Method for cleaning and regenerating MBR (Membrane Bioreactor) invalid membrane module

Abstract

The invention discloses a cleaning and regenerating method for an MBR (Membrane Bioreactor) failure membrane module. In a conventional physical and chemical cleaning method, enzyme cleaning is added, and the cleaning sequence is that physical cleaning is carried out firstly, enzyme cleaning is carried out secondly, and chemical cleaning is completed finally. The method can gradually, reasonably and deeply remove various pollutants remaining on the surface of the failed membrane module and in membrane holes, further improves the cleaning efficiency, and better recovers and maintains the membrane flux. The cleaning liquid used in the invention can also effectively improve the cleaning effect of the failed membrane module, further recovers the membrane flux, is simple and convenient to operate, does not generate secondary pollution, and greatly reduces the cleaning cost. The method disclosed by the invention is simple and convenient to operate, and has a wide application prospect in the aspect of relieving serious pollution of the membrane module in the MBR operation process.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method for cleaning and regenerating a failed MBR membrane component. Background Art

[0002] Membrane bioreactor (MBR) is a sewage treatment process that combines membrane separation technology with traditional activated sludge method. It has the characteristics of good effluent quality, strong resistance to water quality shock load, small footprint and low sludge production. In recent years, it has been widely used in sewage treatment fields such as urban sewage and industrial wastewater. However, the inevitable membrane pollution problem has restricted the development of MBR. With the continuous operation of MBR, sludge, colloidal particles and soluble macromolecular organic matter in the reactor will be retained by the membrane components. They are adsorbed and deposited on the membrane surface or in the membrane pores, causing the membrane pore size to become smaller or blocked, resulting in a decrease in membrane flux (J) and an increase in transmembrane pressure difference (TMP), affecting the stable operation of MBR.

[0003] The causes of membrane component contamination can be divided into concentration polarization, membrane pore blockage and membrane surface adsorption and deposition. Concentration polarization is the process in which the mixed liquid flows to the membrane surface, and macromolecular substances and solid particles are constantly adsorbed and deposited on the membrane surface, causing the solute concentration near the membrane surface to be higher than the concentration of the mixed liquid, and forming a stable concentration decreasing zone at a certain thickness on the membrane surface. Pollutants are adsorbed and deposited outside and inside the membrane pore channel, causing different degrees of membrane pore blockage. At the same time, various pollutants are adsorbed and deposited on the membrane surface to form filter cake layers, including mud cake layers, gel layers and inorganic pollution layers.

[0004] In addition to the measures to control membrane fouling used in MBR operation, membrane cleaning technology is a common means to alleviate membrane fouling problems and maintain good performance of membrane components. From the perspective of cleaning operations, membrane cleaning can be divided into online maintenance cleaning and offline recovery cleaning. Among them, online maintenance cleaning is simple to operate and can improve the use status of membrane components in a short time, but it is difficult to remove deep pollutants, and the surface of the membrane components is prone to fouling again. Offline recovery cleaning usually uses high-concentration cleaning agents, which has a good membrane flux recovery effect and can maintain good performance of membrane components for a long time. On the other hand, from the perspective of cleaning methods, membrane cleaning is mainly divided into physical cleaning and chemical cleaning. Physical cleaning is a method that uses fluid dynamics to make pollutants leave the membrane material. It usually includes hydraulic cleaning, air aeration cleaning, ultrasonic cleaning, etc., which is simple to operate and will not cause secondary pollution. The loose mud cake layer can be removed by physical cleaning and is generally considered to be reversible dirt; if the mud cake layer is compacted and becomes dense, physical cleaning cannot remove it, it is considered to be irreversible dirt and needs to be further removed by chemical cleaning. Chemical cleaning is the use of chemical reagents to increase the electrostatic repulsion between pollutants and membrane materials, or chemical reagents react with membrane pollutants, so that pollutants leave the membrane material and precipitate with the solution, thereby restoring membrane flux and effectively alleviating membrane pollution. Common reagents include acids, alkalis, oxidants, surfactants, and metal chelators. Chemical cleaning can remove irreversible dirt such as dense mud cake layers, gel layers, and inorganic pollution layers.

[0005] Enzyme preparations have the characteristics of high specificity, selectivity, biodegradability and environmental friendliness. They perform well in the biocatalytic conversion of various water-soluble compounds and can destroy the fouling layer on the membrane surface under mild reaction conditions. Commonly used enzymes include proteases, amylases, lipases and cellulases. Enzyme cleaning can effectively remove stubborn dirt such as proteins and polysaccharides. Studies have shown that when using too much concentration of enzyme cleaning solution or non-optimal cleaning time, the enzyme will be deposited on the membrane surface, resulting in reduced cleaning efficiency and the possibility of re-contamination of the membrane. Therefore, it is very important to control the enzyme cleaning conditions and the cleaning order.

[0006] The types of MBR membrane components mainly include hollow fiber membranes, flat membranes, tubular membranes and ceramic membranes. Among them, hollow fiber membranes have the advantages of high flux, high retention rate, wear resistance, corrosion resistance, etc., but they are easy to be blocked and broken, and have a relatively short service life. After the hollow fiber membrane is polluted, the membrane filaments are easily entangled to form mud, resulting in a sharp drop in membrane flux and relatively difficult cleaning. Flat membranes have better anti-pollution performance, strong mechanical stability, and are easy to clean and maintain. After being polluted, the flat membrane can be cleaned by online cleaning or by removing and flushing a single membrane sheet, and the cleaning difficulty is relatively low.

[0007] Existing conventional cleaning methods can partially restore the flux of failed membrane components. However, in most cases, conventional methods have limited cleaning capabilities for failed membrane components. In order to obtain better cleaning effects, a cleaning and regeneration method for failed MBR membrane components is sought to gradually and reasonably remove pollutants and further improve cleaning efficiency, which has positive significance for extending the service life of membrane components and reducing the operation and maintenance costs of MBR. Summary of the invention

[0008] In order to overcome the above defects and shortcomings in the prior art, the present invention provides a method for cleaning and regenerating a failed MBR membrane assembly.

[0009] The first object of the present invention is to provide a method for cleaning a failed MBR membrane assembly.

[0010] The present invention claims the following:

[0011] A method for cleaning an MBR failed membrane assembly comprises the following steps:

[0012] S1. Use clean water to physically clean the failed membrane assembly;

[0013] S2. Use enzyme cleaning solution, alkaline cleaning solution, acid cleaning solution and surfactant cleaning solution to clean the failed membrane assembly in sequence, and discharge the cleaning solution after each cleaning.

[0014] Preferably, in step S1, the physical cleaning includes flushing the surface of the failed membrane assembly, backwashing, aeration flushing and ultrasonic cleaning.

[0015] More preferably, the time for flushing the surface of the failed membrane assembly is 10 to 20 minutes, the time for backwashing is 20 to 30 minutes, the time for aeration flushing is 10 to 20 minutes, and the time for ultrasonic cleaning is 10 to 20 minutes.

[0016] Most preferably, the time for flushing the surface of the failed membrane assembly is 15 minutes, the time for backwashing is 25 minutes, the time for aeration flushing is 10 minutes, and the time for ultrasonic cleaning is 15 minutes.

[0017] Preferably, in step S2, the enzyme cleaning solution is a protease solution or an amylase solution.

[0018] More preferably, the protease solution is an alkaline protease solution, and the amylase solution is an alkaline amylase solution.

[0019] More preferably, the volume fraction of the alkaline protease solution is 0.15% to 0.3%, and the volume fraction of the alkaline amylase solution is 0.4% to 0.6%.

[0020] Most preferably, the volume fraction of the alkaline protease solution is 0.3%, and the volume fraction of the alkaline amylase solution is 0.5%.

[0021] More preferably, the pH of the alkaline protease solution is 10, and the pH of the alkaline amylase solution is 9.

[0022] More preferably, the temperature of the alkaline protease solution is 50-60°C, and the temperature of the alkaline amylase solution is 60-80°C.

[0023] Preferably, in step S2, the alkaline cleaning solution is a sodium hypochlorite solution or a sodium percarbonate solution.

[0024] More preferably, the mass fraction of the sodium hypochlorite solution is 1% to 2%, and the mass fraction of the sodium percarbonate solution is 1% to 2%.

[0025] Most preferably, the mass fraction of the sodium hypochlorite solution is 1.5%, and the mass fraction of the sodium percarbonate solution is 1.5%.

[0026] More preferably, the pH of the sodium hypochlorite solution is 11, and the pH of the sodium percarbonate solution is 10.

[0027] Preferably, in step S2, the acidic cleaning solution is a citric acid solution or a nitric acid solution.

[0028] More preferably, the mass fraction of the citric acid solution is 1% to 2%, and the mass fraction of the nitric acid solution is 1% to 2%.

[0029] Most preferably, the mass fraction of the citric acid solution is 1.5%, and the mass fraction of the nitric acid solution is 1.5%.

[0030] More preferably, the pH of the citric acid solution is 2, and the pH of the nitric acid solution is 1.

[0031] Preferably, in step S2, the surfactant cleaning solution is a sodium dodecyl sulfate solution or a sodium dodecylbenzene sulfonate solution.

[0032] More preferably, the mass fraction of the sodium dodecyl sulfate solution is 0.4% to 0.6%, and the mass fraction of the sodium dodecylbenzene sulfonate solution is 0.4% to 0.6%.

[0033] Most preferably, the mass fraction of the sodium dodecyl sulfate solution is 0.5%, and the mass fraction of the sodium dodecylbenzene sulfonate solution is 0.5%.

[0034] More preferably, the pH of the sodium dodecyl sulfate solution is 7, and the pH of the sodium dodecylbenzene sulfonate solution is 10.

[0035] Preferably, in step S2, the cleaning method is one or more of immersion, backwashing and water circulation.

[0036] More preferably, the flow rate of the water inlet pump during the soaking is 400-800 mL / min, the flow rate of the water inlet pump during the backwashing is 800-1200 mL / min, and the flow rate of the water outlet pump during the water outlet circulation is 100-140 mL / min.

[0037] Most preferably, the flow rate of the water inlet pump during the soaking is 600 mL / min, the flow rate of the water inlet pump during the backwashing is 1000 mL / min, and the flow rate of the water outlet pump during the water outlet circulation is 120 mL / min.

[0038] Preferably, in step S2, the cleaning time of the enzyme cleaning solution, the alkaline cleaning solution, the acid cleaning solution and the surfactant cleaning solution is 2 to 4 hours.

[0039] More preferably, the cleaning time of the enzyme cleaning solution is 4 hours, the cleaning time of the alkaline cleaning solution is 2 hours, the cleaning time of the acidic cleaning solution is 2 hours, and the cleaning time of the surfactant cleaning solution is 3 hours.

[0040] Preferably, the failed membrane assembly is a failed hollow fiber membrane assembly.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention discloses a cleaning and regeneration method for MBR failed membrane components. The present invention adds enzyme cleaning to conventional physical and chemical cleaning methods, and the cleaning sequence is first physical cleaning, then enzyme cleaning, and finally chemical cleaning. The method can gradually and reasonably remove various pollutants remaining on the surface of the failed membrane component and in the membrane pores, further improve the cleaning efficiency, and the membrane flux is also better restored and maintained.

[0043] The cleaning liquid used in the present invention can effectively improve the cleaning effect of the failed membrane component, further restore the membrane flux, is simple and convenient to operate, does not generate secondary pollution, and greatly reduces the cleaning cost.

[0044] The cleaning method of the present invention includes soaking, backwashing and effluent circulation. According to different conditions of membrane component failure caused by membrane pollution, a suitable cleaning method for the failed membrane component can be well found, and various pollutants remaining on the surface and membrane pores of the failed membrane component can be efficiently removed. The operation is simple and convenient, and it has a wide application prospect in alleviating the serious pollution of the membrane component during the operation of MBR. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1This is a graph showing changes in TMP and J during the cleaning process of Example 1.

[0046] Figure 2 This is a graph showing changes in TMP and J during the cleaning process of Example 2.

[0047] Figure 3 This is a graph showing changes in TMP and J during the cleaning process of Example 3.

[0048] Figure 4 This is a graph showing changes in TMP and J during the cleaning process of Comparative Example 1.

[0049] Figure 5 This is a graph showing the changes in TMP and J during the cleaning process of Comparative Example 2.

[0050] Figure 6 This is a graph showing changes in TMP and J during the cleaning process of Comparative Example 3.

[0051] Figure 7 This is a graph showing changes in TMP and J during the cleaning process of Comparative Example 4. DETAILED DESCRIPTION

[0052] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0053] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0054] In the embodiments of the present invention, the type of failed membrane assembly used is specifically a hollow fiber membrane. This choice is based on its practicality and availability in specific application scenarios, rather than a strict limitation on the scope of application of the present invention. The key to the present invention lies in its innovative methods and treatment means, which are universal and can be widely applied to various types of failed membrane assemblies, including but not limited to flat membranes, tubular membranes, ceramic membranes and other forms of membrane assemblies. The application of hollow fiber membranes is only an example of an embodiment of the present invention, and is intended to demonstrate the effectiveness and practicality of the present invention in treating specific types of failed membrane assemblies.

[0055] Cleaning efficiency = ((membrane resistance before cleaning - membrane resistance after cleaning) ÷ membrane resistance before cleaning) × 100%.

[0056] Example 1 A method for cleaning and regenerating a failed membrane assembly of a membrane bioreactor

[0057] 1. Experimental Methods

[0058] S1. Use clean water to rinse the surface of the failed membrane assembly for 10 minutes, then backwash it for 25 minutes, then aerate it for 20 minutes, and then perform ultrasonic cleaning for 20 minutes;

[0059] S2. The failed membrane module is cleaned with the prepared enzyme cleaning solution, which is composed of alkaline protease, with a concentration of 0.15% (v / v), a pH value of 10, a temperature of 50-60°C, and a backwashing and soaking method. The cleaning time is 3h. The flow rate of the water inlet pump during backwashing is 1000mL / min. The enzyme cleaning solution is discharged after the cleaning is completed;

[0060] S3. The failed membrane module is cleaned with a prepared alkaline cleaning solution, which is composed of sodium hypochlorite with a concentration of 1% (w / v) and a pH value of 11. The cleaning method is backwashing and soaking. The cleaning time is 4 hours. The flow rate of the water inlet pump during backwashing is 1000 mL / min. The alkaline cleaning solution is discharged after the cleaning is completed.

[0061] S4. The failed membrane module is cleaned with the prepared acidic cleaning solution, which is composed of citric acid with a concentration of 1.5% (w / v) and a pH value of 2. The cleaning method is backwashing and soaking. The cleaning time is 4 hours. The flow rate of the water inlet pump during backwashing is 1000 mL / min. The acidic cleaning solution is discharged after the cleaning is completed.

[0062] S5. The failed membrane components are cleaned with the prepared surfactant cleaning solution, which is composed of sodium dodecyl sulfate with a concentration of 0.5% (w / v) and a pH value of 7. The cleaning method is backwashing and soaking. The cleaning time is 3 hours. The flow rate of the water inlet pump during backwashing is 1000 mL / min. The surfactant cleaning solution is discharged after the cleaning is completed.

[0063] 2. Experimental Results

[0064] The changes of TMP and J during the cleaning process are as follows Figure 1 As shown, the cleaning efficiency is 95.8%.

[0065] Example 2 A method for cleaning and regenerating a failed membrane component of a membrane bioreactor

[0066] 1. Experimental Methods

[0067] S1. Use clean water to rinse the surface of the failed membrane assembly for 15 minutes, then backwash it for 25 minutes, then aerate it for 10 minutes, and then perform ultrasonic cleaning for 15 minutes;

[0068] S2. The failed membrane module is cleaned with the prepared enzyme cleaning solution, which is composed of alkaline protease, with a concentration of 0.3% (v / v), a pH value of 10, a temperature of 50-60°C, and a cleaning method of soaking and water circulation. The cleaning time is 4 hours in total. The flow rate of the water inlet pump during soaking is 600 mL / min, and the flow rate of the water outlet pump during water circulation is 120 mL / min. The enzyme cleaning solution is discharged after the cleaning is completed;

[0069] S3. The failed membrane module is cleaned with the prepared alkaline cleaning solution, which is composed of sodium hypochlorite with a concentration of 1.5% (w / v) and a pH value of 11. The cleaning method is soaking and water circulation. The cleaning time is 2 hours. The flow rate of the water inlet pump during soaking is 600 mL / min, and the flow rate of the water outlet pump during water circulation is 120 mL / min. The alkaline cleaning solution is discharged after the cleaning is completed;

[0070] S4. The failed membrane module is cleaned with the prepared acidic cleaning solution, which is composed of citric acid with a concentration of 1.5% (w / v) and a pH value of 2. The cleaning method is soaking and water circulation. The cleaning time is 2 hours. The flow rate of the water inlet pump during soaking is 600 mL / min, and the flow rate of the water outlet pump during water circulation is 120 mL / min. The acidic cleaning solution is discharged after the cleaning is completed.

[0071] S5. The failed membrane components are cleaned with a prepared surfactant cleaning solution, which is composed of sodium dodecylbenzene sulfonate with a concentration of 0.5% (w / v) and a pH value of 10. The cleaning method is soaking for 3 hours. The flow rate of the water inlet pump during soaking is 600 mL / min. The surfactant cleaning solution is discharged after the cleaning is completed.

[0072] 2. Experimental Results

[0073] The changes of TMP and J during the cleaning process are as follows Figure 2 As shown, the cleaning efficiency is 96.5%.

[0074] Example 3 A method for cleaning and regenerating a failed membrane assembly of a membrane bioreactor

[0075] 1. Experimental Methods

[0076] S1. Use clean water to rinse the surface of the failed membrane assembly for 20 minutes, then backwash it for 25 minutes, then aerate it for 10 minutes, and then perform ultrasonic cleaning for 10 minutes;

[0077] S2. The failed membrane module is cleaned with the prepared enzyme cleaning solution, which is composed of alkaline amylase, with a concentration of 0.5% (v / v), a pH value of 9, a temperature of 60-80°C, and a cleaning method of soaking and water circulation. The cleaning time is 2h. The flow rate of the water inlet pump during soaking is 600mL / min, and the flow rate of the water outlet pump during water circulation is 120mL / min. The enzyme cleaning solution is discharged after the cleaning is completed;

[0078] S3. The failed membrane module is cleaned with the prepared alkaline cleaning solution, which is composed of sodium percarbonate, with a concentration of 1.5% (w / v) and a pH value of 10. The cleaning method is soaking and water circulation. The cleaning time is 3 hours. The flow rate of the water inlet pump during soaking is 600 mL / min, and the flow rate of the water outlet pump during water circulation is 120 mL / min. The alkaline cleaning solution is discharged after the cleaning is completed;

[0079] S4. The failed membrane module is cleaned with the prepared acidic cleaning solution, which is composed of nitric acid with a concentration of 1.5% (w / v) and a pH value of 1. The cleaning method is soaking and water circulation. The cleaning time is 3 hours. The flow rate of the water inlet pump during soaking is 600 mL / min, and the flow rate of the water outlet pump during water circulation is 120 mL / min. The acidic cleaning solution is discharged after the cleaning is completed;

[0080] S5. The failed membrane components are cleaned with the prepared surfactant cleaning solution, which is composed of sodium dodecylbenzene sulfonate with a concentration of 0.5% (w / v) and a pH value of 10. The cleaning method is soaking and water circulation. The cleaning time is 3 hours. The flow rate of the water inlet pump during soaking is 600 mL / min, and the flow rate of the water outlet pump during water circulation is 120 mL / min. The surfactant cleaning solution is discharged after cleaning is completed.

[0081] 2. Experimental Results

[0082] The changes of TMP and J during the cleaning process are as follows Figure 3 As shown, the cleaning efficiency is 82.2%.

[0083] Comparative Example 1

[0084] 1. Experimental Methods

[0085] S1. Use clean water to rinse the surface of the failed membrane assembly for 5 minutes, then backwash it for 20 minutes, and then aerate it for 10 minutes;

[0086] S2. The failed membrane module is cleaned with a prepared alkaline cleaning solution, wherein the alkaline cleaning solution is composed of sodium hypochlorite with a concentration of 0.5% (w / v) and a pH value of 10. The cleaning method is soaking for 3 hours. The flow rate of the water inlet pump during soaking is 600 mL / min. After the cleaning is completed, the alkaline cleaning solution is discharged;

[0087] S3. The failed membrane assembly is cleaned with the prepared acidic cleaning solution, which is composed of citric acid with a concentration of 1.5% (w / v) and a pH value of 3. The cleaning method is soaking for 3 hours. The flow rate of the water inlet pump during soaking is 600 mL / min. The acidic cleaning solution is discharged after the cleaning is completed.

[0088] 2. Experimental Results

[0089] The changes of TMP and J during the cleaning process are as follows Figure 4 As shown, the cleaning efficiency is 42.5%.

[0090] Comparative Example 2

[0091] 1. Experimental Methods

[0092] S1. Use clean water to rinse the surface of the failed membrane assembly for 10 minutes, then backwash it for 15 minutes, and then aerate it for 10 minutes;

[0093] S2. The failed membrane module is cleaned with a prepared alkaline cleaning solution, wherein the alkaline cleaning solution is composed of sodium hypochlorite with a concentration of 1.5% (w / v) and a pH value of 11. The cleaning method is soaking for 3 hours. The flow rate of the water inlet pump during soaking is 600 mL / min. After the cleaning is completed, the alkaline cleaning solution is discharged;

[0094] S3. The failed membrane module is cleaned with a prepared acidic cleaning solution, wherein the acidic cleaning solution is composed of citric acid, the concentration is 2% (w / v), the pH value is 2, the cleaning method is soaking, the cleaning time is 3h, the flow rate of the water inlet pump during soaking is 600mL / min, and the acidic cleaning solution is discharged after the cleaning is completed;

[0095] S4. The failed membrane components are cleaned with the prepared enzyme cleaning solution, which is composed of alkaline protease with a concentration of 0.3% (v / v), a pH value of 10, and a temperature of 50-60°C. The cleaning method is backwashing and soaking. The cleaning time is 3 hours. The flow rate of the water inlet pump during backwashing is 1000 mL / min. The enzyme cleaning solution is discharged after cleaning is completed.

[0096] 2. Experimental Results

[0097] The changes of TMP and J during the cleaning process are as follows Figure 5 As shown, the cleaning efficiency is 66.4%.

[0098] Comparative Example 3

[0099] 1. Experimental Methods

[0100] S1. Use clean water to rinse the surface of the failed membrane assembly for 10 minutes, then backwash it for 20 minutes, and then aerate it for 10 minutes;

[0101] S2. The failed membrane module is cleaned with the prepared enzyme cleaning solution, which is composed of alkaline protease, with a concentration of 0.3% (v / v), a pH value of 10, a temperature of 50-60°C, and a backwashing and soaking method. The cleaning time is 3h. The flow rate of the water inlet pump during backwashing is 1000mL / min. The enzyme cleaning solution is discharged after the cleaning is completed;

[0102] S3. The failed membrane module is cleaned with a prepared alkaline cleaning solution, wherein the alkaline cleaning solution is composed of sodium hypochlorite with a concentration of 1.5% (w / v) and a pH value of 11. The cleaning method is soaking for 3 hours. The flow rate of the water inlet pump during soaking is 600 mL / min. After the cleaning is completed, the alkaline cleaning solution is discharged;

[0103] S4. The failed membrane assembly is cleaned with the prepared acidic cleaning solution, which is composed of citric acid with a concentration of 2% (w / v) and a pH value of 2. The cleaning method is soaking for 3 hours. The flow rate of the water inlet pump during soaking is 600 mL / min. The acidic cleaning solution is discharged after the cleaning is completed.

[0104] 2. Experimental Results

[0105] The changes of TMP and J during the cleaning process are as follows Figure 6 As shown, the cleaning efficiency is 76.2%.

[0106] Comparative Example 4

[0107] 1. Experimental Methods

[0108] The failed membrane assembly was cleaned according to the cleaning method in Example 3 of Chinese invention patent CN 115715933A, as follows:

[0109] S1. Use clean water to flush the failed membrane assembly;

[0110] S2. The failed membrane module is cleaned with a prepared alkaline cleaning solution, which is composed of sodium hypochlorite, sodium lauryl sulfate and sodium dodecylbenzene sulfonate in a mass ratio of 1:1, and sodium hydroxide. The concentration of sodium hypochlorite is 800 mg / L, the concentration of sodium lauryl sulfate and sodium dodecylbenzene sulfonate is 100 mg / L, the pH value is 12, and the immersion is 10 minutes. After the immersion is completed, the alkaline cleaning solution is discharged;

[0111] S3. The failed membrane module is cleaned with a prepared complex enzyme preparation cleaning solution, which is composed of a protease, an esterase, an oxidoreductase and a peroxidase in a mass ratio of 1:1:1:1, and a concentration of 20 mg / L. The mixture is soaked for 5 minutes, and the complex enzyme preparation cleaning solution is discharged after the soaking is completed;

[0112] S4. The failed membrane components are cleaned with a prepared acid cleaning solution, which is composed of citric acid, sodium tripolyphosphate and disodium ethylenediaminetetraacetate. The concentration of sodium tripolyphosphate is 100 mg / L, the concentration of the metal chelating agent is 100 mg / L, the pH value is 3, and the soaking is for 10 minutes. After the soaking is completed, the acid cleaning solution is discharged.

[0113] 2. Experimental Results

[0114] The changes of TMP and J during the cleaning process are as follows Figure 7 As shown, the cleaning efficiency is 2.8%.

[0115] It can be seen that the cleaning solution used in the embodiment of the present invention greatly improves the cleaning effect of the failed membrane assembly compared with the traditional cleaning solution used in the comparative example, and further restores the membrane flux. The present invention adds enzyme cleaning to the conventional physical and chemical cleaning methods, and the cleaning sequence is to first physically clean the failed membrane assembly, then perform enzyme cleaning, and finally complete chemical cleaning. At the same time, the present invention provides different cleaning methods, including soaking, backwashing and effluent circulation, which are suitable for cleaning failed membrane assemblies with different degrees of contamination, and can gradually and reasonably remove various pollutants remaining on the surface of the failed membrane assembly and in the membrane pores, thereby improving the cleaning efficiency, and the membrane flux is also better restored and maintained, and the operation is simple and convenient.

[0116] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for cleaning an MBR failed membrane assembly, characterized in that: The following steps are involved: S1. Use clean water to physically clean the failed membrane assembly; S2. Use enzyme cleaning solution, alkaline cleaning solution, acid cleaning solution and surfactant cleaning solution to clean the failed membrane assembly in sequence, and discharge the cleaning solution after each cleaning.

2. The cleaning method according to claim 1, characterized in that: In step S1, the physical cleaning includes flushing the surface of the failed membrane assembly, backwashing, aeration flushing and ultrasonic cleaning.

3. The cleaning method according to claim 2, characterized in that: The time for flushing the surface of the failed membrane assembly is 10 to 20 minutes, the time for backwashing is 20 to 30 minutes, the time for aeration flushing is 10 to 20 minutes, and the time for ultrasonic cleaning is 10 to 20 minutes.

4. The cleaning method according to claim 1, characterized in that: In step S2, the enzyme cleaning solution is a protease solution or an amylase solution.

5. The cleaning method according to claim 1, characterized in that: In step S2, the alkaline cleaning solution is a sodium hypochlorite solution or a sodium percarbonate solution.

6. The cleaning method according to claim 1, characterized in that: In step S2, the acidic cleaning solution is a citric acid solution or a nitric acid solution.

7. The cleaning method according to claim 1, characterized in that: In step S2, the surfactant cleaning solution is a sodium dodecyl sulfate solution or a sodium dodecylbenzene sulfonate solution.

8. The cleaning method according to claim 1, characterized in that: In step S2, the cleaning method is one or more of immersion, backwashing and water circulation.

9. The cleaning method according to claim 1, characterized in that: In step S2, the cleaning time of the enzyme cleaning solution, the alkaline cleaning solution, the acid cleaning solution and the surfactant cleaning solution is 2 to 4 hours.

10. The cleaning method according to claim 1, characterized in that: The failed membrane component is a failed hollow fiber membrane component.

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