Method for controlling membrane pollution of anaerobic membrane bioreactor by jointly adding biosurfactant and filler

Abstract

The invention discloses a method for controlling membrane pollution of an anaerobic membrane bioreactor (ANMBR) by jointly adding a biosurfactant and a filler, the ANMBR is used for treating municipal sewage, the biosurfactant and the filler are added into the ANMBR, and a membrane component and a mechanical stirring device are arranged. The membrane pollution control process is as follows: a biological surfactant with a certain concentration and a filler with a certain volume ratio are jointly added into the reactor. According to the invention, the biosurfactant is added into the AnMBR reactor to promote the dissolution of viscous substances and insoluble substances in a sludge mixed solution, and dissolved organic molecules are wrapped by micelles formed by the surfactant, so that the contact between organic pollutants and the membrane surface is reduced. Further, filler is added, so that the attachment of sludge flocs in the suspension and the adsorption of biosurfactant solubilizing substances are facilitated, the concentration of the sludge flocs, organic matters and other substances in the mixed solution is reduced, and finally, the membrane pollution of the AnMBR is effectively retarded on the premise of ensuring the remarkable operation efficiency of the reactor.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a method for controlling membrane pollution of an anaerobic membrane bioreactor by jointly adding a biological surfactant and a filler. Background Art

[0002] The anaerobic membrane bioreactor (AnMBR) is a new type of sewage treatment process that combines anaerobic biological treatment with membrane separation technology. It has the advantages of good treatment effect, less residual sludge, and production of biogas as a clean energy source. However, membrane fouling increases the operating cost of AnMBR, becoming a bottleneck problem that limits its widespread application.

[0003] At present, the membrane fouling of AnMBR is mainly controlled by modifying membrane materials, improving the characteristics of mixed liquor and changing the operating conditions of reactors. Among them, improving the characteristics of mixed liquor is one of the important means to alleviate membrane fouling. Most of the studies reduce the content of polysaccharides, proteins, humus and other substances in the mixed liquor by adding coagulants, flocculants, fillers, quorum sensing quenching enzymes and quorum sensing inhibitors to the reactor, thereby reducing membrane fouling.

[0004] In recent years, some studies have added surfactants to membrane bioreactors to affect the properties of the mixed solution through the solubilization, emulsification, reduction of surface tension, hydrophilicity / hydrophobicity and other characteristics of the surfactant, thereby slowing down membrane fouling. However, traditional synthetic surfactants have obvious toxicity to microorganisms, such as sodium dodecyl sulfate (SDS), Triton X-100 and tetradecyl trimethylammonium bromide, which may have adverse effects on sludge mixed solution. Biosurfactants have the advantages of being non-toxic, biodegradable, temperature-resistant, high-salt-resistant, adaptable to a wide pH range and environmentally friendly. Applying them to membrane bioreactors to control membrane fouling has become a research hotspot. At present, there are patent reports on the study of biosurfactants to control membrane fouling. For example, a method for preparing sophorolipids by fermentation and the application of sophorolipids in reverse osmosis membrane agents (CN114807271B) add sophorolipids to the influent, and the results show that sophorolipids have a significant blocking effect on organic matter (bovine serum albumin) and metal salts (containing calcium ions) in the influent during reverse osmosis membrane filtration. Through bridging, organic matter and metal salts are stabilized in water and not deposited on the reverse osmosis membrane, effectively blocking organic matter and metal salts from polluting the reverse osmosis membrane; the application of rhamnolipids as biological cleaning agents (CN102399644A) uses rhamnolipids as cleaning agents to clean the contaminated filter membrane. The former intercepts organic matter in simulated sewage, and the latter cleans the contaminated membrane. The environmental components faced by both in the process of using biosurfactants are relatively single and the conditions are relatively simple. The influence of biosurfactants on membrane pollution control in membrane biological reaction treatment systems with complex pollutants and microorganisms coexisting has not been investigated, and how biosurfactants intercept the contact between organic matter and membrane in solution has not been deeply investigated.

[0005] Zhang et al. (Separation and Purification Technology, 2023, 326, 124855) added rhamnolipid and magnetic powder to aerobic membrane bioreactors and found that rhamnolipid can reduce membrane fouling by reducing the viscosity of the mixed liquor. However, this study did not make full use of the changes in the characteristics of the sludge mixed liquor caused by the addition of biosurfactants to further combine other technologies to control membrane fouling, and the method of combining biosurfactants with fillers to control membrane fouling in anaerobic membrane bioreactors has not yet been reported. Summary of the invention

[0006] In view of the above technical problems existing in the prior art, the object of the present invention is to provide a method for controlling the membrane fouling of anaerobic membrane bioreactor by adding a biosurfactant and a filler in combination, aiming to further slow down the membrane fouling of AnMBR and promote the wide application of AnMBR municipal sewage treatment. The present invention controls the membrane fouling of AnMBR by adding a certain concentration of sophorolipids (SL) and a certain volume fraction of polyurethane sponge biofiller (PUS) to AnMBR. Sophorolipids are a class of non-ionic biosurfactants, and their solubilizing effect can promote the dissolution of viscous and insoluble substances in the sludge mixture. The solubilized organic molecules are wrapped by micelles formed by the surfactant, thereby reducing the contact between organic matter such as proteins and polysaccharides and the membrane surface. In addition, the addition of fillers is conducive to the attachment of sludge flocs in the sludge mixed liquor, and the polyurethane sponge filler contains carboxyl, hydroxyl, amine and other groups, which are also conducive to the adsorption of solubilized organic matter, ultimately reducing the concentration of suspended particles and organic matter in the mixed liquor and slowing down membrane fouling. The combined addition of the two can reduce the concentration of suspended particles and organic pollutants such as proteins and polysaccharides in the mixed liquor, thereby slowing down membrane fouling while ensuring the effluent quality and achieving stable operation of the AnMBR reactor.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for controlling membrane fouling of an anaerobic membrane bioreactor by combined addition of a biosurfactant and a filler, characterized in that: an anaerobic membrane bioreactor AnMBR is used to treat municipal sewage, a membrane module and a mechanical stirring device are arranged in the AnMBR, a water suspension of anaerobic sludge is contained in the AnMBR, the membrane module is suspended in the water suspension, a water outlet of the membrane module is connected to a water outlet pump through a pipeline, a pressure gauge is arranged on the pipeline between the water outlet of the membrane module and the water outlet pump, and a gas outlet of the AnMBR is connected to a gas collection bag;

[0009] When treating municipal sewage, the water suspension in the AnMBR is continuously stirred, and biosurfactants and fillers are added into the AnMBR. The combined action of biosurfactants and fillers reduces membrane fouling, and the methane gas generated during the sewage treatment process is collected.

[0010] Furthermore, the membrane assembly of the anaerobic membrane bioreactor has a pore size of 0.1±0.05 μm and is made of a submerged flat membrane made of polyvinylidene fluoride (PVDF), which is installed in the middle position of the anaerobic membrane bioreactor AnMBR.

[0011] Furthermore, AnMBR is operated in a continuous flow mode. When the transmembrane pressure difference TMP of the membrane assembly reaches a set value, the membrane assembly is disassembled for chemical cleaning, and then the cleaned membrane assembly is reinstalled to continue repeated operation.

[0012] Furthermore, when the transmembrane pressure difference TMP of the membrane assembly reaches 25 kPa, the membrane assembly is cleaned. The specific cleaning method is: soaking in a sodium hypochlorite solution with a mass fraction of 0.2-0.5% for at least 12 hours, then rinsing with clean water, and then continuing to use the membrane assembly.

[0013] Furthermore, the biosurfactant is a glycolipid biosurfactant sophorolipid, which has a higher interfacial potential and a stronger affinity for organic matter, an effective content of 50±5%, and a pH range of 6-7.

[0014] Furthermore, the filler is a polyurethane sponge biological filler. As an organic biological filler, polyurethane sponge filler (PUS) contains OH, NH, COOH and other groups, has strong hydrophilicity, large specific surface area, porosity of 95±3%, and density of 15±2kg / m 3 The polyurethane sponge biological filler is in the shape of a cube, and the diameter of the cube is 1-5 cm, preferably 2-3 cm.

[0015] Furthermore, the effective concentration of the biosurfactant sophorolipid added to the water suspension in the AnMBR is 20-100 mg / L, and the addition amount of the filler is 4-10% of the effective volume of the reactor. The addition amount of the filler 4-10% refers to the percentage of the total volume of the added filler to the volume of the water suspension in the AnMBR during the actual operation of the reactor AnMBR.

[0016] Furthermore, the fillers of the anaerobic membrane bioreactor are evenly arranged inside the reactor, and the stirring speed is controlled at 400-500 rpm.

[0017] Furthermore, AnMBR is operated by continuous membrane filtration, the membrane flux is set to 6-10LMH, the hydraulic retention time HRT of sewage in AnMBR is 24-48h, the average operating temperature is 25-28℃, and the sludge concentration is 6-8g / L.

[0018] Furthermore, the COD value of the municipal sewage is 400±20 mg / L, and the COD value of the treated clean water continuously discharged through the membrane module is 20±5 mg / L.

[0019] Compared with the prior art, the beneficial effects achieved by this application are:

[0020] (1) The present invention uses a biosurfactant, sophorolipid, to control membrane fouling, which has a solubilizing effect and promotes the dissolution of sticky and insoluble substances in the sludge mixture. The solubilized organic molecules are wrapped inside the micelles formed by the surfactant, thereby reducing the contact between organic matter such as proteins and polysaccharides and the membrane surface, thereby effectively slowing down membrane fouling.

[0021] (2) The addition of biosurfactants has no significant negative impact on microbial activity and can ensure stable effluent quality of AnMBR. In addition, the solubilization process of adding surfactants is conducive to promoting the anaerobic process, providing more substrates (such as soluble proteins and short-chain fatty acids) for methanogens, thereby increasing the production of anaerobic methanogens.

[0022] (3) The added polyurethane filler not only provides a carrier for biofilm formation and reduces the concentration of suspended solids in sludge, but also mainly uses the filler to adsorb the excessively high concentration of soluble organic matter generated by the solubilization process of adding sophora biosurfactant, especially the organic matter with a particle size distribution of 1-5μm that is closely related to membrane fouling. In addition, the surface of the polyurethane sponge filler contains carboxyl, hydroxyl, and amino groups. The addition of sophora biosurfactant can wrap the solubilized hydrophobic organic matter and form micelles with hydrophilic surface. The micelles can adhere to the filler surface by chemical bond connection, thereby further reducing the organic matter in the mixed liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the effect of different dosages of sophorolipids on membrane fouling in anaerobic membrane bioreactor;

[0024] Figure 2 This is the effect of combined addition of sophorolipids and fillers on membrane fouling in anaerobic membrane bioreactors;

[0025] Figure 3 a and Figure 3 b is the effect of combined addition of sophorolipids and fillers on the particle size fraction and concentration of organic matter (protein, polysaccharide) in the mixed liquor of anaerobic membrane bioreactor;

[0026] Figure 4 This is the effect of combined addition of sophorolipids and fillers on the COD removal rate of anaerobic membrane bioreactor;

[0027] Figure 5 This is a graph showing the effect of combined addition of microbial fermentation biosurfactant and filler on the methane gas production of anaerobic membrane bioreactor. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0029] In Example 1 of the present invention, the following operating conditions are adopted:

[0030] The influent is simulated municipal sewage, and the influent formula is: beef extract 28mg / L, C6H 12O6280 mg / L, peptone 82 mg / L, NH4Cl 153.6 mg / L, NaHCO3725 mg / L, KH2PO420 mg / L, the formula of trace elements is: FeSO4·7H2O2.5 mg / L, CaCl20.44 mg / L, MgCl2·6H2O 0.19 mg / L, Na2MoO4·2H2O 0.19 mg / L, CoCl2·6H2O0.13 mg / L, MnCl2·4H2O 0.06 mg / L, ZnCl20.06 mg / L, H3BO30.06 mg / L, CuSO40.06 mg / L, NiCl2·6H2O 0.04 mg / L, COD is maintained at about 400 mg / L.

[0031] The anaerobic membrane bioreactor uses a rectangular cavity with a bottom side length of 120mm×120mm, a height of 210mm, and a total volume of about 3000mL. The membrane assembly uses a flat membrane assembly, the membrane material is polyvinylidene fluoride, the membrane pore size is 0.1μm, and the effective filtration area is 98cm 2 The total volume of liquid and anaerobic sludge in the reactor was controlled to be about 2.5L, the sludge concentration was maintained at about 6g / L, the HRT of sewage in the reactor was 43h, the operating temperature was 25.0±3.7℃, the membrane flux was 6LMH, and the TMP changes were observed during the operation of the reactor.

[0032] In the embodiment of the present invention, the glycolipid biosurfactant Sophorolipid (Shandong Yousuo Chemical Technology Co., Ltd.) has an effective content of 50% and a pH range of 6-7. Sophorolipid is a microbial secondary metabolite produced by Candida with sugar and vegetable oil as carbon sources through a fermentation process under certain conditions. The concentration of Sophorolipid added during the experiment is its effective concentration. In the process of treating municipal sewage in the AnMBR of the present invention, Sophorolipid is directly poured into the reactor at one time according to the concentration required for the experiment at the initial stage of operation, and no addition is required to the influent.

[0033] The polyurethane sponge biofiller in the embodiment of the present invention is purchased from Henan Saiyue Environmental Protection Equipment Co., Ltd. and is made of polyurethane. The polyurethane sponge biofiller added in the experiment has a regular cubic structure and a size of 3×3×3cm. During the experiment, multiple 3×3×3cm cubic fillers were added according to the required amount of filler. The filler addition amount of 6% refers to the percentage of the total volume of the added filler to the volume of the water suspension in the AnMBR reactor during the actual operation of the AnMBR reactor.

[0034] Embodiment 1:

[0035] In this embodiment 1, an anaerobic membrane bioreactor is used to set multiple concentration gradients, select the most suitable amount of sophorolipid addition, and set five groups of "no sophorolipid addition", "sophorolipid addition concentration of 0.024 g / L", "sophorolipid addition concentration of 0.05 g / L", "sophorolipid addition concentration of 0.1 g / L", and "sophorolipid addition concentration of 0.2 g / L" to select the best sophorolipid addition concentration.

[0036] Reference Figure 1 It can be seen that when the addition concentration of low-concentration sophorolipids is 0.05g / L, the growth trend of TMP is the slowest, and the period to reach 25kPa is 7.5 days, which is 2.5 days longer than the blank group (period is 5 days). However, the addition of high concentrations (0.1g / L, 0.2g / L) aggravates membrane pollution, and its TMP growth rate is faster than that of the blank group TMP. This may be because the high concentration of surfactant dissolves excessive soluble microbial products, increases the concentration of organic pollutants such as proteins and polysaccharides in the sludge mixture, and causes more serious membrane pollution.

[0037] Therefore, the present invention provides a method for controlling membrane fouling of an anaerobic membrane bioreactor by jointly adding a biosurfactant and a filler, wherein the addition concentration of the biosurfactant is controlled to be 0.05 g / L.

[0038] Embodiment 2:

[0039] The anaerobic membrane bioreactor of this Example 2 is the same as that of Example 1, except that four conditions are set: "blank", "addition of 6% volume fraction of polyurethane sponge filler", "addition of 0.05 g / L sophorolipid", and "addition of 6% volume fraction of polyurethane sponge filler + addition of 0.05 g / L sophorolipid".

[0040] The membrane fouling of AnMBR under four conditions is summarized in Figure 2 middle. Figure 2 During the multiple cycles, when the TMP reaches 25kPa, the membrane assembly is removed and chemically flushed. The membrane assembly is soaked in a 0.3% sodium hypochlorite solution for 12 hours and then rinsed with clean water. The cleaned membrane assembly is used for the next cycle. Figure 2 It can be seen that the membrane fouling period when TMP reaches 25 kPa in the blank group AnMBR, AnMBR with polyurethane sponge filler added alone, AnMBR with sophorolipid added alone, and AnMBR with sophorolipid and polyurethane sponge filler added together are about 5d, 8d, 7d, and 10d, respectively. This shows that the addition of surfactants and fillers alone can effectively slow down membrane fouling, while the combined addition of surfactants and fillers has the best effect on membrane fouling control, and the membrane fouling period is twice as long as that of the blank group.

[0041] In the middle of the AnMBR operation process (TMP = 15kPa), 50mL of sludge mixed liquid was taken from the sampling port of the reactor and placed in a centrifuge at 2000rmp. After centrifugation for 5min, the mixed liquid was passed through filter membranes with different pore sizes (10, 5, 1, 0.45μm) in turn. The filtrates obtained by filtering with filter membranes with different pore sizes were tested for the concentrations of proteins and polysaccharides. The results are shown in Table 1. Figure 3 (b) According to Figure 3 (b) The percentage of protein content of different particle sizes in the sludge mixture to the total protein content was calculated, and the percentage of polysaccharide content of different particle sizes in the sludge mixture to the total polysaccharide content was calculated. The comparison results of the percentage of protein or polysaccharide content at different particle sizes were summarized in Figure 3 (a) From Figure 3 (b) As shown in the figure, in the experimental group where sophorolipids were added alone, the concentration of proteins and polysaccharides in the mixed solution increased due to the solubilization effect of sophorolipids, especially the particle size distribution of 1-5μm increased most significantly, which may be due to the solubilization of macromolecular organic matter into relatively small molecular organic matter of 1-5μm by biosurfactants. From the experimental group where sophorolipids and polyurethane sponge fillers were added together, it can be seen that the organic matter with a size of 1-5μm was significantly reduced compared with the group where sophorolipids were added alone, indicating that the addition of fillers is conducive to the adsorption of biosurfactant solubilization products. The combined addition of the two effectively controls the concentration of sludge particles and organic matter in the mixed solution, thereby achieving the purpose of slowing down membrane fouling.

[0042] The COD of AnMBR effluent under four conditions is as follows Figure 4 , Figure 4 The data of each bar graph in the figure are the effluent COD data measured on the third day of the reactor operation when TMP did not reach 25kPa in one operation cycle. The results show that the effluent COD of the blank AnMBR group is 17mg / L, the effluent COD of the single addition of polyurethane sponge filler is 18mg / L, the effluent COD of the single addition of sophorolipid is 22mg / L, and the effluent COD of the combined addition of polyurethane sponge filler and sophorolipid is 20mg / L. The COD removal rates of the four reactors are all above 90%. It shows that sophorolipid, polyurethane sponge filler and their combined addition have no significant effect on the COD removal of AnMBR.

[0043] The methane production of AnMBR under four conditions is as follows Figure 5 ,Under the four conditions, the AnMBR reactor recorded one operation cycle from the beginning to the end of the experiment, and the methane measurement data collected within one operation cycle. Figure 5The ordinate is the ratio of the total amount of methane gas in a cycle to the effluent COD removal rate, which represents the amount of methane that can be produced by microorganisms for every 1g of COD removed. The calculation process is: the total amount of gas in a cycle * the percentage of methane content / [(the influent COD concentration of the cycle - the effluent COD concentration) * the influent volume of the cycle]. The results show that the methane production of the single addition of polyurethane sponge filler, the single addition of sophorolipids, and the combined addition of polyurethane sponge fillers and sophorolipids is higher than that of the blank group, which increased by 1.6, 2.2 and 2.5 times, respectively. This may be because the filler can be beneficial to the enrichment of methanogenic bacteria, and the solubilization of sophorolipids is beneficial to the production of more substrates (soluble proteins and short-chain fatty acids) required by methanogenic bacteria.

[0044] Therefore, the method provided by the present invention for controlling membrane fouling of anaerobic membrane bioreactor by adding biosurfactant and filler in combination is expected to effectively alleviate membrane fouling and contribute to anaerobic methane production. The present invention adds biosurfactant and filler in combination in AnMBR, and promotes the dissolution of viscous and insoluble substances in the sludge mixture (mainly extracellular polymers present inside or on the surface of activated sludge flocs, proteins adhered to the surface of the filter membrane, etc.) through the biosurfactant sophorolipid, avoids the formation of the filter cake layer accelerated by the presence of these viscous and insoluble substances, and the solubilized organic molecules are wrapped by the micelles formed by the surfactant, thereby reducing the contact between organic matter such as protein and polysaccharide and the membrane surface. The added polyurethane sponge filler is conducive to the attachment of sludge flocs in the sludge mixed liquor and the adsorption of the solubilized organic matter, and finally reduces the concentration of suspended particles and organic matter in the mixed liquor, thereby slowing down membrane fouling under the condition of ensuring the effluent water quality, and realizing the stable operation of the AnMBR reactor.

[0045] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms described in the embodiments.

Claims

1. A method for controlling membrane fouling of an anaerobic membrane bioreactor by adding a biosurfactant and a filler, characterized in that: An anaerobic membrane bioreactor AnMBR is used to treat municipal sewage. A membrane module and a mechanical stirring device are arranged in the AnMBR. A water suspension of anaerobic sludge is contained in the AnMBR. The membrane module is suspended in the water suspension. The water outlet of the membrane module is connected to a water outlet pump through a pipeline. A pressure gauge is arranged on the pipeline between the water outlet of the membrane module and the water outlet pump. The gas outlet of the AnMBR is connected to a gas collection bag. When treating municipal sewage, the water suspension in the AnMBR is continuously stirred, and biosurfactants and fillers are added into the AnMBR. The combined action of biosurfactants and fillers reduces membrane fouling, and the methane gas generated during the sewage treatment process is collected.

2. The method for controlling membrane fouling of an anaerobic membrane bioreactor by combined addition of a biosurfactant and a filler as claimed in claim 1, characterized in that: AnMBR is a continuous flow operation mode. When the transmembrane pressure difference TMP of the membrane module reaches the set value, the membrane module is disassembled for chemical cleaning, and then the cleaned membrane module is reinstalled to continue repeated operation.

3. The method for controlling membrane fouling of an anaerobic membrane bioreactor by combined addition of a biosurfactant and a filler as claimed in claim 2, characterized in that: When the transmembrane pressure difference TMP of the membrane assembly reaches 25 kPa, the membrane assembly is chemically flushed by soaking it in a sodium hypochlorite solution with a mass fraction of 0.2-0.5% for at least 12 hours, and then rinsed with clean water before continuing to use the membrane assembly.

4. The method of controlling membrane fouling of an anaerobic membrane bioreactor by combined addition of a biosurfactant and a filler according to claim 1, characterized in that: The biosurfactant is a glycolipid biosurfactant, a sophorolipid, with an effective content of 50±5% and a pH range of 6-7.

5. The method for controlling membrane fouling of an anaerobic membrane bioreactor by combined addition of a biosurfactant and a filler according to claim 4, characterized in that: The effective concentration of the biosurfactant sophorolipid added to the water suspension in the AnMBR is 20-100 mg / L.

6. The method of controlling membrane fouling of an anaerobic membrane bioreactor by combined addition of a biosurfactant and a filler according to claim 1, characterized in that: The filler is a polyurethane sponge biological filler, which has strong hydrophilicity, large specific surface area, porosity of 95±3%, and density of 15±2 kg / m 3 The polyurethane sponge biological filler is in the shape of a cube, and the diameter of the cube is 1-5 cm, preferably 2-3 cm.

7. The method of controlling membrane fouling of an anaerobic membrane bioreactor by combined addition of a biosurfactant and a filler according to claim 6, characterized in that: The dosage of the filler is 4-10% of the effective volume of the reactor. The dosage of the filler 4-10% refers to the percentage of the total volume of the added filler to the volume of the water suspension in the AnMBR reactor during the actual operation of the AnMBR reactor.

8. The method of controlling membrane fouling of an anaerobic membrane bioreactor by combined addition of a biosurfactant and a filler according to claim 1, characterized in that: The membrane assembly of the anaerobic membrane bioreactor has a pore size of 0.1±0.05 μm and is made of PVDF submerged flat membrane, which is installed in the middle position of the anaerobic membrane bioreactor AnMBR.

9. The method of controlling membrane fouling of an anaerobic membrane bioreactor by combined addition of a biosurfactant and a filler according to claim 1, characterized in that: The fillers of the anaerobic membrane bioreactor are evenly arranged inside the reactor, and the stirring speed is controlled at 400-500 rmp; the anaerobic membrane bioreactor operates at a flux of 6-10 LMH and a sludge concentration of 6-8 g / L.

10. The method of controlling membrane fouling of an anaerobic membrane bioreactor by combined addition of a biosurfactant and a filler according to claim 1, characterized in that: The COD value of the municipal sewage is 400±20 mg / L, and the COD value of the treated clean water continuously discharged through the membrane module is 20±5 mg / L.

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