JP2010022896A - Method of recovering performance of reverse osmosis membrane and method for membrane separation treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of recovering performance of reverse osmosis membrane and a method for membrane separation treatment capable of stably operating a reverse osmosis (RO) membrane apparatus by effectively removing a slime on the reverse osmosis membrane in which a differential pressure is raised because of the deterioration of performance due to membrane separation in an acidic condition to efficiently recover membrane separation performance so that the differential pressure is reduced, with a simple configuration and operations. <P>SOLUTION: Upon the membrane separation of acidic liquid to be processed by using the RO apparatus 1, when the RO membrane 2 decreases in performance, the liquid to be processed is replaced with a cleaning liquid, or alkali is introduced without replacement, a cleaning agent containing an enzyme agent is brought into contact with the RO membrane, thereafter, the RO membrane 2 is washed with an alkaline aqueous solution and pure water to recover its performance, thereby the membrane separation is performed by using the recovered RO apparatus 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reverse osmosis membrane performance recovery method for membrane separation treatment of an acidic treatment liquid, and a membrane separation treatment method using a reverse performance reverse osmosis membrane, and in particular, reverse from an acidic treatment liquid containing phosphoric acid. The present invention relates to a membrane separation treatment method and a reverse osmosis membrane performance recovery method suitable for a method of recovering phosphoric acid using an osmosis membrane.

  An etching solution containing phosphoric acid is used for etching liquid crystal substrates, wafers, and other electronic devices. The high-concentration waste etchant generated in the etching process is recovered and recycled, but the electronic equipment after etching is washed with pure water, and a large amount of low-concentration washing wastewater is generated. Such cleaning wastewater contains phosphoric acid, nitric acid, acetic acid, other acid components, etc., which are components of the etching solution, as well as metal ions, organic substances, and other impurities eluted by etching. It is water.

  Such etching cleaning wastewater is conventionally mixed with other wastewater or treated by coagulation sedimentation or ion exchange, but there are problems such as large amount of chemicals used and complicated operation. was there. As a method for solving this problem, phosphoric acid and water are recovered with high purity by membrane separation treatment with a reverse osmosis membrane. However, this method treats acidic liquids containing nutrients such as phosphoric acid, nitric acid, acetic acid, and organic matter, so that slime mainly composed of filamentous fungi and other microorganisms is generated, causing clogging, and the inhibition rate. There is a problem that the membrane separation performance such as flux and flux is lowered and the differential pressure is increased.

  As countermeasures against slime in general equipment, sterilization, addition of antibacterial agents, irradiation with UV, gamma rays, etc., high temperature treatment, removal of organic substances serving as food are known. However, in these methods, the adverse effect on the reverse osmosis membrane such as clogging due to oxidation, chemical adsorption or alteration is great, the performance of the reverse osmosis membrane decreases, the purity of the recovered phosphoric acid due to the additive agent decreases, the equipment cost, There are problems such as high operating costs, high energy consumption, and inefficiency in removing slime once generated.

  The slime once produced remains in a clogged state even if the causative microorganism is sterilized, and the membrane separation performance of the reverse osmosis membrane does not recover. Chlorine and oxidizers such as hydrogen peroxide used for slime stripping in cooling water systems cannot be used because they degrade the reverse osmosis membrane itself. Therefore, as a countermeasure against the slime once generated, alkali immersion, air flushing and the like were carried out, but no effect was seen.

Patent Document 1 (Japanese Patent No. 2663141) proposes a method in which an ion exchange membrane is brought into contact with a cleaning agent for ion exchange membranes containing chitinase as a method for removing deposits on the ion exchange membrane. The ion exchange membrane used here is composed of a cation exchange membrane and an anion exchange membrane that allow permeation of the cation and anion constituting the salinity in order to remove salt by electrodialysis of seawater, It cannot be applied to the removal of slime from reverse osmosis membranes with different processing conditions and slime generation conditions.
Japanese Patent No. 2663141

  The object of the present invention is to efficiently remove the slime of the reverse osmosis membrane whose performance has been reduced due to the membrane separation treatment under acidic conditions and the differential pressure has been increased by a simple configuration and operation, and the membrane separation performance can be effectively improved. In other words, the present invention proposes a reverse osmosis membrane performance recovery method and a membrane separation treatment method that can restore the pressure to reduce the differential pressure and stably operate the reverse osmosis membrane device.

The present invention is the following reverse osmosis membrane performance recovery method and membrane separation treatment method.
(1) A method for recovering the performance of a reverse osmosis membrane, characterized in that, in a method for subjecting an acidic liquid to be treated with a reverse osmosis membrane, the reverse osmosis membrane having a reduced performance is brought into contact with a cleaning solution containing an enzyme agent.
(2) The method according to (1) above, wherein the reverse osmosis membrane is washed by introducing an alkali before or after bringing the reverse osmosis membrane into contact with a cleaning solution containing an enzyme agent.
(3) In a method of membrane separation treatment of an acidic liquid to be treated with a reverse osmosis membrane,
At the time when the performance of the reverse osmosis membrane deteriorates, the treatment liquid is replaced with the cleaning liquid, or alkali is introduced without replacement, and after the cleaning agent containing the enzyme agent is brought into contact with the reverse osmosis membrane,
The reverse osmosis membrane is washed with an alkaline aqueous solution and pure water to restore performance.
A membrane separation treatment method comprising performing membrane separation treatment using a reverse osmosis membrane whose performance has been recovered.
(4) The method according to any one of (1) to (3) above, wherein when the reverse osmosis membrane is brought into contact with a cleaning liquid containing an enzyme agent, a part of the cleaning liquid is permeated through the reverse osmosis membrane.
(5) The method according to any one of (1) to (4) above, wherein the liquid to be treated is an effluent containing phosphoric acid.
(6) The method according to any one of (1) to (5) above, wherein the enzyme agent contains an enzyme having a chitinolytic action.

  In the present invention, the liquid to be treated for membrane separation treatment is an acidic liquid to be treated, and examples thereof include waste liquid containing phosphoric acid. As an example of such an acidic liquid to be treated containing phosphoric acid, there is an electronic equipment cleaning waste water after etching, in addition to etching liquid components such as phosphoric acid, nitric acid, acetic acid, other acid components, etc. It contains eluted metal ions, organic substances, and other impurities, but most is pure water.

  An acidic liquid to be treated containing phosphoric acid such as electronic equipment cleaning wastewater contains 50 to 10000 mg / L of phosphate ions, particularly 50 to 2000 mg / L, and has a pH of 3 or less, particularly 2.8 or less, In any case, acidic water of 1 or more, particularly 1.8 or more, is targeted for membrane separation treatment. In addition to phosphate ions, acid components such as nitrate ions and acetate ions, other anions, metal ions, etc. Cations, organic substances, and other impurities may be contained. Examples of the cleaning waste water after etching include acidic water having a pH of 1.8 to 2.8, containing phosphate ions 50 to 2000 mg / L, nitrate ions 10 to 500 mg / L, and acetate ions 5 to 300 mg / L. .

  By subjecting such an acidic liquid to be processed to membrane separation, it is possible to separate and recover an active component such as an acid component and pure water contained in the liquid to be processed. When recovering phosphorus and pure water from phosphoric acid-containing water, the phosphoric acid-containing water is supplied to the reverse osmosis membrane device under conditions of pH 3 or lower and phosphoric acid concentration of 1 to 15% by weight, and membrane separation is performed by the reverse osmosis membrane. By performing the treatment, pure water is recovered by allowing the solvent water to permeate the permeate chamber side, and phosphoric acid or the like is concentrated and recovered to the concentrate chamber side.

  In the present invention, the reverse osmosis device in the membrane separation step is also called an RO device, and is divided into a permeate chamber and a concentrate chamber by a reverse osmosis (RO) membrane. On the concentrated liquid chamber side of the reverse osmosis membrane device, a liquid to be processed supply section for supplying the liquid to be processed and a concentrated liquid extraction section for extracting the concentrated phosphoric acid liquid are formed. On the side of the permeate chamber of the reverse osmosis membrane device, a permeate extractor for taking out the permeate is formed. A circulation path for circulating the concentrated liquid extracted from the concentrated liquid extracting section to the concentrated liquid chamber side is formed between the concentrated liquid extracting section and the liquid to be treated supplying section. Reverse osmosis membranes allow water to permeate by osmotic pressure, or conversely, pressurize to a pressure higher than osmotic pressure and supply the liquid to be treated to allow water to permeate by reverse osmosis, while not allowing salt and other solutes to permeate. A semi-permeable membrane to block.

  The material of the reverse osmosis membrane is not particularly limited as long as it has the above characteristics, and examples thereof include a polyamide-based permeable membrane, a polyimide-based permeable membrane, and a cellulose-based permeable membrane. A composite reverse osmosis membrane in which an active skin layer having substantially selective separability is formed on a support is preferred. The reverse osmosis device may be any device that includes such a reverse osmosis membrane, but preferably includes a membrane module in which a reverse osmosis membrane, a support mechanism, a water collection mechanism, and the like are integrated. There is no restriction | limiting in particular as a membrane module, For example, a tubular membrane module, a plane membrane module, a spiral membrane module, a hollow fiber membrane module etc. can be mentioned. As the reverse osmosis apparatus provided with these, a known apparatus can be used, and a highly permeable apparatus operated at a low pressure is preferable.

  When a membrane separation treatment is performed by supplying an acidic liquid to be treated such as phosphoric acid-containing water to a reverse osmosis device under a condition of pH 3 or lower, acids other than phosphoric acid such as nitric acid and acetic acid, together with water, are reverse osmosis membranes. Is transferred to the permeate chamber side and taken out from the permeate chamber side. Since phosphoric acid is prevented from permeating through the reverse osmosis membrane and remains on the concentrate chamber side to be concentrated, it can be recovered from the concentrate chamber side as a phosphoric acid concentrate. The pressure of the phosphoric acid containing water supplied to a reverse osmosis apparatus can be 0.3-5 Mpa, Preferably it can be 0.5-3 Mpa.

  When such an acid treatment liquid is subjected to membrane separation treatment with such a reverse osmosis membrane apparatus, the acid treatment liquid containing nutrient components such as phosphoric acid, nitric acid, acetic acid, and organic matter is concentrated. Slime mainly composed of microorganisms is generated in the vicinity of the reverse osmosis membrane, causing clogging, and the membrane separation performance such as the blocking rate and the flux is lowered and the differential pressure is increased. In the reverse osmosis membrane device, the solvent liquid permeates through the reverse osmosis membrane by pressurization, and the solute acid and other substances are concentrated on the concentration side of the reverse osmosis membrane. The processing conditions, slime generation conditions, and the like are different from the processing with a film that transmits water but does not transmit liquid.

  In the reverse osmosis membrane device, the solvent liquid permeates through the reverse osmosis membrane, and solute acids and other substances are concentrated on the concentration side of the reverse osmosis membrane, so slime is generated on the concentration side and part of the liquid permeation. Along with this, it is presumed to spread inside the network structure of the reverse osmosis membrane. The slime produced under acidic conditions is mainly composed of filamentous fungi and other microorganisms, and has a cell wall mainly composed of chitin. When slime is formed on the surface of an ion exchange membrane as in Patent Document 1, it is possible to remove the slime by degrading chitin with an enzyme and restore the performance. When the slime spreads inside the network structure of the film, even if the slime on the surface is removed, the internal slime remains and the film performance cannot be recovered.

  The slime produced by microorganisms mainly composed of filamentous fungi under acidic conditions mainly contains chitin, but contains high molecular organic substances such as proteins. However, organic substances such as proteins and polysaccharides remain inside the reverse osmosis membrane network structure, preventing complete recovery of membrane performance. Therefore, when the reverse osmosis membrane whose performance has been lowered is brought into contact with a cleaning solution containing an enzyme agent, or before or after it is washed by introducing an alkali, it is possible to promote the removal of high-molecular organic substances such as proteins and polysaccharides. it can. When the reverse osmosis membrane is brought into contact with the cleaning solution containing the enzyme agent, if a part of the cleaning solution is allowed to permeate the reverse osmosis membrane, the enzyme agent is concentrated on the membrane surface, and the slime inside the membrane is efficiently dissolved. can do.

  For this reason, in the present invention, the reverse osmosis membrane whose performance has been lowered is brought into contact with a cleaning solution containing an enzyme agent to remove slime generated in the module of the reverse osmosis membrane, thereby recovering the reduced membrane separation performance. Reduce the differential pressure. At this time, when the reverse osmosis membrane is brought into contact with a washing solution containing an enzyme agent, or before or after washing with alkali, the removal of organic substances such as proteins and polysaccharides is promoted and the membrane separation performance is restored. Effectively.

  The procedure for recovering the membrane separation performance by removing the slime from the reverse osmosis membrane is as follows. First, since the liquid crystal production wastewater is acidic at a pH of about 2, in order to adjust the pH to water that is easy for enzymes to work and pH, an alkali such as a sodium hydroxide solution is added and stirred in the reverse osmosis membrane device to adjust the pH to 4-8. adjust. Subsequently, the enzyme agent is added and diluted, the valve is switched to the washing line, and the cleaning solution containing the pH-adjusted enzyme agent is circulated on the primary side of the reverse osmosis membrane module, and a part of the washing solution permeates through the reverse osmosis membrane. Then, it is allowed to stand for several hours to several days, and the slime adhering to the reverse osmosis membrane module is dissolved. Thereafter, pure water is introduced into the reverse osmosis membrane device, the enzyme solution in which the slime is dissolved is extruded, and pure water is further introduced and washed. Thereafter, a dilute alkaline aqueous solution of 0.01 to 0.1% by weight sodium hydroxide is introduced for washing, and pure water is further introduced for washing. In addition, it is also possible to make a washing | cleaning liquid contact with a reverse osmosis membrane, without permeate | transmitting.

  Although the washing operation of the reverse osmosis membrane device is completed as described above, the membrane separation performance of the reverse osmosis membrane is recovered and the differential pressure is reduced. For this reason, the permeated water is recovered as pure water and the phosphoric acid is concentrated and recovered by passing an acidic liquid such as liquid crystal production wastewater through the reverse osmosis membrane device and restarting the membrane separation treatment. . The above-described washing operation of the reverse osmosis membrane device can be performed periodically or at any time when the performance of the reverse osmosis membrane is deteriorated.

  The enzyme used in the present invention is preferably an enzyme having a chitinolytic action. Chitin is the major structural polysaccharide in many invertebrates, including fungi, and insects. Therefore, chitin synthesis and metabolic processes are extremely important for the life support and growth of these invertebrates. In the present invention, the reverse osmosis membrane whose performance has been reduced is brought into contact with an enzyme agent having a chitin-degrading action, thereby decomposing chitin, making it difficult to maintain the life of microorganisms constituting the slime, and destroying debris. To do.

  As an enzyme having a chitin degrading action, chitinase involved in the metabolic process of chitin is known. This chitinase is widely distributed in fungi, insects, mites, nematodes and the like, and is an essential enzyme for these. Chitin is a glycoprotein complex composed of an N-acetylglucosamine polymer and protein, and chitinase decomposes this polymer into N-acetylglucosamine monomers. That is, the cell walls of mold and yeast are chitin and are destroyed by chitinase.

  The addition amount of the enzyme having a chitin decomposing action to be added to the cleaning liquid is an amount capable of decomposing and removing slime in the cleaning step, and generally has a chitinase concentration of 0.001 to 50% by weight, preferably 0.1 to 0.1%. About 5% by weight. In addition to chitinase, enzymes that can be used in the present invention include commercially available enzymes that exhibit chitobiase activity, glucanase activity, cellulase activity, etc. (for example, YL-NL “Amano”, Cellulase A “Amano” manufactured by Amano Enzyme Co., Ltd.). 3 and hemicellulase “Amano” 90; Tunicase FN and Samoaase PC10F manufactured by Daiwa Kasei Co., Ltd .; Yatalase, Westase and Labiase manufactured by Ozeki Co., Ltd .; It is recognized that Akon CHL (manufactured by Co., Ltd.) and the like have an effect of dissolving slime, which is considered to be because chitinase is contained in these enzymes.

  In the present invention, when the reverse osmosis membrane is brought into contact with a washing solution containing an enzyme agent, or before or after washing with alkali, the removal of organic substances such as proteins and polysaccharides is promoted, and membrane separation performance However, when the reverse osmosis membrane is brought into contact with a cleaning solution containing an enzyme agent, an alkali is introduced and the alkali is added to the liquid to be treated to adjust the pH to a value suitable for the enzyme to work. In addition, the enzyme can be made easier to work and the decomposition of the slime can be promoted.

  In addition, by contacting with a cleaning solution containing an enzyme agent and then washing with an alkali, organic substances such as residual proteins and polysaccharides are removed, and enzymes (proteins) are also removed. This prevents these residues from becoming mold, yeast, and other fungal baits on the reverse osmosis membrane surface, further preventing slime from growing and growing and reducing membrane performance, and increasing the washing interval. Can do. Thereafter, it is possible to prevent the purity of the recovered phosphoric acid from being lowered by washing with water and removing the alkali component.

  As described above, according to the present invention, in the method of membrane separation treatment of an acidic liquid to be treated with a reverse osmosis membrane, the reverse osmosis membrane whose performance has been reduced is brought into contact with a washing solution containing an enzyme agent and washed. Reverse osmosis membrane device that effectively removes slime from reverse osmosis membrane whose pressure drop has been increased due to the performance of membrane separation under the conditions, effectively recovering membrane separation performance and lowering differential pressure Can be operated stably.

  According to the membrane separation treatment method of the present invention, since the membrane separation treatment is performed with the reverse osmosis membrane whose performance has been recovered in this way, the acidic component liquid is efficiently subjected to the membrane separation treatment to remove the acid component and the pure water. It can be recovered and the membrane separation process can be performed stably.

  Furthermore, in the present invention, when the reverse osmosis membrane is brought into contact with a washing solution containing an enzyme agent, or before or after washing by introducing alkali, slime-derived proteins, organic substances such as polysaccharides are removed, Residual enzymes and proteins can also be removed, thereby further improving the slime removal effect, promoting the recovery of the membrane performance, and increasing the washing interval.

  Moreover, in this invention, when making a reverse osmosis membrane contact with the washing | cleaning liquid containing an enzyme agent, a part of washing | cleaning liquid permeate | transmits a reverse osmosis membrane, and can dissolve and remove even the slime inside a reverse osmosis membrane.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart of a membrane separation processing apparatus using a reverse osmosis (RO) membrane apparatus in the embodiment.
In FIG. 1, reference numeral 1 denotes an RO device, which is divided into a permeate chamber 3 and a concentrate chamber 4 by an RO membrane 2. Reference numeral 5 denotes a liquid tank to be processed, which stores the liquid 6 to be processed. Reference numeral 7 denotes a cleaning liquid tank which stores the cleaning liquid 8 and includes a stirrer 9 and a pH meter 10.

  In the above membrane separation processing apparatus, the liquid 6 to be processed is introduced from the line L1 to the liquid tank 5 to be processed, the valves V1, V2, V3, V4 are opened and pressurized by the pressure pump P1, and the RO apparatus from the line L2. 1 is supplied to the concentrated liquid chamber 4 and subjected to membrane separation treatment, water as a solvent is permeated to the permeated liquid chamber 3 side, and solutes such as phosphoric acid are concentrated to the concentrated liquid chamber 4 side. Acids other than phosphoric acid such as nitric acid and acetic acid contained in the liquid to be treated 6 may or may not permeate depending on the pH, phosphoric acid concentration, etc. of the liquid to be treated 6.

  The permeate in the permeate chamber 3 is taken out from the line L3, and impurities such as permeated nitric acid and acetic acid are removed as necessary to recover pure water. A part of the concentrated liquid in the concentrated liquid chamber 4 is circulated through the line L4 as necessary, and another part is taken out from the line L5, and if necessary, impurities such as nitric acid and acetic acid remaining are removed to remove phosphoric acid. to recover. Whether or not the concentrated liquid is circulated from the line L4 to the liquid tank 5 to be processed and the amount thereof are determined by the properties of the liquid 6 to be processed, the configuration of the system, and the like.

  When the acidic liquid 6 is subjected to membrane separation treatment with such an RO apparatus 1, the acidic liquid 6 containing nutrient components such as phosphoric acid, nitric acid, acetic acid and organic matter is concentrated. The slime mainly composed of microorganisms is generated in the vicinity of the RO membrane 2 to cause clogging, the membrane separation performance such as the blocking rate and the flux is lowered, and the differential pressure is increased. For this reason, the process moves to the cleaning process when the performance of the membrane is deteriorated, but the determination can be made by measuring the differential pressure and switching the process when the pressure becomes a predetermined value or more.

In the washing step, pure water is introduced into the washing liquid tank 7 from the line L10, an alkaline aqueous solution such as sodium hydroxide is supplied from the line L8, the mixture is stirred with the stirrer 9, the pH is measured with the pH meter 10, and the predetermined pH is obtained. Then, an aqueous enzyme solution is supplied from the line L9 and stirred with the stirrer 9 to prepare the cleaning liquid 8. At this time, if necessary, the cleaning liquid 8 can be heated to be adjusted to a temperature suitable for the enzyme reaction.
In the above embodiment, pure water is used for the adjustment of the cleaning liquid containing the enzyme agent. However, the present invention is not limited to this, and the liquid 6 to be treated may be used.

  Thereafter, the valves V1, V3, V4 are closed, the valves V2, V5, V6 are opened, and the cleaning liquid 8 is introduced from the line L7 into the concentrated liquid chamber 4 of the RO apparatus 1 by the pump P2, and is circulated from the line L6 to the RO membrane 2. And a part of the cleaning solution 8 is passed through the RO membrane 2. At the stage where the cleaning solution 8 is in uniform contact with the RO membrane 2 and the cleaning solution 8 is homogenized, the pump P2 is stopped to allow the enzyme reaction to proceed and decompose the slime, but if necessary, the pump P2 can be continuously or intermittently used. The cleaning liquid 8 can be circulated by driving. At this time, the permeate may be discharged out of the system or may be returned to the cleaning liquid tank 7. Further, when the cleaning liquid 8 is circulated, the valve V2 can be closed to prevent the cleaning liquid from permeating.

  After completion of the enzyme reaction, the cleaning liquid 8 is discharged or not discharged, and pure water is introduced from the line L10 into the cleaning liquid tank 7, supplied to the concentrated liquid chamber 4 from the line L7, and circulated from the line L6 to be washed with water. . Thereafter, an alkaline aqueous solution such as sodium hydroxide is introduced from the line L8 into the washing liquid tank 7, supplied to the concentrate chamber 4 from the line L7, circulated from the line L6, attached to the RO membrane 2, and remaining proteins, polysaccharides, Remove organic substances such as enzymes. Thereafter, the alkaline aqueous solution is discharged or not discharged, and pure water is introduced from the line L10 into the cleaning liquid tank 7, supplied to the concentrated liquid chamber 4 from the line L7, and circulated from the line L6 to be washed with water.

  Although the cleaning operation of the RO device 1 is completed as described above, the membrane separation performance of the RO membrane 2 is restored and the differential pressure is reduced. Therefore, the pump P2 is stopped, the valves V5 and V6 are closed, the valves V1 to V4 are opened, the pump P1 is driven, the liquid 6 to be treated is passed through the RO device 1, and the membrane separation process is resumed. Thus, the permeated water is recovered as pure water, and the phosphoric acid is concentrated and recovered. The above-described cleaning operation of the RO apparatus is performed periodically or at any time when the performance of the RO membrane is deteriorated.

  Examples of the present invention will be described below. In each example, “%” represents “% by weight” unless otherwise specified.

[Example 1, Comparative Example 1]: Petri dish observation;
Liquid crystal production wastewater containing phosphoric acid (phosphoric acid: 2000 mg / L, acetic acid: 100 mg / L, nitric acid: 100 mg / L, Al: 7 mg / L) Added. And 1 mL of the solution which melt | dissolved 50 g of filamentous fungus cell wall lytic enzyme Yatalase (the product made by Ozeki Co., Ltd., trademark, chitinase activity, chitobiase activity, glucanase activity) in 50 mL of pure water was added to the petri dish, and left still for 48 hours. (Example 1). Table 1 shows a comparison with that tested under the same conditions without addition of enzyme (Comparative Example 1). In Table 1, area% indicates a value where the initial value is 100%, and “clear” and “unclear” in the number of colonies mean the number of colonies whose colony boundaries are “clear” or “unclear”, respectively. As can be seen from Table 1, it was clearly observed that filamentous fungi were dissolved.

[Examples 2 to 6]:
The slime dissolution test similar to Example 1 was done using the commercially available enzyme agent. As for the enzyme agent used, Example 2 is chitinase (Akon CHL, manufactured by Toto Kasei Kogyo Co., Ltd., trademark), Example 3 is yeast cell wall lytic enzyme (YL-NL “Amano”, Amano Enzyme Co., Ltd.) Trademark), Example 4 is β-glucanase (Tunicase FN, trade name, manufactured by Daiwa Kasei Co., Ltd.), Example 5 is protease (Samoase PC10F, trade name, manufactured by Daiwa Kasei Co., Ltd.), and Example 6 is cellulase. (Cellulase A “Amano” 3, Amano Enzyme Co., Ltd., trademark). Use conditions and results are shown in Table 2. In Table 2, area% of all colonies indicates the value of area% of all colonies after 40 hours when the initial is 100%. From Table 2, even when other commercially available enzyme agents were used, the dissolution of filamentous fungi was observed, but chitinase showed the best solubility among them.

[Example 7, Comparative Example 2]: Test with RO membrane module;
Liquid crystal production wastewater containing phosphoric acid (RO phosphate 2000 mg / L, nitric acid 100 mg / L, nitric acid 100 mg / L, acetic acid 100 mg / l) in the RO device 1 of FIG. 1 loaded with a reverse osmosis membrane ES-20 (2-inch) module manufactured by Nitto Denko Corporation L, pH 2.1) was passed at an operating pressure of 1.6 MPa and a liquid flow rate of 300 L / h, and continuous operation was performed for 6 months. Six months later, the module differential pressure (inlet / outlet difference) was 0.07 MPa and the permeate flow rate was 30 L / hr. When the module was opened, the end face of the RO membrane module had a thickness of 0.5 to 2 mm slime was attached.

  After the module was immersed in a 0.1% sodium hydroxide solution for 2 days, flushing was performed at a flow rate of 100 L / h and an air flow rate of 3 L / min, but the module differential pressure remained at 0.07 MPa and did not change. (Comparative Example 2).

  Thereafter, a sodium hydroxide solution was added to 100 L of liquid crystal wastewater containing phosphoric acid to adjust the pH to 6.7, and 20 g of the enzyme Yatase was added to prepare an enzyme solution. This enzyme solution was circulated through the module without passing through the reverse osmosis membrane and allowed to stand for 48 hours. When the enzyme solution was discharged, pure water was supplied and washed, the module differential pressure decreased to 0.035 MPa, and the permeated water amount increased to 35 L / hr. Thereafter, a 0.1% sodium hydroxide solution was introduced, immersed for 12 hours, and pure water was further introduced and washed, whereby the amount of permeated water increased to 70 L / hr (Example 7).

[Example 8]: Test with RO membrane module;
The test was conducted in the same manner as in Example 7 except that the enzyme agent solution was passed through the reverse osmosis membrane module under conditions where the enzyme agent solution permeated at 35 L / hr. When the enzyme solution was discharged, pure water was supplied and washed, the module differential pressure decreased to 0.02 MPa.

  From the above results, in the method of membrane separation treatment of an acidic liquid to be treated with a reverse osmosis membrane, the reverse osmosis membrane of the reduced osmosis membrane was obtained by bringing the reverse osmosis membrane into contact with a cleaning solution containing an enzyme agent and washing it. It can be seen that slime is effectively removed, the differential pressure is reduced, and then the permeated water amount is further increased by washing with alkali. Here, since the differential pressure is reduced and the permeation flux is increased, it can be seen that the membrane separation performance is recovered. In addition, when the reverse osmosis membrane is brought into contact with the cleaning liquid containing the enzyme agent, it can be seen that the cleaning can be effectively performed by allowing a part of the cleaning liquid to pass through the reverse osmosis membrane.

  The present invention relates to a reverse osmosis membrane performance recovery method for membrane separation treatment of an acidic treatment liquid, and a membrane separation treatment method using a reverse performance reverse osmosis membrane, and in particular, reverse from an acidic treatment liquid containing phosphoric acid. The present invention can be used for a membrane separation treatment method suitable for a method of recovering phosphoric acid by an osmosis membrane and a method for recovering the performance of a reverse osmosis membrane.

It is a flowchart of the membrane separation processing apparatus using the reverse osmosis membrane apparatus in the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RO apparatus 2 RO membrane 3 Permeate chamber 4 Concentrate chamber 5 Processed liquid tank 6 Processed liquid 7 Cleaning liquid tank 8 Cleaning liquid 9 Stirrer 10 pH meter

Claims (6)

  A method for recovering the performance of a reverse osmosis membrane, characterized in that a reverse osmosis membrane having a reduced performance is brought into contact with a cleaning solution containing an enzyme agent in a method for membrane separation treatment of an acidic liquid to be treated with a reverse osmosis membrane.   2. The method according to claim 1, wherein the reverse osmosis membrane is washed by introducing an alkali when the reverse osmosis membrane is brought into contact with a cleaning solution containing an enzyme agent, or before or after that. In a method of performing membrane separation treatment with a reverse osmosis membrane on an acidic liquid to be treated,
At the time when the performance of the reverse osmosis membrane deteriorates, the treatment liquid is replaced with the cleaning liquid, or alkali is introduced without replacement, and after the cleaning agent containing the enzyme agent is brought into contact with the reverse osmosis membrane,
The reverse osmosis membrane is washed with an alkaline aqueous solution and pure water to restore performance.
A membrane separation treatment method comprising performing membrane separation treatment using a reverse osmosis membrane whose performance has been recovered.   4. The method according to claim 1, wherein when the reverse osmosis membrane is brought into contact with a cleaning liquid containing an enzyme agent, a part of the cleaning liquid is allowed to permeate through the reverse osmosis membrane.   5. The method according to claim 1, wherein the liquid to be treated is a waste liquid containing phosphoric acid.   6. The method according to any one of claims 1 to 5, wherein the enzyme agent contains an enzyme having a chitinolytic action.

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