WO2016104356A1

WO2016104356A1 - Method for controlling slime on separation membrane

Info

Publication number: WO2016104356A1
Application number: PCT/JP2015/085476
Authority: WO
Inventors: 吉川　浩; 染谷　新太郎; 雅人都司; 千晴大森
Original assignee: オルガノ株式会社
Priority date: 2014-12-25
Filing date: 2015-12-18
Publication date: 2016-06-30
Also published as: KR20170084257A; SG11201704614YA; KR101966569B1; CN107108277A; TW201627057A; MY188356A; SA517381683B1; CN107108277B; TWI651123B

Abstract

Provided is a method for controlling slime on separation membranes, the method being capable of reducing trihalomethane content in permeate while having adequate slime-controlling effects in membrane separation apparatuses that use water supply or rinse water containing trihalomethane precursors. The method for controlling slime on a separation membrane adds, to trihalomethane precursor-containing water supply or rinse water for a membrane separation apparatus with a separation membrane: a bromine oxidizing agent or a reactant of a bromine compound with a chlorine oxidizing agent; a bromine oxidizing agent or a reactant of a bromine compound with a chlorine oxidizing agent, and a sulfamic acid compound; or a reaction product of a bromine oxidizing agent with a sulfamic acid compound, or a reaction product of a sulfamic acid compound with a reactant of a bromine compound with a chlorine oxidizing agent.

Description

Method for suppressing slime in separation membrane

The present invention relates to a slime suppression method for a separation membrane such as a reverse osmosis membrane (RO membrane).

As a slime suppression method for separation membranes such as reverse osmosis membranes (RO membranes), methods using various slime inhibitors are known. Chlorine oxidizers such as hypochlorous acid are typical slime inhibitors, and are usually added upstream of the separation membrane for the purpose of suppressing slime in the system. Since chlorinated oxidants are likely to deteriorate the separation membrane, it is generally possible to reduce and decompose the chlorinated oxidants immediately before the separation membrane, or intermittently flow the chlorinated oxidant into the separation membrane. It is operated (see Patent Document 1).

JP-A-9-057076

It is known that a chlorine-based oxidant reacts with trihalomethane precursors such as humic substances in water to produce trihalomethanes such as chloroform. Here, it has become clear from the examination of the present inventors that trihalomethane produced by these chlorinated oxidants is difficult to be excluded by the separation membrane and easily leaks into the permeated water of the separation membrane. .

An object of the present invention is to provide a separation membrane slime capable of reducing the trihalomethane content in the permeate while having a sufficient slime suppression effect in a membrane separation apparatus using feed water or washing water containing a trihalomethane precursor. It is to provide a suppression method.

The present invention relates to a slime of a separation membrane in which a bromine-based oxidant or a reaction product of a bromine compound and a chlorine-based oxidant is present in feed water or washing water to a membrane separation apparatus having a separation membrane containing a trihalomethane precursor. It is a suppression method.

The present invention provides a bromine-based oxidant or a reaction product of a bromine compound and a chlorine-based oxidant, a sulfamic acid compound, in a feed water or a wash water containing a trihalomethane precursor and having a separation membrane. Is a method for suppressing slime in a separation membrane.

The present invention provides a bromine-based oxidant or a reaction product of a bromine compound and a chlorine-based oxidant, a sulfamic acid compound, in a feed water or a wash water containing a trihalomethane precursor and having a separation membrane. This is a method for suppressing slime of a separation membrane in which the reaction product of the present is present.

The present invention relates to a separation in which a mixture of bromine and a sulfamic acid compound or a reaction product of bromine and a sulfamic acid compound is present in feed water or washing water to a membrane separation apparatus having a separation membrane containing a trihalomethane precursor. This is a method for suppressing the slime of a film.

In the method for suppressing slime of the separation membrane, the reaction product of bromine and a sulfamic acid compound includes a step of reacting a mixed liquid containing water, an alkali and a sulfamic acid compound by adding bromine in an inert gas atmosphere. It is preferable that it is obtained by the method.

In the method for suppressing slime of the separation membrane, it is preferable that the concentration of the trihalomethane precursor in the feed water or the washing water is 0.001 mg / L or more as a trihalomethane generating ability.

In the method for suppressing slime of the separation membrane, the separation membrane is preferably a polyamide polymer membrane.

In the method for suppressing slime of the separation membrane, the trihalomethane precursor preferably contains humic substances.

In the method for suppressing slime of the separation membrane, it is preferable that the water supply or washing water further contains bromide ions.

In the method for suppressing slime of the separation membrane, it is preferable that the concentration of bromide ions in the feed water or the wash water is 5 mg / L or more.

In the method for suppressing slime of the separation membrane, the membrane separation device provided with the separation membrane is a membrane separation device that is operated and stopped, and during the suspension of operation of the membrane separation device,
The presence of the bromine-based oxidant or a reaction product of a bromine compound and a chlorine-based oxidant;
The bromine-based oxidant or a reaction product of a bromine compound and a chlorine-based oxidant and a sulfamic acid compound are present;
The brominated oxidant, or the reaction product of a bromine compound and a chlorinated oxidant and the reaction product of a sulfamic acid compound, or
The presence of a reaction product of the bromine with a sulfamic acid compound;
This is a method for suppressing slime of a separation membrane.

In the method for suppressing slime of the separation membrane, it is preferable that the pH of water existing in the membrane separation device is pH 5.5 or more.

In the method for suppressing slime of the separation membrane, the water present in the membrane separation device is preferably at least one of seawater and brine.

In the present invention, a bromine-based oxidant or a reaction product of a bromine compound and a chlorine-based oxidant is present in feed water or washing water to a membrane separation apparatus including a separation membrane containing a trihalomethane precursor; A oxidant, or a reaction product of a bromine compound and a chlorine oxidant, and a sulfamic acid compound; a bromine-based oxidant, or a reaction product of a bromine compound and a chlorine-based oxidant, and a sulfamic acid compound The presence of a reaction product of bromine and a sulfamic acid compound; or the presence of a reaction product of bromine and a sulfamic acid compound has a sufficient slime-inhibiting effect. However, the trihalomethane content in the permeated water can be reduced.

It is a schematic structure figure showing an example of a membrane separation system concerning an embodiment of the present invention. In Example 4, 5 and Comparative Example 2, it is a figure which shows the total trihalomethane density | concentration (mg / L) in the treated water with respect to the bromide ion density | concentration (mg / L) in to-be-treated water.

Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

<Method for suppressing slime of separation membrane>
In the method for suppressing slime of a separation membrane according to an embodiment of the present invention, a “bromine-based oxidant” is present as a slime inhibitor in feed water or wash water containing a trihalomethane precursor and supplied to a membrane separation apparatus having a separation membrane. A method, or a method in which a “reaction product of a bromine compound and a chlorine-based oxidizing agent” such as hypobromous acid is present.

The method for suppressing slime of a separation membrane according to an embodiment of the present invention includes a “bromine-based oxidant” and a “sulfamine” as slime inhibitors in feed water or washing water to a membrane separation apparatus including a separation membrane containing a trihalomethane precursor. Acid compound ”or“ reaction product of bromine compound and chlorinated oxidant ”and“ sulfamic acid compound ”. Thereby, it is thought that a hypobromite stabilization composition produces | generates in feed water or washing water.

In addition, the slime suppression method for a separation membrane according to an embodiment of the present invention includes a bromine-based oxidizing agent and a sulfamine as a slime inhibitor in feed water or washing water containing a trihalomethane precursor and having a separation membrane. A method of allowing a hypobromite stabilizing composition to be a "reaction product with an acid compound" or a "reaction product of a reaction product of a bromine compound with a chlorine-based oxidant and a sulfamic acid compound" This is a method in which a hypobromite stabilizing composition is present.

Specifically, the method for suppressing slime of a separation membrane according to an embodiment of the present invention includes, for example, “bromine”, “bromine chloride” in feed water or washing water to a membrane separation device including a trihalomethane precursor and including a separation membrane. ”,“ Hypobromite ”or“ reaction product of sodium bromide and hypochlorous acid ”.

A method for suppressing slime of a separation membrane according to an embodiment of the present invention includes, for example, “bromine”, “bromine chloride”, “next” in feed water or washing water to a membrane separation device including a trihalomethane precursor and including a separation membrane. This is a method in which "bromous acid" or "reaction product of sodium bromide and hypochlorous acid" and "sulfamic acid compound" are present.

In addition, the method for suppressing slime of a separation membrane according to an embodiment of the present invention includes, for example, “reaction of bromine with a sulfamic acid compound” in feed water or washing water containing a trihalomethane precursor to a membrane separation device including a separation membrane. Hypobromite, which is "product", "reaction product of bromine chloride and sulfamic acid compound", or "reaction product of sodium bromide and hypochlorous acid and sulfamic acid compound" A method of presenting a stabilizing composition. In addition, it is not clear what kind of compound is generated as “reaction product of bromine and sulfamic acid compound”, but “bromosulfamic acid” which is a hypobromite stabilizing compound is generated. Conceivable.

By these methods, it is possible to reduce the trihalomethane content in the permeated water while suppressing the generation of slime in the separation membrane in the membrane separation apparatus using feed water or washing water containing a trihalomethane precursor. Moreover, membrane contamination by microorganisms can be reliably suppressed without substantially degrading the performance of the separation membrane. By the slime suppression method of the separation membrane according to the present embodiment, slime suppression treatment can be performed while having a high slime suppression effect while minimizing the influence on membrane performance and downstream water quality.

Bromine-based oxidants and hypobromite stabilization compositions, like chlorine-based oxidants, react with trihalomethane precursors to produce trihalomethanes, but are produced by bromine-based oxidants and hypobromite stabilization compositions. The brominated trihalomethanes such as bromoform are the main trihalomethanes, and are more easily removed by the separation membrane than the chloroform-based trihalomethanes such as chloroform produced by the chlorinated oxidant, and the trihalomethane in the permeated water of the separation membrane is greatly reduced. It is thought. The reason for the high removal rate of brominated trihalomethanes in the separation membrane is unknown, but it is presumed that brominated trihalomethanes have a relatively large molecular weight compared to chlorinated trihalomethanes.

Thus, the slime suppression method of the separation membrane according to the present embodiment, despite exhibiting a slime suppression effect equal to or higher than that of a chlorine-based oxidizing agent such as hypochlorous acid, compared with a chlorine-based oxidizing agent, Since the elimination rate of the brominated trihalomethane produced in the separation membrane is extremely high, the trihalomethane in the permeated water of the separation membrane can be greatly reduced. For this reason, the slime inhibitor used with the slime suppression method of the separation membrane which concerns on this embodiment is suitable as a slime inhibitor for separation membranes.

Among the slime suppression methods of the separation membrane according to the present embodiment, a method in which “bromine-based oxidant” and “sulfamic acid compound” are present, “reaction product of bromine compound and chlorine-based oxidant”, and “sulfamic acid compound” ”, A method in which“ a reaction product of a bromine-based oxidant and a sulfamic acid compound ”is present, or“ a reaction product of a reaction product of a bromine compound and a chlorinated oxidant and a sulfamic acid compound ” The method in which the “product” is present has an extremely low deterioration effect on the separation membrane, and can be directly introduced into the separation membrane to suppress slime. For this reason, the slime inhibitor used by these slime suppression methods is more suitable as a slime inhibitor for separation membranes.

Among the slime suppression methods of the separation membrane according to the present embodiment, when “bromine-based oxidant” or “reaction product of bromine compound and chlorine-based oxidant” is bromine, there is no chlorine-based oxidant. Moreover, the production amount of chlorine-based trihalomethanes having a low rejection rate in the separation membrane is also low, which is more suitable as a slime inhibitor for separation membranes. When a chlorinated oxidant is included, there is a concern about the production of chloric acid.

Trihalomethane refers to one in which three hydrogen atoms of methane are substituted with halogen, and examples thereof include chloroform, bromodichloromethane, dibromochloromethane, and bromoform. The trihalomethane precursor is not particularly limited as long as it is a substance that becomes a precursor of trihalomethane, and examples thereof include a compound having a 1,3-diketone structure and a compound having a 1,3-dihydroxybenzene structure. Specific examples of the trihalomethane precursor include humic substances including humic acid and fulvic acid. Here, the humic substance (humic substance) is an organic component formed by huming the parts of the plant such as leaves and stems. Called fulvic acid.

The trihalomethane precursor can be measured as a trihalomethane production ability (THMFP) (mg / L) by a measurement method based on “a special method for the maintenance of water quality in a tap water source area for prevention of specific water use damage”. Specifically, the sample was produced under the conditions of pH 7.0, temperature 20 ° C., reaction time 24 hours, and sodium hypochlorite added so that the free residual chlorine concentration after 24 hours was 1 to 2 mg / L. In this method, the amount of trihalomethane produced is determined by simultaneous analysis using a purge / trap / gas chromatograph / mass spectrometer. The trihalomethane precursor can also be measured with a TOC meter or the like.

When the trihalomethane precursor is present at 0.001 mg / L or more as the trihalomethane precursor (THMFP) (mg / L), trihalomethane is likely to be generated. When the concentration is L or more, preferably 0.01 mg / L or more, and more preferably 0.02 mg / L or more, the method for suppressing slime of the separation membrane according to this embodiment is more effective. Although there is no restriction | limiting in particular in the upper limit of the trihalomethane production ability of the feed water or washing water to a membrane separator, For example, it is 1 mg / L or less.

Further, since trihalomethane is easily generated when the trihalomethane precursor is present in a TOC of 0.5 mg / L or more, the TOC of water supplied to the membrane separation device or washing water is 0.5 mg / L or more, preferably 5.0 mg / L or more. More preferably, when it is 10.0 mg / L or more, the method for suppressing slime of the separation membrane according to the present embodiment is more effective. Although there is no restriction | limiting in particular in the upper limit of the TOC of the water supply or washing water to a membrane separator, For example, it is 500 mg / L or less. In addition, when measured in the Example mentioned later, trihalomethane production | generation ability 0.01 mg / L is corresponded to TOC5.0 mg / L.

In particular, when the trihalomethane precursor contains humic acid, trihalomethane is easily generated when humic acid is present in an amount of 0.89 mg / L or more. The slime suppression method for a separation membrane according to the present embodiment is more effective when it is preferably 8.9 mg / L or more, more preferably 890 mg / L or more. Although there is no restriction | limiting in particular in the upper limit of the humic acid of the feed water or washing water to a membrane separator, For example, it is 180 mg / L or less. In addition, when measured in the below-mentioned Example, the trihalomethane production | generation ability 0.01 mg / L is equivalent to 8.9 mg / L humic acid.

In the method for suppressing the slime of the separation membrane according to the present embodiment, when the water supply or the washing water to the membrane separation apparatus provided with the separation membrane further contains bromide ions, the effect is more exhibited. According to the slime suppression method for a separation membrane according to the present embodiment, in a membrane separation apparatus using feed water or washing water containing a trihalomethane precursor and bromide ions, the trihalomethane in the permeated water has a sufficient slime suppression effect. The content can be reduced.

As described above, when a chlorine-based oxidizing agent such as hypochlorous acid is added to water containing a trihalomethane precursor, trihalomethane such as chloroform is produced, but bromide ions are contained in water like seawater (for example, 5 mg / L or more) and containing a trihalomethane precursor such as humic substance, when hypochlorous acid is added as a slime inhibitor, bromine-based trihalomethane is mainly produced. Bromine-based trihalomethane has a higher molecular weight than chlorine-based trihalomethane, so the total trihalomethane concentration is high.

Slime inhibitors such as “hypobromite” and “hypobromite stabilizing composition in which bromine-based oxidant and sulfamic acid coexist” used in the method for suppressing slime of a separation membrane according to an embodiment of the present invention are Slime suppression effect (bactericidal effect) equivalent to or better than hypochlorous acid. When trihalomethane precursors and bromide ions are present in the system, bromine trihalomethane is mainly produced. However, these “hypobromite” and “hypobromite stabilization composition”, unlike ordinary hypochlorous acid, hardly increases the amount of trihalomethane generated with increasing bromide ion concentration. . For this reason, in the method for suppressing slime of the separation membrane according to this embodiment using a slime inhibitor such as “hypobromite” or “hypobromite stabilizing composition in which bromine-based oxidizing agent and sulfamic acid coexist”. Therefore, it is considered that the concentration of trihalomethane produced is lower in water containing bromide ions than in the case of using hypochlorous acid.

On the other hand, although "stabilized hypochlorous acid" such as chlorosulfamic acid is stabilized, trihalomethane formation ability is suppressed, but "hypobromous acid" and "hypobromite stabilization composition Compared with “,” the sterilizing power is low, and a sufficient slime suppressing effect cannot be obtained.

When the slime inhibitor used in the slime suppression method of the separation membrane according to the present embodiment exhibits a slime suppression effect equal to or higher than hypochlorous acid, but contains bromide ions in the water to be treated, Compared to hypochlorous acid, the amount of trihalomethane produced thereby is small. For this reason, the slime suppression method for a separation membrane according to this embodiment is suitable as a slime suppression method for a membrane separation device using feed water or washing water containing a trihalomethane precursor and bromide ions.

As described above, the slime suppression method for a separation membrane according to the present embodiment enables a slime suppression treatment that minimizes the trihalomethane concentration in the permeated water of the separation membrane while having a high slime suppression effect.

In particular, if bromide ions are present in the feed water or washing water to the membrane separation device in an amount of 5 mg / L or more, trichloromethane is likely to be generated in the case of hypochlorous acid, so the concentration of bromide ions in the feed water or washing water to the membrane separation device is When the concentration is 5 mg / L or more, preferably 18 mg / L or more, the slime suppression method for a separation membrane according to this embodiment is more effective. Although there is no restriction | limiting in particular in the upper limit of the bromide ion density | concentration of the feed water or washing water to a membrane separator, For example, it is 1000 mg / L or less.

In the method for suppressing slime of the separation membrane according to the present embodiment, for example, “bromine-based oxidant” or “bromine compound and chlorine” is fed into the feed water or the wash water to the membrane separator using the feed water or the wash water containing the trihalomethane precursor. What is necessary is just to inject | pour a reaction material with a type | system | group oxidizing agent with a chemical injection pump. The “bromine compound” and the “chlorine oxidant” may be added separately to the aqueous system, or may be added to the aqueous system after being mixed with the stock solution.

For example, in a feed water or a wash water to a membrane separation apparatus using a feed water or a wash water containing a trihalomethane precursor, a “bromine oxidant” or a “reaction product of a bromine compound and a chlorine oxidizer” and “sulfamic acid” The “compound” may be injected by a chemical injection pump or the like. The “bromine-based oxidant” or “reaction product of bromine compound and chlorine-based oxidant” and the “sulfamic acid compound” may be added separately to the aqueous system, or they are mixed together in the stock solution and then into the aqueous system. It may be added.

Further, for example, in a feed water or a wash water to a membrane separation device using a feed water or a wash water containing a trihalomethane precursor, a “reaction product of a bromine-based oxidant and a sulfamic acid compound” or “a bromine compound and a chlorine-based water” You may inject | pour the reaction product with an oxidizing agent, and a sulfamic acid compound with a chemical injection pump.

The above-mentioned slime inhibitor added to the water supplied to the membrane separator or the washing water may be decomposed by a reducing agent or the like immediately before the separation membrane.

The separation membrane slime suppression method according to the present embodiment can suppress the deterioration of the separation membrane and effectively sterilize the separation membrane during the operation suspension even in the membrane separation system that operates and halts the operation. It becomes.

<Membrane separation system>
An outline of an example of a membrane separation system according to an embodiment of the present invention is shown in FIG. The membrane separation system 1 includes a raw water tank 10 and a membrane separation device 12.

In the membrane separation system 1 of FIG. 1, a raw water pipe 16 is connected to the inlet of the raw water tank 10. The outlet of the raw water tank 10 and the inlet of the membrane separation device 12 are connected by a raw water supply pipe 18 via a pump 14. A permeated water pipe 20 is connected to the permeated water outlet of the membrane separator 12, and a concentrated water pipe 22 is connected to the concentrated water outlet. A sterilizing agent supply pipe 24 is connected between the pump 14 in the raw water supply pipe 18 and the inlet of the membrane separation device 12.

The operation of the membrane separation system 1 according to this embodiment and the method for sterilizing the separation membrane will be described.

The raw water to be treated is stored in the raw water tank 10 as necessary, and then supplied to the membrane separation device 12 through the raw water supply pipe 18 by the pump 14. In the membrane separation apparatus 12, membrane separation processing is performed by the separation membrane (membrane separation processing step). The permeated water (treated water) obtained by the membrane separation treatment is discharged through the permeated water pipe 20, and the concentrated water is discharged through the concentrated water pipe 22. The concentrated water may be circulated to the raw water tank 10 or the raw water supply pipe 18.

For example, a disinfectant supply mechanism is installed between the pump 14 in the raw water supply pipe 18 and the inlet of the membrane separator 12, and the raw water in the raw water tank 10 is passed through the membrane separator 12 and the disinfectant is added to the raw water. A sterilizing agent having a predetermined concentration is added through the sterilizing agent supply pipe 24 from the adding mechanism. When the operation of the membrane separation system 1 is stopped, the pump 14 is stopped, and the disinfectant is present in the membrane separation device 12 while the operation of the membrane separation system 1 is stopped. The disinfectant supply mechanism may be installed in the raw water supply pipe 18 or the raw water tank 10.

In addition, the raw water in the raw water tank 10 is passed through the membrane separator 12 and a predetermined concentration of bactericide is added to the raw water through the bactericide supply pipe 24 from the bactericide supply mechanism, and the operation of the membrane separation system 1 is performed. In the case of stopping, after adding a predetermined concentration of bactericide from the bactericide addition mechanism 24 to the raw water through the bactericide supply pipe 24, the pump 14 is stopped and the bactericide is stopped during the operation of the membrane separation system 1. May be present in the membrane separation device 12.

Here, “operation stop” means that the membrane separation system 1 has not obtained treated water (permeated water).

In addition, when backwashing the membrane separation device 12 using backwashing water or using permeated water as backwashing water, a bactericidal agent is added to the backwashing water, and the membrane separation system 1 is not in operation. In addition, a disinfectant may be present in the membrane separation device 12.

In the membrane separation system 1, a level switch is installed in the raw water tank 10, the operation is stopped when the water level in the raw water tank 10 detected by the level switch during operation is lower than a predetermined height, and the level switch is detected during the operation stop. Control may be performed so that the operation is resumed when the water level in the raw water tank 10 becomes higher than a predetermined height.

In the method for suppressing slime of the separation membrane according to the present embodiment, “bromine-based oxidizing agent” and “sulfamic acid compound” are used as disinfectants (slime suppressing agents) during the operation stop of the membrane separation system 1 in which the operation and the operation stop are performed. Is present in the membrane separation device 12 or “reaction product of bromine compound and chlorine-based oxidant” and “sulfamic acid compound” are present in the membrane separation device 12. Thereby, it is thought that a hypobromite stabilization composition produces | generates in disinfectant containing backwash water or disinfectant containing water.

Moreover, the slime suppression method of the separation membrane which concerns on this embodiment is a "bromine-type oxidizing agent and a sulfamic acid compound as a disinfectant (slime inhibitor) during the operation stop of the membrane separation system 1 in which an operation | movement and an operation stop are performed. Or a reaction product of a reaction product of a bromine compound and a chlorinated oxidant and a sulfamic acid compound. This is a method in which the hypobromite stabilizing composition, which is a product, is present in the membrane separation device 12.

Specifically, the method for suppressing the slime of the separation membrane according to the present embodiment includes, for example, “bromine”, “bromine chloride”, “hypobromine” during the operation stop of the membrane separation system 1 in which the operation and the operation stop are performed. In this method, the “acid” or “reaction product of sodium bromide and hypochlorous acid” and the “sulfamic acid compound” are present in the membrane separator 12.

In addition, the method for suppressing slime of the separation membrane according to the present embodiment can be performed during, for example, “reaction product of bromine and sulfamic acid compound”, “salt chloride” during the operation stop of the membrane separation system 1 in which the operation and the operation stop are performed. The reaction product of bromine and sulfamic acid compound ", or the reaction product of sodium bromide and hypochlorous acid and the reaction product of sulfamic acid compound" hypobromite stabilization composition This is a method of existing in the separation device 12.

By these methods, in the membrane separation system 1 that performs operation and operation suspension, it is possible to suppress the deterioration of the separation membrane of the membrane separation device 12 and effectively sterilize the separation membrane during operation suspension. Moreover, there is no need for complicated additional equipment for supplying the bactericide periodically, and the system is simplified.

In the method for suppressing slime of the separation membrane according to the present embodiment, for example, during the operation stop of the membrane separation system 1 in which the operation and the operation stop are performed, “bromine-based oxidant” or “bromine compound and chlorine-based oxidant”. The “reactant” and the “sulfamic acid compound” may be injected into the aqueous system by a chemical injection pump or the like. The “bromine-based oxidant” or “reaction product of bromine compound and chlorine-based oxidant” and the “sulfamic acid compound” may be added separately to the aqueous system, or they are mixed together in the stock solution and then into the aqueous system. It may be added.

Further, for example, during the operation stop of the membrane separation system 1 in which the operation and the operation stop are performed, “reaction product of bromine-based oxidant and sulfamic acid compound” or “reaction of bromine compound and chlorine-based oxidant” The reaction product of the product and the sulfamic acid compound ”may be injected into the aqueous system by a chemical injection pump or the like.

In the slime suppression method for a separation membrane according to the present embodiment, the ratio of the equivalent of “sulfamic acid compound” to the equivalent of “bromine-based oxidant” or “reaction product of bromine compound and chlorine-based oxidant” is 1 or more. It is preferable that it is in the range of 1 or more and 2 or less. If the ratio of the equivalent of “sulfamic acid compound” to the equivalent of “bromine-based oxidant” or “reaction product of bromine compound and chlorine-based oxidant” is less than 1, the film may be deteriorated. When it exceeds, manufacturing cost may increase.

The effective halogen concentration in contact with the separation membrane is preferably 0.01 to 100 mg / L in terms of effective chlorine concentration. If it is less than 0.01 mg / L, a sufficient slime-inhibiting effect may not be obtained. If it is more than 100 mg / L, it may cause deterioration of the separation membrane and corrosion of piping.

Examples of bromine-based oxidizing agents include bromine (liquid bromine), bromine chloride, bromic acid, bromate, and hypobromite.

Among these, the preparation of “bromine and sulfamic acid compound (mixture of bromine and sulfamic acid compound)” or “reaction product of bromine and sulfamic acid compound” using bromine is composed of “hypochlorous acid and bromine compound and Compared to sulfamic acid preparations and bromine chloride and sulfamic acid preparations, the amount of trihalomethane produced is small, and the reverse osmosis membrane (RO membrane) does not deteriorate further, and the reverse osmosis membrane (RO membrane) permeates. Since the amount of effective halogen leaked into membrane permeated water such as water is smaller, it is more preferable as a slime inhibitor for separation membranes such as reverse osmosis membranes (RO membranes).

That is, in the method for suppressing slime of a separation membrane according to an embodiment of the present invention, bromine and a sulfamic acid compound are present in feed water or washing water to a membrane separation apparatus including a separation membrane, which contains a trihalomethane precursor ( Preferably, a mixture of bromine and a sulfamic acid compound is present). In addition, it is preferable that a reaction product of bromine and a sulfamic acid compound is present in the feed water or the washing water containing a trihalomethane precursor and supplied to a membrane separation apparatus including a separation membrane.

Examples of bromine compounds include sodium bromide, potassium bromide, lithium bromide, ammonium bromide and hydrobromic acid. Of these, sodium bromide is preferable from the viewpoint of formulation cost and the like.

Examples of the chlorine-based oxidizing agent include chlorine gas, chlorine dioxide, hypochlorous acid or a salt thereof, chlorous acid or a salt thereof, chloric acid or a salt thereof, perchloric acid or a salt thereof, chlorinated isocyanuric acid or a salt thereof. Etc. Among these, examples of the salt include alkali metal hypochlorites such as sodium hypochlorite and potassium hypochlorite, alkaline earth hypochlorite such as calcium hypochlorite and barium hypochlorite. Metal salts, alkali metal chlorites such as sodium chlorite and potassium chlorite, alkaline earth metal chlorites such as barium chlorite, and other metal chlorites such as nickel chlorite , Alkali metal chlorates such as ammonium chlorate, sodium chlorate and potassium chlorate, and alkaline earth metal chlorates such as calcium chlorate and barium chlorate. These chlorine-based oxidants may be used alone or in combination of two or more. As the chlorine-based oxidant, sodium hypochlorite is preferably used from the viewpoint of handleability.

The sulfamic acid compound is a compound represented by the following general formula (1).
R ₂ NSO ₃ H (1)
(In the formula, R is independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.)

Examples of the sulfamic acid compound include sulfamic acid (amidosulfuric acid) in which both two R groups are hydrogen atoms, N-methylsulfamic acid, N-ethylsulfamic acid, N-propylsulfamic acid, N- A sulfamic acid compound in which one of two R groups such as isopropylsulfamic acid and N-butylsulfamic acid is a hydrogen atom and the other is an alkyl group having 1 to 8 carbon atoms, N, N-dimethylsulfamic acid, N, Two R groups such as N-diethylsulfamic acid, N, N-dipropylsulfamic acid, N, N-dibutylsulfamic acid, N-methyl-N-ethylsulfamic acid, N-methyl-N-propylsulfamic acid, etc. One of two R groups such as a sulfamic acid compound, N-phenylsulfamic acid and the like, both of which are alkyl groups having 1 to 8 carbon atoms Is a hydrogen atom and the other sulfamic acid compound or a salt thereof, such as an aryl group having 6 to 10 carbon atoms. Examples of the sulfamate include alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as calcium salt, strontium salt and barium salt, manganese salt, copper salt, zinc salt, iron salt, cobalt salt, Other metal salts such as nickel salts, ammonium salts, guanidine salts and the like can be mentioned. The sulfamic acid compounds and salts thereof may be used alone or in combination of two or more. As the sulfamic acid compound, sulfamic acid (amidosulfuric acid) is preferably used from the viewpoint of environmental load.

In the method for suppressing slime of the separation membrane according to this embodiment, an alkali may be further present. Examples of the alkali include alkali hydroxides such as sodium hydroxide and potassium hydroxide. From the viewpoint of product stability at low temperatures, sodium hydroxide and potassium hydroxide may be used in combination. Further, the alkali is not solid and may be used as an aqueous solution.

Examples of the separation membrane include a reverse osmosis membrane (RO membrane), a nanofiltration membrane (NF membrane), a microfiltration membrane (MF membrane), and an ultrafiltration membrane (UF membrane). Among these, the method for suppressing slime of the separation membrane according to the embodiment of the present invention can be suitably applied particularly to a reverse osmosis membrane (RO membrane). Moreover, the slime suppression method of the separation membrane which concerns on embodiment of this invention is suitably applicable to the polyamide-type polymer membrane which is mainstream these days as a reverse osmosis membrane. Polyamide polymer membranes have a relatively low resistance to oxidizing agents, and when free chlorine or the like is continuously brought into contact with the polyamide polymer membrane, the membrane performance is significantly reduced. However, in the method for suppressing slime of the separation membrane according to the present embodiment, such a remarkable decrease in membrane performance hardly occurs even in the polyamide polymer membrane.

In the separation membrane slime suppression method according to the present embodiment, when the membrane separation device is a RO device including a reverse osmosis membrane (RO membrane) as a separation membrane, the pH of water supplied to the RO device may be 5.5 or more. Preferably, it is 6.0 or more, more preferably 6.5 or more. If the pH of the feed water to the RO device is less than 5.5, the amount of permeated water may decrease. Further, the upper limit value of the pH of water supplied to the RO device is not particularly limited as long as it is equal to or lower than the upper limit pH (for example, pH 10) of a normal reverse osmosis membrane (RO membrane), but the scale of hardness components such as calcium. Considering the precipitation, it is preferable to operate at a pH of, for example, 9.0 or less. When using the slime suppression method of the separation membrane according to the present embodiment, the reverse osmosis membrane (RO membrane) is deteriorated and treated water (permeated water) is deteriorated by operating at a pH of 5.5 or higher for the water supplied to the RO device. It is possible to secure a sufficient amount of permeated water while suppressing deterioration of water quality and exhibiting a sufficient slime suppressing effect.

In the RO device, when scale is generated at pH 5.5 or higher of the feed water to the RO device, a dispersant may be used in combination with a bromine-based oxidizing agent or a hypobromite stabilizing composition for scale control. . Examples of the dispersant include polyacrylic acid, polymaleic acid, and phosphonic acid. The amount of the dispersant added to the feed water is, for example, in the range of 0.1 to 1,000 mg / L as the concentration in the RO concentrated water.

Further, in order to suppress the generation of scale without using a dispersant, for example, an RO device is used so that the silica concentration in the RO concentrated water is less than the solubility and the Langeria index, which is a calcium scale index, is less than 0. Adjusting the operating conditions such as the recovery rate.

Examples of the use of the RO device include seawater desalination and wastewater recovery.

<Slime inhibitor composition for separation membrane>
The slime inhibitor composition for separation membrane according to the present embodiment contains “bromine-based oxidant” or “reaction product of bromine compound and chlorine-based oxidant” and “sulfamic acid compound”, Furthermore, you may contain an alkali.

Further, the slime inhibitor composition for separation membrane according to the present embodiment includes a “reaction product of a bromine-based oxidant and a sulfamic acid compound” or a “reaction product of a bromine compound and a chlorine-based oxidant, and a sulfamic acid. It contains a reaction product of a compound and may further contain an alkali.

The bromine-based oxidizing agent, bromine compound, chlorine-based oxidizing agent, and sulfamic acid compound are as described above.

As the slime inhibitor composition for separation membrane according to this embodiment, the reverse osmosis membrane (RO membrane) or the like is not further deteriorated, and the amount of effective halogen leaked into membrane permeated water such as RO permeated water is smaller. Containing bromine and a sulfamic acid compound (containing a mixture of bromine and sulfamic acid compound), for example, a mixture of bromine, sulfamic acid compound, alkali and water, or reaction of bromine with sulfamic acid compound A product containing a product, for example, a mixture of a reaction product of bromine and a sulfamic acid compound, an alkali, and water is preferable.

The slime inhibitor composition for a separation membrane according to the present embodiment has a high oxidizing power, slime inhibitory power, and slime peeling power, which is remarkably high compared to a combined chlorine-based slime inhibitor such as chlorosulfamic acid. Similarly, it hardly causes significant film deterioration like hypochlorous acid having high oxidizing power. At normal use concentrations, the effect on film degradation can be substantially ignored. Therefore, it is optimal as a slime inhibitor for separation membranes such as reverse osmosis membranes (RO membranes).

Unlike the hypochlorous acid, the slime inhibitor composition for separation membrane according to the present embodiment hardly permeates the reverse osmosis membrane (RO membrane), and therefore has little influence on the quality of treated water. Further, since the concentration can be measured on site in the same manner as hypochlorous acid or the like, more accurate concentration management is possible. In addition, the slime inhibitor composition for separation membrane according to the present embodiment reacts with the trihalomethane precursor to produce bromine-based trihalomethane, but is easily eliminated by the separation membrane, and the trihalomethane in the permeated water of the separation membrane is greatly reduced. It is thought that it is done.

The pH of the composition is, for example, more than 13.0, more preferably more than 13.2. When the pH of the composition is 13.0 or less, the effective halogen in the composition may become unstable.

The bromic acid concentration in the slime inhibitor composition for separation membrane is preferably less than 5 mg / kg. If the bromate concentration in the slime inhibitor composition for separation membrane is 5 mg / kg or more, the concentration of bromate ions in the permeated water may increase.

<Method for Producing Slime Inhibitor Composition for Separation Membrane>
The slime inhibitor composition for a separation membrane according to the present embodiment is a mixture of a bromine-based oxidant and a sulfamic acid compound, or a reaction product of a bromine compound and a chlorine-based oxidant, and a sulfamic acid compound. And may be further mixed with an alkali.

As a method for producing a slime inhibitor composition for a separation membrane containing bromine and a sulfamic acid compound, or a slime inhibitor composition for a separation membrane containing a reaction product of bromine and a sulfamic acid compound, water, A step of adding bromine to a mixture liquid containing an alkali and a sulfamic acid compound in an inert gas atmosphere to react, or a step of adding bromine to a liquid mixture containing water, an alkali and a sulfamic acid compound in an inert gas atmosphere It is preferable to contain. By adding and reacting under an inert gas atmosphere, or adding under an inert gas atmosphere, the bromate ion concentration in the composition is lowered, and the bromate ion concentration in the permeated water such as RO permeated water is reduced. Lower.

Although the inert gas to be used is not limited, at least one of nitrogen and argon is preferable from the viewpoint of production and the like, and nitrogen is particularly preferable from the viewpoint of manufacturing cost and the like.

The oxygen concentration in the reactor during the addition of bromine is preferably 6% or less, more preferably 4% or less, further preferably 2% or less, and particularly preferably 1% or less. If the oxygen concentration in the reactor during the bromine reaction exceeds 6%, the amount of bromic acid produced in the reaction system may increase.

The addition ratio of bromine is preferably 25% by weight or less, more preferably 1% by weight or more and 20% by weight or less based on the total amount of the composition. If the bromine addition rate exceeds 25% by weight relative to the total amount of the composition, the amount of bromic acid produced in the reaction system may increase. If it is less than 1% by weight, the sterilizing power may be inferior.

The reaction temperature at the time of bromine addition is preferably controlled in the range of 0 ° C. to 25 ° C., but more preferably in the range of 0 ° C. to 15 ° C. from the viewpoint of production cost. When the reaction temperature at the time of bromine addition exceeds 25 degreeC, the production amount of the bromic acid in a reaction system may increase, and when it is less than 0 degreeC, it may freeze.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

When a hypobromite stabilizing composition which is a “reaction product of bromine-based oxidant and sulfamic acid compound” is used as a slime inhibitor (Example 1), “reaction between bromine compound and chlorine-based oxidant” When a hypobromite stabilizing composition which is a reaction product of a product and a sulfamic acid compound is used (Example 2), a case where a “bromine-based oxidant” is used (Example 3), Comparison was made with respect to trihalomethane concentration in the permeated water and reverse osmosis membrane (RO membrane) performance when hypochlorous acid, which is a general slime inhibitor, was used (Comparative Example 1).

[Preparation of Composition 1]
Under nitrogen atmosphere, liquid bromine: 16.9% by weight (wt%), sulfamic acid: 10.7% by weight, sodium hydroxide: 12.9% by weight, potassium hydroxide: 3.94% by weight, water: remaining Minutes were mixed to prepare composition 1. The pH of Composition 1 was 14, and the effective halogen concentration (effective chlorine equivalent concentration) was 7.5% by weight. The detailed preparation method of the composition 1 is as follows.

Add 1436 g of water and 361 g of sodium hydroxide to a 2 L four-necked flask sealed by continuous injection while controlling the flow rate of nitrogen gas with a mass flow controller so that the oxygen concentration in the reaction vessel is maintained at 1%. Next, after adding 300 g of sulfamic acid and mixing, 473 g of liquid bromine was added while maintaining cooling so that the temperature of the reaction solution was 0 to 15 ° C., and 230 g of 48% potassium hydroxide solution was added. The target composition 1 was obtained, in which the sulfamic acid was 10.7% by weight relative to the total amount of the composition, 16.9% bromine, and the equivalent ratio of sulfamic acid to the equivalent of bromine was 1.04. The pH of the resulting solution was 14 as measured by the glass electrode method. The bromine content of the resulting solution was 16.9% as measured by a redox titration method using sodium thiosulfate after bromine was converted to iodine with potassium iodide, and the theoretical content (16.9% ) Of 100.0%. The oxygen concentration in the reaction vessel during the bromine reaction was measured using “Oxygen Monitor JKO-02 LJDII” manufactured by Zico Corporation. The bromic acid concentration was less than 5 mg / kg.

[Preparation of Composition 2]
Sodium bromide: 11% by weight, 12% sodium hypochlorite aqueous solution: 50% by weight, sodium sulfamate: 14% by weight, sodium hydroxide: 8% by weight, water: the residue was mixed to prepare composition 2. Prepared. The pH of Composition 2 was 14, and the effective halogen concentration (effective chlorine equivalent concentration) was 6% by weight. The detailed preparation method of the composition 2 is as follows.

17 g of water was put into a reaction vessel, 11 g of sodium bromide was added and dissolved by stirring, 50 g of 12% aqueous sodium hypochlorite solution was added and mixed, and then 14 g of sodium sulfamate was added and stirred. After dissolution, 8 g of sodium hydroxide was added, stirred and dissolved to obtain the desired composition 2.

In addition, according to the method stipulated in the sodium hypochlorite standard for water supply (JWWA K 120 2008), the content of chloric acid in the composition was determined to be composition 2 (1100 mg / kg). ) Less than composition 1 (less than 50 mg / kg).

[Composition 3]
A 9% by weight aqueous sodium hypobromite solution (Kanto Chemical Co., Ltd., Deer Grade 1) was used as Composition 3.

[Composition 4]
A 12 wt% aqueous sodium hypochlorite solution was used as Composition 4.

<Examples 1 to 3, Comparative Example 1, Reference Examples 1 and 2>
Under the following conditions, compositions 1 to 4 were added to the raw water of the reverse osmosis membrane device, respectively, and the total trihalomethane concentration in the separation membrane feed water and the separation membrane permeated water, the total trihalomethane in the reverse osmosis membrane (RO membrane) Exclusion rates were compared. As raw water, the following simulated water was used in Examples 1 to 3 and Comparative Example 1, and pure water was used in Reference Examples 1 and 2.

(Test conditions)
Test apparatus: Flat membrane test apparatus Separation membrane: Polyamide polymer reverse osmosis membrane ES15 manufactured by Nitto Denko Corporation
・ Operating pressure: 0.75 MPa
・ Raw water: Simulated water with trihalomethane production ability of 0.01 mg / L (pure water added with 8.9 mg / L humic acid (manufactured by Wako Pure Chemical Industries) as a trihalomethane precursor, TOC: 5 mg / L) or pure Water / drug: Compositions 1 to 4 are added so that the effective halogen concentration (effective chlorine equivalent concentration) is 3 mg / L. Raw water pH: The pH of the test water is adjusted to 8 after the drug is added. : 25 ° C
・ Method for measuring trihalomethane production ability: Under conditions where sodium hypochlorite was added so that the free residual chlorine concentration of the sample was pH 7.0, temperature 20 ° C., reaction time 24 hours, and 24 hours later, 1 to 2 mg / L. The amount of trihalomethane produced was determined by simultaneous analysis using a purge / trap / gas chromatograph / mass spectrometer. The purge / trap apparatus used was “TEKMA, Tekmar Stratum”, the gas chromatograph was “Agilent, 7890”, and the mass spectrometer was “Agilent, 5975C”.
・ Measurement method of effective halogen concentration: measured by DPD method using residual chlorine measuring device (manufactured by Hach, “DR-4000”)

(Evaluation methods)
[Total trihalomethane concentration in RO water supply and RO permeated water, removal rate of total trihalomethane in reverse osmosis membrane (RO membrane)]
Compositions 1 to 4 as shown in Table 1 were added to simulated water or pure water, and the pH was adjusted to 8. The water temperature was adjusted to 25 ° C. and circulated through the RO apparatus. Four hours later, the total trihalomethane concentration (mg / L) in the RO water supply and RO permeated water was measured. From the total trihalomethane concentration in the RO water supply and RO permeated water, the removal rate (%) of the total trihalomethane in the reverse osmosis membrane (RO membrane) was determined. The results are shown in Table 1. Here, the total trihalomethane refers to four substances of chloroform, bromodichloromethane, dibromochloromethane and bromoform.

Total trihalomethane concentration was measured by a simultaneous analysis method using a purge / trap / gas chromatograph / mass spectrometer in accordance with the method (Ministry of Health, Labor and Welfare Notification No. 261) established by the Minister of Health, Labor and Welfare based on the provisions of the Ministerial Ordinance on Water Quality Standards. .

Thus, in Examples 1 to 3, the trihalomethane content in the permeated water could be reduced while having a sufficient slime suppressing effect as compared with Comparative Example 1. In the case of Reference Examples 1 and 2 using pure water as raw water, almost no trihalomethane was produced.

“Comparative test of reverse osmosis membrane (RO membrane) rejection rate, impact on permeated water, and oxidizing power”
When using bromine-based oxidants or reaction products of bromine compounds and chlorine-based oxidants and sulfamic acid compounds, and when using general slime inhibitors such as hypochlorite and hypobromite The effect on the reverse osmosis membrane (RO membrane) rejection rate, the effect on the permeated water, the oxidizing power, and the bactericidal power were compared.

Under the following conditions, compositions 1, 2, 4 to 7 are added to the raw water of the reverse osmosis membrane device to influence the exclusion rate of the reverse osmosis membrane (RO membrane), the effect on the permeated water, and the oxidizing power. Compared.

[Composition 5]
Each composition of Composition 2 was added separately in water.

[Composition 6]
Composition 6 containing bromine chloride, sodium sulfamate, and sodium hydroxide was used. The pH of the composition 6 was 14, and the effective halogen concentration (effective chlorine equivalent concentration) was 7% by weight.

[Composition 7]
Sodium bromide: 15% by weight, 12% sodium hypochlorite aqueous solution: 42.4% by weight were separately added to water.

(Test conditions)
Test apparatus: Flat membrane test apparatus Separation membrane: Polyamide polymer reverse osmosis membrane ES20 manufactured by Nitto Denko Corporation
・ Operating pressure: 0.75 MPa
Raw water: Sagamiharai water (pH 7.2, conductivity 240 μS / cm, bromide ion concentration less than 1.0 mg / L)
・ Drug: Compositions 1, 2, 4 to 7 are added so that the effective halogen concentration (effective chlorine equivalent concentration) is 10 mg / L.

(Evaluation methods)
・ Effect on rejection rate of reverse osmosis membrane (RO membrane): Conductivity rejection rate after 30 days water flow (%)
(100- [permeated water conductivity / feed water conductivity] × 100)
・ Effect on permeated water: Effective halogen concentration (effective chlorine equivalent concentration, mg / L) in permeated water 1 hour after addition of chemicals was measured using a residual chlorine measuring device ("DR-4000" manufactured by Hach). Measured by DPD method / Oxidation power: Measures redox potential (ORP) of feed water after 1 hour using redox potential measuring device (RM-20P type ORP meter, manufactured by Toa DKK)

"Comparison test of bactericidal activity"
Under the following conditions, compositions 1, 2, 4 to 7 were added to simulated water, and the bactericidal power was compared.

(Test conditions)
・ Water: Simulated water prepared by adding normal bouillon to Sagamiharai water to adjust the number of general bacteria to 10 ⁵ CFU / ml. Drug: Composition 1, 2, 4-7, effective halogen concentration (in terms of effective chlorine) Concentration) added to 1 mg / L (effective halogen concentration measurement method: measured by DPD method using a residual chlorine measuring device (“DR-4000” manufactured by Hach))

(Evaluation methods)
・ Measures the number of general bacteria 24 hours after the addition of chemicals using a bacterial count kit (manufactured by Sanai Oil, BioChecker TTC)

Table 2 shows the test results.

Compositions 1, 2, 5, and 6 maintained a high reverse osmosis membrane (RO membrane) rejection rate, had low effective halogen concentration (effective chlorine equivalent concentration) of permeated water, and high oxidation power and bactericidal power. Among compositions 1, 2, 5, and 6, composition 1 maintained the highest reverse osmosis membrane (RO membrane) rejection rate and had the lowest effective halogen concentration (effective chlorine equivalent concentration) of permeated water. .

Composition 4 had high oxidizing power and bactericidal power, but the rejection rate of the reverse osmosis membrane (RO membrane) was reduced, and the effective halogen concentration (effective chlorine equivalent concentration) of the permeated water was also high. Although the composition 7 had high oxidizing power and bactericidal power, the effective halogen concentration (effective chlorine equivalent concentration) of permeated water was slightly high.

"Comparison experiment of bromate ion concentration in permeate"
The bromate ion concentration of permeated water with and without nitrogen gas purge during composition preparation was compared.

[Preparation of Composition 1 ']
In the same manner as in Composition 1, in a nitrogen atmosphere, liquid bromine: 17% by weight (wt%), sulfamic acid: 10.7% by weight, sodium hydroxide: 12.9% by weight, potassium hydroxide: 3.95 The composition 1 ′ was prepared by mixing the weight%, water: residue. Composition 1 ′ had a pH of 14, an effective halogen concentration (effective chlorine equivalent concentration) of 7.5% by weight, and a bromic acid concentration of less than 5 mg / kg.

[Preparation of Composition 8]
In the atmosphere without nitrogen purge, liquid bromine: 17% by weight (wt%), sulfamic acid: 10.7% by weight, sodium hydroxide: 12.9% by weight, potassium hydroxide: 3.95% by weight, Water: the residue was mixed to prepare composition 8. Composition 8 had a pH of 14, an effective halogen concentration (effective chlorine equivalent concentration) of 7.4% by weight, and a bromic acid concentration of 63 mg / kg.

(Test conditions)
Test apparatus: Flat membrane test apparatus Separation membrane: Polyamide polymer reverse osmosis membrane ES20 manufactured by Nitto Denko Corporation
・ Operating pressure: 0.75 MPa
Raw water: Sagamiharai water (pH 7.2, conductivity 240 μS / cm)
-Drug: Compositions 1 'and 8 are added so that the effective halogen concentration (effective chlorine equivalent concentration) is 50 mg / L.

(Evaluation methods)
-The bromate ion concentration in the permeated water was measured by ion chromatography-post column absorptiometry.

Table 3 shows the test results.

In composition 1 ', the bromate ion concentration in the feed water and permeate was less than 1 μg / L. In composition 8, the bromate ion concentration in the feed water and permeated water was higher than in composition 1 '.

Next, when a hypobromite stabilizing composition which is a “reaction product of bromine-based oxidant and sulfamic acid compound” is used as a slime inhibitor (Example 4), “bromine-based oxidant” is used. (Example 5) and when hypochlorous acid, which is a general slime inhibitor, is used (Comparative Example 2), hypochlorous acid is a reaction product of hypochlorous acid and a sulfamic acid compound. It compared about the trihalomethane density | concentration in a treated water with the case where a chloric acid stabilization composition is used (comparative example 3), and the influence on disinfection performance.

[Composition 9]
Composition 9 was prepared by mixing 12% aqueous sodium hypochlorite solution: 50% by weight, sulfamic acid: 10% by weight, sodium hydroxide: 8% by weight, water: residue. The pH of the composition 9 was 14, and the effective halogen concentration (effective chlorine equivalent concentration) was 6% by weight.

<Examples 4 and 5, Comparative Examples 2 and 3>
Under the following conditions, compositions 1, 3, and 4 were added to the raw water, and the total trihalomethane concentrations in the treated water were compared. The following simulated water was used as raw water.

(Test conditions)
Raw water: Simulated water (pure water with humic acid (manufactured by Wako Pure Chemical Industries) 8.9 mg / L as a trihalomethane precursor and sodium bromide (manufactured by Kanto Kagaku, special grade) as a bromide ion source with a concentration of 0.1 to Added to 300mg / L)
-Drug: Compositions 1, 3, and 4 are added so that the effective halogen concentration (effective chlorine equivalent concentration) is 3 mg / L.-Raw water pH: adjusted so that the pH of the test water is 8 after the drug is added. Temperature: 25 ° C
・ Measurement method of effective halogen concentration: measured by DPD method using residual chlorine measuring device (manufactured by Hach, “DR-4000”)

(Evaluation methods)
[Total trihalomethane concentration in treated water]
Compositions 1, 3, and 4 were added to the simulated water and the pH was adjusted to 8, and the water temperature was adjusted to 25 ° C. and stirred for 4 hours. After 4 hours of stirring, the total trihalomethane concentration (mg / L) in the treated water was measured. The results are shown in FIG. Here, the total trihalomethane refers to four substances of chloroform, bromodichloromethane, dibromochloromethane and bromoform.

[Comparison test of bactericidal activity]
Under the following conditions, compositions 1 and 9 were added to the simulated water, and the bactericidal power was compared.

(Test conditions)
・ Water: Simulated water prepared by adding normal bouillon to Sagamiharai water and adjusting the number of general bacteria to 10 ⁵ CFU / ml. ・ Drugs: Compositions 1 and 9 as effective halogen concentrations (effective chlorine equivalent concentrations). Added to 1 mg / L (effective halogen concentration measurement method: measured by DPD method using a residual chlorine measuring device (manufactured by Hach, “DR-4000”))

(Evaluation methods)
・ Measure the number of general bacteria 24 hours after adding the drug using a bacterial count kit (manufactured by Sanai Oil, Bio Checker TTC)

Table 4 shows the test results.

Thus, in Examples 4 and 5, compared with Comparative Examples 2 and 3, it is possible to easily suppress the production of trihalomethane while suppressing the production of slime in water containing a trihalomethane precursor and bromide ions. did it.

"Time-dependent change in effective halogen concentration in water containing trihalomethane precursors"
[Preparation of Composition 2 ′]
A composition prepared according to the following procedure based on the contents described in JP-T-11-506139. Composition 2 ′ had a pH of 14, an effective halogen concentration (effective chlorine equivalent concentration) of 5% by weight, and a bromic acid concentration of 15 mg / kg.
(1) To 27.0 g of 40 wt% sodium bromide pure aqueous solution, 41.7 g of 12% sodium hypochlorite solution was added and stirred.
(2) A stabilized solution composed of 56.0 g of pure water, 26.0 g of sulfamic acid, and 18.0 g of sodium hydroxide was prepared.
(3) 31.3 g of the stabilized solution of (2) was added to the solution of (1) while stirring to obtain the target composition 2 ′.

<Example 6, Comparative Example 4>
Under the conditions shown in Table 5, simulated seawater A having a trihalomethane production capacity of 0.11 mg / L (artificial seawater with humic acid (manufactured by Wako Pure Chemical Industries, Ltd.) 8.9 mg / L added as a trihalomethane precursor, TOC: 5 mg / L), or simulated seawater B having a trihalomethane production capacity of 0.04 mg / L (artificial seawater added with 8.9 mg / L of humic acid (manufactured by Wako Pure Chemical Industries) as a trihalomethane precursor, TOC: 5 mg / L) ), Or simulated water C having a trihalomethane production capacity of 0.01 mg / L (a mixture of pure water with 8.9 mg / L humic acid (manufactured by Wako Pure Chemical Industries, Ltd.) as a trihalomethane precursor, TOC: 5 mg / L) respectively, composition 1, composition 2 ', or a composition 4 was added to a 10 mg / L AsCl ₂ or 5 mg / L AsCl ₂ as an active halogen . Using a sodium hydroxide aqueous solution or a sulfuric acid aqueous solution, the pH of the test solution was adjusted to 8.4, and stored at room temperature (25 ° C.) under light-shielding conditions, and the change with time in the total halogen concentration was measured. . The results are shown in Table 5. Simulated seawater A and B were prepared by dissolving each component in pure water so as to have the composition shown in Table 6 using artificial seawater (manufactured by Yashima Pharmaceutical Co., Ltd., Aquamarine (registered trademark)). Is. The trihalomethane production ability was measured by the same method as in Example 1.

The total halogen concentration (effective chlorine equivalent concentration) was measured according to the following procedure.

The effective halogen concentration is determined by diluting the sample and using a multi-item water quality analyzer DR / 4000 manufactured by HACH (in the case of the total halogen concentration, the measurement item is “total chlorine”), and the effective chlorine measurement method (DPD (diethyl-p -Phenylenediamine) method) (mg / L asCl ₂ ). The effective halogen referred to here is a value measured by an effective chlorine measuring method (DPD method). In addition, an effective bromine concentration (mg / L asCl ₂ ), which is an effective halogen concentration in terms of chlorine, can be calculated from the effective chlorine concentration, and the measured value by the effective chlorine measurement method (DPD method) is 2.25 (159.8). (G / mol) /70.9 (g / mol)) (Molecular weight of chlorine (Cl ₂ ) is 70.9 (g / mol), and molecular weight of bromine (Br ₂ ) Is 159.8 (g / mol).)

In Table 5, the comparison between the example and the comparative example shows that the composition 1 and the composition 2 ′ have a higher residual halogen than the composition 4 over a long period of time, and the membrane separation apparatus is stopped for a long period of time. It can be seen that the separation membrane can be sterilized effectively. Here, the reason why the decrease rate of the total halogen concentration in the simulated seawaters A and B is larger than that in the simulated water C than in the comparison between the comparative examples 4-1 and 4-2 and the comparative example 4-3. This is probably because hypochlorous acid and bromide ions in simulated seawater reacted to change to more unstable hypobromous acid. On the other hand, from Examples 6-1, 6-2, and 6-4, compositions 1, 2 ′, which are hypobromite stabilizing compositions, have a lower total halogen concentration in simulated seawater than composition 4. Suppressed. This is because the hypobromite stabilization composition is more stable than hypochlorous acid and hypobromite, and a portion of the hypobromite stabilization composition and chlorination in artificial seawater. This is thought to be due to the reaction of the product ions and the production of bound chlorine with extremely high stability.

“Reverse osmosis membrane (RO membrane) exclusion rate after immersion in bactericidal solution and effect on permeated water”
<Example 7>
Table 7 shows the results of measuring the conductivity exclusion rate and the permeated water retention rate of the membrane after the separation membrane was immersed and stored in each bactericide solution for 30 days.

(Test conditions)
-Separation membrane: Nitto Denko Corporation, polyamide polymer reverse osmosis membrane ES15
Test water: Simulated seawater A or simulated seawater B or simulated water C
・ Chemicals: added to a total halogen concentration of 10 mg / L asCl ₂・ Test water pH: adjusted to a predetermined pH using sodium hydroxide aqueous solution or sulfuric acid aqueous solution ・ Immersion storage period of separation membrane: 30 days Conditions: room temperature (25 ° C) under light-shielding conditions

(Exclusion rate measurement method)
・ Test equipment: Flat membrane test equipment ・ Operating pressure: 0.75 MPa
・ Raw water: Sagamiharai water (pH 7.2, conductivity 24 mS / m)
Conductivity rejection rate [%] = 100− [permeated water conductivity / feed water conductivity] × 100
Permeate retention rate [%] = [permeate amount of separation membrane immersed in test water / permeate amount of new separation membrane] × 100

In composition 4, when the separation membrane is stored for a long period of time, the separation membrane deteriorates and the rejection rate is greatly reduced. However, compositions 1 and 2 'maintain a high rejection rate even if the separation membrane is stored for a long period of time. Film deterioration was suppressed.

As described above, in the examples using the hypobromite stabilizing composition, in the membrane separation system that operates and shuts down, the degradation of the separation membrane is suppressed, and the separation membrane is effectively removed during the shutdown. It was found that it can be sterilized.

1 membrane separation system, 10 raw water tank, 12 membrane separator, 14 pump, 16 raw water piping, 18 raw water supply piping, 20 permeated water piping, 22 concentrated water piping, 24 disinfectant supply piping.

Claims

In the feed water or wash water to a membrane separation device comprising a separation membrane containing a trihalomethane precursor,
A method for suppressing slime of a separation membrane, comprising the presence of a bromine-based oxidant or a reaction product of a bromine compound and a chlorine-based oxidant.
In the feed water or wash water to a membrane separation device comprising a separation membrane containing a trihalomethane precursor,
A brominated oxidant or a reaction product of a bromine compound and a chlorinated oxidant;
A sulfamic acid compound;
A method for suppressing slime of a separation membrane, wherein
In the feed water or wash water to a membrane separation device comprising a separation membrane containing a trihalomethane precursor,
A brominated oxidant or a reaction product of a bromine compound and a chlorinated oxidant;
A sulfamic acid compound;
A slime-suppressing method for a separation membrane, characterized by including the reaction product of
In the feed water or wash water to a membrane separation device comprising a separation membrane containing a trihalomethane precursor,
A method for suppressing slime of a separation membrane, comprising the presence of a mixture of bromine and a sulfamic acid compound or a reaction product of bromine and a sulfamic acid compound.
It is a slime suppression method of the separation membrane of Claim 4, Comprising:
The reaction product of bromine and a sulfamic acid compound is obtained by a method including a step of reacting a mixed liquid containing water, an alkali and a sulfamic acid compound by adding bromine in an inert gas atmosphere. A method for suppressing slime in a separation membrane.
A method for suppressing slime of a separation membrane according to any one of claims 1 to 5,
The method for suppressing slime of a separation membrane, wherein the concentration of the trihalomethane precursor in the feed water or the washing water is 0.001 mg / L or more as a trihalomethane generating ability.
A method for suppressing slime of a separation membrane according to any one of claims 1 to 6,
A method for suppressing slime of a separation membrane, wherein the separation membrane is a polyamide polymer membrane.
A method for suppressing slime of a separation membrane according to any one of claims 1 to 7,
The method for suppressing slime of a separation membrane, wherein the trihalomethane precursor contains humic substances.
A method for suppressing slime of a separation membrane according to any one of claims 1 to 8,
The method for suppressing slime of a separation membrane, wherein the water supply or washing water further contains bromide ions.
A method for suppressing slime of a separation membrane according to claim 9,
A method for suppressing slime of a separation membrane, wherein a concentration of bromide ions in the water supply or washing water is 5 mg / L or more.
A method for suppressing slime of a separation membrane according to any one of claims 1 to 10,
The membrane separation device comprising the separation membrane is a membrane separation device in which operation and shutdown are performed,
During the shutdown of the membrane separator,
The presence of the bromine-based oxidant or a reaction product of a bromine compound and a chlorine-based oxidant;
The bromine-based oxidant or a reaction product of a bromine compound and a chlorine-based oxidant and a sulfamic acid compound are present;
The brominated oxidant, or the reaction product of a bromine compound and a chlorinated oxidant and the reaction product of a sulfamic acid compound, or
The presence of a reaction product of the bromine with a sulfamic acid compound;
A method for suppressing slime of a separation membrane.
It is a slime suppression method of the separation membrane of Claim 11, Comprising:
A method for suppressing slime of a separation membrane, wherein the pH of water present in the membrane separation device is pH 5.5 or more.
A method for suppressing slime of a separation membrane according to claim 10 or 11,
The method for suppressing slime of a separation membrane, wherein the water present in the membrane separation device is at least one of seawater and brine.