Efficient and environment-friendly method for treating wastewater through photo-Fenton oxidation

Abstract

The invention relates to the technical field of wastewater treatment, and discloses an efficient and environment-friendly photo-Fenton oxidation wastewater treatment method which comprises the following steps: performing primary treatment on wastewater through a water inlet and pretreatment unit to remove large-particle impurities; a flocculating agent is added through the flocculation treatment unit to further remove suspended solids; organic matters are efficiently degraded by utilizing ultraviolet light catalysis and a Fenton reagent through the photo-Fenton reaction unit; solid-liquid separation is realized through the separation and drainage unit, and wastewater is discharged after reaching the standard; system operation parameters are monitored in real time and automatically adjusted through the monitoring and control unit, and the treatment effect is ensured; large-recycle-ratio operation is achieved through the recycle-ratio control unit, the reaction efficiency is improved, and consumption of chemical reagents is reduced. According to the method, ultraviolet light catalysis and Fenton reaction are combined, efficient degradation of refractory organics in the wastewater is achieved, and meanwhile through the intelligent control and cyclic utilization technology, the treatment efficiency is improved, and the operation cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly to a method for efficiently and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater. Background Art

[0002] With the acceleration of the industrialization process, the amount of organic wastewater generated by various industrial activities has increased sharply, and these wastewaters contain a variety of refractory organic pollutants. Traditional wastewater treatment methods, such as biological treatment and physical filtration, have problems of low efficiency and incomplete treatment for treating organic wastewater with high concentration and complex composition. In addition, these methods may cause secondary pollution and cannot meet the increasingly strict environmental protection standards.

[0003] Existing wastewater treatment technologies, including chemical precipitation, biodegradation, and physical filtration, often require a long treatment time and have poor treatment effects on some refractory organic pollutants. For example, biological treatment methods are sensitive to microbial toxic substances in wastewater, and the treatment efficiency is easily affected by environmental conditions; physical filtration methods may require frequent maintenance due to clogging and wear problems.

[0004] In order to overcome the limitations of traditional wastewater treatment technologies, the photocatalytic Fenton oxidation technology has been proposed as an advanced oxidation process. This technology uses ultraviolet light to excite hydroxyl radicals generated by the Fenton reaction to effectively degrade organic matter in wastewater. However, the single photocatalytic Fenton oxidation technology has problems of low efficiency and high cost in practical applications, especially when treating high-concentration and complex wastewater.

[0005] In view of the limitations of single technologies in treating wastewater, it is necessary to develop a method for efficiently and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater. Summary of the Invention

[0006] The purpose of the present invention is to propose a method for efficiently and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater to solve the problems in the prior art.

[0007] To achieve the above purpose, the present invention adopts the following technical scheme: A method for efficiently and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater, comprising the following steps: S1: Continuously input the wastewater to be treated into the reaction tank through the wastewater inlet at the bottom of the reaction tank; S2: Add an acidic inorganic polymer flocculant to the bottom of the reaction tank through the acidic inorganic polymer flocculant dosing port, control the pH of the reaction system to 3.0 - 5.0, and perform preliminary flocculation; S3: Add a polymer flocculant to the bottom of the reaction tank through the polymer flocculant dosing port, stir and mix for 5 - 15 minutes, and after forming flocs, let it stand for sedimentation; S4: Turn on the ultraviolet lamp in the ultraviolet lamp sleeve in the reaction tank. The ultraviolet lamp can be divided into two types: ozone-free output at 254 nm or ozone output at 185 nm + 254 nm, with a power density of 50 - 200 W / m³, and continuously irradiate the reaction system; S5: Continuously inject ferrous solution and hydrogen peroxide into the reaction tank through the top ferrous dosing port and hydrogen peroxide dosing port respectively. The molar ratio of ferrous solution to hydrogen peroxide is 1:3 - 1:10, and the injection rate is 0.5 - 2.0 L / min; S6: Use the porous turbulence baffle at the bottom of the reaction tank to uniformly disturb the mixed liquid, promoting the full contact of ferrous, hydrogen peroxide and organic matter in the wastewater; S7: The trivalent iron ions generated by the reaction are reduced to divalent iron ions under ultraviolet light irradiation, and part of the reaction liquid is refluxed to the inlet pipe through the top overflow weir and hydrogen peroxide circulation pipe. The reflux flow rate is 3 - 10 times the inlet water flow rate, realizing the recycling of iron ions; S8: Achieve a large circulation ratio, and the ratio of circulating water flow rate to inlet water flow rate ≥ 10:1; S9: The treated wastewater is discharged through the wastewater discharge port, and the sludge is regularly discharged through the bottom sedimentation tank.

[0008] Furthermore, a system for high-efficiency and environmental-friendly photocatalytic Fenton oxidation treatment of wastewater is characterized by including: A monitoring and control unit for monitoring the parameters during the treatment process through sensors and automatically adjusting the system operation parameters according to the monitoring data; An inlet water and pretreatment unit for automatically adjusting the wastewater flow rate through real-time monitoring data and preliminarily treating the incoming wastewater; A flocculation treatment unit for removing part of the organic matter and suspended solids in the wastewater through a chemical flocculation process; A photocatalytic Fenton reaction unit for efficiently degrading the organic matter in the wastewater through ultraviolet light excitation and Fenton synergy reaction; A circulation ratio control unit for refluxing part of the treated wastewater to the inlet pipe and monitoring and adjusting the flow rate of the circulating water to achieve a ratio of circulating water flow rate to inlet water flow rate ≥ 10:1; A separation and drainage unit for settling the solid particles in the treated wastewater and discharging them regularly.

[0009] The beneficial effects brought by the technical solution provided by the present invention at least include: The method of the present invention significantly improves the treatment efficiency of wastewater by integrating the steps of flocculation, photocatalytic Fenton reaction and iron ion recycling, can degrade the organic matter in the wastewater faster, and shorten the treatment cycle.

[0010] The present invention reduces the usage of chemical reagents and energy consumption through an automated control system and precise dosing of chemical reagents, thereby reducing the overall treatment cost.

[0011] The present invention produces less chemical sludge during the treatment process and is easy to handle, effectively reducing the risk of secondary pollution and meeting the requirements of modern environmental protection.

[0012] The present invention can effectively degrade the organic matter in wastewater, significantly improving the quality of the treated wastewater, meeting more stringent discharge standards, and contributing to environmental protection and water resources conservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0014] Figure 1 It is a flowchart of the method provided by the embodiment of the present invention; Figure 2 It is a schematic diagram of the system composition provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation manner, structure, features, and effects of a method for treating wastewater by high-efficiency and environmentally friendly photo-Fenton oxidation proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0017] The following embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0018] The following specifically describes the specific solution of a method for treating wastewater by high-efficiency and environmentally friendly photo-Fenton oxidation provided by the present invention with reference to the accompanying drawings.

[0019] Please refer to Figure 1 , which shows a flowchart of a method for treating wastewater by high-efficiency and environmentally friendly photo-Fenton oxidation provided by an embodiment of the present invention. The method includes the following steps: S1: Continuously input the wastewater to be treated into the reaction tank through the wastewater inlet at the bottom of the reaction tank; It should be noted that for the location of the wastewater inlet: Selecting the bottom of the reaction tank as the wastewater inlet can utilize the gravitational force to evenly distribute the wastewater and avoid directly impacting the treated wastewater or flocs in the reaction tank.

[0020] Continuous input: Adopt a continuous input method to ensure the stability of the treatment process and avoid fluctuations in the treatment effect caused by intermittent input.

[0021] S2: Add an acidic inorganic polymer flocculant to the bottom of the reaction tank through the acidic inorganic polymer flocculant dosing port, control the pH of the reaction system to 3.0 - 5.0, and conduct preliminary flocculation; It should be noted that for the type of flocculant: Select an acidic inorganic polymer flocculant, which has good charge neutralization and adsorption bridging effects and can effectively agglomerate fine particles in the wastewater.

[0022] pH control: Control the pH value of the reaction system to 3.0 - 5.0. This acidic environment is conducive to the full play of the flocculant and provides suitable pH conditions for the subsequent Fenton reaction.

[0023] Preliminary flocculation: After adding the flocculant, promote the full contact between the flocculant and the particles in the wastewater through means such as stirring to form larger flocs, which is convenient for subsequent sedimentation and separation.

[0024] S3: Add a polymer flocculant to the bottom of the reaction tank through the polymer flocculant dosing port, stir and mix for 5 - 15 minutes, and then let it stand for sedimentation after forming flocs; It should be noted that for the characteristics of the polymer flocculant: The polymer flocculant has a long molecular chain and can connect fine particles into larger flocs through adsorption bridging to improve the sedimentation efficiency.

[0025] Stirring and mixing: Control the stirring time to 5 - 15 minutes to ensure the full contact and reaction between the flocculant and the particles in the wastewater and form stable flocs.

[0026] Static sedimentation: Let it stand after stirring to precipitate the flocs, achieve solid-liquid separation, and provide clearer wastewater for the subsequent photo-Fenton reaction.

[0027] S4: Turn on the ultraviolet lamp in the ultraviolet lamp sleeve in the reaction tank. The ultraviolet lamp can be divided into two types: 254 nm ozone-free output or 185 nm + 254 nm ozone output, with a power density of 50 - 200 W / m³, and continuously irradiate the reaction system; It should be noted that the types of ultraviolet lamps: Ultraviolet lamps can be divided into two categories: those with ozone-free output at 254 nm or ozone output at 185 nm + 254 nm. The 254-nm ultraviolet light mainly generates reactive oxygen through photolysis, while the 185-nm ultraviolet light can generate ozone to further enhance the oxidation ability.

[0028] Power density: The power density of the ultraviolet lamp is 50 - 200 W / m³. Select an appropriate power according to the nature and treatment requirements of the wastewater to ensure sufficient energy output.

[0029] Continuous irradiation: The ultraviolet lamp continuously irradiates the reaction system to ensure the continuous progress of the Fenton reaction and simultaneously degrade organic matter using the strong oxidizing property of ultraviolet light.

[0030] S5: Continuously inject ferrous solution and hydrogen peroxide into the reaction tank through the top ferrous dosing port and hydrogen peroxide dosing port respectively. The molar ratio of the ferrous solution to hydrogen peroxide is 1:3 - 1:10, and the injection rate is 0.5 - 2.0 L / min; It should be noted that the dosing ratio of the agents: The molar ratio of the ferrous solution to hydrogen peroxide is 1:3 - 1:10. This ratio range can ensure the efficient progress of the Fenton reaction and avoid adverse effects on the reaction system caused by excessive ferrous or hydrogen peroxide.

[0031] Injection rate: The injection rate is 0.5 - 2.0 L / min. Adjust the injection rate according to the flow rate and treatment requirements of the wastewater to ensure an appropriate concentration of the agents in the reaction system.

[0032] Continuous injection: Adopt a continuous injection method to ensure the continuous progress of the Fenton reaction and avoid reaction interruption caused by intermittent injection.

[0033] S6: Use the porous turbulence baffle at the bottom of the reaction tank to uniformly disturb the mixed liquid, promoting the full contact of ferrous, hydrogen peroxide and organic matter in the wastewater; It should be noted that the design of the porous turbulence baffle: The porous turbulence baffle can generate local eddies, enabling the full mixing of the agents and organic matter in the mixed liquid and improving the reaction rate.

[0034] Uniform disturbance: Through the design of the porous turbulence baffle, achieve uniform disturbance of the mixed liquid, avoiding insufficient local reaction or overreaction.

[0035] S7: The trivalent iron ions generated by the reaction are reduced to divalent iron ions under ultraviolet light irradiation, and part of the reaction liquid is refluxed to the inlet pipe through the top overflow weir and hydrogen peroxide circulation pipe. The reflux flow rate is 3 - 10 times the inflow rate to achieve the recycling of iron ions; It should be noted that the reduction of iron ions: Under ultraviolet light irradiation, trivalent iron ions can be reduced to divalent iron ions and participate in the Fenton reaction again.

[0036] Circulating reflux: Part of the reaction liquid is refluxed to the water inlet pipe through the top overflow weir and the hydrogen peroxide circulation pipe to realize the recycling of iron ions and maintain the stability of the reaction system at the same time.

[0037] Control of reflux flow rate: The reflux flow rate is 3 - 10 times the water inlet flow rate. Adjust the reflux flow rate according to the actual treatment requirements to ensure the recycling efficiency of iron ions.

[0038] S8: Achieve a large circulation ratio, and the ratio of the circulating water flow rate to the water inlet flow rate ≥ 10:1; It should be noted that for the control of the circulation ratio: Through the circulation ratio control unit, the circulating water flow rate and the water inlet flow rate are monitored in real time, and the circulation ratio is automatically adjusted to ensure that the ratio ≥ 10:1.

[0039] Circulating water flow rate: The increase in the circulating water flow rate can improve the mixing effect and reaction rate of the reaction system, and reduce the consumption of chemical reagents at the same time.

[0040] S9: The treated wastewater is discharged through the wastewater discharge port, and the sludge is regularly discharged through the bottom sedimentation tank.

[0041] It should be noted that for the wastewater discharge: The treated wastewater is discharged from the system through the wastewater discharge port to ensure that its water quality meets the discharge standards.

[0042] Sludge discharge: The sludge is regularly discharged through the bottom sedimentation tank to avoid the accumulation of sludge in the reaction tank and affect the treatment effect.

[0043] Please refer to Figure 2 It is a schematic diagram of the system composition of a system for highly efficient and environmentally friendly photo-Fenton oxidation treatment of wastewater provided by an embodiment of the present invention. In the embodiment of the present invention, a system for highly efficient and environmentally friendly photo-Fenton oxidation treatment of wastewater is provided, including: A monitoring and control unit, used to monitor the parameters during the treatment process through sensors and automatically adjust the system operation parameters according to the monitoring data; An inlet water and pretreatment unit, used to automatically adjust the wastewater flow rate through real-time monitoring data and conduct preliminary treatment on the incoming wastewater; A flocculation treatment unit, used to remove part of the organic matter and suspended solids in the wastewater through a chemical flocculation process; A photo-Fenton reaction unit, used to efficiently degrade the organic matter in the wastewater through the synergistic reaction of ultraviolet light excitation and Fenton; A circulation ratio control unit, used to reflux part of the treated wastewater to the water inlet pipe, monitor and adjust the flow rate of the circulating water, and achieve a ratio of the circulating water flow rate to the water inlet flow rate ≥ 10:1; A separation and drainage unit, used to settle the solid particles in the treated wastewater and conduct regular discharge.

[0044] I. Monitoring and Control Unit The monitoring and control unit includes a real-time monitoring module, a historical monitoring module, and a control module; The real-time monitoring module uses sensors to monitor the parameters during the real-time processing. The sensors include pH electrodes, temperature sensors, pressure sensors, dissolved oxygen probes, photoelectric colorimeters, ammonia nitrogen sensors, conductivity meters, ORP electrodes, flow meters, sludge concentration meters, and ultraviolet light intensity meters. The parameters include pH value, temperature, pressure, dissolved oxygen, COD, BOD, ammonia nitrogen, suspended solids, conductivity, oxidation-reduction potential, flow rate, sludge concentration, and ultraviolet light intensity; The historical monitoring module includes a data collection and storage mechanism for storing the data collected during the monitoring process and can preserve historical data for a long time; The control module realizes automatic control through the PLC system and can automatically adjust the system operation parameters according to the real-time monitoring data and the preset program.

[0045] It should be noted that the pH electrode: is used to measure the acidity and alkalinity (pH value) of the wastewater to ensure that the reaction system is in a suitable acidic environment (the pH value of the photo-Fenton reaction is usually between 3.0 and 5.0).

[0046] The temperature sensor: monitors the temperature in the reaction tank to ensure that the reaction proceeds within a suitable temperature range.

[0047] The pressure sensor: measures the pressure in the system to prevent damage to the equipment caused by too high or too low pressure.

[0048] The dissolved oxygen probe: monitors the dissolved oxygen content in the water, which is particularly important for biological treatment processes or reactions that require control of oxidation-reduction conditions.

[0049] The photoelectric colorimeter: is used to measure the chemical oxygen demand (COD) or biochemical oxygen demand (BOD) to evaluate the pollution degree of the wastewater.

[0050] The ammonia nitrogen sensor: monitors the ammonia nitrogen content in the wastewater, which is particularly important for the treatment of nitrogen-containing wastewater.

[0051] The conductivity meter: measures the conductivity of the water to indirectly reflect the content of dissolved solids in the water.

[0052] The ORP electrode (oxidation-reduction potential electrode): monitors the oxidation-reduction potential in the water to ensure that the reaction system is in a suitable oxidation-reduction state.

[0053] The flow meter: measures the flow rate of the wastewater to ensure the continuous and stable operation of the system.

[0054] The sludge concentration meter: monitors the sludge concentration to facilitate the timely discharge of sludge and prevent sludge accumulation.

[0055] Ultraviolet light intensity meter: Monitor the output intensity of the ultraviolet lamp to ensure that the intensity of the ultraviolet light meets the reaction requirements.

[0056] pH value: Monitor the acidity and alkalinity of the wastewater to ensure that the reaction system is within the appropriate pH range (such as the acidic conditions of the Fenton reaction).

[0057] Temperature: Monitor the temperature in the reaction tank to ensure that the reaction proceeds at an appropriate temperature and avoid the influence of too high or too low temperature on the reaction rate.

[0058] Pressure: Monitor the pressure in the system to ensure the safe operation of the equipment and avoid equipment damage caused by too high pressure.

[0059] Dissolved oxygen (DO): Monitor the content of dissolved oxygen in water, which is very important for biological treatment units (if any in the follow-up).

[0060] COD and BOD: Monitor the organic matter content of the wastewater and evaluate the treatment effect.

[0061] Ammonia nitrogen: Monitor the ammonia nitrogen content in the wastewater to ensure its up-to-standard discharge.

[0062] Suspended solids (SS): Monitor the suspended solids content in the wastewater and evaluate the flocculation and precipitation effects.

[0063] Conductivity (EC): Monitor the conductivity of the wastewater and indirectly reflect the content of dissolved solids in water.

[0064] Oxidation-reduction potential (ORP): Monitor the oxidation-reduction state of the reaction system to ensure the efficient progress of the Fenton reaction.

[0065] Flow rate: Monitor the flow rate of the wastewater in the reaction tank to ensure its uniform distribution and sufficient mixing.

[0066] Sludge concentration: Monitor the sludge concentration in the sedimentation tank to provide a basis for sludge discharge.

[0067] Ultraviolet light intensity: Monitor the output intensity of the ultraviolet lamp to ensure its normal operation and provide sufficient energy for the photo-Fenton reaction.

[0068] Data storage mechanism: Adopt high-capacity and high-reliability storage devices, such as industrial-grade hard disks or cloud storage services, to ensure the safe storage of historical data.

[0069] Data storage format: Support multiple data storage formats, including CSV, Excel, and databases, to facilitate data interaction with other software or systems.

[0070] PLC system: Adopt a high-performance PLC controller with powerful data processing capabilities and logic control capabilities, capable of implementing complex automation control functions.

[0071] II. Inlet and Pretreatment Unit The inlet and pretreatment unit includes an inlet flow control module and a wastewater pretreatment module; The inlet flow control module includes a flow sensor and an automatic regulating valve. The flow of wastewater can be monitored in real time through the flow sensor, and the flow can be automatically adjusted according to the monitoring data through the automatic regulating valve to control the flow of wastewater entering the reaction tank; The wastewater pretreatment module is used for the preliminary treatment of wastewater. Large particulate matter and suspended solids are removed through pretreatment equipment, and the pretreatment equipment includes a grille and a grit chamber.

[0072] It should be noted that for the flow sensor: an electromagnetic flowmeter or an ultrasonic flowmeter is adopted. The sensor has the characteristics of high precision, high reliability and non-contact measurement, and is applicable to various water quality conditions.

[0073] Installation location: The flow sensor is installed on the wastewater inlet pipe to monitor the flow of wastewater in real time.

[0074] Measurement range: Select a suitable measurement range according to the flow demand of the wastewater treatment system, for example, 0 - 100 m³ / h.

[0075] The automatic regulating valve: an electric regulating valve or a pneumatic regulating valve is adopted, which can automatically adjust the valve opening according to the signal of the flow sensor.

[0076] Control mode: The PLC system receives the signal of the flow sensor, calculates the deviation between the actual flow and the set flow, and adjusts the opening of the regulating valve according to the deviation.

[0077] Response speed: The response speed of the regulating valve should be fast enough to ensure the rapid adjustment of the flow, and the response time is within 1 - 5 seconds.

[0078] The grille: Coarse grille and fine grille are adopted. The coarse grille is used to remove larger floating objects and solid wastes (such as branches, plastic bags, etc.), and the fine grille is used to remove smaller suspended solids (such as fibers, sand grains).

[0079] Installation location: The grille is installed at the wastewater inlet, and the wastewater first passes through the grille for preliminary filtration.

[0080] Clearance size: The clearance of the coarse grille is usually 10 - 50 mm, and the clearance of the fine grille is 1 - 10 mm. The specific clearance size is selected according to the nature and treatment requirements of the wastewater.

[0081] The grit chamber: A horizontal flow grit chamber or a vortex grit chamber is adopted to remove sand grains and inorganic suspended solids such as soil in the wastewater.

[0082] Working principle: By controlling the water flow rate, the heavy solid particles in the wastewater settle to the bottom, thus achieving solid-liquid separation.

[0083] III. Flocculation treatment unit The flocculation treatment unit includes a flocculant dosing module and a flocculation treatment module; The flocculant dosing module includes a precision metering pump and an automatic control system. The flocculant is added to the wastewater through the precision metering pump, and the dosing amount is automatically adjusted according to the treatment requirements of the wastewater through the automatic control system. The dosing amount calculation formula of the flocculant is: Wherein, is the dosing amount of the flocculant, is the target flocculant concentration, is the wastewater flow rate, is the effective utilization rate of the flocculant; The flocculation treatment module promotes the full reaction of the flocculant with the substances in the wastewater through a stirring and mixing device to form flocs that are easy to settle. The sedimentation velocity formula of the flocs is: Wherein, v is the sedimentation velocity of the flocs, r is the radius of the floc particles, g is the acceleration due to gravity, floc particle density, is the wastewater density, is the dynamic viscosity of the wastewater.

[0084] It should be noted that the precision metering pump: uses a diaphragm metering pump or a plunger metering pump, which can provide high-precision flow control to ensure the accurate dosing amount of the flocculant.

[0085] Flow range: Select a suitable flow range according to the scale of the wastewater treatment system and the usage amount of the flocculant, such as 0.1 - 10 L / h.

[0086] Accuracy: The flow accuracy of the metering pump is usually within ±1%, which can meet the requirements of high-precision dosing.

[0087] Automatic control system: According to the preset control strategy and real-time monitoring data, automatically adjust the rotation speed or stroke of the metering pump, thereby adjusting the dosing amount of the flocculant.

[0088] Feedback mechanism: Realize the dynamic adjustment of the dosing amount through a feedback control algorithm (PID control) to ensure that the dosing amount of the flocculant matches the treatment requirements of the wastewater.

[0089] Stirring and mixing device: Adopts a mechanical stirrer or a pneumatic stirrer. The mechanical stirrer drives the stirring blades to rotate through an electric motor, and the pneumatic stirrer drives the stirring device through compressed air.

[0090] Mixing method: Select a suitable mixing method according to the properties of the wastewater and the characteristics of the flocculant, including low-speed mixing or high-speed mixing. Low-speed mixing is suitable for the preliminary mixing of the flocculant, and high-speed mixing is suitable for the rapid dispersion of the flocculant.

[0091] Mixing intensity: The mixing intensity should be moderate. It is necessary to ensure the full mixing of the flocculant and the wastewater, and at the same time avoid excessive mixing resulting in the breakage of flocs. The mixing intensity is usually controlled by the rotation speed and the shape of the mixing paddle blades.

[0092] Mixing time: The mixing time is usually 5 - 15 minutes, and the specific time is determined according to the properties of the wastewater and the reaction rate of the flocculant.

[0093] Reaction tank design: Use a horizontal flow reaction tank or a baffled flow reaction tank. The horizontal flow reaction tank has a stable water flow, and the baffled flow reaction tank can increase the turbulence of the water flow and promote the flocculation reaction.

[0094] Tank body size: Design the size of the reaction tank according to the flow rate of the wastewater and the mixing time to ensure that the wastewater has sufficient residence time in the reaction tank.

[0095] Floc formation: Through reasonable mixing and reaction tank design, enable the flocculant to fully react with the substances in the wastewater to form flocs that are easy to settle.

[0096] IV. Photo-Fenton reaction unit The photo-Fenton reaction unit includes an ultraviolet catalytic module, a reagent catalytic module, a separation module, and an iron ion recycling module; The ultraviolet catalytic module is used to provide ultraviolet light for catalysis. Specific wavelength ultraviolet light is provided through an ultraviolet lamp device. The ultraviolet lamp has an adjustable power output and can adapt to the needs of different wastewater treatments.

[0097] The reagent catalytic module is used to add a catalyst to promote the Fenton reaction. The dosing amount and time of the catalyst are controlled by a dosing pump. The catalyst can maximize the generation of hydroxyl radicals; The separation module is used to separate the components after the reaction and achieve the effective separation of the reaction products. Solids and liquids are separated through a filter according to the physical properties of the reaction products. The physical properties include solubility, density, and particle size distribution.

[0098] The iron ion recycling module is used to recycle iron ions through a circulation pump to reduce the consumption of chemical reagents.

[0099] It should be noted that wavelength selection: The wavelength of the ultraviolet lamp is usually 254 nm (without ozone output) or 185 nm + 254 nm (with ozone output). The 254 nm ultraviolet light is mainly used to stimulate the Fenton reaction, and the 185 nm ultraviolet light can generate ozone to further enhance the oxidation ability.

[0100] Power adjustment: The ultraviolet lamp has an adjustable power output, with a power density range of 50 - 200 W / m³. According to the nature of the wastewater and the treatment requirements, the power of the ultraviolet lamp can be dynamically adjusted to optimize the reaction efficiency.

[0101] Lamp life: The service life of the ultraviolet lamp is usually several thousand hours, and the specific life depends on the quality of the lamp tube and the usage environment.

[0102] Catalyst selection: Ferrous ions (Fe²⁺) are used as the catalyst, which can react with hydrogen peroxide (H2O2) to generate strongly oxidizing hydroxyl radicals (·OH), thereby degrading the organic matter in the wastewater.

[0103] Dosage: According to the nature of the wastewater and the treatment requirements, the optimal dosage of the catalyst is determined through experiments. The molar ratio of ferrous ions to hydrogen peroxide is 1:3 - 1:10.

[0104] Dosing pump: A high-precision metering pump is used, which can accurately control the dosage and dosing time of the catalyst.

[0105] Filter: A sand filter, activated carbon filter or membrane filter is used, and a suitable filtering medium is selected according to the physical properties of the reaction products.

[0106] Separation principle: Through the pore structure of the filter, separation is carried out according to the solubility, density and particle size distribution of the reaction products. Solid particles are retained in the filter, while the liquid passes through the filter and is discharged.

[0107] Circulation pump: A corrosion-resistant centrifugal pump or diaphragm pump is used, which can return part of the reacted liquid (containing iron ions) to the inlet pipe of the reaction tank.

[0108] Circulation ratio: The return flow is usually 3 - 10 times the influent flow. The specific circulation ratio is optimized according to the nature of the wastewater and the treatment requirements.

[0109] V. Circulation ratio control unit The circulation ratio control unit includes a circulation flow control module and a circulation ratio adjustment module; The circulation flow control module includes a circulation pump and a flow meter. The flow of the circulating water is measured in real time through the flow meter, and the flow in the circulating water is adjusted and controlled through the circulation pump; The circulation ratio adjustment module is used to automatically adjust the circulation flow according to the influent flow. Through intelligent control algorithms, based on the preset circulation ratio target and real-time monitoring data, the operating parameters of the circulation pump are automatically adjusted. The operating parameters include the pump speed, operating time, intermittent circulation and pump power.

[0110] It should be noted that the circulation pump: A corrosion-resistant centrifugal pump or diaphragm pump is used, which can adapt to the chemical properties and flow requirements of the wastewater.

[0111] Flow meter: An electromagnetic flow meter or a vortex flow meter is adopted, which features high precision, high reliability and non-contact measurement, and is suitable for various water quality conditions.

[0112] Installation location: The flow meter is installed on the circulating water pipeline to measure the flow rate of the circulating water in real time.

[0113] Measurement range: Select an appropriate measurement range according to the designed flow rate of the system, such as 0 - 100 m³ / h.

[0114] Intelligent control algorithm: The PID control algorithm is adopted. According to the real-time monitored inlet water flow rate and circulating water flow rate, the operating parameters of the circulating pump are automatically calculated and adjusted.

[0115] Parameter optimization: Through experiments and data analysis, optimize the parameters (proportional, integral, derivative) of the PID control algorithm to achieve the best control effect.

[0116] Pump speed: Adjust the speed of the circulating pump through a frequency converter to change the flow rate of the circulating water.

[0117] Operating time: Automatically adjust the operating time of the circulating pump according to the real-time monitored data to ensure the stability of the circulation ratio.

[0118] Intermittent circulation: In some cases, the circulating pump can adopt an intermittent operation mode, and the PLC system is used to control the time interval of its operation and stop.

[0119] Pump power: Adjust the power output of the circulating pump according to the actual demand to optimize energy consumption and operating efficiency.

[0120] VI. Separation and Drainage Unit The separation and drainage unit includes a precipitation module, a wastewater discharge module and a sludge discharge module; Precipitation module, used to precipitate solid particles in the wastewater. The precipitation process of solid particles in the wastewater is realized through a sedimentation tank, and the sedimentation efficiency can be changed by adjusting the sedimentation tank parameters. The sedimentation tank parameters include the depth, shape and surface load of the sedimentation tank. The sedimentation efficiency calculation formula of the sedimentation tank is: Among them, is the sedimentation efficiency of the sedimentation tank, is the inlet water flow rate, is the outlet water flow rate, is the suspended solid concentration of the inlet water, is the suspended solid concentration of the outlet water; Wastewater discharge module, including a flow control valve and a height adjustment device for the discharge port, discharges the treated wastewater meeting the discharge standards through the flow control valve, and avoids impacting the receiving water body through the height adjustment device of the discharge port; Sludge discharge module, including a sludge pump and a centrifuge, is used to discharge the precipitated sludge. The sludge at the bottom of the sedimentation tank is discharged through the sludge pump, and the sludge is concentrated and dewatered by the centrifuge to reduce the sludge volume and increase the solid content. The sludge production calculation formula is: Wherein, is the sludge production, is the wastewater flow rate, is the suspended solid concentration of the influent, is the removal rate of suspended solids, is the solid concentration of the sludge.

[0121] It should be noted that for the sedimentation tank design: a horizontal flow sedimentation tank, a vertical flow sedimentation tank or a radial flow sedimentation tank is adopted. The horizontal flow sedimentation tank has stable water flow and is suitable for large-flow wastewater treatment; the vertical flow sedimentation tank has a small floor area and is suitable for occasions with limited space; the radial flow sedimentation tank is suitable for treating wastewater containing a large amount of suspended solids.

[0122] Sedimentation tank depth: Select a suitable sedimentation tank depth according to the wastewater flow rate and the sedimentation velocity of solid particles, usually between 2 - 5 meters.

[0123] Sedimentation tank shape: The shape of the sedimentation tank should be conducive to the stable flow of water and the sedimentation of solid particles. The shapes include rectangular, circular and polygonal.

[0124] Surface loading: Surface loading refers to the wastewater flow rate passing through the unit sedimentation tank surface area per unit time, usually between 0.5 - 2.0 m³ / (m²·h). The lower the surface loading, the better the sedimentation effect, but the floor area of the sedimentation tank will increase.

[0125] Flow control valve: An electric control valve or a pneumatic control valve is adopted, which can automatically adjust the valve opening according to the instructions of the PLC system to control the discharge flow rate of the wastewater.

[0126] Control method: Receive real-time monitoring data (flow sensor, water quality sensor) through the PLC system, and automatically adjust the opening of the flow control valve according to the preset discharge standards.

[0127] Discharge port height adjustment device: An adjustable-height discharge pipe or overflow weir is adopted, which can automatically adjust the height of the discharge port according to the water level change of the receiving water body.

[0128] Adjustment method: The lifting of the discharge port height adjustment device is controlled by the PLC system to ensure the smoothness and uniformity of wastewater discharge and avoid impacting the receiving water body.

[0129] Sludge pump: A screw pump or a diaphragm pump is adopted, which has good corrosion resistance and high conveying efficiency and is suitable for conveying high-concentration sludge.

[0130] Centrifuge: A horizontal screw centrifuge or a plate and frame filter press is adopted. The horizontal screw centrifuge is suitable for continuous operation, and the plate and frame filter press is suitable for intermittent operation.

[0131] Working principle: The centrifuge separates the solid particles from the liquid in the sludge through the centrifugal force generated by high-speed rotation, realizing the concentration and dehydration of the sludge.

[0132] Sludge concentration: The water in the sludge is removed through the centrifuge to increase the solid content of the sludge and reduce the volume of the sludge.

[0133] Sludge dehydration: Further, the water in the sludge is squeezed out through centrifugal force to make the sludge reach a state that can be transported and disposed of. The above-described embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application and should all be included within the protection scope of the present application.

Claims

1. A method for treating wastewater by efficient and environmentally friendly photo-Fenton oxidation, characterized in that, The method includes: S1: Continuously input the wastewater to be treated into the reaction tank through the wastewater inlet at the bottom of the reaction tank; S2: Add an acidic inorganic polymer flocculant to the bottom of the reaction tank through the acidic inorganic polymer flocculant dosing port, control the pH of the reaction system to be 3.0 - 5.0, and conduct preliminary flocculation; S3: Add a polymer flocculant to the bottom of the reaction tank through the polymer flocculant dosing port, stir and mix for 5 - 15 minutes, and let it stand for sedimentation after forming flocs; S4: Turn on the ultraviolet lamp in the ultraviolet lamp sleeve in the reaction tank. The ultraviolet lamp is divided into two types: 254 nm ozone-free output or 185 nm + 254 nm ozone output, with a power density of 50 - 200 W / m², and continuously irradiate the reaction system; S5: Continuously inject a ferrous solution and hydrogen peroxide into the reaction tank through the top ferrous dosing port and the hydrogen peroxide dosing port respectively. The molar ratio of the ferrous solution to hydrogen peroxide is 1:3 - 1:10, and the injection rate is 0.5 - 2.0 L / min; S6: Use the porous turbulence baffle at the bottom of the reaction tank to uniformly disturb the mixed liquid to promote the full contact of ferrous, hydrogen peroxide and the organic matter in the wastewater; S7: The trivalent iron ions generated by the reaction are reduced to divalent iron ions under ultraviolet light irradiation, and part of the reaction liquid is refluxed to the inlet pipe through the top overflow weir and the hydrogen peroxide circulation pipe. The reflux amount is 3 - 10 times the water inflow amount to realize the recycling of iron ions; S8: Achieve a large circulation ratio, and the ratio of the circulating water flow rate to the inlet water flow rate ≥ 10:1; S9: The treated wastewater is discharged through the wastewater discharge port, and the sludge is regularly discharged through the bottom sedimentation tank.

2. A system for efficiently and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater, characterized in that, It includes: A monitoring and control unit for monitoring the parameters in the treatment process through sensors and automatically adjusting the system operation parameters according to the monitoring data; An inlet and pretreatment unit for automatically adjusting the wastewater flow rate according to the real-time monitoring data and preliminarily treating the incoming wastewater; A flocculation treatment unit for removing part of the organic matter and suspended solids in the wastewater through a chemical flocculation process; A photo-Fenton reaction unit for efficiently degrading the organic matter in the wastewater through ultraviolet light excitation and Fenton synergistic reaction; A circulation ratio control unit for refluxing part of the treated wastewater to the inlet pipe, monitoring and adjusting the flow rate of the circulating water, and achieving a ratio of the circulating water flow rate to the inlet water flow rate ≥ 10:1; A separation and drainage unit for sedimenting the solid particles in the treated wastewater and discharging them regularly.

3. The system for highly efficient and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater according to claim 2, wherein The monitoring and control unit includes: A real-time monitoring module that realizes real-time monitoring of the parameters in the treatment process through sensors. The sensors include a pH electrode, a temperature sensor, a pressure sensor, a dissolved oxygen probe, a photoelectric colorimeter, an ammonia nitrogen sensor, a conductivity meter, an ORP electrode, a flow meter, a sludge concentration meter, and an ultraviolet light intensity meter. The parameters include pH value, temperature, pressure, dissolved oxygen, COD, BOD, ammonia nitrogen, suspended solids, conductivity, redox potential, flow rate, sludge concentration, and ultraviolet light intensity; A historical monitoring module including a data collection and storage mechanism for storing the data collected during the monitoring process and capable of long-term preservation of historical data; The control module realizes automatic control through the PLC system and can automatically adjust the system operation parameters according to the real-time monitoring data and preset programs.

4. The system for efficiently and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater according to claim 2, characterized in that, The inlet and pretreatment unit includes: The inlet flow control module, including a flow sensor and an automatic regulating valve, can monitor the flow rate of wastewater in real time through the flow sensor, and can automatically adjust the flow rate according to the monitoring data through the automatic regulating valve to control the flow rate of wastewater entering the reaction tank; The wastewater pretreatment module is used for preliminary treatment of wastewater. Large particulate matter and suspended solids are removed through pretreatment equipment, and the pretreatment equipment includes a grille and grit chamber.

5. The system for highly efficient and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater according to claim 2, wherein, The flocculation treatment unit includes: The flocculant dosing module, including a precise metering pump and an automatic control system, adds flocculant to the wastewater through the precise metering pump, and automatically adjusts the dosing amount according to the treatment requirements of the wastewater through the automatic control system. The calculation formula for the dosing amount of the flocculant is: Among them, is the dosage of the flocculant, is the concentration of the target flocculant, is the wastewater flow rate, is the effective utilization rate of the flocculant; The flocculation treatment module promotes the full reaction between the flocculant and the substances in the wastewater through a stirring and mixing device to form flocs that are easy to settle. The sedimentation velocity formula of the flocs is: where v is the floc sedimentation velocity, r is the floc particle radius, g is the acceleration due to gravity, the density of the floc particles, is the density of the wastewater, and is the dynamic viscosity of the wastewater.

6. The system for efficiently and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater according to claim 2, characterized in that, The photo-Fenton reaction unit includes: The ultraviolet catalytic module is used to provide ultraviolet light for catalysis. Ultraviolet light of a specific wavelength is provided through an ultraviolet lamp device, and the ultraviolet lamp has an adjustable power output to adapt to the needs of different wastewater treatments; The reagent catalytic module is used to add a catalyst to promote the Fenton reaction. The dosing amount and time of the catalyst are controlled by a dosing pump, and the catalyst can maximize the generation of hydroxyl radicals; The separation module is used to separate the components after the reaction to effectively separate the reaction products. Solids and liquids are separated through a filter according to the physical properties of the reaction products, and the physical properties include solubility, density, and particle size distribution; The iron ion recycling module is used to recycle iron ions through a circulation pump to reduce the consumption of chemical reagents.

7. The system for highly efficient and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater according to claim 2, characterized in that, The recycle ratio control unit includes: The recycle flow control module, including a circulation pump and a flow meter, measures the flow rate of the circulating water in real time through the flow meter, and adjusts and controls the flow rate in the circulating water through the circulation pump; The recycle ratio adjustment module is used to automatically adjust the recycle flow rate according to the inlet flow rate. Through an intelligent control algorithm, according to the preset recycle ratio target and real-time monitoring data, the operation parameters of the circulation pump are automatically adjusted, and the operation parameters include the pump speed, operation time, intermittent circulation, and power.

8. The system for efficient and environmentally friendly photocatalytic Fenton oxidation treatment of wastewater according to claim 2, wherein The separation and drainage unit includes: The precipitation module is used to precipitate solid particles in the wastewater. The precipitation process of solid particles in the wastewater is realized through a sedimentation tank, and the sedimentation efficiency can be changed by adjusting the sedimentation tank parameters. The sedimentation tank parameters include the depth, shape, and surface loading of the sedimentation tank. The calculation formula for the sedimentation efficiency of the sedimentation tank is: Among them, is the sedimentation efficiency of the sedimentation tank, is the influent flow rate, is the effluent flow rate, is the suspended solid concentration of the influent, is the suspended solid concentration of the effluent; The wastewater discharge module, including a flow control valve and a height adjustment device for the discharge port, discharges the treated wastewater that meets the discharge standards from the system through the flow control valve, and avoids impacting the receiving water body through the height adjustment device of the discharge port; Sludge discharge module, including a sludge pump and a centrifuge, is used to discharge the precipitated sludge. The sludge at the bottom of the sedimentation tank is discharged through the sludge pump, and the sludge is concentrated and dehydrated by the centrifuge to reduce the sludge volume and increase the solid content. The calculation formula for the output of the sludge is as follows: Among them, is the sludge production, is the wastewater flow rate, is the suspended solid concentration of the influent water, is the removal rate of suspended solids, is the solid concentration of the sludge.

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