cleaning effect cannot be obtained. In particular, when the pH is on the acidic side, the reactions of the above formulas (a) to (c) occur, which is not preferable. The higher the pH of the cleaning solution (i) is, the better the cleaning effect is. However, if the cleaning solution (i) is too high, the handling property as the cleaning solution deteriorates and RO membrane deterioration due to alkali occurs. 13.

  In addition, the cleaning solution (i) is an effective chlorine concentration obtained by calculation based on the effective chlorine concentration of the hypochlorous acid (salt) aqueous solution before dilution and the dilution factor (hereinafter, sometimes referred to as “theoretical effective chlorine concentration”). Is required to be 30 mg / L or less. If the theoretical effective chlorine concentration of the cleaning liquid (i) is higher than 30 mg / L, the RO membrane may be deteriorated, and the desalination rate of the RO membrane may be reduced by cleaning. The theoretical effective chlorine concentration of the cleaning liquid (i) is preferably lower from the viewpoint of preventing the deterioration of the RO membrane, and higher from the viewpoint of the cleaning effect. The theoretical effective chlorine concentration of the cleaning liquid (i) is particularly preferably 0.1 to 10 mg / L, and particularly preferably 1 to 10 mg / L.

  Therefore, in the present invention, an alkaline agent and water are added to and mixed with a hypochlorous acid (salt) aqueous solution so that the pH and the theoretical effective chlorine concentration are obtained and used as the cleaning liquid (i).

Other cleaning liquid components may be added to the cleaning liquid (i) as long as the cleaning effect is not impaired.
For example, in order to enhance the peeling effect of membrane contaminants, chelating agents such as EDTA (ethylenediaminetetraacetic acid), EGTA (ethyleneglycolbis (aminoethylether) tetraacetic acid), IDA (iminodiacetic acid), sodium lauryl sulfate, One or more surfactants such as sodium dodecylbenzene sulfate may be added.

  Further, before or after the RO membrane cleaning with the cleaning liquid (i), the RO membrane cleaning with another cleaning liquid may be performed, and the cleaning effect can be further enhanced by combining the RO membrane cleaning with another cleaning liquid.

  For example, before the cleaning with the cleaning liquid (i) or after the cleaning with the cleaning liquid (i), cleaning with an alkaline aqueous solution containing no hypochlorous acid (salt) may be performed. As the alkali agent of the alkaline aqueous solution, those described above as the alkali agent of the cleaning liquid (i) can be used, and the pH thereof is preferably pH 10 or more, particularly pH 12 to 13 in terms of the cleaning effect and handleability. preferable.

  Further, acid cleaning effective for removing scales and metal colloids may be performed. For the acid cleaning, an aqueous solution containing one or more acids such as hydrochloric acid, nitric acid, citric acid, and oxalic acid is used. it can. The pH of the acid aqueous solution is preferably pH 4 or less, particularly preferably pH 1 to 3, in terms of cleaning effect and handleability.

  The RO membrane can be cleaned using the cleaning solution (i) as long as the RO membrane is brought into contact with the cleaning solution (i). Although there is no particular limitation, the cleaning solution (i) is usually placed on the raw water side of the RO membrane module. Soaking is performed by introducing and allowing to stand. In this immersion cleaning, the pH of the cleaning liquid (i) in contact with the RO membrane is 10 or more, preferably 12 to 13, and the theoretical effective chlorine concentration is 10 mg / L or less, preferably 1 to 10 mg / L. This is very important.

  Also, when washing is performed using the above-described alkaline aqueous solution or acid aqueous solution before and after washing with the washing liquid (i), the same immersion washing as described above is usually employed.

  The immersion cleaning time with the cleaning liquid (i) and other cleaning liquids is not particularly limited as long as the recovery rate of the target film performance can be obtained, but is usually about 2 to 24 hours.

In the case where the cleaning with the cleaning liquid (i) is combined with the cleaning with the alkaline aqueous solution and / or the aqueous acid solution, the cleaning procedure is not particularly limited, but the acid cleaning with the aqueous acid solution is performed before the cleaning with the cleaning solution (i). By performing, it is possible to reduce and remove metals that may cause a catalytic effect on chlorine. Further, the alkali cleaning with the alkaline aqueous solution may be performed before or after the cleaning with the cleaning liquid (i).
However, when cleaning with a cleaning solution (i) or a combination of three aqueous solutions, an alkaline aqueous solution and an acid aqueous solution, cleaning is performed using an alkaline aqueous solution, followed by cleaning with an aqueous acid solution, and then using the cleaning solution (i). It is preferable to wash it. This removes organic matter adhering to the film surface by washing with an alkaline aqueous solution, improves the peeling effect of metallic deposits in subsequent acid washing, and chlorine and metal in washing with the washing liquid (i) This is because it is possible to effectively reduce the risk of film deterioration due to the catalytic effect.

  After cleaning with the above-described cleaning liquid or the like, usually, high-purity water such as pure water is passed to perform final cleaning, and the process proceeds to the next inhibition rate improving process.

<Cleaning liquid (ii) and cleaning method thereof>
A chloramine compound, for example, an amino acid obtained by reacting hypochlorous acid (HOCl) with a compound having a primary amino group (XNH ₂ ) in a reaction as shown in the following reaction formulas (g) and (h) If the hydrogen atom of the group is substituted with a chlorine atom (XNHCl), the oxidation action on the RO membrane is suppressed, so even an aromatic polyamide RO membrane with low chlorine resistance can be used for cleaning. Become.
XNH ₂ + HOCl⇔XNHCl + H ₂ O (g)
XNH ₂ + OCl ⁻ ⇔XNHCl + OH ⁻ (h)

  The cleaning solution (ii) can be applied to the cleaning of the RO membrane of the chlorine-based cleaning solution under alkaline conditions by the above reaction, and is sterilized by the chloramine compound for the organic substance peeling action and hydrolysis action by the alkaline condition washing. In addition, the organic substance decomposing action is added to enhance the alkali cleaning effect and effectively restore the performance of the contaminated RO membrane.

The chloramine compound contained in the cleaning liquid (ii) is either a compound having a primary amino group, ammonia, or an ammonium salt (hereinafter, these may be referred to as “compounds having a primary amino group”). In this case, the compound having a primary amino group includes an aliphatic amine, aromatic amine, sulfamic acid, sulfanilic acid, sulfamoylbenzoic acid. And amino acids. Examples of ammonium salts include ammonium chloride and ammonium sulfate. These may be used alone or in combination of two or more. Among these compounds having a primary amino group, sulfamic acid (NH ₂ SO ₂ OH) is a stable chloramine compound when it is used to produce monochlororosulfamine, and since it does not contain carbon, it is a TOC of a cleaning agent. It is preferable to use it together with an alkaline agent without increasing the value because it becomes a very effective cleaning solution.

  On the other hand, hypochlorite to be reacted with a compound having a primary amino group includes alkali metal salts of hypochlorous acid such as sodium hypochlorite and alkalis of hypochlorous acid such as calcium hypochlorite. An earth metal salt or the like can be used. These may be used alone or in combination of two or more.

When a compound having a primary amino group and hypochlorous acid (salt) are mixed to produce a chloramine compound, the compound having a primary amino group and hypochlorous acid (salt) are hypochlorous acid. It is possible to use chloramine so that the molar ratio Cl ₂ / N molar ratio between the effective chlorine Cl ₂ derived from (salt) and the carbon atom N derived from a compound having a primary amino group is 0.1-1 It is preferable in terms of production efficiency and stability. If the Cl ₂ / N molar ratio is larger than the above upper limit, free chlorine may be produced. If the Cl ₂ / N molar ratio is smaller than the above lower limit, the production efficiency of chloramine is reduced with respect to the compound having a primary amino group used.
In this case, the amount of hypochlorous acid (salt) is the amount of chloramine compound in the cleaning liquid (ii).

  As the alkaline agent, it is possible to maintain solubility when the cleaning liquid (ii) is used, and alkali metal hydroxides such as sodium hydroxide and potassium hydroxide can be used. These may be used alone or in combination of two or more.

  The cleaning liquid (ii) must have a pH of 10 or more. If the pH of the cleaning liquid (ii) is less than 10, a sufficient cleaning effect cannot be obtained. The higher the pH of the cleaning solution (ii) is, the better the cleaning effect is.However, if the pH is too high, the handling property as the cleaning solution is deteriorated and the risk of deterioration of the RO membrane is increased, so the pH of the cleaning solution (ii) is preferable. Is 12 or more and less than 13.

Further, the concentration of the chloramine compound in the cleaning liquid (ii) is preferably 0.001 to 0.5M, and particularly preferably 0.01 to 0.2M. If the concentration of the chloramine compound in the cleaning liquid (ii) is too low, a sufficient cleaning effect cannot be obtained, and if it is too high, the RO membrane may be deteriorated. The chloramine compound concentration of 0.001 to 0.5 M is a concentration corresponding to a total chlorine concentration of 71 to 35500 mg-Cl ₂ / L. The total chlorine concentration can be measured by the OPD method defined in JIS K0400-33-10.1999.

Chloramine compounds are conventionally used as a slime control agent for permeable membranes. When a chloramine compound is used as a slime control agent, it is usually used at a low concentration of about 1 to 50 mg-Cl ₂ / L as a total chlorine concentration. . Moreover, although the pH at that time is less than 10, in the cleaning liquid (ii), a high cleaning effect is obtained by using the chloramine compound at a high concentration as described above and using an alkaline cleaning liquid having a pH of 10 or more.

The cleaning liquid (ii) is a cleaning liquid (ii) having a pH and a chloramine compound concentration as described above by diluting a cleaning agent containing a chloramine compound (hereinafter referred to as “cleaning agent (ii)”) with water (preferably pure water). It may be prepared.
In order to prepare the cleaning liquid (ii) having the above-described pH and chloramine compound concentration by diluting with water (preferably pure water), the cleaning agent (ii) has a pH of 13 or more containing a chloramine compound and an alkaline agent. Preferably, the aqueous solution has a pH of 13 to 15, a chloramine compound concentration of 0.2 to 2M, particularly 1 to 2M, and an alkaline agent concentration of 1 to 3M.

Hereinafter, a method for producing the cleaning agent (ii) will be described.
The cleaning agent (ii) is prepared by, for example, adding a compound having a primary amino group such as sulfamic acid to the aqueous solution of the alkali agent described above and dissolving it, and the resulting compound having the primary amino group and the alkali agent mixed aqueous solution. In addition, hypochlorous acid (salt) can be added and mixed. The aqueous solution of the alkali agent preferably has a water content of 50 to 90% by weight.

  In addition, the compound having a primary amino group such as sulfamic acid may be added in the form of a salt. In this case, usable salts include those which are soluble when an aqueous chloramine compound-containing solution is used. Sodium sulfamate, potassium sulfamate, ammonium sulfamate and the like can be used. The compound having a primary amino group is added so that the concentration of the chloramine compound in the cleaning agent (ii) is the above concentration. The addition amount of the compound having a primary amino group is such that the content ratio between the alkali agent and the compound having a primary amino group is 0.5 to 0.7 in terms of N / alkali metal (molar ratio). preferable. The compound having a primary amino group can be added in a powder state or in an aqueous solution state. When using a sulfamate as a compound having a primary amino group, the amount of alkali metal contained in the sulfamate is added as an alkali. When an aqueous solution is used, the amount of water contained in the aqueous solution is added as the amount of water in the alkaline aqueous solution.

On the other hand, hypochlorous acid (salt) is preferably added as an aqueous solution having an effective chlorine (Cl ₂ ) concentration of 5 to 20 wt%, preferably 10 to 15 wt%. The amount of hypochlorous acid (salt) added is such that the chloramine compound concentration in the detergent (ii) is the above concentration, and the compound containing a primary amino group and hypochlorous acid (salt) are included. The ratio is added so as to be the above-mentioned Cl ₂ / N molar ratio. As a result, there is no generation of foaming or chlorine odor, and it is possible to efficiently produce the cleaning agent (ii) comprising an aqueous solution preparation excellent in reactivity, stability, handleability, chlorine-free odor and the like. Even in this case, it is preferable to gradually add and mix hypochlorous acid (salt).

  The washing liquid (ii) is produced by diluting the thus produced washing agent (ii) with water, preferably pure water, at a pH of 10 or more so as to have the above-mentioned suitable chloramine compound concentration. However, the cleaning liquid (ii) can also be produced directly by the same method as above without going through the cleaning agent (ii).

To the cleaning liquid (ii), other cleaning component may be added as long as the cleaning effect is not impaired.
For example, in order to enhance the peeling effect of membrane contaminants, chelating agents such as EDTA (ethylenediaminetetraacetic acid), EGTA (ethyleneglycolbis (aminoethylether) tetraacetic acid), IDA (iminodiacetic acid), sodium lauryl sulfate, One or more surfactants such as sodium dodecylbenzene sulfate may be added.

In addition, when a polyol compound having a molecular weight of 1000 or less, preferably 60 to 1000 is used in combination, the cleaning effect can be further enhanced by the action of penetration into the RO membrane and dissolution of contaminants. Here, if the molecular weight of the polyol compound exceeds 1000, there is a possibility of contributing to RO membrane contamination. As the polyol compound having a molecular weight of 1000 or less, for example, ethylene glycol, propylene glycol, polyethylene glycol (degree of polymerization 2 to 22) and the like can be used. These polyol compounds may be used individually by 1 type, and 2 or more types may be mixed and used for them.
Such a polyol compound may be added to the cleaning liquid (ii) of the present invention, or may be used by adding to the following alkaline aqueous solution or acid aqueous solution.

  Further, before and after the cleaning of the RO membrane with the cleaning solution (ii), membrane cleaning with another cleaning solution may be performed, and the cleaning effect can be further enhanced by combining membrane cleaning with another cleaning solution.

  For example, washing with an alkaline aqueous solution not containing a chloramine compound can be performed prior to washing with the washing liquid (ii) or after washing with the washing liquid (ii). As the alkaline agent in this alkaline aqueous solution, those described above as the alkaline agent of the cleaning liquid (ii) can be used, and the pH thereof is pH 10 or more, particularly pH 12 to 13, in terms of the cleaning effect and handling properties. preferable.

  Further, acid cleaning effective for removing scales and metal colloids may be performed. For the acid cleaning, an aqueous solution containing one or more acids such as hydrochloric acid, nitric acid, citric acid, and oxalic acid is used. it can. The pH of the acid aqueous solution is preferably pH 4 or less, particularly preferably pH 1 to 3, in terms of cleaning effect and handleability.

  The RO membrane can be cleaned using the cleaning solution (ii) as long as the RO membrane is brought into contact with the cleaning solution (ii). Although there is no particular limitation, the cleaning solution (ii) is usually applied to the raw water side of the RO membrane module. Immersion cleaning is performed by introducing and allowing to stand. In this immersion cleaning, the pH of the cleaning liquid (ii) in contact with the RO membrane is 10 or more, preferably 12 to 13, and the chloramine compound concentration is 0.001 to 0.5M, particularly 0.01 to 0.2M. It is important that

  Also, when washing is performed using the above-described alkaline aqueous solution or acid aqueous solution before and after washing with the washing liquid (ii), the same immersion washing as described above is usually employed.

  The immersion cleaning time with the cleaning liquid (ii) and other cleaning liquids is not particularly limited as long as the recovery rate of the target film performance can be obtained, but is usually about 2 to 24 hours.

  When washing with a cleaning solution (ii) is combined with washing with an alkaline aqueous solution and / or an acid aqueous solution, the washing procedure is not particularly limited, but acid washing with an acid aqueous solution is performed before washing with a washing solution (ii). When it does, the metal which may cause a catalytic effect with respect to chlorine can be reduced and removed. In addition, the alkaline cleaning with the alkaline aqueous solution may be performed before or after the cleaning with the cleaning liquid (ii), but if performed after the cleaning with the cleaning liquid (ii), an additional cleaning effect without risk of film deterioration. Can be obtained.

  After cleaning with the above-described cleaning liquid (ii) or the like, usually, high-purity water such as pure water is passed to perform final cleaning, and the process proceeds to the next inhibition rate improving process.

[Prevention rate improvement processing]
In this invention, there is no restriction | limiting in particular as a rejection rate improvement agent used for the rejection rate improvement process after the washing | cleaning process of said RO membrane, Any conventionally used for the rejection rate improvement process of RO membrane is applied suitably. For example, it is preferable to use a blocking rate improver such as the following (1) to (4).
(1) An aqueous solution containing a compound having a polyalkylene glycol chain having a weight average molecular weight of 2,000 to 6,000 (hereinafter referred to as “blocking rate improver (1)”).
(2) An aqueous solution containing a first organic compound having a molecular weight of less than 200, a second organic compound having a molecular weight of 200 or more and less than 500, and a third organic compound having a molecular weight of 500 or more (hereinafter referred to as “blocking rate improver (2)”. ")
(3) An aqueous solution containing one or more selected from the group consisting of polyphenols, modified polyvinyl alcohol, polymeric polysaccharides and polyamino acids, or an aqueous solution containing polyphenols and modified polyvinyl alcohol, polymeric polysaccharides and polyamino acids An aqueous solution containing one or more selected from the group consisting of the following groups (hereinafter referred to as “blocking rate improver (3)”).
(4) An aqueous solution containing a compound having an amino group and a molecular weight of 1000 or less (hereinafter referred to as “blocking rate improver (4)”).

  In any blocking rate improver, an inorganic electrolyte such as sodium chloride (NaCl), a neutral organic substance such as isopropyl alcohol or glucose, and a low molecular polymer such as polymaleic acid may be added as a tracer. By analyzing the degree of permeation of salt and glucose into the permeated water of the RO membrane, the degree of membrane repair can be confirmed.

  Hereinafter, the rejection rate improving method using each rejection rate improving agent will be described.

<Rejection rate improving method using the rejection rate improver (1)>
Examples of the polyalkylene glycol chain of the compound using the blocking rate improver (1) 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. The polyalkylene glycol chain is particularly preferably a polyethylene glycol chain. Since the compound having a polyethylene glycol chain is highly water-soluble, it can be easily handled as a blocking rate improver and has high affinity for the RO membrane surface, so that there is little deterioration in performance over time after treatment.

  As the compound having a polyalkylene glycol chain, a multi-branched structure compound such as a multi-branched polyerythritol obtained by ring-opening polymerization of tetrahydrofuran-3,4-diol, a multi-branched polyglycerol obtained by ring-opening polymerization of glycidol, etc. Can be mentioned.

  The polyalkylene glycol chain has a weight average molecular weight of 2,000 to 6,000, preferably 3,000 to 5,000. If the weight average molecular weight of the polyalkylene glycol chain is less than 2,000, the RO membrane rejection rate may not be sufficiently improved, and the fixability after processing may be lowered. If the weight average molecular weight of the polyalkylene glycol chain exceeds 6,000, the permeation flux of the RO membrane may be greatly reduced. The weight average molecular weight can be obtained by analyzing an aqueous solution of a compound having a polyalkylene glycol chain by gel permeation chromatography (GPC) and converting the obtained chromatogram into the molecular weight of a polyethylene oxide standard product.

As the compound having a polyalkylene glycol chain, a compound in which an ionic group is introduced into the polyalkylene glycol chain can be used. Examples of the ionic group include a sulfo group —SO ₃ H, a carboxyl group —COOH, an amino group —NH ₂ , and a quaternary ammonium group —N ⁺ R ₃ X ^— . In order to prevent the occurrence of scale, the RO membrane is often subjected to a filtration operation under weakly acidic conditions. In this case, since it becomes anion-rich, introduction of a strong anionic sulfo group is effective.

  In the RO membrane rejection rate improving method using the rejection rate improving agent (1), the concentration of the compound having a polyalkylene glycol chain is preferably 0.01 to 10 mg / L, more preferably 0.1 to 5 mg / L. The blocking rate improver (1) is made to contact with the RO membrane, preferably at an operating pressure that generates permeated water. The operating pressure is preferably the same level as that during actual use. The concentration of the compound having a polyalkylene glycol chain of the rejection rate improving agent (1) can be selected in consideration of concentration polarization. By passing a low-concentration aqueous solution and performing a filtration operation, it is possible to efficiently form a thin adsorption layer in the water passage, and to minimize the decrease in permeation flux. If the concentration of the compound having a polyalkylene glycol chain is less than 0.01 mg / L, the adsorption layer may be incomplete, and the rejection rate may not be sufficiently improved. If the concentration of the compound having a polyalkylene glycol chain exceeds 10 mg / L, the adsorption layer may become too thick, and the permeation flux may be greatly reduced.

  In the RO membrane rejection rate improving method by the rejection rate improving agent (1), a modifier having a polyalkylene glycol chain and a water-soluble polymer having a hydrophobic group having 8 or more carbon atoms is used in combination. Also good. The modifier is composed of a water-soluble polymer having a hydrophobic group having 8 or more carbon atoms, but is preferably a modifier having a hydrophobic group comprising an alkyl group or alkylene group having 8 or more carbon atoms, particularly 8 to 20 carbon atoms. A modifier having a hydrophobic group comprising an alkyl group or an alkylene group is preferred. Here, a hydrophobic group consisting of an alkyl group or alkylene group having 8 or more carbon atoms, especially 8 to 20 carbon atoms has high hydrophobicity and high affinity with organic hydrophobic groups. It is presumed that it is suitable for blocking the permeation of low-molecular water-soluble organic components that require exclusion. If the carbon number is less than 8, the effect of improving the rejection rate and the stability are not sufficient, and if the carbon number exceeds 20, it is difficult to dissolve in water, and the permeation flux tends to decrease greatly.

As the modifier, a surfactant having a hydrophilic group and a hydrophobic group is preferable, and polyoxyethylene alkyl (or alkenyl) ether, polyoxyethylene alkyl (or alkenyl) phenyl ether, alkyl (or alkenyl) glucoside, polyoxy Ethylene sorbitan fatty acid ester, alkyl (or alkenyl) trimethylammonium chloride, dialkyl (or alkenyl) dimethylammonium chloride, alkyl (or alkenyl) pyridinium chloride, and the like can be used.
In addition, these surface active substances can also be used as a blocking rate improver (1).

  The molecular weight of the modifier is not particularly limited, but a weight average molecular weight of 500 to 5,000 is preferable. If the weight average molecular weight is too small, particularly less than 500, the fixability of the modifying agent after the treatment is lowered, and the blocking rate of the RO membrane is not sufficiently improved. If the weight average molecular weight is too large, especially exceeding 5,000, the permeation flux of the RO membrane may be greatly reduced.

  The treatment with the modifier is performed simultaneously with the treatment with the rejection rate improver (1), or the treatment with the modifier is performed after the treatment with the rejection rate improver (1). In the case where the treatment with the rejection rate improver (1) and the treatment with the modifier are performed simultaneously, the mixture treatment is performed using the mixed treatment agent containing the rejection rate improver (1) and the modifier, and the treatment is performed separately. Performs the treatment with the modifier after the treatment with the blocking rate improver (1). As the rejection rate improving agent (1) and the modifying agent, those suitable for the material and form of the RO membrane to be treated are selected. In the case of carrying out the mixed agent treatment, the concentration of the compound having a polyalkylene glycol chain can be 2 times or more, preferably 2 to 100 times, more preferably 2 to 20 times the concentration of the modifying agent.

<Rejection rate improving method using the rejection rate improver (2)>
In the rejection rate improver (2), examples of the first organic compound having a molecular weight of less than 200 and the second organic compound having a molecular weight of 200 or more and less than 500 include the following.

Aromatic amino compounds: For example, those having a benzene skeleton and an amino group such as aniline and diaminobenzene. Aromatic aminocarboxylic acid compounds: For example, 3,5-diaminobenzoic acid, 3,4-diaminobenzoic acid, 2, Those having a benzene skeleton such as 4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 2,4,6-triaminobenzoic acid, two or more amino groups, and a carboxyl group less than the number of amino groups.

Aliphatic amino compound: for example, a straight-chain hydrocarbon group having about 1 to 20 carbon atoms such as methylamine, ethylamine, octylamine, 1,9-diaminononane (C ₉ H ₁₈ (NH ₂ ) ₂ ) and one or Those having a plurality of amino groups, and aminopentane (NH ₂ (CH ₂ ) ₂ CH (CH ₃ ) ₂ ), 2-methyloctadiamine (NH ₂ CH ₃ CH (CH ₃ ) (CH ₂ ) ₆ NH ₂ And the like having a branched hydrocarbon group having about 1 to 20 carbon atoms and one or more amino groups.

Aliphatic amino alcohol: A linear or branched hydrocarbon group having 1 to 20 carbon atoms, such as monoaminoisopentanol (NH ₂ (CH ₂ ) ₂ CH (CH ₃ ) CH ₂ OH), and an amino group and a hydroxyl group. What you have.

  -Heterocyclic amino compound: A compound having a heterocyclic ring and an amino group such as tetrahydrofurfurylamine (the following structural formula).

  Amino acid compounds: For example, basic amino acid compounds such as arginine and lysine, amino acid compounds having an amide group such as asparagine and glutamine, and other amino acid compounds such as glycine and phenylalanine.

  -Ethylenediamines: polyethyleneamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine

  Of these, amino acids or amino acid compounds (amino acid derivatives) are preferred as the first organic compound (with a molecular weight of less than 200).

  For example, arginine (molecular weight 174), lysine (molecular weight 146), and histidine (molecular weight 155), which are basic amino acids, can be effectively used as the first organic compound. Further, as a peptide or a derivative thereof, for example, aspartame (molecular weight 294) which is a methyl ester of a dipeptide of phenylalanine and aspartic acid can be effectively used as the second organic compound. In addition, carnosine (molecular weight: 226), Nα- (L-tyrosyl) -L-arginine (molecular weight: 336), pyrimidine-2,4,5,6-tetraamine (molecular weight 140) and the like are also effectively used.

  These low molecular weight amino compounds are highly soluble in water and can be passed through the reverse osmosis membrane as a stable aqueous solution, reacting with the carboxyl group of the membrane and binding to the RO membrane to form an insoluble salt. Thus, the holes caused by the deterioration of the film are closed, thereby increasing the blocking rate of the film.

  These low molecular weight amino compounds may be used individually by 1 type, and 2 or more types may be mixed and used for them. In particular, when two or more kinds of low molecular weight amino compounds having different molecular weights and skeletal structures are used in combination, and these are simultaneously permeated through the RO membrane, each compound becomes an obstacle when permeating through the membrane, and causes deterioration in the membrane. A longer residence time is preferable because the contact probability between the carboxyl group of the film and the amino group of the low molecular weight amino compound is increased, and the effect of repairing the film is enhanced.

  The contents of the first and second organic compounds in the rejection rate improver (2) vary depending on the degree of deterioration of the membrane, but if excessively large, the permeation flux may be greatly reduced, and if excessively small Since the repair becomes insufficient, the total concentration of the first and second organic compounds in the rejection improvement treatment water should be about 0.2 to 500 mg / L, particularly about 1 to 200 mg / L. preferable.

  As the third organic compound having a molecular weight of 500 or more (preferably 500 to 500,000, particularly preferably 500 to 50,000), those having a carboxyl group, an amino group or a hydroxyl group are suitable. Examples include tannic acid and peptides. Examples of tannic acid include hydrolyzable pentaploid, gallic, condensed kebracho and mimosa. Examples of the peptide include polyglycine, polylysine, polytryptophan, polyalanine and the like having a molecular weight of 500 or more.

  The concentration of the third organic compound in the rejection rate improver (2) is preferably about 0.1 to 1000 mg / L, particularly about 0.5 to 100 mg / L.

  When the rejection rate improver (2) is passed through the RO membrane, if the water supply pressure is excessively high, there is a problem that adsorption to a non-deteriorated area proceeds. If it is excessively low, adsorption to the deteriorating area also proceeds. Therefore, it is preferably 30 to 150%, particularly 50 to 130% of the normal operating pressure of the RO membrane.

  The rejection improvement process by the rejection improvement agent (2) can be performed at room temperature, for example, a temperature of about 10 to 35 ° C., and as the treatment time, each organic compound sufficiently permeates through the RO membrane. The time is sufficient to detect the organic compound on the permeate side, and there is no particular upper limit, but it is usually preferably 0.5 to 100 hours, particularly preferably about 1 to 50 hours.

<Rejection rate improving method using the rejection rate improver (3)>
In the rejection improvement process using the rejection improvement agent (3), an aqueous solution containing one or more selected from the group consisting of polyphenol, modified polyvinyl alcohol, polymeric polysaccharide and polyamino acid is passed through the RO membrane. After passing an aqueous solution containing polyphenol through the RO membrane, an aqueous solution containing one or more selected from the group consisting of modified polyvinyl alcohol, high molecular polysaccharides and polyamino acids is applied to the RO membrane. It may be performed by passing water. In this case, the aqueous solution containing one or more selected from the group consisting of modified polyvinyl alcohol, polymer polysaccharide and polyamino acid may contain polyphenol (hereinafter, modified polyvinyl alcohol, polymer polysaccharide). And one or more selected from the group consisting of polyamino acids may be referred to as “second blocking rate improving component”.

  In this method, it is further preferable to pass an aqueous solution containing an organic compound having a molecular weight of 1000 or less (low molecular weight amino compound) through the RO membrane.

(Polyphenol)
The polyphenol is preferably a polyphenol having a molecular weight of 500 or more, particularly a molecular weight of 500 to 500,000, particularly a molecular weight of 500 to 50,000 in terms of effectively covering and fixing the surface of the RO membrane. For example, tannic acid, lignin And lignin derivatives. Examples of tannic acid include tannic acid such as pentaploid, gallic, quebracho and mimosa. These polyphenols may be used alone or in combination of two or more.

(Second blocking rate improving component)
As the second blocking rate improving component, only one of the following modified polyvinyl alcohol, high molecular polysaccharide and polyamino acid may be used, or two or more of these may be used in combination.

<Modified polyvinyl alcohol>
The modified polyvinyl alcohol is composed of a vinyl alcohol unit and a unit to which a modifying group is bonded, and optionally further includes a vinyl acetate unit.

  The molar fraction of the unit to which the modifying group in the modified polyvinyl alcohol is bonded is preferably 0.1 to 50 mol%, more preferably 0.3 to 40 mol%, and particularly preferably 0.5 to 30 mol%. preferable. If the molar fraction of the unit to which the modifying group is bonded is lower than this range, the effect of improving the adsorptivity to the RO membrane by introducing the modifying group cannot be sufficiently obtained. In addition, the mole fraction of the vinyl alcohol unit is reduced, and the effect of improving the rejection is reduced.

  Moreover, 50-99.9 mol% is preferable, as for the molar fraction of the vinyl alcohol unit in modified polyvinyl alcohol, 60-99.7 mol% is more preferable, and 70-99.5 mol% is especially preferable. If the molar fraction of the vinyl alcohol unit is less than this range, the number of hydroxyl groups in the modified polyvinyl alcohol will decrease, and a sufficient blocking rate improvement effect will not be obtained. There is a possibility that the molar fraction of the unit being reduced decreases and the effect of improving the adsorptivity to the RO membrane by introducing the modifying group cannot be sufficiently obtained.

  Moreover, 0-20 mol% is preferable, as for the molar fraction of the vinyl acetate unit in modified polyvinyl alcohol, 0-10 mol% is more preferable, and 0-5 mol% is especially preferable.

  There is a degree of saponification as an index indicating the properties of polyvinyl alcohol. The saponification degree is obtained by dividing the molar fraction of the vinyl alcohol unit by the sum of the molar fractions of the vinyl alcohol unit and the vinyl acetate unit. The saponification degree of the modified polyvinyl alcohol is preferably 80% or more, particularly 85% or more, particularly 95% or more. When the degree of saponification is less than 80%, the number of hydroxyl groups is small, the hydrophilicity is lowered, and there is a tendency that a sufficient inhibition rate improving effect and flux stability cannot be obtained.

  Moreover, although there is no restriction | limiting in particular as a polymerization degree of modified polyvinyl alcohol, ie, said number of units, 20-20,000 are preferable. If the degree of polymerization is too low, the adsorptivity to the membrane is deteriorated, and if the degree of polymerization is too high, the decrease in the flux of the RO membrane due to the inhibition rate improvement treatment is increased, which is not preferable.

  The modifying group of the modified polyvinyl alcohol preferably contains an ionic group, a polyalkylene oxide group (a group having a polyoxyalkylene oxide chain), or both. In particular, when a modified polyvinyl alcohol having a quaternary ammonium group is selected, interaction with a carboxyl group or polyphenol on the RO membrane surface can be expected. Moreover, since the polyethylene glycol chain is adsorbed on the polyamide RO membrane by selecting a modified polyvinyl alcohol having a polyethylene oxide group, interaction with the RO membrane can be expected.

The cationic polyvinyl alcohol having a cationic group as a modifying group is preferably, for example, one produced by copolymerization of a vinyl ester such as vinyl acetate and a cationic monomer and then hydrolysis (saponification).
As the cationic monomer, monomers having —NH ₂ , —NHR, —NRR ′, —NH ₃ ⁺ , —NH ₂ R, —NHRR ′ ⁺ , —NRR′R ″ ⁺ (R, R ′, R ′ 'Each represents a hydrocarbon residue.), Specifically, diallyldimethylammonium salt, acrylates and methacrylates having an ammonium group, N-substituted methacrylamide, vinylpyridine, vinylpyridine quaternary ammonium salt, vinylimidazole Etc.

  Examples of commercially available products of cationic polyvinyl alcohol include “C-506”, “CM-318” (manufactured by Kuraray Co., Ltd.), and “Gosefimer K-210” (manufactured by Nippon Synthetic Chemical Industry).

  Examples of the anionic group of the anionic polyvinyl alcohol having an anionic group as a modifying group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group. Acid groups are preferred.

  As a method for producing a modified polyvinyl alcohol having a carboxyl group introduced into polyvinyl alcohol, an unsaturated basic acid, an unsaturated dibasic acid, an anhydride thereof, or an anhydride thereof that can be copolymerized with a vinyl ester such as vinyl acetate is used. Examples thereof include a method for saponifying a copolymer obtained by copolymerizing an ester or a salt, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride and the like.

  The carboxyl group-modified polyvinyl alcohol can also be obtained by saponifying the vinyl ester and a copolymer such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide.

  Examples of the graft polymerization method include a method of graft polymerization of acrylonitrile, acrylamide or the like to a polyvinyl ester such as polyvinyl alcohol or polyvinyl acetate, followed by saponification. In addition, as a method of chemical reaction of polyvinyl alcohol, a piece in which polyvinyl alcohol is reacted with a dibasic acid such as maleic acid, fumaric acid, phthalic acid, malonic acid, succinic acid, oxalic acid, adipic acid, or an anhydride thereof. A carboxyl group can also be introduced into polyvinyl alcohol by an esterification reaction.

  When introducing a sulfonic acid group into polyvinyl alcohol, a method of reacting polyvinyl alcohol with concentrated sulfuric acid, ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, or their A sulfonic acid group-modified polyvinyl alcohol can be obtained by copolymerization of an ester or salt with vinyl acetate and then saponification.

  Examples of commercially available anionic polyvinyl alcohol include “KL-118”, “KL-318”, “KM-118”, “KM-618”, “SK-5102” (manufactured by Kuraray), “Gosenal T- 330 ”,“ Gocenal T-330H ”,“ Gocenal T-350 ”,“ Goceran L-3266 ”,“ Goceran L-0301 ”,“ Goceran L-0302 ”,“ Goceran CKS-50 ” (Made by industry) etc. are illustrated.

  The polyalkylene oxide chain of the modified polyvinyl alcohol having a polyalkylene oxide chain is preferably a polyalkylene oxide chain having 2 to 4 carbon atoms of an alkylene group such as polyethylene oxide, polypropylene oxide, polybutylene oxide, and the like. Most preferred. The number of repeating alkylene oxides is preferably 2 to 300, more preferably 10 to 100. If the number of repetitions is too small, the effect of improving the adsorptivity to the RO membrane by the polyalkylene oxide chain cannot be sufficiently obtained, and if it is too large, the decrease in the flux of the RO membrane due to the inhibition rate improvement treatment becomes large. It is not preferable.

  The modified polyvinyl alcohol having such a polyalkylene oxide chain can be obtained by a known synthesis method. Commercial products such as “Ecomati WO-320N” and “Ecomati WO-320R” manufactured by Nippon Synthetic Chemical Industry can also be used.

  As a method for synthesizing a modified polyvinyl alcohol having a polyalkylene oxide chain, a method in which a monomer having a polyalkylene oxide chain is polymerized with vinyl acetate, and then a part or all of vinyl acetate is saponified to give vinyl alcohol is preferable. However, other synthesis methods may be used.

Examples of the monomer having a polyalkylene oxide chain include polyethylene oxide monovinyl ether, polypropylene oxide monovinyl ether, polyethylene oxide monoallyl ether, polyethylene glycol monomethacrylate, polyethylene glycol monoacrylate, polypropylene glycol monomethacrylate, polypropylene glycol monoacrylate, Polyethylene glycol-polypropylene glycol monomethacrylate, polyethylene glycol-polypropylene glycol monoacrylate, poly (ethylene glycol-tetramethylene glycol) monomethacrylate, poly (ethylene glycol-tetramethylene glycol) monoacrylate, poly (ethylene glycol-propylene glycol) Call) monomethacrylate, methoxy polyethylene glycol - and polypropylene glycol monoacrylate and the like.
These may be used alone or in combination of two or more.

<Polymer polysaccharide>
As the high molecular polysaccharide, a high molecular weight polysaccharide having a molecular weight of 10,000 or more, particularly used as a food additive, can be preferably used. There is no particular upper limit on the molecular weight of the high molecular polysaccharide, and any polymer that exhibits water solubility can be used. Examples of such high molecular polysaccharides include xanthan gum (molecular weight: 2 million or more), guar gum (molecular weight: 200 to 300,000), carboxymethyl cellulose and salts thereof (molecular weight: 50,000 or more), alginic acid and salts thereof (molecular weight). : 10,000 or more), chitosan (molecular weight: 10,000 or more), and the like.

These high molecular polysaccharides are usually used as thickeners and show good adsorptivity to the RO membrane. That is, for example, when an aqueous solution of xanthan gum 1 mg / L was passed through an aromatic polyamide RO membrane (ES20) manufactured by Nitto Denko Corporation at 0.75 MPa, the permeation flux was 0.9 m ³ / m in 7 days. It decreased from ² · day to 0.5 m ³ / m ² · day. This can be said to be because the permeability of xanthan gum to the RO membrane is high and the permeation flux of the membrane was lowered. In the case of guar gum, the permeation flux decreased from 0.9 m ³ / m ² · day to 0.3 m ³ / m ² · day in 7 days in the same test. Thus, it can be said that what reduces the permeation | transmission flux of RO membrane by water flow has high adsorptivity with respect to RO membrane.

  These polymer polysaccharides may be used alone or in combination of two or more.

<Polyamino acid>
As polyamino acids, polylysine, polyglycine, polyglutamic acid, etc., which are polymers of one amino acid with a molecular weight of 1,000 or more and 1,000,000 or less, can be used, and polymers of two or more amino acids are also used. Can do. In particular, polylysine, polyarginine and polyhistidine which are polymers of basic amino acids can be suitably used. In particular, polylysine is preferable because it has a strong electrostatic interaction with polyphenols, and can be used in combination with polyphenols to obtain a high blocking rate improving treatment effect. These polyamino acids may be used alone or in combination of two or more.

(Low molecular weight amino compounds)
In the rejection improvement process using the rejection improvement agent (3), in addition to the polyphenol and the second rejection improvement component, the rejection is improved using an organic compound having a molecular weight of 1000 or less (low molecular weight amino compound). Treatment may be carried out, and the combined use of a low molecular weight amino compound can further enhance the effect of improving the rejection.

  As the low molecular weight amino compound, those having a molecular weight of 1000 or less, particularly less than 500, for example, having a molecular weight of 70 to 300 are preferable in terms of the effect of repairing the deteriorated portion of the RO membrane. Examples thereof include those exemplified as the first organic compound having a molecular weight of less than 200 and the second organic compound having a molecular weight of 200 or more and less than 500, which are used in the rejection rate improver (2). One kind of these low molecular weight amino compounds may be used, or two or more kinds may be used, but the work becomes complicated as the number of kinds increases.

  As described above, these low molecular weight amino compounds are highly soluble in water and can pass through the RO membrane as a stable water-soluble substance, react with the carboxyl group of the membrane, bind to the RO membrane, and form an insoluble salt. It can be formed to close holes created by film degradation.

(Inhibition rate improving component concentration)
Concentrations in the polyphenol, the second blocking rate improving component, and the blocking rate improver (3) of the low molecular weight amino compound, when only one of them is contained, When two or more of these are included, the total concentration is preferably 1.0 to 5,000 mg / L, and more preferably 1.0 to 2,000 mg / L. If this concentration is too low, a long-term treatment is required, which is not preferable. On the other hand, if this concentration is too high, the number of compounds that adsorb in multiple layers on the surface of the film and do not reach the deteriorated portion increases, and the repair efficiency deteriorates.

  Further, in order to more effectively obtain the effect of using the polyphenol and the second rejection rate improving component in combination, the concentration is calculated from the concentration in the rejection rate improver (3) and the amount of the aqueous solution that passes through the RO membrane. As a total supply amount to the RO membrane, the weight ratio of polyphenol to the second rejection ratio improving component is: polyphenol: second rejection ratio improving component = 1: 0.1-5, particularly 1: 0.1-2. It is preferable to use so that it may become this range.

  Further, when a low molecular weight amino compound is used, the low molecular weight amino compound is calculated as the total supply amount to the RO membrane calculated from the concentration in the blocking rate improver (3) and the amount of the aqueous solution that passes through the RO membrane. The polyphenol and the low molecular weight amino compound are preferably used so that the weight ratio of polyphenol: low molecular weight amino compound is 1: 0 to 2, particularly 1: 0.1 to 1.

(Processing procedure)
In the case of using polyphenol and the second blocking rate improving component, and also a low molecular weight amino compound in combination, there is no particular limitation on the order of water passage of the polyphenol, the second blocking rate improving component and the low molecular weight amino compound to the RO membrane, These may be added to a single aqueous solution and subjected to a blocking rate improvement treatment using one type of blocking rate improver (3), or these may be passed through the RO membrane as separate aqueous solutions.

  When processing separately, it is preferable to perform the process by the 2nd rejection rate improvement component last. In other words, the second blocking rate improving component is for coating polyphenols and low molecular weight amino compounds to increase their adsorption stability, and the second blocking rate improving component is added prior to polyphenols and low molecular weight amino compounds. If adsorbed on the RO membrane, there is a possibility that the adsorption of polyphenols and low molecular weight amino compounds to the RO membrane may be inhibited, which is not preferable.

The following modes are mentioned as a specific water flow order.
(1) The aqueous solution containing the polyphenol and the second inhibition rate improving component is passed through the RO membrane.
(2) After passing the aqueous solution containing polyphenol through the RO membrane, the aqueous solution containing the second inhibition rate improving component is passed through the RO membrane.
(3) After passing the aqueous solution containing polyphenol through the RO membrane, the aqueous solution containing the polyphenol and the second inhibition rate improving component is passed through the RO membrane.
(4) The aqueous solution containing the polyphenol, the second blocking rate improving component, and the low molecular weight amino compound is passed through the RO membrane.
(5) The aqueous solution containing the polyphenol and the low molecular weight amino compound is passed through the RO membrane, and then the aqueous solution containing the second inhibition rate improving component is passed through the RO membrane.
(6) After passing an aqueous solution containing polyphenol and a low molecular weight amino compound through the RO membrane, an aqueous solution containing the polyphenol, the low molecular weight amino compound and the second blocking rate improving component is passed through the RO membrane.

If the pressure at the time of passing the blocking rate improver (3) through the RO membrane is excessively high, the permeation flux decreases due to the progress of adsorption of the blocking rate improving component to the undegraded portion of the RO membrane. There is a problem, and if it is too low, the contact efficiency of the component for improving the rejection rate to the deteriorated portion of the RO membrane may be lowered, and the intended effect of improving the rejection rate may not be obtained. Considering that it is preferable to carry out the present invention as it is after washing the RO membrane with a washing device, the water flow pressure (inlet pressure) of the rejection rate improver (3) is 0.1 to 0.5 MPa. preferable. Compared to the normal operating pressure of the RO membrane, it is preferably 10 to 150%, particularly 25 to 100%. The permeation flux during the rejection improvement process is related to pressure, water temperature, membrane shape, etc., but is preferably 0.1 to 1.0 m ³ / (m ² d). The reason for this is that, as described above, if it is excessively high, there is a problem that the adsorption to the portion where the RO membrane is not deteriorated, and if it is too low, the contact efficiency to the deteriorated portion of the RO membrane is deteriorated.

  The treatment time is not particularly limited as long as it is 1 hour or longer, but is preferably 1 hour or more and 48 hours or less. If the treatment time is less than 1 hour, the treatment may be terminated without sufficient fixing property of the rejection rate improving component being obtained, and the rejection rate improving component attached to the RO film may be peeled off, which is preferable. Absent.

  The temperature (water temperature) during the treatment is preferably 10 to 35 ° C. If the water temperature is too low, the amount of permeated water is reduced, and the contact efficiency between the blocking rate improving component and the RO membrane is deteriorated. If the water temperature becomes too high, problems such as denaturation of the membrane material may occur.

<Rejection rate improvement treatment using a rejection rate improver (4)>
The amino compound used in the blocking rate improver (4) has an amino group and has a relatively low molecular weight of 1,000 or less, and there is no particular limitation, but the molecular weight used in the blocking rate improver (2) is not particularly limited. Examples thereof include those exemplified as the first organic compound having a molecular weight of less than 200 and the second organic compound having a molecular weight of 200 or more and less than 500.

  Among the aforementioned low molecular weight amino compounds, basic amino acids such as arginine (molecular weight 174), lysine (molecular weight 146), and histidine (molecular weight 155) can be used effectively. As a peptide or a derivative thereof, for example, aspartame (molecular weight 294) which is a methyl ester of a dipeptide of phenylalanine and aspartic acid can be used effectively.

  As described above, these low molecular weight amino compounds are highly soluble in water and can pass through the permeable membrane as a stable aqueous solution. As described above, these low molecular weight amino compounds react with the carboxyl groups of the membrane and bind to the permeable membrane. Insoluble salts are formed to close the holes caused by the deterioration of the film, thereby increasing the blocking rate of the film.

  If the molecular weight of the low molecular weight amino compound used in the blocking rate improver (4) is greater than 1000, it may not be possible to enter a finely degraded portion, which is not preferable. However, if the molecular weight of the amino compound is excessively small, it is difficult to stay in the dense layer of the film. Therefore, the molecular weight of this amino compound is preferably 1000 or less, particularly 500 or less, and particularly 60 to 300.

  These low molecular weight amino compounds may be used individually by 1 type, and 2 or more types may be mixed and used for them. In particular, when two or more low molecular weight amino compounds having different molecular weights and skeletal structures are used in combination, and these are allowed to permeate through the permeable membrane at the same time, each compound becomes an obstacle when permeating the membrane, and causes deterioration in the membrane. A longer residence time is preferable because the contact probability between the carboxyl group of the film and the amino group of the low molecular weight amino compound is increased, and the effect of repairing the film is enhanced.

  For this reason, a low molecular weight amino compound having a molecular weight of several tens, for example, about 60 to 300, and a low molecular weight amino compound having a molecular weight of several hundreds, for example, about 200 to 1,000 are used in combination, or a cyclic compound and a chain compound are further linearized. It is preferable to use a compound and a branched compound in combination.

  Preferred examples of the combination include the combined use of diaminobenzoic acid and 1,9-diaminononane or aminopentane, and the combined use of aniline and 2-methyloctadiamine or arginine and aspartame.

  The content of the low molecular weight amino compound in the rejection improving agent (4) varies depending on the degree of deterioration of the membrane, but if it is excessively large, the permeation flux may be lowered, and if it is excessively small, the repair becomes insufficient. Therefore, the concentration of the low molecular weight amino compound in the rejection rate improver (4) (when two or more low molecular weight amino compounds are used, the total concentration thereof) is about 1 to 1000 mg / L, particularly about 5 to 500 mg / L. It is preferable that

  In addition, when two or more kinds of low molecular weight amino compounds are used, if there is a large difference in the concentration of each low molecular weight amino compound, it is difficult to obtain the effect of the combined use. On the other hand, it is preferable to blend so that the content of the low molecular weight amino compound contained in the smallest amount is 50% or more.

  In the blocking rate improver (4), a low molecular weight organic compound having a molecular weight of 1000 or less other than the above low molecular weight amino compound, for example, an alcohol compound, a compound having a carboxyl group or a sulfonic acid group, specifically, Butanol, salicylic acid or isothiazoline-based compounds may be added to such a concentration that does not polymerize with low molecular weight amino compounds, for example, about 0.1 to 100 mg / L, thereby increasing the steric hindrance in the dense layer, It is expected to increase the effect of clogging.

  It is also effective to use in combination with a polymer having a carboxyl group, amino group or hydroxyl group having a molecular weight of 1000 to 10,000. Examples include tannic acid and peptides. Examples of tannic acid include hydrolyzable pentaploid, gallic, condensed kebracho and mimosa. Examples of the peptide include polyglycine, polylysine, polytryptophan, polyalanine and the like having a molecular weight of 1000 or more.

  Further, when the water supply pressure when the rejection rate improver (4) is passed through the RO membrane is excessively high, there is a problem that the adsorption to a non-degraded portion proceeds. Therefore, it is preferable to set it to 30 to 150%, particularly 50 to 130% of the normal operating pressure of the RO membrane.

  The rejection improvement process by the rejection improvement agent (4) can be performed at room temperature, for example, a temperature of about 10 to 35 ° C., and the treatment time depends on the concentration of the low molecular weight amino compound to be supplied. Although there is no restriction | limiting especially an upper limit, Usually, it is preferable to set it as about 0.5 to 100 hours, especially 1 to 50 hours.

[Reverse osmosis membrane]
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 RO membrane to which the present invention is applied include polymer membranes such as asymmetric membranes and composite membranes. Examples of the RO membrane material include aromatic polyamides, aliphatic polyamides, polyamide materials such as composite materials thereof, and cellulose materials such as cellulose acetate. Among these, the RO membrane rejection ratio improving method of the present invention is particularly suitable for a membrane made of an aromatic polyamide material and having many carboxyl groups due to degradation of CN bonds due to deterioration. Can be applied.
In particular, when the desalination rate of the RO membrane before the rejection improvement process is 90% or less, it is suitable for applying the method of the present invention.

  The RO membrane module type is not particularly limited, and examples thereof include a tubular membrane module, a planar membrane module, a spiral membrane module, and a hollow fiber membrane module.

[Water treatment method]
In the water treatment method of the present invention in which the RO membrane treatment is performed by allowing the water to be treated to permeate through the RO membrane of the present invention treated by the method of improving the rejection rate of the present invention, the RO membrane is blocked with a high permeation flux. The rate can be improved and the high state can be maintained for a long time, whereby the removal effect of a substance to be removed such as an organic substance is high, and a stable treatment is possible over a long period of time.
For this reason, the RO membrane treated by the method for improving the rejection rate of the present invention is used for recovering / reusing wastewater containing high or low concentration TOC discharged in the electronic device manufacturing field, semiconductor manufacturing field, and other various industrial fields. Therefore, it is effectively applied to water treatment for industrial use, ultrapure water production from industrial water and city water, and water treatment in other fields.

  The treatment water can be supplied and permeated in the same way as normal RO membrane treatment, but when treating water containing hardness components such as calcium and magnesium, the raw water contains dispersant and scale prevention. Agents and other agents may be added. The water to be treated is not particularly limited, but can be suitably used for organic substance-containing water. For example, TOC = 0.01 to 100 mg / L, preferably about 0.1 to 30 mg / L. It is suitably used for the treatment of organic substance-containing water. Examples of such organic substance-containing water include, but are not limited to, wastewater from electronic device manufacturing factories, transportation machinery manufacturing factories, organic synthesis factories, printing plate making / painting factories, or the primary treatment water thereof. .

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

  In the following Examples and Comparative Examples, the deteriorated film subjected to the water flow test, the rejection rate improver, the cleaning liquid, the performance evaluation water, and the performance evaluation apparatus used in the test are as follows.

<Deteriorated film>
Hydronautics 8-inch RO membrane element “CPA3” used for 3 years in pure water production
Flux of "CPA3" new film, salt rejection, IPA removal rate, ^{respectively, 0.90m 3 / (m 2 d} ), 99%, 88%.

The permeation flux, NaCl removal rate (desalting rate), and IPA removal rate of the evaluation membrane were calculated from the following equations, respectively.
Permeation flux [m ³ / (m ² d)] =
Permeate volume [m ³ / d] / membrane area [m ² ] × temperature conversion coefficient [−]
NaCl removal rate [%] =
{1-permeated water conductivity [mS / m] × 2 / (treated water conductivity [mS / m]
+ Concentrated water conductivity [mS / m])} × 100
IPA removal rate [%] =
{1-permeated water TOC [mg / L] × 2 / (treated water TOC [mg / L]
+ Concentrated water TOC [mg / L])} × 100

<Blocking rate improver>
Constituents of the blocking rate improver I: 10 mg / L arginine (manufactured by Ajinomoto Healthy Supply), 10 mg / L aspartame (manufactured by Ajinomoto Healthy Supply), 10 mg / L tannic acid AL (manufactured by Fuji Chemical Industries)
Constituent components of the blocking rate improver II: 2 mg / L polyethylene glycol 4000 (manufactured by Wako Pure Chemical Industries), 0.5 mg / L polyoxyethylene (100) stearyl ether (manufactured by SIGMA-ALDRICH)

<Cleaning liquid>
Cleaning solution A: pH 12.5 sodium hydroxide aqueous solution of 0.1 mM sodium hypochlorite (theoretical effective chlorine concentration 7 mg / L)
Cleaning solution B: pH 11.5 aqueous solution of 20 mM sodium hypochlorite and 40 mM ammonia (chloramine concentration 20 mM)
Cleaning solution C: pH 12.5 sodium hydroxide aqueous solution of 20 mM sodium hypochlorite and 40 mM sulfamic acid (monochlororosulfamin concentration 20 mM)
Washing solution D: pH 12.5 sodium hydroxide aqueous solution of 80 mM sodium hypochlorite and 160 mM sulfamic acid (monochlororosulfamin concentration 80 mM)
Cleaning solution E: pH 12.5 sodium hydroxide aqueous solution

<Performance evaluation water>
NaCl 500mg / L, isopropyl alcohol (IPA) 100mg / L dissolved in pure water

<Performance evaluation apparatus: RO test apparatus shown in FIG. 3>
In this RO test apparatus, water to be treated is supplied from a pipe 11 to a primary side (raw water side) of a vessel 1 loaded with one 8-inch deteriorated membrane element by a pump P, concentrated water is taken out from a pipe 12, and permeated water. Is taken out from the pipe 13. The treated water supply pipe 11 and the concentrated water discharge pipe 12 are respectively provided with pressure gauges 2 and 3, and the concentrated water discharge pipe 12 is provided with a pressure adjustment valve 4.

[Example 1]
Using the cleaning liquid A as the cleaning liquid and the blocking rate improver I as the blocking rate improver, water was passed through a performance evaluation apparatus loaded with a deteriorated film by the following procedures [1] to [6]. In all steps, the water temperature was 25 ° C. ± 2 ° C.

[1] Performance evaluation: Water flow: Operation pressure: 0.75 MPa, water flow time: 2 hours [2] Washing with cleaning liquid: Water flow through the cleaning liquid at 0.2 MPa for 30 minutes, then 15 hours
Immersion, then exchanged with pure water for 30 minutes at 0.2 MPa [3] Pure water flow: Operating pressure 0.75 MPa, water flow time 24 hours [4] Performance evaluation Water flow: Operation pressure 0.75 MPa Water passage time: 2 hours [5] Water blocking ratio improving agent water flow: Operation pressure: 0.2 MPa, Water flow time: 15 hours [6] Performance evaluation: Water flow: Operation pressure: 0.75 MPa, Water flow time: 2 hours

  Performance evaluation of [1] Permeation flux of evaluation membrane at the time of water flow, evaluation result before washing of NaCl removal rate and IPA removal rate, Performance evaluation of [4] Permeation flux of evaluation membrane at the time of water flow, Evaluation results after washing the NaCl removal rate and IPA removal rate, performance evaluation of [6] Permeation flux of the evaluation membrane during water flow, NaCl removal rate and IPA removal rate as the evaluation results after improving the rejection rate, respectively The results are shown in Table 1.

[Example 2]
In Example 1, a water flow test and evaluation were performed in the same manner except that the cleaning liquid B was used as the cleaning liquid, and the results are shown in Table 1.

[Example 3]
In Example 1, a water flow test and evaluation were performed in the same manner except that the cleaning liquid C was used as the cleaning liquid, and the results are shown in Table 1.

[Example 4]
In Example 1, a water flow test and evaluation were performed in the same manner except that the cleaning liquid D was used as the cleaning liquid, and the results are shown in Table 1.

[Example 5]
In Example 4, the blocking rate improver II was used as the blocking rate improver, and the water flow test and evaluation were performed in the same manner except that the water passing time of the blocking rate improver aqueous solution of [5] was 3 hours. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, a water flow test and an evaluation were performed in the same manner except that the steps from [2] washing with the cleaning liquid to [4] performance evaluation water flow were not performed, and the results are shown in Table 1. .

[Comparative Example 2]
In Example 1, a water flow test and evaluation were performed in the same manner except that the cleaning liquid E was used as the cleaning liquid, and the results are shown in Table 1.

  From Table 1, it can be seen that by washing the RO membrane according to the present invention before the rejection improvement process, the permeation flux is greatly improved and a high rejection is obtained.

1 Vessel 2, 3 Pressure gauge 4 Open / close valve

Claims (6)

  In the method for improving the rejection rate of the reverse osmosis membrane by contacting the reverse osmosis membrane with the rejection rate improver, prior to the contact between the reverse osmosis membrane and the rejection rate improver, hypochlorous acid and / or A method for improving the rejection rate of a reverse osmosis membrane, comprising contacting a cleaning liquid comprising an alkaline solution having a pH of 10 or more containing a chlorite or a chloramine compound. In Claim 1, the said washing | cleaning liquid prepared by diluting and mixing the aqueous solution of hypochlorous acid and / or hypochlorite (henceforth "hypochlorous acid (salt)") with an alkaline agent and water. An alkaline aqueous solution of hypochlorous acid (salt),
The effective chlorine concentration of the alkaline aqueous solution of hypochlorous acid (salt) obtained by calculation based on the effective chlorine concentration of the hypochlorous acid (salt) aqueous solution before dilution and the dilution ratio is 10 mg / L or less. A method for improving the rejection of a reverse osmosis membrane.   2. The method for improving the rejection of a reverse osmosis membrane according to claim 1, wherein the cleaning liquid is an aqueous solution containing a chloramine compound and an alkaline agent. 4. The improvement in the rejection rate of a reverse osmosis membrane according to any one of claims 1 to 3, wherein the rejection rate improver is one or more of the following (1) to (4): Method.
(1) An aqueous solution containing a compound having a polyalkylene glycol chain having a weight average molecular weight of 2,000 to 6,000 (2) A first organic compound having a molecular weight of less than 200, and a second organic compound having a molecular weight of 200 or more and less than 500 An aqueous solution containing a third organic compound having a molecular weight of 500 or more (3) An aqueous solution containing one or more selected from the group consisting of polyphenols, modified polyvinyl alcohols, polymeric polysaccharides and polyamino acids, or polyphenols An aqueous solution containing an aqueous solution containing one or more selected from the group consisting of a modified polyvinyl alcohol, a polymeric polysaccharide and a polyamino acid (4) An aqueous solution containing a compound having an amino group and a molecular weight of 1000 or less   The reverse osmosis membrane processed by the rejection improvement method of any one of Claims 1 thru | or 4.   A water treatment method using the reverse osmosis membrane according to claim 5.

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