CN110894125A

CN110894125A - Sewage treatment process for recycling N-methyl pyrrolidone

Info

Publication number: CN110894125A
Application number: CN201910910446.0A
Authority: CN
Inventors: 顾德华; 李亚东; 孙敏
Original assignee: Zhenjiang Xinna Environmental Protection Materials Co Ltd
Current assignee: Zhenjiang Xinna Environmental Protection Materials Co Ltd
Priority date: 2019-09-25
Filing date: 2019-09-25
Publication date: 2020-03-20

Abstract

The sewage treatment process for recovering the N-methyl pyrrolidone comprises the following steps: pretreating high-concentration wastewater; the method comprises the following steps of pretreating high-concentration wastewater, wherein the pretreatment sequentially comprises catalytic cracking, high-voltage pulse electrolysis and coagulating sedimentation; obtaining pretreated wastewater; biochemical treatment; mixing and homogenizing the pretreated wastewater in the step (1), carrying out anaerobic reaction, hydrolytic acidification and contact oxidation in sequence; obtaining biochemical treatment water; ensuring treatment; and (3) carrying out precipitation reaction, multi-medium filtration and active carbon filtration on the biochemical treatment water in the step (2) in sequence to finish recovery. The invention has the advantages of low process cost, high efficiency, good recovery effect and good wastewater treatment effect, and is expected to be widely popularized and used.

Description

Sewage treatment process for recycling N-methyl pyrrolidone

Technical Field

The invention belongs to the technical field of sewage treatment, and particularly relates to a sewage treatment process for recovering N-methyl pyrrolidone.

Background

N-methylpyrrolidone, a chinese alias: NMP; 1-methyl-2-pyrrolidone; n-methyl-2-pyrrolidone. Colorless transparent oily liquid, slightly having amine odor. Low volatility, good thermal stability and chemical stability, and can be volatilized with water vapor. It has hygroscopic property. Is sensitive to light. It is easily soluble in water, ethanol, diethyl ether, acetone, ethyl acetate, chloroform and benzene, and can dissolve most organic and inorganic compounds, polar gas, natural and synthetic high molecular compounds. N-methyl pyrrolidone is widely applied to the industries of lithium batteries, medicines, pesticides, pigments, cleaning agents, insulating materials and the like.

The current wastewater from the production of carbon nanotube slurry contains N-methyl pyrrolidone, and belongs to high-concentration refractory organic wastewater. Mainly comprises rectification production wastewater and partial equipment cleaning wastewater, wherein the CODcr concentration is less than or equal to about 50000 mg/L; the main pollution factors of the comprehensive chemical wastewater are CODER and ammonia nitrogen, and the characteristic pollutant components are mainly organic compounds such as organic solvent NMP and the like. The wastewater which is required to be treated and reaches the take-over standard of a sewage treatment plant has high organic matter concentration, complex components and stable structure, contains a certain amount of toxic substances for inhibiting the growth of organisms, and can not reach the discharge requirement by direct biochemical treatment.

Disclosure of Invention

Aiming at the problems, the invention discloses a sewage treatment process for recovering N-methyl pyrrolidone.

The specific technical scheme is as follows:

the sewage treatment process for recovering the N-methyl pyrrolidone is characterized by comprising the following steps of:

pretreating high-concentration wastewater; the method comprises the following steps of pretreating high-concentration wastewater, wherein the pretreatment sequentially comprises catalytic cracking, high-voltage pulse electrolysis and coagulating sedimentation; obtaining pretreated wastewater;

biochemical treatment; mixing and homogenizing the pretreated wastewater in the step (1), carrying out anaerobic reaction, hydrolytic acidification and contact oxidation in sequence; obtaining biochemical treatment water;

step (3) guarantee processing; and (3) carrying out precipitation reaction, multi-medium filtration and active carbon filtration on the biochemical treatment water in the step (2) in sequence to finish recovery.

Further, catalytic cracking in step (1)The solution adopts a Fenton reagent method; fe in Fenton reagent²⁺As homogeneous catalyst, and H₂O₂Has strong oxidizing ability; the Fenton reagent can generate hydroxyl free radical (HO) through catalytic decomposition to attack organic molecules and oxidize the organic molecules into CO₂、H₂Inorganic substances such as O; in this system, HO · is actually an oxidant reaction, and the reaction formula is:

Fe²⁺+H₂O₂+H⁺→Fe³⁺+H₂O+HO·

the standard Fenton reagent is prepared from H₂O₂With Fe²⁺The reaction mechanism of initiation, consumption and termination of the reaction chain of the mixed system and the standard system can be summarized as follows:

Fe²⁺+H₂O₂→Fe³⁺+OH^-+HO·

Fe²⁺+HO·→Fe³⁺+OH^-

HO₂+Fe³⁺→Fe²⁺+O₂+H⁺

HO·+H₂O₂→H₂O+HO₂·

Fe²⁺+HO₂·→Fe³⁺+HO₂ ^–

Fe³⁺+H₂O₂→Fe²⁺+HO₂+H⁺。

further, in the step (1), the high-voltage pulse electrolysis takes alloy metal such as aluminum, iron and the like as a main electrode, an external pulse high-voltage action is applied to generate an electrochemical reaction, electric energy is converted into chemical energy, the anode metal electrode is sacrificed to generate a metal cation flocculating agent, and pollutants are separated from the water body through coagulation, floatation, reduction and oxidative decomposition.

Further, in the step (1), coagulating sedimentation is to discharge the wastewater after high-voltage pulse electrolysis into an inclined tube sedimentation tank; and the step of putting the mixture into an inclined tube sedimentation tank is that a honeycomb inclined tube assembly forming a certain inclination angle with the horizontal plane is placed in a sedimentation area of the sedimentation tank.

Further, the inclination angle of the honeycomb inclined tube assembly in the step (1) is 60 degrees, and the inclination angle is the included angle between the honeycomb inclined tube assembly and the horizontal plane.

Further, the pH value of the wastewater after high-voltage pulse electrolysis is adjusted to 6-9 before coagulation and precipitation in the step (1), and a coagulant aid are metered and added through a dosing device after the pH value is adjusted.

Further, the mixing and homogenizing in the step (2) are as follows: intercepting large-particle floating objects in the pretreated wastewater by a grating and then collecting the large-particle floating objects in a comprehensive adjusting tank; the tank is internally provided with a perforation aeration stirring device for stirring and homogenizing the collected wastewater.

Further, the anaerobic reaction in the step (2) is as follows: and carrying out anaerobic reaction on the wastewater by using a composite baffled anaerobic reactor.

Further, in the step (2), the hydrolysis acidification is that the wastewater after the anaerobic reaction is introduced into a hydrolysis acidification tank, and the reaction process is controlled in two stages of hydrolysis and acidification in the anaerobic digestion process in the hydrolysis acidification tank; hydrolysis refers to biochemical reaction carried out outside the cells before organic matters enter the microbial cells; the microorganism completes the biocatalytic reaction by releasing extracellular free enzyme or immobilized enzyme connected on the outer wall of the cell; acidification is a typical type of fermentation process; hydrolysis is a necessary process for degrading macromolecular organic matters, and the macromolecular organic matters are required to be utilized by microorganisms and must be hydrolyzed into micromolecular organic matters firstly, so that the micromolecular organic matters can enter bacterial cells for further degradation; acidification is an accelerated process of organic matter degradation, because the hydrolyzed small molecular organic matter is further converted into simple compounds and secreted outside cells, and organic matters such as carbohydrates and the like are degraded into organic acids mainly including acetic acid, butyric acid, propionic acid and the like in an acid production stage.

Further, in the step (2), the contact oxidation is that the wastewater which is hydrolyzed and acidified is introduced into a contact oxidation tank, and the structure of the contact oxidation tank comprises a tank body, a filler, a water distribution device and an aeration device; filling materials are arranged in the aeration tank and are used as carriers of biological films; the wastewater to be treated flows through the filler at a certain flow rate after being oxygenated, and is contacted with the biological membrane for purification; a nitrifying liquid reflux pump is arranged in the tank to enhance the biological denitrification capability; the aeration device adopts a rotary mixing type aerator to improve the utilization rate of oxygen.

Furthermore, the JBM novel combined biological filler is placed in the comprehensive adjusting tank, the hydrolysis acidification tank and the contact oxidation tank for mixing and homogenizing to accelerate the biological decomposition process.

Further, the precipitation reaction in the step (3) is that the mixture is introduced into a final sedimentation tank, the final sedimentation tank comprises a coagulation reaction section and a sedimentation zone, and a coagulant aid are added in the coagulation reaction section in a metering manner; arranging a honeycomb inclined pipe assembly in the settling zone; the bottom of the settling zone is connected with a sludge pump, and the sludge pump is connected with a sludge tank; the top of the settling zone is connected with a pipeline which is connected with a discharge monitoring pool; the settled sludge is discharged into a sludge tank by a sludge pump, and the supernatant automatically flows into a discharge monitoring tank for monitoring; and directly discharging and recycling if the monitoring reaches the standard, and entering multi-medium filtration if the monitoring does not reach the standard.

Further, the multi-medium filter in the step (3) adopts a multi-medium filter, and the multi-medium filter is quartz sand and manganese sand.

Further, the activated carbon filter in the step (3) is an activated carbon filter.

The working principle and the beneficial effects of the invention are as follows:

(1) fe in Fenton reagent²⁺As a homogeneous catalyst, and H₂O₂Has strong oxidizing ability. Is particularly suitable for treating organic wastewater with high concentration, difficult degradation and large toxicity. The Fenton reagent has very high oxidation capacity because of H₂O₂In Fe²⁺Under the catalytic action of the compound, the generated hydroxyl radicals HO & lt- & gt and other oxidants have stronger oxidation electrode potential and strong oxidation performance, so that a plurality of organic matters which are difficult to biodegrade and oxidize by a common oxidation method can be effectively decomposed, and HO & lt- & gt has higher electronegativity or electron affinity.

For the HO · addition of water-soluble high molecular compounds (polyvinyl alcohol, polyacrylamide) and water-soluble propylene derivatives (acrylonitrile, acrylic acid, allyl alcohol, methyl acrylate, etc.) to the C ═ C bond, the double bond is cleaved and then oxidized to CO₂(ii) a For saturated aliphatic hydroxy compounds (acetic acid)Ethyl acetate acetone and acetaldehyde), the main chain is a stable compound, HO & can only oxidize the main chain into carboxylic acid, and the compound is oxidized and decomposed into a straight carbon chain micromolecule compound by a complex macromolecular structure substance; for aromatic compounds, HO · can destroy aromatic rings to form aliphatic compounds, thereby eliminating the biotoxicity of aromatic compounds.

(2) The high-voltage pulse electrolysis mainly has four main functions of electrochemistry: electrolytic oxidation, electrolytic reduction, electrolytic flocculation and electrolytic air flotation are integrated to carry out comprehensive decomposition and separation on pollutants in water.

a. Electrolytic oxidation

The oxidation during electrolysis can be divided into two categories. One is direct oxidation, that is, the pollutant loses electrons directly at the anode and oxidation occurs; the other is indirect oxidation, using anions with a lower electrode potential in solution, e.g. OH^-、Cl^-Active species such as [ O ] which lose electrons at the anode to form new stronger oxidants]、[OH]、Cl₂And the like. The active substances are used for oxygenolysis of BOD in water₅、COD、NH₃-N, etc.

b. Electrolytic reduction

The reduction in the electrolysis process can be divided into two categories. One is direct reduction, i.e., the contaminant directly gains electrons at the cathode and reduction occurs. The other is indirect reduction, and the positive ions in the pollutants firstly obtain electrons at the cathode, so that the high-valence metal positive ions in the electrolyte obtain electrons at the cathode and are directly reduced into low-valence positive ions or metal precipitates.

c. Electrolytic flocculation

Soluble anode such as Fe and Al, and high-voltage pulse DC, the anode loses electrons to form metal cation Fe²⁺、 Al³⁺With OH in solution^-The flocculant has strong adsorption capacity and flocculation effect superior to that of common flocculant, and can adsorb and coprecipitate the pollutant in waste water to eliminate pollutant.

d. Electrolytic air flotation

The electrolytic air flotation is to electrolyze the wastewater and ionize water molecules to generate H⁺And OH^-And the hydrogen and the oxygen are respectively separated out on the surfaces of the cathode plate and the anode plate under the driving of an electric field. The diameter of the newly generated bubbles is very small, the diameter of the hydrogen bubbles is about 10-30 μm, and the diameter of the oxygen bubbles is about 20-60 μm; compared with the diameters (100-150 μm) of the bubbles generated during the pressurized dissolved air floatation and the diameters (800-1000 μm) of the bubbles generated during the mechanical stirring. It is understood that the bubbles generated by electrolysis have a higher ability to trap fine impurity particles than the latter two, and the dispersion degree of the bubbles is high, and the bubbles float up as carriers adhering to suspended solids in water, thereby easily removing contaminants. The electrolytic air flotation can remove hydrophobic pollutants in the wastewater and can also remove hydrophilic pollutants in the wastewater.

2) Efficiency of electrolytic reactor

The electrode plate of the electrolytic reactor can be made of different materials according to different substances to be removed, so that the effects of strong flocculation, strong oxidation, strong reduction, strong air flotation and the like are generated, the best treatment effect is achieved, and iron, aluminum, titanium, graphite, lead dioxide and the like are frequently applied. Each material has its own field of application, and the design of the electrolytic reactor and the choice of electrode plates are determined by a great deal of research and development trials and a great deal of engineering and practical experience. The electrolytic reactor is verified to have the following effects on removing various impurities in wastewater according to a large number of experiments:

a. oil

The oily sewage is different in the components and the existing state of oil pollutants in the water body according to different sources. The oil exists in the sewage body in the following 5 types: suspension oil, dispersion oil, emulsified oil, dissolved oil, oil-solid.

Wherein, the suspended oil, the dispersed oil and the oil-solid can be removed better by simple mechanical separation or air flotation separation. The most difficult oil to treat is emulsified oil, the oil is in an emulsion state in water, O/W type emulsified particles are easily formed, the particle size is less than 1 mu m, a layer of electric double layer with negative charges is often covered on the surface, the system is stable, and the oil is difficult to float on the water surface and is difficult to treat. The electrolytic reactor can make charged emulsified oil particles generate directional migration by utilizing the action of a strong electric field, the electric nuclei are neutralized on the surface of an electrode plate, destabilization polymerization is realized, meanwhile, the high-efficiency flocculation groups generated by electrolysis can also well destroy the double electric layer structure of oil drops, the demulsification effect is realized, a large amount of oil drops subjected to demulsification by the micro-bubbles generated by synergistic reaction are removed by air floatation, and the removal rate can reach more than 90%.

From practical experience, the effluent can reach below 50mg/L under the condition that the content of the inlet water oil is hundreds to tens of thousands mg/L aiming at the oil extraction wastewater of the oil field and the oil-containing wastewater of the oil refinery.

b、CODer

The organic matters in the industrial sewage are various in types and very complex in components, and the types of the organic matters are different according to different industries. They can be classified into soluble organic substances and non-soluble organic substances according to their solubility, and into readily biodegradable organic substances and hardly biodegradable organic substances according to their biodegradability.

The electrolysis technology has better removal effect on organic matters with high concentration and difficult biochemical degradation.

The electrolysis technology utilizes the efficient electrolytic flocculation effect to generate high-activity flocculation groups with extremely strong adsorbability, and has good removal effect on non-soluble high-molecular organic matters. Meanwhile, the combination of the electro-flotation and the electro-oxidation can further improve the removal rate of the organic matters, especially for the organic matters which are difficult to be biochemically degraded, chemical bonds can be cut off through strong oxidation, the biodegradability of the organic matters is improved, and the aim of fully degrading CODcr can be fulfilled by combining a biochemical treatment method.

The removal rate of the electrolysis technology for CODcr is generally 30-80% according to different water quality conditions.

c. Heavy metal ion

The heavy metal ions in the general wastewater are mainly as follows: copper, chromium, nickel, iron, manganese, zinc, and the like.

For removing iron and manganese ions, an aeration method is generally adopted to convert the iron and manganese ions into high-valence oxides and hydroxides so as to convert the iron and manganese ions from an ionic state into an insoluble state to be separated out from water,then removed by filtration. The electrolysis technology generates OH in water during the electric reaction^-The ions are combined with iron ions and manganese ions to form insoluble substances to be separated out, and then the insoluble substances are matched with sand filtration equipment, so that the heavy metal ions in the water can be effectively removed. The removal rate can reach 80 to 95 percent.

The chromium ion removal is mainly aimed at Cr in the electroplating wastewater⁶⁺Due to Cr⁶⁺The toxicity is high, and the Cr needs to be reduced to Cr with low toxicity³⁺Reuse of Cr³⁺With OH^-And removing the neutralization precipitate. Electrolytic production of Fe by electrolysis²⁺Which is used as a reducing agent for reducing Cr in water⁶⁺Fully converted into Cr in a low valence state³⁺And then OH produced by the reaction^-And separating and removing the generated precipitate. The removal rate of the electrolysis technology to the chromium ions can reach more than 90 percent.

d. Turbidity, suspended matter

The electrolytic technology can realize good adsorption flocculation on colloid particles and various impurity particles in water due to the efficient flocculation, so that tiny particles in water are polymerized into larger floccules, and the formed floccules are larger and more compact than floccules formed by adding a flocculating agent, thereby being beneficial to settling, intercepting and separating from water. The effluent treated by the electrocoagulation technology is combined with the precipitation and filtration technology, so that the effluent turbidity can be controlled below 3NTU, and if the raw water turbidity is very high (>100NTU), the flocculation effect same as that of the lower turbidity water can be achieved only by simply changing the operation parameters.

The removal rate of turbidity and suspended matters by the electrolysis technology can reach more than 90 percent.

e、SiO₂Colloidal silica, silicone

SiO₂When the supersaturated state is reached, the SiO precipitates from the water, and the influence on a membrane filtration system is often large because the precipitated SiO₂It adheres to the membrane surface and must be removed in a controlled manner during pretreatment of the membrane.

Flocculation can adsorb SiO₂Precipitation from water, typical flocculants for SiO₂The removal rate of the catalyst is 30 to 40 percent, and the electrolysis technologyFor SiO₂The removal rate of the catalyst can reach 70 to 90 percent.

f. Color intensity

The chroma is generally caused by chromophoric functional groups in organic matters, such as dyeing and printing, and the chroma of waste water in the dye industry is very high. The electrolysis technology has a good effect on removing high-chroma water, and the strong oxidation and strong reduction effects of the electrolysis technology can destroy the color development functional groups of organic matters and reduce the chroma of water quality. The removal rate of the electrolysis technology to the chroma is generally more than 80 percent.

g. Bacteria and virus

The electrolysis technology utilizes the action of a strong electric field between polar plates and the oxidation action of strong oxidizing radicals generated by reaction to remove and kill bacteria and viruses in water, and the removal rate can reach more than 80 percent.

The high-voltage pulse electrolysis has the technical characteristics of low investment cost, low operating cost, low maintenance and repair cost, no need of adding any chemical agent, small occupied area, simple operation, high automation degree, short equipment treatment time, high treatment efficiency, wide wastewater adaptation range, capability of simultaneously treating various pollutants, less sludge generated by equipment treatment and high sludge compactness, and solves the passivation problem of the traditional electrolysis polar plate by adding pulse current.

(3) A combined baffling type anaerobic reactor (FABR), also called as a third-generation anaerobic reactor, has strong biological solid interception capability and good hydraulic mixing condition. With the development of anaerobic technology, the hydraulic design of the process has been developed from simple plug flow or complete mixing to mixed complex hydraulic flow regime. The third generation anaerobic reactor has the characteristics that: the reactors have good hydraulic flow state, and most of water flow in the reactors is in a composite flow state combining plug flow and complete mixed flow through structural improvement, so that the reactors have high volume utilization rate and can obtain stronger processing capacity; the device has good interception capability of biosolids, and microorganisms in one reactor grow in different areas and contact with inlet water at different stages, so that the separation of the biological phases is realized to a certain extent, and the treatment effect of the device can be stabilized and improved; by the structural improvement, the flow path of water flow in the reactor is prolonged, thereby promoting the contact of wastewater and sewage.

The composite baffling type anaerobic reactor is a novel efficient anaerobic reactor developed on the basis of UASB, and has the advantages that:

① reactor structure-simple structure, no moving parts, low cost, high volume utilization rate, uneasy blockage, low sludge bed expansion degree, low total height of the reactor, low investment cost and low operation cost.

② Biomass characteristic-no special requirement for settling property of organism, low sludge yield, less residual sludge, long sludge life, no need for sludge growth on carrier surface, and no need for sludge-water separation in subsequent sedimentation tank.

③ its advantages are short hydraulic stay time, intermittent running, high resistance to water and organic impact, high resistance to toxic and harmful substances in water, and long running time without discharging mud

(4) The purpose of hydrolytic acidification is mainly to convert non-soluble organic matters in the original wastewater into soluble organic matters and mainly convert organic matters which are difficult to biodegrade into organic matters which are easy to biodegrade, thereby improving the biodegradability of the wastewater, reducing the pH value of the sewage and reducing the sludge yield so as to be beneficial to subsequent aerobic treatment. The hydrolytic acidification tank can improve the removal effect of the whole system on organic matters and suspended matters, and reduce the organic load of the aerobic system, so that the energy consumption of the whole system is greatly reduced compared with that of the aerobic system used alone.

(5) The biological membrane in the contact oxidation pond and the suspended activated sludge act together to achieve the function of purifying the wastewater. The biological treatment is a link after physical and chemical treatment and is also an important link in the whole circulation flow, and harmful substances such as ammonia/nitrogen, nitrous acid, nitrate, cyanogen sulfide and the like are removed.

(6) The multi-media filter is a process of clarifying water by passing the water with high turbidity through a certain thickness of granular or non-granular material under a certain pressure by using one or more filter media, thereby effectively removing suspended impurities. The multi-medium filter is mainly used for water treatment and turbidity removal, pre-stage pretreatment of softened water and pure water and the like, and the turbidity of the outlet water can reach below 3 ℃.

(7) The activated carbon filter is a pressure container filled with a coarse quartz sand cushion layer and high-quality activated carbon. In a water quality pretreatment system, an activated carbon filter can adsorb pollutants such as micromolecular organic matters leaked from a previous stage, and has obvious adsorption and removal effects on peculiar smell, colloid, pigment, heavy metal ions, COD (chemical oxygen demand) and the like in water. SDI <5, TOC <2.Oppm can be guaranteed.

The operation of the activated carbon filter is accomplished by a carbon bed. The active carbon particles forming the carbon bed have very many micropores and huge specific surface area, and have very strong physical adsorption capacity. The water passes through the carbon bed, and the organic pollutants in the water are effectively adsorbed by the activated carbon. In addition, the amorphous part of the surface of the active carbon has some oxygen-containing tube energy groups, so that the organic pollutants in the water passing through the carbon bed are effectively adsorbed by the active carbon.

Detailed Description

In order to make the technical solution of the present invention clearer and more clear, the present invention is further described below, and any solution obtained by substituting technical features of the technical solution of the present invention with equivalents and performing conventional reasoning falls within the scope of the present invention.

The coagulant in the examples of the present invention was PAC, available from sumac wetting water treatment technologies ltd, and the coagulant aid used was PAM). The model of the composite baffled anaerobic reactor is FABR-JBM combined filler, the specification is 4500x5000x3000mm, and the composite baffled anaerobic reactor is purchased from Yixing Delrin environmental protection Limited company.

Example 1

Further, the catalytic cracking in the step (1) adopts a Fenton reagent method; fe in Fenton reagent²⁺As homogeneous catalyst, and H₂O₂Has strong oxidizing ability; the Fenton reagent can generate hydroxyl free radical (HO) through catalytic decomposition to attack organic molecules and oxidize the organic molecules into CO₂、H₂Inorganic substances such as O; in this system, HO · is actually an oxidant reaction, and the reaction formula is:

Fe²⁺+H₂O₂+H⁺→Fe³⁺+H₂O+HO·

Fe²⁺+H₂O₂→Fe³⁺+OH^-+HO·

Fe²⁺+HO·→Fe³⁺+OH^-

HO₂+Fe³⁺→Fe²⁺+O₂+H⁺

HO·+H₂O₂→H₂O+HO₂·

Fe²⁺+HO₂·→Fe³⁺+HO₂ ^–

Fe³⁺+H₂O₂→Fe²⁺+HO₂+H⁺。

Further, the pH value of the wastewater after high-voltage pulse electrolysis is adjusted to 7 before coagulation and precipitation in the step (1), and coagulant aid are metered and added by a dosing device after the pH value is adjusted

In this example, the dosage of the chemicals is taken as an example of treating 100 tons of wastewater per day

Serial number	Name (R)	Dosage (kg/day)
			1	H₂O₂(content: 30%)	35kg
2	FeSO₄(content: 27%)	70kg
			3	NaOH (caustic soda flakes, content 99%)	5
4	HCl (technical grade, content 31%)	10
			5	PAC	10
6	PAM	0.5

Wherein H₂O₂With FeSO₄For constituting a Fenton reagent; NaOH and HCl are used for adjusting the PH value of the wastewater; PAC is coagulant and PAM is coagulant aid.

Effects of embodiments of the invention

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

A process for treating sewage from the recovery of N-methylpyrrolidone, which comprises the following steps:

pretreating high-concentration wastewater; the method comprises the following steps of pretreating high-concentration wastewater, wherein the pretreatment sequentially comprises catalytic cracking, high-voltage pulse electrolysis and coagulating sedimentation; obtaining pretreated wastewater;

biochemical treatment; mixing and homogenizing the pretreated wastewater in the step (1), carrying out anaerobic reaction, hydrolytic acidification and contact oxidation in sequence; obtaining biochemical treatment water;

step (3) guarantee processing; and (3) carrying out precipitation reaction, multi-medium filtration and active carbon filtration on the biochemical treatment water in the step (2) in sequence to finish recovery.
2. The process for treating sewage containing N-methylpyrrolidone, as claimed in claim 1, wherein the catalytic cracking in the step (1) is carried out by using "Fenton's reagent method"; fe in Fenton reagent²⁺As a homogeneous catalyst, and H₂O₂Has strong oxidizing ability; the Fenton reagent can generate hydroxyl free radical (HO) through catalytic decomposition to attack organic molecules and oxidize the organic molecules into CO₂、H₂Inorganic substances such as O; in this system, HO · is actually an oxidant reaction, and the reaction formula is:

Fe²⁺+H₂O₂+H⁺→Fe³⁺+H₂O+HO·

the standard Fenton reagent is prepared from H₂O₂With Fe²⁺The reaction mechanism of initiation, consumption and termination of the reaction chain of the mixed system and the standard system can be summarized as follows:

Fe²⁺+H₂O₂→Fe³⁺+OH^-+HO·

Fe²⁺+HO·→Fe³⁺+OH^-

HO₂+Fe³⁺→Fe²⁺+O₂+H⁺

HO·+H₂O₂→H₂O+HO₂·

Fe²⁺+HO₂·→Fe³⁺+HO₂ ^–

Fe³⁺+H₂O₂→Fe²⁺+HO₂+H⁺。
3. the process for treating sewage containing N-methylpyrrolidone, as claimed in claim 1, wherein the high voltage pulse electrolysis in step (1) is carried out by using an alloy metal such as aluminum, iron, etc. as a main electrode, applying an applied pulse high voltage to generate an electrochemical reaction, converting electric energy into chemical energy, sacrificing an anode metal electrode to generate a metal cation flocculant, and separating contaminants from the water body by coagulation, floatation, reduction and oxidative decomposition.
4. The process for treating sewage containing N-methylpyrrolidone as claimed in claim 1, wherein the coagulating sedimentation in the step (1) is to discharge the waste water after the high-voltage pulse electrolysis into an inclined tube sedimentation tank; and the step of putting the mixture into an inclined tube sedimentation tank is that a honeycomb inclined tube assembly forming a certain inclination angle with the horizontal plane is placed in a sedimentation area of the sedimentation tank.
5. The process for treating sewage from N-methylpyrrolidone recovery according to claim 1, wherein the pH of the wastewater after the high-pressure pulse electrolysis is adjusted before the coagulation and precipitation in step (1), and the coagulant and coagulant aid are added by metering with a dosing device after the pH adjustment.
6. The process for treating sewage containing N-methylpyrrolidone, as claimed in claim 1, wherein the mixing and homogenizing in step (2) is: intercepting large-particle floaters in the pretreated wastewater by a grating and then collecting the wastewater in a comprehensive adjusting tank; the tank is internally provided with a perforation aeration stirring device for stirring and homogenizing the collected wastewater.
7. The process for wastewater treatment with N-methylpyrrolidone recovery according to claim 1, wherein the anaerobic reaction in the step (2) is: and carrying out anaerobic reaction on the wastewater by using a composite baffled anaerobic reactor.
8. The process for treating sewage containing N-methylpyrrolidone, as claimed in claim 1, wherein the hydrolysis acidification in step (2) is carried out by introducing the wastewater after anaerobic reaction into a hydrolysis acidification tank, wherein the reaction process is controlled in two stages of hydrolysis and acidification in the anaerobic digestion process in the hydrolysis acidification tank; hydrolysis refers to biochemical reaction carried out extracellularly before organic matters enter microbial cells; the microorganism completes the biocatalytic reaction by releasing extracellular free enzyme or immobilized enzyme connected on the outer wall of the cell; acidification is a typical type of fermentation process; hydrolysis is a necessary process for degrading macromolecular organic matters, and the macromolecular organic matters are required to be utilized by microorganisms and must be hydrolyzed into micromolecular organic matters firstly, so that the micromolecular organic matters can enter bacterial cells for further degradation; acidification is an accelerated process of organic matter degradation, because the hydrolyzed small molecular organic matter is further converted into simple compounds and secreted outside cells, and organic matters such as carbohydrates and the like are degraded into organic acids mainly including acetic acid, butyric acid, propionic acid and the like in an acid production stage.
9. The process for treating sewage containing N-methylpyrrolidone as claimed in claim 1, wherein the contact oxidation in the step (2) is carried out by introducing the hydrolysis-acidified wastewater into a contact oxidation tank, and the structure of the contact oxidation tank comprises a tank body, a filler, a water distribution device and an aeration device; filling materials are arranged in the aeration tank and are used as carriers of biological films; the wastewater to be treated flows through the filler at a certain flow rate after being oxygenated, and is contacted with the biological membrane for purification; a nitrifying liquid reflux pump is arranged in the tank to enhance the biological denitrification capability; the aeration device adopts a rotary mixing type aerator to improve the utilization rate of oxygen.
10. The process for treating sewage containing N-methylpyrrolidone as claimed in claim 1, wherein the precipitation reaction in step (3) is carried out by introducing into a final sedimentation tank, the final sedimentation tank comprises a coagulation reaction section and a sedimentation zone, and a coagulant aid are added in the coagulation reaction section in a metered manner; arranging a honeycomb inclined pipe assembly in the settling zone; the bottom of the sedimentation zone is connected with a sludge pump, and the sludge pump is connected with a sludge tank; the top of the settling zone is connected with a pipeline which is connected with a discharge monitoring pool; the settled sludge is discharged into a sludge tank by a sludge pump, and the supernatant automatically flows into a discharge monitoring tank for monitoring; and directly discharging and recycling if the monitoring reaches the standard, and entering multi-medium filtration if the monitoring does not reach the standard.