Wastewater pretreatment method based on wet oxygen method

Abstract

The invention discloses a wastewater pretreatment method based on a wet oxygen method, and particularly relates to the field of wastewater treatment.The wastewater pretreatment method comprises the steps that all wastewater sources are sampled and calibrated, the content and proportion of organic pollutants, inorganic pollutants and characteristic pollutants in wastewater are analyzed, meanwhile, reference indexes of the wastewater are measured, and an analysis result is obtained; and the wastewater is classified according to an analysis result. According to the scheme, through two-stage operation of the wet oxygen reactor, ring opening and chain scission reactions of macromolecular organic matters are realized, and micromolecules are further oxidized and mineralized into inorganic products; in the first stage, the generation efficiency of hydroxyl radicals is optimized by utilizing temperature and pressure, and complex organic matters are decomposed according to time-sensitive reaction characteristics; in the second stage, micromolecule mineralization is accelerated by increasing the temperature, and residues of organic pollutants are reduced to the maximum extent; the problem that an existing wet oxygen method is not high in treatment efficiency under a single condition is solved, and the removal effect of organic pollutants in wastewater is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and more specifically, to a wastewater pretreatment method based on the wet oxygen method. Background Art

[0002] The existing wet oxygen method is mostly used to treat high-concentration organic wastewater. Its advantage lies in the ability to degrade difficult-to-decompose organic pollutants using hydroxyl radicals under high-temperature and high-pressure conditions. However, the traditional wet oxygen method usually operates under a single reaction condition and does not perform segmented treatment according to the characteristics of different pollutants, resulting in insufficient degradation of some macromolecular organic substances and difficulty in completely mineralizing small-molecular organic substances. In addition, volatile organic compounds may cause explosion or corrosion of equipment under high temperature and pressure, and the treatment of tail gas and waste heat utilization have not been fully optimized. These problems limit the wide application of the wet oxygen method in complex wastewater treatment.

[0003] The single reaction condition of the traditional wet oxygen method is difficult to meet the degradation requirements of various organic substances in wastewater. Especially when treating complex wastewater, the reaction conditions are not adjusted according to the time and temperature sensitivity, resulting in low degradation efficiency and insufficient mineralization. For example, in actual operation, high-concentration macromolecular pollutants require a longer time to decompose, while small-molecular pollutants require a higher temperature to achieve complete oxidation. Therefore, the traditional process has an efficiency bottleneck when treating different pollutants and fails to effectively control the biodegradability of the subsequent oxidation liquid, posing challenges to the subsequent biochemical treatment. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a wastewater pretreatment method based on the wet oxygen method, which realizes the ring-opening and chain-breaking reactions of macromolecular organic substances through two-stage operation of a wet oxygen reactor, and further oxidizes and mineralizes small molecules into inorganic products. In the first stage, the generation efficiency of hydroxyl radicals is optimized by temperature and pressure, and complex organic substances are decomposed according to the reaction characteristics sensitive to time. In the second stage, the temperature is increased to accelerate the mineralization of small molecules, minimizing the residue of organic pollutants to solve the problems proposed in the above background art.

[0005] To achieve the above object, the present invention provides the following technical solution: A wastewater pretreatment method based on the wet oxygen method, comprising:

[0006] First, sample and calibrate all wastewater sources, analyze the content and proportion of organic pollutants, inorganic pollutants, and characteristic pollutants in the wastewater, and simultaneously measure the reference indicators of the wastewater to obtain the analysis results, and classify the wastewater according to the analysis results.

[0007] Immediately afterwards, for the volatile organic compounds present in the wastewater, perform light component removal pretreatment by heating or flash evaporation.

[0008] Before the wastewater enters the wet oxygen reactor, the suspended particulate pollutants in the wastewater are removed through a filter;

[0009] The wet oxygen reactor uses a two-stage operation to determine the removal efficiency of organic pollutants in wastewater and the feasibility of subsequent treatment. The first stage involves controlling the temperature at 150°C–200°C and maintaining the pressure at 5MPa–7MPa. Hydroxyl radicals react with macromolecular organic matter through ring-opening and chain-scission reactions to generate intermediate products with good biodegradability. The second stage increases the temperature to 250°C–300°C and maintains the pressure at 7MPa–8MPa.

[0010] When the pH value of the oxidized liquid produced after the wet oxygen treatment is lower than the preset pH threshold, an alkaline neutralizer is added until the pH value is adjusted to the preset pH threshold range; when the biodegradability of the oxidized liquid is higher than the preset biodegradability threshold through the B / C ratio test, biochemical treatment is directly carried out; when the B / C ratio is lower than the preset B / C ratio threshold, a bioactive agent is added or a secondary oxidation treatment is carried out;

[0011] The water vapor in the tail gas is condensed and separated by flash evaporation, and volatile organic compounds are captured. Then, the harmful gases remaining in the tail gas are removed by activated carbon adsorption. The waste heat of the tail gas is recovered through a heat exchanger and used to preheat wastewater or provide low-pressure steam.

[0012] During the trial operation phase, an online monitoring model was established based on the engineering risk assessment of the wet oxygen method. The online monitoring model included equipment operating status monitoring, corrosion condition assessment, and operating parameter optimization.

[0013] In a preferred embodiment, the reference indicators include chemical oxygen demand, biochemical oxygen demand, B / C ratio, pH value and total dissolved solids; the characteristic pollutants include acetone, dichloromethane, ammonia nitrogen at a preset concentration, and macromolecular organic matter with sugar-like properties.

[0014] In a preferred embodiment, wastewater classification and reference index calculation are performed based on a multi-index comprehensive decision-making model;

[0015]

[0016] Where Z is the comprehensive pollution index; w i is the dynamic weight of the i-th indicator; i is the influence coefficient of the i-th indicator on the system; M i is the actual value of the i-th indicator; M i,min , M i,max Respectively represent the lower limit and upper limit of the i-th indicator; γ i is the nonlinear adjustment index of the i-th indicator;

[0017] By comprehensively considering the gas-liquid equilibrium and mass transfer resistance, the separation efficiency of volatile organic compounds is calculated through a mass transfer model;

[0018]

[0019] where E VOC is the separation efficiency of volatile organic compounds; k L is the liquid-phase mass transfer coefficient; a is the ratio of the gas-liquid contact area; H is the Henry coefficient; C L is the actual concentration of volatile organic compounds in the liquid phase; C L,eq is the equilibrium concentration of volatile organic compounds in the liquid phase.

[0020] In a preferred embodiment, in the filtration and removal of suspended particles, based on the superposition effect of pressure drop, the stepwise interception of suspended particles by each layer of filter screen is described; a cumulative resistance model is established, and the filtration efficiency is analyzed through the cumulative resistance model considering the comprehensive effect of multiple layers of filter screens;

[0021]

[0022] where η filter is the multi-layer filtration efficiency; ΔP i is the pressure drop of the i-th layer of filter screen; P in is the inlet pressure; m is the number of filter screen layers.

[0023] In a preferred embodiment, by coupling the dual effects of time and temperature and introducing the reaction order to describe the degradation characteristics at different stages; the degradation characteristics include being sensitive to time in the first stage and sensitive to temperature in the second stage; a two-parameter kinetic model of the wet oxygen reaction degradation process is established based on the two-stage operation of the wet oxygen reactor;

[0024]

[0025] where C t , C0 are the pollutant concentrations at time t and the initial time respectively; k1, k2 are the influence coefficients of time and temperature on the reaction rate respectively; β1, β2 are the reaction orders of time and temperature respectively; t is the reaction time; T is the reaction temperature.

[0026] In a preferred embodiment, in the post-treatment and regulation of the oxidation liquid, by coupling the synergistic effect of the surfactant dosage and pH, the comprehensive effect of chemical regulation and biological enhancement is reflected, and a B / C ratio regulation model of the oxidation liquid is established by combining surfactant addition and oxidation enhancement:

[0027] B / C new =(B / C orig +κC bio )·(1+θe<l -pH )

[0028] where B / C new is the regulated B / C ratio; B / C orig is the original B / C ratio; κ is the activation agent enhancement coefficient; C bio is the dosage of the activation agent; θ is the influence weight of pH on the regulated B / C ratio; -pH is the exponential decay factor of pH value on the regulation effect.

[0029] Technical effects and advantages of the present invention:

[0030] 1. Through the two-stage operation of the wet oxygen reactor in this solution, the ring-opening and chain-breaking reactions of macromolecular organic compounds are realized, and small molecules are further oxidized and mineralized into inorganic products; in the first stage, the generation efficiency of hydroxyl radicals is optimized by temperature and pressure, and complex organic compounds are decomposed according to the reaction characteristics sensitive to time; in the second stage, the mineralization of small molecules is accelerated by increasing the temperature to minimize the residue of organic pollutants; the problem that the existing wet oxygen method has low treatment efficiency under a single condition is solved, and the removal effect of organic pollutants in wastewater is improved;

[0031] 2. The light components of volatile organic compounds in the wastewater are removed by heating or flash evaporation technology to prevent potential safety hazards under high temperature and high pressure conditions, and at the same time reduce the burden on the wet oxygen reactor by volatile components;

[0032] 3. By constructing a regulation model for the B / C ratio of the oxidation liquid and combining the synergistic effect of the addition of the activation agent and pH regulation, the biodegradability of the oxidation liquid is dynamically optimized; by adjusting the activation agent enhancement coefficient and the pH exponential decay factor, the composition of the oxidation liquid is regulated, so as to ensure the applicability of subsequent biochemical treatment;

[0033] 4. A combined technology of flash evaporation and activated carbon adsorption is adopted to remove volatile organic compounds and residual harmful gases in the tail gas, and at the same time, the waste heat of the tail gas is recovered by a heat exchanger for wastewater preheating or low-pressure steam supply, optimizing the energy efficiency of the system and reducing the operating cost. Brief description of the drawings

[0034] Figure 1 is the flow chart of the present invention. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] Refer to the attached specification Figure 1, A wastewater pretreatment method based on the wet oxygen method according to an embodiment of the present invention includes:

[0037] Step 1: Wastewater source and composition analysis

[0038] First, sample and calibrate all wastewater sources, analyze the content and proportion of organic pollutants, inorganic pollutants, and characteristic pollutants in the wastewater, and at the same time measure the reference indicators of the wastewater to obtain the analysis results, and classify the wastewater according to the analysis results;

[0039] Step 2: Light component removal pretreatment

[0040] Immediately afterwards, for the volatile organic compounds present in the wastewater, perform light component removal pretreatment by heating or flashing to reduce the burden on the wet oxygen device. The light component removal tower is the core equipment. By preheating the wastewater to 60–70°C and utilizing the low boiling point characteristics of the light components, separate them from water; in this process, directly heat with steam and maintain the pressure at atmospheric pressure to 1.2 MPa to ensure that the light components are fully volatilized. At the same time, capture and recover the volatiles through the tail gas condensation device. The recovered light components are further processed or safely disposed according to their properties to prevent secondary pollution. After the light component removal is completed, the concentration of volatile organic compounds (such as VOC) in the wastewater needs to be reduced to less than 50 mg / L to meet the safety operation requirements of the subsequent wet oxygen reactor;

[0041] Step 3: Suspended solid removal

[0042] Before the wastewater enters the wet oxygen reactor, remove the suspended particulate pollutants in the wastewater through a filter to avoid clogging and coking phenomena in the high-temperature and high-pressure environment; a dual-precision filter with one in use and one standby is set in this step, and the filtration accuracy is controlled at 0.1–0.5 mm. It is recommended to choose an alloy material with strong corrosion resistance for the filter mesh material; after filtration, it is necessary to evaluate the particulate removal rate through on-line monitoring to ensure that the suspended particulate concentration is less than 50 ppm. At the same time, the filter can be selected to have an on-line backwashing function and be cleaned once every 8–12 hours to maintain efficient operation;

[0043] Step 4: Optimization of the wet oxygen reaction process

[0044] The wet oxygen reactor uses a two-stage operation to determine the removal efficiency of organic pollutants in wastewater and the feasibility of subsequent treatment. The first stage involves controlling the temperature at 150°C–200°C and maintaining the pressure at 5MPa–7MPa. Hydroxyl radicals react with macromolecular organic matter through ring-opening and chain-breaking reactions to generate intermediate products with good biodegradability, including small-molecule organic acids. The second stage increases the temperature to 250°C–300°C and maintains the pressure at 7MPa–8MPa to oxidize small-molecule organic matter and mineralize it into inorganic products such as CO2, H2O, and NH3 as much as possible. A compressed air station is used to supply oxygen, and a flow control valve is used to maintain an oxygen excess ratio between 2.0–2.5 to ensure the efficient generation of hydroxyl radicals in the reaction system. The COD removal rate of the reaction effluent is monitored online in real time, with the goal of a single-pass removal rate of ≥70%.

[0045] Step 5: Post-treatment and regulation of oxidation solution

[0046] When the pH value of the oxidizing liquid produced after wet oxygen treatment is lower than the preset pH threshold, an alkaline neutralizer is added, including NaOH or Ca(OH)2, until the pH value is adjusted to the preset pH threshold range to prevent the oxidizing liquid from corroding subsequent pipelines and equipment; when the biodegradability of the oxidizing liquid is higher than the preset biodegradability threshold through the B / C ratio test, biochemical treatment is directly carried out; when the B / C ratio is lower than the preset B / C ratio threshold, a bioactive agent is added or a secondary oxidation treatment is implemented to improve the biodegradability; in addition, when high salt components are detected in the oxidizing liquid, a low-temperature evaporation and concentration process is used to separate the inorganic salts before biochemical treatment is carried out to ensure that the oxidizing liquid meets the emission standard requirements;

[0047] Step 6: Exhaust gas purification and waste heat recovery

[0048] The water vapor in the tail gas is condensed and separated by flash evaporation, and trace volatile organic compounds are captured. Then, the harmful gases remaining in the tail gas are removed by activated carbon adsorption. The waste heat of the tail gas is recovered through a heat exchanger and used to preheat wastewater or provide low-pressure steam.

[0049] Step 7: Engineering risk assessment and optimization improvements

[0050] During the trial operation phase, an online monitoring model was established based on the engineering risk assessment of the wet oxygen method. The online monitoring model included equipment operating status monitoring, corrosion condition assessment, and operating parameter optimization.

[0051] It should be noted that: Based on the characteristics of the wet oxygen method, combined with the actual treatment requirements of the wastewater composition, the treatment process is gradually optimized to achieve efficient pollutant removal and equipment operation stability; First, for the diverse organic pollutants, inorganic pollutants, and characteristic pollutants in the wastewater, through sampling calibration and analysis classification, accurate basis is provided for staged treatment, aiming to avoid resource waste and low treatment efficiency caused by one-size-fits-all;

[0052] For the light component removal of volatile organic compounds, heating or flash evaporation technology is adopted, which is based on the physical properties of volatile components, such as low boiling point and high volatility, as well as the potential safety hazards in high temperature and high pressure environments. Therefore, a temperature range of 60°C - 70°C and a pressure range from atmospheric pressure to 1.2 MPa are set, which are derived from the experimentally verified gas-liquid equilibrium conditions to ensure the full removal of volatile organic compounds; In the wet oxygen reaction, the step-by-step degradation of pollutants is achieved through staged operation (the first stage: 150°C - 200°C, 5 MPa - 7 MPa; the second stage: 250°C - 300°C, 7 MPa - 8 MPa). The conditions in the first stage are suitable for the ring-opening and chain-breaking reactions of macromolecular organic compounds, and the degradation efficiency is improved through hydroxyl radicals. In the second stage, the higher temperature and pressure accelerate the mineralization of small molecules into inorganic substances; When the pH of the treated oxidation liquid is lower than the preset range, it is adjusted to neutral by adding alkaline neutralizing agents because a neutral environment can effectively prevent pipeline and equipment corrosion; At the same time, the B / C ratio test is used to determine whether the oxidation liquid is suitable for direct entry into biochemical treatment or requires further strengthening treatment. Based on this, the system economy and treatment effect are ensured; The tail gas treatment adopts flash evaporation and activated carbon adsorption design, based on the fact that volatile organic compounds and harmful gases in the tail gas need to be physically separated and chemically adsorbed to ensure up-to-standard emissions. At the same time, the waste heat of the tail gas is recovered through a heat exchanger for wastewater preheating or steam supply, which not only improves energy efficiency but also reduces operating costs;

[0053] The reference indicators include chemical oxygen demand, biochemical oxygen demand, B / C ratio, pH value, and total dissolved solids; The characteristic pollutants include acetone, dichloromethane, ammonia nitrogen at a preset concentration, and macromolecular organic compounds with sugar-like properties.

[0054] Based on the multi-index comprehensive decision-making model, the wastewater is classified and the reference indicators are calculated;

[0055]

[0056] Where Z is the comprehensive pollution index, and the comprehensive pollution index is used to reflect the overall pollution severity of the wastewater; w i is the dynamic weight of the i-th index; λ i is the influence coefficient of the i-th index on the system; M i is the actual value of the i-th index; M i,min , M i,maxrespectively represent the lower limit value and the upper limit value of the i-th index; γ i is the non-linear adjustment index of the i-th index, which is used to amplify or weaken the influence of a certain index;

[0057] By comprehensively considering the gas-liquid equilibrium and mass transfer resistance, the separation efficiency of volatile organic compounds is calculated through a mass transfer model;

[0058]

[0059] where E VOC is the separation efficiency of volatile organic compounds; k L is the liquid-phase mass transfer coefficient, which is used to reflect the transfer rate of solute in the liquid phase; a is the ratio of the gas-liquid contact area; H is the Henry's law constant, which is used to represent the gas-liquid equilibrium characteristics of the solute; C L is the actual concentration of volatile organic compounds in the liquid phase; C L,eq is the equilibrium concentration of volatile organic compounds in the liquid phase;

[0060] By combining Henry's law with the mass transfer rate model, which reflects the efficiency of volatile organic compounds transferring from the liquid phase to the gas phase, the mass transfer coefficient k L and the contact area a are improved through equipment optimization, while the Henry's law constant is related to the physical properties of volatile organic compounds;

[0061] In addition, the above scheme uses a multi-index comprehensive decision-making model to classify wastewater and calculate reference indicators. The core of this step is to construct a comprehensive pollution index to reflect the overall pollution degree of wastewater. Among them, dynamic weights and non-linear adjustment indexes are introduced to flexibly adjust the importance and influence range of each index; the necessity of this design lies in the complexity of wastewater components. For example, chemical oxygen demand may have a greater weight in some wastewater treatments, while total dissolved solids may be more critical in other cases. Therefore, it is necessary to dynamically allocate weights and amplify or weaken specific indicators to ensure that the model is highly adaptable and the classification is reasonable; secondly, the separation of volatile organic compounds uses a mass transfer model, which combines gas-liquid equilibrium and mass transfer resistance to describe the process of volatile organic compounds transferring from the liquid phase to the gas phase; the mass transfer coefficient and the contact area are determined by equipment optimization, and the Henry's law constant is related to the physical properties of volatile organic compounds. The principle of the design is to maximize the separation effect by improving the gas-liquid contact efficiency and optimizing the equipment structure.

[0062] In the filtration and removal of suspended particles, based on the superposition effect of pressure drop, the step-by-step interception effect of each layer of filter screen on suspended particles is described; a cumulative resistance model is established, and the filtration efficiency is analyzed through the cumulative resistance model considering the comprehensive effect of multiple layers of filter screens;

[0063]

[0064] where ηfilter is the multi-layer filtration efficiency; ΔP i is the pressure drop of the i-th filter layer; P in is the inlet pressure; m is the number of filter layers;

[0065] A multi-layer filter efficiency model based on the pressure drop superposition effect is used to describe the gradual retention of particulate matter when wastewater passes through the multi-layer filter. By treating the retention effect of each layer of filter as an independent pressure drop contribution, the overall filtration efficiency of the multi-layer filter is comprehensively analyzed through the cumulative resistance model. Specifically, the filtration efficiency is related to the ratio of the pressure drop of each layer of filter to the inlet pressure. The greater the pressure drop, the higher the proportion of particulate matter retained. The multi-layer filter gradually improves the overall filtration efficiency through the superposition of pressure drops, thereby achieving efficient removal of suspended particles. The pressure drop ratio of each layer of filter in the above formula reflects the reduction in the probability of particle penetration, and the unified standardization of inlet pressure makes the model adaptable to different operating conditions. This design is based on the complexity of actual wastewater treatment. Suspended particles may have diverse particle sizes and distribution characteristics. A single-layer filter often cannot fully meet the requirements of efficient removal. Therefore, a multi-layer filter design is adopted to enhance the filtration capacity. At the same time, the cumulative resistance model avoids redundant design caused by the increase in the number of filter layers.

[0066] By coupling the dual effects of time and temperature and introducing reaction orders, the degradation characteristics of different stages are described. The degradation characteristics include time sensitivity in the first stage and temperature sensitivity in the second stage. A two-parameter kinetic model of the wet oxygen reaction degradation process is established based on the two-stage operation of the wet oxygen reactor.

[0067]

[0068] Among them C t , C0 are the pollutant concentrations at time t and the initial time respectively; k1 and k2 are the influence coefficients of time and temperature on the reaction rate respectively; β1 and β2 are the reaction orders of time and temperature respectively; t is the reaction time; T is the reaction temperature;

[0069] By constructing a two-parameter kinetic model for wet oxygen reaction degradation, the dual effects of time and temperature are coupled to describe the degradation characteristics of pollutants at different stages. The first stage relies on time to break the chain and open the ring of large organic molecules, while the second stage accelerates the mineralization of small molecules into inorganic substances at higher temperatures. The time and temperature sensitivity parameters and response order introduced in the formula accurately describe their contributions to the degradation rate. Based on the wet oxygen reaction mechanism, combined with dynamic adjustment of reaction conditions, the above formula achieves precise control of pollutant removal.

[0070] In the post-treatment and regulation of the oxidation liquid, the combined effect of chemical regulation and biological enhancement is reflected by coupling the synergistic effects of the surfactant dosage and pH. A B / C ratio regulation model of the oxidation liquid is established by combining surfactant addition and oxidation enhancement:

[0071] B / C new =(B / C orig +κC bio )·(1 + θe -pH )

[0072] Where B / C new is the regulated B / C ratio; B / C orig is the original B / C ratio; κ is the surfactant enhancement coefficient; C bio is the surfactant dosage; θ is the influence weight of pH on the regulated B / C ratio; -pH is the exponential decay factor of pH on the regulation effect, - is the decay rate coefficient, and pH is the pH value of the solution;

[0073] By constructing a B / C ratio regulation model of the oxidation liquid and combining the synergistic effects of the surfactant dosage and pH value, the comprehensive effect of chemical regulation and biological enhancement is achieved; in the formula, the surfactant dosage affects the improvement amplitude of biodegradability, and the pH value adjusts the regulation efficiency through the exponential term, reflecting the dynamic influence of acid-base conditions on the biochemical effect; the regulated B / C ratio is jointly determined by the original B / C ratio, the surfactant enhancement coefficient, and the pH value decay factor; this model is designed because the biodegradability in the oxidation liquid needs to be optimized under both chemical and biological conditions, and the coupling effect of the surfactant and pH value can significantly enhance the degradation effect; in practical applications, this model provides a scientific basis for optimizing the surfactant dosage and regulating the oxidation liquid, and dynamically adapts to different wastewater characteristics to ensure the economy and effectiveness of subsequent treatment.

[0074] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A wastewater pretreatment method based on the wet oxygen method, characterized in that, Including: First, sample and calibrate all wastewater sources, analyze the contents and proportions of organic pollutants, inorganic pollutants, and characteristic pollutants in the wastewater, and simultaneously measure the reference indicators of the wastewater to obtain the analysis results, and classify the wastewater based on the analysis results; Immediately afterwards, for the volatile organic compounds present in the wastewater, perform light component removal pretreatment by heating or flash evaporation; Before the wastewater enters the wet oxidation reactor, remove the suspended particulate pollutants in the wastewater through a filter; Based on the wet oxidation reactor, the removal effect of organic pollutants in the wastewater and the feasibility of subsequent treatment are determined through two-stage operation; the first-stage operation includes controlling the temperature at 150°C–200°C and maintaining the pressure at 5MPa–7MPa, and performing ring-opening and chain-breaking reactions on macromolecular organic compounds through hydroxyl radicals to generate intermediate products with good biodegradability; In the second stage, raise the temperature to 250°C–300°C and keep the pressure at 7MPa–8MPa; When the pH value of the oxidation liquid generated after wet oxidation treatment is lower than the preset pH threshold, add an alkaline neutralizing agent until the pH value is adjusted within the preset pH threshold range; when the biodegradability of the oxidation liquid is higher than the preset biodegradability threshold through the B / C ratio test, directly perform biochemical treatment; when the B / C ratio is lower than the preset B / C ratio threshold, add a biological activator or perform secondary oxidation treatment; Condense and separate the water vapor in the tail gas by flash evaporation and capture the volatile organic compounds, and then remove the residual harmful gases in the tail gas by activated carbon adsorption; Recover the waste heat of the tail gas through a heat exchanger for preheating the wastewater or providing low-pressure steam; In the trial operation stage, based on the assessment of the engineering risks of the wet oxidation method, establish an online monitoring model, and the online monitoring model includes equipment operation status monitoring, corrosion condition assessment, and operation parameter optimization.

2. A wastewater pretreatment method based on the wet oxidation method according to claim 1, wherein: The reference indicators include chemical oxygen demand, biochemical oxygen demand, B / C ratio, pH value, and total dissolved solids; the characteristic pollutants include acetone, dichloromethane, ammonia nitrogen at a preset concentration, and macromolecular organic compounds with sugar-like properties.

3. A wastewater pretreatment method based on the wet oxidation method according to claim 2, wherein: Based on a multi-index comprehensive decision-making model, calculate the wastewater classification and reference indicators; where Z is the comprehensive pollution index; w i is the dynamic weight of the i-th index; λ i is the influence coefficient of the i-th index on the system; M i is the actual value of the i-th index; M i,min , M i,max respectively represent the lower limit value and the upper limit value of the i-th index; γ i is the non-linear adjustment index of the i-th index; By comprehensively considering gas-liquid equilibrium and mass transfer resistance, the separation efficiency of volatile organic compounds is calculated through a mass transfer model; Among them, E VOC is the separation efficiency of volatile organic compounds; k L is the liquid-phase mass transfer coefficient; a is the ratio of the gas-liquid contact area; H is the Henry coefficient; C L is the actual concentration of volatile organic compounds in the liquid phase; C L,eq is the equilibrium concentration of volatile organic compounds in the liquid phase.

4. A wastewater pretreatment method based on the wet oxidation method according to claim 3, wherein: In the filtration and removal of suspended particles, based on the superposition effect of pressure drop, describe the gradual interception of suspended particles by each layer of filter mesh; establish an accumulated resistance model, and analyze the filtration efficiency considering the comprehensive effect of multiple layers of filter mesh through the accumulated resistance model; where η filter is the multi-layer filtration efficiency; ΔP i is the pressure drop across the i-th layer of filter mesh; P in is the inlet pressure; m is the number of filter mesh layers.

5. A wastewater pretreatment method based on the wet oxidation method according to claim 4, wherein: By coupling the dual effects of time and temperature and introducing the reaction order to describe the degradation characteristics of different stages; the degradation characteristics include being sensitive to time in the first stage and sensitive to temperature in the second stage; A two-parameter kinetic model for the wet oxygen reaction degradation process is established based on the two-stage operation of the wet oxygen reactor; where C t , C0 are the pollutant concentrations at time t and the initial time respectively; k1, k2 are the influence coefficients of time and temperature on the reaction rate respectively; β1, β2 are the reaction orders of time and temperature respectively; t is the reaction time; T is the reaction temperature.

6. A wastewater pretreatment method based on the wet oxygen method according to claim 5, characterized in that: In the post-treatment and regulation of the oxidation liquid, the combined effect of chemical regulation and biological enhancement is reflected by coupling the synergistic effects of the surfactant dosage and pH, and a B / C ratio regulation model for the oxidation liquid is established by combining surfactant addition and oxidation enhancement: B / C new = (B / C orig + κC bio ) · (1 + θe -pH ) Among them, B / C new is the regulated B / C ratio; B / C orig is the original B / C ratio. κ is the surfactant strengthening coefficient; C bio is the dosage of surfactant; θ is the influence weight of pH on the regulated B / C ratio; -pH is the exponential decay factor of pH value on the regulation effect.

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