Method for treating low-carbon-source sewage by MBCR process and application

Abstract

The application provides a method for treating low-carbon-source sewage by using an MBCR process and application, and the method comprises the following steps: building an integrated MBR reactor, feeding low-carbon-source sewage into the membrane bioreactor, and performing filtration treatment through a membrane assembly, wherein the membrane assembly is a modified PVDF piezoelectric beta crystal hollow fiber ultrafiltration membrane, and the sludge improver comprises chitosan or sodium alginate. The method can improve the removal efficiency of low-carbon-source sewage, improve the membrane separation efficiency and stability, reduce energy consumption and operation and maintenance cost, and brings important social, economic and environmental benefits to the field of low-carbon-source freshwater aquaculture sewage treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and relates to an MBCR (MBR-activated carbon-activated sludge) process and application thereof, in particular to a method for treating low-carbon-source sewage by using the high-efficiency, stable and energy-saving MBCR process and application thereof. BACKGROUND

[0002] With the acceleration of global urbanization and the increase of population, the aquaculture industry has developed rapidly. In particular, in rural and remote areas, aquaculture has become an important economic source. However, due to the lack of proper sewage treatment facilities in these areas, a large amount of low-carbon-source aquaculture sewage is directly discharged, causing serious pollution to the environment. The COD concentration of aquaculture sewage is often lower than 200 mg / L. Previous studies have shown that under low-carbon-source conditions, the mass ratio of C / N and C / P is low, especially the low concentration of COD at the initial stage of operation, which brings great trouble to sewage treatment plants. In general, the organic matter is lacking in low-C / N sewage, and the microorganisms in the activated sludge compete for resources with each other, which leads to the balance between nitrification and denitrification being broken, and the biological denitrification process being inhibited, resulting in poor removal effect of total nitrogen pollutants and relatively poor effluent quality. Cr Cr The traditional aquaculture sewage treatment method, such as activated sludge method, although widely used, has low treatment efficiency, high energy consumption and large land occupation, and cannot meet the current high-efficiency treatment demand of low-carbon-source aquaculture sewage. MBR technology successfully solves the problems existing in traditional activated sludge method, such as sludge bulking, low sludge content and large amount of residual sludge, through aeration flushing. In addition, it utilizes the adsorption and microbial degradation of biofilm and the strong adsorption performance of activated carbon to efficiently remove organic matter, nitrogen, phosphorus and other pollutants in aquaculture sewage.

[0003] The traditional aquaculture sewage treatment method, such as activated sludge method, although widely used, has low treatment efficiency, high energy consumption and large land occupation, and cannot meet the current high-efficiency treatment demand of low-carbon-source aquaculture sewage. MBR technology successfully solves the problems existing in traditional activated sludge method, such as sludge bulking, low sludge content and large amount of residual sludge, through aeration flushing. In addition, it utilizes the adsorption and microbial degradation of biofilm and the strong adsorption performance of activated carbon to efficiently remove organic matter, nitrogen, phosphorus and other pollutants in aquaculture sewage.

[0004] ​MBCR (MBR-activated carbon-activated sludge) process is a process based on MBR process, which adds flocculants into the MBR reactor. The flocculants can slow down the membrane pollution and fully exert the advantages of MBR process, so that the system can achieve better treatment effect. At present, MBCR process has been widely used as an advanced wastewater treatment technology. It combines membrane separation and biodegradation mechanisms, and can efficiently remove organic matter, ammonia nitrogen and phosphate in water, and the effluent indicators meet the relevant discharge standards. However, there are still some problems in the treatment of low-carbon freshwater aquaculture wastewater by MBCR process. Firstly, the amount of activated carbon is large. Secondly, PVDF membrane, as the most widely used filter membrane, has excellent chemical stability and physical properties, but its hydrophilicity is poor, which can be easily polluted by organic matter in water, resulting in a decrease in membrane flux and an increase in energy consumption, and cannot be operated stably for a long time, which limits its application in the treatment of low-carbon freshwater aquaculture wastewater. Therefore, how to improve the hydrophilicity of PVDF membrane and enhance its anti-pollution and stability is an urgent problem to be solved in the treatment of low-carbon freshwater aquaculture wastewater by MBCR process. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application proposes a new MBCR process specially used for treating low-carbon freshwater aquaculture wastewater. This technology aims to improve the performance of PVDF membrane by using sludge improver, improve the efficiency and stability of membrane separation, and slow down the membrane pollution, so as to realize the efficient, stable and low-energy consumption treatment of freshwater aquaculture wastewater. This technology makes full use of membrane separation, biodegradation, physical adsorption and other mechanisms, and provides a new scheme for the environmentally friendly treatment of freshwater aquaculture wastewater.

[0006] The technical scheme of the present application is as follows:

[0007] A method for treating low-carbon wastewater by MBCR process, characterized in that it comprises:

[0008] An MBR reactor is built, and low-carbon wastewater is introduced into the membrane bioreactor for filtration treatment by a membrane assembly. The membrane assembly is a modified PVDF piezoelectric beta crystal hollow fiber ultrafiltration membrane, and the sludge improver comprises chitosan or sodium alginate.

[0009] The addition of sludge improver can improve the properties of sludge, increase the settling performance of sludge, slow down the membrane pollution, and fully exert the advantages of MBR process. The traditional PVDF ultrafiltration membrane is replaced by a PVDF piezoelectric beta crystal ultrafiltration membrane to solve the problems of low piezoelectricity and limited permeability of the traditional PVDF ultrafiltration membrane, and to improve the efficiency and stability of membrane separation. The PVDF piezoelectric beta crystal ultrafiltration membrane has high surface area and conductivity, and can efficiently remove pollutants, thereby improving the overall wastewater treatment efficiency.

[0010] Preferably, the sludge improver is added in an amount of at least 12 mg / L.

[0011] Preferably, the sludge improver is sodium alginate.

[0012] Preferably, the method for preparing the modified PVDF piezoelectric beta crystal hollow fiber type ultrafiltration membrane comprises the following steps:

[0013] (1) Preparation of modified PVDF: PVDF powder is mixed with an organic base and placed in a reactor for reaction;

[0014] (2) Modified PVDF obtained in step (1), carboxylated graphene oxide powder, catalyst, pore former 1, plasticizer, pore former 2 are sequentially added to N,N-dimethylacetamide solution, and ultrasonic stirring is performed after the addition of each material, and a composite base membrane casting solution is obtained after the completion of material addition; or modified PVDF obtained in step (1), carboxylated graphene oxide powder, catalyst, plasticizer, pore former 1, pore former 2 are sequentially added to N,N-dimethylacetamide solution, and ultrasonic stirring is performed after the addition of each material, and a composite base membrane casting solution is obtained after the completion of material addition;

[0015] The pore former 1 is hexadecyl trimethyl ammonium bromide, and the pore former 2 is sodium dodecyl sulfate;

[0016] (3) The composite base membrane casting solution obtained in step (2) is added to a methanol aqueous solution for phase inversion to obtain a PVDF ultrafiltration membrane;

[0017] (4) The PVDF ultrafiltration membrane obtained in step (3) is mechanically stretched, and then subjected to electric field polarization by using a polarization device to obtain a PVDF beta crystal piezoelectric ultrafiltration membrane.

[0018] Preferably, the mass ratio of PVDF powder to organic base is 100:6.

[0019] Preferably, the ultrasonic time is 0.5-1 h each time.

[0020] Preferably, the mass ratio of modified PVDF, carboxylated graphene oxide powder, catalyst, pore former 1, plasticizer, pore former 2 is 10-14:5-8:5-10:4-7:5-9:50-60.

[0021] Preferably, the polarization electric field intensity is 90 MV / m.

[0022] Preferably, the low-carbon source freshwater aquaculture sewage has the following indexes: COD Cr 138-175 mg / L, TP 5.05-8.3 mg / L, TN 35.36-51.73 mg / L.

[0023] The application of the method in treating low-carbon-source freshwater aquaculture wastewater also belongs to the protection scope of the present application.

[0024] The beneficial effects of the present application are:

[0025] (1) Improve wastewater treatment efficiency: The use of MBCR process and PVDF piezoelectric beta crystal ultrafiltration membrane can significantly improve the treatment efficiency of low-carbon-source freshwater aquaculture wastewater. The addition of a small amount of sludge modifier in the MBCR process can improve the properties of the sludge, slow down the membrane fouling, increase the settling performance of the sludge, and thus improve the removal efficiency. At the same time, the PVDF piezoelectric beta crystal ultrafiltration membrane has high surface area and conductivity, which can efficiently remove high molecular substances such as humic acid, so that the overall wastewater treatment efficiency is significantly improved.

[0026] (2) Enhance system stability: The application of MBCR process can improve the stability and impact load capacity of the system. The addition of sludge modifier improves the sludge properties, slows down the membrane fouling, reduces the membrane cleaning frequency, and thus prolongs the service life of the membrane module and enhances the stability of the system.

[0027] (3) Improve membrane separation efficiency and stability: The improved PVDF piezoelectric beta crystal ultrafiltration membrane has high piezoelectric performance and permeability in the membrane separation process, which improves the separation efficiency and stability of the membrane. This will help to prolong the service life of the membrane, reduce the frequency of membrane replacement, and reduce the operation and maintenance cost.

[0028] (4) Reduce energy consumption and cost: Due to the high removal capacity of MBCR process, the system can complete the treatment in a shorter time, reducing the energy consumption and chemical dosage during the treatment process. At the same time, the PVDF piezoelectric beta crystal ultrafiltration membrane has good mechanical properties and corrosion resistance, prolonging the service life of the membrane module and reducing the operation cost of the system.

[0029] (5) Promote sustainable use of water resources: The present application realizes efficient treatment of low-carbon-source freshwater aquaculture wastewater, which effectively utilizes and reuses water resources. This has a positive role in alleviating water resource shortage and water environmental pollution problems.

[0030] (6) Improve treatment applicability: The present application improves the PVDF membrane material to have piezoelectric beta crystal performance, thereby expanding the separation capacity and application range of the membrane. It can more efficiently remove organic matter and high molecular substances in low-carbon-source freshwater aquaculture wastewater, and is suitable for different types of wastewater treatment scenarios.

[0031] In summary, the effect and benefit brought by the present application include improving the treatment efficiency, improving the removal efficiency of low-carbon-source sewage, improving the membrane separation efficiency and stability, reducing the energy consumption and operation and maintenance cost, promoting the sustainable utilization of water resources, and promoting the technological innovation and application promotion. These effects will bring important social, economic and environmental benefits to the field of low-carbon-source freshwater aquaculture sewage treatment. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A schematic diagram of the MBCR process experiment in Example 1 of the present application;

[0033] Figure 2 A modified PVDF piezoelectric beta crystal hollow fiber membrane module in Example 1 of the present application. DETAILED DESCRIPTION

[0034] In order to better understand the technical content of the present application, the following specific examples are provided to further illustrate the present application.

[0035] Preparation method of modified PVDF piezoelectric beta crystal ultrafiltration membrane module in Example 1

[0036] (1) Preparation of modified PVDF: PVDF powder and organic base (ethanolamine) were mixed in a mass ratio of 100:6 and put into a reactor, and reacted at 60±2℃ for 10 min.

[0037] (2) Modified PVDF, carboxylated graphene oxide powder, catalyst (equal mass of 3-aminopropyl triethoxysilane and vinyl trimethoxysilane), pore former 1 (hexadecyl trimethyl ammonium bromide), plasticizer (phthalate), pore former 2 (sodium dodecyl sulfate) were sequentially added to DMAC (N,N-dimethylacetamide) solution, and each material was subjected to ultrasonic stirring for 0.5 h after being added to the DMAC solution. After the addition of materials was completed, a composite base membrane casting solution was obtained;

[0038] The mass ratio of modified PVDF, carboxylated graphene oxide powder, catalyst, pore former 1, plasticizer, and pore former 2 is 10:5:5:4:9:60.

[0039] (3) The composite base membrane casting solution obtained in step (2) was added to a 30% volume concentration methanol aqueous solution for phase inversion to obtain a PVDF ultrafiltration membrane;

[0040] (4) The PVDF ultrafiltration membrane obtained in step (3) was subjected to mechanical stretching (uniaxial stretching, stretching temperature 70℃), and then subjected to electric field polarization (polarization electric field intensity 90MV / m) using a polarization device to obtain a PVDF beta crystal piezoelectric ultrafiltration membrane.

[0041] (5) The PVDF beta crystal piezoelectric ultrafiltration membrane prepared in step (4) was assembled into a membrane module.

[0042] (6) MBCR reactor assembly: Assemble the prepared PVDF piezoelectric β crystal ultrafiltration membrane module with other components of the MBCR reactor (such as the reaction tank, water inlet pipeline, water outlet pipeline, etc.) to form a complete MBCR reactor.

[0043] The carboxylated graphite oxide can be selected from commercially available products or prepared by conventional methods. In this embodiment, a self-prepared product is selected.

[0044] Preparation method of carboxylated graphite oxide:

[0045] Weigh 0.2 g of graphene oxide and add it to 100 mL of sodium hydroxide aqueous solution (10 mg / mL) and ultrasonically disperse for 2 h. Then add 1 g of chloroacetic acid and continue to ultrasonically disperse for 2 h. Repeat the centrifugal washing until neutral. Obtain a carboxylated graphene oxide solution. Centrifuge the solution, remove the supernatant, and dry for use.

[0046] Preparation method of modified PVDF piezoelectric β crystal ultrafiltration membrane module in Example 2

[0047] Compared with Example 1, the addition order of the porogen and plasticizer is adjusted in this embodiment.

[0048] (1) Preparation of modified PVDF: Mix PVDF powder with organic base (ethanolamine) at a mass ratio of 100:6 and put it into a reactor. React at 60±2℃ for 10 min.

[0049] (2) Add modified PVDF obtained in step (1), carboxylated graphene oxide powder, catalyst (equal mass of 3-aminopropyltriethoxysilane and vinyltrimethoxysilane), plasticizer (phthalate), porogen 1 (hexadecyltrimethylammonium bromide), and porogen 2 (sodium dodecyl sulfate) into DMAC (N,N-dimethylacetamide) solution in sequence. Ultrasonically stir for 0.5 h after each material is added into the DMAC solution. After the addition of all materials, a composite base membrane casting solution is obtained.

[0050] The mass ratio of modified PVDF, carboxylated graphene oxide powder, catalyst, porogen 1, plasticizer, and porogen 2 is 10:5:5:4:9:60.

[0051] (3) Add the composite base membrane casting solution obtained in step (2) into a 30% volume concentration methanol aqueous solution for phase inversion to obtain a PVDF ultrafiltration membrane.

[0052] (4) Mechanically stretch (uniaxial stretching, stretching temperature 70℃) the PVDF ultrafiltration membrane obtained in step (3), and then use a polarization device for electric field polarization (polarization electric field intensity 90 MV / m) to obtain a PVDF β crystal piezoelectric ultrafiltration membrane.

[0053] (5) Assembling the PVDF β-crystal piezoelectric ultrafiltration membrane prepared in step (4) into a membrane module.

[0054] (6) MBCR reactor assembly: Assembling the PVDF β-crystal piezoelectric ultrafiltration membrane module prepared in step (5) with other components (such as a reaction tank, a water inlet pipeline, a water outlet pipeline, etc.) of the MBCR reactor to form a complete MBCR reactor.

[0055] The carboxylated graphite oxide can be selected from commercially available products or prepared by conventional methods. In this embodiment, a self-prepared product is selected.

[0056] Preparation method of carboxylated graphite oxide:

[0057] 0.2 g of graphene oxide was weighed and added to 100 mL of sodium hydroxide aqueous solution (10 mg / mL) and ultrasonically dispersed for 2 h, then 1 g of chloroacetic acid was added and ultrasonically dispersed for another 2 h. The mixture was repeatedly centrifuged and washed with water until neutral. A carboxylated graphene oxide solution was obtained. The solution was centrifuged to remove the supernatant and dried for later use.

[0058] Preparation method of modified PVDF piezoelectric β-crystal ultrafiltration membrane module in Example 3

[0059] (1) Preparation of modified PVDF: PVDF powder and organic base (ethanolamine) were mixed in a mass ratio of 100:6 and placed in a reactor, and reacted at 60±2°C for 10 min.

[0060] (2) Modified PVDF obtained in step (1), carboxylated graphene oxide powder, catalyst (equal mass of 3-aminopropyltriethoxysilane and vinyltrimethoxysilane), plasticizer (phthalate), porogen 1 (cetyltrimethylammonium bromide), and porogen 2 (sodium dodecyl sulfate) were sequentially added to a DMAC (N,N-dimethylacetamide) solution. After each material was added to the DMAC solution, ultrasonic stirring was performed for 1 h. After the addition of all materials, a composite base membrane casting solution was obtained.

[0061] The mass ratio of modified PVDF, carboxylated graphene oxide powder, catalyst, porogen 1, plasticizer, and porogen 2 was 14:8:10:7:5:50.

[0062] (3) The composite base membrane casting solution obtained in step (2) was added to a 30% volume concentration methanol aqueous solution for phase inversion to obtain a PVDF ultrafiltration membrane.

[0063] (4) The PVDF ultrafiltration membrane obtained in step (3) was subjected to mechanical stretching (uniaxial stretching, stretching temperature 70°C), and then an electric field polarization device was used for electric field polarization (polarization electric field strength 90 MV / m) to obtain a PVDF β-crystal piezoelectric ultrafiltration membrane.

[0064] (5) Assemble the PVDFβ crystal piezoelectric ultrafiltration membrane prepared in step (4) into a membrane module.

[0065] (6) MBCR reactor assembly: The prepared PVDF piezoelectric β crystal ultrafiltration membrane module is assembled with other components of the MBCR reactor (such as reaction tank, inlet pipe, outlet pipe, etc.) to form a complete MBCR reactor.

[0066] The carboxylated graphite oxide can be a commercially available product or prepared using conventional methods. In this embodiment, a self-made product is selected.

[0067] Preparation method of carboxylated graphite oxide:

[0068] Weigh 0.2g of graphene oxide and add it to 100mL of sodium hydroxide aqueous solution (10mg / mL). Disperse the solution by sonication for 2h, then add 1g of chloroacetic acid and continue sonication for 2h. Repeatedly centrifuge and wash with water until neutral to obtain a carboxylated graphene oxide solution. Centrifuge the solution, remove the supernatant, and dry it for later use.

[0069] Example 4: Method for treating low-carbon source wastewater using the MBCR process

[0070] Prepare low-carbon source freshwater aquaculture wastewater (COD) Cr 138–175 mg / L, TP 5.05–8.3 mg / L, TN 35.36–51.73 mg / L). An integrated MBR reactor was constructed. Figure 1 The membrane module used is the modified PVDF piezoelectric β-crystal hollow fiber ultrafiltration membrane described in Example 1. A sludge conditioner (chitosan, dosage 12 mg / L) is added to the reactor. Each reactor is aerated via a blower connected to a flow meter to control the aeration rate. One influent peristaltic pump, one effluent peristaltic pump, and one backwash peristaltic pump are provided. A magnetic stirrer is used to agitate the sludge in the reactor. A vacuum pressure gauge is connected to the membrane module to measure the membrane pressure, ensuring constant pressure effluent. The influent pump is started to deliver low-carbon source freshwater aquaculture wastewater into the reactor, maintaining a stable flow rate and temperature. The aerator and stirrer are started to maintain good aeration and agitation in the reactor to promote microbial growth and mixing. The reactor operates on a cycle of approximately 12 hours, with two cycles per day. During influent intake, the magnetic stirrer is activated with an influent flow rate of 3L, followed by 9 hours of aeration. After 25 minutes of effluent discharge (approximately 3L), backwashing is performed for 1 minute. The magnetic stirrer is deactivated half an hour before effluent discharge, allowing the reactor to stand. The reactor operates continuously without idle periods. Water quality parameters in the reactor, including COD, ammonia nitrogen, and total phosphorus, are monitored. Samples are taken periodically for analysis, and data are recorded. Experimental comparisons and analyses are conducted based on the monitoring results to evaluate the treatment efficacy and stability of the MBCR process for low-carbon-source freshwater aquaculture wastewater.

[0071] Example 5 Method for treating low-carbon source sewage by MBCR process

[0072] Prepare low-carbon source aquaculture sewage (COD Cr 138-175 mg / L, TP 5.05-8.3 mg / L, TN 35.36-51.73 mg / L). Build an integrated MBR reactor, and use the modified PVDF piezoelectric beta crystal hollow fiber ultrafiltration membrane described in Example 1 for the membrane assembly. Add sludge modifier (sodium alginate, dosage 12 mg / L) to the reactor. Each reactor is connected to a flowmeter by a blower to control the aeration amount. There is one peristaltic pump for water inlet, one peristaltic pump for water outlet, and one peristaltic pump for backwashing. There is one magnetic stirrer to stir the sludge in the reactor. The membrane assembly is connected to a vacuum pressure gauge to measure the membrane pressure and ensure constant pressure water outlet. Start the water inlet pump and send the low-carbon source aquaculture sewage into the reactor, maintaining a stable flow rate and temperature. Start the aerator and stirrer to maintain good aeration and stirring in the reactor to promote microbial growth and mixing. The reactor operates for about 12 h, with two cycles per day. Turn on the magnetic stirrer when feeding, with a water inlet amount of 3 L, an aeration time of 9 h, a water outlet time of 25 min, a water outlet amount of about 3 L, and a backwashing time of 1 min. Turn off the magnetic stirrer half an hour before water outlet to allow the water to be discharged. The reactor is continuously operated without idling. Monitor the water quality parameters in the reactor, including COD, ammonia nitrogen, total phosphorus, and other indicators. Take samples regularly for analysis and record the data. Compare and analyze the experimental results based on the monitoring results to evaluate the treatment effect and stability of the MBCR process on low-carbon source aquaculture sewage.

[0073] Example 6 Method for treating low-carbon source sewage by MBCR process

[0074] Continue to use the reactor of Example 5. Monitor the water quality indicators every two days and record the data. Take samples regularly for analysis of COD, ammonia nitrogen, total phosphorus, and other indicators to evaluate the continuous treatment effect of the MBCR process. Observe the sludge state and membrane assembly in the reactor to analyze the influence of the MBCR process on system stability.

[0075] Example 7

[0076] Replace the modified PVDF piezoelectric beta crystal hollow fiber ultrafiltration membrane used in Example 5 with the modified PVDF piezoelectric beta crystal hollow fiber ultrafiltration membrane described in Example 2. Other conditions remain unchanged. Monitor the water quality indicators every two days and record the data. Take samples regularly for analysis of COD, ammonia nitrogen, total phosphorus, and other indicators to evaluate the continuous treatment effect of the MBCR process. Observe the sludge state and membrane assembly in the reactor to analyze the influence of the MBCR process on system stability.

[0077] Comparative Example 1 Method for treating low-carbon source sewage by MBCR process

[0078] Comparative Example 1 differs from Example 4 in that no sludge improver is added.

[0079] Prepare low-carbon freshwater aquaculture wastewater (COD Cr 138-175 mg / L, TP 5.05-8.3 mg / L, TN 35.36-51.73 mg / L). Build an integrated MBR reactor, and select the PVDF piezoelectric beta crystal hollow fiber ultrafiltration membrane modified in Example 1 for the membrane assembly. The reactor is aerated by connecting a flowmeter to an air blower to control the aeration amount, and one each of a peristaltic pump for water inlet, a peristaltic pump for water outlet, and a peristaltic pump for backwashing, as well as a magnetic stirrer for stirring the sludge in the reactor, a vacuum pressure gauge connected to the membrane assembly to measure the membrane pressure and ensure constant pressure water outlet. The reactor operates for 12 h, two cycles per day. The magnetic stirrer is turned on when water is fed, and the sludge-water mixture is stirred. The water inlet amount is 3 L, the aeration time is 9 h, the water outlet time is 25 min, the water outlet amount is about 3 L, the backwashing time is 1 min, and the magnetic stirrer is turned off half an hour before water outlet to allow the reactor to stand for water outlet. The reactor is continuously operated without idling. Monitor the water quality parameters in the reactor, including COD, ammonia nitrogen, total phosphorus, and other indicators. Take samples regularly for analysis and record the data.

[0080] Performance test

[0081] (1) Analysis of water quality index removal effect

[0082] Analyze the water inlet and outlet of the reactor in the examples and Comparative Example 1. Take a sample from the water outlet and inlet every two days to measure the indicators of the water sample. Since the MBCR method discharges water through the membrane assembly, the PVDF ultrafiltration membrane assembly has a filtration precision of 0.1 μm, which is less than the water sample measurement filtration precision, so the water outlet sample does not need to be filtered. The measured indicators include CODcr, TN, PO4 3- , NH4 + -N.

[0083] The data in Table 1 for Example 4 and Example 5 are the results detected after two days of operation, and the data for Example 6 and Example 7 are the results after 60 days of operation.

[0084] (2) Analysis of sludge conditions

[0085] Determine the sludge settling ratio (SV), sludge concentration (MLSS), and sludge index (SVI) in the reactors of Examples 4-7 and Comparative Example.

[0086] (3) Test results

[0087] Table 1

[0088]

[0089] According to the experimental data and analysis results, the MBCR process shows good effect in treating low-carbon freshwater aquaculture wastewater. The addition of sludge modifier can significantly improve the sludge properties, slow down the membrane pollution, maintain high water output and improve the pollutant removal rate, fully exert the advantages of MBR process, and make the system achieve better treatment effect. The removal efficiency of sodium alginate and chitosan addition group is slightly higher than that of sodium alginate addition group, but the effect of the two sludge modifiers is significantly better than that of the control group. It can be seen that the addition of sodium alginate and chitosan can effectively improve the sludge properties and improve the pollutant removal efficiency, providing a feasible technical solution for efficient treatment of low-carbon freshwater aquaculture wastewater. Through the continuous stability verification, the MBCR process shows good continuous treatment effect. In the long-term operation process, the removal efficiency of the MBCR reactor is basically stable at a high level, the sludge state is good, and the membrane assembly is lightly polluted. By comparing the results of example 6 and example 7, it can be known that the modified filter membrane prepared in example 1 (optimizing the use time of pore-forming agent) can obviously improve the long-term operation effect of the filter membrane.

[0090] The above only describes some embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application falls within the protection scope of the present application.

Claims

1. A method for treating low-carbon source wastewater using the MBCR process, characterized in that, include: An MBR reactor was constructed, and low-carbon source wastewater was fed into the membrane bioreactor for filtration through a membrane module, which was a modified PVDF piezoelectric β-crystal hollow fiber ultrafiltration membrane. A sludge improver, sodium alginate, was added to the reactor. The method for preparing the modified PVDF piezoelectric β-crystal hollow fiber ultrafiltration membrane is as follows: (1) Preparation of modified PVDF: PVDF powder is mixed with organic base and placed in a reactor for reaction; (2) The modified PVDF, carboxylated graphene oxide powder, catalyst, pore-forming agent 1, plasticizer and pore-forming agent 2 obtained in step (1) are added to N,N-dimethylacetamide solution in sequence. Each material is ultrasonically stirred after being added. After the materials are added, the composite base film casting solution is obtained. The porogen 1 is hexadecyltrimethylammonium bromide, and the porogen 2 is sodium dodecyl sulfate; (3) The composite base membrane casting solution obtained in step (2) is added to a methanol aqueous solution for phase inversion to obtain a PVDF ultrafiltration membrane; (4) The PVDF ultrafiltration membrane obtained in step (3) is mechanically stretched and then electrically polarized using a polarization device to obtain a PVDF β crystal piezoelectric ultrafiltration membrane.

2. The method according to claim 1, characterized in that, The amount of the sludge improver added is at least 12 mg / L.

3. The method according to claim 1, characterized in that, The mass ratio of PVDF powder to organic alkali is 100:

6.

4. The method according to claim 1, characterized in that, Each ultrasound session lasts 0.5-1 hour.

5. The method according to claim 1, characterized in that, The mass ratio of modified PVDF, carboxylated graphene oxide powder, catalyst, porogen 1, plasticizer, and porogen 2 is 10-14:5-8:5-10:4-7:5-9:50-60.

6. The method according to claim 1, characterized in that, The polarization electric field strength is 90 MV / m.

7. The method according to claim 1, characterized in that, The low-carbon source wastewater is low-carbon source freshwater aquaculture wastewater, and the indicators of the low-carbon source freshwater aquaculture wastewater are COD. Cr 138~175 mg / L, TP 5.05~8.3 mg / L, TN35.36~51.73 mg / L.

8. The application of the method according to any one of claims 1 to 7 in the treatment of low-carbon source freshwater aquaculture wastewater.

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