TW201709968A - Method for pretreating reverse osmosis membrane device, and device for treating water - Google Patents

Abstract

The purpose of the present invention is, in the treatment of an RO membrane by adding an oxidative chemical substance to water containing an oxidizing agent, to prevent the membrane deterioration of the RO membrane, which can be caused by a residue of the oxidizing agent, by adding a reducing agent, and to prevent the decomposition of the oxidative chemical substance, which can be caused by the added reducing agent, to achieve the water treatment effect of the oxidative chemical substance effectively. As the reducing agent, nitrous acid and/or a salt thereof is used. Nitrous acid and/or a salt thereof can reduce a residue of the oxidizing agent such as chlorine, and does not undergo a redox reaction with an oxidative chemical substance such as chlorosulfamic acid at a practically available concentration and therefore never removes the oxidative chemical substance through reduction to reduce the concentration of the effective component even when a residue of nitrous acid and/or the salt thereof remains.

Description

Pretreatment method of reverse osmosis membrane device and water treatment device

The present invention relates to a pretreatment method for a reverse osmosis membrane (RO membrane) device. In particular, the present invention relates to a pretreatment method for an RO membrane device in which an oxidizing drug is added to an oxidizing agent-containing water to perform RO membrane treatment, and a reducing agent is added to prevent deterioration of a membrane of the RO membrane caused by residual oxidizing agent, and at the same time preventing The added reducing agent causes decomposition of the oxidizing drug, and effectively obtains the treatment effect of the oxidizing drug.

Further, the present invention relates to a water treatment apparatus using the prior treatment method.

The RO membrane device is widely used as a means of producing pure water, such as water for industrial use, urban water supply, well water, river water, lake water, and factory wastewater. In this case, in order to suppress biofouling by microorganisms contained in the water to be treated, a chlorine-based oxidizing agent such as chlorine, sodium hypochlorite or sodium chlorite or an oxidizing agent such as hydrogen peroxide or ozone is added to the water to be treated. Further, the use of an electrode to generate chlorine is also performed.

Further, the oxidizing agent may be added as a treatment before the RO membrane treatment, and may be added in order to oxidize iron or manganese in the water to be treated and remove it by a filtration device.

When the RO membrane is treated with water to which an oxidizing agent is added, the RO membrane is oxidatively degraded by the residual oxidizing agent.

Conventionally, an activated carbon column is provided in the front stage of the RO membrane device to remove residual oxidizing agent such as chlorine (Patent Document 1), or a reducing agent such as sodium hydrogen sulfite or sodium sulfite is added to the RO membrane device to decompose and remove chlorine. Document 2) and so on.

When an activated carbon column is provided, biofouling occurs in the tower to contaminate the latter stage device, and there is a disadvantage in that the initial cost is required, and the decomposition and removal of the residual oxidizing agent by the addition of the reducing agent are generally performed.

When the reducing agent is added, the concentration of the residual oxidizing agent varies depending on the water quality of the water to be treated, and in order to completely remove the residual oxidizing agent, the deterioration of the RO film is surely prevented. Generally, the reducing agent is added more than the reaction equivalent of the residual oxidizing agent.

In the RO membrane treatment, in order to prevent contamination (sludge) of the RO membrane caused by turbidity or organic matter contained in the treated water, 2,2-dibromo-3-nitropropionamide is added to the treated water ( DBNPA), a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one (Cl-MIT) and 2-methyl-4-isothiazolin-3-one (MIT) (DOW Chemical Co., Ltd.) Product name "Caisson WT"), ammonia chloramine, chloramine sulfonic acid, and stabilized hypobromous acid-based slime control agent (Organo E266 series, manufactured by Organo Co., Ltd.) and "Stablex" manufactured by Nalco Co., Ltd. ) The case of oxidizing drugs.

The oxidizing agent is a drug used for oxidizing a target substance such as sodium hypochlorite. In contrast, an oxidizing drug has an oxidizing power such as the above-mentioned Caisson WT, but the purpose of use is not limited to oxidizing. Product, the two are different. More specifically, at pH 7.0 and 20 ° C, a substance (strong oxidizing agent) which undergoes redox reaction when an equivalent amount of nitrite ions is added is defined as an "oxidizing agent", and a substance which does not undergo a redox reaction under the same conditions (weak An oxidizing agent is defined as an "oxidizing drug."

When an oxidizing agent and an oxidizing drug are used, for example, an oxidizing agent is added to the water to be treated, and then agglomerated and filtered, and then an excess amount of a reducing agent is added to decompose and remove the residual oxidizing agent, followed by addition of an oxidizing drug to perform RO membrane treatment. However, when an excess amount of the reducing agent is added for the removal of the residual oxidizing agent, and the oxidizing drug is added, the remaining reducing agent reacts with the oxidizing drug to decompose and remove the oxidizing drug, and the concentration of the active ingredient of the oxidizing drug decreases. Therefore, the effect corresponding to the amount of addition of the oxidizing drug is not obtained, and in order to obtain the intended effect, it is necessary to calculate the decomposition-removed portion by the reducing agent, and the problem of the amount of the oxidizing drug added is increased.

Patent Document 1: Japanese Patent Laid-Open No. Hei 10-337563

Patent Document 2: Japanese Patent Laid-Open No. Hei 7-308671

An object of the present invention is to provide an oxidizing agent for adding an oxidizing agent to water containing an oxidizing agent, and to add a reducing agent to prevent deterioration of a film of an RO film caused by a residual oxidizing agent, and to prevent an oxidizing drug due to an added reducing agent. A pretreatment method and a water treatment device for an RO membrane device which decompose and efficiently obtain a water treatment effect of an oxidizing drug.

The inventors of the present invention conducted an intensive review in order to provide a novel reducing agent which does not affect the treatment of the RO membrane, and found that nitrous acid and/or its salt system is most suitable.

Nitrous acid and/or its salt is a mixture of DBNPA, Cl-MIT, and MIT (product name "Caisson"), which is used to reduce and remove residual oxidizing agent such as chlorine. Oxidation reduction of oxidizing drugs such as ammonia chloramine, chloramine sulfonic acid, and stabilized hypobromous acid-based slime control agent (Orpero E266 series, manufactured by Organo Co., Ltd., and "Stablex" manufactured by Nalco Co., Ltd.) The reaction does not reduce and remove the oxidizing drug to reduce the concentration of the active ingredient.

The present invention has been achieved on the basis of such knowledge and knowledge, and the following is taken as the gist.

[1] A pretreatment method for a reverse osmosis membrane device, which is a treatment method for treating an oxidant-containing water by a reverse osmosis membrane device reverse osmosis membrane, characterized in that nitrous acid and/or nitrous acid is added to the oxidant-containing water. The salt is reduced to remove the oxidizing agent.

[2] The pretreatment method of the reverse osmosis membrane device according to [1], wherein an oxidizing drug is added to the water after the addition of the nitrous acid and/or a salt thereof.

[3] The pretreatment method of the reverse osmosis membrane device according to [2], wherein the nitrous acid and/or a salt thereof is added to the water after the addition of the nitrous acid and/or a salt thereof After the different reducing agents, the aforementioned oxidizing drug is added.

[4] The pretreatment method of the reverse osmosis membrane device according to [2] or [3], wherein the oxidizing drug is selected from the group consisting of a salt of chloramine sulfonic acid, chloramine sulfonic acid, and a stabilized hypobromous acid-based slime. One or two or more types of the group formed by the agent.

[5] The pretreatment method of the reverse osmosis membrane device according to [3] or [4], wherein the reducing agent different from nitrous acid and/or a salt thereof is selected from the group consisting of hydrogensulfite, sulfite, and thiosulfuric acid. One or two or more kinds of salts.

[6] A water treatment apparatus which is a water treatment apparatus for treating a water containing an oxidizing agent by a reverse osmosis membrane, comprising: a reducing agent adding means for adding nitrous acid and/or a salt thereof to the oxidizing agent-containing water; An oxidizing drug adding means for adding an oxidizing drug to water added with nitric acid and/or a salt thereof, and a reverse osmosis membrane device for treating water to which an oxidizing drug is added by a reverse osmosis membrane.

According to the present invention, when an oxidizing drug is added to an oxidizing agent-containing water for RO membrane treatment, a reducing agent is added to prevent deterioration of the membrane of the RO membrane caused by the residual oxidizing agent, and at the same time, prevention of decomposition of the oxidizing drug due to the added reducing agent is effective. The water treatment effect of the oxidizing drug is obtained.

1‧‧‧ original sink

2‧‧‧Filter device

3‧‧‧Filtering sink

4‧‧‧Safety filter

5‧‧‧RO membrane device

Fig. 1 is a system diagram showing an embodiment of a water treatment apparatus of the present invention.

Form of implementing the invention

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

Hereinafter, the water to be treated treated with the RO membrane is described as "water supply".

In the present invention, when the RO membrane is treated with water containing an oxidizing agent such as chlorine, nitrous acid and/or a salt thereof is added as a reducing agent for reducing and removing the oxidizing agent instead of a conventional reducing agent such as sodium hydrogen sulfite or sodium sulfite. Hereinafter also referred to as "nitrous acid (salt)").

In the present invention, the RO membrane system includes a generalized RO membrane of a NF membrane (Nanofiltration Membran), and the material thereof is not limited, and a cellulose acetate polymer, a polyamide, a polyester, a polyimine, a vinyl polymerization is generally used. Polymer materials such as materials. The form of the RO membrane module and the like are also not particularly limited.

As the nitrite used in the present invention, sodium nitrite is representative, but potassium nitrite, calcium nitrite, magnesium nitrite, aluminum nitrite or the like can also be used. The nitrous acid (salt) may be used alone or in combination of two or more.

The form of use of nitrous acid (salt) is generally an aqueous solution, but may be formulated and used in combination with other solvents, a dispersion medium, a polymer compound for water treatment, an antifouling agent, and a slime controlling agent. From the viewpoint of workability, the use form of nitrous acid (salt) is preferably a liquid form such as an aqueous solution.

When the nitrous acid (salt) is formulated and used, the content ratio of nitrous acid (salt) of the nitrous acid (salt)-containing preparation is not particularly limited, but The nitrate ion is preferably from 5 to 43% by mass, more preferably from 10 to 38% by mass. When nitrous acid (salt) is blended in such a range, it is preferable to reduce the volume of the nitrous acid (salt) preparation and to have good stability.

The nitrous acid (salt) is not particularly limited as long as it is a water supply containing an oxidizing agent such as chlorine. By adding nitrous acid (salt) to the water supply, it is exhibited that the oxidizing agent such as chlorine is reduced, and the oxidizing drug added in the latter stage is hardly reduced by the remaining nitrous acid (salt).

The type or use form of the oxidizing agent contained in the water supply is not particularly limited. As the oxidizing agent, chlorine is representative, but hydrogen peroxide, chlorine dioxide, chlorous acid and/or a salt thereof, hypochlorous acid and/or a salt thereof, ozone, chlorine generated by using an electrode, or the like may be used. These oxidizing agents may be used alone or in combination of two or more.

The amount of the nitrous acid (salt) added is not less than the reaction equivalent of the amount of the residual oxidizing agent in the water supply, but is preferably 2 to 3 times the reaction equivalent, and is preferably 3 to 5 times in order to surely prevent the residual of the oxidizing agent.

When nitrous acid (salt) is added and reacted with the oxidizing agent in the water supply, depending on the conditions, the oxidizing agent may remain in a trace amount even if it is added in an equivalent amount or more. In this case, a conventional reducing agent having good reactivity such as sodium hydrogen sulfite or the like is used as the second reducing agent in the step before the RO membrane device, and a reaction equivalent or more is added to the residual amount of the oxidizing agent, preferably 2 ~3 times, especially to prevent the residual of oxidant, it can be 3 to 5 times.

A conventional reducing agent such as sodium hydrogen sulfite added as a second reducing agent reduces an active ingredient by reducing an oxidizing drug However, the residual amount of the oxidizing agent after adding nitrous acid (salt) as the first reducing agent is a small amount, and the second reducing agent addition ratio such as sodium hydrogen sulfite added thereto is also small. Therefore, even when the second reducing agent remains, the amount of the oxidizing drug to be reduced is a small amount, and the decrease in the concentration of the active ingredient of sodium hydrogen sulfite can be suppressed.

As the second reducing agent, one or two or more kinds of hydrogen sulfite such as sodium bisulfite, sulfite such as sodium sulfite, or thiosulfate such as sodium thiosulfate can be used.

The amount of addition of nitrous acid (salt) or the amount of nitrous acid (salt) of the first reducing agent and the second reducing agent is specifically as follows.

The concentration of the oxidizing agent in the water supply is described by the DPD method using N,N-diethyl-1,4-phenylenediamine in JIS K 0400-33-10:1999 as the chlorine concentration.

When sodium nitrite is used as the nitrous acid (salt), sodium nitrite which reacts with 1 g equivalent of free chlorine is 1.0 g (nitrite ion is 0.67 g), but in actual use, it is preferable to add this. Times around. When the oxidizing agent is other than chlorine, it is also equivalent to 1 g of perchlorine of the above DPD method, and the reaction equivalent of 1.0 g of sodium nitrite (0.67 g of nitrite ions).

Since the free chlorine is slightly residual depending on the pH condition of the water supply, a second reducing agent having good reactivity is added. At this time, the reaction equivalent of the second reducing agent was 1.5 g with respect to free chlorine, 1.5 g of sodium hydrogensulfite, 1.8 g of sodium sulfite, and 2.2 g of sodium thiosulfate.

The nitrous acid (salt) used in the present invention has low reactivity with an oxidizing agent, and the present invention is particularly suitable for a reducing agent since the oxidizing agent is hardly eliminated. After the addition, an RO membrane treatment of an oxidizing drug is added.

The oxidizing agent is a drug which is used for oxidizing a target substance such as sodium hypochlorite. In contrast, an oxidizing drug has an oxidizing power such as the above-described Caisson WT, but the purpose of use is not limited to an oxidized drug, and the two are distinguished. More specifically, at pH 7.0 and 20 ° C, a substance (strong oxidizing agent) which undergoes redox reaction when an equivalent amount of nitrite ions is added is defined as an "oxidizing agent", and a substance which does not undergo a redox reaction under the same conditions (weak An oxidizing agent is defined as an "oxidizing drug."

As an oxidizing drug, 2,2-dibromo-3-nitropropionamide (DBNPA) and 5-chloro-2-methyl which are generally used as an oxidizing drug for preventing fouling of an RO membrane are mentioned. -4-isothiazolin-3-one (Cl-MIT), 5-chloro-2-methyl-4-isothiazolin-3-one (Cl-MIT) and 2-methyl-4-isothiazoline a mixture of -3-ketone (MIT) (trade name "Caisson WT" manufactured by DOW Chemical Co., Ltd.), ammonia chloramine, chloramine sulfonic acid and/or its salt, and stabilized hypobromous acid-based slime control agent (Organo) ) The product name is "Orpersion E266 Series", and the product name "Stablex" manufactured by Nalco Co., Ltd.). These may be used alone or in combination of two or more.

When an oxidizing drug is added to the water supply, the amount of the oxidizing drug varies depending on the type of the oxidizing drug to be used, the water quality of the water supply, or the RO membrane treatment conditions. However, the amount of the total amount of the chlorinated compound is usually about 0.01 to 50 mg/L. Specifically, in the case of sodium chloramine sulfonate, the amount of addition in terms of total chlorine is usually 0.1 to 10 mg/L, preferably about 0.5 to 3 mg/L. The addition amount of the stabilized hypobromous acid-based slime control agent (Orgoro E266 series, manufactured by Organo Co., Ltd.) and the "Stablex" manufactured by Nalco Co., Ltd. It is 0.01 to 3 mg/L, preferably 0.02 to 0.2 mg/L. The addition amount of Cl-MIT which is not detected as perchlorine is usually 0.01 to 0.5 mg/L, preferably about 0.03 to 0.15 mg/L. The amount of DBNPA added is usually 0.1 to 10 mg/L, preferably about 0.2 to 6 mg/L.

According to the present invention, the nitrous acid (salt) added for the reduction and removal of the residual oxidizing agent has little reactivity with these oxidizing chemicals, so that the effect of the added oxidizing drug can be maximized. Therefore, the amount of the oxidizing drug can be suppressed and the cost of the drug can be reduced.

FIG. 1 specifically shows the addition of nitrous acid (salt) or nitrous acid (salt) as a first reducing agent to a second reducing agent after adding an oxidizing agent to the water supply, and further adding the oxidizing drug to the RO film treatment. An example of an embodiment of a water treatment device.

In Fig. 1a and Fig. 1b, the raw water in the raw water tank 1 is filtered by the filter device 2, and the filtered water is passed through the filtration treatment tank 3 and the safety filter 4, and is treated by the RO membrane of the RO membrane device 5, and the treated water is taken out.

In the embodiment of Fig. 1a, an oxidizing agent is added to a pipe from which the raw water is supplied to the filter device 2 from the raw water tank 1, and nitrous acid (salt) is added to the inlet of the RO membrane device 6 at the rear stage of the safety filter 5, and then added. Oxidizing drugs.

In the embodiment of Fig. 1b, nitrous acid (salt) is added as a first reducing agent at the inlet of the RO membrane device 6 at the rear stage of the safety filter 5, and then a second reducing agent such as sodium hydrogen sulfite is added, followed by addition. Oxidizing drugs.

The order of addition of each drug is as described above, and the addition of the local system There is no particular limitation, and for example, it may be added on the inlet side or the outlet side of the filtration device 2. Each drug can also be added in different places.

Fig. 1a and Fig. 1b show an example of an embodiment of a water treatment device according to the present invention, and the present invention is not limited to the device of the drawings.

The oxidizing agent may be contained in a water supply to which nitrous acid (salt) is added. If the oxidizing agent has been contained in the preceding step, the pretreatment method and the water treatment device of the RO membrane device of the present invention do not require an oxidizing agent addition step or an oxidizing agent addition. means.

The pretreatment method of the RO membrane device of the present invention can be carried out by a control unit including a CPU or the like in a device (for example, a personal computer or the like) for managing the water quality of the water supply to be processed. Further, the preprocessing method of the RO membrane device of the present invention may be stored in a hardware resource including a recording medium (non-volatile memory (USB memory or the like), HDD, CD, etc.), and the like. Implementation. The control unit may be configured to add a water treatment system that controls nitrous acid (salt) as a reducing agent or nitrous acid (salt) as a first reducing agent and a second reducing agent to the water supply.

Example

The invention will be more specifically described by the following examples, but the invention is not limited by the following examples.

In the following examples and comparative examples, as the water supply for the RO membrane, the tap water of the activated carbon from the Noji-cho, Shimo-machi, Tochigi, Japan, is dechlorinated by activated carbon (hereinafter referred to as "dechlorinated town water"). The experiments were carried out at pH 7.0 and at a temperature of 20 °C.

Use the following as an added test. In the measurement of residual chlorine, the HACH company's pocket residual chlorine meter "HACH 2470" was used.

Sodium hypochlorite aqueous solution (12% effective chlorine, manufactured by Asahi Glass Co., Ltd.)

Sodium nitrite (KISHIDA Chemical Co., Ltd.)

Sodium bisulfite (KISHIDA Chemical Co., Ltd.)

Sodium sulfite (KISHIDA Chemical Co., Ltd.)

Sodium thiosulfate (KISHIDA Chemical Co., Ltd.)

Sodium chloramine sulfonate (made by Kurita Industrial Co., Ltd.)

Cl-MIT (Kurida Industry Co., Ltd.)

DBNPA (DOW Chemical Japan Co., Ltd.)

Sodium bromide (KISHIDA Chemical Co., Ltd.)

Amine sulfonic acid (semi-sulfonic acid sulfonic acid) (KISHIDA Chemical Co., Ltd.)

Sodium hydroxide (KISHIDA Chemical Co., Ltd.)

Sodium hypobromite solution (5% effective bromine) (KISHIDA Chemical Co., Ltd.)

In the table showing the results of the examples and the comparative examples, the added drug is described by the following short form.

[Examples 1 to 6] <Addition of oxidant>

1 g of a sodium hypochlorite diluted solution diluted with a concentration adjustment in which the free chlorine addition rate was fed to the value of Table 2 was added to 99 g of dechlorinated municipal water.

<Addition of first reducing agent>

Then, 1 g of an aqueous sodium nitrite solution diluted with a concentration adjustment in which the sodium nitrite addition ratio was added to the value of Table 2 was added thereto. The sample was collected from this solution and the free chlorine concentration was measured immediately. The results are shown in Table 2.

<Addition of second reducing agent>

In the first, second, and sixth embodiments, after the addition of the first reducing agent, 1 g of an aqueous solution of sodium hydrogen sulfite diluted by concentration adjustment was added so as to add the sodium bisulfite addition ratio to the value shown in Table 2.

The sample was collected from this solution and the free chlorine concentration was measured immediately. The results are shown in Table 2.

In Examples 3, 4, and 5, the following oxidizing drug was added without performing this step.

<Addition of oxidizing drugs>

Then, 1 g of an aqueous solution of sodium chloramine sulfonate diluted by concentration adjustment was added so as to have a total chlorine addition ratio (addition ratio in terms of total chlorine conversion) as shown in Table 2. The sample was collected from this solution and the total chlorine concentration was measured immediately. In Table 2 Show results.

The following are known from Table 2.

When 1.2% or more of sodium nitrite is added to the free chlorine, most of the free chlorine system disappears, and even if there is residual free chlorine, the second reducing agent can be added in a small amount of 0.1 to 0.15 mg/L (Example) 1,2,6 is sodium bisulfite) and is reduced to a level where the free chlorine concentration is not detected.

After the reaction of these, even if sodium chloramine sulfonate as an oxidizing drug was added, the same concentration as the feed concentration was detected, and it was confirmed that the residual sodium nitrite did not undergo redox reaction with sodium chloramine sulfonate. .

[Examples 7, 8]

1 g of a Cl-MIT diluted solution diluted with concentration adjustment in such a manner that the feed addition ratio became the value of Table 3 was added to 99 g of dechlorinated municipal water. Then, the concentration is adjusted in such a manner that the addition rate of sodium nitrite becomes the value of Table 3. 1 g of the diluted aqueous sodium nitrite solution was added thereto. For this solution, the Cl-MIT concentration was determined by liquid chromatography. The results are shown in Table 3.

[Comparative Example 1-4]

1 g of a Cl-MIT diluted solution diluted with concentration adjustment in such a manner that the feed addition ratio became the value of Table 3 was added to 99 g of dechlorinated municipal water. Then, 1 g of sodium hydrogen sulfite or an aqueous sodium sulfite solution diluted with a concentration adjustment in which the feed addition ratio became the value of Table 3 was added thereto. For this solution, the Cl-MIT concentration was determined by liquid chromatography. The results are shown in Table 3.

The following are known from Table 3.

Even with the addition of 600 to 700 times sodium nitrite relative to Cl-MIT, Cl-MIT was detected at the same concentration as the feed concentration. That is, sodium nitrite does not reductively decompose Cl-MIT. Relative to it, sodium bisulfite or sub The sodium sulfate system was added at about 170 times and the Cl-MIT disappeared.

[Examples 9 to 11]

1 g of an aqueous solution of sodium chloramine sulfonate diluted and adjusted to have a concentration of the total chlorine addition rate (addition ratio in terms of perchlorine conversion) as shown in Table 4 was added to 99 g of dechlorinated municipal water. Then, 1 g of an aqueous solution of sodium nitrite diluted and adjusted in such a manner that the sodium nitrite addition ratio was changed to the value shown in Table 4 was added thereto. For this solution, the total chlorine concentration was measured immediately. The results are shown in Table 4.

[Comparative Examples 5 to 10]

1 g of an aqueous solution of sodium chloramine sulfonate diluted and adjusted to have a concentration of the total chlorine addition rate (addition ratio in terms of perchlorine conversion) as shown in Table 4 was added to 99 g of dechlorinated municipal water. Then, 1 g of sodium hydrogen sulfite or an aqueous sodium sulfite solution diluted with a concentration adjustment in such a manner that the feed addition ratio became the value of Table 4 was added thereto. For this solution, the total chlorine concentration was measured immediately. The results are shown in Table 4.

The following are known from Table 4.

In the case of sodium chloramine sulfonate, when sodium nitrite was added, the same concentration as the feed concentration was detected, but sodium hydrogen sulfite or sodium sulfite was added in an equivalent amount, and all the active components of sodium chloramine sulfonate disappeared.

[Examples 12 to 14]

1 g of a DBNPA aqueous solution diluted with a concentration adjustment in which the total chlorine addition ratio (addition ratio in terms of total chlorine conversion) was added to the value of Table 5 was added to 99 g of dechlorinated municipal water. Then, 1 g of an aqueous sodium nitrite solution diluted with a concentration adjustment in which the feed addition ratio became the value of Table 5 was added thereto. For this solution, the total chlorine concentration was measured immediately. The concentration of the active ingredient of DBNPA can be determined as the total chlorine concentration by the DPD method. The results are shown in Table 5.

[Comparative Examples 11 to 16]

1 g of a DBNPA aqueous solution diluted with a concentration adjustment in which the total chlorine addition ratio (addition ratio in terms of total chlorine conversion) was added to the value of Table 5 was added to 99 g of dechlorinated municipal water. Then, 1 g of sodium hydrogen sulfite or an aqueous sodium sulfite solution diluted with a concentration adjustment in which the feed addition ratio is the value of Table 5 was added thereto. For this solution, the total chlorine concentration was measured immediately. The results are shown in Table 5.

The following are known from Table 5.

When DBNPA was added, the same concentration as the feed concentration was detected, but sodium hydrogen sulfite or sodium sulfite was added at about 1.2 times the reaction equivalent, and all the active components of DBNPA disappeared.

[Comparative Examples 17 to 22]

1 g of an aqueous solution of sodium chloramine sulfonate diluted and adjusted to have a concentration of the total chlorine addition rate (addition ratio in terms of perchlorine conversion) as shown in Table 6 was added to 99 g of dechlorinated municipal water. Then, 1 g of an aqueous sodium thiosulfate solution diluted with a concentration adjustment in which the feed addition ratio became the value of Table 6 was added thereto. For this solution, the total chlorine concentration was measured immediately. The results are shown in Table 6.

In Table 6, the concentration of the total chlorine in the sodium chloramine sulfonate disappeared by the addition of sodium thiosulfate is described together.

From Table 6, it can be seen that when sodium chlorsulfate is added, when sodium thiosulfate is added, it is added in an amount of 1.3 times or more by equivalent, and 50% or more of the amount of sodium chloramine sulfonate is lost.

[Examples 15 to 17, Comparative Examples 23-28] <Preparation of stabilized hypobromous acid slime control agent I>

The stabilized hypobromous acid-based slime controlling agent I was prepared by the following procedure.

(1) A solution having a concentration of 45% by weight was prepared by dissolving sodium bromide in pure water.

(2) Dissolving sodium hydroxide in pure water to prepare a solution having a concentration of 48% by weight

(3) 42.4 g of an aqueous solution of sodium hypochlorite and 20.5 g of a 45% by weight aqueous solution of sodium bromide were mixed.

(4) 13.5 g of pure water and 13.8 g of a 48% by weight aqueous sodium hydroxide solution were mixed, and the mixture was heated to 70 ° C, and 9.6 g of an amine sulfonic acid was added to completely dissolve.

(5) The temperature of (4) is maintained at 50 ° C or higher, and (3) is added thereto, and sufficiently mixed.

<Examples 15 to 17>

1 g of the stabilized hypobromous acid-based slime controlling agent I diluted and adjusted to have a concentration of the total chlorine addition rate (addition ratio in terms of perchlorine conversion) as shown in Table 7 was added to 99 g of dechlorinated municipal water. Then, 1 g of an aqueous sodium nitrite solution diluted with a concentration adjustment in which the feed addition ratio was the value of Table 7 was added thereto. For this solution, the total chlorine concentration was measured immediately. The concentration of the active ingredient of the stabilized hypobromous acid-based slime controlling agent I can be determined as the total chlorine concentration by the DPD method. The results are shown in Table 7.

<Comparative Examples 23 to 28>

The stabilized hypobromous acid-based slime control agent diluted with the concentration of the total chlorine addition rate (addition rate in terms of total chlorine conversion) as shown in Table 7 1 g of I was added to 99 g of dechlorinated municipal water. Then, 1 g of sodium hydrogen sulfite or an aqueous sodium sulfite solution diluted with a concentration adjustment in which the feed addition ratio was the value of Table 7 was added thereto. For this solution, the total chlorine concentration was measured immediately. The results are shown in Table 7.

[Examples 18 to 20, Comparative Examples 29 to 34] <Preparation of stabilized hypobromous acid-based slime control agent II>

The stabilized hypobromous acid-based slime controlling agent II was prepared by the following procedure.

(1) Dissolving sodium hydroxide in pure water to prepare a solution having a concentration of 48% by weight

(2) 13.5 g of pure water and 13.8 g of a 48% by weight aqueous sodium hydroxide solution were mixed, and the mixture was heated to 70 ° C, and 9.6 g of an amine sulfonic acid was added to completely dissolve.

(3) The temperature of (2) was kept at 50 ° C or higher, and 62.9 g of a sodium hypobromite solution was added thereto, and the mixture was sufficiently mixed.

<Examples 18 to 20>

1 g of the stabilized hypobromous acid-based slime controlling agent II diluted and adjusted in such a manner that the total chlorine addition ratio (addition ratio in terms of total chlorine conversion) was added to the value of Table 8 was added to 99 g of dechlorinated municipal water. Then, 1 g of an aqueous sodium nitrite solution diluted with a concentration adjustment in which the feed addition ratio became the value of Table 8 was added thereto. For this solution, the total chlorine concentration was measured immediately. The concentration of the active ingredient of the stabilized hypobromous acid-based slime controlling agent II can be determined as the total chlorine concentration by the DPD method. The results are shown in Table 8.

<Comparative Examples 29 to 34>

1 g of the stabilized hypobromous acid-based slime controlling agent II diluted and adjusted in such a manner that the total chlorine addition ratio (addition ratio in terms of total chlorine conversion) was added to the value of Table 8 was added to 99 g of dechlorinated municipal water. Then, 1 g of sodium hydrogen sulfite or an aqueous sodium sulfite solution diluted with a concentration adjustment in which the feed addition ratio became the value of Table 8 was added thereto. For this solution, the total chlorine concentration was measured immediately. The results are shown in Table 8.

As can be seen from Tables 7 and 8, even when a stabilized hypobromous acid-based slime controlling agent is used as the oxidizing drug, as long as it is nitrous acid (salt), decomposition of the oxidizing drug due to the residual reducing agent can be prevented.

As is clear from the results of the above examples and comparative examples, when nitrous acid (salt) is used as the reducing agent added for the reduction and removal of the residual oxidizing agent, even if it remains, the oxidizing drug added later does not undergo redox reaction. Therefore, the addition effect of the oxidizing drug is not impaired.

The present invention has been described in detail with reference to the specific embodiments thereof, and it is understood that various modifications are possible without departing from the spirit and scope of the invention.

Japanese Patent Application No. 2015-111487 filed on June 1, 2015, Japanese Invention Patent Application No. 2015-119401 filed on June 12, 2015, and Japanese Invention Patent Application No. The application is based on 2016-012615 and is invoked by reference. All.

1‧‧‧ original sink

2‧‧‧Filter device

3‧‧‧Filtering sink

4‧‧‧Safety filter

5‧‧‧RO membrane device

Claims (6)

A pretreatment method for a reverse osmosis membrane device, which is a pretreatment method for treating water containing an oxidant by a reverse osmosis membrane device reverse osmosis membrane, characterized in that nitrous acid and/or a salt thereof is added to the oxidant-containing water. The oxidant is removed by reduction. The pretreatment method of the reverse osmosis membrane device according to claim 1, wherein an oxidizing drug is added to the water after the addition of the nitrous acid and/or a salt thereof. The pretreatment method of the reverse osmosis membrane device according to claim 2, wherein in the water after the addition of the nitrous acid and/or a salt thereof, the reduction of the oxidizing agent remaining in the water or more is different from the reduction of nitrous acid and/or a salt thereof. After the agent, the aforementioned oxidizing drug is added. The pretreatment method of the reverse osmosis membrane device according to claim 2 or 3, wherein the oxidizing drug is selected from the group consisting of a salt of chloramine sulfonic acid, chloramine sulfonic acid, and a stabilized hypobromous acid-based slime controlling agent. One or two or more of the groups. The pretreatment method of the reverse osmosis membrane device according to claim 3 or 4, wherein the reducing agent different from nitrous acid and/or a salt thereof is selected from the group consisting of hydrogensulfite, sulfite and thiosulfate or 2 or more types. A water treatment device which is a water treatment device for treating a water containing an oxidizing agent by a reverse osmosis membrane, comprising: a reducing agent adding means for adding nitrous acid and/or a salt thereof to the oxidizing agent-containing water, and nitrous acid and/or Or an oxidizing drug added means for adding an oxidizing drug to the water after the salt is added, And a reverse osmosis membrane device for treating water with an oxidizing drug added thereto.