Method and system for treating N-methyl pyrrolidone wastewater

Abstract

The invention discloses an N-methyl pyrrolidone wastewater treatment method which comprises the following steps: S1, pretreatment: collecting and storing production wastewater, homogenizing and homogenizing water quality, pressurizing and lifting the wastewater, and waiting for subsequent treatment; s2, electrochemical treatment: pre-degrading the pretreated production wastewater, and improving the biodegradability of the wastewater; and S3, biochemical treatment: firstly carrying out anaerobic biochemical treatment on the production wastewater subjected to electrochemical treatment, then carrying out anoxic and aerobic process treatment, and finally filtering through an MBR (Membrane Bioreactor) membrane. Meanwhile, the invention further discloses an N-methyl pyrrolidone wastewater treatment system. According to the method, the electrochemical process, the UASB anaerobic process, the AO biochemical process and the MBR membrane filtration process are combined, the high-COD N-methyl pyrrolidone wastewater is treated, the treatment effect is remarkable, the requirement that the treated wastewater reaches the second-class standard of the electronic industrial pollutant discharge standard can be met, and the effluent quality is stable.

Description

Technical Field

[0001] The invention relates to a method and a system for treating N-methylpyrrolidone wastewater, belonging to the technical field of sewage treatment. Background Art

[0002] N-methylpyrrolidone (NMP) wastewater mainly comes from multiple links in the lithium battery production process. Specifically, NMP volatilizes as a solvent in the batching, coating and drying processes of the lithium battery cathode, and the waste gas generated passes through the recovery device to form NMP waste liquid. In addition, in the chemical production process, the process using NMP as a solvent will also produce wastewater containing high concentrations of COD and ammonia nitrogen. These wastewaters not only include distillation wastewater and amination wastewater in the lithium battery production process, but also involve industrial production in the fields of semiconductors, chemical fibers, fine chemicals, etc.

[0003] The sources of NMP wastewater can be summarized as follows: (1) Lithium battery production: including NMP volatilization and waste gas treatment in the batching, coating and drying processes. (2) Chemical production: various chemical production processes using NMP as a solvent. (3) Other industrial fields: such as semiconductors, chemical fibers and fine chemicals. These wastewaters have high concentrations of COD and ammonia nitrogen, and belong to the type of organic wastewater that is difficult to degrade, making them difficult to treat. Therefore, we propose a method and system for treating N-methylpyrrolidone wastewater. Summary of the invention

[0004] The object of the present invention is to provide a method for treating N-methylpyrrolidone wastewater, and also to provide an N-methylpyrrolidone wastewater treatment system. The present invention has good treatment effect on high COD wastewater, stable effluent quality, and can meet the requirements of Class II standard (indirect emission standard) (GB 39731-2020) of the electronic industry pollutant emission standard.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solution: a method for treating N-methylpyrrolidone wastewater, comprising the following steps:

[0006] S1, pre-treatment, collecting and storing production wastewater, homogenizing and balancing the water quality, pressurizing and lifting the wastewater, and waiting for subsequent treatment;

[0007] S2. Electrochemical treatment: pre-degrade the pre-treated production wastewater and improve the biodegradability of the wastewater. The electrochemical process has a high removal rate for organic pollutants, and the COD removal rate can reach 30-90%. It can non-selectively degrade the refractory toxic organic matter in the wastewater into carbon dioxide, water and minerals, and convert the non-biodegradable high-molecular organic matter into small-molecule compounds that can be biochemically treated, thereby improving the biodegradability of the wastewater.

[0008] S3, biochemical treatment, the production wastewater after electrochemical treatment is first subjected to anaerobic biochemical treatment, then anoxic aerobic process treatment, and finally completed after MBR membrane filtration. MBR replaces the sedimentation tank to intercept sludge and SS to complete the wastewater treatment to meet the standards.

[0009] The aforementioned N-methylpyrrolidone wastewater treatment method also includes disinfection treatment, sterilizing and disinfecting the biochemically treated water, and also has a partial removal effect on residual COD and ammonia nitrogen.

[0010] In the aforementioned method for treating N-methylpyrrolidone wastewater, the disinfection treatment is performed by adding sodium hypochlorite to the wastewater.

[0011] In the aforementioned N-methylpyrrolidone wastewater treatment method, in step S1, after homogenizing and equalizing the water quality, flocculants and coagulants are added to the collected and stored production wastewater, and the pH is adjusted to 6-6.5.

[0012] In the aforementioned N-methylpyrrolidone wastewater treatment method, the flocculant and coagulant are PAC and PAM respectively, and the pH is adjusted by adding alkali to the production wastewater.

[0013] In the aforementioned N-methylpyrrolidone wastewater treatment method, the electrochemical treatment in step S2 uses a CME electrochemical system to electrochemically oxidize the wastewater, pre-degrade the wastewater, remove part of the COD, and improve the biodegradability of the wastewater. The electrochemical process has a high removal rate for organic pollutants, and the COD removal rate can reach 30-90%. It can non-selectively degrade the refractory toxic organic matter in the wastewater into carbon dioxide, water and minerals, and convert the non-biodegradable high-molecular organic matter into small-molecule compounds that can be biochemically treated, thereby improving the biodegradability of the wastewater.

[0014] The aforementioned N-methylpyrrolidone wastewater treatment method, the biochemical treatment of step S3 includes anaerobic treatment, A / O treatment and MBR membrane filtration treatment, the anaerobic treatment adopts an upflow anaerobic sludge bed process for anaerobic biochemical treatment, chain breaking and decomposition of macromolecular organic matter, producing small molecular organic acids, some of which are incompletely oxidized into organic matter such as methane, thereby improving the biodegradability of the wastewater, in the A / O treatment process, the anoxic aerobic process section removes most of the COD in the water and decomposes it into water and CO2, and nitrification and denitrification of ammonia nitrogen and organic nitrogen are treated to generate nitrogen gas removal system, complete the degradation of total nitrogen, and at the same time, urea and sodium dihydrogen phosphate are added to the wastewater.

[0015] The aforementioned N-methylpyrrolidone wastewater treatment method also includes sludge treatment. Part of the sludge produced by MBR membrane filtration is returned to the A / O treatment process for utilization, and the other part is concentrated and filtered using a plate and frame dehydrator.

[0016] An N-methylpyrrolidone wastewater treatment system comprises a regulating tank, wherein a water outlet of the regulating tank is connected to a water inlet of an electrochemical reaction tank, the water outlet of the electrochemical reaction tank is connected to a water inlet of a biochemical regulating tank, the water outlet of the biochemical regulating tank is connected to a water inlet of a UASB anaerobic tank, the water outlet of the UASB anaerobic tank is connected to a water inlet of an anoxic tank, the water outlet of the anoxic tank is connected to a water inlet of an aerobic tank, the water outlet of the aerobic tank is connected to a water inlet of an MBR tank, a sludge output end of the MBR tank is connected to the UASB anaerobic tank, a water outlet end of an MBR device in the MBR tank is connected to a disinfection tank, the water outlet end of the disinfection tank is connected to a clean water tank, and a sludge output end of the MBR tank is connected to a sludge treatment device.

[0017] The aforementioned N-methylpyrrolidone wastewater treatment system also includes an aeration system, the aeration system is connected to the aerobic tank and the MBR tank respectively, the aeration system includes a blower, an aeration pipe, and an aeration head, the output end of the blower is connected to the aeration pipe through a pipeline, there are at least two aeration pipes, the aeration pipes are arranged at the bottom of the aerobic tank and the MBR tank, the aeration heads are evenly distributed on the aeration pipes, the aeration pipes include a main pipe and a branch pipe, the branches are evenly distributed on both sides of the main pipe, and the angle between the main pipe and the branch pipe is The angle is 15°-35°, and the cross-sectional area of ​​the main pipe cavity is larger than the sum of the cross-sectional areas of the branch pipe cavities. The aeration heads are evenly distributed on the upper sides of the branch pipes. The different resistance losses of the branch pipes in the multi-branch parallel pipeline are the direct cause of the uneven flow distribution of the branch pipes. The inclined branch part can reduce the resistance loss of the branch pipe. The consistent angle can make the branch pipe resistance of each branch part the same. When the total resistance loss of each branch pipe in the parallel pipeline is small, the ratio of the cross-sectional area of ​​the main pipe to the sum of the cross-sectional areas of each branch pipe is greater than the design, and the flow distribution uniformity of each branch pipe is better. A check valve is provided on the connecting pipe between the blower and the aeration pipe fitting.

[0018] Compared with the prior art, the present invention mainly adopts a combination of electrochemical process, UASB anaerobic process, AO biochemical process and MBR membrane filtration process to treat high COD N-methylpyrrolidone wastewater, and the treatment effect is significant. The wastewater can meet the requirements of Class II standard of pollutant emission standard for electronic industry (indirect emission standard) (GB 39731-2020) after wastewater treatment, and the effluent water quality is stable. At the same time, the aeration volume of the aeration system of the present invention is uniform and stable, which significantly improves the treatment effect of AO biochemical process and MBR membrane filtration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flow chart of the processing method of the present invention;

[0020] Figure 2is a schematic diagram of the processing system of the present invention;

[0021] Figure 3 It is a schematic diagram of the structure of the invented aeration system;

[0022] Figure 4 It is a schematic diagram of the aeration tube structure of the present invention.

[0023] Figure numerals: 1-regulating tank, 2-electrochemical reaction tank, 3-branch pipe, 4-UASB anaerobic tank, 5-anoxic tank, 6-aerobic tank, 7-MBR tank, 8-disinfection tank, 9-clear water tank, 10-sludge treatment device, 11-aeration system, 12-blower, 13-aeration pipe fittings, 14-aeration head, 15-main pipe.

[0024] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0025] Embodiment 1 of the present invention: A method for treating N-methylpyrrolidone wastewater, comprising the following steps:

[0026] S1, pre-treatment, collecting and storing production wastewater, homogenizing and balancing the water quality, pressurizing and lifting the wastewater, and waiting for subsequent treatment;

[0027] S2. Electrochemical treatment: pre-degrade the pre-treated production wastewater and improve the biodegradability of the wastewater. The electrochemical process has a high removal rate for organic pollutants, and the COD removal rate can reach 30-90%. It can non-selectively degrade the refractory toxic organic matter in the wastewater into carbon dioxide, water and minerals, and convert the non-biodegradable high-molecular organic matter into small-molecule compounds that can be biochemically treated, thereby improving the biodegradability of the wastewater.

[0028] S3, biochemical treatment, the production wastewater after electrochemical treatment is first subjected to anaerobic biochemical treatment, then anoxic aerobic process treatment, and finally completed after MBR membrane filtration. MBR replaces the sedimentation tank to intercept sludge and SS to complete the wastewater treatment to meet the standards.

[0029] The present invention adopts a combination of electrochemical process, UASB anaerobic process, AO biochemical process and MBR membrane filtration process to treat high COD N-methylpyrrolidone wastewater, and the treatment effect is remarkable. It can meet the requirements of Class II standard of pollutant emission standard for electronic industry (indirect emission standard) (GB 39731-2020) after wastewater treatment, and the effluent water quality is stable.

[0030] Embodiment 2 of the present invention: A method for treating N-methylpyrrolidone wastewater, comprising the following steps:

[0031] S1, pre-treatment, collecting and storing production wastewater, homogenizing and balancing the water quality, pressurizing and lifting the wastewater, and waiting for subsequent treatment;

[0032] S2. Electrochemical treatment: pre-degrade the pre-treated production wastewater and improve the biodegradability of the wastewater. The electrochemical process has a high removal rate for organic pollutants, and the COD removal rate can reach 30-90%. It can non-selectively degrade the refractory toxic organic matter in the wastewater into carbon dioxide, water and minerals, and convert the non-biodegradable high-molecular organic matter into small-molecule compounds that can be biochemically treated, thereby improving the biodegradability of the wastewater.

[0033] S3, biochemical treatment, the production wastewater after electrochemical treatment is first subjected to anaerobic biochemical treatment, then anoxic aerobic process treatment, and finally completed after MBR membrane filtration. MBR replaces the sedimentation tank to intercept sludge and SS to complete the wastewater treatment to meet the standards.

[0034] It also includes disinfection treatment, which sterilizes and disinfects the biochemically treated water and has a partial removal effect on residual COD and ammonia nitrogen. The disinfection treatment is to add sodium hypochlorite to the wastewater.

[0035] The present invention adopts a combination of electrochemical process, UASB anaerobic process, AO biochemical process and MBR membrane filtration process to treat high COD N-methylpyrrolidone wastewater, and the treatment effect is remarkable. It can meet the requirements of Class II standard of pollutant emission standard for electronic industry (indirect emission standard) (GB 39731-2020) after wastewater treatment, and the effluent water quality is stable.

[0036] Embodiment 3 of the present invention: A method for treating N-methylpyrrolidone wastewater, comprising the following steps:

[0037] S1, pretreatment, collecting and storing production wastewater, homogenizing and averaging the water quality, and then adding flocculants and coagulants to the collected and stored production wastewater, wherein the flocculants and coagulants are PAC and PAM respectively, and adjusting the pH to 6-6.5 by adding alkali to the production wastewater, and pressurizing and lifting the wastewater to wait for subsequent treatment;

[0038] S2. Electrochemical treatment: pre-degrade the pre-treated production wastewater and improve the biodegradability of the wastewater. The electrochemical process has a high removal rate for organic pollutants, and the COD removal rate can reach 30-90%. It can non-selectively degrade the refractory toxic organic matter in the wastewater into carbon dioxide, water and minerals, and convert the non-biodegradable high-molecular organic matter into small-molecule compounds that can be biochemically treated, thereby improving the biodegradability of the wastewater.

[0039] S3, biochemical treatment, the production wastewater after electrochemical treatment is first subjected to anaerobic biochemical treatment, then anoxic aerobic process treatment, and finally completed after MBR membrane filtration. MBR replaces the sedimentation tank to intercept sludge and SS to complete the wastewater treatment to meet the standards.

[0040] It also includes disinfection treatment, which sterilizes and disinfects the biochemically treated water and has a partial removal effect on residual COD and ammonia nitrogen. The disinfection treatment is to add sodium hypochlorite to the wastewater.

[0041] The present invention adopts a combination of electrochemical process, UASB anaerobic process, AO biochemical process and MBR membrane filtration process to treat high COD N-methylpyrrolidone wastewater, and the treatment effect is remarkable. It can meet the requirements of Class II standard of pollutant emission standard for electronic industry (indirect emission standard) (GB 39731-2020) after wastewater treatment, and the effluent water quality is stable.

[0042] Embodiment 4 of the present invention: A method for treating N-methylpyrrolidone wastewater, comprising the following steps:

[0043] S1, pretreatment, collecting and storing production wastewater, homogenizing and averaging the water quality, and then adding flocculants and coagulants to the collected and stored production wastewater, wherein the flocculants and coagulants are PAC and PAM respectively, and adjusting the pH to 6-6.5 by adding alkali to the production wastewater, and pressurizing and lifting the wastewater to wait for subsequent treatment;

[0044] S2. Electrochemical treatment: Use CME electrochemical system to electrochemically oxidize wastewater, pre-degrade pre-treated production wastewater, and improve the biodegradability of wastewater. The electrochemical process has a high removal rate for organic pollutants, and the COD removal rate can reach 30-90%. It can non-selectively degrade the toxic organic matter that is difficult to degrade in wastewater into carbon dioxide, water and minerals, and convert non-biodegradable high-molecular organic matter into small-molecule compounds that can be biochemically treated, thereby improving the biodegradability of wastewater.

[0045] S3, biochemical treatment, the production wastewater after electrochemical treatment is first subjected to anaerobic biochemical treatment, then to anoxic aerobic process treatment, and finally to MBR membrane filtration. MBR replaces the sedimentation tank to intercept sludge and SS to complete the wastewater treatment to meet the standards. The biochemical treatment includes anaerobic treatment, A / O treatment and MBR membrane filtration treatment. The anaerobic treatment adopts an upflow anaerobic sludge bed process for anaerobic biochemical treatment, and the macromolecular organic matter is broken and decomposed to produce small molecular organic acids, some of which are incompletely oxidized to organic matter such as methane, so as to improve the biodegradability of the wastewater. In the A / O treatment process, the anoxic aerobic process section removes most of the COD in the water and decomposes it into water and CO2, and the ammonia nitrogen and organic nitrogen are nitrified and denitrified to generate nitrogen gas to remove the system, and the degradation of total nitrogen is completed. At the same time, urea and sodium dihydrogen phosphate are added to the wastewater.

[0046] It also includes disinfection treatment, which sterilizes and disinfects the biochemically treated water and has a partial removal effect on residual COD and ammonia nitrogen. The disinfection treatment is to add sodium hypochlorite to the wastewater.

[0047] It also includes sludge treatment. Part of the sludge produced by MBR membrane filtration is returned to the A / O treatment process for utilization, and the other part is concentrated and filtered by a plate and frame dehydrator.

[0048] The present invention adopts a combination of electrochemical process, UASB anaerobic process, AO biochemical process and MBR membrane filtration process to treat high COD N-methylpyrrolidone wastewater, and the treatment effect is remarkable. It can meet the requirements of Class II standard of pollutant emission standard for electronic industry (indirect emission standard) (GB 39731-2020) after wastewater treatment, and the effluent water quality is stable.

[0049] Embodiment 5 of the present invention: An N-methylpyrrolidone wastewater treatment system comprises a regulating tank 1, wherein the outlet end of the regulating tank 1 is connected to the inlet end of an electrochemical reaction tank 2, the outlet end of the electrochemical reaction tank 2 is connected to the inlet end of a biochemical regulating tank 3, the outlet end of the biochemical regulating tank 3 is connected to the inlet end of a UASB anaerobic tank 4, the outlet end of the UASB anaerobic tank 4 is connected to the inlet end of an anoxic tank 5, the outlet end of the anoxic tank 5 is connected to the inlet end of an aerobic tank 6, the outlet end of the aerobic tank 6 is connected to the inlet end of an MBR tank 7, the sludge output end of the MBR tank 7 is connected to the UASB anaerobic tank 4, the outlet end of the MBR equipment in the MBR tank 7 is connected to a disinfection tank 8, the outlet end of the disinfection tank 8 is connected to a clear water tank 9, and the sludge output end of the MBR tank 7 is connected to a sludge treatment device 10.

[0050] Embodiment 6 of the present invention: An N-methylpyrrolidone wastewater treatment system comprises a regulating tank 1, wherein the outlet end of the regulating tank 1 is connected to the inlet end of an electrochemical reaction tank 2, the outlet end of the electrochemical reaction tank 2 is connected to the inlet end of a biochemical regulating tank 3, the outlet end of the biochemical regulating tank 3 is connected to the inlet end of a UASB anaerobic tank 4, the outlet end of the UASB anaerobic tank 4 is connected to the inlet end of an anoxic tank 5, the outlet end of the anoxic tank 5 is connected to the inlet end of an aerobic tank 6, the outlet end of the aerobic tank 6 is connected to the inlet end of an MBR tank 7, the sludge output end of the MBR tank 7 is connected to the UASB anaerobic tank 4, the outlet end of the MBR equipment in the MBR tank 7 is connected to a disinfection tank 8, the outlet end of the disinfection tank 8 is connected to a clear water tank 9, and the sludge output end of the MBR tank 7 is connected to a sludge treatment device 10.

[0051] The aeration system 11 is also included. The aeration system 11 is connected to the aerobic tank 6 and the MBR tank 7 respectively. The aeration system 11 includes a blower 12, an aeration pipe 13, and an aeration head 14. The output end of the blower 12 is connected to the aeration pipe 13 through a pipeline. There are at least two aeration pipes 13. The aeration pipe 13 is arranged at the bottom of the aerobic tank 6 and the MBR tank 7. The aeration heads 14 are evenly distributed on the aeration pipe 13. The aeration pipe 13 includes a main pipe 15 and a branch pipe 3. The branch pipes 3 are evenly distributed on both sides of the main pipe 15. The main pipe 15 and the branch pipe 3 are connected to each other. The angle is 15°-35°, and the cross-sectional area of ​​the inner cavity of the main pipe 15 is larger than the sum of the cross-sectional areas of the inner cavities of the branches 3. The aeration heads 14 are evenly distributed on the upper sides of the branches 3. The different resistance losses of the branches in the multi-branch parallel pipeline are the direct cause of the uneven flow distribution of the branches. The inclined branch part can reduce the resistance loss of the branch 3. The consistent angle can make the resistance of the branches 3 of each branch part the same. When the total resistance loss of each branch 3 in the parallel pipeline is small, the ratio of the cross-sectional area of ​​the main pipe 15 to the sum of the cross-sectional areas of each branch 3 is greater than 1 by design, and the flow distribution uniformity of each branch 3 is better. A check valve is provided on the connecting pipe between the blower 12 and the aeration pipe 13. .

[0052] The working principle of an embodiment of the present invention: The treatment method of the present invention combines electrochemical process, UASB anaerobic process, AO biochemical process and MBR membrane filtration process to treat high COD N-methylpyrrolidone wastewater, and the treatment effect is significant. It can meet the requirements of Class II standard of pollutant emission standards for the electronics industry (indirect emission standard) (GB 39731-2020) after wastewater treatment, and the effluent water quality is stable. In actual use, the COD of sewage in the regulating tank 1 is 19900 mg / L, and TN is 149 mg / L. After treatment, the effluent water quality COD is 400 mg / L, and TN is 6.30 mg / L. The treatment effect is obvious and the effluent water quality is stable.

[0053] During use of the treatment system of the present invention, wastewater is collected and stored in the regulating tank 1. The regulating tank 1 is provided with a water inlet fine grid to intercept debris, and the water quality is homogenized and evenly treated. At the same time, the pH of the wastewater is adjusted to 6-6.5 by adding alkali, and PAC and PAM can be added to the regulating tank 1. The wastewater is then pressurized and lifted to enter the electrochemical reaction tank 2, where the wastewater is pre-degraded to remove part of the COD and improve the biodegradability of the wastewater. The wastewater then enters the UASB anaerobic tank 4, which is mainly used for anaerobic biochemical treatment, to break the chain of large molecular organic matter, produce small molecular organic acids, and partially be incompletely oxidized to organic matter such as methane, thereby improving the biodegradability of the wastewater. The wastewater from the electrochemical reaction tank 2 is then treated through the A / O process, and enters the UASB anaerobic tank 4 with a residence time of 15 hours, and then enters the aerobic tank 6 with a residence time of 15 hours. The anoxic and aerobic process section removes water. Most of the COD in the water is decomposed into water and CO2, and ammonia nitrogen and organic nitrogen are nitrified and denitrified to generate nitrogen gas to remove the system, completing the degradation of total nitrogen; then it enters the MBR pool 7 for filtration, and the MBR device replaces the sedimentation tank to intercept the sludge and SS. The sludge output end of the MBR pool 7 is connected to the UASB anaerobic pool 4 for sludge return, and the water treated by the MBR flows into the disinfection pool 8, which disinfects and sterilizes the biochemically treated water, and also has a partial removal effect on the residual COD and ammonia nitrogen. The disinfected clean water is collected in the clean water pool 9, and the disinfected wastewater stored in the clean water pool 9 is lifted to the discharge point of the plant for discharge; the sludge output end of the MBR pool 7 is connected to the sludge treatment device 10, which uses a plate and frame filter press to further treat the sludge after sedimentation in the sludge pool to reduce the sludge water content to 80% and reduce the sludge volume.

Claims

1. A method for treating N-methylpyrrolidone wastewater, characterized in that: The following steps are involved: S1, pre-treatment, collecting and storing production wastewater, homogenizing and balancing the water quality, pressurizing and lifting the wastewater, and waiting for subsequent treatment; S2. Electrochemical treatment, which pre-degrades the pre-treated production wastewater and improves the biodegradability of the wastewater; S3, biochemical treatment, the production wastewater after electrochemical treatment is first subjected to anaerobic biochemical treatment, then anoxic aerobic process treatment, and finally completed after MBR membrane filtration.

2. A method for treating N-methylpyrrolidone wastewater according to claim 1, characterized in that: It also includes disinfection treatment, which sterilizes and kills viruses in the biochemically treated water, and also has a partial removal effect on residual COD and ammonia nitrogen.

3. A method for treating N-methylpyrrolidone wastewater according to claim 2, characterized in that: The disinfection treatment is to add sodium hypochlorite into the wastewater.

4. A method for treating N-methylpyrrolidone wastewater according to claim 1, characterized in that: In step S1, after homogenizing and equalizing the water quality, flocculants and coagulants are added to the collected and stored production wastewater, and the pH is adjusted to 6-6.

5.

5. A method for treating N-methylpyrrolidone wastewater according to claim 4, characterized in that: The flocculant and coagulant are PAC and PAM respectively, and the pH is adjusted by adding alkali to the production wastewater.

6. A method for treating N-methylpyrrolidone wastewater according to claim 1, characterized in that: The electrochemical treatment in step S2 uses a CME electrochemical system to electrochemically oxidize the wastewater.

7. A method for treating N-methylpyrrolidone wastewater according to claim 1, characterized in that: The biochemical treatment in step S3 includes anaerobic treatment, A / O treatment and MBR membrane filtration treatment. The anaerobic treatment adopts an upflow anaerobic sludge blanket process for anaerobic biochemical treatment. In the A / O treatment process, urea and sodium dihydrogen phosphate are added to the wastewater at the same time.

8. A method for treating N-methylpyrrolidone wastewater according to claim 7, characterized in that: It also includes sludge treatment. Part of the sludge produced by MBR membrane filtration is returned to the A / O treatment process for utilization, and the other part is concentrated and filtered using a plate and frame dehydrator.

9. An N-methylpyrrolidone wastewater treatment system according to claims 1-7, characterized in that: The invention comprises a regulating tank (1), wherein the water outlet of the regulating tank (1) is connected to the water inlet of an electrochemical reaction tank (2), the water outlet of the electrochemical reaction tank (2) is connected to the water inlet of a UASB anaerobic tank (4), the water outlet of the UASB anaerobic tank (4) is connected to the water inlet of an anoxic tank (5), the water outlet of the anoxic tank (5) is connected to the water inlet of an aerobic tank (6), the water outlet of the aerobic tank (6) is connected to the water inlet of an MBR tank (7), the sludge output end of the MBR tank (7) is connected to the UASB anaerobic tank (4), the water outlet of an MBR device in the MBR tank (7) is connected to a disinfection tank (8), the water outlet of the disinfection tank (8) is connected to a clean water tank (9), and the sludge output end of the MBR tank (7) is connected to a sludge treatment device (10).

10. The N-methylpyrrolidone wastewater treatment system according to claim 9, characterized in that: The invention also comprises an aeration system (11), wherein the aeration system (11) is connected to the aerobic tank (6) and the MBR tank (7) respectively, and the aeration system (11) comprises a blower (12), an aeration pipe (13), and an aeration head (14). The output end of the blower (12) is connected to the aeration pipe (13) through a pipeline. There are at least two aeration pipes (13), and the aeration pipes (13) are arranged at the bottom of the aerobic tank (6) and the MBR tank (7). Aeration heads (14) are evenly distributed on the air pipe member (13); the aeration pipe member (13) comprises a main pipe (15) and a branch pipe (3); the branch pipes (3) are evenly distributed on both sides of the main pipe (15); the angle between the main pipe (15) and the branch pipe (3) is 15°-35°, and the inner cavity cross-sectional area of ​​the main pipe (15) is greater than the sum of the inner cavity cross-sectional areas of each of the branch pipes (3); and the aeration heads (14) are evenly distributed on the upper side of each of the branch pipes (3).

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