WO2012165748A1 - Method for washing a filtration membrane using a novel disinfectant - Google Patents

Abstract

Provided is a method for washing a filtration membrane using novel disinfectant applied to water treatment, and a method for controlling biofouling. The method for washing the filtration membrane includes a step of disinfecting raw water, inflow water, and a filtration membrane using a solution including isocyanurate to minimize damage of the membrane and maintain superior performance. Microorganisms which form a biofilm and cause biofouling may be inactivated to maintain a high salt removal rate and a stable amount of water penetration.

Description

Filtration membrane cleaning method using a new disinfectant

The present invention relates to a filtration membrane cleaning and bio fouling control method using a new disinfectant, and more particularly, to a filtration membrane cleaning method capable of minimizing membrane damage and reducing membrane performance change by using a new disinfectant.

Water treatment method using a filtration membrane is one of the widely used water treatment technology as the depletion and pollution of water resources intensify. It is widely used in water treatment, including desalination of seawater and brackish water, water purification, wastewater treatment, etc. because of its high stability and efficiency since energy efficiency and no additional chemicals are used. However, there is a problem that a fouling phenomenon occurs that contaminants adhere to the surface of the filtration membrane such as the osmosis membrane, thereby reducing performance. In order to solve this problem, the pretreatment process and clean-in-place (CIP) are important, which is a key factor in determining membrane performance and membrane lifetime.

Osmotic membrane is a membrane used to separate osmotic pressure, which is a membrane for separating a solution with a difference in concentration, after which a water of a low concentration solution moves through the membrane to a high concentration solution. The reverse osmosis phenomenon is to send water to a low concentration solution by applying an osmotic pressure or more to a high concentration solution, and the separator used at this time is a reverse osmosis membrane. Reverse osmosis membrane system is divided into water treatment, pretreatment, reverse osmosis membrane process, and post treatment.

The pretreatment process is an initial treatment of raw water before it is supplied to the reverse osmosis membrane. This process is performed to improve the quality of the raw water at the stage before the reverse osmosis membrane process. The chemical treatment and filter removes contaminants such as organic matter using chemicals and removes them through filters. Physical processing steps.

In reverse osmosis membrane processes, chlorine solutions are used as disinfectants to inactivate microorganisms, one of the major contaminants that degrade membranes and shorten their life during pretreatment and membrane cleaning steps. Chlorine solution, which is commonly used at this time, is made by diluting a liquid solution such as sodium hypochlorite, which decomposes hypochlorous acid in water.

Microorganisms are inactivated by chlorine, a strong oxidizing agent, where inactivation of microorganisms inhibits or kills the growth of microorganisms attached to the membrane or in water to eliminate the infectivity of microorganisms and inhibit the formation of biofilms. Chlorine disinfectants can reduce the contamination of membranes and contribute to maintaining performance and extending the lifespan by killing microorganisms by forming biofilms, reducing the permeation rate of membranes and shortening membrane lifespans and inhibiting their growth.

However, polyamide synthesized on the surface in order to increase the salt removal rate in the reverse osmosis membrane has a weak property to chlorine, which is easily damaged by chlorine treatment, resulting in deterioration of the membrane performance. For this reason, a large amount of reducing agent is added after the pretreatment process to remove residual chlorine present in the feed water of the membrane, thereby preventing damage to the membrane by chlorine. Reverse osmosis membranes are vulnerable to biofouling if microorganisms pass the pretreatment process in the absence of residual disinfectant. Therefore, short-term exposure to reverse osmosis membranes using alkali or complex salts other than chlorine reduces biofouling, but is not very effective.

Hypochlorous acid is a strong oxidant with economical disinfection and sterilization ability and is widely used in water treatment process for inactivation of contaminant microorganisms. Hypochlorous acid is a weak acid and exists as hypochlorous acid and hypochlorite ions depending on pH. Chlorine solutions containing hypochlorous acid are also used in various water treatment applications and in pretreatment of reverse osmosis membrane processes.

Although pretreatment using hypochlorous acid is excellent for inactivating microorganisms, the polyamide-based reverse osmosis membrane, which has been generalized, is damaged from hypochlorous acid and has a disadvantage of degrading the performance of the membrane. That is, the polyamide reverse osmosis membrane has a problem in that its structure is degraded by the chlorine component and thus its performance is lost, thereby shortening the life of the membrane. In addition, a large amount of reducing agent used after pretreatment to prevent oxidation of the membrane by the strong oxidizer hypochlorous acid may potentially promote biofouling because it can potentially become a nutrient of the microorganism.

In order to minimize the problems described above, it is necessary to develop a new membrane having excellent durability against chlorine, or to develop a new disinfectant which can be used in an existing membrane but prevents damage to the membrane.

It is an object of the present invention to provide a method for cleaning a membrane using a new disinfectant which can suppress biofouling while minimizing damage and degradation of the membrane by chlorine.

In order to achieve the above object, the filtration membrane cleaning method of the present invention comprises the step of disinfecting the filtration membrane with a solution containing isocyanuric acid.

In one embodiment, the filtration membrane may be at least one of reverse osmosis membrane, forward osmosis membrane, nanofiltration membrane, ultrafiltration membrane and microfiltration membrane.

In one embodiment, a polyamide reverse osmosis membrane is applied as the filtration membrane.

In one embodiment, the solution containing isocyanuric acid is obtained by dissolving an isocyanurate solid phase including powder and pellets in water.

In one embodiment, as the isocyanurate, at least one of sodium isocyanur dichloride, potassium isocyanur dichloride, sodium isocyanur trichloride, and potassium isocyanurate trichloride can be used.

In one embodiment, the filtration membrane is used in a water treatment process including desalination of seawater or brackish water, water purification, sewage treatment and wastewater treatment.

In one embodiment, the sterilizing of the filtration membrane is a method of injecting a solution containing isocyanuric acid during the pretreatment process, isocyanuric acid before or after the influent is supplied after the pretreatment process is performed. Method of injecting a solution containing, and immersing the filtration membrane in the solution containing the isocyanuric acid or circulating the solution is carried out in any one of the manner.

In one embodiment, after immersing the filtration membrane in a solution containing the isocyanuric acid or circulating the solution, the step of rinsing the filtration membrane with distilled water is further performed.

In one embodiment, before performing the disinfection step, a compaction step of supplying water for a predetermined time to stabilize the permeate amount is further performed.

In one embodiment, the pressure applied to the membrane in the compaction step is in the range of 200 to 800 psig.

In one embodiment, the microorganisms attached to the filtration membrane is inactivated through sterilizing the filtration membrane.

According to the washing method and the bio fouling control method according to an embodiment of the present invention configured as described above, despite the long-term exposure to the chlorine component, the salt removal rate is excellent and there is almost no change in the amount of permeate. In addition, the isocyanuric acid disinfectant according to the embodiment of the present invention is a component that is well dissolved in water, and does not need to use a separate organic solvent for its dissolution, and maintains an effective chlorine concentration that is relatively stable with respect to pH, temperature, and time. As a result, the membrane can be continuously disinfected and sterilized.

1 is a view schematically showing an example of a system for performing a water treatment process using a reverse osmosis membrane.

2 is a flowchart illustrating a reverse osmosis membrane cleaning method according to an embodiment of the present invention.

3 is a graph showing a change in the amount of permeated water according to the system operating time of the filtration membrane treated with sodium hypochlorite solution.

4 is a graph showing a change in the amount of permeated water according to the system operation time of the filtration membrane treated with sodium isocyanurium dichloride solution.

5 is a graph showing the change in the salt removal rate according to the system operation time of the filter membrane treated with sodium hypochlorite solution.

FIG. 6 is a graph showing the change in the salt removal rate according to the system operation time of the filtration membrane treated with sodium isocyanurium dichloride solution.

Hereinafter, a filtration membrane washing method using a new chlorine disinfectant according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described on the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, parts, or combinations thereof.

On the other hand, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

As a specific example, the present invention is to describe a method for cleaning and fouling the polyamide-based reverse osmosis membrane surface control. The filter membrane is used in different materials, in particular, the reverse osmosis membrane is a specific embodiment because the surface of the polyamide is vulnerable to chlorine components. After all, it means that the washing isocyanuric acid solution applicable to the reverse osmosis membrane can be easily applied to various other filtration membranes.

The washing method of the present invention is applicable almost without exception to all the filtration membranes used in the water treatment. For example, reverse osmosis membranes, forward osmosis membranes, nanofiltration membranes, ultrafiltration membranes, microfiltration membranes can be applied to all common filtration membranes that require disinfection and washing.

Compared with reverse osmosis membranes, other filtration membranes have a relatively slight degradation in performance or shortened lifespan due to chlorine components. to be. In addition, since isocyanurate has good solubility in water, it is well soluble in water without the use of a separate organic solvent and can be easily used in a filtration membrane cleaning process, which is one of water treatment technologies.

The water treatment method can be applied to almost all water treatment methods requiring filtration membranes such as desalination of seawater and brackish water, as well as water purification, sewage treatment, and wastewater treatment.

In the present invention, it is possible to reduce the damage of the filtration membrane by the chlorine solution used as a disinfectant in the washing process to inactivate the microorganism, one of the main causes of contamination to the filtration membrane and to control biofouling, and to decrease the membrane performance due to the filtration membrane damage. It is to use a solution containing isocyanuric acid component is a new chlorine disinfectant to minimize the.

In other words, microorganisms are inactivated, but the membrane is cleaned using isocyanuric acid, a new disinfectant that has minimal effect on the membrane. As the isocyanurate, all compounds which have high solubility in water and which can be dissolved in water to produce an isocyanuric acid component are applicable. Preferably, isocyanate dichloride solution and potassium isocyanur dichloride solution. Compounds, such as a solution, sodium isocyanur trichloride solution, and potassium isocyanur trichloride, can be used.

The washing of the filtration membrane using the isocyanuric acid component and the biofouling control can be performed in various ways. Filtration membrane disinfection includes various methods such as injecting a chlorine solution into the membrane system and dipping the membrane itself in the chlorine solution or circulating the solution.

Specifically, in the pretreatment process step, isocyanuric acid treatment may be performed instead of the conventional hypochlorous acid treatment. In this case, depending on the isocyanuric acid concentration, an appropriate amount of reducing agent may be used to remove the isocyanuric acid component after treatment, and a reducing agent may not be used to retain trace components. If the isocyanuric acid concentration is kept low, the traces of residual isocyanuric acid in the influent may continue to provide disinfecting effects rather than damaging the membrane, thus cleaning the membrane and controlling biofouling during influent treatment. You will get the effect.

Alternatively, the influent may be inactivated and the biofouling in the membrane may be controlled by injecting a low concentration of isocyanuric acid solution into the influent before or during the pretreatment of the influent. have. The biofouling of the membrane through this control has the advantage of slowing down the membrane fouling rate and increasing the cycle time of the cleaning process (CIP).

Alternatively, there is a method in which the purified water is stopped for a certain time and the membrane is immersed in a relatively high concentration of isocyanuric acid solution or the solution is circulated for disinfection. This method is applicable to the CIP process because it uses a relatively high concentration of the solution, shocking dosing in a short time (Shocking dosing) method has the advantage that can be disinfected with high satisfaction, but after the sterilization the step of further cleaning the membrane with distilled water The disadvantage is that after a normal operation of the system, a certain amount of production water, which can contain some cleaning solution, must be discarded.

For each application, it is desirable to maintain the concentration of isocyanuric acid in the solution in an appropriate range. To apply the first method, the concentration should be applied at the level necessary for pretreatment of raw water. The pretreatment process is an initial treatment of feed water, which includes chemical treatment of pollutants such as organic matter and physical treatment of removal through a filter. Therefore, the concentration of isocyanuric acid may vary according to various factors such as the degree of pollution of the raw water, the types of components included in the raw water, and the type of raw water. Preferably isocyanuric acid solution containing an effective chlorine concentration of about 50 mg / L or less is added. The isocyanuric acid component remaining in the influent after the chemical treatment is continuously passed through the filtration membrane, so the concentration should be lowered so that there is little irritation to the membrane. Therefore, if necessary, an appropriate amount of reducing agent is added to adjust the concentration of isocyanuric acid to a low level, and then to the filtration membrane system.

When disinfection and biofouling control are performed by injecting a low concentration of isocyanuric acid solution before or during the inflow of pretreated influent, a solution containing an effective chlorine concentration of about 20 mg / L or less is used. It is desirable to. In this case, the disinfecting solution must maintain a low chlorine concentration and can be injected discontinuously or continuously as necessary.

In the third method, the membrane is immersed in a solution containing isocyanuric acid or the solution is circulated. Thus, the highest concentration of isocyanuric acid solution is applied because the membrane is brought into contact with the disinfecting solution for a certain time. After disinfection of the membrane, it is possible to use high concentration solution because the membrane is thoroughly washed with clean water before the production water is redrawn. In this case, a solution containing an effective chlorine concentration of about 5000 mg / L or less can be used.

However, the classification of the concentration according to each washing method is for illustration only and is appropriately changed according to various factors such as the type of pollutant in the raw water, the degree of contamination, the type of raw water, whether the damage to the membrane, and whether the by-products are produced. Can be.

As described above, various methods can be applied to disinfect the membrane, and each has advantages and disadvantages. In consideration of the cleaning effect, a method of immersing the membrane in a solution or circulating the solution is most preferred.

Hereinafter, the filtration membrane washing method according to an embodiment of the present invention will be described in more detail with reference to the drawings.

1 is a diagram schematically showing a system for performing a water treatment process using a reverse osmosis membrane.

Referring to FIG. 1, the water treatment system schematically shows each component used to evaluate the performance of the membrane under pressure and temperature conditions for carrying out the reverse osmosis membrane process.

The system is largely divided into feed tank (1), temperature controller (2), high pressure pump (3), pressure regulator (4), cell (5), flow valve (6), permeation scale (7), computer (10), etc. It includes.

Each cell 5 is equipped with a reverse osmosis membrane in the form of a plate. The reverse osmosis membrane in the form of a plate can be used by cutting a spiral wound membrane into a flat membrane that can be attached to the cell 5. Influent can be supplied to the membrane in a lateral flow manner and pressure can be applied to an appropriate value. The pressure is adjustable for each cell 5 and the pressure regulated by the pressure regulator 4 is monitored via a connected computer 10. Different pressure values may be applied within the range of about 200 to 800 psig, depending on the use of the membrane, such as seawater and brackish water. For example, when using a membrane for water can be set to a constant pressure condition of about 225 psig.

2 is a flowchart illustrating a reverse osmosis membrane cleaning method according to an embodiment of the present invention. With reference to Figures 1 and 2 will be described the operation of the filtration system and the washing method of the reverse osmosis membrane.

In a specific and preferred embodiment, the microorganisms are washed with an isocyanuric acid, a new chlorine disinfectant that inactivates but has minimal effect on the membrane and measures the resulting change in membrane performance. In the present embodiment, the membrane was treated in such a way that a solution containing a high concentration of chlorine was made to immerse the filter membrane in order to show that the membrane performance was maintained well even under high chlorine conditions. In addition, the membrane was washed with sodium hypochlorite solution under the same conditions to evaluate the performance and compare the result data.

The reverse osmosis membrane mounted in each cell 5 in the form of a flat plate is compacted into tertiary distilled water as inflow water at a constant pressure, temperature, and lateral flow rate until the permeate amount of the membrane is stabilized (FIG. 2, step S10). The third distilled water generally refers to pure distilled water prepared by first distilling tap water, secondly distilling water using a filter, and thirdly distilling water using a semipermeable membrane. Recently, it is also manufactured using a filter, a semipermeable membrane and an ion exchange resin without first distillation.

The tertiary distilled water is supplied from the feed tank 1 and the temperature of the tertiary distilled water is kept constant by the temperature controller 2 connected to the tank. The temperature of the influent is 25 ?? It can be maintained at room temperature conditions. The tertiary distilled water of the feed tank 1 is delivered to each cell 5 by a high pressure pump 3 and used for the compaction of the membrane. The time at which the compaction is finished may vary depending on the type of membrane or the sample site of the membrane, and is the point at which it is determined that the permeate is stabilized. If the membrane has a certain amount of permeate, it can be determined that the compaction is completed. When the compaction is completed, treated water such as artificial seawater or brackish water having a salt concentration suitable for the treatment conditions of the membrane is supplied to evaluate the performance of the membrane. For example, when using a reverse osmosis membrane for brackish membrane performance evaluation can be performed with 2000 mg / L NaCl solution.

After compaction, the treated water, such as artificial seawater or brackish water, is used to determine the performance of the membrane by its influent treatment capability, which consists of measuring the permeate and salt removal rates. For example, 2000 mg / L NaCl solution used as influent is sent from feed tank 1 to each cell 5 by high pressure pump 3 and permeate the membrane under constant pressure by pressure regulator 4. The permeate 8 is collected by the automatic flowmeter and after collecting a certain amount, it returns to the feed tank 1 again. In addition, the permeate (8) passing through the membrane in the cell is an automatic flow meter, the concentrated water (9) that has not permeated and flows past the membrane to the feed tank (1) as it is.

One embodiment thus employs a circulating system in which permeate and concentrated water are returned to feed tank 1. Permeate volume and pressure in the system can be monitored in real time through the computer 10 connected to the system. After supplying the NaCl solution, the permeated water that passed through the membrane for a certain period of time was measured using a permeate water balance (7) to measure the concentration of the salt, from which the performance of the polyamide reverse osmosis membrane before chlorination was evaluated.

Membranes evaluated in accordance with the method described above are sterilized using sodium hypochlorite solution (Comparative Example 1) and sodium isocyanurium dichloride solution (Example 1) (FIG. 2, step S20). Preferably, the disinfection is performed by immersing the membrane in a chlorine solution such as sodium hypochlorite solution, sodium isocyanur dichloride solution, etc. at the same effective chlorine concentration for a predetermined time.

For performance evaluation of the degree of membrane damage, a solution of 5000 mg / L effective chlorine concentration can be used and the membrane can be exposed for 1 hour, 2 hours and 3 hours. After disinfection, the membrane is rinsed sufficiently with tertiary distilled water so as not to be affected by the residual chlorine (FIG. 2, step S30), and then mounted in the cell 5 of the system.

Thereafter, the performance evaluation of the disinfectant treated membrane is carried out in the same manner as before. Permeate volume and salt removal rate can be measured to compare membrane performance with the type of disinfectant and before disinfectant treatment.

Example 1

A spiral wound osmosis reverse osmosis membrane LFC1 (Hydranautics Co.) was dissected and cut into a flat membrane to fit the cell and mounted on the cell. All operations were set to 225 psig (or 15.5 bar) and 27 ± 2 ° C by a temperature controller and pressure regulator. The flow rate through all the cells was controlled to 50 ml / min by the flow valve. In order to find the equilibrium condition, feed 3rd distilled water (Millpore SAS, Mill-Q Direct8) to the feed tank for more than 20 hours, and monitor the permeate flow rate by automatic flow meter. The performance evaluation of the membrane was started.

A circulating system was used to provide about 6 L of NaCl solution to the feed tank and permeate and concentrated water back to the feed tank (see FIG. 1). In consideration of the time taken for the NaCl solution to pass through the membrane as permeate, the volume of permeate was measured after receiving the permeate for 1 hour. The salt concentration was measured using a conductivity meter (Horiba, DS-51, 9382-10D). After the initial membrane permeation rate and salt removal rate was confirmed, the membrane was removed from the cell, rinsed thoroughly with tertiary distilled water to remove the contaminants or salts, and the membrane was disinfected.

Disinfection of the membrane was carried out using a solution of sodium isocyanur dichloride, with an effective chlorine concentration of 5000 mg / L. The effective chlorine concentration was measured at a wavelength of 530 nm on a UV spectrometer using a DPD reagent (HACH ㄾ, DPD free chlorine reagent). Since the damage of the membrane was caused by the effective chlorine, the experiment was conducted based on the same effective chlorine, and the membrane was exposed to the solution for 1 hour, 2 hours, and 3 hours at a slightly higher concentration than in the actual process. One set of example experiments was conducted with one disinfection solution. The chlorinated membrane was then rinsed sufficiently with flowing tertiary distilled water so that residual chlorine did not remain on the surface and was then put back into the cell.

After each hour of disinfection, each membrane was put back in the cell and the system was run again. The performance of the treated membrane was evaluated in the same manner as above, considering the time until the supplied NaCl solution passed through the membrane. Membrane performance tests for about 120 hours were performed to measure the change in membrane performance over the operating hours of the system.

Comparative Example 1

In the same manner as described in Example 1, but disinfection of the membrane was carried out using sodium hypochlorite solution, the effective chlorine concentration of the solution was adjusted to 5000 mg / L.

Experiment result

3 and 4 and 5 and 6 show the results of evaluating the performance of the membrane after disinfection of the membrane using sodium hypochlorite solution and sodium isocyanurium dichloride solution. 3 is a graph showing the change of the permeate amount according to the system operation time of the membrane treated with sodium hypochlorite solution. 4 is a graph showing a change in the amount of permeated water according to the system operation time of the membrane treated with sodium isocyanurium dichloride solution.

5 is a graph showing the change in the salt removal rate with the system operating time of the membrane treated with sodium hypochlorite solution. 6 is a graph showing the change in the salt removal rate according to the system operation time of the membrane treated with sodium isocyanur dichloride solution.

In each figure, the graphs marked with 와 and solid line show the results for the case of using the reverse osmosis membrane without the disinfectant treatment. The graph marked with ■ shows the result when the membrane was treated with the disinfecting solution for 1 hour, and the graph marked with ▲ shows the result when the membrane was treated with the disinfecting solution for 2 hours, and the graph marked with ◆ shows the disinfection of the membrane for 3 hours. The result about the case with the solution is shown. Experiments were performed under the same conditions to compare and analyze the performance of membranes sterilized with both solutions.

In Figures 3 and 5, the graphs marked with ■ show the changing performance when the membrane treated with effective chlorine 5000 mg / L sodium hypochlorite solution for 1 hour was operated in the system as shown in Figure 1 for 120 hours. Represents an evaluation of the performance of the membrane treated for 2 and 3 hours, respectively. In the same manner, the graphs of FIGS. 4 and 6 show the results of performance evaluation of membranes treated with 5000 mg / L of sodium isocyanuric dichloride solution of effective chlorine. When the membrane treatment was carried out for a time. 2 shows the water permeation rate of the performance of the membrane.

In Figures 3 and 4, it can be said that the more the permeate amount under the condition that the salt removal rate is maintained, the better because there is a greater amount of water to be treated during the same time. 5 and 6 show the rate of salt removal in the performance of the membrane. Salt removal rate means the amount of salt contained in seawater or brackish water removed by the membrane. The higher the removal rate, the better the membrane. The performance is good when both the permeate quantity and the salt removal rate are high, but in the actual process, it is difficult to increase the salt removal rate when the permeate quantity is high and the permeate quantity is low when the salt removal rate is high. The system is operated under process conditions that meet performance.

3 and 4, the performance of the membrane treated with sodium isocyanuric dichloride solution (FIG. 4) shows that the change in the amount of permeate with time is smaller than the performance of the membrane treated with sodium hypochlorite solution (FIG. 3). Can be. In view of the change in performance of membranes treated with sodium hypochlorite solution, the permeate yield decreased sharply after disinfection of the membrane and then increased with increasing system operating time. In addition, the longer the disinfectant treatment time, the higher the rate of permeation increase, and in the case of the membrane treated for 3 hours, the amount increased by about 1.3 times beyond the initial permeate. On the other hand, the membrane performance treated with sodium isocyanate dichloride solution was significantly smaller than that treated with sodium hypochlorite solution compared to the untreated membrane, and the permeate amount was also not chlorine treated. It can be seen that the decrease is similar to the decrease in permeated water in fouling of the membrane by salt.

Even in the salt removal rates shown in FIGS. 5 and 6, the performance of membranes treated with sodium isocyanur dichloride solution was much higher. In FIG. 5, which shows the salt removal rate of the membrane treated with sodium hypochlorite solution, it was observed that the performance had already decreased immediately after the disinfection of the membrane. After that, the salt removal rate gradually decreased, and the membrane treated for 3 hours was 120 The run time of time resulted in a reduction in salt removal rate of about 20%. On the other hand, in the case of membranes treated with sodium isocyanuric dichloride solution, the salt removal rate of the membranes remained almost the same for a long system operation time as shown in FIG. 6.

Membrane treated with sodium hypochlorite solution shows low salt removal rate in spite of high permeated water, so it can be seen that the amount of water passing through the membrane is increased due to surface damage of the membrane by disinfectant, but not only water but also salt of influent.

From the results of the above performance evaluation, the filter membrane using sodium isocyanate dichloride solution as a disinfectant is superior to the performance maintaining the filter membrane treated with sodium hypochlorite solution, which is used. It can be seen that the effect on the film is small.

As described above, according to an embodiment of the present invention, a method of washing a membrane using an isocyanuric dichloride solution capable of maintaining stable concentrations of effective chlorine for a longer period of time with little damage to the membrane and allowing stable and continuous disinfection is provided. Is provided. In particular, the isocyanurate raw material is in a solid phase, which is convenient for preservation, high solubility in water, easy to use, and inexpensive, and therefore economical. In addition, since it maintains a relatively stable concentration of chlorine in water and room temperature, the disinfection and sterilization effect of microorganisms can be maintained for a long time. Above all, membranes cleaned using isocyanurate as a disinfectant have a high salt removal rate and a stable permeate rate even during long system operation.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (11)

1. A method of cleaning a filtration membrane comprising disinfecting the filtration membrane with a solution containing isocyanuric acid.
2. The method of claim 1, wherein the filtration membrane is at least one of a reverse osmosis membrane, an forward osmosis membrane, a nanofiltration membrane, an ultrafiltration membrane, and a microfiltration membrane.
3. The washing method according to claim 2, wherein the filtration membrane is a polyamide reverse osmosis membrane.
4. The method according to claim 1, wherein the solution comprising isocyanuric acid is obtained by dissolving an isocyanurate solid phase including powder and pellets in water.
5. The method of claim 4, wherein the isocyanurate is at least one selected from the group consisting of sodium isocyanur dichloride, potassium isocyanur dichloride, sodium isocyanur trichloride and potassium isocyanur trichloride. Characterized by a washing method.
6. The method of claim 1, wherein the filtration membrane is used in a water treatment process including desalination of seawater or brackish water, water purification, sewage treatment, and wastewater treatment.
7. The method of claim 1, wherein the sterilizing of the filtration membrane is performed by injecting a solution containing isocyanuric acid during the pretreatment process, before the influent water is supplied after the pretreatment process is performed or while the influent is supplied. Method of injecting a solution comprising a, and the method of immersing the filtration membrane in the solution containing the isocyanuric acid or circulating the solution, characterized in that carried out in any one of the manner.
8. The method of claim 7, wherein after performing the step of disinfecting the filtration membrane in a solution containing the isocyanuric acid or circulating the solution, the step of washing the filtration membrane with distilled water is further performed. Washing method.
9. The washing method according to claim 1, further comprising performing a compaction step of supplying water for a predetermined time to stabilize the permeate amount of the filtration membrane before performing the sterilizing step.
10. 10. The method of claim 9, wherein the pressure applied to the membrane in the compaction step is in the range of 200 to 800 psig.
11. The method of claim 1, wherein the microfiltration is inactivated and biofouling is controlled by disinfecting the filtration membrane.

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