Multi-stage treatment process for salt-containing wastewater in petrochemical industry

Abstract

The invention provides a multi-stage treatment process for salt-containing wastewater in the petrochemical industry, and relates to the field of multi-stage treatment of the salt-containing wastewater in the petrochemical industry. According to the multi-stage treatment process for the salt-containing wastewater in the petrochemical industry, reverse osmosis concentrated water is adopted, and in the first step, the reverse osmosis concentrated water is subjected to multi-technology synergistic efficient catalytic oxidation; according to the multi-stage treatment process for the salt-containing wastewater in the petrochemical industry, aiming at the characteristics of reverse osmosis membrane concentrated liquor, a chemical oxidation and biological coupling synchronous decarburization and denitrification process combining multi-technology synergistic efficient catalytic oxidation, a high-salt biofilm process and efficient low-consumption catalytic ozonation is formed, so that the biodegradability of the wastewater is improved; the biochemical system adopts a high-salt biofilm method to enhance the denitrification effect; and the advanced treatment adopts a high-efficiency low-consumption catalytic oxidation ozone technology with high pertinence to low-concentration COD (Chemical Oxygen Demand). The process technology is advanced, green and efficient, efficient treatment of the wastewater can be achieved, the wastewater treatment cost and energy consumption are reduced, and secondary pollution is avoided.

Description

Technical Field

[0001] This invention relates to the field of multi-stage treatment technology for petrochemical saline wastewater, specifically a multi-stage treatment process for saline wastewater in the petrochemical industry. Background Technology

[0002] Oil and gas extraction and petroleum refining processes consume a large amount of water resources and generate a large amount of high-salt organic wastewater. Wastewater treatment and resource reuse are important means to solve the contradiction between water supply and demand in the petroleum and petrochemical industry. A large amount of water resources need to be supplemented during oil and gas extraction and petroleum refining. Due to the complex composition of crude oil and the increasingly refined extraction, refining and processing technologies, the composition of associated wastewater pollution is becoming more and more complex.

[0003] Petroleum and petrochemical wastewater mainly includes oil and gas field wastewater and refining and chemical wastewater. Among them, oil and gas field wastewater mainly comes from drilling mud, completion fluid, produced water, and acid / pressure flowback fluid generated during the oil and gas field development and production process (drilling, well completion, well washing, downhole operations, oil and gas production, etc.).

[0004] Refining and chemical wastewater mainly originates from the crude oil refining process (atmospheric and vacuum distillation, catalytic cracking, reforming, hydrogenation, delayed coking, and auxiliary processes), including desalination wastewater, desulfurization and denitrification wastewater, alkali residue neutralization water, cooling water, and wastewater discharged from circulating water systems. Existing treatment processes in the petrochemical industry are not effective at completely removing pollutants such as benzene and phenols from saline wastewater, and their salt treatment effect is also insufficient. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-stage treatment process for saline wastewater in the petrochemical industry, which solves the problems mentioned in the background art.

[0006] Technical solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a multi-stage treatment process for saline wastewater in the petrochemical industry, comprising: first, reverse osmosis concentrate is subjected to efficient catalytic oxidation using multiple technologies; second, high-salt A / O biofilm treatment is employed; third, the treated reverse osmosis concentrate is subjected to coagulation and sedimentation; fourth, oxidation is carried out using a high-efficiency, low-consumption catalytic ozone device; and fifth, the final effluent is obtained.

[0008] Furthermore, addressing the issue of poor biodegradability caused by residual undegraded organic matter and microbial metabolites such as proteins, polysaccharides, and humic acids in wastewater, a "multi-technology synergistic high-efficiency catalytic oxidation" pretreatment technology is employed. This technology breaks down recalcitrant substances in the membrane concentrate, decomposing them into easily biodegradable substances, improving the wastewater's B / C ratio, and reducing its biotoxicity before it enters the subsequent biochemical system. The characteristics of multi-technology synergistic high-efficiency catalytic oxidation are: based on the composition of pollutants in the wastewater, multi-technology synergistic catalytic technology is used. Under different reaction conditions and operating parameters, it fully utilizes the oxidation characteristics of different oxidizing groups (such as hydroxyl radicals and oxygen radicals) to induce rapid chemical reactions (such as addition and substitution reactions) between specific oxidizing groups and pollutant functional groups. This achieves highly efficient and selective degradation of chromogenic groups such as C=C and C=O, as well as highly toxic and recalcitrant substances such as aromatics and heterocyclic compounds. In some stages of the reaction, process control avoids the problem of poor selectivity of hydroxyl radical (·OH) oxidation for target pollutants in the wastewater, while also avoiding competition between oxidants, effectively improving the efficiency of the oxidation reaction. In another stage of the oxidation reaction, the high oxidation potential of hydroxyl radicals (·OH) is fully utilized to react with organic matter in wastewater. The organic free radicals generated in the reaction can continue to participate in the chain reaction of hydroxyl radicals, or after generating organic peroxide free radicals, they can undergo further oxidative decomposition reactions until they are degraded into the final products CO2 and H2O.

[0009] Furthermore, the aforementioned multi-technology synergistic high-efficiency catalytic oxidation technology employs multi-metal doped high-efficiency catalysts, multi-stage circulating tower reactors, and specially designed distributors, with the following characteristics:

[0010] (1) Salt-resistant multi-metal doped catalyst: This catalyst is a metal catalyst composed of multiple metals, characterized by its porous structure, high specific surface area, numerous active sites, low dosage, resistance to deactivation, and long lifespan (over 2 years). The addition of the catalyst greatly enhances the ability of the oxidant to generate hydroxyl radicals (·OH) on the catalyst surface, achieving an oxidant utilization rate of over 95%, which is several times higher than that of general catalytic oxidation. This technology is highly effective for high-salt, recalcitrant organic matter and has a high removal rate for coloring substances such as C=C and C=O in wastewater, significantly removing color and recalcitrant substances. Simultaneously, the catalyst exhibits a micro-expansion state within the tower, solving the catalyst caking problem and facilitating the treatment of wastewater with high hardness.

[0011] (2) Multi-circulation tower reactor enhances mass transfer efficiency and improves utilization rate.

[0012] The multi-circulation tower reactor employs a tower structure with a high height-to-diameter ratio, where gas and liquid contact in a counter-current manner. A special gas distributor generates high-density microbubbles (diameter less than 20 micrometers). The tower is equipped with functional catalytic packing, and through multi-circulation, the bubble rise velocity is significantly reduced (to only about 1% of that of bubbles from ordinary aeration discs). The bubble residence time in water is extended by tens of times, greatly improving the contact area and efficiency between the gas and organic matter and catalyst in the water, enhancing gas-liquid mass transfer, and effectively prolonging the gas-liquid contact time.

[0013] (3) Specially designed distributor with significant anti-clogging effect

[0014] It adopts a specially designed aeration disc with uniform pore size, high porosity, and stable pore shape; the air distribution plate has small pores, which can fully cut the oxidant into high-density microbubbles, resulting in good mixing effect; the bubbles diffuse evenly, and the gas-liquid interface area is large; the aeration resistance is low, the separation and purification efficiency is high, and the mechanical properties are good; it will not cause pore clogging, has good chemical stability, and strong corrosion resistance; it has antioxidant properties, reduces energy consumption by 40% compared with conventional aerators, and increases sewage treatment capacity by nearly 100%; it is non-magnetic, non-toxic, does not shed, does not pollute, and has good biocompatibility; it has good sealing properties, a compact structure, and is not easily damaged; it can be regenerated online, is easy to clean, and has a long service life.

[0015] Furthermore, the "high-salt biofilm method" is employed to maintain the biological concentration under low organic load:

[0016] (1) Biofilm method

[0017] The COD value of the wastewater entering the biological treatment system is not high. Under low organic load, in order to better maintain the biological concentration, highly hydrophilic biological packing materials with a large specific surface area are set in the biological treatment system to form an effective biofilm and enhance the removal of pollutants. The biofilm method is beneficial for the enrichment of organisms and the maintenance of biomass.

[0018] Features of high-efficiency denitrification packing:

[0019] ① Organic and inorganic composite materials, with large specific surface area, hydrophilic and microbial-friendly.

[0020] The packing material is made of special materials that are both microbial and hydrophilic, with a large specific surface area, fast biofilm formation, and easy operation. Under the premise of the presence of nitrifying bacteria, biofilm formation only takes 72 hours; the system can be put into normal operation in no more than one month.

[0021] ② Larger biofilm formation rate compared to traditional packing materials

[0022] The microbial concentration can reach 15-20 g / L, which is 5-6 times that of ordinary packing material for biofilm formation. It has a high load capacity and saves 25%-50% of the floor space.

[0023] ③ The packing material is suitable for the attachment of specific bacteria.

[0024] The packing material is developed based on the principle of denitrification and the composition of microorganisms. It has good hydrophilicity and microbial affinity. Based on its affinity for microorganisms, the packing material has a good effect on the selective immobilization of specific bacteria, especially nitrifying and denitrifying bacteria that participate in the denitrification process.

[0025] ④ Save operating costs

[0026] It can achieve sludge reduction. Compared with the traditional activated sludge process, the amount of residual activated sludge can be reduced by more than 50%. It is rich in biological components, with indicator organisms and metazoans that indicate good water quality appearing. After using the packing material, short-cut and simultaneous nitrification and denitrification occur, reducing the addition of carbon sources and alkalinity, and greatly reducing the reflux ratio, saving 1 / 2 of the operating costs compared with the traditional method.

[0027] (2) Measures to improve the salt tolerance of wastewater

[0028] The wastewater from this project has a high salt content. Salt-tolerant bacteria are added to the biological system to rapidly acclimate the bacteria in a high-salt environment and allow them to quickly attach to the biological packing material.

[0029] Furthermore, the "high-efficiency and low-consumption catalytic ozone oxidation" technology is used to further remove residual organic matter in the biochemical effluent.

[0030] Generally, the COD concentration of the first-stage reverse osmosis membrane concentrate is not high, but it contains a certain concentration of total nitrogen. For example, a certain reverse osmosis concentrate has a COD concentration of 120 mg / L and a TN concentration of 50 mg / L, resulting in an imbalanced C / N ratio in the wastewater. To ensure the denitrification effect of the biological system, a carbon source must be added to the influent. However, after adding a carbon source, there is a risk that the COD will be excessive and cannot be completely consumed by the biological system. To achieve long-term stable compliance of the effluent quality, a "high-efficiency, low-consumption catalytic ozone oxidation" unit is installed at the end of the biological system to further degrade the concentration of residual organic matter in the biological effluent.

[0031] This invention provides a multi-stage treatment process for saline wastewater from the petrochemical industry. It offers the following advantages:

[0032] This multi-stage treatment process for saline wastewater from the petrochemical industry, tailored to the characteristics of reverse osmosis membrane concentrate, combines chemical oxidation and biological coupling for simultaneous carbon and nitrogen removal through a synergistic effect of "multi-technology synergistic high-efficiency catalytic oxidation + high-salt biofilm method + high-efficiency low-consumption catalytic ozone oxidation," thereby improving the biodegradability of the wastewater. The biological system employs a high-salt biofilm method to enhance nitrogen removal. The advanced treatment utilizes a highly efficient, low-consumption catalytic ozone oxidation technology, which is particularly effective for low-concentration COD. This advanced, green, and efficient process achieves high-efficiency wastewater treatment, reduces wastewater treatment costs and energy consumption, and avoids secondary pollution, making it significant for achieving clean production and sustainable development goals. Attached Figure Description

[0033] Figure 1 Experimental results demonstrating the improvement of wastewater biodegradability for this utility model;

[0034] Figure 2 This is a schematic diagram illustrating the biotoxicity analysis of wastewater before and after oxidation according to the present invention.

[0035] Figure 3 These are the experimental results of the high-salt A / O biofilm device of this invention;

[0036] Figure 4 The results are from experiments using the efficient and low-consumption catalytic ozone oxidation process of this invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] like Figure 1-4 As shown in the figure, this embodiment of the invention provides a multi-stage treatment process for saline wastewater in the petrochemical industry, including reverse osmosis concentrate. The first step involves using reverse osmosis concentrate for efficient catalytic oxidation through multiple technologies. The second step involves treatment using a high-salt A / O biofilm method. The third step involves coagulation and sedimentation of the treated reverse osmosis concentrate. The fourth step involves oxidation using a high-efficiency, low-consumption catalytic ozone device. The fifth step achieves the final effluent.

[0039] Furthermore, addressing the issue of poor biodegradability caused by residual undegraded organic matter and microbial metabolites such as proteins, polysaccharides, and humic acids in wastewater, a "multi-technology synergistic high-efficiency catalytic oxidation" pretreatment technology is employed. This technology breaks down recalcitrant substances in the membrane concentrate, decomposing them into easily biodegradable substances, improving the wastewater's B / C ratio, and reducing its biotoxicity before it enters the subsequent biochemical system. The characteristics of multi-technology synergistic high-efficiency catalytic oxidation are: based on the composition of pollutants in the wastewater, multi-technology synergistic catalytic technology is used. Under different reaction conditions and operating parameters, it fully utilizes the oxidation characteristics of different oxidizing groups (such as hydroxyl radicals and oxygen radicals) to induce rapid chemical reactions (such as addition and substitution reactions) between specific oxidizing groups and pollutant functional groups. This achieves highly efficient and selective degradation of chromogenic groups such as C=C and C=O, as well as highly toxic and recalcitrant substances such as aromatics and heterocyclic compounds. In some stages of the reaction, process control avoids the problem of poor selectivity of hydroxyl radical (·OH) oxidation for target pollutants in the wastewater, while also avoiding competition between oxidants, effectively improving the efficiency of the oxidation reaction. In another stage of the oxidation reaction, the high oxidation potential of hydroxyl radicals (·OH) is fully utilized to react with organic matter in wastewater. The organic free radicals generated in the reaction can continue to participate in the chain reaction of hydroxyl radicals, or after generating organic peroxide free radicals, they can undergo further oxidative decomposition reactions until they are degraded into the final products CO2 and H2O.

[0040] Furthermore, the multi-technology synergistic high-efficiency catalytic oxidation technology employs multi-metal doped high-efficiency catalysts, multi-stage circulating tower reactors, and specially designed distributors, with the following characteristics:

[0041] (1) Salt-resistant multi-metal doped catalyst: This catalyst is a metal catalyst composed of multiple metals, characterized by its porous structure, high specific surface area, numerous active sites, low dosage, resistance to deactivation, and long lifespan (over 2 years). The addition of the catalyst greatly enhances the ability of the oxidant to generate hydroxyl radicals (·OH) on the catalyst surface, achieving an oxidant utilization rate of over 95%, which is several times higher than that of general catalytic oxidation. This technology is highly effective for high-salt, recalcitrant organic matter and has a high removal rate for coloring substances such as C=C and C=O in wastewater, significantly removing color and recalcitrant substances. Simultaneously, the catalyst exhibits a micro-expansion state within the tower, solving the catalyst caking problem and facilitating the treatment of wastewater with high hardness.

[0042] (2) Multi-circulation tower reactor enhances mass transfer efficiency and improves utilization rate.

[0043] The multi-circulation tower reactor employs a tower structure with a high height-to-diameter ratio, where gas and liquid contact in a counter-current manner. A special gas distributor generates high-density microbubbles (diameter less than 20 micrometers). The tower is equipped with functional catalytic packing, and through multi-circulation, the bubble rise velocity is significantly reduced (to only about 1% of that of bubbles from ordinary aeration discs). The bubble residence time in water is extended by tens of times, greatly improving the contact area and efficiency between the gas and organic matter and catalyst in the water, enhancing gas-liquid mass transfer, and effectively prolonging the gas-liquid contact time.

[0044] (3) Specially designed distributor with significant anti-clogging effect

[0045] It adopts a specially designed aeration disc with uniform pore size, high porosity, and stable pore shape; the air distribution plate has small pores, which can fully cut the oxidant into high-density microbubbles, resulting in good mixing effect; the bubbles diffuse evenly, and the gas-liquid interface area is large; the aeration resistance is low, the separation and purification efficiency is high, and the mechanical properties are good; it will not cause pore clogging, has good chemical stability, and strong corrosion resistance; it has antioxidant properties, reduces energy consumption by 40% compared with conventional aerators, and increases sewage treatment capacity by nearly 100%; it is non-magnetic, non-toxic, does not shed, does not pollute, and has good biocompatibility; it has good sealing properties, a compact structure, and is not easily damaged; it can be regenerated online, is easy to clean, and has a long service life.

[0046] Furthermore, the "high-salt biofilm method" is employed to maintain biological concentration under low organic load:

[0047] (1) Biofilm method

[0048] The COD value of the wastewater entering the biological treatment system is not high. Under low organic load, in order to better maintain the biological concentration, highly hydrophilic biological packing materials with a large specific surface area are set in the biological treatment system to form an effective biofilm and enhance the removal of pollutants. The biofilm method is beneficial for the enrichment of organisms and the maintenance of biomass.

[0049] Features of high-efficiency denitrification packing:

[0050] ① Organic and inorganic composite materials, with large specific surface area, hydrophilic and microbial-friendly.

[0051] The packing material is made of special materials that are both microbial and hydrophilic, with a large specific surface area, fast biofilm formation, and easy operation. Under the premise of the presence of nitrifying bacteria, biofilm formation only takes 72 hours; the system can be put into normal operation in no more than one month.

[0052] ② Larger biofilm formation rate compared to traditional packing materials

[0053] The microbial concentration can reach 15-20 g / L, which is 5-6 times that of ordinary packing material for biofilm formation. It has a high load capacity and saves 25%-50% of the floor space.

[0054] ③ The packing material is suitable for the attachment of specific bacteria.

[0055] The packing material is developed based on the principle of denitrification and the composition of microorganisms. It has good hydrophilicity and microbial affinity. Based on its affinity for microorganisms, the packing material has a good effect on the selective immobilization of specific bacteria, especially nitrifying and denitrifying bacteria that participate in the denitrification process.

[0056] ④ Save operating costs

[0057] It can achieve sludge reduction. Compared with the traditional activated sludge process, the amount of residual activated sludge can be reduced by more than 50%. It is rich in biological components, with indicator organisms and metazoans that indicate good water quality appearing. After using the packing material, short-cut and simultaneous nitrification and denitrification occur, reducing the addition of carbon sources and alkalinity, and greatly reducing the reflux ratio, saving 1 / 2 of the operating costs compared with the traditional method.

[0058] (2) Measures to improve the salt tolerance of wastewater

[0059] The wastewater from this project has a high salt content. Salt-tolerant bacteria are added to the biological system to rapidly acclimate the bacteria in a high-salt environment and allow them to quickly attach to the biological packing material.

[0060] Furthermore, the "high-efficiency and low-consumption catalytic ozone oxidation" technology is used to further remove residual organic matter in the biochemical effluent.

[0061] Generally, the COD concentration of the first-stage reverse osmosis membrane concentrate is not high, but it contains a certain concentration of total nitrogen. For example, a certain reverse osmosis concentrate has a COD concentration of 120 mg / L and a TN concentration of 50 mg / L, resulting in an imbalanced C / N ratio in the wastewater. To ensure the denitrification effect of the biological system, a carbon source must be added to the influent. However, after adding a carbon source, there is a risk that the COD will be excessive and cannot be completely consumed by the biological system. To achieve long-term stable compliance of the effluent quality, a "high-efficiency, low-consumption catalytic ozone oxidation" unit is installed at the end of the biological system to further degrade the concentration of residual organic matter in the biological effluent.

[0062] In summary, considering the characteristics of reverse osmosis membrane concentrate, a multi-technology synergistic high-efficiency catalytic oxidation technique is employed for pretreatment of the reverse osmosis concentrate to improve its biodegradability. The biological system utilizes a high-salt biofilm method to enhance denitrification. For advanced treatment, a highly efficient and low-consumption catalytic oxidation ozone technology, specifically designed for low-concentration COD, is employed. This advanced, green, and efficient process not only achieves high-efficiency wastewater treatment, reducing treatment costs and energy consumption, but also avoids secondary pollution, making it significant for achieving clean production and sustainable development goals.

[0063] In the PTA unit, the reverse osmosis concentrate from the water reuse system first undergoes "multi-technology synergistic high-efficiency catalytic oxidation pretreatment" to improve the biodegradability of the wastewater. Experimental results are as follows: Figure 1 As shown:

[0064] Depend on Figure 1It can be seen that the multi-technology synergistic high-efficiency catalytic oxidation (primary oxidation) mainly improves the biodegradability of PTA membrane concentrate, with an average TOC removal of about 10 mg / L and an average UV254 reduction of 63%.

[0065] The reverse osmosis concentrate from the PTA plant's water reuse system is treated using a multi-technology synergistic high-efficiency catalytic oxidation process. Biotoxicity analysis of the wastewater before and after oxidation is as follows: Figure 2 As shown:

[0066] Depend on Figure 2 It can be seen that after the reverse osmosis concentrate (PTA membrane concentrate) of Yizheng Chemical Fiber is pretreated by a multi-technology synergistic high-efficiency catalytic oxidation device, the biological toxicity is improved from high to low, and the biodegradability of the wastewater is further improved, which is more conducive to subsequent biological treatment.

[0067] In the PTA unit, the reverse osmosis concentrate from the water reuse system is pretreated using a multi-technology synergistic high-efficiency catalytic oxidation process before entering the high-salt A / O biofilm unit. Experimental results are as follows: Figure 3 As shown:

[0068] Depend on Figure 3 It can be seen that the average TOC removal rate in the high-salt A / O biochemical section is approximately 18 mg / L.

[0069] The effluent from the high-salt A / O biofilm unit first undergoes coagulation and sedimentation, followed by a high-efficiency, low-consumption catalytic ozone oxidation process. Experimental results are as follows: Figure 4 As shown:

[0070] Depend on Figure 4 It can be seen that the advanced treatment section (secondary coagulation + secondary oxidation) removes an average of about 6 mg / L of TOC from the wastewater, and the final effluent TOC concentration can be stabilized below 18 mg / L (COD≤40 mg / L).

[0071] Based on the above experimental data, the following experimental results were obtained:

[0072] (1) In the experiment, the PTA membrane concentrate was first coagulated to remove suspended solids and colloids in the membrane concentrate. The TOC removal amount was about 9 mg / L.

[0073] (2) Multi-technology synergistic high-efficiency catalytic oxidation (primary oxidation) mainly improves the biodegradability of PTA membrane concentrate, with an average TOC removal of about 10 mg / L and a 67% reduction in UV254.

[0074] (3) The average TOC removal rate in the high-salt A / O biochemical section is approximately 18 mg / L;

[0075] (4) The average TOC removal rate in the advanced treatment section (secondary coagulation + secondary oxidation) is approximately 6 mg / L;

[0076] (5) The final effluent TOC concentration can be kept below 18 mg / L (COD≤40 mg / L).

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multi-stage treatment process for saline wastewater from the petrochemical industry, comprising reverse osmosis concentrate, characterized in that: The first step involves using reverse osmosis concentrate for efficient catalytic oxidation through a multi-technology synergy; the second step utilizes a high-salt A / O biofilm method for treatment; the third step involves coagulation and sedimentation of the treated reverse osmosis concentrate; the fourth step utilizes a high-efficiency, low-consumption catalytic ozone device for oxidation; and the fifth step achieves the final effluent.

2. The multi-stage treatment process for saline wastewater in the petrochemical industry according to claim 1, characterized in that: To address the issue of poor biodegradability caused by residual undegraded organic matter and microbial metabolites such as proteins, polysaccharides, and humic acids in wastewater, a "multi-technology synergistic high-efficiency catalytic oxidation" pretreatment technology is employed. This technology breaks down recalcitrant substances in the membrane concentrate, decomposing them into easily biodegradable substances, improving the wastewater's biodegradability (B / C ratio), and reducing its biotoxicity before it enters the subsequent biochemical system. The characteristics of this multi-technology synergistic high-efficiency catalytic oxidation are: based on the composition of pollutants in the wastewater, multi-technology synergistic catalytic technology is used. Under different reaction conditions and controlled operating parameters, it fully utilizes the oxidation characteristics of different oxidizing groups (such as hydroxyl radicals and oxygen radicals) to induce rapid chemical reactions (such as addition and substitution reactions) between specific oxidizing groups and the functional groups of pollutants. This achieves highly efficient and selective degradation of chromogenic groups such as C=C and C=O, as well as highly toxic and recalcitrant substances such as aromatics and heterocyclic compounds. In some stages of the reaction, process control avoids the problem of poor selectivity of hydroxyl radical (·OH) oxidation for target pollutants in the wastewater, while also avoiding competition between oxidants, effectively improving the efficiency of the oxidation reaction. In another stage of the oxidation reaction, the high oxidation potential of hydroxyl radicals (·OH) is fully utilized to react with organic matter in wastewater. The organic free radicals generated in the reaction can continue to participate in the chain reaction of hydroxyl radicals, or after generating organic peroxide free radicals, they can undergo further oxidative decomposition reactions until they are degraded into the final products CO2 and H2O.

3. The multi-stage treatment process for saline wastewater in the petrochemical industry according to claim 1, characterized in that: The aforementioned multi-technology synergistic high-efficiency catalytic oxidation technology employs multi-metal doped high-efficiency catalysts, multi-stage circulating tower reactors, and specially designed distributors, and has the following characteristics: (1) Salt-resistant multi-metal doped catalyst: This catalyst is a metal catalyst composed of multiple metals, characterized by its porous structure, high specific surface area, numerous active sites, low dosage, resistance to deactivation, and long lifespan (over 2 years). The addition of the catalyst greatly enhances the ability of the oxidant to generate hydroxyl radicals (·OH) on the catalyst surface, achieving an oxidant utilization rate of over 95%, which is several times higher than that of general catalytic oxidation. This technology is highly effective for high-salt, recalcitrant organic matter and has a high removal rate for coloring substances such as C=C and C=O in wastewater, significantly removing color and recalcitrant substances. Simultaneously, the catalyst exhibits a micro-expansion state within the tower, solving the catalyst caking problem and facilitating the treatment of wastewater with high hardness. (2) Multi-circulation tower reactor enhances mass transfer efficiency and improves utilization rate. The multi-circulation tower reactor adopts a tower structure with a large height-to-diameter ratio, and the gas and liquid come into contact in a countercurrent manner, generating high-density microbubbles (with a diameter of less than 20 micrometers) through a special gas distributor. The tower is equipped with functional catalytic packing, which greatly reduces the rising speed of bubbles (to only about 1% of that of bubbles in ordinary aeration discs) through several times circulation. The residence time of bubbles in water is extended by tens of times, which greatly improves the contact area and efficiency between gas and organic matter and catalyst in water, enhances gas-liquid mass transfer, and effectively prolongs gas-liquid contact time. (3) Specially designed distributor with significant anti-clogging effect It adopts a specially designed aeration disc with uniform pore size, high porosity, and stable pore shape; the air distribution plate has small pores, which can fully cut the oxidant into high-density microbubbles, resulting in good mixing effect; the bubbles diffuse evenly and the gas-liquid interface area is large; the aeration resistance is low, the separation and purification efficiency is high, and the mechanical properties are good; it will not cause pore blockage, has good chemical stability, and strong corrosion resistance. It has antioxidant properties, reduces energy consumption by 40% compared to conventional aerators, and nearly doubles the wastewater treatment capacity; Non-magnetic, non-toxic, non-shedding, non-polluting, and biocompatible; It has good sealing properties, a compact structure, and is not easily damaged; it can be regenerated online, is easy to clean, and has a long service life.

4. The multi-stage treatment process for saline wastewater in the petrochemical industry according to claim 1, characterized in that: The method employs a "high-salt biofilm method" to maintain biological concentration under low organic load: (1) Biofilm method The COD value of the wastewater entering the biological treatment system is not high. Under low organic load, in order to better maintain the biological concentration, highly hydrophilic biological packing materials with a large specific surface area are set in the biological treatment system to form an effective biofilm and enhance the removal of pollutants. The biofilm method is beneficial for the enrichment of organisms and the maintenance of biomass. Features of high-efficiency denitrification packing: ① Organic and inorganic composite materials, with large specific surface area, hydrophilic and microbial-friendly. The packing material is made of special materials that are both microbial and hydrophilic, with a large specific surface area, fast biofilm formation, and easy operation. Under the premise of the presence of nitrifying bacteria, biofilm formation only takes 72 hours; the system can be put into normal operation in no more than one month. ② Larger biofilm formation rate compared to traditional packing materials The microbial concentration can reach 15-20 g / L, which is 5-6 times that of ordinary packing material for biofilm formation. It has a high load capacity and saves 25%-50% of the floor space. ③ The packing material is suitable for the attachment of specific bacteria. The packing material is developed based on the principle of denitrification and the composition of microorganisms. It has good hydrophilicity and microbial affinity. Based on its affinity for microorganisms, the packing material has a good effect on the selective immobilization of specific bacteria, especially nitrifying and denitrifying bacteria that participate in the denitrification process. ④ Save operating costs It can achieve sludge reduction. Compared with the traditional activated sludge process, the amount of residual activated sludge can be reduced by more than 50%. It is rich in biological components, with indicator organisms and metazoans that indicate good water quality appearing. After using the packing material, short-cut and simultaneous nitrification and denitrification occur, reducing the addition of carbon sources and alkalinity, and greatly reducing the reflux ratio, saving 1 / 2 of the operating costs compared with the traditional method. (2) Measures to improve the salt tolerance of wastewater The wastewater from this project has a high salt content. Salt-tolerant bacteria are added to the biological system to rapidly acclimate the bacteria in a high-salt environment and allow them to quickly attach to the biological packing material.

5. The multi-stage treatment process for saline wastewater in the petrochemical industry according to claim 1, characterized in that: The technology employs "high-efficiency, low-consumption catalytic ozone oxidation" to further remove residual organic matter in the biochemical effluent. Generally, the COD concentration of the first-stage reverse osmosis membrane concentrate is not high, but it contains a certain concentration of total nitrogen. For example, a certain reverse osmosis concentrate has a COD concentration of 120 mg / L and a TN concentration of 50 mg / L, resulting in an imbalanced C / N ratio in the wastewater. To ensure the denitrification effect of the biological system, a carbon source must be added to the influent. However, after adding a carbon source, there is a risk that the COD will be excessive and cannot be completely consumed by the biological system. To achieve long-term stable compliance of the effluent quality, a "high-efficiency, low-consumption catalytic ozone oxidation" unit is installed at the end of the biological system to further degrade the concentration of residual organic matter in the biological effluent.

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