JP6299595B2 - Filtration membrane cleaning method - Google Patents

Description

The present invention relates to a method for cleaning a filtration membrane used for sewage or factory wastewater treatment.
This application claims priority on June 28, 2013 based on Japanese Patent Application No. 2013-137501 for which it applied to Japan, and uses the content here.

Generally, when water treatment is performed using a filtration membrane module, filtration is performed while repeating a filtration step and a washing step. When the wastewater treatment is performed using a filtration membrane in the filtration step, it is possible to remove contaminants such as suspended substances contained in the wastewater, and clear treated water is obtained.
However, when the wastewater is filtered through a filtration membrane, contaminant components adhere to the inside of the filtration membrane pores or on the surface of the filtration membrane, the filtration membrane is blocked, and the filtration resistance gradually increases.
On the other hand, when filtration is performed at a constant flow rate, it is necessary to increase the filtration pressure. Therefore, it is necessary to recover the filtration performance of the filtration membrane in the washing step before the filtration resistance becomes excessive and it becomes difficult to pass the drainage. In the cleaning process, the contaminant components are removed by physical and chemical cleaning. As a method of washing a filtration membrane having increased filtration resistance, reverse water is introduced by introducing treated water filtered through the filtration membrane from the treated water side of the filtration membrane to the raw water side, and discharging pollutant components from the pores of the filtration membrane. A cleaning method that removes contaminant components on the surface of the filtration membrane by rubbing the filtration membranes by swirling flow generated by bubbles generated by supplying gas to the raw water side of the membrane and the oscillation of the filtration membrane ( From Patent Document 1), a method of continuing filtration while restoring membrane performance is known. In addition, when these cleaning methods are repeated, contaminant components that cannot be removed accumulate. Therefore, a reverse liquid cleaning method using a cleaning agent (Patent Document 2) or a filtration membrane module is taken out from the system, and the cleaning agent is removed. A method of immersing and immersing in water is disclosed (Patent Document 3).

Japanese Unexamined Patent Publication No. 2010-69361 Japanese Patent Publication No. 6-65371 Japanese Unexamined Patent Publication No. 2001-294895

In general, when performing reverse flow cleaning using a cleaning agent as a method for cleaning a filtration membrane, in order to reduce the amount of cleaning liquid containing the cleaning agent and reduce the pressure difference between one side and the end side where the cleaning liquid is injected. In addition, it is often performed under low flux conditions.
However, when the raw water contains a component that inhibits the cleaning effect of the cleaning agent, the conventional method cannot provide a sufficient cleaning effect. In addition, in the method of injecting a cleaning liquid into the filtration membrane and cleaning the filtration membrane, if the raw water contains a component that reacts with a component in the cleaning liquid and generates bubbles, bubbles are generated in the filtration membrane. This causes a problem that the injected cleaning liquid does not reach the end of the filtration membrane. Further, the cleaning method for removing the filtration membrane module from the system is disadvantageous in terms of cost and work.
The present invention provides a membrane filter module in the system even when the raw water contains a component that inhibits the cleaning effect, or when a component that reacts with the cleaning agent component to generate bubbles is contained. It is an object of the present invention to provide a method for cleaning a filtration membrane that can sufficiently remove the contaminant components of the filtration membrane without removing from the filter.

  As a result of intensive studies in view of the above problems, the present inventor has included components that generate bubbles by reacting with the components of the cleaning agent when components that inhibit the cleaning effect are included in the raw water. In this case, the present inventors have found a method for cleaning a filtration membrane that can sufficiently remove contaminant components of the filtration membrane without removing the filtration membrane module from the system.

  That is, in the method for cleaning a filtration membrane of the present invention, a cleaning agent containing chloric acid or a salt thereof and a surfactant is reversely passed from the treated water side to the raw water side, and the permeation flux in the reversely passing liquid is 0. 15 to 3.0 m / d.

Moreover, it is preferable that the free chlorine concentration in the said cleaning agent is 0.01-3.0 mass%.
Moreover, it is preferable that the density | concentration of surfactant in the said cleaning agent is 0.05-3.0 mass%.
Moreover, it is preferable that the said cleaning agent contains an antifoamer.
Moreover, it is preferable that the mass concentration of the defoaming agent in the cleaning agent is 0.1 to 2 times the mass concentration of the surfactant.
Moreover, it is preferable to add an antifoamer in the processing tank which reversely flowed the said washing | cleaning agent.
The filtration membrane is preferably washed once / one day to once / 90 days.
The present invention has the following aspects.
(1) Back-flowing a cleaning agent containing chloric acids or salts thereof and a surfactant from the treated water side of the filtration membrane to the raw water side, and the permeation flux of the cleaning agent in the reverse-flowing solution is 0 A method for cleaning a filtration membrane of 15 to 3.0 m / d.
(2) The filtration membrane cleaning method according to (1), wherein the free chlorine concentration in the cleaning agent is 0.01 to 3.0% by mass with respect to the total mass of the cleaning agent.
(3) The method for cleaning a filtration membrane according to (1) or (2), wherein the concentration of the surfactant in the cleaning agent is 0.05 to 3.0% by mass with respect to the total mass of the cleaning agent.
(4) The filtration membrane cleaning method according to any one of claims (1) to (3), wherein the cleaning agent further contains an antifoaming agent.
(5) The method for cleaning a filtration membrane according to (4), wherein the mass concentration of the antifoaming agent in the cleaning agent is 0.1 to 2 times the mass concentration of the surfactant.
(6) The method for cleaning a filtration membrane according to any one of (1) to (3), further comprising adding an antifoaming agent to the raw water side reversely passed through the cleaning agent.
(7) The method for cleaning a filtration membrane according to any one of (1) to (6), wherein the filtration membrane is washed at a frequency of once / day to once / 90 days.
(8) The filtration according to any one of (1) to (7), wherein the filtration membrane is a filtration membrane used for treatment of raw water containing a substance that reacts with chloric acid or a salt thereof to generate bubbles. Method for cleaning the membrane.
(9) The filtration membrane cleaning method according to (8), wherein the substance that reacts with the chloric acid or a salt thereof to generate bubbles is ammonia.
(10) The method for cleaning a filtration membrane according to (9), wherein the ammonia content is 50 mg / L or more as ammonium nitrogen per unit volume of the raw water, which is a filtration membrane used for the raw water treatment.

  According to the filtration membrane cleaning method of the present invention, when raw water contains a component that inhibits the cleaning effect, or when it contains a component that reacts with the cleaning agent component to generate bubbles. However, the contaminant components of the filtration membrane can be sufficiently removed without removing the filtration membrane module from the system.

Hereinafter, the cleaning method for the filtration membrane of the present invention will be described in detail.
The method for cleaning a filtration membrane of the present invention includes reversely passing a cleaning agent containing chloric acids or salts thereof and a surfactant from the treated water side of the filtration membrane to the raw water side, and the cleaning solution in the reverse solution The filtration membrane has a permeation flux of 0.15 to 3.0 m / d.
Here, the permeation flux is represented by the amount of liquid that passes through the membrane per unit time per unit area of the filtration membrane, and can be obtained by the following equation.
Permeation flux (m / d) = permeate volume (m ³ ) / (measurement time (d) × membrane area (m ² ))
In the present specification, the unit time is one day, and the measurement time (d) is expressed in days.
In the present invention, the membrane area refers to the area of one of the membrane surfaces of the filtration membrane in either the hollow fiber membrane or the flat membrane. For example, when raw water is filtered from the outside of the hollow fiber membrane toward the inside of the membrane, it is the area of the outer membrane surface of the hollow fiber membrane, and the raw water is directed from the inside of the hollow fiber membrane to the outside of the membrane. When filtered, it is the area of the inner membrane surface of the hollow fiber membrane.
In this specification, the permeation flux (m / d) represents the permeation flux (m / d) at the temperature of the cleaning liquid during reverse flow.
One aspect of the present invention is that in a system for obtaining treated water with reduced pollutant components by filtering raw water containing pollutant components through a filter membrane, the filter membrane is used in the system, that is, from within the system. It is a method of cleaning without removing.
Another aspect of the present invention is a cleaning method in which the raw water contains activated sludge.
Another aspect of the present invention is a cleaning method including a substance that generates bubbles by reacting the raw water with a chloric acid such as ammonia or a salt thereof.
In the present specification, in the system, a section where raw water is mainly present is referred to as “raw water side” and a section where treated water is mainly present is sometimes referred to as “treated water side”. Further, the “raw water” may be diluted with water such as seawater, lake water, river water, rain water, etc. before being filtered through the filter membrane, and the “raw water” includes the diluted “raw water”.

The cleaning agent used in the present invention contains chloric acids or salts thereof and a surfactant. Examples of chloric acids or salts thereof include perchloric acid or salts thereof, chlorous acid or salts thereof, hypochlorous acid or salts thereof, and chlorine dioxide in addition to chloric acid or salts thereof.
Examples of chloric acid or salts thereof include sodium chlorate, potassium chlorate, ammonium chlorate, lithium chlorate, calcium chlorate, and salts thereof in addition to chloric acid.
As perchloric acid or a salt thereof, in addition to perchloric acid, for example, sodium perchlorate, potassium perchlorate, ammonium perchlorate, lithium perchlorate, magnesium perchlorate, calcium perchlorate, perchloric acid Examples thereof include tetraalkylammonium and a salt thereof.
Examples of chlorous acid or salts thereof include sodium chlorite, potassium chlorite, ammonium chlorite, magnesium chlorite, calcium chlorite, and salts thereof in addition to chlorous acid.
Examples of hypochlorous acid or a salt thereof include sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite, calcium hypochlorite, and salts thereof in addition to hypochlorous acid. .
Here, hypochlorous acid or a salt thereof is preferable from the viewpoint of detergency and handleability.
As the solvent contained in the cleaning agent, any solvent can be used as long as it can dissolve the cleaning agent component to be used, but it is preferable to use water from the viewpoint of ease of handling and safety as waste water after cleaning.
In one aspect of the present invention, the cleaning agent used in the present invention is an aqueous solution containing chloric acids or salts thereof and a surfactant.

The free chlorine concentration of the chloric acid or salt thereof in the cleaning agent is 0.01 to 3.0% by mass, preferably 0.02 to 2.5% by mass, based on the total mass of the cleaning agent. It is most preferable that it is 0.03-2.0 mass%. When the free chlorine concentration of chloric acids or salts thereof is less than the lower limit value, the filtration membrane is not sufficiently cleaned, and when the upper limit value is exceeded, it becomes difficult to treat the waste liquid after cleaning. The free chlorine in the cleaning agent means a chlorine component having an oxidizing ability. For example, chlorine (Cl ₂ ), hypochlorous acid (HClO), hypochlorite ion (ClO ⁻ ) dissolved in the cleaning liquid. And can be calculated by the DPD method described in JIS K 0102 (2008).

  The surfactant of the cleaning agent is selected depending on the type of plugging substance of the filtration membrane, etc. From the point of being excellent in the cleaning property of the filtration membrane, the cost merit and the handling property, it is a low foaming nonionic surfactant. An agent is more preferable. Moreover, you may mix 1 or more types of nonionic surfactant, anionic surfactant, cationic surfactant, and amphoteric surfactant.

  Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyalkylene ether such as polyoxyethylene-polyoxypropylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polystyryl phenyl ether, polyoxyethylene- Polyoxypropylene glycol, polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, polyoxyethylenated castor oil, fatty acid diethanolamide, polyoxyethylene alkylamine, Examples include triethanolamine fatty acid partial esters, trialkylamine oxides, etc., from the viewpoint of surfactant stability and membrane cleaning properties. It is preferably a polyoxypropylene alkyl ethers - polyoxyethylene.

  Examples of the anionic surfactant include alkylsulfonic acid, alkylbenzenesulfonic acid, alkylcarboxylic acid, alkylnaphthalenesulfonic acid, α-olefinsulfonic acid, dialkylsulfosuccinic acid, α-sulfonated fatty acid, N-methyl-N-oleyl taurine. , Petroleum sulfonic acid, alkyl sulfuric acid, sulfated oil, polyoxyethylene alkyl ether sulfuric acid, polyoxyethylene styrenated phenyl ether sulfuric acid, alkyl phosphoric acid, polyoxyethylene alkyl ether phosphoric acid, polyoxyethylene alkyl phenyl ether phosphoric acid, naphthalene Examples include sulfonic acid formaldehyde condensates and salts thereof.

  Examples of the cationic surfactant include primary to tertiary fatty amines, quaternary ammonium, tetraalkylammonium, trialkylbenzylammoniumalkylpyridinium, 2-alkyl-1-alkyl-1-hydroxyethylimidazolinium, N, Examples include N-dialkylmorpholinium, polyethylene polyamine fatty acid amide, urea condensate of polyethylene polyamine fatty acid amide, quaternary ammonium of urea condensate of polyethylene polyamine fatty acid amide, and salts thereof.

  Examples of the amphoteric surfactant include betaines (N, N-dimethyl-N-alkyl-N-carboxymethylammonium betaine, N, N, N-trialkyl-N-sulfoalkyleneammonium betaine, N, N-dialkyl- N, N-bispolyoxyethylene ammonium sulfate betaine, 2-alkyl-1-carboxymethyl-1-hydroxyethylimidazolinium betaine, etc.), aminocarboxylic acids (N, N-dialkylaminoalkylene carboxylate, etc.), etc. Is mentioned.

The concentration of the surfactant in the cleaning agent is preferably 0.05 to 3.0% by mass, more preferably 0.1 to 2.0% by mass, based on the total mass of the cleaning agent. It is most preferable that it is 3-1.5 mass%. If the surfactant concentration is equal to or higher than the lower limit, the filtration membrane can be sufficiently washed, but if the upper limit is exceeded, cost demerits increase. Moreover, activated sludge may be adversely affected.
Further, the ratio of the surfactant when the free chlorine concentration of chloric acid or a salt thereof is 1 (mass%) is not particularly limited, but higher detergency can be obtained. It is preferable that it is -1.5 (mass%).

As a method for cleaning the filtration membrane using the filtration membrane cleaning agent, for example, a liquid filtration membrane cleaning agent diluted with water to the above-mentioned concentration is placed in a container, and the treated water of the membrane by a pump or water head pressure is used. A method of reversely flowing from the side to the raw water side can be mentioned.
In the present invention, the permeation flux of the cleaning liquid containing the cleaning agent is 0.15 to 3.0 m / d. It is more preferably 0.2 to 2.8 m / d, further preferably 0.5 to 2.5 m / d, and most preferably 1.0 to 2.0 m / d. If the permeation flux is not less than the lower limit value, the filtration membrane can be sufficiently washed. However, if the upper limit is exceeded, the capacity of the pump increases, and the pressure applied to the filtration membrane becomes excessive, which may shorten the membrane life. Furthermore, if the permeation flow rate of the cleaning liquid is equal to or higher than the above upper limit value, the cleaning liquid may preferentially escape from the root on the cleaning liquid supply side of the filtration membrane to the raw water side, which may reduce the cleaning effect of the entire filtration membrane. is there.
In the case of the lower limit value or less, bubbles are generated in the membrane, so that the chemical solution does not reach the end of the filtration membrane, resulting in insufficient cleaning. Furthermore, while the filtration membrane is being washed, it is necessary to stop the raw water treatment of the filtration membrane. However, if it is equal to or lower than the lower limit value, the time required for washing becomes long, which may affect the raw water treatment.
In the present invention, it is preferable that the cleaning liquid is pressurized by the pump or the water head pressure so as to be the permeation flux and reversely passed through the filtration membrane. The permeation flow rate can be adjusted, for example, by controlling the pump pressure.

The amount of the cleaning liquid is preferably 1 to 5 L / m ² and more preferably ² to 4 L / m ² with respect to the membrane area of the filtration membrane. If the amount of cleaning liquid is less than or equal to the lower limit value, the amount of liquid is too small and the sufficient cleaning effect is small, and if it is greater than or equal to the upper limit value, the activated sludge may be adversely affected. In the present invention, if the amount of the cleaning liquid per unit area of the membrane area is in the above range, the filtration membrane is sufficiently cleaned.
Moreover, as one aspect of the present invention, the amount of cleaning liquid is an amount of cleaning liquid used per cleaning.

The frequency of cleaning the filtration membrane depending on the amount of the cleaning liquid is preferably 1 time / 90 days to 1 time / 1 day. Below the lower limit value, the membrane contaminants cannot be sufficiently removed, and stable operation cannot be performed. On the other hand, above the upper limit, not only will the activated sludge be adversely affected, but the life of the filtration membrane will be shortened by the cleaning liquid.
As one aspect of the present invention, the amount of the cleaning liquid is an amount of the cleaning liquid used per cleaning.

  Since the surfactant has high foaming properties, it is preferable to use an antifoaming agent in combination. As the concentration of the defoaming agent, the surfactant concentration in the activated sludge, that is, 0.1% by mass with respect to the concentration of the surfactant reversely passed through the raw water side of the filtration membrane or reversely passed through. It is preferably ˜2 times, more preferably 0.15 to 1.5 times, and most preferably 0.2 to 1 times. If the amount is not more than the lower limit, foaming by the surfactant cannot be sufficiently suppressed. If the amount is not less than the upper limit, not only the chemical cost is increased, but also the activated sludge is adversely affected.

The antifoaming agent is not particularly limited as long as it is not a substance that closes the filtration membrane such as silicon or mineral oil, and examples thereof include polyether antifoaming agents and higher alcohol defoaming agents.
The antifoaming agent can be added to the cleaning agent. The antifoaming agent can be added to the raw water separately from the cleaning agent. That is, one aspect of the present invention is a method for cleaning a filtration membrane, further comprising adding an antifoaming agent to the raw water side reversely passed through the treatment agent. The antifoaming agent can be added to the treatment tank separately from the cleaning agent. That is, another aspect of the present invention is a method for cleaning a filtration membrane, further comprising adding an antifoaming agent after reversely passing the treatment agent.
In this specification, the system which obtains the treated water by which the raw | natural water containing a pollutant component is filtered with a filtration membrane and the pollutant component was reduced is comprised in the processing tank provided with the filtration membrane module. The antifoaming agent can be added to the raw water side in the treatment tank.

  Further, since the quality of the treated water deteriorates when the cleaning agent remains in the treated water, it is preferable to treat the detergent in the treated water separately. Examples of the treatment method include bringing the treated water into contact with activated carbon or zeolite and adsorbing or decomposing the cleaning agent in the treated water, or bringing the treated water into contact with an oxidation catalyst and oxidizing the cleaning agent. . Moreover, you may use the method of diluting by returning treated water to the raw | natural water side. In the present invention, it is more preferable to treat with activated carbon from the viewpoint of cost and stability.

The filtration membrane may be a hollow fiber membrane or a flat membrane. Examples of the material of the filter membrane include fluorine resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), cellulose resins such as cellulose acetate, polyolefin resins, polysulfone resins, and crosslinked polyamides. Resin. Moreover, you may contain hydrophilic polymers, such as polyvinylpyrrolidone and polyvinyl alcohol, as an additive. Among these, in the case of a hollow fiber membrane, clogging in the filtration membrane due to bubbles is likely to occur, and the effect is particularly exhibited.
In one aspect of the present invention, the filtration membrane is a filtration membrane used for treatment of raw water containing a substance that reacts with chloric acid or a salt thereof to generate bubbles.
Examples of the substance that reacts with the chloric acid or a salt thereof to generate bubbles include substances that generate gas by oxidation of ammonia and the like, and reducing substances such as sodium sulfite and sodium thiosulfate. Is preferred.
As one aspect of the present invention, the ammonia content is 800 g / L or more as ammonium nitrogen relative to the unit volume of raw water, and as another aspect, the ammonia content is relative to the unit volume of raw water. It is 1000 g / L or more as ammonium nitrogen, and, as another aspect, the ammonia content is 1200 g / L or more as ammonium nitrogen per unit volume of raw water.
Further, the ammonia content is 50 g / L or more as ammonium nitrogen relative to the volume of the raw water, and as another aspect, the ammonia content is 60 g / L as ammonium nitrogen relative to the unit volume of the raw water. In yet another aspect, the ammonia content is 70 g / L or more as ammonium nitrogen per unit volume of raw water.
Here, ammonium nitrogen (NH ₄ -N) is nitrogen contained as ammonium ion or ammonium salt in water, and its content is determined by indophenol blue absorptiometry (JIS K 0102 (2008)). Can be measured. Moreover, it is not limited only to the above measuring method, the Nessler method, salicylic acid method, it is possible to determine the content of the ammonium nitrogen in the salicylate method (NH 4 _-N).

Further, the type of the surfactant may be appropriately changed depending on the type of the occluding substance in the cleaning agent, and an acid may be added.
According to another aspect of the present invention, the acid is not added to the cleaning agent, and the acid is reversely passed through the filtration membrane before the cleaning agent is passed through the filtration membrane. Backflow of the cleaning agent through the filtration membrane.

In particular, cleaning with an acid is often effective for removing contaminants mainly composed of inorganic substances.
The acid used for the acid cleaning may be either an organic acid or an inorganic acid, and the acid concentration of these solutions is preferably 0.1 to 2.0 mol / L.
Examples of the organic acid include formic acid, acetic acid, citric acid, and oxalic acid.
Examples of the inorganic acid include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, and the like.

  As described above, according to the present invention, even when the raw water contains a component that inhibits the cleaning effect, or when it contains a component that reacts with the cleaning agent component to generate bubbles. The contaminant components of the filtration membrane can be sufficiently removed without removing the filtration membrane module from the system.

Here, examples of components that generate bubbles by reacting with a cleaning inhibiting component or a cleaning agent include substances that generate gas by oxidation such as ammonia, and reducing substances such as sodium sulfite and sodium thiosulfate.
In one aspect of the present invention, the water permeability retention rate of the filtration membrane washed by the filtration membrane washing method of the invention is such that the concentration of a substance that generates bubbles by reacting with chloric acid or its salt in raw water is 800 mg / Even within the range of not less than L and not more than 1200 mg / L, it recovers to 30% to 85%, preferably recovers to 50% to 85%, and most preferably recovers to 65% to 85%.
In another aspect of the present invention, the filtration performance retention rate of the filtration membrane washed by the filtration membrane washing method of the invention is such that the concentration of a substance that generates bubbles by reacting with chloric acids or its salts in raw water is 50 mg / Even within the range of not less than L and not more than 70 mg / L, it recovers to 70% to 85%, preferably recovers to 75% to 85%.
Here, as will be described later, the water permeation performance retention rate was measured by allowing pure water pressurized to 100 kPa (gauge pressure) to permeate from the outside to the inside of the filtration membrane, and [(the hollow fiber membrane after washing Permeated water amount / (permeated water amount of unused hollow fiber membrane)] × 100 (%).
One aspect of the present invention includes reversely passing a cleaning agent containing hypochlorous acid or a salt thereof and a nonionic surfactant from the treated water side to the raw water side of the hollow fiber membrane, In which the permeation flux of the cleaning agent is 0.15 to 3.0 m / d.
Another aspect of the present invention is hypochlorous acid or a salt thereof and polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether such as polyoxyethylene polystyryl phenyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene-polyoxy Propylene glycol, polyoxyethylene-polyoxypropylene alkyl ether, polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, polyoxyethylenated castor oil, fatty acid diethanolamine And at least one selected from the group consisting of polyoxyethylene alkylamine, triethanolamine fatty acid partial ester and trialkylamine oxide A reverse flow of the cleaning agent containing the nonionic active agent from the treated water side to the raw water side of the hollow fiber membrane, and the permeation flux of the cleaning agent in the reverse flow rate is 0.15 to 3.0 m / This is a method for cleaning a filtration membrane which is d.
Another aspect of the present invention is that a cleaning agent containing hypochlorous acid or a salt thereof and a nonionic surfactant (a light oil hunter manufactured by Kyoeisha Chemical Co., Ltd.) is reversely passed from the treated water side of the hollow fiber membrane to the raw water side. The filtration membrane cleaning method is a filtration membrane cleaning method, wherein the permeation flux of the cleaning agent in the reverse flow is 0.15 to 3.0 m / d.
Another aspect of the present invention relates to hypochlorous acid or a salt thereof and polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether such as polyoxyethylene polystyryl phenyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene-poly Oxypropylene glycol, polyoxyethylene-polyoxypropylene alkyl ether, polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, polyoxyethylenated castor oil, fatty acid At least selected from the group consisting of diethanolamide, polyoxyethylene alkylamine, triethanolamine fatty acid partial ester and trialkylamine oxide. Back flow of a cleaning agent containing one nonionic active agent from the treated water side of the hollow fiber membrane to the raw water side, and the permeation flux of the cleaning agent in the reverse flow is 0.5-2. This is a method for cleaning a filtration membrane of 0 m / d.
Another aspect of the present invention relates to hypochlorous acid or a salt thereof and polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether such as polyoxyethylene polystyryl phenyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene-poly Oxypropylene glycol, polyoxyethylene-polyoxypropylene alkyl ether, polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, polyoxyethylenated castor oil, fatty acid At least selected from the group consisting of diethanolamide, polyoxyethylene alkylamine, triethanolamine fatty acid partial ester and trialkylamine oxide. Backflow of a cleaning agent containing one type of nonionic active agent from the treated water side to the raw water side of the hollow fiber membrane, and the permeation flux of the cleaning agent in the reverse flow is 1.0-2. This is a method for cleaning a filtration membrane of 0 m / d.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, a following example does not limit the scope of the present invention.

Example 1
A hollow fiber membrane element (Mitsubishi Rayon Co., Ltd. Stella Pore SADF) is fixed to a structure (hereinafter referred to as a module) having an air diffuser and a membrane filtered water collection part. It was immersed in the water tank which entered. With the diffuser connected to the blower, the membrane element and the suction pump, the blower was activated and the air was diffused, and then the suction pump was activated and the factory wastewater purification test was conducted. As industrial wastewater, ammonium nitrogen (NH ₄ -N) is 2,100 to 3,000 mg / L, COD _Mn is 3,500 to 4,700 mg / L, COD _Cr is 3,000 to 5,000 mg / L, Wastewater generated by a coking process having a TOC of 1,000 to 2,000 mg / L, a chromaticity of 400 to 800, and a normal hexane extract of 10 to 15 mg / L was used as raw water.
What diluted the said raw | natural water about 3 times using seawater was used as to-be-processed water in a present Example. This raw water has Ca ²⁺ of 70 to 200 mg / L, NH ₄ —N of 800 to 1,200 mg / L, COD _Mn of 950 to 1,450 mg / L, COD _Cr of 600 to 1,700 mg / L, TOC of It contained 300-700 mg / L, the chromaticity was 130-300, and the normal hexane extract showed 3-5 mg / L.
Using the treated water, purification treatment was performed for 3 months under the condition that the permeation flux of the hollow fiber membrane module having a membrane area of 18 m ² was 0.1 to 1.0 m / d. Next, about 70 cm of a hollow fiber membrane was cut out from the pulled membrane element, and this was used as a test membrane.
Pure water is added to the washing tank, and further, sodium hypochlorite (manufactured by Matsudo Co., Ltd.) having a free chlorine concentration of 12% is used as a stock solution. It diluted so that surfactant concentration might be 1.5 mass%, and the washing | cleaning liquid was adjusted. Here, a nonionic surfactant (Light Oil Hunter manufactured by Kyoeisha Chemical Co., Ltd.) was used as the surfactant. The free chlorine concentration was measured by the DPD method described in JIS K 0102 (2008). Specifically, a value calculated by a free chlorine measurement kit (HACH Pocket Colorimeter) was used.
Subsequently, the lower end of the test membrane was sealed, and the test membrane was stretched in the activated sludge containing the raw water and fixed in a suspended state so that the hollow fiber membrane portion was completely immersed. The cleaning agent was passed through the cleaning liquid with a permeation flux of ² L / m ² of 0.2 m / d from the upper end of the hollow fiber membrane module using a pump. Thereafter, the pump was stopped and allowed to stand.
About the hollow fiber membrane module before washing | cleaning and after washing | cleaning, the permeated water amount was measured by making the pure water pressurized to 100 kPa (gauge pressure) permeate | transmit the inside from the outer side of a hollow fiber membrane. And the water-permeable performance retention was calculated | required from the formula [(Amount of permeated water of the hollow fiber membrane after washing) / (Amount of permeated water of unused hollow fiber membrane)] × 100 (%). Table 1 shows the results of water permeability retention. In addition, it means that the filtration performance recovered | restored by washing | cleaning, so that water permeability performance retention rate is high.

(Examples 2 to 5)
The hollow fiber membrane was washed in the same manner as in Example 1 except that the permeation flux was changed to 0.3 to 2.0 m / d, and the water permeability retention rate was determined. Table 1 shows the results of water permeability retention.

(Examples 6 to 10)
The pH of the water to be treated is adjusted to 11 using a sodium hydroxide solution, and NH ₄ —N in the raw water is adjusted to 60 mg / L by bubbling using air, and then the pH is adjusted using a hydrochloric acid solution. The hollow fiber membrane was washed in the same manner as in Example 1 except that the activated sludge liquid containing raw water adjusted to 7 to 8 was used, and the water permeability retention rate was determined.
Table 1 shows the results of water permeability retention.

(Comparative Example 1)
Except for changing the permeation flux to 0.1 m / d, the hollow fiber membrane was washed in the same manner as in Examples 1 to 5, and the water permeability retention rate was determined.
Table 1 shows the results of water permeability retention.

(Comparative Example 2)
Except for changing the permeation flux to 0.1 m / d, the hollow fiber membrane was washed in the same manner as in Examples 6 to 10, and the water permeability performance retention was determined.
Table 1 shows the results of water permeability retention.

Examples 1 to 5 where the permeation flux is 0.15 to 3.0 m / d are the same when reverse flow cleaning is performed in activated sludge containing a large amount of ammonium nitrogen (NH ₄ -N). Even with the amount of washing liquid, the water permeability after filtration membrane washing could be recovered effectively. On the other hand, in Comparative Example 1 having a low permeation flux, the water permeation performance could hardly be recovered.
Moreover, when performing reverse flow cleaning in a property sludge containing a small amount of ammonium nitrogen (NH ₄ -N), Examples 6 to 10 having a permeation flux of 0.15 to 3.0 m / d are: The water permeability was successfully restored. On the other hand, in the comparative example 2 with a low permeation | transmission flow rate, the water-permeable performance retention rate was low compared with Examples 6-10.

  According to the filtration membrane cleaning method of the present invention, when raw water contains a component that inhibits the cleaning effect, or when it contains a component that reacts with the cleaning agent component to generate bubbles. However, the contaminant components of the filtration membrane can be sufficiently removed without removing the filtration membrane module from the system.

Claims (9)

Back flow of a cleaning agent containing chloric acids or salts thereof and a surfactant from the treated water side of the filtration membrane to the raw water side, and the permeation flux of the cleaning agent in the reverse flow rate is 0.15 to 0.15. 3.0m / d der is,
The filtration membrane, chlorine acids or method for cleaning a filtration membrane der Ru filtration membrane used in the raw water treatment containing a substance that generates the reaction was bubbles and salts thereof.   The method for cleaning a filtration membrane according to claim 1, wherein the concentration of free chlorine in the cleaning agent is 0.01 to 3.0% by mass with respect to the total mass of the cleaning agent.   The method for cleaning a filtration membrane according to claim 1 or 2, wherein the concentration of the surfactant in the cleaning agent is 0.05 to 3.0 mass% with respect to the total mass of the cleaning agent.   The method for cleaning a filtration membrane according to any one of claims 1 to 3, wherein the cleaning agent further contains an antifoaming agent.   The method for cleaning a filtration membrane according to claim 4, wherein the mass concentration of the antifoaming agent in the cleaning agent is 0.1 to 2 times the mass concentration of the surfactant.   The method for cleaning a filtration membrane according to any one of claims 1 to 3, further comprising adding an antifoaming agent to the raw water side through which the cleaning agent is reversely passed.   The filtration membrane cleaning method according to any one of claims 1 to 6, wherein the filtration membrane is washed at a frequency of once / day to once / 90 days. The method for cleaning a filtration membrane according to any one of claims 1 to 7 , wherein the substance that reacts with the chloric acid or a salt thereof to generate bubbles is ammonia. The method for cleaning a filtration membrane according to claim 8 , wherein the ammonia content is 50 mg / L or more as ammonium nitrogen with respect to a unit volume of the raw water.