A method for treating N-methylpyrrolidone industrial wastewater

Abstract

The present invention discloses a method for treating N-methylpyrrolidone industrial wastewater, which combines the processes of chemical sedimentation, microbial decomposition and activated carbon adsorption, improves the efficiency of ammonia nitrogen reduction, and reduces the time consumption. It is an environmentally friendly and fast method for treating N-methylpyrrolidone industrial wastewater. The present invention reduces the waste and secondary pollution of the precipitant by using a recyclable precipitant slow-release ball that releases layer by layer from the center of the sphere; then uses a modified biological rope filler in the aeration tank to shorten the time for microbial film formation and degradation; finally, uses modified coconut shell activated carbon in the adsorption tank to adsorb residual harmful substances, so that the ammonia nitrogen value of the final effluent is reduced to less than 5 mg / L.

Description

Technical Field

[0001] The present invention relates to a method for treating high ammonia nitrogen industrial wastewater, and particularly to a method for treating N-methylpyrrolidone industrial wastewater. Background Art

[0002] N-methylpyrrolidone industrial wastewater mainly includes rectification wastewater and amination wastewater generated during the production process of N-methylpyrrolidone. The main pollutant indicators are high concentrations of COD (chemical oxygen demand), total nitrogen (NT), and ammonia nitrogen, which are a relatively difficult type to treat in chemical industrial wastewater.

[0003] High ammonia nitrogen wastewater mainly comes from industries such as food processing, chemical fertilizers, metallurgical production, oil refining, and pharmaceuticals. Generally, nitrogen exists in water in two forms: organic nitrogen and inorganic nitrogen. In recent years, with the rapid development of China's economy, a large amount of high ammonia nitrogen wastewater is generated every year. If this high ammonia nitrogen wastewater is discharged without treatment, it will cause eutrophication of water bodies and seriously affect the health of water resources. N-methylpyrrolidone industrial wastewater belongs to high ammonia nitrogen wastewater. Its wastewater is clear and transparent and has a pungent odor. Chemical sedimentation can be used, but it is not easy to control the addition amount. When excessive, it not only wastes the precipitant but also easily causes secondary pollution. It can also be degraded by microorganisms, but when the concentration is high, it will inhibit the growth of microorganisms. Therefore, it is necessary to strictly control the influent concentration of the biochemical treatment in the sewage treatment plant. At the same time, high ammonia nitrogen wastewater has an inhibitory effect on conventional activated sludge, and it is difficult for microorganisms to form a biofilm in a high ammonia nitrogen environment.

[0004] Providing a method for treating high ammonia nitrogen industrial wastewater that is convenient to operate and has a simple process is the research direction of the present invention. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the technical problem to be solved by the present invention is: to invent a method specifically for treating N-methylpyrrolidone industrial wastewater containing high ammonia nitrogen, and to solve the problems of low efficiency of traditional wastewater treatment processes and difficulty in forming a biofilm for microorganisms.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention includes the following steps:

[0007] A method for treating N-methylpyrrolidone industrial wastewater includes the following steps:

[0008] (1) Add N-methylpyrrolidone industrial wastewater into a sedimentation tank, input sedimentation agent slow-release balls at a ratio of 3 - 5 kg per ton of wastewater, adjust the pH to 8.0 with a 3% mass fraction NaOH solution, and after standing for 1 d, discharge it through a 20-mesh filter screen;

[0009] (2) The wastewater discharged from the sedimentation tank enters the aeration tank with modified biological rope fillers suspended with nitrifying bacteria biofilm for nitrification, and the blower aeration is turned on to maintain the dissolved oxygen at 2 mg / L. After 1 day of reaction, it is discharged.

[0010] (3) The wastewater discharged from the aeration tank enters the anaerobic tank with sodium acetate-coated modified biological rope fillers suspended with denitrifying bacteria biofilm for denitrification, and a carbon source is added. After 1 day of reaction, it is discharged.

[0011] (4) The wastewater discharged from the anaerobic tank enters the adsorption tank. In the adsorption tank, 60 - 75 kg of modified coconut shell activated carbon is added, and it is stirred at a rate of 120 r / min for 1 - 2 h, then left to stand for 5 h and passed through a 50-mesh filter screen to complete the wastewater treatment.

[0012] Among them, the preparation method of the precipitant slow-release ball is as follows:

[0013] a. Preparation of the precipitant: Disodium hydrogen phosphate dodecahydrate and magnesium chloride hexahydrate are mixed and stirred evenly according to a weight ratio of 0.8:1.

[0014] b. Preparation of the adhesive slow-release agent: 1 - 2 parts of sodium carboxymethylcellulose are mixed and stirred with 98 - 99 parts of distilled water to obtain a sodium carboxymethylcellulose colloidal solution.

[0015] c. Preparation of the hydrophobic modified corn starch emulsion: 30 parts of corn starch are added to 100 parts of deionized water, stirred evenly, and kept at a constant temperature of 35 °C for subsequent steps. The pH is adjusted to 8.0 with a 3% mass fraction NaOH solution, and while stirring, octenyl succinic anhydride is dropped at a rate of 20 drops / min for 30 min. After dropping, 0.8% of methyl sodium silicate based on the starch mass is added, and stirring continues for 10 min and then left to stand for 30 min to obtain the hydrophobic modified corn starch emulsion.

[0016] d. Sieve out 2,4,6 - tribromophenol soft particles with a size of 3 - 5 mm, place them in the adhesive slow-release agent for 2 - 3 s and then fish them out. After standing for 5 min, the precipitant and the slow-release ball are loaded into a disk-type ball rolling machine according to a weight ratio of 1:1, and rolled and coated for 3 - 5 min. Then, the excess precipitant is sieved out through a sieve with a 1 cm pore diameter. Then, continue according to the coating sequence of the adhesive slow-release agent - precipitant until the diameter of the slow-release ball reaches 3 - 4 cm. Finally, it is placed in the hydrophobic modified corn starch emulsion for 5 min and then fished out and dried at 40 °C for standby. Open 3 - 5 1-mm holes leading to the ball center of the dried slow-release ball, then immerse the slow-release ball in a 75% ethanol solution, ultrasonically vibrate for 20 min, take it out and dry at 40 °C to obtain the precipitant slow-release ball.

[0017] Among them, the preparation method of the modified biological rope filler is as follows:

[0018] Mix the original chromic acid cleaning solution and distilled water evenly at a ratio of 1:2. After heating to 55°C, completely immerse several 2-m long biological rope fillers in it. After soaking for 30 minutes, take out the biological rope fillers and wash them with distilled water 2 - 3 times. Let half of them air dry naturally for later use, and immerse the other half in a 20% sodium acetate solution at 35°C for 12 hours and then take them out to air dry naturally; Hang the modified biological rope fillers without sodium acetate coating in the aeration tank, and hang the modified biological rope fillers coated with sodium acetate in the anaerobic tank, and 3 - 5 pieces can be hung per square meter.

[0019] Among them, the method of film formation is as follows:

[0020] i. Nitrifying bacteria film formation:

[0021] Drain the wastewater from the sedimentation tank into the aeration tank with the modified biological rope fillers without sodium acetate coating suspended. Adjust the temperature of the aeration tank to 20 - 25°C. Stop injecting water when the injection volume reaches 1 / 3 of the capacity of the aeration tank. Then blow air for 30 minutes, then add 30 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 8 hours. After that, continue to inject water until it reaches 2 / 3 of the capacity of the aeration tank and stop injecting water. Then blow air for 30 minutes, then add 20 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 8 hours. After that, continue to inject water until it is full, then blow air for 30 minutes, then add 15 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 1 day, and the film formation of nitrifying bacteria can be completed;

[0022] ii. Denitrifying bacteria film formation:

[0023] Drain the wastewater from the aeration tank into the anaerobic tank with the modified biological rope fillers coated with sodium acetate suspended. Adjust the temperature of the anaerobic tank to 20 - 25°C. Stop injecting water when the injection volume reaches 1 / 3 of the capacity of the anaerobic tank. Then add 30 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 8 hours. After that, continue to inject water until it reaches 2 / 3 of the capacity of the anaerobic tank and stop injecting water. Then add 20 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 8 hours. After that, continue to inject water until it is full, then add 15 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 1 day, and the film formation of denitrifying bacteria can be completed.

[0024] Among them, film formation only needs to be carried out when the aeration tank and the anaerobic tank are used for the first time;

[0025] Among them, the residue in the sedimentation tank is dried at 40°C and then passed through a sieve with a pore size of 2 cm to realize the recovery of the slow-release balls; the precipitate is magnesium ammonium phosphate crystals with a particle size of less than 2 cm, which can be recovered as compound fertilizer, and the slow-release balls are spherical objects with a particle size greater than 3 cm. After drying, the slow-release balls and magnesium ammonium phosphate precipitates can be separated by a sieve with a pore size of 2 cm; the recovered slow-release balls can be separated by a mass screening machine to separate the slow-release balls with completely consumed precipitants, and the precipitants that have not been used up can be reused. The slow-release balls with used precipitants can be dried and crushed and used as a supplementary carbon source for denitrifying bacteria in anaerobic tanks.

[0026] The carbon source is methanol, or a 1:1 mixture of methanol and a substance obtained by drying and crushing the shell of the sustained-release ball after the precipitant has been used.

[0027] Wherein, the preparation method of modified coconut shell activated carbon is:

[0028] a) adding coconut shell activated carbon into a ball mill and grinding it, and collecting coconut shell activated carbon particles with a particle size of 20 mesh;

[0029] b) immersing the coconut shell activated carbon particles in a 4 mol / L nitric acid solution, stirring in a constant temperature water bath at 35°C for 6 hours, then washing with distilled water for 2-3 times, and finally drying at 100°C;

[0030] c) The acid-washed coconut shell activated carbon particles were immersed in a 200 mg / L polyepoxysuccinic acid aqueous solution, stirred at a speed of 120 r / min for 6 h, filtered and naturally dried to obtain modified coconut shell activated carbon particles.

[0031] The characteristics of the present invention are:

[0032] 1) The precipitant sustained-release sphere prepared by the present invention dissolves and removes 2,4,6-tribromophenol in the center of the sphere by ethanol, so that the precipitant becomes a hollow sphere with holes. After being put into a precipitation tank, the precipitant coated with sodium carboxymethyl cellulose is gradually released from the center of the sphere. This method avoids the waste of raw materials and realizes the recovery of the precipitant.

[0033] 2) Chemical precipitation method has the advantages of fast, convenient and recyclable precipitates for treating high ammonia nitrogen wastewater, but it also has certain defects, such as incomplete reaction of added reagents, easy to cause secondary pollution, and less metered and divided addition will waste time and manpower. Therefore, the present invention uses precipitant slow-release balls to simulate the effect of divided addition, avoiding waste of precipitant, and the recyclable environmentally friendly material of slow-release balls does not affect subsequent microbial degradation. The precipitant coating shell made of corn starch has the following advantages compared with other starches: low cost and suitable for large-scale use, good elasticity and low viscosity after molding, and will not stick to the precipitate. Hydrophobic modification of corn starch can effectively coat the precipitant.

[0034] 3) For conventional biological rope fillers, several high-quality varieties resistant to corrosion, temperature, and aging in polyolefins and polyamides are selected. Using special wire drawing and wire strip hair-making processes, the wire strips are interspersed and fixed on a corrosion-resistant and high-strength central rope. The fillers can be evenly stretched and distributed three-dimensionally and omni-directionally in the effective area, enabling full mixing, penetration, and contact exchange of gas, water, and biofilm. However, due to its insufficiently rough surface, when applied to the treatment of high-concentration ammonia-nitrogen wastewater, there are problems such as difficult film formation and uneven film formation. Therefore, it needs to be modified. The purpose of using chromic acid cleaning solution to oxidize the surface of the biological rope filler in the present invention is that the low-concentration chromic acid cleaning solution can oxidize the surface of the biological rope filler, remove excess organic matter, and form a micro-porous structure on its surface, which is beneficial for the coating of sodium acetate. The advantage of sodium acetate as a carbon source is that it can immediately respond to the denitrification process and is very suitable as the carbon source required during the film formation of denitrifying bacteria. A rough surface has a thicker laminar boundary layer than a smooth surface, which can provide a good static hydraulic environment, thus avoiding the adverse effects of water shear force on the growth of attached microorganisms. Therefore, in the initial stage of biofilm formation, the modified biological rope filler prepared in the present invention with a large specific surface area and surface roughness can accelerate the biofilm formation rate and increase the amount of microbial film formation.

[0035] 4) Activated carbon is usually used in wastewater treatment to adsorb residual harmful substances. However, ordinary activated carbon is prone to powdering and losing its adsorption function when soaked in water for a long time, and many closed pores cannot be utilized. The modified coconut shell activated carbon prepared in the present invention exposes its closed small pores through pickling, thereby enhancing its adsorption function, and then is modified by coating with polyepoxysuccinic acid. Polyepoxysuccinic acid is a nitrogen-free and phosphorus-free green water treatment chemical with dual functions of scale inhibition and corrosion inhibition. It can protect the coconut shell activated carbon from being eroded when soaked in water for a long time and prevent sludge from coating on the coconut shell activated carbon, thus not affecting the water purification effect. Embodiment

[0036] The present invention will be further described in detail below with reference to the embodiments.

[0037] The N-methylpyrrolidone industrial wastewater used in the embodiments of the present invention is all wastewater of the same batch and with the same ammonia-nitrogen concentration. For the rest of the raw materials or chemical reagents, unless otherwise specified, they are all obtained through conventional commercial channels. Embodiment

[0038] This embodiment includes the following steps:

[0039] 1. Preparation of precipitant sustained-release balls:

[0040] 1) Preparation of the precipitant: Mix 40 kg of disodium hydrogen phosphate dodecahydrate and 50 kg of magnesium chloride hexahydrate evenly with stirring;

[0041] 2) Preparation of the adhesive slow-release agent: Mix 2 kg of sodium carboxymethylcellulose with 98 L of distilled water and stir to obtain a sodium carboxymethylcellulose colloidal solution;

[0042] 3) Preparation of the hydrophobic modified corn starch emulsion: Add 30 kg of corn starch to 100 L of deionized water, stir evenly, keep the temperature at 35 °C for subsequent steps, adjust the pH to 8.0 with a 3% (mass fraction) NaOH solution, start dropping octenyl succinic anhydride at a rate of 20 drops / min while stirring, stop dropping after 30 min of dropping, add 240 g of sodium methyl silicate based on the mass of the starch, continue stirring for 10 min and then let it stand for 30 min to obtain the hydrophobic modified corn starch emulsion;

[0043] 4) Weigh 10 kg of 2,4,6-tribromophenol soft particles with a size of 3 - 5 mm, place them in the adhesive for 2 - 3 s and then fish them out. After standing for 5 min, load the precipitant and the slow-release balls into a disk-type ball rolling machine according to a weight ratio of 1:1, roll and coat for 4 min, then screen out the excess precipitant through a sieve with a 1 cm pore size. Then continue the coating sequence of the adhesive slow-release agent - precipitant until the slow-release balls can pass through a sieve with a 4 cm pore size and be retained on a sieve with a 3 cm pore size. Finally, place them in the hydrophobic modified corn starch emulsion for 5 min, then fish them out and dry them at 40 °C for standby. Open 4 small holes with a diameter of 1 mm leading to the center of the dried slow-release balls, then immerse the slow-release balls in a 75% ethanol solution, ultrasonically vibrate for 20 min and then take them out and dry them at 40 °C to obtain the precipitant slow-release balls;

[0044] 2. Preparation of the modified biological rope filler:

[0045] Mix 5 L of the original chromic acid cleaning solution with 10 L of distilled water evenly, heat it to 55 °C, then completely immerse 80 biological rope fillers with a length of 2 m in it. After soaking for 30 min, take out the biological rope fillers and wash them 2 times with distilled water. Among them, 40 are air-dried for standby, and the other 40 are immersed in a 20% sodium acetate solution at 35 °C for 12 h and then taken out and air-dried; The modified biological rope filler without sodium acetate coating is suspended in the aeration tank, and the modified biological rope filler coated with sodium acetate is suspended in the anaerobic tank, with 4 suspended per square meter;

[0046] 3. Microbial film formation:

[0047] i. Nitrifying bacteria film formation:

[0048] The wastewater discharged from the sedimentation tank is injected into the aeration tank with modified biological rope fillers without sodium acetate coating suspended. The temperature of the aeration tank is adjusted to 23 °C. When the water injection volume reaches 1 / 3 of the capacity of the aeration tank, the water injection stops. Then, air is blown for 30 minutes, and then 30 ml of concentrated nitrifying bacteria water is added. After stirring evenly, it is left standing for 8 hours. Then, the water injection continues until it reaches 2 / 3 of the capacity of the aeration tank, and the water injection stops. Then, air is blown for 30 minutes, and then 20 ml of concentrated nitrifying bacteria water is added. After stirring evenly, it is left standing for 8 hours. Then, the water injection continues until it is full, and then air is blown for 30 minutes, and then 15 ml of concentrated nitrifying bacteria water is added. After stirring evenly, it is left standing for 1 day, and the film formation of nitrifying bacteria can be completed;

[0049] ii. Denitrifying bacteria film formation:

[0050] The wastewater discharged from the aeration tank is injected into the anaerobic tank with modified biological rope fillers coated with sodium acetate suspended. The temperature of the anaerobic tank is adjusted to 23 °C. When the water injection volume reaches 1 / 3 of the capacity of the anaerobic tank, the water injection stops. Then, 30 ml of concentrated denitrifying bacteria water is added. After stirring evenly, it is left standing for 8 hours. Then, the water injection continues until it reaches 2 / 3 of the capacity of the anaerobic tank, and the water injection stops. Then, 20 ml of concentrated denitrifying bacteria water is added. After stirring evenly, it is left standing for 8 hours. Then, the water injection continues until it is full, and then 15 ml of concentrated denitrifying bacteria water is added. After stirring evenly, it is left standing for 1 day, and the film formation of denitrifying bacteria can be completed;

[0051] 4. Preparation of modified coconut shell activated carbon:

[0052] 1) Add 80 kg of coconut shell activated carbon to the ball mill for ball milling, and collect coconut shell activated carbon particles with a particle size of 20 mesh;

[0053] 2) Immerse the above-mentioned coconut shell activated carbon particles in a 4 mol / L nitric acid solution, stir in a constant temperature water bath at 35 °C for 6 hours, then wash twice with distilled water, and finally dry at 100 °C;

[0054] 2) Immerse the above-mentioned pickled coconut shell activated carbon particles in a 200 mg / L polyepoxysuccinic acid aqueous solution, stir at a rotation speed of 120 r / min for 6 hours, filter and air-dry naturally to obtain modified coconut shell activated carbon particles;

[0055] 5. Treatment of N-methylpyrrolidone industrial wastewater:

[0056] (1) Add 20 tons of N-methylpyrrolidone industrial wastewater to the sedimentation tank, add 80 kg of precipitant slow-release balls, adjust the pH to 8.0 with a 3% mass fraction NaOH solution, leave it standing for 1 day, and then discharge it through a 20-mesh filter screen;

[0057] (2) The wastewater filtered in the sedimentation tank enters the aeration tank with modified biological rope fillers hanging with nitrifying bacteria biofilms for nitrification, and the blower aeration is turned on to maintain the dissolved oxygen at 2 mg / L. The wastewater reacts for 1 day and then is discharged;

[0058] (3) The wastewater discharged from the above aeration tank enters the anaerobic tank with sodium acetate-coated modified biological rope fillers hanging with denitrifying bacteria biofilms for denitrification, and 1 kg of methanol is added as a carbon source. The wastewater reacts for 1 day and then is discharged;

[0059] (4) The wastewater discharged from the above anaerobic tank enters the adsorption tank. 70 kg of modified coconut shell activated carbon is added to the adsorption tank, and it is stirred at a rate of 120 r / min for 1.5 h and then left to stand for 5 h. After passing through a 50-mesh filter screen, the wastewater treatment is completed. Example

[0060] This example includes the following steps:

[0061] 1. Preparation of precipitant slow-release balls:

[0062] 1) Preparation of precipitant: 32 kg of disodium hydrogen phosphate dodecahydrate and 40 kg of magnesium chloride hexahydrate are mixed and stirred evenly;

[0063] 2) Preparation of adhesive slow-release agent: 2 kg of sodium carboxymethylcellulose is mixed with 98 L of distilled water and stirred to obtain a sodium carboxymethylcellulose colloidal solution;

[0064] 3) Preparation of hydrophobic modified corn starch emulsion: 30 kg of corn starch is added to 100 L of deionized water, stirred evenly, and kept at a constant temperature of 35 °C for subsequent steps. The pH is adjusted to 8.0 with a 3% mass fraction NaOH solution. While stirring, octenyl succinic anhydride is added dropwise at a rate of 20 drops / min for 30 min and then the addition is stopped. 240 g of sodium methyl silicate based on the mass of the starch is added, and stirring is continued for 10 min and then left to stand for 30 min to obtain the hydrophobic modified corn starch emulsion;

[0065] 4) Weigh 8 kg of 2,4,6-tribromophenol soft particles with a size of 3-5 mm, place them in the adhesive for 2-3 s and then fish them out. After standing for 5 min, the precipitant and slow-release balls are loaded into a disk-type ball rolling machine according to a weight ratio of 1:1, and rolled and coated for 3 min. Then, the excess precipitant is sieved through a 1 cm aperture sieve. Then, continue according to the coating sequence of adhesive slow-release agent - precipitant until the slow-release balls can pass through a 4 cm aperture sieve and are retained on a 3 cm aperture sieve. Finally, they are placed in the hydrophobic modified corn starch emulsion for 5 min and then fished out and dried at 40 °C for standby. Three 1 mm holes leading to the center of the ball are opened in the dried slow-release balls, and then the slow-release balls are immersed in a 75% ethanol solution, ultrasonically vibrated for 20 min and then taken out and dried at 40 °C to obtain the precipitant slow-release balls;

[0066] 2. Preparation of modified biological rope filler:

[0067] Mix 3 L of the original chromic acid cleaning solution evenly with 6 L of distilled water. After heating to 55 °C, completely immerse 60 pieces of 2-m-long biological rope fillers in it. After soaking for 30 min, take out the biological rope fillers and wash them twice with distilled water. Among them, 30 pieces are air-dried for standby, and the other 30 pieces are immersed in a 20% sodium acetate solution at 35 °C for 12 h and then taken out and air-dried naturally; the modified biological rope fillers without sodium acetate coating are suspended in the aeration tank, and the modified biological rope fillers coated with sodium acetate are suspended in the anaerobic tank, with 3 pieces suspended per square meter;

[0068] 3. Microbial film formation:

[0069] i. Nitrifying bacteria film formation:

[0070] The wastewater discharged from the sedimentation tank is injected into the aeration tank with the modified biological rope fillers without sodium acetate coating suspended. The temperature of the aeration tank is adjusted to 20 °C. When the water injection volume reaches 1 / 3 of the capacity of the aeration tank, stop water injection, then blow air and aerate for 30 min, then add 30 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 8 h. After that, continue to inject water until the water injection volume reaches 2 / 3 of the capacity of the aeration tank, then stop water injection, then blow air and aerate for 30 min, then add 20 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 8 h. After that, continue to inject water until it is full, then blow air and aerate for 30 min, then add 15 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 1 d, and the film formation of nitrifying bacteria can be completed;

[0071] ii. Denitrifying bacteria film formation:

[0072] The wastewater discharged from the aeration tank is injected into the anaerobic tank with the modified biological rope fillers coated with sodium acetate suspended. The temperature of the anaerobic tank is adjusted to 20 °C. When the water injection volume reaches 1 / 3 of the capacity of the anaerobic tank, stop water injection, then add 30 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 8 h. After that, continue to inject water until the water injection volume reaches 2 / 3 of the capacity of the anaerobic tank, then stop water injection, then add 20 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 8 h. After that, continue to inject water until it is full, then add 15 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 1 d, and the film formation of denitrifying bacteria can be completed;

[0073] 4. Preparation of modified coconut shell activated carbon:

[0074] 1) Add 70 kg of coconut shell activated carbon to the ball mill for ball milling, and collect coconut shell activated carbon particles with a particle size of 20 mesh;

[0075] 2) Immerse the above-mentioned coconut shell activated carbon particles in a 4 mol / L nitric acid solution, stir in a constant temperature water bath at 35 °C for 6 h, then wash twice with distilled water, and finally dry at 100 °C;

[0076] 2) Immerse the above-mentioned pickled coconut shell activated carbon particles in an aqueous solution of polyepoxysuccinic acid at 200 mg / L, stir at a speed of 120 r / min for 6 h, filter and air-dry naturally to obtain modified coconut shell activated carbon particles;

[0077] 5. Treatment of N-methylpyrrolidone industrial wastewater:

[0078] (1) Add 20 tons of N-methylpyrrolidone industrial wastewater to the sedimentation tank, add 60 kg of precipitant slow-release balls, adjust the pH to 8.0 with a 3% (mass fraction) NaOH solution, let it stand for 1 d, and then discharge through a 20-mesh filter screen;

[0079] (2) The wastewater filtered in the above sedimentation tank enters the aeration tank with modified biological rope fillers hanging with nitrifying bacteria biofilms for nitrification, and start blowing aeration to maintain the dissolved oxygen at 2 mg / L. The wastewater reacts for 1 d and then is discharged;

[0080] (3) The wastewater discharged from the above aeration tank enters the anaerobic tank with modified biological rope fillers hanging with denitrifying bacteria biofilms coated with sodium acetate for denitrification, and add 800 g of methanol and 200 g of corn starch as carbon sources. The wastewater reacts for 1 d and then is discharged;

[0081] (4) The wastewater discharged from the above anaerobic tank enters the adsorption tank, add 60 kg of modified coconut shell activated carbon to the adsorption tank, stir at a rate of 120 r / min for 1.5 h, then let it stand for 5 h and pass through a 50-mesh filter screen to complete the wastewater treatment. Example

[0082] This example includes the following steps:

[0083] 1. Preparation of precipitant slow-release balls:

[0084] 1) Preparation of precipitant: Mix 48 kg of disodium hydrogen phosphate dodecahydrate and 60 kg of magnesium chloride hexahydrate evenly;

[0085] 2) Preparation of adhesive slow-release agent: Mix 2 kg of sodium carboxymethylcellulose with 98 L of distilled water and stir to obtain a sodium carboxymethylcellulose colloidal solution;

[0086] 3) Preparation of hydrophobically modified corn starch emulsion: Add 30 kg of corn starch to 100 L of deionized water, stir evenly, keep the temperature at 35 °C for subsequent steps, adjust the pH to 8.0 with 3% (mass fraction) NaOH solution, start dropping octenyl succinic anhydride at a rate of 20 drops / min while stirring, stop dropping after 30 min, add 240 g of sodium methyl silicate based on the mass of starch, continue stirring for 10 min and then let it stand for 30 min to obtain the hydrophobically modified corn starch emulsion;

[0087] 4) Weigh 12 kg of 2,4,6-tribromophenol soft particles with a size of 3 - 5 mm, place them in the adhesive for 2 - 3 s and then take them out. After standing for 5 min, load the precipitant and the slow-release ball into a disk-type ball rolling machine according to a weight ratio of 1:1, roll and coat for 5 min, then screen out the excess precipitant through a sieve with a 1 cm aperture, and then continue coating in the order of adhesive slow-release agent - precipitant until the slow-release ball can pass through a sieve with a 4 cm aperture and be retained on a sieve with a 3 cm aperture. Finally, place it in the hydrophobically modified corn starch emulsion for 5 min, take it out and dry it at 40 °C for standby. Open 5 small holes with a diameter of 1 mm leading to the center of the dried slow-release ball, then immerse the slow-release ball in a 75% ethanol solution, ultrasonically vibrate for 20 min, take it out and dry it at 40 °C to obtain the precipitant slow-release ball;

[0088] 2. Preparation of modified biological rope filler:

[0089] Mix 5 L of chromic acid cleaning solution stock solution with 10 L of distilled water evenly, heat it to 55 °C, then completely immerse 100 biological rope fillers with a length of 2 m in it. After soaking for 30 min, take out the biological rope fillers and wash them twice with distilled water. Among them, 50 are left to dry naturally for standby, and the other 50 are immersed in a 20% sodium acetate solution at 35 °C for 12 h and then taken out to dry naturally; The modified biological rope filler without sodium acetate coating is hung in the aeration tank, and the modified biological rope filler coated with sodium acetate is hung in the anaerobic tank, with 5 hung per square meter;

[0090] 3. Microbial film formation:

[0091] i. Nitrifying bacteria film formation:

[0092] The wastewater discharged from the sedimentation tank is injected into the aeration tank where modified biological rope fillers without sodium acetate coating are suspended. The temperature of the aeration tank is adjusted to 25°C. When the water injection volume reaches 1 / 3 of the capacity of the aeration tank, stop water injection, then blow air for 30 minutes, then add 30 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 8 hours. After that, continue water injection until it reaches 2 / 3 of the capacity of the aeration tank, then stop water injection, then blow air for 30 minutes, then add 20 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 8 hours. After that, continue water injection until it is full, then blow air for 30 minutes, then add 15 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 1 day to complete the film hanging of nitrifying bacteria;

[0093] ii. Film hanging of denitrifying bacteria:

[0094] The wastewater discharged from the aeration tank is injected into the anaerobic tank where modified biological rope fillers coated with sodium acetate are suspended. The temperature of the anaerobic tank is adjusted to 25°C. When the water injection volume reaches 1 / 3 of the capacity of the anaerobic tank, stop water injection, then add 30 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 8 hours. After that, continue water injection until it reaches 2 / 3 of the capacity of the anaerobic tank, then stop water injection, then add 20 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 8 hours. After that, continue water injection until it is full, then add 15 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 1 day to complete the film hanging of denitrifying bacteria;

[0095] 4. Preparation of modified coconut shell activated carbon:

[0096] 1) Add 100 kg of coconut shell activated carbon to a ball mill for ball milling, and collect coconut shell activated carbon particles with a particle size of 20 mesh;

[0097] 2) Immerse the above coconut shell activated carbon particles in a 4 mol / L nitric acid solution, stir in a constant temperature water bath at 35°C for 6 hours, then wash 3 times with distilled water, and finally dry at 100°C;

[0098] 2) Immerse the above pickled coconut shell activated carbon particles in a 200 mg / L polyepoxysuccinic acid aqueous solution, stir at a speed of 120 r / min for 6 hours, filter and air-dry naturally to obtain modified coconut shell activated carbon particles;

[0099] 5. Treatment of N-methylpyrrolidone industrial wastewater:

[0100] (1) Add 20 tons of N-methylpyrrolidone industrial wastewater to the sedimentation tank, add 100 kg of precipitant slow-release balls, adjust the pH to 8.0 with a 3% mass fraction NaOH solution, let it stand for 1 day and then discharge through a 20-mesh filter screen;

[0101] (2) The wastewater filtered in the sedimentation tank enters the aeration tank with modified biological rope fillers hanging with nitrifying bacteria biofilms for nitrification, and the blower aeration is turned on to maintain the dissolved oxygen at 2 mg / L. The wastewater reacts for 1 day and then is discharged;

[0102] (3) The wastewater discharged from the aeration tank enters the anaerobic tank with modified biological rope fillers coated with sodium acetate and hanging with denitrifying bacteria biofilms for denitrification, and 500 g of methanol and 500 g of corn starch are added as carbon sources. The wastewater reacts for 1 day and then is discharged;

[0103] (4) The wastewater discharged from the anaerobic tank enters the adsorption tank. 75 kg of modified coconut shell activated carbon is added to the adsorption tank, and it is stirred at a rate of 120 r / min for 1.5 h, and then left to stand for 5 h. After passing through a 50-mesh filter screen, the wastewater treatment is completed. Example

[0104] The difference between this comparative example and Example 1 is that the precipitant in step 1) is: 40 g of disodium hydrogen phosphate and 50 g of magnesium oxide are mixed and stirred evenly. Example

[0105] The difference between this comparative example and Example 1 is that the precipitant in step 1) is: 40 g of sodium phosphate and 50 g of magnesium chloride are mixed and stirred evenly. Example

[0106] 1. Prepare the precipitant:

[0107] Mix 40 kg of disodium hydrogen phosphate dodecahydrate and 50 kg of magnesium chloride hexahydrate evenly;

[0108] 2. Prepare the modified biological rope fillers:

[0109] Mix 5 L of the original chromic acid cleaning solution with 10 L of distilled water evenly. After heating to 55 °C, completely immerse 80 2-m-long biological rope fillers in it. After soaking for 30 min, take out the biological rope fillers and wash them 2 times with distilled water. Among them, 40 are air-dried for later use, and the other 40 are immersed in a 20% sodium acetate solution at 35 °C for 12 h and then taken out and air-dried; The modified biological rope fillers without sodium acetate coating are hung in the aeration tank, and the modified biological rope fillers coated with sodium acetate are hung in the anaerobic tank, with 4 hung per square meter;

[0110] 3. Microbial biofilm formation:

[0111] i. Nitrifying bacteria biofilm formation:

[0112] The wastewater discharged from the sedimentation tank is injected into the aeration tank with modified biological rope fillers without sodium acetate coating suspended. The temperature of the aeration tank is adjusted to 23°C. When the water injection volume reaches 1 / 3 of the capacity of the aeration tank, the water injection stops. Then, air is blown for 30 minutes. Then, 30 ml of concentrated nitrifying bacteria water is added. After stirring evenly, it is left standing for 8 hours. After that, the water injection continues until it reaches 2 / 3 of the capacity of the aeration tank and then stops. Then, air is blown for 30 minutes. Then, 20 ml of concentrated nitrifying bacteria water is added. After stirring evenly, it is left standing for 8 hours. After that, the water injection continues until it is full. Then, air is blown for 30 minutes. Then, 15 ml of concentrated nitrifying bacteria water is added. After stirring evenly, it is left standing for 1 day to complete the film formation of nitrifying bacteria;

[0113] ii. Film formation of denitrifying bacteria:

[0114] The wastewater discharged from the aeration tank is injected into the anaerobic tank with modified biological rope fillers coated with sodium acetate suspended. The temperature of the anaerobic tank is adjusted to 23°C. When the water injection volume reaches 1 / 3 of the capacity of the anaerobic tank, the water injection stops. Then, 30 ml of concentrated denitrifying bacteria water is added. After stirring evenly, it is left standing for 8 hours. After that, the water injection continues until it reaches 2 / 3 of the capacity of the anaerobic tank and then stops. Then, 20 ml of concentrated denitrifying bacteria water is added. After stirring evenly, it is left standing for 8 hours. After that, the water injection continues until it is full. Then, 15 ml of concentrated denitrifying bacteria water is added. After stirring evenly, it is left standing for 1 day to complete the film formation of denitrifying bacteria;

[0115] 4. Preparation of modified coconut shell activated carbon:

[0116] 1) Add 80 kg of coconut shell activated carbon to the ball mill for ball milling, and collect coconut shell activated carbon particles with a particle size of 20 mesh;

[0117] 2) Immerse the above coconut shell activated carbon particles in a 4 mol / L nitric acid solution, stir in a constant temperature water bath at 35°C for 6 hours, then wash twice with distilled water, and finally dry at 100°C;

[0118] 2) Immerse the above pickled coconut shell activated carbon particles in a 200 mg / L aqueous solution of polyepoxysuccinic acid, stir at a speed of 120 r / min for 6 hours, filter and air-dry naturally to obtain modified coconut shell activated carbon particles;

[0119] 5. Treatment of N-methylpyrrolidone industrial wastewater:

[0120] (1) Add 20 tons of N-methylpyrrolidone industrial wastewater to the sedimentation tank, add 80 kg of precipitant, adjust the pH to 8.0 with a 3% (mass fraction) NaOH solution, leave it standing for 1 day, and then discharge it through a 20-mesh filter screen;

[0121] (2) The wastewater filtered in the sedimentation tank enters the aeration tank with modified biological rope fillers hanging with nitrifying bacteria biofilms for nitrification, and the blower aeration is turned on to maintain the dissolved oxygen at 2 mg / L. After the wastewater reacts for 1 day therein, it is discharged;

[0122] (3) The wastewater discharged from the aeration tank enters the anaerobic tank with modified biological rope fillers coated with sodium acetate and hanging with denitrifying bacteria biofilms for denitrification, and 1 kg of methanol is added as a carbon source. After the wastewater reacts for 1 day therein, it is discharged;

[0123] (4) The wastewater discharged from the anaerobic tank enters the adsorption tank, 70 kg of modified coconut shell activated carbon is added to the adsorption tank, and after stirring at a rate of 120 r / min for 1.5 h, it is left to stand for 5 h and then passed through a 50-mesh filter screen to complete the wastewater treatment. Example

[0124] 1. Preparation of precipitant slow-release balls:

[0125] 1) Preparation of the precipitant: Mix 40 kg of disodium hydrogen phosphate dodecahydrate and 50 kg of magnesium chloride hexahydrate evenly by stirring;

[0126] 2) Preparation of the adhesive slow-release agent: Mix 2 kg of sodium carboxymethylcellulose with 98 L of distilled water and stir to obtain a sodium carboxymethylcellulose colloidal solution;

[0127] 3) Preparation of the hydrophobic modified corn starch emulsion: Add 30 kg of corn starch to 100 L of deionized water, stir evenly, keep the temperature at 35 °C constant for the subsequent steps, adjust the pH to 8.0 with a 3% mass fraction NaOH solution, start dropping octenyl succinic anhydride at a rate of 20 drops / min while stirring, stop dropping after 30 min, add 240 g of sodium methyl silicate based on the mass of the starch, continue stirring for 10 min and then leave to stand for 30 min to obtain the hydrophobic modified corn starch emulsion;

[0128] 4) Weigh 10 kg of 2,4,6-tribromophenol soft particles with a size of 3 - 5 mm, place them in the adhesive for 2 - 3 s and then take them out, leave to stand for 5 min, then put the precipitant and the slow-release balls into a disk-type ball rolling machine according to a weight ratio of 1:1, roll and coat for 4 min, and then screen out the excess precipitant through a sieve with a 1 cm pore size. Then continue according to the coating sequence of the adhesive slow-release agent - precipitant until the slow-release balls can pass through a sieve with a 4 cm pore size and be retained on a sieve with a 3 cm pore size. Finally, place them in the hydrophobic modified corn starch emulsion for 5 min, take them out and dry them at 40 °C for standby. Open 4 small holes with a diameter of 1 mm leading to the center of the slow-release balls, then immerse the slow-release balls in a 75% ethanol solution, ultrasonically vibrate for 20 min, take them out and dry them at 40 °C to obtain the precipitant slow-release balls;

[0129] 2. Hanging biological rope fillers:

[0130] Suspend 40 pieces of biological rope fillers in the aeration tank and 40 pieces of biological rope fillers in the anaerobic tank, with 4 pieces suspended per square meter.

[0131] 3. Microbial film formation:

[0132] i. Nitrifying bacteria film formation:

[0133] The wastewater discharged from the sedimentation tank is injected into the aeration tank with suspended biological rope fillers. The temperature of the aeration tank is adjusted to 23 °C. Stop injecting water when the water injection volume reaches 1 / 3 of the capacity of the aeration tank, then blow air for 30 min, then add 30 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 8 h. After that, continue injecting water until it reaches 2 / 3 of the capacity of the aeration tank, then stop injecting water, then blow air for 30 min, then add 20 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 8 h. After that, continue injecting water until it is full, then blow air for 30 min, then add 15 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 1 day, and the film formation of nitrifying bacteria can be completed.

[0134] ii. Denitrifying bacteria film formation:

[0135] The wastewater discharged from the aeration tank is injected into the anaerobic tank with suspended biological rope fillers. The temperature of the anaerobic tank is adjusted to 23 °C. Stop injecting water when the water injection volume reaches 1 / 3 of the capacity of the anaerobic tank, then add 30 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 8 h. After that, continue injecting water until it reaches 2 / 3 of the capacity of the anaerobic tank, then stop injecting water, then add 20 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 8 h. After that, continue injecting water until it is full, then add 15 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 1 day, and the film formation of denitrifying bacteria can be completed.

[0136] 4. Preparation of modified coconut shell activated carbon:

[0137] 1) Add 80 kg of coconut shell activated carbon to a ball mill for ball milling, and collect coconut shell activated carbon particles with a particle size of 20 mesh.

[0138] 2) Immerse the above-mentioned coconut shell activated carbon particles in a 4 mol / L nitric acid solution, stir in a constant temperature water bath at 35 °C for 6 h, then wash twice with distilled water, and finally dry at 100 °C.

[0139] 2) Immerse the above-mentioned acid-washed coconut shell activated carbon particles in a 200 mg / L aqueous solution of polyepoxysuccinic acid, stir at a speed of 120 r / min for 6 h, filter and air-dry naturally to obtain modified coconut shell activated carbon particles.

[0140] 5. Treatment of N-methylpyrrolidone industrial wastewater:

[0141] (1) Add 20 tons of N-methylpyrrolidone industrial wastewater to the sedimentation tank, add 80 kg of precipitant slow-release balls, adjust the pH to 8.0 with 3% (mass fraction) NaOH solution, and after standing for 1 day, drain through a 20-mesh filter screen;

[0142] (2) The wastewater filtered in the above sedimentation tank enters the aeration tank with modified biological rope fillers hanging with nitrifying bacteria biofilm for nitrification, and start the blower aeration to maintain the dissolved oxygen at 2 mg / L. After the wastewater reacts in it for 1 day, it is drained;

[0143] (3) The wastewater discharged from the above aeration tank enters the anaerobic tank with modified biological rope fillers coated with sodium acetate and hanging with denitrifying bacteria biofilm for denitrification, and put 1 kg of methanol as a carbon source. After the wastewater reacts in it for 1 day, it is drained;

[0144] (4) The wastewater discharged from the above anaerobic tank enters the adsorption tank. Add 70 kg of modified coconut shell activated carbon to the adsorption tank, stir at a rate of 120 r / min for 1.5 h, and after standing for 5 h, drain through a 50-mesh filter screen to complete the wastewater treatment. Example

[0145] 1. Preparation of precipitant slow-release balls:

[0146] 1) Preparation of precipitant: Mix 40 kg of disodium hydrogen phosphate dodecahydrate and 50 kg of magnesium chloride hexahydrate evenly;

[0147] 2) Preparation of adhesive slow-release agent: Mix 2 kg of sodium carboxymethylcellulose with 98 L of distilled water to prepare a sodium carboxymethylcellulose colloidal solution;

[0148] 3) Preparation of hydrophobic modified corn starch emulsion: Add 30 kg of corn starch to 100 L of deionized water, stir evenly, keep the temperature at 35 °C for subsequent steps, adjust the pH to 8.0 with 3% (mass fraction) NaOH solution, start to drip octenyl succinic anhydride at a rate of 20 drops / min while stirring, stop dripping after 30 min of dripping, add 240 g of sodium methyl silicate based on the mass of starch, continue to stir for 10 min and then stand for 30 min to obtain the hydrophobic modified corn starch emulsion;

[0149] 4) Weigh 10 kg of 2,4,6-tribromophenol soft particles with a size of 3 - 5 mm, place them in the adhesive for 2 - 3 s and then fish them out. After standing for 5 min, load the precipitant and the slow-release balls into a disk-type ball rolling machine according to a weight ratio of 1:1, roll and coat for 4 min, then screen out the excess precipitant through a sieve with a 1 cm aperture. Then continue the coating sequence of the adhesive slow-release agent - precipitant until the slow-release balls can pass through a sieve with a 4 cm aperture and be retained on a sieve with a 3 cm aperture. Finally, place them in a hydrophobic modified corn starch emulsion for 5 min, then fish them out and dry them at 40 °C for standby. Open 4 small holes with a diameter of 1 mm leading to the center of the dried slow-release balls, then immerse the slow-release balls in a 75% ethanol solution, ultrasonically oscillate for 20 min, take them out and dry them at 40 °C to obtain the precipitant slow-release balls;

[0150] 2. Preparation of modified biological rope packing:

[0151] Mix 5 L of the original chromic acid cleaning solution evenly with 10 L of distilled water. After heating to 55 °C, completely immerse 80 biological rope packings with a length of 2 m in it. After soaking for 30 min, take out the biological rope packings and wash them 2 times with distilled water. Among them, 40 are air-dried for standby, and the other 40 are immersed in a 20% sodium acetate solution at 35 °C for 12 h and then taken out and air-dried; The modified biological rope packing without sodium acetate coating is hung in the aeration tank, and the modified biological rope packing coated with sodium acetate is hung in the anaerobic tank, with 4 hung per square meter;

[0152] 3. Microbial film formation:

[0153] i. Nitrifying bacteria film formation:

[0154] The wastewater discharged from the sedimentation tank is injected into the aeration tank with the modified biological rope packing without sodium acetate coating hung. The temperature of the aeration tank is adjusted to 23 °C. When the water injection volume reaches 1 / 3 of the capacity of the aeration tank, stop water injection, then blow air and aerate for 30 min, then add 30 ml of concentrated nitrifying bacteria water, stir evenly and then stand for 8 h. After that, continue to inject water until the water injection volume reaches 2 / 3 of the capacity of the aeration tank, stop water injection, then blow air and aerate for 30 min, then add 20 ml of concentrated nitrifying bacteria water, stir evenly and then stand for 8 h. After that, continue to inject water until it is full, then blow air and aerate for 30 min, then add 15 ml of concentrated nitrifying bacteria water, stir evenly and then stand for 1 day to complete the film formation of nitrifying bacteria;

[0155] ii. Denitrifying bacteria film formation:

[0156] The wastewater discharged from the aeration tank is injected into the anaerobic tank with bio-rope fillers coated with sodium acetate. The temperature of the anaerobic tank is adjusted to 23°C. When the water injection volume reaches 1 / 3 of the anaerobic tank capacity, stop the water injection. Then add 30 ml of concentrated denitrifying bacteria solution, stir evenly and let it stand for 8 h. After that, continue the water injection until it reaches 2 / 3 of the anaerobic tank capacity, then stop the water injection. Then add 20 ml of concentrated denitrifying bacteria solution, stir evenly and let it stand for 8 h. After that, continue the water injection until it is full, and then add 15 ml of concentrated denitrifying bacteria solution, stir evenly and let it stand for 1 day to complete the film hanging of denitrifying bacteria.

[0157] 4. Preparation of activated carbon particles:

[0158] Add 80 kg of conventional wood activated carbon to the ball mill and grind it to collect activated carbon particles with a particle size of 20 mesh.

[0159] 5. Treatment of N-methylpyrrolidone industrial wastewater:

[0160] (1) Add 20 tons of N-methylpyrrolidone industrial wastewater to the sedimentation tank, add 80 kg of precipitant slow-release balls, adjust the pH to 8.0 with 3% (mass fraction) NaOH solution, let it stand for 1 day and then discharge it through a 20-mesh filter screen.

[0161] (2) The wastewater filtered in the above sedimentation tank enters the aeration tank with modified bio-rope fillers with nitrifying bacteria film hanging for nitrification, and start the blower aeration to maintain the dissolved oxygen at 2 mg / L. The wastewater reacts for 1 day and then is discharged.

[0162] (3) The wastewater discharged from the above aeration tank enters the anaerobic tank with acetic acid sodium-coated modified bio-rope fillers with denitrifying bacteria film hanging for denitrification, and put 1 kg of methanol as the carbon source. The wastewater reacts for 1 day and then is discharged.

[0163] (4) The wastewater discharged from the above anaerobic tank enters the adsorption tank. Add 70 kg of activated carbon particles to the adsorption tank, stir at a rate of 120 r / min for 1.5 h, and then let it stand for 5 h and pass through a 50-mesh filter screen to complete the wastewater treatment.

[0164] Experiment:

[0165] Collect and detect the wastewater after treatment of each component at the final outlet. The detection items and results are shown in Table 1.

Claims

1. A method for treating N-methylpyrrolidone industrial wastewater, characterized in that, It includes the following steps: (1) Add N-methylpyrrolidone industrial wastewater into a sedimentation tank, put precipitation agent slow-release balls at a ratio of 3-5 kg per ton of wastewater, adjust the pH to 8.0 with a 3% mass fraction NaOH solution, let it stand for 1 day and then discharge it through a 20-mesh filter screen; (2) The wastewater discharged from the above sedimentation tank enters an aeration tank with modified biological rope fillers hanging with nitrifying bacteria biofilms for nitrification, and start blowing air to keep the dissolved oxygen at 2 mg / L, and discharge it after reacting for 1 day; (3) The wastewater discharged from the above aeration tank enters an anaerobic tank with modified biological rope fillers hanging with denitrifying bacteria biofilms coated with sodium acetate for denitrification, and add a carbon source, and discharge it after reacting for 1 day; (4) The wastewater discharged from the above anaerobic tank enters an adsorption tank, add 60-75 kg of modified coconut shell activated carbon into the adsorption tank, stir at a rate of 120 r / min for 1-2 h, then let it stand for 5 h and pass through a 50-mesh filter screen to complete the wastewater treatment; Among them, the preparation method of the precipitation agent slow-release ball is: 1) Preparation of the precipitation agent: Mix dibasic sodium phosphate dodecahydrate and magnesium chloride hexahydrate evenly at a weight ratio of 0.8:1; 2) Preparation of the adhesive slow-release agent: Mix 1-2 parts of sodium carboxymethylcellulose with 98-99 parts of distilled water and stir to obtain a sodium carboxymethylcellulose colloidal solution; 3) Preparation of the hydrophobic modified corn starch emulsion: Add 30 parts of corn starch into 100 parts of deionized water, stir evenly, keep it at a constant temperature of 35 °C for subsequent steps, adjust the pH to 8.0 with a 3% mass fraction NaOH solution, start dropping octenyl succinic anhydride at a rate of 20 drops / min while stirring, stop dropping after 30 min of dropping, add methyl sodium silicate at 0.8% of the starch mass, continue stirring for 10 min and then let it stand for 30 min to obtain the hydrophobic modified corn starch emulsion; 4) Screen out 2,4,6-tribromophenol soft particles with a size of 3-5 mm, place them in the adhesive slow-release agent for 2-3 s and then fish them out, let it stand for 5 min, then put the precipitation agent and the slow-release ball into a disk-type ball rolling machine at a weight ratio of 1:1, roll and coat for 3-5 min, then screen out the excess precipitation agent through a sieve with a 1 cm pore diameter, and then continue according to the coating sequence of the adhesive slow-release agent - precipitation agent until the diameter of the slow-release ball reaches 3-4 cm. Finally, place it in the hydrophobic modified corn starch emulsion for 5 min, fish it out and dry it at 40 °C for standby. Open 3-5 1-mm small holes leading to the center of the ball of the dried slow-release ball, then immerse the slow-release ball in a 75% ethanol solution, ultrasonically vibrate for 20 min, take it out and dry it at 40 °C to obtain the precipitation agent slow-release ball; Among them, the preparation method of the modified biological rope filler is: Mix the original chromic acid cleaning solution and distilled water evenly at a ratio of 1:

2. After heating to 55°C, completely immerse several 2-m long biological rope fillers in it. After soaking for 30 minutes, take out the biological rope fillers and wash them with distilled water 2-3 times. Let half of them air dry naturally for standby, and immerse the other half in a 20% sodium acetate solution at 35°C for 12 hours and then take them out to air dry naturally; Hang the modified biological rope fillers without sodium acetate coating in the aeration tank, and hang the modified biological rope fillers coated with sodium acetate in the anaerobic tank, and 3-5 pieces can be hung per square meter; Among them, the preparation method of the modified coconut shell activated carbon is as follows: 1) Add coconut shell activated carbon to a ball mill for ball milling, and collect coconut shell activated carbon particles with a particle size of 20 mesh; 2) Immerse the above coconut shell activated carbon particles in a 4 mol / L nitric acid solution, stir them in a constant temperature water bath at 35°C for 6 hours, then wash them with distilled water 2-3 times, and finally dry them at 100°C; 3) Immerse the above pickled coconut shell activated carbon particles in an aqueous solution of polyepoxysuccinic acid with a concentration of 200 mg / L, stir them at a speed of 120 r / min for 6 hours, filter and air dry them to obtain modified coconut shell activated carbon particles.

2. The method for treating N-methylpyrrolidone industrial wastewater according to claim 1, characterized in that, The method of film hanging is as follows: i. Nitrifying bacteria film hanging: The wastewater discharged from the sedimentation tank is injected into the aeration tank with the modified biological rope fillers without sodium acetate coating suspended. The temperature of the aeration tank is adjusted to 20-25°C. Stop injecting water when the water injection volume reaches 1 / 3 of the capacity of the aeration tank, then blow air for aeration for 30 minutes, then add 30 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 8 hours. Then continue to inject water until it reaches 2 / 3 of the capacity of the aeration tank and stop injecting water. Then blow air for aeration for 30 minutes, then add 20 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 8 hours. Then continue to inject water until it is full, then blow air for aeration for 30 minutes, then add 15 ml of concentrated nitrifying bacteria water, stir evenly and let it stand for 1 day to complete the film hanging of nitrifying bacteria; ii. Denitrifying bacteria film hanging: The wastewater discharged from the aeration tank is injected into the anaerobic tank with the modified biological rope fillers coated with sodium acetate suspended. The temperature of the anaerobic tank is adjusted to 20-25°C. Stop injecting water when the water injection volume reaches 1 / 3 of the capacity of the anaerobic tank, then add 30 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 8 hours. Then continue to inject water until it reaches 2 / 3 of the capacity of the anaerobic tank and stop injecting water. Then add 20 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 8 hours. Then continue to inject water until it is full, then add 15 ml of concentrated denitrifying bacteria water, stir evenly and let it stand for 1 day to complete the film hanging of denitrifying bacteria.

3. The method for treating N-methylpyrrolidone industrial wastewater according to claim 1, wherein, Step 1) also includes drying the residues in the sedimentation tank at 40°C and then passing them through a sieve with a pore diameter of 2 cm to recover the slow-release balls.

4. The method for treating N-methylpyrrolidone industrial wastewater according to claim 1, characterized in that, The carbon source is methanol, or a compound of methanol and the dried and crushed substance of the slow-release ball shell after the precipitant is used up in any proportion.

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