Use of cationic hydrophobic polyacrylamide flocculants to mitigate membrane fouling

Abstract

The application discloses an application of a cationic hydrophobic polyacrylamide flocculant for slowing down membrane pollution, and a cationic hydrophobic polyacrylamide is synthesized through a copolymerization method. The cationic hydrophobic polyacrylamide flocculant is added into raw water in an ultrafiltration water purification process, after the polyacrylamide flocculant reaches the membrane surface, the hydrophobic association and the ultrafiltration membrane surface are combined, the hydrophilic end and the cationic group are unfolded outward, the membrane surface can be effectively hydrophilic modified, and the ultrafiltration membrane pollution and the removal of bacteria in the raw water are effectively slowed down.

Description

[0001] This invention relates to the field of membrane fouling control in ultrafiltration water purification processes, and specifically to an application of using cationic hydrophobic polyacrylamide flocculant to mitigate membrane fouling. Background Technology

[0002] With the increasing severity of global water scarcity and water pollution, advancements in water treatment technology have become particularly important. Ultrafiltration, as a highly efficient water treatment technology, is widely used due to its ability to effectively remove suspended solids, colloids, bacteria, and large organic molecules. However, membrane fouling is one of the major problems limiting the application of ultrafiltration technology, leading to decreased membrane flux, increased cleaning frequency and costs, and shortened membrane lifespan. To address this issue, various pretreatment technologies have been researched and applied, among which flocculation, as one pretreatment technology, mitigates membrane fouling by improving the quality of the influent.

[0003] Polyacrylamide is a widely used flocculant with good flocculation effects. However, ordinary polyacrylamide flocculants are not very effective in mitigating membrane fouling because ordinary polyacrylamide is difficult to interact with and modify the membrane surface, and it also lacks good bactericidal ability.

[0004] This patent aims to provide a method for mitigating membrane fouling during ultrafiltration using a cationic hydrophobic polyacrylamide flocculant. By optimizing the structure and properties of the flocculant, it binds to the membrane surface through hydrophobic association upon reaching the membrane, thereby modifying the membrane's hydrophilicity. Furthermore, the cationic groups of the flocculant can remove bacteria from the water, effectively mitigating membrane fouling. This method offers advantages such as simple operation, significant results, and low cost, providing strong technical support for the widespread application of ultrafiltration technology. Summary of the Invention

[0005] The technical problem that this invention aims to solve is how to mitigate ultrafiltration membrane fouling during the ultrafiltration water purification process.

[0006] This invention provides an application of using cationic hydrophobic polyacrylamide flocculant to mitigate membrane fouling, the preparation method and application comprising the following steps:

[0007] (1) By mass, mix 1100-1200 parts of pure water, 260-270 parts of acrylamide, 20-50 parts of cationic monomer, and 2-20 parts of hydrophobic monomer evenly and freeze to -2 °C. After passing nitrogen gas for 15 min, add 0.01-0.02 parts of complexing agent, 0.3-0.5 parts of initiator, and 0.01-0.05 parts of chain transfer agent in sequence. After passing nitrogen gas for 5 min, add 0.002-0.006 parts of oxidant. After 0.5 min, add 0.002-0.006 parts of reducing agent. Stop passing nitrogen gas at the beginning of the reaction. After the reaction is completed, keep warm for 2 h, take out the gel block, granulate, dry, and grind to make cationic hydrophobic polyacrylamide flocculant.

[0008] (2) Dissolve 10-20 parts by weight of kaolin, 5-10 parts by weight of humic acid, 5-10 parts by weight of bovine serum albumin, and 5-10 parts by weight of sodium alginate in 1000 parts by weight of pure water, and add Escherichia coli to the solution to a concentration of 10. 6 -10 7 CFU / L;

[0009] (3) First, prepare a 1-2 g / L solution of the cationic hydrophobic polyacrylamide from step (1), and maintain the flow rate of the wastewater from step (2) at 25 L / (m³) using a peristaltic pump. 2 •h), the flocculant flow rate is maintained at 2 L / (m 2 The hydraulic retention time in the ultrafiltration tank is 1 h, and the total surface area of ​​the fiber membrane in the ultrafiltration module is 300 cm². 2 Before use, soak the fiber membrane in pure water for 24 hours to clean it. After filtration every 30 minutes, apply a water flow of 30 L / (m³) for 0.5 minutes. 2 Backwashing was performed using a combination of air bubbling (150 L / h) and air bubbling (150 L / h). The fiber membrane was physically cleaned with a sponge at 12, 24 and 36 hours to remove the filter cake layer. Transmembrane pressure (TMP) was measured during 45-50 hours of fiber membrane operation.

[0010] The cationic monomer is allyltrimethylammonium chloride, the hydrophobic monomer is one of dodecyl dimethylallyl ammonium chloride, allyltributylphosphine chloride, or (3,3-dimethylallyl)triphenylphosphine bromide, the complexing agent is diethylenetriaminepentaacetic acid pentasodium, the initiator is azobisisobutyronitrile, the chain transfer agent is sodium hypophosphite, the oxidizing agent is tert-butyl hydroperoxide, and the reducing agent is sodium metabisulfite.

[0011] The membrane material is PVDF (polyvinylidene fluoride) or PES (polyether).

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] (1) By utilizing the hydrophobic effect of cationic hydrophobic polyacrylamide, after the flocculant reaches the membrane surface, it can bind to the membrane surface through hydrophobic association, thereby modifying the membrane surface to be hydrophilic and effectively blocking hydrophobic pollutants from reaching the membrane surface, thus mitigating membrane fouling.

[0014] (2) The bactericidal effect of the cationic group of the flocculant effectively removes bacteria in the raw water and slows down biofilm pollution. Attached Figure Description

[0015] Figure 1 This is the transmembrane pressure-time diagram for Example 1;

[0016] Figure 2 This is the transmembrane pressure-time diagram for Example 2;

[0017] Figure 3 This is the transmembrane pressure-time diagram for Example 3;

[0018] Figure 4 This is the transmembrane pressure-time diagram for Example 4;

[0019] Figure 5 This is the transmembrane pressure-time diagram for Example 5;

[0020] Figure 6 This is the transmembrane pressure-time diagram for Example 6;

[0021] Figure 7 This is the transmembrane pressure-time plot for Comparative Example 1;

[0022] Figure 8 This is the transmembrane pressure-time plot for Comparative Example 2;

[0023] Figure 9 The bacterial concentrations are those of Examples 1-6 and Comparative Examples 1-2. Detailed Implementation

[0024] The following are specific embodiments of the present invention, which further describe the operation scheme of the present invention. However, the present invention...

[0025] The scope of protection includes, but is not limited to, these embodiments. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. Example 1

[0026] (1) By mass, 1100 parts of pure water, 260 parts of acrylamide, 30 parts of allyltrimethylammonium chloride, and 5 parts of dodecyl dimethyl allyl ammonium chloride were mixed evenly and frozen to -2 °C. After purging with nitrogen for 15 min, 0.01 parts of diethylenetriaminepentaacetic acid pentasodium, 0.5 parts of azobisisobutyronitrile, and 0.02 parts of sodium hypophosphite were added sequentially. After purging with nitrogen for 5 min, 0.002 parts of tert-butyl hydroperoxide were added. After 0.5 min, 0.002 parts of sodium metabisulfite were added. Nitrogen purging was stopped at the beginning of the reaction. After the reaction was completed and kept at the temperature for 2 h, the gel block was removed, granulated, dried, and ground to prepare cationic hydrophobic polyacrylamide flocculant. The reaction formula is as follows: .

[0027] (2) By weight, dissolve 10 parts kaolin, 5 parts humic acid, 5 parts bovine serum albumin, and 5 parts sodium alginate in 1000 parts pure water, and add Escherichia coli to the solution until the concentration reaches 10. 6 CFU / L.

[0028] (3) Prepare a 1 g / L solution of the cationic hydrophobic polyacrylamide from step (1), and maintain the flow rate of the wastewater from step (2) at 25 L / (m³) using a peristaltic pump. 2 •h), the flocculant flow rate is maintained at 2 L / (m 2 The hydraulic retention time in the ultrafiltration tank is 1 h, and the total surface area of ​​the PVDF fiber membrane in the ultrafiltration module is 300 cm². 2 Before use, soak the PVDF fiber membrane in pure water for 24 hours to clean it. After filtration for 30 minutes, apply a water flow of 30 L / (m³) for 0.5 minutes. 2 Backwashing was performed using a combination of air bubbling (150 L / h) and air bubbling (150 L / h). The PVDF fiber membrane was physically cleaned with a sponge at 12, 24 and 36 hours to remove the filter cake layer. Transmembrane pressure (TMP) was measured during 48 hours of fiber membrane operation. Example 2

[0029] (1) By mass, 1130 parts of pure water, 263 parts of acrylamide, 33 parts of allyltrimethylammonium chloride, and 5.3 parts of dodecyl dimethyl allyl ammonium chloride were mixed evenly and then frozen to -2 °C. After purging with nitrogen for 15 min, 0.012 parts of diethylenetriaminepentaacetic acid pentasodium, 0.43 parts of azobisisobutyronitrile, and 0.022 parts of sodium hypophosphite were added sequentially. After purging with nitrogen for another 5 min, 0.0021 parts of tert-butyl hydroperoxide were added. After 0.5 min, 0.0022 parts of sodium metabisulfite were added. Nitrogen purging was stopped at the beginning of the reaction. After the reaction was completed and kept at the temperature for 2 h, the gel block was removed, granulated, dried, and ground to prepare a cationic hydrophobic polyacrylamide flocculant. The reaction formula is as follows: .

[0030] (2) By weight, dissolve 10.5 parts kaolin, 5.1 parts humic acid, 5.5 parts bovine serum albumin, and 5.3 parts sodium alginate in 1000 parts pure water, and add Escherichia coli to the solution until the concentration reaches 10. 6 CFU / L.

[0031] (3) Prepare a 1 g / L solution of the cationic hydrophobic polyacrylamide from step (1), and maintain the flow rate of the wastewater from step (2) at 25 L / (m³) using a peristaltic pump. 2 •h), the flocculant flow rate is maintained at 2 L / (m 2 The hydraulic retention time in the ultrafiltration tank is 1 h, and the total surface area of ​​the PES fiber membrane in the ultrafiltration module is 300 cm². 2 Before use, soak the PES fiber membrane in pure water for 24 hours to clean it. After filtration for 30 minutes, apply a water flow of 30 L / (m³) for 0.5 minutes. 2 Backwashing was performed using a combination of air bubbling (150 L / h) and air bubbling (150 L / h). The PES fiber membrane was physically cleaned with a sponge at 12, 24 and 36 hours to remove the filter cake layer. Transmembrane pressure (TMP) was measured during 48 hours of fiber membrane operation. Example 3

[0032] (1) By mass, 1140 parts of pure water, 265 parts of acrylamide, 23 parts of allyltrimethylammonium chloride, and 15 parts of allyltributylphosphine chloride were mixed evenly and then frozen to -2 °C. After purging with nitrogen for 15 min, 0.015 parts of diethylenetriaminepentaacetic acid pentasodium, 0.45 parts of azobisisobutyronitrile, and 0.025 parts of sodium hypophosphite were added sequentially. After purging with nitrogen for another 5 min, 0.0021 parts of tert-butyl hydroperoxide were added. After 0.5 min, 0.0023 parts of sodium metabisulfite were added. Nitrogen purging was stopped at the beginning of the reaction. After the reaction was completed and kept at the temperature for 2 h, the gel block was removed, granulated, dried, and ground to prepare a cationic hydrophobic polyacrylamide flocculant. The reaction formula is as follows: .

[0033] (2) By weight, dissolve 10.8 parts kaolin, 5.7 parts humic acid, 5.8 parts bovine serum albumin, and 5.9 parts sodium alginate in 1000 parts pure water, and add Escherichia coli to the solution until the concentration reaches 10. 6 CFU / L.

[0034] (3) Prepare a 1 g / L solution of the cationic hydrophobic polyacrylamide from step (1), and maintain the flow rate of the wastewater from step (2) at 25 L / (m³) using a peristaltic pump. 2•h), the flocculant flow rate is maintained at 2 L / (m 2 The hydraulic retention time in the ultrafiltration tank is 1 hour. The total surface area of ​​the PVDF fiber membrane in the ultrafiltration module is 300 cm². 2 Before use, soak the PVDF fiber membrane in pure water for 24 hours to clean it. After filtration for 30 minutes, apply a water flow of 30 L / (m³) for 0.5 minutes. 2 Backwashing was performed using a combination of air bubbling (150 L / h) and air bubbling (150 L / h). The PVDF fiber membrane was physically cleaned with a sponge at 12, 24 and 36 hours to remove the filter cake layer. Transmembrane pressure (TMP) was measured during 48 hours of fiber membrane operation. Example 4

[0035] (1) By mass, 1150 parts of pure water, 268 parts of acrylamide, 26 parts of allyltrimethylammonium chloride, and 17 parts of allyltributylphosphine chloride were mixed evenly and then frozen to -2 °C. After purging with nitrogen for 15 min, 0.014 parts of diethylenetriaminepentaacetic acid pentasodium, 0.46 parts of azobisisobutyronitrile, and 0.024 parts of sodium hypophosphite were added sequentially. After purging with nitrogen for another 5 min, 0.0022 parts of tert-butyl hydroperoxide were added. After 0.5 min, 0.0026 parts of sodium metabisulfite were added. Nitrogen purging was stopped at the beginning of the reaction. After the reaction was completed and kept at the temperature for 2 h, the gel block was removed, granulated, dried, and ground to prepare a cationic hydrophobic polyacrylamide flocculant. The reaction formula is as follows: .

[0036] (2) By weight, dissolve 10.9 parts kaolin, 5.5 parts humic acid, 5.1 parts bovine serum albumin, and 5.5 parts sodium alginate in 1000 parts pure water, and add Escherichia coli to the solution until the concentration reaches 10. 6 CFU / L.

[0037] (3) Prepare a 1 g / L solution of the cationic hydrophobic polyacrylamide from step (1), and maintain the flow rate of the wastewater from step (2) at 25 L / (m³) using a peristaltic pump. 2 •h), the flocculant flow rate is maintained at 2 L / (m 2 The hydraulic retention time in the ultrafiltration tank is 1 hour. The total surface area of ​​the PES fiber membrane in the ultrafiltration module is 300 cm². 2 Before use, soak the PES fiber membrane in pure water for 24 hours to clean it. After filtration for 30 minutes, apply a water flow of 30 L / (m³) for 0.5 minutes. 2Backwashing was performed using a combination of air bubbling (150 L / h) and air bubbling (150 L / h). The PES fiber membrane was physically cleaned with a sponge at 12, 24 and 36 hours to remove the filter cake layer. Transmembrane pressure (TMP) was measured during 48 hours of fiber membrane operation. Example 5

[0038] (1) By mass, 1120 parts of pure water, 264 parts of acrylamide, 20 parts of allyltrimethylammonium chloride, and 16 parts of (3,3-dimethylallyl)triphenylphosphine bromide were mixed evenly and frozen to -2 °C. After purging with nitrogen for 15 min, 0.015 parts of diethylenetriaminepentaacetic acid pentasodium, 0.5 parts of azobisisobutyronitrile, and 0.02 parts of sodium hypophosphite were added sequentially. After purging with nitrogen for 5 min, 0.002 parts of tert-butyl hydroperoxide were added. After 0.5 min, 0.002 parts of sodium metabisulfite were added. Nitrogen purging was stopped at the beginning of the reaction. After the reaction was completed and kept at the temperature for 2 h, the gel block was removed, granulated, dried, and ground to prepare a cationic hydrophobic polyacrylamide flocculant. The reaction formula is as follows: .

[0039] (2) By mass, dissolve 11 parts kaolin, 5.9 parts humic acid, 6 parts bovine serum albumin, and 5.8 parts sodium alginate in 1000 parts pure water, and add Escherichia coli to the solution until the concentration reaches 10. 6 CFU / L.

[0040] (3) Prepare a 1 g / L solution of the cationic hydrophobic polyacrylamide from step (1), and maintain the flow rate of the wastewater from step (2) at 25 L / (m³) using a peristaltic pump. 2 •h), the flocculant flow rate is maintained at 2 L / (m 2 The hydraulic retention time in the ultrafiltration tank is 1 h, and the total surface area of ​​the PVDF fiber membrane in the ultrafiltration module is 300 cm². 2 Before use, soak the PVDF fiber membrane in pure water for 24 hours to clean it. After filtration for 30 minutes, apply a water flow of 30 L / (m³) for 0.5 minutes. 2 Backwashing was performed using a combination of air bubbling (150 L / h) and air bubbling (150 L / h). The PVDF fiber membrane was physically cleaned with a sponge at 12, 24 and 36 hours to remove the filter cake layer. Transmembrane pressure (TMP) was measured during 48 hours of fiber membrane operation. Example 6

[0041] (1) By mass, 1170 parts of pure water, 267 parts of acrylamide, 24 parts of allyltrimethylammonium chloride, and 19 parts of (3,3-dimethylallyl)triphenylphosphine bromide were mixed evenly and frozen to -2 °C. After purging with nitrogen for 15 min, 0.01 parts of diethylenetriaminepentaacetic acid pentasodium, 0.5 parts of azobisisobutyronitrile, and 0.02 parts of sodium hypophosphite were added sequentially. After purging with nitrogen for 5 min, 0.002 parts of tert-butyl hydroperoxide were added. After 0.5 min, 0.002 parts of sodium metabisulfite were added. Nitrogen purging was stopped at the beginning of the reaction. After the reaction was completed and kept at the temperature for 2 h, the gel block was removed, granulated, dried, and ground to prepare a cationic hydrophobic polyacrylamide flocculant. The reaction formula is as follows: .

[0042] (2) By weight, dissolve 11.3 parts kaolin, 5.5 parts humic acid, 5.8 parts bovine serum albumin, and 5.7 parts sodium alginate in 1000 parts pure water, and add Escherichia coli to the solution until the concentration reaches 10. 6 CFU / L.

[0043] (3) Prepare a 1 g / L solution of the cationic hydrophobic polyacrylamide from step (1), and maintain the flow rate of the wastewater from step (2) at 25 L / (m³) using a peristaltic pump. 2 •h), the flocculant flow rate is maintained at 2 L / (m 2 The hydraulic retention time in the ultrafiltration tank is 1 h, and the total surface area of ​​the PES fiber membrane in the ultrafiltration module is 300 cm². 2 Before use, soak the PES fiber membrane in pure water for 24 hours to clean it. After filtration for 30 minutes, apply a water flow of 30 L / (m³) for 0.5 minutes. 2 Backwashing was performed using a combination of air bubbling (150 L / h) and air bubbling (150 L / h). The PES fiber membrane was physically cleaned with a sponge at 12, 24 and 36 hours to remove the filter cake layer. Transmembrane pressure (TMP) was measured during 48 hours of fiber membrane operation.

[0044] Comparative Example 1:

[0045] (1) By mass, 1150 parts of pure water, 269 parts of acrylamide, and 5 parts of dodecyl dimethyl allyl ammonium chloride were mixed evenly and frozen to -2 °C. After passing nitrogen gas for 15 min, 0.015 parts of diethylenetriaminepentaacetic acid pentasodium, 0.44 parts of azobisisobutyronitrile, and 0.025 parts of sodium hypophosphite were added in sequence. After passing nitrogen gas for 5 min, 0.0025 parts of tert-butyl hydroperoxide were added. After 0.5 min, 0.0021 parts of sodium metabisulfite were added. Nitrogen gas was stopped at the beginning of the reaction. After the reaction was completed and kept warm for 2 h, the gel block was taken out, granulated, dried, and ground to prepare polyacrylamide flocculant.

[0046] (2) By weight, dissolve 12 parts kaolin, 5.8 parts humic acid, 5.3 parts bovine serum albumin, and 5.7 parts sodium alginate in 1000 parts pure water, and add Escherichia coli to the solution until the concentration reaches 10. 6 CFU / L.

[0047] (3) Prepare a 1 g / L solution of polyacrylamide from step (1), and maintain the flow rate of the wastewater from step (2) at 25 L / (m³) using a peristaltic pump. 2 •h), the flocculant flow rate is maintained at 2 L / (m 2 The hydraulic retention time in the ultrafiltration tank is 1 hour, and the total surface area of ​​the PVDF fiber membrane in the ultrafiltration module is 300 cm². 2 Before use, soak the PVDF fiber membrane in pure water for 24 hours to clean it. After filtration for 30 minutes, apply a water flow of 30 L / (m³) for 0.5 minutes. 2 Backwashing was performed using a combination of air bubbling (150 L / h) and air bubbling (150 L / h). The PVDF fiber membrane was physically cleaned with a sponge at 12, 24 and 36 hours to remove the filter cake layer. Transmembrane pressure (TMP) was measured during 48 hours of fiber membrane operation.

[0048] Comparative Example 2:

[0049] (1) By mass, 1170 parts of pure water, 265 parts of acrylamide, and 30 parts of allyltrimethylammonium chloride were mixed evenly and frozen to -2 °C. After passing nitrogen gas for 15 min, 0.012 parts of diethylenetriaminepentaacetic acid pentasodium, 0.47 parts of azobisisobutyronitrile, and 0.025 parts of sodium hypophosphite were added in sequence. After passing nitrogen gas for 5 min, 0.0022 parts of tert-butyl hydroperoxide were added. After 0.5 min, 0.0023 parts of sodium metabisulfite were added. Nitrogen gas was stopped at the beginning of the reaction. After the reaction was completed and kept warm for 2 h, the gel block was taken out, granulated, dried, and ground to prepare polyacrylamide flocculant.

[0050] (2) By weight, dissolve 11.8 parts kaolin, 5.8 parts humic acid, 6.2 parts bovine serum albumin, and 6.1 parts sodium alginate in 1000 parts pure water, and add Escherichia coli to the solution until the concentration reaches 10. 6 CFU / L.

[0051] (3) Prepare a 1 g / L solution of polyacrylamide from step (1), and maintain the flow rate of the wastewater from step (2) at 25 L / (m³) using a peristaltic pump. 2 •h), the flocculant flow rate is maintained at 2 L / (m 2The hydraulic retention time in the ultrafiltration tank is 1 hour. The total surface area of ​​the PVDF fiber membrane in the ultrafiltration module is 300 cm². 2 Before use, soak the PVDF fiber membrane in pure water for 24 hours to clean it. After filtration for 30 minutes, apply a water flow of 30 L / (m³) for 0.5 minutes. 2 Backwashing was performed using a combination of air bubbling (150 L / h) and air bubbling (150 L / h). The PVDF fiber membrane was physically cleaned with a sponge at 12, 24 and 36 hours to remove the filter cake layer. Transmembrane pressure (TMP) was measured during 48 hours of fiber membrane operation.

[0052] The transmembrane pressure-time results for the above embodiments and comparative examples are attached. Figure 1-8 As shown, Examples 1-6 used cationic hydrophobic polyacrylamide to mitigate membrane fouling during ultrafiltration. The results showed that the transmembrane pressure increased slowly in the four stages of 0-12 h, 12-24 h, 24-26 h, and 36-48 h. After backwashing and physical cleaning, the transmembrane pressure quickly reached a very low level, indicating that most of the membrane fouling was reversible and easily removed by physical cleaning. This is because the cationic hydrophobic polyacrylamide, upon reaching the membrane surface, binds to the membrane surface through hydrophobic association, hydrophilically modifying the membrane surface and effectively blocking hydrophobic contaminants from reaching it. The polyacrylamide flocculant in Comparative Example 1 could bind to the membrane surface but lacked good bactericidal ability, leading to increased transmembrane pressure due to biofilm fouling. The flocculant in Comparative Example 2, lacking hydrophobic monomers, had difficulty binding effectively to the membrane surface and could not hydrophilically modify it, thus resulting in significant membrane fouling.

[0053] Appendix Figure 9 The bacterial concentrations in the supernatant of the ultrafiltration membrane tanks in Examples 1-6 and Comparative Examples 1-2 after stable operation are shown. The results indicate that the flocculants in Examples 1-6 and Comparative Example 2 contain a large number of cationic groups, which is beneficial for the removal of bacteria in the water. However, the polyacrylamide flocculant in Comparative Example 1 contains very few cationic groups, resulting in a greater number of residual bacteria in the water.

Claims

1. An application of using cationic hydrophobic polyacrylamide flocculant to mitigate membrane fouling, characterized in that: Includes the following steps: (1) By mass, mix 1100-1200 parts of pure water, 260-270 parts of acrylamide, 20-50 parts of cationic monomer, and 2-20 parts of hydrophobic monomer evenly and freeze to -2 °C. After passing nitrogen gas for 15 min, add 0.01-0.02 parts of complexing agent, 0.3-0.5 parts of initiator, and 0.01-0.05 parts of chain transfer agent in sequence. After passing nitrogen gas for 5 min, add 0.002-0.006 parts of oxidant. After 0.5 min, add 0.002-0.006 parts of reducing agent. Stop passing nitrogen gas at the beginning of the reaction. After the reaction is completed, keep warm for 2 h, take out the gel block, granulate, dry, and grind to make cationic hydrophobic polyacrylamide flocculant. (2) Dissolve 10-20 parts of kaolin, 5-10 parts of humic acid, 5-10 parts of bovine serum albumin and 5-10 parts of sodium alginate in 1000 parts of pure water by mass, and add Escherichia coli to the solution until the concentration reaches 106-107 CFU / L. (3) First, prepare a 1-2 g / L solution of the cationic hydrophobic polyacrylamide flocculant from step (1), and maintain the flow rate of the wastewater from step (2) at 25 L / (m³) using a peristaltic pump. 2 •h), the flocculant flow rate is maintained at 2 L / (m 2 The hydraulic retention time in the ultrafiltration tank is 1 h, and the total surface area of ​​the fiber membrane in the ultrafiltration module is 300 cm². 2 Before use, soak the fiber membrane in pure water for 24 hours to clean it. After filtration every 30 minutes, use a water flow of 30 L / (m³) for 0.5 minutes. 2 Backwashing was performed using a combination of air bubbling (150 L / h) and air bubbling (150 L / h). The fiber membrane was physically cleaned with a sponge at 12, 24 and 36 hours to remove the filter cake layer. The transmembrane pressure (TMP) was measured during 45-50 hours of fiber membrane operation. The cationic monomer is allyltrimethylammonium chloride, the hydrophobic monomer is one of dodecyl dimethyl allylammonium chloride, allyl tributylphosphine chloride, or (3,3-dimethylallyl)triphenylphosphine bromide, the complexing agent is diethylenetriaminepentaacetic acid pentasodium, the initiator is azobisisobutyronitrile, the chain transfer agent is sodium hypophosphite, the oxidant is tert-butyl hydroperoxide, and the reducing agent is sodium metabisulfite.

2. The application of cationic hydrophobic polyacrylamide flocculant to mitigate membrane fouling according to claim 1, characterized in that: The fiber membrane material is PVDF (polyvinylidene fluoride) or PES (polyethersulfone).

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