Biochemical treatment process for coal chemical wastewater

Abstract

The invention relates to the field of coal chemical industry, the field of environmental engineering and the technical field of sewage treatment, in particular to a biochemical treatment process for coal chemical industry wastewater, which comprises a cascade physicochemical treatment unit, a phenol ammonia recovery unit, a biochemical enhanced treatment unit and a deep treatment unit which are connected in sequence, the cascade physicochemical treatment unit is used for three-stage gradient oil removal; the phenol-ammonia recovery unit is used for removing phenol and ammonia and recovering resources; the biochemical enhanced treatment unit is used for efficiently degrading organic matters and removing nitrogen; the deep treatment unit is used for removing refractory pollutants and hardness and fluorine ions; through system integration and synergistic effects of four process units of cascade physicochemical treatment, phenol ammonia recovery, biochemical enhanced treatment and deep treatment, the whole-process efficient purification capacity for the coal chemical wastewater (such as semi-coke wastewater) is formed.

Description

Technical Field

[0001] The present invention relates to the fields of coal chemical industry, environmental engineering and sewage treatment technology, and in particular to a biochemical treatment process for coal chemical wastewater. Background Art

[0002] As an emerging industry relying on coal resources for development, the lignite industry's traditional high-energy consumption and high-emission development model is incompatible with the current increasingly stringent environmental protection requirements. It is in urgent need of transformation and upgrading to a circular economy and clean production model. Lignite wastewater (also known as semi-coke wastewater) mainly comes from the process of low-grade coal distillation at medium and low temperatures (about 600℃ to 800℃), coal gas purification, and lignite steam quenching. Due to the relatively low distillation temperature, a large amount of low-molecular organic matter is not completely oxidized and remains in the wastewater, resulting in its pollutant concentration being much higher than that of coking wastewater with similar composition, usually about 10 times that of coking wastewater.

[0003] The composition of semi-coke wastewater is extremely complex, containing high concentrations of inorganic pollutants such as ammonia nitrogen, cyanide, and sulfide, as well as organic pollutants such as oils, polycyclic aromatic hydrocarbons, and heterocyclic compounds containing nitrogen, oxygen, and sulfur. Among them, oil pollutants mainly include heavy oil such as condensed aromatic hydrocarbons, light oil such as straight-chain hydrocarbons, and a large amount of emulsified oil. These oils are not only difficult to remove by physical methods, but also cause coking and clogging of treatment equipment, affecting the stable operation of the treatment system. The biodegradability of semi-coke wastewater is extremely poor. After dephenolization, its B / C ratio is usually only 0.1 to 0.16, and in some cases it is even as low as 0.03, which makes it difficult to directly apply conventional biological treatment methods. In addition, the high concentrations of phenols and cyanide pollutants in the wastewater are biologically toxic and will have a toxic effect on water treatment microorganisms. During the water treatment process, they will cause the water treatment microorganisms to decay, lose, and die, further increasing the difficulty of wastewater treatment. For the tail water after treatment in the biochemical unit, if there is a demand for reclaimed water reuse, the hardness, fluoride ions and other pollutants in the lignite wastewater will cause scaling and clogging of the membrane system in the subsequent deep treatment, resulting in frequent cleaning of the membrane system and sometimes even damage and replacement.

[0004] Currently, the treatment methods for semi-coke wastewater mainly draw on the treatment processes of coking wastewater. Usually, physical and chemical pretreatment is required to remove pollutants that have inhibitory or toxic effects on microorganisms and improve the biodegradability of the wastewater. In recent years, the biochemical treatment technology of semi-coke wastewater has made certain progress, and technologies including activated sludge, biofilm, biological fluidized bed, and membrane bioreactor have been developed. In addition, bioaugmentation technology has gradually attracted attention for the difficult-to-degrade polycyclic aromatic hydrocarbons and phenolic organic compounds in wastewater. By adding selected dominant bacterial strains to the biological reaction system, the treatment efficiency of semi-coke wastewater can be further improved.

[0005] Despite recent progress in lignite wastewater treatment technology, it still faces numerous challenges. Existing processes still have shortcomings in terms of technical maturity, economic efficiency, and operational stability, requiring further optimization and improvement. Furthermore, the integration of treatment processes and the stability of biochemical treatment systems are pressing issues. Therefore, establishing a comprehensive biochemical treatment process for coal chemical wastewater is essential. Through system integration and optimization, this process efficiently removes pollutants such as ammonia nitrogen, total phenols, and chemical oxygen demand from lignite wastewater, effectively promoting the sustainable development of the lignite industry. Summary of the Invention

[0006] The present invention provides a biochemical treatment process for coal chemical wastewater based on a combination of "cascaded physicochemical treatment - phenol and ammonia recovery - biochemical enhanced treatment - advanced treatment." The process primarily includes multiple process flows: cascaded physicochemical treatment (three-stage gradient physicochemical oil removal of wastewater), phenol and ammonia recovery (phenol removal and ammonia removal), biochemical enhanced treatment (high-energy anaerobic, high-load aeration, anaerobic ammonium oxidation, multi-stage A / O), and advanced treatment (fluidized bed Fenton, pelletized hardness and fluoride removal, membrane system). This highly integrated process system features personalized design, simple operation, and fully automated process monitoring. The treated effluent meets the GB16171-2012 "Pollutant Emission Standard for Coking Chemical Industry."

[0007] The present invention provides the following technical solutions:

[0008] A biochemical treatment process for coal chemical wastewater, comprising a sequentially connected cascade physicochemical treatment unit, a phenol-ammonia recovery unit, a biochemical enhanced treatment unit, and a deep treatment unit, wherein:

[0009] The cascade physicochemical treatment unit is used for three-stage gradient oil removal;

[0010] The phenol-ammonia recovery unit is used for removing phenol and ammonia and recovering resources;

[0011] The biochemical enhancement treatment unit is used for efficiently degrading organic matter and removing nitrogen;

[0012] The deep treatment unit is used to remove refractory pollutants, hardness and fluoride ions.

[0013] As a further technical solution, the three-stage oil removal of the cascade physicochemical treatment unit includes:

[0014] (1) Primary oil-water separation by removing floating oil and dispersed oil through conventional oil removal equipment;

[0015] (2) adding 300-3000 mg / L of amphiphilic emulsifier and centrifuging the emulsified oil for secondary chemical demulsification;

[0016] The amphiphilic emulsifier is fatty amine polyoxyethylene ether, polyoxypropylene ether or organic amine;

[0017] (3) A three-stage new material for deep oil removal using methyltrichlorosilane-modified super-hydrophobic and oleophilic polyurethane material with a pore size of 200-400 μm to adsorb ultrafine oils, with the final oil content ≤20 mg / L.

[0018] As a further technical solution, the methyltrichlorosilane-modified super-hydrophobic and oleophilic polyurethane material is obtained by using polyurethane with a pore size of 200-400 μm as a matrix and modifying the polyurethane with methyltrichlorosilane;

[0019] The oil absorption capacity of methyltrichlorosilane-modified super-hydrophobic and oleophilic polyurethane material is 20 times its own weight, and oil separation and recovery and material reuse can be achieved through extrusion deformation.

[0020] As a further technical solution, the preparation method of the super hydrophobic and oleophilic polyurethane material is as follows: a polyurethane matrix with a pore size of 200-400 μm is ultrasonically cleaned with an ethanol-acetone mixture for 30-40 minutes, dried at 72-80°C for 3-4 hours, immersed in a methyltrichlorosilane hydrolyzate with a pH of 2-3, and reacted at room temperature for 3-4 hours under oscillation. After washing with deionized water, it is vacuum dried at 55-70°C and -0.06 to -0.08 MPa for 4-6 hours.

[0021] The methyltrichlorosilane hydrolyzate is prepared by mixing methyltrichlorosilane, deionized water and ethanol in a molar ratio of 1:3-5:5-8.

[0022] As a further technical solution, the phenol ammonia recovery unit comprises:

[0023] Double-tower, two-stage, low-temperature, low-pressure micro-evaporation module: adjusts the wastewater pH to 6-9, preheats and deacidifies at 90-110°C in the first tower, and deammonifies at -0.08MPa negative pressure in the second tower, recovering ammonia water and crude phenol to achieve ammonia nitrogen ≤500mg / L and total phenol ≤800mg / L;

[0024] Extraction and dephenolization module: N, N-bis (1-methylheptyl) acetamide or tributyl phosphate is used as the extractant, phenols are transferred by difference in distribution coefficient, and the extractant is regenerated by distillation / crystallization.

[0025] As a further technical solution, the biochemical enhancement treatment unit includes:

[0026] High-energy anaerobic reactor: Add composite fungal engineering bacteria maintained in an external live bacteria tank, with a residence time of 2-3 days and a COD removal rate of 50-65%;

[0027] High-load aeration tank: dissolved oxygen 2-3 mg / L, residence time 8-12 hours, COD removal rate ≥ 70%;

[0028] Anaerobic ammonium oxidation reactor: control temperature at 36±1℃, pH7.8±0.2, dissolved oxygen ≤0.5mg / L, NH4 + Concentration 70±10mg / L, NO2 - Concentration 90±10mg / L, denitrification rate ≥80%;

[0029] Multi-stage A / O system: built-in live bacteria tank and dosing of engineered bacteria, aerobic section stay 4-6 hours, anoxic section stay 2-3 hours, COD removal rate ≥ 60%, ammonia nitrogen removal rate ≥ 90%.

[0030] As a further technical solution, the anaerobic ammonium oxidation reactor is an autotrophic bacteria reaction system that does not require an external carbon source and saves 60% of oxygen supply compared to traditional nitrification processes.

[0031] As a further technical solution, the depth processing unit includes:

[0032] Fluidized bed Fenton reactor: using Fe 2+ It generates hydroxyl radicals with H2O2 and achieves COD removal rate ≥ 50% through gas-solid-liquid three-phase fluidization;

[0033] Pelletized hardness and fluoride removal reactor (PCR): Add crystallization reagents to make hardness ions and F- crystallize on the surface of pellet seeds, protecting the water quality of the membrane system;

[0034] Membrane system: It includes multi-media filter, ultrafiltration device and reverse osmosis device in sequence. The reverse osmosis effluent meets the GB16171-2012 standard.

[0035] As a further technical solution, the dosage of the pelletized hardness and fluoride removal reactor is determined based on the hardness, pH, alkalinity and removal rate of the water to be treated, so as to achieve directional removal of total hardness and fluoride ions.

[0036] As a further technical solution, the process integrates a full-process automated monitoring system, which can be used to individually design the process flow according to the influent water quality, with an overall compliance rate of ≥97%.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention forms a full-process and efficient purification capability for coal chemical wastewater (such as semi-coke wastewater) through the system integration and synergy of the four major process units of "cascade physicochemical treatment - phenol-ammonia recovery - biochemical enhanced treatment - deep treatment". Its technical advantages are as follows:

[0039] 1. Cascade physicochemical treatment unit: precise oil removal to ensure stability of subsequent treatment

[0040] Primary oil-water separation: Rapidly remove floating oil and dispersed oil through a physical oil separator, reducing the risk of direct blockage of subsequent equipment by oil.

[0041] Secondary chemical demulsification: Utilizing the molecular structure of amphiphilic emulsifiers (such as fatty amine polyoxyethylene ethers), this method destroys the interfacial membrane of the emulsified oil, causing the oil droplets to coalesce and settle, achieving an oil removal rate of 90%. This step solves the problem of emulsified oil being difficult to treat with conventional physical methods.

[0042] Three-stage new material for deep oil removal: Utilizing a super-hydrophobic and oleophilic polyurethane modified with methyltrichlorosilane, this material efficiently captures ultra-finely dispersed and semi-emulsified oils through the lipophilic adsorption of the hydrophobic methyl groups on its surface. The modified material has an oil absorption capacity of 20 times its own weight and is reusable through extrusion, avoiding the secondary contamination issues associated with traditional adsorbents.

[0043] The three-stage process purifies layer by layer from "macro floating oil → emulsified oil → ultrafine oil", eventually reducing the oil content to below 20 mg / L, completely solving the problems of equipment coking and microbial poisoning caused by oil, and creating suitable conditions for subsequent biochemical treatment.

[0044] 2. Phenol-ammonia recovery unit: dual goals of resource recovery and toxicity reduction

[0045] Dual-tower low-temperature, low-pressure micro-evaporation: Through deacidification in the first tower and negative-pressure ammonia removal in the second tower, this process utilizes the principle of vapor-liquid equilibrium to efficiently separate ammonia nitrogen from phenols, while simultaneously recovering ammonia water and crude phenol. This process reduces ammonia nitrogen concentration from 3,000 mg / L to below 500 mg / L and total phenols from 8,000 mg / L to below 800 mg / L, while maintaining low energy consumption, significantly reducing wastewater toxicity.

[0046] Extraction and dephenolization: Using highly efficient extractants such as N,N-bis(1-methylheptyl)acetamide, the phenols are transferred to the extractant by taking advantage of the difference in the partition coefficients of phenols between the aqueous and organic phases (partition coefficient > 10). The extractant can be recycled after distillation, achieving a phenol recovery rate exceeding 95%, achieving resourceful utilization of pollutants.

[0047] Physical and chemical dephenolization and ammonia removal are carried out simultaneously with resource recovery, which not only reduces the toxic effects of wastewater on microorganisms (such as phenols inhibiting microbial enzyme activity), but also reduces treatment costs through by-product recovery, saving reagent costs compared to traditional chemical precipitation methods.

[0048] 3. Biochemical Enhanced Treatment Unit: Technological Breakthrough in Efficient Degradation and Energy-Saving Denitrification

[0049] High-energy anaerobic: Add composite fungal engineered bacteria (external live bacteria tank to maintain activity), and use the directional decomposition enzyme system to convert polycyclic aromatic hydrocarbons, heterocyclic compounds and other difficult-to-degrade organic matter into low molecular substances (such as fatty acids). A COD removal rate of 50-65% can be achieved after staying for 2-3 days, significantly improving the biodegradability of wastewater.

[0050] High-load aeration tank: Through dissolved oxygen control and long residence time, aerobic microorganisms are used to further degrade organic matter, with a COD removal rate of more than 70%, creating a low-load environment for subsequent denitrification.

[0051] Anaerobic ammonium oxidation: Utilize the metabolic characteristics of autotrophic anaerobic ammonium oxidizing bacteria to convert ammonia nitrogen (NH4 + ) and nitrite (NO2 - ) is directly converted into nitrogen (N2), with a denitrification rate of >80%. This reaction does not require an external carbon source, saving 60% of oxygen supply and 100% of carbon source input compared to traditional nitrification-denitrification processes, significantly reducing energy consumption.

[0052] Multi-stage A / O system: Through built-in live bacteria tanks and engineered bacteria enhancement, simultaneous nitrification and denitrification are achieved in an alternating aerobic-anoxic environment. The aerobic stage degrades COD, while the anoxic stage removes total nitrogen. The ammonia nitrogen removal rate is >90%, and the total nitrogen removal rate is >85%, solving the problem of low denitrification efficiency of traditional A / O systems.

[0053] The four-step process of "anaerobic hydrolysis and acidification → aerobic organic matter degradation → autotrophic denitrification → biologically enhanced deep denitrification" optimizes the entire chain from organic matter decomposition to nitrogen conversion. The targeted addition of engineered bacteria (such as complex fungi and anaerobic ammonium-oxidizing bacteria) addresses the industry's challenges of microbial susceptibility to toxicity and low activity, increasing the system's resistance to shock loads by over 50%.

[0054] 4. Deep processing unit: ensuring reuse and long-term operation

[0055] Fluidized bed Fenton: through Fe 2+ It reacts with H2O2 to generate hydroxyl radicals, which oxidize and decompose the refractory organic matter (such as polycyclic aromatic hydrocarbon derivatives) remaining in the biochemical tail water. The gas-solid-liquid three-phase fluidization design in the reactor increases the reagent utilization rate to over 90%, and the COD removal rate is stabilized at over 50%.

[0056] Pelletization for Hardness and Fluoride Removal: Crystallization agents (such as calcium hydroxide and sodium fluoride) are added to the PCR reactor to induce the growth of calcium carbonate and calcium fluoride crystals on the surface of the pellet seeds, achieving targeted removal of total hardness and fluoride ions. This process avoids the large sludge production associated with traditional precipitation methods, reducing sludge production by over 70%.

[0057] Membrane system (multi-media filtration + ultrafiltration + reverse osmosis): further removes suspended matter and ionic pollutants through physical interception. The COD of reverse osmosis effluent is less than 30mg / L and ammonia nitrogen is less than 5mg / L, fully meeting the GB16171-2012 emission standards and industrial reuse water requirements.

[0058] The combination of "oxidation destruction → crystallization removal → membrane fine treatment" solves the problems of easy scaling and short life of membrane systems in traditional processes (the membrane cleaning cycle is extended from 2 weeks to more than 3 months). At the same time, it realizes the recycling of water resources, with a reuse rate of more than 70%, saving the company about 20 yuan / ton in fresh water costs.

[0059] 5. Advantages of full-process system integration

[0060] Resource recovery: The recovery value of ammonia and crude phenol can cover part of the operating costs;

[0061] Energy consumption optimization: anaerobic ammonia oxidation, high-energy anaerobic and other processes have significantly reduced comprehensive energy consumption compared to traditional technologies;

[0062] Sludge reduction: Pelletization process and bio-augmentation technology significantly reduce the amount of sludge generated and reduce the cost of hazardous waste treatment.

[0063] Industry adaptability: It is suitable for semi-coke wastewater, coal gasification wastewater and other high-phenol, high-ammonia nitrogen, high-oil coal chemical wastewater, and the treatment scale can be from 50m 3 / d to 10000m 3 / d Flexible adaptation has promoted the standardization and integration of coal chemical wastewater treatment technology.

[0064] In summary, the present invention forms a full-chain solution of "efficient oil removal - toxicity reduction - bio-augmentation - deep purification - resource recycling" through functional coupling and technological innovation of each process unit, which significantly improves the efficiency, stability and economy of coal chemical wastewater treatment, and has significant environmental, economic and social benefits.

[0065] Figures in the specification

[0066] Figure 1 This is the process flow chart of semi-coal wastewater treatment;

[0067] Figure 2 This is a pH diagram of semi-coke wastewater after treatment by this process. The dotted line in the figure is the national standard qualified line; each step is tested 10 times to reduce errors and ensure the accuracy of the data. The annotations of the steps are as follows: 1. Pre-treatment water inlet, 2. Phenol ammonia recovery system (V23), 3. Phenol ammonia recovery water (E15), 4. Multi-function tank, 5. High-energy anaerobic, 6. A / O tank water inlet, 7. Secondary sedimentation tank effluent, 8. Fluidized bed Fenton + high-density sedimentation tank, 9. Cloud tank effluent, 10. Ultrafiltration and reverse osmosis;

[0068] Figure 3 This is a schematic diagram of the ammonia nitrogen content in steps 1 to 10 of the semi-coke wastewater after it has been treated by this process. The dotted line in the figure is the national standard qualified line; each step is tested 10 times to reduce errors and ensure the accuracy of the data. The annotations of the steps are as follows: 1. Pretreatment water inlet, 2. Phenol ammonia recovery system (V23), 3. Phenol ammonia recovery water (E15), 4. Multi-function tank, 5. High-energy anaerobic, 6. A / O tank water inlet, 7. Secondary sedimentation tank effluent, 8. Fluidized bed Fenton + high-density sedimentation tank, 9. Cloud tank effluent, 10. Ultrafiltration and reverse osmosis;

[0069] Figure 4 This is a schematic diagram of the COD content of semi-coke wastewater in steps 1 to 10 after the process. The dotted line in the figure is the national standard qualified line; each step is tested 10 times to reduce errors and ensure the accuracy of the data. The annotations of the steps are as follows: 1. Pre-treatment water inlet, 2. Phenol ammonia recovery system (V23), 3. Phenol ammonia recovery water (E15), 4. Multi-function tank, 5. High-energy anaerobic, 6. A / O tank water inlet, 7. Secondary sedimentation tank effluent, 8. Fluidized bed Fenton + high-density sedimentation tank, 9. Cloud tank effluent, 10. Ultrafiltration and reverse osmosis;

[0070] Figure 5 This is a schematic diagram of the oil content in the water in steps 1 to 10 after the semi-coke wastewater is treated by this process. The dotted line in the figure is the national standard qualified line; each step is tested 10 times to reduce errors and ensure the accuracy of the data. The annotations of the steps are as follows: 1. Pre-treatment water inlet, 2. Phenol ammonia recovery system (V23), 3. Phenol ammonia recovery water (E15), 4. Multi-function tank, 5. High-energy anaerobic, 6. A / O tank water inlet, 7. Secondary sedimentation tank effluent, 8. Fluidized bed Fenton + high-density sedimentation tank, 9. Cloud tank effluent, 10. Ultrafiltration and reverse osmosis;

[0071] Figure 6 This is a schematic diagram of the total phenol content in steps 1 to 10 of the semi-coke wastewater after it has been treated by this process. The dotted line in the figure is the national standard qualified line; each step was tested 10 times to reduce errors and ensure the accuracy of the data. The annotations of the steps are as follows: 1. Pre-treatment water inlet, 2. Phenol ammonia recovery system (V23), 3. Phenol ammonia recovery water (E15), 4. Multi-function tank, 5. High-energy anaerobic, 6. A / O tank water inlet, 7. Secondary sedimentation tank effluent, 8. Fluidized bed Fenton + high-density sedimentation tank, 9. Cloud tank effluent, 10. Ultrafiltration and reverse osmosis;

[0072] Figure 7This is a schematic diagram of the suspended solids content in steps 1 to 10 of the semi-coke wastewater after treatment through this process. The dotted line in the figure marks the national standard pass line; each step was tested 10 times to reduce errors and ensure data accuracy. The annotations of the steps are as follows: 1. Pretreatment water inlet, 2. Phenol ammonia recovery system (V23), 3. Phenol ammonia recovery water (E15), 4. Multi-function tank, 5. High-energy anaerobic, 6. A / O tank water inlet, 7. Secondary sedimentation tank effluent, 8. Fluidized bed Fenton + high-density sedimentation tank, 9. Cloud tank effluent, 10. Ultrafiltration and reverse osmosis. DETAILED DESCRIPTION

[0073] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0074] A biochemical treatment process for coal chemical wastewater based on the combination of "cascaded physical and chemical treatment - biochemical enhanced treatment - deep treatment" specifically includes:

[0075] 1. Step-by-step physicochemical treatment (three-step gradient physicochemical degreasing)

[0076] Wastewater oil removal is completed in three steps

[0077] The first step: oil-water separation - oil-water separation is carried out through conventional oil removal equipment to first remove floating oil and dispersed oil;

[0078] The second step: chemical demulsification - add amphiphilic molecular emulsifiers, usually fatty amine polyoxyethylene ether, polyoxypropylene ether, organic amine, etc. The dosage is about 300-3000mg / L, and the emulsified oil is separated by centrifugation, and the oil removal rate can reach 90%.

[0079] The third step: Deep Oil Removal Using New Materials—Developing a novel hydrophobic adsorbent, polyurethane, to filter and adsorb ultrafinely dispersed and semi-emulsified oils. The oil removal adsorbent utilizes a super-hydrophobic and oleophilic polyurethane material. Specifically, a polyurethane matrix with a pore size of 200-400μm is modified with methyltrichlorosilane to achieve selective separation of oil-water mixtures and rapid adsorption and recovery of oils. The oil absorption capacity can reach 20 times its own weight. Extrusion and deformation of the material allow for oil separation and recovery, as well as the reuse of the hydrophobic and oleophilic material. After oil removal, the oil content in the wastewater is reduced to below 20mg / L.

[0080] The preparation method of super hydrophobic and oleophilic polyurethane material is as follows: a polyurethane matrix with a pore size of 200-400 μm is ultrasonically cleaned with an ethanol-acetone mixture for 30-40 minutes, dried at 72-80°C for 3-4 hours, immersed in a methyltrichlorosilane hydrolyzate with a pH of 2-3, and oscillated at room temperature for 3-4 hours. After washing with deionized water, the matrix is ​​vacuum dried at 55-70°C and -0.06 to -0.08 MPa for 4-6 hours.

[0081] Phenol and ammonia recovery (phenol removal and ammonia removal)

[0082] To remove phenol and ammonia, hydrochloric acid, sulfuric acid, and other reagents are first added to adjust the pH to 6-9. A dual-tower, two-stage, low-temperature, low-pressure micro-evaporation process is then employed to remove phenol and ammonia at a low cost, recovering ammonia and crude phenol. The primary tower performs preheating and deacidification, while the secondary tower performs deamination, achieving wastewater deammoniation and ammonia recovery. The secondary tower then performs dephenolization to reduce the phenol concentration in the wastewater. After preheating, the wastewater is heated to 90-110°C before undergoing deacidification to remove acidic gases. Deamination is then performed under negative pressure (vacuum level -0.08 MPa).

[0083] Subsequently, extractive dephenolization is performed, primarily relying on the difference in solubility of phenolic compounds between water and the extractant. This transfers the phenols from the phenolic wastewater into the extractant, achieving dephenolization. The extractant must possess a high partition coefficient, a large difference in relative gravity between the two, resistance to emulsification, low solubility in water, low vapor pressure, ease of stripping and regeneration, non-corrosiveness to equipment, low toxicity, a high ignition temperature, and good chemical stability. Common extractants include N,N-bis(1-methylheptyl)acetamide and tributyl phosphate. The extractant is then regenerated through distillation and crystallization, enabling the recovery of phenolic compounds and the reuse of the extractant. After recovery, the wastewater's ammonia nitrogen concentration drops below 500 mg / L, and the total phenol concentration drops below 800 mg / L.

[0084] 3. Biochemical enhanced treatment (high-energy anaerobic, high-load aeration, anaerobic ammonium oxidation, multi-stage A / O)

[0085] 3.1 High-energy anaerobic

[0086] In a conventional anaerobic reactor, activated engineered microbial strains (with an external live bacteria tank) are added. These complex fungi, composed of diverse biochemical species with the ability to specifically decompose organic matter, effectively degrade a wide range of organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Highly active anaerobic engineered microorganisms and growth promoters decompose high-concentration organic matter in the wastewater into low-molecular-weight organic matter. With a residence time of 2-3 days, the organic matter removal rate reaches over 50-65%.

[0087] 3.2 High-load aeration tank

[0088] The wastewater is further degraded in conventional aeration tanks, with a dissolved oxygen concentration of 2-3 mg / L, a residence time of 8-12 hours, and a COD removal rate of over 70%.

[0089] 3.3 Anaerobic ammonium oxidation

[0090] In a conventional anaerobic ammonium oxidation reactor, nitrite reacts with ammonia nitrogen under anaerobic conditions to produce nitrogen gas. The culture conditions of anaerobic ammonium oxidizing bacteria are: temperature controlled at about 36℃, pH controlled at about 7.8, NH4 + About 70mg / L, NO2 - The dissolved oxygen concentration in the reactor is controlled below 0.5 mg / L, and some ammonia nitrogen is oxidized to nitrite. Anaerobic ammonium-oxidizing bacteria then react with the ammonia nitrogen and nitrite nitrogen to form nitrogen gas, which is then discharged, achieving wastewater denitrification with a denitrification rate exceeding 80%. This process uses 60% less oxygen than full-process nitrification. Anaerobic ammonium-oxidizing bacteria are autotrophic and require no organic matter. Using ammonia as an electron donor, they eliminate the carbon source required in traditional denitrification processes.

[0091] 3.4 Multi-level A / O

[0092] The bio-augmented multi-stage A / O system significantly improves biodegradation efficiency (compared to conventional biochemical systems) by integrating live bacteria tanks and dosing engineered bacteria within conventional biochemical tanks. This system also achieves deep removal of COD, ammonia nitrogen, and total nitrogen from wastewater through alternating aerobic and anoxic environments within the biochemical tanks. The residence time for each A / O unit is 4-6 hours in the aerobic phase and 2-3 hours in the anoxic phase, respectively. COD removal rates exceed 60%, and ammonia nitrogen removal rates exceed 90%.

[0093] 4. Advanced treatment (pelletization for hardness and fluoride removal, membrane system)

[0094] 4.1 Fluidized Bed Fenton

[0095] The fluidized bed Fenton system uses ferrous ions and H2O2 to produce highly oxidizing hydroxyl radicals to oxidize and decompose the difficult-to-degrade organic matter remaining in the wastewater. Through hydraulic optimization inside the reactor and efficient fluidization of gas-solid-liquid three-phase materials, full utilization of the reagents is achieved, maintaining a COD removal rate of more than 50%.

[0096] 4.2 Pelletization for hardness and fluoride removal

[0097] A crystallization agent is added to a conventional pellet reactor. The pellet seeds come into full contact with water under fluidization. Hardness ions in the water form crystals on the pellet seeds and grow, eventually forming larger, mature pellets that are discharged from the PCR reactor. This removes total hardness and fluoride ions from the water, protecting the membrane system's influent quality and extending the membrane's service life. The dosage for the PCR pellet crystallization reactor is determined based on the hardness, pH, alkalinity, and removal rate of the water being treated.

[0098] 4.3 Membrane system

[0099] The effluent from the pellet reactor flows by gravity into the multi-media filter for pretreatment and then into the ultrafiltration device. The effluent from the ultrafiltration device enters the reverse osmosis device for concentration. The effluent quality of the reverse osmosis device meets the discharge or reuse standards.

[0100] The following are specific embodiments:

[0101] Example 1: Treatment of blue carbon wastewater

[0102] The semi-coke wastewater treated in this example originated from a semi-coke production enterprise and primarily consisted of phenol-ammonia recovery water and tar hydrogenation purified water. The influent quality of the wastewater was: pH 6-9, COD <6000mg / L, ammonia nitrogen <300mg / L, oil <200mg / L, and total phenols <800mg / L. The effluent quality was: pH 6-9, COD <50mg / L, ammonia nitrogen <5mg / L, and SS <20mg / L.

[0103] The blue carbon wastewater treatment process used in this embodiment is as follows Figure 1 As shown:

[0104] Including: lignite wastewater oil removal → phenol ammonia recovery → high-energy anaerobic → high-load aeration tank → anaerobic ammonia oxidation → multi-stage A / O → fluidized bed Fenton → cloud tank → pelletization hardness removal and fluoride removal → membrane system.

[0105] Step 1: Three-stage oil removal of semi-coke wastewater: First stage: oil-water separation - oil-water separation is carried out through the oil removal device to first remove floating oil and dispersed oil; Second stage: chemical demulsification - add amphiphilic molecular emulsifier and centrifuge to separate the emulsified oil; Third stage: new material deep oil removal - super hydrophobic and oleophilic polyurethane material, filter and adsorb ultra-fine dispersed and ultra-fine semi-emulsified oils.

[0106] The preparation method of super hydrophobic and oleophilic polyurethane material is as follows: the polyurethane matrix with a pore size of 200 μm is ultrasonically cleaned with an ethanol-acetone mixture for 30 minutes, dried at 72°C for 3 hours, immersed in a pH 2 methyltrichlorosilane hydrolyzate, and reacted at room temperature for 3 hours. After washing with deionized water, it is vacuum dried at 55°C and -0.06 MPa for 4 hours.

[0107] Step 2: Phenol and ammonia recovery: The wastewater pH is adjusted to 6-9. It undergoes two-stage, low-temperature, low-pressure micro-evaporation in a dual-tower system to cost-effectively remove phenols and ammonia. Ammonia and crude phenol are then recovered. Extractive dephenolation reduces the phenol and ammonia content in the wastewater, creating favorable conditions for subsequent biochemical treatment.

[0108] Step 3: High-energy anaerobic treatment: After oil removal and phenol-ammonia recovery, the wastewater enters a high-energy anaerobic reactor. Within the reactor, activated engineered microbial strains are added, along with an external live bacteria tank to ensure microbial activity and stability, resulting in efficient degradation of organic matter. Highly active anaerobic engineered microorganisms and growth promoters decompose high-concentration organic matter in the wastewater into low-molecular-weight organic matter.

[0109] Step 4. High-load aeration tank: The wastewater after anaerobically treated flows into the high-load aeration tank. Under the action of aerobic microorganisms, COD in the wastewater is further removed, creating conditions for the subsequent anaerobic ammonium oxidation reaction.

[0110] Step 5: Anaerobic ammonium oxidation: In the anaerobic ammonium oxidation reactor, nitrite and ammonia nitrogen react under anaerobic conditions to produce nitrogen gas. The dissolved oxygen concentration in the reactor is controlled below 0.5 mg / L, partially oxidizing the ammonia nitrogen to nitrite. The ammonia nitrogen and nitrite nitrogen then react with anaerobic ammonium-oxidizing bacteria to produce nitrogen gas, which is then discharged, achieving wastewater denitrification.

[0111] Step 6: Multi-stage A / O: The bio-augmented multi-stage A / O system utilizes a built-in live bacteria tank and the addition of engineered bacterial strains within the biochemical pool. This system, coupled with an external live bacteria tank, ensures microbial activity and bacterial stability, significantly improving biochemical degradation efficiency (compared to conventional biochemical systems). The alternating aerobic and anoxic environments within the biochemical pool deeply remove COD, ammonia nitrogen, and total nitrogen from the wastewater.

[0112] Step 7. Fluidized bed Fenton: The fluidized bed Fenton system uses ferrous ions and H2O2 to produce highly oxidizing hydroxyl radicals to oxidize and decompose the difficult-to-degrade organic matter remaining in the wastewater. Through hydraulic optimization inside the reactor and efficient fluidization of gas-solid-liquid three-phase materials, full utilization of the reagents is achieved to ensure COD removal rate.

[0113] Step 8. Cloud tank: The wastewater passes through a series of cloud tanks to further remove excess COD and ammonia nitrogen.

[0114] Step 9. Pelletization for hardness and fluoride removal: Crystallization agent is added to the pellet reactor. The pellet seeds are in full contact with water in a fluidized state. The hardness ions in the water form crystals and grow on the surface of the pellet seeds. Eventually, mature pellets with larger particle size are formed and discharged from the PCR reactor, thereby removing the total hardness and fluoride ions in the water, protecting the inlet water quality of the membrane system, and extending the service life of the membrane.

[0115] Step 10, membrane system: the effluent from the pellet reactor flows into the multi-media filter for pretreatment and then enters the ultrafiltration device. The effluent from the ultrafiltration device enters the reverse osmosis device for concentration. The effluent quality of the reverse osmosis device meets the discharge or reuse standards.

[0116] Example 1 shows the effect of wastewater treatment. Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 As shown in the figure, the semi-coke wastewater treated through the above process was tested at each stage for pH, ammonia nitrogen (mg / L), COD (mg / L), oil in water (mg / L), total phenols (mg / L), and suspended solids (mg / L). The effluent quality after this process reached the following indicators: pH 7.0-8.5, COD <30mg / L, ammonia nitrogen <5mg / L, total phenols <1.0mg / L, SS <20mg / L, etc. The results showed that all indicators met the requirements of GB16171-2012 "Pollutant Emission Standard for Coking Chemical Industry", with an overall compliance rate of approximately 97.0%.

[0117] Example 2

[0118] The difference from Example 1 is that the preparation method of the super hydrophobic and oleophilic polyurethane material is as follows: the polyurethane matrix with a pore size of 250 μm is ultrasonically cleaned with an ethanol-acetone mixture for 35 minutes, dried at 76°C for 3.5 hours, immersed in a methyltrichlorosilane hydrolyzate with a pH of 2.4, and reacted at room temperature for 3.5 hours. After washing with deionized water, it is vacuum dried at 60°C and -0.07 MPa for 5 hours.

[0119] After the semi-coke wastewater has been treated through the aforementioned process, water quality testing is conducted at each stage, including pH, ammonia nitrogen (mg / L), COD (mg / L), oil in water (mg / L), total phenols (mg / L), and suspended solids (mg / L). The effluent quality achieved through this process meets the following indicators: pH 7.0-8.5, COD <30mg / L, ammonia nitrogen <5mg / L, total phenols <1.0mg / L, and SS <20mg / L. The results show that all indicators meet the requirements of GB16171-2012, "Pollutant Emission Standards for the Coking Chemical Industry," with an overall compliance rate of approximately 97.2%.

[0120] Example 3

[0121] The difference from Example 1 is that the preparation method of the super hydrophobic and oleophilic polyurethane material is as follows: the polyurethane matrix with a pore size of 400 μm is ultrasonically cleaned with an ethanol-acetone mixture for 40 minutes, dried at 80°C for 4 hours, immersed in a pH 3 methyltrichlorosilane hydrolyzate, and reacted at room temperature for 4 hours. After washing with deionized water, it is vacuum dried at 70°C and -0.08 MPa for 6 hours.

[0122] After the semi-coke wastewater has been treated through the aforementioned process, water quality is tested at each stage, including pH, ammonia nitrogen (mg / L), COD (mg / L), oil in water (mg / L), total phenols (mg / L), and suspended solids (mg / L). The effluent quality achieved through this process meets the following indicators: pH 7.0-8.5, COD <30mg / L, ammonia nitrogen <5mg / L, total phenols <1.0mg / L, and SS <20mg / L. The results show that all indicators meet the requirements of GB16171-2012, "Pollutant Emission Standards for the Coking Chemical Industry," with an overall compliance rate of approximately 97.5%.

[0123] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. The preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification.

Claims

1. A biochemical treatment process for coal chemical wastewater, characterized in that: It includes sequentially connected cascade physicochemical treatment units, phenol-ammonia recovery units, biochemical enhanced treatment units and deep treatment units, among which: The cascade physicochemical treatment unit is used for three-stage gradient oil removal; The phenol-ammonia recovery unit is used for removing phenol and ammonia and recovering resources; The biochemical enhancement treatment unit is used for efficiently degrading organic matter and removing nitrogen; The deep treatment unit is used to remove refractory pollutants, hardness and fluoride ions.

2. A biochemical treatment process for coal chemical wastewater according to claim 1, characterized in that: The three-stage oil removal of the cascade physicochemical treatment unit includes: (1) Primary oil-water separation by removing floating oil and dispersed oil through conventional oil removal equipment; (2) adding 300-3000 mg / L of amphiphilic emulsifier and centrifuging the emulsified oil for secondary chemical demulsification; The amphiphilic emulsifier is fatty amine polyoxyethylene ether, polyoxypropylene ether or organic amine; (3) A three-stage new material for deep oil removal using methyltrichlorosilane-modified super-hydrophobic and oleophilic polyurethane material with a pore size of 200-400 μm to adsorb ultrafine oils, with the final oil content ≤20 mg / L.

3. A biochemical treatment process for coal chemical wastewater according to claim 2, characterized in that: The methyltrichlorosilane-modified super-hydrophobic and oleophilic polyurethane material is obtained by using polyurethane with a pore size of 200-400 μm as a matrix and modifying the polyurethane with methyltrichlorosilane. The oil absorption capacity of methyltrichlorosilane-modified super-hydrophobic and oleophilic polyurethane material is 20 times its own weight, and oil separation and recovery and material reuse can be achieved through extrusion deformation.

4. A biochemical treatment process for coal chemical wastewater according to claim 3, characterized in that: The preparation method of the super-hydrophobic and oleophilic polyurethane material is as follows: a polyurethane matrix with a pore size of 200-400 μm is ultrasonically cleaned with an ethanol-acetone mixture for 30-40 minutes, dried at 72-80°C for 3-4 hours, immersed in a methyltrichlorosilane hydrolyzate with a pH of 2-3, and reacted at room temperature for 3-4 hours under oscillation. After washing with deionized water, the matrix is ​​vacuum dried at 55-70°C and -0.06 to -0.08 MPa for 4-6 hours. The methyltrichlorosilane hydrolyzate is prepared by mixing methyltrichlorosilane, deionized water and ethanol in a molar ratio of 1:3-5:5-8.

5. A biochemical treatment process for coal chemical wastewater according to claim 1, characterized in that: The phenol ammonia recovery unit comprises: Double-tower, two-stage, low-temperature, low-pressure micro-evaporation module: adjusts the wastewater pH to 6-9, preheats and deacidifies at 90-110°C in the first tower, and deammonifies at -0.08MPa negative pressure in the second tower, recovering ammonia water and crude phenol to achieve ammonia nitrogen ≤500mg / L and total phenol ≤800mg / L; Extraction and dephenolization module: N, N-bis (1-methylheptyl) acetamide or tributyl phosphate is used as the extractant, phenols are transferred by difference in distribution coefficient, and the extractant is regenerated by distillation / crystallization.

6. A biochemical treatment process for coal chemical wastewater according to claim 1, characterized in that: The biochemical enhancement treatment unit comprises: High-energy anaerobic reactor: Add composite fungal engineering bacteria maintained in an external live bacteria tank, with a residence time of 2-3 days and a COD removal rate of 50-65%; High-load aeration tank: dissolved oxygen 2-3 mg / L, residence time 8-12 hours, COD removal rate ≥ 70%; Anaerobic ammonium oxidation reactor: control temperature at 36±1℃, pH7.8±0.2, dissolved oxygen ≤0.5mg / L, NH4 + Concentration 70±10mg / L, NO2 - Concentration 90±10mg / L, denitrification rate ≥80%; Multi-stage A / O system: built-in live bacteria tank and dosing of engineered bacteria, aerobic section stay 4-6 hours, anoxic section stay 2-3 hours, COD removal rate ≥ 60%, ammonia nitrogen removal rate ≥ 90%.

7. A biochemical treatment process for coal chemical wastewater according to claim 6, characterized in that: The anaerobic ammonium oxidation reactor is an autotrophic bacteria reaction system that does not require an external carbon source and saves 60% of oxygen supply compared to traditional nitrification processes.

8. A biochemical treatment process for coal chemical wastewater according to claim 1, characterized in that: The depth processing unit includes: Fluidized bed Fenton reactor: using Fe 2+ It generates hydroxyl radicals with H2O2 and achieves COD removal rate ≥ 50% through gas-solid-liquid three-phase fluidization; Pelletized hardness and fluoride removal reactor (PCR): Add crystallization reagents to make hardness ions and F- crystallize on the surface of pellet seeds, protecting the water quality of the membrane system; Membrane system: It includes multi-media filter, ultrafiltration device and reverse osmosis device in sequence. The reverse osmosis effluent meets the GB16171-2012 standard.

9. A biochemical treatment process for coal chemical wastewater according to claim 8, characterized in that: The dosage of the pelletized hardness and fluoride removal reactor is determined by measuring and calculating the hardness, pH, alkalinity and removal rate of the water to be treated, so as to achieve the directional removal of total hardness and fluoride ions.

10. A biochemical treatment process for coal chemical wastewater according to any one of claims 1 to 9, characterized in that: The process integrates a full-process automated monitoring system, which can be used to individually design the process flow according to the influent water quality, with an overall compliance rate of ≥97%.

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