A method for treating high-concentration organic wastewater

Abstract

This invention discloses a method for treating high-concentration organic wastewater, comprising: (1) homogenizing and equalizing the wastewater, adjusting the pH to 3-4, and recovering polyvinylpyrrolidone; (2) concentrating the filtrate using an ultrafiltration membrane, and drying the concentrate to recover polyvinylpyrrolidone; (3) pumping the permeate into an adsorption column for dynamic adsorption until saturation, desorbing 1-vinyl-2-pyrrolidone, and recovering 1-vinyl-2-pyrrolidone; (4) adjusting the pH of the adsorbed wastewater to 2-6, adding ZIF-8@Fe3O4 core-shell catalyst and hydrogen peroxide to generate Fe(OH)3 flocs, and separating the supernatant and iron sludge; (5) treating the supernatant using an A2 / O-MBR combined process, passing it through a ceramic filter layer, disinfecting it with ultraviolet light, adjusting the pH to neutral, and testing the water quality to meet the discharge requirements before effluent discharge. This invention can achieve nitrogen and phosphorus removal, suspended solids retention and salt-tolerant bacteria enhancement in wastewater, ensuring effluent stability; the multi-level barrier of ozone oxidation combined with photocatalysis and ultraviolet disinfection ensures that the effluent meets discharge standards.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a method for treating high-concentration organic wastewater. Background Technology

[0002] Polyvinylpyrrolidone is a nonionic polymer compound and the most distinctive, extensively studied, and fine chemical among N-vinylamide polymers. It has gained wide application due to its excellent and unique properties.

[0003] With the rapid development of industries such as pharmaceuticals and chemicals, the production of polyvinylpyrrolidone (PVP) has gradually increased. The production of PPVP generates a large amount of industrial wastewater containing raw material N-vinylpyrrolidone and products such as PPVP and polyvinylpyrrolidone. This type of wastewater is characterized by complex composition, high COD concentration (typically >2000 mg / L), high salinity (some wastewater contains 1-3% salt), and strong biological toxicity. Traditional treatment processes are insufficient for efficient degradation and resource recovery, necessitating the development of integrated and green wastewater treatment technologies. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method and system for treating high-concentration organic wastewater.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for treating high-concentration organic wastewater includes the following steps:

[0007] (1) The wastewater to be treated is introduced into the equalization tank after being screened to remove slag. The wastewater is stirred to make it homogeneous and uniform in quantity. A pH adjuster is added to adjust the pH to 3-4. The wastewater is allowed to stand to precipitate polyvinylpyrrolidone. The precipitate is separated and polyvinylpyrrolidone is recovered using a plate and frame filter press.

[0008] (2) The filtrate produced by pressure filtration is concentrated by ultrafiltration membrane to produce concentrate and permeate. Polyvinylpyrrolidone is recovered after the concentrate is dried.

[0009] (3) The liquid is pumped into the adsorption column filled with adsorbent and dynamically adsorbed until saturation, generating wastewater from the adsorption treatment. The 1-vinyl-2-pyrrolidone on the adsorbent is desorbed by the desorption liquid and the 1-vinyl-2-pyrrolidone is recovered by distillation.

[0010] (4) The pH of the adsorption-treated wastewater is adjusted to 2-6 by pH adjuster, ZIF-8@Fe3O4 core-shell catalyst and hydrogen peroxide are added, the reaction is stirred, and then alkali is added to adjust the pH to 8-9 to generate Fe(OH)3 flocs. After settling, the supernatant and iron sludge are separated.

[0011] (5) Add KH2PO4 and trace elements to the separated supernatant, adjust the C:N:P ratio to 100:5:1, pump it into the anaerobic tank and stir. The hydraulic retention time is 2-4 hours. Then pump it into the anoxic tank and the hydraulic retention time is 4-6 hours. Add sodium acetate to adjust the C:N ratio to 4-6. The mixed liquor reflux ratio is 100-200%. After denitrification, pump it into the aerobic tank. Under the conditions of dissolved oxygen 2-4 mg / L and sludge concentration 8000-12000 mg / L, the hydraulic retention time is 8-12 hours. Nitrifying bacteria convert ammonia nitrogen into NO3. - The resulting wastewater undergoes nitrogen and phosphorus removal;

[0012] (6) Pump the denitrification and phosphorus removal wastewater into the MBR membrane tank equipped with hollow fiber membrane, with a pumping cycle of 8-12 min operation / 2 min relaxation. The suspended solids in the effluent are <10 mg / L. Then add 5-10% sludge concentration of salt-tolerant nitrifying bacteria, ozone and titanium dioxide catalyst to react and obtain mixed wastewater.

[0013] (7) Pump the mixed wastewater into the aerated biological filter. The mixed wastewater passes through the ceramsite filter layer at a filtration rate of 0.5-1.5 m / h. The hydraulic retention time is 1-2 h. Then, methanol is added to supplement trace carbon sources. Ultraviolet light is used for disinfection. The pH is adjusted to neutral and the water quality is tested. After meeting the discharge requirements, the effluent is discharged.

[0014] Furthermore, in step (1), the stirring speed is 50-100 rpm, the standing time is 1-2 h, the pressure of the plate and frame filter press is ≥0.5 MPa, and the recovery rate of polyvinylpyrrolidone is ≥90%.

[0015] Furthermore, in step (2), the ultrafiltration membrane has a molecular weight cutoff of 5-50 kDa, a membrane flux of 10-30 L / (m²·h), a drying temperature of 60-80℃, and a polyvinylpyrrolidone recovery rate of ≥85%.

[0016] Further, in step (3), the adsorbent in the adsorption column includes at least one of activated carbon, mesoporous silica, diatomaceous earth, and porous alumina ceramic. The adsorbent dosage is 5-20 g / L, the adsorption time is 1-3 h, the desorption solution is a mixed solution of methanol, sodium hydroxide and water, the mass ratio of methanol, sodium hydroxide and water is 4:1:10-20, and the recovery rate of 1-vinyl-2-pyrrolidone is ≥80%.

[0017] Further, in step (4), the amount of ZIF-8@Fe3O4 core-shell catalyst added is 0.5-1.5 g / L, the amount of hydrogen peroxide added is 0.1-0.3 mol / L, the stirring speed is 200-400 rpm, the stirring time is 1-2 h, the alkali includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water, and the settling time is 0.5-1 h.

[0018] Furthermore, the preparation method of the ZIF-8@Fe3O4 core-shell catalyst in step (4) includes the following steps:

[0019] S1. Weigh out the following components by weight: 5-6 parts ferric chloride hexahydrate, 2-3 parts ferrous chloride tetrahydrate, 0.5-1 parts sodium citrate, 2-4 parts 3-aminopropyltriethoxysilane, 0.1-0.3 parts succinic anhydride, 0.6-1.0 parts zinc nitrate hexahydrate, 1.2-1.6 parts 2-methylimidazole, 40-60 parts ethanol, 80-120 parts methanol, and 100-120 parts deionized water.

[0020] S2. Dissolve ferric chloride hexahydrate and ferrous chloride tetrahydrate in deionized water, add sodium citrate, bubble with nitrogen for 30-40 minutes to remove oxygen, add 20-30% ammonia water dropwise at 60-70℃ under nitrogen protection to adjust the pH to 10-11, stir vigorously at 800-1000 rpm for 1-2 hours to form a black precipitate, after magnetic separation, wash the black precipitate with ethanol and deionized water alternately 3-5 times, and vacuum dry at 50-60℃ for 4-6 hours to obtain Fe3O4 nanoparticles with a particle size of 50-100nm.

[0021] S3. Disperse Fe3O4 nanoparticles in ethanol, add 3-aminopropyltriethoxysilane, sonicate for 30-40 min, reflux at 50-60℃ for 4-6 h, and after magnetic separation, wash and dry to obtain amino-modified iron(III) oxide.

[0022] S4. Add amino-modified iron(III) oxide and succinic anhydride to 1 / 2 methanol and stir for 1-2 hours. Then sonicate for 20-30 minutes to obtain a suspension.

[0023] S5. Dissolve zinc nitrate hexahydrate and 2-methylimidazole separately in 1 / 4 methanol and sonicate to dissolve. Mix the zinc nitrate solution with the suspension and slowly add the 2-methylimidazole solution under magnetic stirring. Transfer to a hydrothermal reactor and react at 116-124℃ for 6-8 hours. Filter and wash the filter residue with methanol and deionized water 3-5 times in sequence. Dry under vacuum at 60-70℃ for 10-12 hours to obtain the ZIF-8@Fe3O4 core-shell catalyst.

[0024] Furthermore, in step (5), the amount of KH2PO4 added is 10-50 mg / L phosphate concentration, the trace elements include at least one of iron, magnesium, potassium and zinc, and the stirring speed is 30-60 rpm.

[0025] Further, in step (6), the hollow fiber membrane has a pore size of 0.1-0.4 μm, the dosage of the salt-tolerant nitrifying bacteria is 5-10% of the sludge concentration, the dosage of ozone is 10-30 mg / L, the dosage of titanium dioxide catalyst is 1-3 g / L, and the reaction time is 30-60 min.

[0026] Furthermore, in step (7), the amount of methanol added is 10-20 mg / L, and the dose of ultraviolet light is 30-60 mJ / cm².

[0027] Furthermore, the pH adjuster includes at least one of sulfuric acid, hydrochloric acid, and glacial acetic acid.

[0028] In summary, this application includes at least one of the following beneficial technical effects:

[0029] This invention achieves high recovery rates of polyvinylpyrrolidone and 1-vinyl-2-pyrrolidone through ultrafiltration, adsorption, and distillation purification, reducing raw material costs; the ZIF-8@Fe3O4 core-shell catalyst combines convenient magnetic separation with high catalytic activity, and can efficiently degrade recalcitrant organic compounds when combined with H2O2. 2 The combination of the / O process and the MBR membrane bioreactor achieves nitrogen and phosphorus removal, suspended solids retention, and salt-tolerant bacteria enhancement, ensuring effluent stability; the multi-level barrier of ozone oxidation combined with photocatalysis and ultraviolet disinfection ensures that the effluent meets discharge standards. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. Unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0031] This invention provides a method for treating high-concentration organic wastewater, comprising the following steps:

[0032] (1) Weigh out the following components by weight: 5-6 parts of ferric chloride hexahydrate, 2-3 parts of ferrous chloride tetrahydrate, 0.5-1 parts of sodium citrate, 2-4 parts of 3-aminopropyltriethoxysilane, 0.1-0.3 parts of succinic anhydride, 0.6-1.0 parts of zinc nitrate hexahydrate, 1.2-1.6 parts of 2-methylimidazole, 40-60 parts of ethanol, 80-120 parts of methanol, and 100-120 parts of deionized water.

[0033] (2) Dissolve ferric chloride hexahydrate and ferrous chloride tetrahydrate in deionized water, add sodium citrate, bubble with nitrogen for 30-40 min to remove oxygen, add 20-30% ammonia water dropwise at 60-70℃ under nitrogen protection to adjust pH to 10-11, stir vigorously at 800-1000 rpm for 1-2 h to generate black precipitate, after magnetic separation, wash the black precipitate with ethanol and deionized water alternately 3-5 times, and vacuum dry at 50-60℃ for 4-6 h to obtain Fe3O4 nanoparticles with a particle size of 50-100 nm;

[0034] (3) Disperse Fe3O4 nanoparticles in ethanol, add 3-aminopropyltriethoxysilane, sonicate for 30-40 min, reflux at 50-60℃ for 4-6 h, and after magnetic separation, wash and dry to obtain amino-modified iron(III) oxide;

[0035] (4) Add amino-modified iron oxide and succinic anhydride to 1 / 2 methanol and stir for 1-2 hours. Then sonicate for 20-30 minutes to obtain a suspension.

[0036] (5) Dissolve zinc nitrate hexahydrate and 2-methylimidazole in 1 / 4 of methanol, and sonicate to dissolve. Mix the zinc nitrate solution with the suspension, and slowly add the 2-methylimidazole solution under magnetic stirring. Transfer to a hydrothermal reactor and react at 116-124℃ for 6-8h. Filter and wash the filter residue with methanol and deionized water 3-5 times in sequence. Dry under vacuum at 60-70℃ for 10-12h to obtain ZIF-8@Fe3O4 core-shell catalyst.

[0037] (6) After the wastewater to be treated is removed by the screen, it is introduced into the equalization tank and stirred at a speed of 50-100 rpm to make the wastewater homogeneous and uniform. The pH is adjusted to 3-4 by adding pH adjuster dropwise and allowed to stand for 1-2 hours to allow polyvinylpyrrolidone to precipitate. The precipitate is separated and polyvinylpyrrolidone is recovered by plate and frame filter press under a pressure ≥0.5MPa. The recovery rate of polyvinylpyrrolidone is ≥90%.

[0038] (7) The filtrate produced by pressure filtration is concentrated by ultrafiltration membrane with a molecular weight cutoff of 5-50 kDa and a membrane flux of 10-30 L / (m²·h) to produce concentrate and permeate. The concentrate is dried at a temperature of 60-80℃ to recover polyvinylpyrrolidone, and the polyvinylpyrrolidone recovery rate is ≥85%.

[0039] (8) The permeate is pumped into an adsorption column filled with adsorbent, wherein the amount of adsorbent added is 5-20 g / L, the adsorption time is 1-3 h, and the adsorption is dynamically saturated, generating wastewater from the adsorption treatment. The 1-vinyl-2-pyrrolidone on the adsorbent is desorbed using desorption liquid, and the 1-vinyl-2-pyrrolidone is recovered by distillation and purification. The recovery rate of 1-vinyl-2-pyrrolidone is ≥80%.

[0040] (9) The pH of the adsorption-treated wastewater is adjusted to 2-6 by pH adjuster, 0.5-1.5 g / L of ZIF-8@Fe3O4 core-shell catalyst and 0.1-0.3 mol / L of hydrogen peroxide are added, and the mixture is stirred at 200-400 rpm for 1-2 h. Then, alkali is added to adjust the pH to 8-9 to generate Fe(OH)3 flocs. The mixture is allowed to stand for 0.5-1 h to settle, and the supernatant and iron sludge are separated.

[0041] (10) Add KH2PO4 to the separated supernatant at a phosphate concentration of 10-50 mg / L, and add trace elements to adjust the C:N:P ratio to 100:5:1. Then pump it into the anaerobic tank and stir at 30-60 rpm for 2-4 h. Then pump it into the anoxic tank for 4-6 h and add sodium acetate to adjust the C:N ratio to 4-6. The mixed liquor reflux ratio is 100-200%. After denitrification, pump it into the aerobic tank. Under the conditions of dissolved oxygen 2-4 mg / L and sludge concentration 8000-12000 mg / L, the hydraulic retention time is 8-12 h. Nitrifying bacteria convert ammonia nitrogen into NO. 3- The resulting wastewater undergoes nitrogen and phosphorus removal;

[0042] (11) Pump the denitrification and phosphorus removal wastewater into an MBR membrane tank equipped with a hollow fiber membrane with a pore size of 0.1-0.4μm. The pumping cycle is 8-12min operation / 2min relaxation. The suspended solids in the effluent are <10mg / L. Then add 5-10% sludge concentration of salt-tolerant nitrifying bacteria, 10-30mg / L of ozone and 1-3g / L of titanium dioxide catalyst. React for 30-60min to obtain mixed wastewater.

[0043] (12) Pump the mixed wastewater into the aerated biological filter. The mixed wastewater passes through the ceramsite filter layer at a filtration rate of 0.5-1.5 m / h and a hydraulic retention time of 1-2 h. Then add 10-20 mg / L of methanol to supplement trace carbon sources. Disinfect with ultraviolet light at a dose of 30-60 mJ / cm². Adjust the pH to neutral and test the water quality. After meeting the discharge requirements, the effluent is discharged.

[0044] The pH adjuster includes at least one of sulfuric acid, hydrochloric acid, and glacial acetic acid; the adsorbent includes at least one of activated carbon, mesoporous silica, diatomaceous earth, and porous alumina ceramic; the desorption solution is a mixed solution of methanol, sodium hydroxide, and water, wherein the mass ratio of methanol, sodium hydroxide, and water is 4:1:10-20; the alkali includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water; and the trace elements include at least one of iron, magnesium, potassium, and zinc.

[0045] The chemical sludge generated from the wastewater treatment is dehydrated after magnetic recovery of the ZIF-8@Fe3O4 core-shell catalyst and then incinerated at a temperature of 800-1000℃ to prepare building materials; the biological sludge has a hydraulic retention time of 15-30 days, is anaerobically digested to produce biogas, and the biogas residue is composted.

[0046] Example 1

[0047] The method for treating high-concentration organic wastewater in this embodiment includes the following steps:

[0048] (1) Weigh out the following components by weight: 5 parts ferric chloride hexahydrate, 2 parts ferrous chloride tetrahydrate, 0.5 parts sodium citrate, 2 parts 3-aminopropyltriethoxysilane, 0.1 parts succinic anhydride, 0.6 parts zinc nitrate hexahydrate, 1.2 parts 2-methylimidazole, 40 parts ethanol, 80 parts methanol, and 100 parts deionized water.

[0049] (2) Dissolve ferric chloride hexahydrate and ferrous chloride tetrahydrate in deionized water, add sodium citrate, bubble with nitrogen for 30 min to remove oxygen, add 20% ammonia water dropwise at 60℃ under nitrogen protection to adjust pH to 10, stir vigorously at 800 rpm for 1 h to generate black precipitate, after magnetic separation, wash the black precipitate with ethanol and deionized water alternately 3-5 times, and vacuum dry at 50℃ for 4 h to obtain Fe3O4 nanoparticles with a particle size of 50 nm.

[0050] (3) Disperse Fe3O4 nanoparticles in ethanol, add 3-aminopropyltriethoxysilane, sonicate for 30 min, reflux at 50 °C for 4 h, and after magnetic separation, wash and dry to obtain amino-modified iron(III) oxide.

[0051] (4) Add amino-modified iron oxide and succinic anhydride to 1 / 2 methanol and stir for 1-2 hours, then sonicate for 20 minutes to obtain a suspension;

[0052] (5) Dissolve zinc nitrate hexahydrate and 2-methylimidazole in 1 / 4 of methanol, and sonicate to dissolve. Mix the zinc nitrate solution with the suspension, and slowly add the 2-methylimidazole solution under magnetic stirring. Transfer to a hydrothermal reactor and react at 116℃ for 6 hours. Filter and wash the filter residue with methanol and deionized water three times in sequence. Dry under vacuum at 60℃ for 10 hours to obtain ZIF-8@Fe3O4 core-shell catalyst.

[0053] (6) The wastewater to be treated was introduced into the equalization tank after being screened to remove slag. The wastewater was stirred at 50 rpm to make it homogeneous and uniform in quantity. Sulfuric acid was added dropwise to adjust the pH to 3. The mixture was allowed to stand for 1 hour to precipitate polyvinylpyrrolidone. The precipitate was separated and polyvinylpyrrolidone was recovered using a plate and frame filter press under a pressure of 0.5 MPa. The recovery rate of polyvinylpyrrolidone was 93.7%.

[0054] (7) The filtrate produced by pressure filtration is concentrated using an ultrafiltration membrane with a molecular weight cutoff of 5 kDa and a membrane flux of 10 L / (m²·h) to produce a concentrate and a permeate. The concentrate is dried at 60°C to recover polyvinylpyrrolidone, and the polyvinylpyrrolidone recovery rate is 87.6%.

[0055] (8) The permeate is pumped into an adsorption column filled with activated carbon, wherein the amount of activated carbon added is 5 g / L, the adsorption time is 1 h, and the adsorption is dynamically adsorbed until saturation, generating wastewater from the adsorption treatment. 1-vinyl-2-pyrrolidone on the adsorbent is desorbed using a desorption solution, wherein the desorption solution is a mixed solution of methanol, sodium hydroxide and water, and the mass ratio of methanol, sodium hydroxide and water is 4:1:10. 1-vinyl-2-pyrrolidone is recovered by distillation and purification, and the recovery rate of 1-vinyl-2-pyrrolidone is 83.4%.

[0056] (9) The pH of the adsorption-treated wastewater was adjusted to 2 with sulfuric acid, and 0.5 g / L of ZIF-8@Fe3O4 core-shell catalyst and 0.1 mol / L of hydrogen peroxide were added. The mixture was stirred at 200 rpm for 1 h, and then sodium hydroxide was added to adjust the pH to 8 to generate Fe(OH)3 flocs. The mixture was allowed to stand for 0.5 h to settle, and the supernatant and iron sludge were separated.

[0057] (10) Add KH2PO4 to the separated supernatant at a phosphate concentration of 10 mg / L, and add trace element iron. Adjust the C:N:P ratio to 100:5:1 and pump it into the anaerobic tank. Stir at 30 rpm for 2 hours. Then pump it into the anoxic tank for 4 hours. Add sodium acetate to adjust the C:N ratio to 4. The mixed liquor reflux ratio is 100%. After denitrification, pump it into the aerobic tank. Under the conditions of dissolved oxygen 2 mg / L and sludge concentration 8000 mg / L, the hydraulic retention time is 8 hours. Nitrifying bacteria convert ammonia nitrogen into NO. 3- The resulting wastewater undergoes nitrogen and phosphorus removal;

[0058] (11) The denitrification and phosphorus removal wastewater is pumped into an MBR membrane tank equipped with a hollow fiber membrane with a pore size of 0.1 μm. The pumping cycle is 8 min operation / 2 min relaxation. The suspended solids in the effluent are <10 mg / L. Then, 5% sludge concentration of salt-tolerant nitrifying bacteria, 10 mg / L ozone and 1 g / L titanium dioxide catalyst are added. The reaction is carried out for 30 min to obtain mixed wastewater.

[0059] (12) Pump the mixed wastewater into the aerated biological filter. The mixed wastewater passes through the ceramic filter layer at a filtration rate of 0.5 m / h and a hydraulic retention time of 1 h. Then add 10 mg / L of methanol to supplement trace carbon sources. Disinfect with ultraviolet light at a dose of 30 mJ / cm². Adjust the pH to neutral and test the water quality. After meeting the discharge requirements, the effluent is discharged.

[0060] Example 2

[0061] The method for treating high-concentration organic wastewater in this embodiment includes the following steps:

[0062] (1) Weigh out the following components by weight: 5.5 parts of ferric chloride hexahydrate, 2.5 parts of ferrous chloride tetrahydrate, 0.8 parts of sodium citrate, 3 parts of 3-aminopropyltriethoxysilane, 0.2 parts of succinic anhydride, 0.8 parts of zinc nitrate hexahydrate, 1.4 parts of 2-methylimidazole, 50 parts of ethanol, 100 parts of methanol, and 110 parts of deionized water.

[0063] (2) Dissolve ferric chloride hexahydrate and ferrous chloride tetrahydrate in deionized water, add sodium citrate, bubble with nitrogen for 35 min to remove oxygen, add 25% ammonia water dropwise at 65℃ under nitrogen protection to adjust pH to 10.5, stir vigorously at 900 rpm for 1.5 h to generate black precipitate, after magnetic separation, wash the black precipitate with ethanol and deionized water alternately 4 times, and vacuum dry at 55℃ for 5 h to obtain Fe3O4 nanoparticles with a particle size of 75 nm.

[0064] (3) Disperse Fe3O4 nanoparticles in ethanol, add 3-aminopropyltriethoxysilane, sonicate for 35 min; reflux at 55 °C for 5 h, magnetically separate, wash and dry to obtain amino-modified iron(III) oxide;

[0065] (4) Add amino-modified iron oxide and succinic anhydride to 1 / 2 methanol and stir for 1.5 h, then sonicate for 25 min to obtain a suspension;

[0066] (5) Dissolve zinc nitrate hexahydrate and 2-methylimidazole in 1 / 4 of methanol, and sonicate to dissolve. Mix the zinc nitrate solution with the suspension, and slowly add the 2-methylimidazole solution under magnetic stirring. Transfer to a hydrothermal reactor and react at 120°C for 7 h. Filter and wash the filter residue with methanol and deionized water 4 times in sequence. Dry under vacuum at 65°C for 11 h to obtain ZIF-8@Fe3O4 core-shell catalyst.

[0067] (6) The wastewater to be treated was introduced into the equalization tank after being screened to remove slag. The wastewater was stirred at 75 rpm to make it homogeneous and uniform in quantity. Hydrochloric acid was added dropwise to adjust the pH to 3.5. The mixture was allowed to stand for 1.5 h to precipitate polyvinylpyrrolidone. The precipitate was separated and polyvinylpyrrolidone was recovered using a plate and frame filter press under a pressure of 1.0 MPa. The recovery rate of polyvinylpyrrolidone was 94.2%.

[0068] (7) The filtrate produced by pressure filtration is concentrated using an ultrafiltration membrane with a molecular weight cutoff of 25 kDa and a membrane flux of 20 L / (m²·h) to produce a concentrate and a permeate. The concentrate is dried at 70°C to recover polyvinylpyrrolidone, with a polyvinylpyrrolidone recovery rate of 89.4%.

[0069] (8) The permeate is pumped into an adsorption column filled with mesoporous silica, wherein the amount of mesoporous silica added is 10 g / L, the adsorption time is 2 h, and the adsorption is dynamically saturated to generate wastewater from the adsorption treatment. 1-vinyl-2-pyrrolidone on the mesoporous silica is desorbed using a desorption solution, wherein the desorption solution is a mixed solution of methanol, sodium hydroxide and water, and the mass ratio of methanol, sodium hydroxide and water is 4:1:15. 1-vinyl-2-pyrrolidone is recovered by distillation and purification, and the recovery rate of 1-vinyl-2-pyrrolidone is ≥84.7%.

[0070] (9) The pH of the adsorption-treated wastewater was adjusted to 4 with hydrochloric acid, 1 g / L of ZIF-8@Fe3O4 core-shell catalyst and 0.2 mol / L of hydrogen peroxide were added, and the mixture was stirred at 300 rpm for 1.5 h. Then potassium hydroxide was added to adjust the pH to 8.5 to generate Fe(OH)3 flocs. The mixture was allowed to stand for 0.8 h to settle, and the supernatant and iron sludge were separated.

[0071] (10) Add KH2PO4 to the separated supernatant at a phosphate concentration of 30 mg / L, and add trace element magnesium. Adjust the C:N:P ratio to 100:5:1 and pump it into the anaerobic tank. Stir at 45 rpm for 3 hours. Then pump it into the anoxic tank for 5 hours. Add sodium acetate to adjust the C:N ratio to 5. The mixed liquor reflux ratio is 150%. After denitrification, pump it into the aerobic tank. Under the conditions of dissolved oxygen 3 mg / L and sludge concentration 10000 mg / L, the hydraulic retention time is 10 hours. Nitrifying bacteria convert ammonia nitrogen into NO. 3- The resulting wastewater undergoes nitrogen and phosphorus removal;

[0072] (11) The denitrification and phosphorus removal wastewater is pumped into an MBR membrane tank equipped with a hollow fiber membrane with a pore size of 0.25 μm. The pumping cycle is 10 min operation / 2 min relaxation. The suspended solids in the effluent are <10 mg / L. Then, 7% sludge concentration of salt-tolerant nitrifying bacteria, 20 mg / L ozone and 2 g / L titanium dioxide catalyst are added. The reaction is carried out for 40 min to obtain mixed wastewater.

[0073] (12) Pump the mixed wastewater into the aerated biological filter. The mixed wastewater passes through the ceramsite filter layer at a filtration rate of 1.0 m / h and a hydraulic retention time of 1.5 h. Then add 15 mg / L of methanol to supplement trace carbon sources. Disinfect with ultraviolet light at a dose of 40 mJ / cm². Adjust the pH to neutral and test the water quality. After meeting the discharge requirements, the effluent is discharged.

[0074] Example 3

[0075] The method for treating high-concentration organic wastewater in this embodiment includes the following steps:

[0076] (1) Weigh out the following components by weight: 6 parts ferric chloride hexahydrate, 3 parts ferrous chloride tetrahydrate, 1 part sodium citrate, 4 parts 3-aminopropyltriethoxysilane, 0.3 parts succinic anhydride, 1.0 parts zinc nitrate hexahydrate, 1.6 parts 2-methylimidazole, 60 parts ethanol, 120 parts methanol, and 120 parts deionized water.

[0077] (2) Dissolve ferric chloride hexahydrate and ferrous chloride tetrahydrate in deionized water, add sodium citrate, bubble with nitrogen for 40 min to remove oxygen, add 30% ammonia water dropwise at 70℃ under nitrogen protection to adjust pH to 11, stir vigorously at 1000 rpm for 2 h to generate black precipitate, after magnetic separation, wash the black precipitate with ethanol and deionized water alternately 5 times, and vacuum dry at 60℃ for 6 h to obtain Fe3O4 nanoparticles with a particle size of 100 nm.

[0078] (3) Disperse Fe3O4 nanoparticles in ethanol, add 3-aminopropyltriethoxysilane, sonicate for 40 min, reflux at 60 °C for 6 h, and after magnetic separation, wash and dry to obtain amino-modified iron(III) oxide.

[0079] (4) Add amino-modified iron oxide and succinic anhydride to 1 / 2 methanol and stir for 2 hours. Then sonicate for 30 minutes to obtain a suspension.

[0080] (5) Dissolve zinc nitrate hexahydrate and 2-methylimidazole in 1 / 4 of methanol, and sonicate to dissolve. Mix the zinc nitrate solution with the suspension, and slowly add the 2-methylimidazole solution under magnetic stirring. Transfer to a hydrothermal reactor and react at 124°C for 8 hours. Filter and wash the filter residue with methanol and deionized water 5 times in sequence. Dry under vacuum at 70°C for 12 hours to obtain ZIF-8@Fe3O4 core-shell catalyst.

[0081] (6) The wastewater to be treated was introduced into the equalization tank after being screened to remove slag. The wastewater was stirred at 100 rpm to make it homogeneous and uniform in quantity. Glacial acetic acid was added dropwise to adjust the pH to 4. The mixture was allowed to stand for 2 hours to precipitate polyvinylpyrrolidone. The precipitate was separated and polyvinylpyrrolidone was recovered using a plate and frame filter press under a pressure of 1.5 MPa. The recovery rate of polyvinylpyrrolidone was 92.7%.

[0082] (7) The filtrate produced by pressure filtration is concentrated using an ultrafiltration membrane with a molecular weight cutoff of 50 kDa and a membrane flux of 30 L / (m²·h) to produce a concentrate and a permeate. The concentrate is dried at 80°C to recover polyvinylpyrrolidone, with a polyvinylpyrrolidone recovery rate of 88.2%.

[0083] (8) The permeate is pumped into an adsorption column filled with porous alumina ceramic, wherein the amount of porous alumina ceramic added is 20 g / L, the adsorption time is 3 h, and the adsorption is dynamically saturated, generating wastewater from the adsorption treatment. 1-vinyl-2-pyrrolidone on the porous alumina ceramic is desorbed using a desorption solution, wherein the desorption solution is a mixed solution of methanol, sodium hydroxide and water, and the mass ratio of methanol, sodium hydroxide and water is 4:1:20. 1-vinyl-2-pyrrolidone is recovered by distillation and purification, and the recovery rate of 1-vinyl-2-pyrrolidone is 82.6%.

[0084] (9) The pH of the adsorption-treated wastewater was adjusted to 6 with glacial acetic acid, and 1.5 g / L of ZIF-8@Fe3O4 core-shell catalyst and 0.3 mol / L of hydrogen peroxide were added. The mixture was stirred at 400 rpm for 2 h, and then ammonia was added to adjust the pH to 9 to generate Fe(OH)3 flocs. The mixture was allowed to stand for 1 h to settle, and the supernatant and iron sludge were separated.

[0085] (10) Add KH2PO4 to the separated supernatant at a phosphate concentration of 50 mg / L, and add trace element zinc. Adjust the C:N:P ratio to 100:5:1 and pump it into the anaerobic tank. Stir at 60 rpm for 4 hours. Then pump it into the anoxic tank for 6 hours. Add sodium acetate to adjust the C:N ratio to 6. The mixed liquor reflux ratio is 200%. After denitrification, pump it into the aerobic tank. Under the conditions of dissolved oxygen 4 mg / L and sludge concentration 12000 mg / L, the hydraulic retention time is 12 hours. Nitrifying bacteria convert ammonia nitrogen into NO. 3- The resulting wastewater undergoes nitrogen and phosphorus removal;

[0086] (11) The denitrification and phosphorus removal wastewater is pumped into an MBR membrane tank equipped with a hollow fiber membrane with a pore size of 0.4 μm. The pumping cycle is 12 min operation / 2 min relaxation. The suspended solids in the effluent are <10 mg / L. Then, 10% sludge concentration of salt-tolerant nitrifying bacteria, 30 mg / L ozone and 3 g / L titanium dioxide catalyst are added. The reaction is carried out for 60 min to obtain mixed wastewater.

[0087] (12) Pump the mixed wastewater into the aerated biological filter. The mixed wastewater passes through the ceramic filter layer at a filtration rate of 1.5 m / h and a hydraulic retention time of 2 h. Then add 20 mg / L of methanol to supplement trace carbon sources. Disinfect with ultraviolet light at a dose of 60 mJ / cm². Adjust the pH to neutral and test the water quality. After meeting the discharge requirements, the effluent is discharged.

[0088] Experimental example:

[0089] Water samples treated using the methods described in Examples 1-3 were tested for various indicators. The test results were based on the "Indirect Discharge Standard for Water Pollutants in Chemical Industry" (DB41 / 1135-2016), as shown in Table 1.

[0090] Table 1: Water Quality of Effluent from Examples 1-3

[0091] .

[0092] The test results of the effluent samples from Examples 1-3 show that this invention achieves high recovery rates of polyvinylpyrrolidone and 1-vinyl-2-pyrrolidone through ultrafiltration, adsorption, and distillation purification, thereby reducing raw material costs. The ZIF-8@Fe3O4 core-shell catalyst combines convenient magnetic separation with high catalytic activity, and when combined with H2O2, it can efficiently degrade recalcitrant organic matter. 2 The combination of the O / O process and the MBR membrane bioreactor achieves nitrogen and phosphorus removal, suspended solids retention, and salt-tolerant bacteria enhancement, ensuring effluent stability. The multi-level barrier of ozone oxidation combined with photocatalysis and ultraviolet disinfection ensures that the effluent meets discharge standards. Therefore, the method for treating high-concentration organic wastewater provided by this invention has promising application prospects.

[0093] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for treating high-concentration organic wastewater, characterized in that, Includes the following steps: (1) The wastewater to be treated is introduced into the equalization tank after being screened to remove slag. The wastewater is stirred to make it homogeneous and uniform in quantity. A pH adjuster is added to adjust the pH to 3-4. The wastewater is allowed to stand to precipitate polyvinylpyrrolidone. The precipitate is separated and polyvinylpyrrolidone is recovered using a plate and frame filter press. (2) The filtrate produced by pressure filtration is concentrated by ultrafiltration membrane to produce concentrate and permeate. Polyvinylpyrrolidone is recovered after the concentrate is dried. (3) The liquid is pumped into the adsorption column filled with adsorbent and dynamically adsorbed until saturation, generating wastewater from the adsorption treatment. The 1-vinyl-2-pyrrolidone on the adsorbent is desorbed by the desorption liquid and the 1-vinyl-2-pyrrolidone is recovered by distillation. (4) The pH of the adsorption-treated wastewater is adjusted to 2-6 by pH adjuster, ZIF-8@Fe3O4 core-shell catalyst and hydrogen peroxide are added, the reaction is stirred, and then alkali is added to adjust the pH to 8-9 to generate Fe(OH)3 flocs. After settling, the supernatant and iron sludge are separated. (5) adding KH2PO4 and trace elements to the separated supernatant, adjusting C:N:P to 100:5:1, and then pumping into an anaerobic tank and stirring, with a hydraulic retention time of 2-4 h, and then pumping into an anoxic tank, with a hydraulic retention time of 4-6 h, adding sodium acetate to adjust C:N to 4-6, and a mixed liquid reflux ratio of 100-200%, and then pumping into an aerobic tank after denitrification, under the conditions of a dissolved oxygen of 2-4 mg / L and a sludge concentration of 8000-12000 mg / L, with a hydraulic retention time of 8-12 h, so that nitrifying bacteria convert ammonia nitrogen into NO3 - , and then obtaining denitrified and phosphorus-removed wastewater; (6) Pump the denitrification and phosphorus removal wastewater into the MBR membrane tank equipped with hollow fiber membrane, with a pumping cycle of 8-12 min operation / 2 min relaxation. The suspended solids in the effluent are <10 mg / L. Then add 5-10% sludge concentration of salt-tolerant nitrifying bacteria, ozone and titanium dioxide catalyst to react and obtain mixed wastewater. (7) Pump the mixed wastewater into the aerated biological filter. The mixed wastewater passes through the ceramsite filter layer at a filtration rate of 0.5-1.5 m / h. The hydraulic retention time is 1-2 h. Then, methanol is added to supplement trace carbon sources. Ultraviolet light is used for disinfection. The pH is adjusted to neutral and the water quality is tested. After meeting the discharge requirements, the effluent is discharged.

2. The method for treating high-concentration organic wastewater according to claim 1, characterized in that, In step (1), the stirring speed is 50-100 rpm, the standing time is 1-2 h, the pressure of the plate and frame filter press is ≥0.5 MPa, and the recovery rate of polyvinylpyrrolidone is ≥90%.

3. The method for treating high-concentration organic wastewater according to claim 1, characterized in that, In step (2), the ultrafiltration membrane has a molecular weight cutoff of 5-50 kDa, a membrane flux of 10-30 L / (m²·h), a drying temperature of 60-80℃, and a polyvinylpyrrolidone recovery rate of ≥85%.

4. The method for treating high-concentration organic wastewater according to claim 1, characterized in that, The adsorbent in the adsorption column in step (3) includes at least one of activated carbon, mesoporous silica, diatomaceous earth, and porous alumina ceramic. The adsorbent dosage is 5-20 g / L, the adsorption time is 1-3 h, the desorption solution is a mixed solution of methanol, sodium hydroxide and water, the mass ratio of methanol, sodium hydroxide and water is 4:1:10-20, and the recovery rate of 1-vinyl-2-pyrrolidone is ≥80%.

5. The method for treating high-concentration organic wastewater according to claim 1, characterized in that, In step (4), the dosage of ZIF-8@Fe3O4 core-shell catalyst is 0.5-1.5 g / L, the dosage of hydrogen peroxide is 0.1-0.3 mol / L, the stirring speed is 200-400 rpm, and the time is 1-2 h. The alkali includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water. The settling time is 0.5-1 h.

6. The method for treating high-concentration organic wastewater according to claim 1, characterized in that, The preparation method of the ZIF-8@Fe3O4 core-shell catalyst in step (4) includes the following steps: S1. Weigh out the following components by weight: 5-6 parts ferric chloride hexahydrate, 2-3 parts ferrous chloride tetrahydrate, 0.5-1 parts sodium citrate, 2-4 parts 3-aminopropyltriethoxysilane, 0.1-0.3 parts succinic anhydride, 0.6-1.0 parts zinc nitrate hexahydrate, 1.2-1.6 parts 2-methylimidazole, 40-60 parts ethanol, 80-120 parts methanol, and 100-120 parts deionized water. S2. Dissolve ferric chloride hexahydrate and ferrous chloride tetrahydrate in deionized water, add sodium citrate, bubble with nitrogen for 30-40 minutes to remove oxygen, add 20-30% ammonia water dropwise at 60-70℃ under nitrogen protection to adjust the pH to 10-11, stir vigorously at 800-1000 rpm for 1-2 hours to form a black precipitate, after magnetic separation, wash the black precipitate with ethanol and deionized water alternately 3-5 times, and vacuum dry at 50-60℃ for 4-6 hours to obtain Fe3O4 nanoparticles with a particle size of 50-100nm. S3. Disperse Fe3O4 nanoparticles in ethanol, add 3-aminopropyltriethoxysilane, sonicate for 30-40 min, reflux at 50-60℃ for 4-6 h, and after magnetic separation, wash and dry to obtain amino-modified iron(III) oxide. S4. Add amino-modified iron(III) oxide and succinic anhydride to 1 / 2 methanol and stir for 1-2 hours. Then sonicate for 20-30 minutes to obtain a suspension. S5. Dissolve zinc nitrate hexahydrate and 2-methylimidazole separately in 1 / 4 methanol and sonicate to dissolve. Mix the zinc nitrate solution with the suspension and slowly add the 2-methylimidazole solution under magnetic stirring. Transfer to a hydrothermal reactor and react at 116-124℃ for 6-8 hours. Filter and wash the filter residue with methanol and deionized water 3-5 times in sequence. Dry under vacuum at 60-70℃ for 10-12 hours to obtain the ZIF-8@Fe3O4 core-shell catalyst.

7. The method for treating high-concentration organic wastewater according to claim 1, characterized in that, In step (5), the amount of KH2PO4 added is 10-50 mg / L phosphate concentration, and the trace elements include at least one of iron, magnesium, potassium and zinc. The stirring speed is 30-60 rpm.

8. The method for treating high-concentration organic wastewater according to claim 1, characterized in that, The hollow fiber membrane in step (6) has a pore size of 0.1-0.4 μm, the amount of salt-tolerant nitrifying bacteria added is 5-10% of the sludge concentration, the amount of ozone added is 10-30 mg / L, the amount of titanium dioxide catalyst added is 1-3 g / L, and the reaction time is 30-60 min.

9. The method for treating high-concentration organic wastewater according to claim 1, characterized in that, In step (7), the amount of methanol added is 10-20 mg / L, and the dose of ultraviolet light is 30-60 mJ / cm².

10. The method for treating high-concentration organic wastewater according to claim 1, characterized in that, The pH adjuster includes at least one of sulfuric acid, hydrochloric acid, and glacial acetic acid.