Wastewater treatment method in carton printing production process

Abstract

The invention relates to the technical field of industrial wastewater treatment, and discloses a wastewater treatment method in a carton printing production process, which comprises the following steps of: 1, filtering carton printing wastewater through a coarse grid and a fine grid in sequence to further remove particle suspended matters; 2, the filtered wastewater enters a regulating tank, the pH value of the wastewater is monitored through an on-line pH sensor, NaOH or H2SO4 is accurately added through an automatic control system according to the monitoring result, the pH value is regulated to 6-8, and the retention time of the wastewater in the regulating tank is controlled to be 6-8 h. Through multi-stage grid filtration and micro-electrolysis pretreatment, suspended particles and macromolecular organic matters in the wastewater are effectively removed, the load of a subsequent unit is reduced, meanwhile, the biodegradability of the wastewater is improved, favorable conditions are provided for subsequent biological treatment, the overall treatment efficiency is remarkably improved, and the risks of system blockage and equipment maintenance are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment, and in particular to a method for treating wastewater in a carton printing production process. Background Art

[0002] Wastewater is generated during the carton printing production process. The wastewater usually contains organic substances such as ink, adhesives, coatings, cleaning agents, and pollutants with high chromaticity. This type of wastewater has high chemical oxygen demand and biological oxygen demand, contains suspended matter and difficult-to-degrade organic matter, and will cause serious pollution to the environment if it is discharged directly without treatment. The composition of wastewater is complex and the concentration of pollutants is high. The traditional single treatment process cannot effectively remove all pollutants, especially ink particles and difficult-to-degrade organic matter, and a comprehensive treatment technology is required.

[0003] Existing wastewater treatment methods usually include physical, chemical and biological treatment. Physical treatment processes remove suspended solids and particulate pollutants through sedimentation, filtration and other methods; chemical treatment uses coagulation, sedimentation and redox reactions to remove some soluble organic pollutants; biological treatment relies on the degradation of microorganisms to remove organic pollutants and reduce color.

[0004] In practical applications, the existing technology has the following main problems:

[0005] Traditional physical filtration methods such as grids and sedimentation tanks can remove large suspended solids, but have limited effects on the removal of fine particles such as ink and large molecular organic matter, which can easily increase the load of subsequent treatment units and affect the overall stability of the system.

[0006] The ink and other organic compounds in carton printing wastewater are relatively stable and difficult to be decomposed by common microorganisms. Therefore, it is difficult for traditional biological treatment processes to effectively remove organic pollutants, resulting in high chemical oxygen demand and biological oxygen demand in the effluent, which is difficult to meet the discharge requirements;

[0007] The ink wastewater has high chromaticity. Traditional biological and chemical treatment processes have poor decolorization effects, and secondary pollution will be generated during the chromaticity removal process. Although deep treatment methods such as chemical oxidation are effective, their operating costs are high and it is difficult to apply them stably in the long term.

[0008] The water quality and quantity of carton printing wastewater fluctuate greatly, and the concentration of pollutants varies greatly. Traditional manual control methods are difficult to adjust the treatment process in a timely and accurate manner, which can easily lead to unstable treatment effects and high operating costs.

[0009] Therefore, those skilled in the art provide a method for treating wastewater in a carton printing production process to solve the above-mentioned problems. Summary of the invention

[0010] In view of the deficiencies in the prior art, the present invention provides a method for treating wastewater in a carton printing production process to solve the problems raised in the above background technology.

[0011] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for treating wastewater in a carton printing production process, comprising:

[0012] Step 1: Filter the carton printing wastewater through coarse and fine grids in sequence to further remove suspended particles;

[0013] Step 2: The filtered wastewater enters the regulating tank, and the pH value of the wastewater is monitored by an online pH sensor. The automatic control system accurately adds NaOH or H2SO4 according to the monitoring results to adjust the pH value to 6-8, and the residence time of the wastewater in the regulating tank is controlled to 6h-8h;

[0014] Step 3: The conditioned wastewater is introduced into a micro-electrolysis device, which is filled with iron-carbon fillers to generate Fe 2+ and gas H2, and the ratio of iron to carbon in the device is 1:1, and the residence time of the wastewater is controlled at 1h-2h;

[0015] Step 4: The wastewater after micro-electrolysis treatment is introduced into a primary coagulation sedimentation tank, and polyaluminium chloride and polyacrylamide are added to the wastewater as coagulants and coagulant aids to perform a coagulation reaction so that the suspended particles and ink particles in the wastewater form flocs;

[0016] Step 5: After the precipitation, the wastewater supernatant is pumped to a subsequent physical and chemical treatment or biological treatment unit for further treatment;

[0017] Step 6: In the physical and chemical unit, suspended solids and ink particles are further removed through flotation, secondary coagulation sedimentation and sand filtration processes; in the biological treatment unit, the wastewater is degraded through anaerobic and aerobic reaction tanks to degrade organic pollutants, and color and residual pollutants are removed in the biological filter.

[0018] Preferably, in step 4, the reaction rate r in the micro-electrolysis treatment satisfies the following formula:

[0019]

[0020] Where r is the reaction rate, k is the reaction rate constant, and C Fe is the concentration of iron, C H+ is the hydrogen ion concentration.

[0021] Preferably, in step 1, the coarse grid spacing is 10 mm-20 mm, and the fine grid spacing is 1 mm-5 mm.

[0022] Preferably, in step 4, the dosage of polyaluminium chloride is controlled at 20mg / L-50mg / L, the dosage of polyacrylamide is controlled at 1mg / L-2mg / L, and the coagulation reaction time is 30min.

[0023] Preferably, in step 6, the flotation treatment step comprises:

[0024] The pressure of the dissolved gas tank is 0.3MPa-0.5MPa, and the bubble diameter is 20 microns-50 microns;

[0025] During the flotation process, 0.5 mg / L of surfactant was added;

[0026] The wastewater forms a scum layer in the flotation tank, which is regularly removed by a scraper.

[0027] The secondary coagulation and sedimentation step further coagulates by adding a secondary coagulant after flotation, the dosage of polyaluminium chloride is 20mg / L-30mg / L, the dosage of polyacrylamide is 1mg / L, and the residence time is 1.5h;

[0028] The sand filter layer has a thickness of 700 mm, a filtration rate of 10 m / h, and is backwashed once to twice a day.

[0029] Preferably, in step 6, the multi-stage biological treatment stage comprises:

[0030] Anaerobic reaction tank: wastewater enters the upflow anaerobic sludge blanket reactor, where anaerobic bacteria degrade macromolecular organic matter into small molecules. The residence time is 10h-12h and the temperature is 35°C.

[0031] Aerobic reaction tank: wastewater is aerobically degraded by aeration in the aerobic tank, dissolved oxygen is controlled at 2mg / L-4mg / L, and the aeration time is 8h;

[0032] Biofilter: Wastewater enters the biofilter, the dissolved oxygen in the filter is maintained above 2 mg / L, and the residence time is 2 hours to remove residual organic matter and color.

[0033] Preferably, the COD removal rate R of the anaerobic reaction tank is COD厌氧 Satisfies the following formula:

[0034]

[0035] Among them, R COD厌氧 is the COD removal rate of the anaerobic reaction tank, COD 进 is the chemical oxygen demand entering the anaerobic reaction tank, COD 出 The chemical oxygen demand of the effluent from the anaerobic reaction tank;

[0036] COD indicates the amount of oxygen consumed by the oxidation of reducing substances in a water sample under the action of a strong oxidant.

[0037] Preferably, the deep oxidation and membrane treatment stage comprises:

[0038] Electrocatalytic oxidation: TiO2 electrode is used to generate hydroxyl radicals to decompose organic matter in wastewater, with a current density of 50A / m 2 -100A / m 2 , reaction time is 1h;

[0039] Activated carbon adsorption: wastewater enters the activated carbon adsorption tower, the adsorption time is 1 hour, and the replacement cycle of activated carbon is 6 months / time;

[0040] Ultrafiltration membrane separation: The pore size of the ultrafiltration membrane should be controlled at 0.01 micron-0.1 micron, and the operating pressure should be controlled at 0.1MPa-0.2MPa to prevent pollutant deposition;

[0041] Reverse osmosis reuse: When wastewater needs to be reused, the reverse osmosis system is used to further remove soluble salts and trace pollutants, with an operating pressure of 1MPa-2MPa.

[0042] Preferably, the deep oxidation and membrane treatment stage comprises:

[0043] Electrocatalytic oxidation: TiO2 electrode is used to generate hydroxyl radicals to decompose organic matter in wastewater, with a current density of 50A / m 2 -100A / m 2 , reaction time is 1h;

[0044] Activated carbon adsorption: wastewater enters the activated carbon adsorption tower, the adsorption time is 1 hour, and the replacement cycle of activated carbon is 6 months / time;

[0045] Ultrafiltration membrane separation: The pore size of the ultrafiltration membrane should be controlled at 0.01 micron-0.1 micron, and the operating pressure should be controlled at 0.1MPa-0.2MPa to prevent pollutant deposition;

[0046] Reverse osmosis reuse: When wastewater needs to be reused, the reverse osmosis system is used to further remove soluble salts and trace pollutants, with an operating pressure of 1MPa-2MPa.

[0047] Preferably, in step 4, polyaluminium chloride and polyacrylamide are added to the wastewater to carry out a coagulation reaction, and the flocs formed by the coagulation reaction are settled in a sedimentation tank, and the residence time in the sedimentation tank is controlled to be 2 hours.

[0048] The present invention provides a method for treating wastewater in a carton printing production process. It has the following beneficial effects:

[0049] 1. The present invention effectively removes suspended particulate matter and macromolecular organic matter in wastewater through multi-stage grid filtration and micro-electrolysis pretreatment, reduces the load of subsequent units, and at the same time, improves the biodegradability of wastewater, provides favorable conditions for subsequent biological treatment, significantly improves overall treatment efficiency, and reduces the risk of system blockage and equipment maintenance.

[0050] 2. The present invention adopts a multi-stage biological treatment system of anaerobic reaction, aerobic reaction and biological filter to decompose organic pollutants and chromaticity in wastewater, significantly reduce chemical oxygen demand and biological oxygen demand, ensure that the effluent water quality meets national emission standards, and the treatment method is stable in effectively removing pollutants, meeting environmental protection requirements.

[0051] 3. The present invention adds electrocatalytic oxidation and membrane separation systems after biological treatment, and effectively removes difficult-to-degrade organic matter, tiny suspended solids and soluble salts through hydroxyl radical oxidation and physical separation of ultrafiltration and reverse osmosis, thereby achieving deep purification of wastewater, making the effluent water quality meet the reuse standard, facilitating the recycling of water resources, and reducing the cost of production water.

[0052] 4. The present invention adopts real-time monitoring and automatic control system to monitor and adjust treatment parameters, reduce the need for manual intervention while optimizing operating efficiency, ensure stable and precise control of the wastewater treatment process, and improve the operating reliability and management efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a flow chart of the present invention;

[0054] Figure 2 It is a flow chart for implementing the solution of the present invention. DETAILED DESCRIPTION

[0055] In order to make the technical personnel in the technical field understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in combination with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a partial embodiment of the present invention, not a complete embodiment. Based on the embodiment of the present invention, other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present invention.

[0056] The present invention is described in detail below in conjunction with the accompanying drawings:

[0057] Example:

[0058] Please see attached Figure 1 and attached Figure 2 The embodiment of the present invention provides a method for treating wastewater in a carton printing production process, comprising:

[0059] Step 1: Filter the carton printing wastewater through coarse and fine grids in sequence to further remove suspended particles;

[0060] Step 2: The filtered wastewater enters the regulating tank, and the pH value of the wastewater is monitored by an online pH sensor. The automatic control system accurately adds NaOH or H2SO4 according to the monitoring results to adjust the pH value to 6-8, and the residence time of the wastewater in the regulating tank is controlled to 6h-8h;

[0061] Step 3: The conditioned wastewater is introduced into a micro-electrolysis device, which is filled with iron-carbon fillers to generate Fe 2+ and gas H2, and the ratio of iron to carbon in the device is 1:1, and the residence time of the wastewater is controlled at 1h-2h;

[0062] Step 4: The wastewater after micro-electrolysis treatment is introduced into a primary coagulation sedimentation tank, and polyaluminium chloride and polyacrylamide are added to the wastewater as coagulants and coagulant aids to perform a coagulation reaction so that the suspended particles and ink particles in the wastewater form flocs;

[0063] Step 5: After the precipitation, the wastewater supernatant is pumped to a subsequent physical and chemical treatment or biological treatment unit for further treatment;

[0064] Step 6: In the physical and chemical unit, suspended solids and ink particles are further removed through flotation, secondary coagulation sedimentation and sand filtration processes; in the biological treatment unit, the wastewater is degraded through anaerobic and aerobic reaction tanks to degrade organic pollutants, and color and residual pollutants are removed in the biological filter.

[0065] Benefits of Step 1 Coarse and fine grid filtration can effectively remove suspended particles in wastewater, reduce the burden on subsequent treatment units, avoid equipment clogging, improve system operation efficiency and stability, and extend the service life of subsequent treatment equipment;

[0066] Benefits of Step 2 The regulating tank realizes the homogenization of wastewater, ensures that the pH value is stable at 6-8, provides the best acid-base conditions for subsequent micro-electrolysis treatment, helps to improve the efficiency of micro-electrolysis reaction, reduces the use of excessive reagents, and further reduces treatment costs;

[0067] Benefits of step 3 Micro-electrolysis treatment by generating reduced Fe 2+ , destroy the structure of macromolecular organic matter in wastewater, improve the biodegradability of wastewater, create favorable conditions for subsequent biological treatment, remove some heavy metal pollutants, and significantly improve the overall pollutant removal rate;

[0068] Benefits of Step 4: Coagulation and sedimentation can effectively remove suspended particles and ink particles, form flocs through the synergistic effect of polyaluminium chloride and polyacrylamide, and make some pollutants settle to the bottom of the pool, reducing the turbidity of the wastewater, providing a relatively clear supernatant for subsequent treatment units, and improving the overall water quality;

[0069] Benefits of step 5: The supernatant is transported to the subsequent treatment unit through the pumping system, which avoids staying in the sedimentation tank for too long, prevents the pollutants in the supernatant from being re-suspended, ensures the stable water inflow of the subsequent treatment unit, and ensures the efficient progress of the subsequent treatment;

[0070] Benefits of Step 6: The flotation, secondary coagulation sedimentation and sand filtration of the physical and chemical unit can further remove fine suspended matter and ink particles, further reducing the suspended matter concentration in the effluent; the biological treatment unit decomposes organic pollutants in the wastewater through a combination of anaerobic and aerobic methods, removes color and difficult-to-degrade residual pollutants in the biological filter, effectively reduces chemical oxygen demand and biological oxygen demand, and ensures that the effluent water quality is stable and meets the standards.

[0071] In step 4, the reaction rate r in the micro-electrolysis process satisfies the following formula:

[0072]

[0073] Where r is the reaction rate, k is the reaction rate constant, and C Fe is the iron concentration, is the hydrogen ion concentration;

[0074] In step 4, the dosage of polyaluminium chloride is controlled at 20mg / L-50mg / L, the dosage of polyacrylamide is controlled at 1mg / L-2mg / L, and the coagulation reaction time is 30min;

[0075] In step 4, polyaluminium chloride and polyacrylamide are added to the wastewater to carry out coagulation reaction. The flocs formed by the coagulation reaction are settled in the sedimentation tank, and the residence time in the sedimentation tank is controlled at 2 hours.

[0076] By controlling the rate of micro-electrolysis reaction, the degradation rate of pollutants can be accurately adjusted to improve the removal efficiency. The precise control of iron concentration and hydrogen ion concentration makes the reduction reaction more efficient, effectively destroying the macromolecular organic matter in the wastewater, improving the biodegradability of the wastewater, and providing more suitable water inlet conditions for subsequent biological treatment units. Accurate reaction control helps to reduce the waste of reagents and reduce operating costs, while ensuring the stability of micro-electrolysis treatment.

[0077] By properly controlling the dosage of polyaluminium chloride and polyacrylamide, the floc formation effect can be ensured, the coagulation reaction can be made more efficient, the suspended particles and ink particles in the wastewater can be effectively removed, the waste of chemical agents due to excessive dosage can be avoided, and the treatment cost can be reduced. In addition, the appropriate dosage can avoid the secondary pollution problem caused by the residual agent, making the effluent quality more stable.

[0078] The floc sedimentation formed by coagulation reaction can significantly reduce the suspended solids and turbidity in the wastewater, ensuring clearer effluent. The 2-hour residence time in the sedimentation tank provides sufficient time for the floc sedimentation, which helps to form a stable sedimentation effect and avoid the redispersion of the flocs during the sedimentation process. At the same time, the stable sedimentation time reduces the residual suspended matter in the supernatant, provides good water inlet conditions for subsequent treatment units, and improves the efficiency and stability of the overall treatment system.

[0079] In step 1, the coarse grid spacing is 10mm-20mm, and the fine grid spacing is 1mm-5mm.

[0080] In step 6, the flotation treatment step includes:

[0081] The pressure of the dissolved gas tank is 0.3MPa-0.5MPa, and the bubble diameter is 20 microns-50 microns;

[0082] During the flotation process, 0.5 mg / L of surfactant was added;

[0083] The wastewater forms a scum layer in the flotation tank, which is regularly removed by a scraper.

[0084] The secondary coagulation and sedimentation step is to further coagulate by adding a secondary coagulant after flotation, the dosage of polyaluminium chloride is 20mg / L-30mg / L, the dosage of polyacrylamide is 1mg / L, and the residence time is 1.5h;

[0085] The thickness of the sand filter layer is 700mm, the filtration rate is 10m / h, and the backwash is 1-2 times per day;

[0086] In step 6, the multi-stage biological treatment phase includes:

[0087] Anaerobic reaction tank: wastewater enters the upflow anaerobic sludge blanket reactor, where anaerobic bacteria degrade macromolecular organic matter into small molecules. The residence time is 10h-12h and the temperature is 35°C.

[0088] Aerobic reaction tank: wastewater is aerobically degraded in the aerobic tank through aeration, dissolved oxygen is controlled at 2mg / L-4mg / L, and the aeration time is 8h;

[0089] Biofilter: Wastewater enters the biofilter, the dissolved oxygen in the filter is maintained above 2 mg / L, and the residence time is 2 hours to remove residual organic matter and color.

[0090] The graded filtration of coarse and fine grids effectively removes large particles of impurities in the wastewater, protects the subsequent treatment units, prevents them from clogging and wear, and prolongs the service life of the equipment and reduces the need for equipment maintenance. In addition, graded filtration reduces the load of the subsequent treatment units and improves the operating efficiency and treatment stability of the overall system;

[0091] Flotation treatment generates tiny bubbles, causing ink particles and suspended solids to float to the surface quickly and form a scum layer, significantly reducing the concentration and turbidity of suspended solids in wastewater. At the same time, the addition of surfactants enhances the flotation effect, further improves the removal rate, and reduces the risk of suspended solids entering subsequent treatment units. Scum is regularly removed by a scraper to keep the flotation system running efficiently, providing more stable water inlet conditions for subsequent treatment.

[0092] Secondary coagulation and sedimentation further removes residual ink particles and tiny suspended solids in the wastewater. Reasonable control of the dosage of polyaluminium chloride and polyacrylamide ensures that the flocs formed are large and the sedimentation speed is fast, effectively reducing the turbidity and residual suspended solids content in the water body. Appropriate residence time ensures the completeness of floc sedimentation, improves the transparency of the supernatant, provides cleaner water quality for subsequent treatment, and optimizes the overall treatment effect of the system;

[0093] Sand filtration can effectively intercept tiny suspended particles remaining in wastewater, further purify water quality, and improve the clarity of effluent. Appropriate sand filter layer thickness and filtration rate ensure efficient removal of particles, and maintain the filtration effect and treatment capacity of the sand filter layer through backwashing 1-2 times a day to avoid blockage, ensure continuous and efficient operation of the system, and provide high-quality influent for subsequent biological treatment units.

[0094] The anaerobic bacteria in the anaerobic reaction tank can effectively degrade macromolecular organic matter and decompose it into small molecular organic acids and methane, significantly reducing the chemical oxygen demand level and organic matter content of the wastewater, reducing the load of subsequent aerobic treatment, controlling the appropriate residence time and temperature to ensure the stability and efficiency of the anaerobic reaction, improving the removal efficiency of organic matter, making the wastewater more biodegradable, and facilitating subsequent aerobic degradation;

[0095] The aerobic reaction tank provides an ideal degradation environment for aerobic microorganisms through aeration, further removes residual organic pollutants in the wastewater, controls the dissolved oxygen concentration at 2mg / L-4mg / L, effectively promotes the activity of aerobic microorganisms, ensures the thorough decomposition of organic matter, and significantly reduces the chemical oxygen demand and biological oxygen demand of the wastewater. The control of aeration time ensures that the wastewater is fully treated in the aerobic tank, and the effluent water quality is stable, creating good conditions for further treatment in the biological filter;

[0096] The biological filter uses microorganisms attached to the surface of the filter material to further degrade the residual organic matter and color in the wastewater, ensuring that the effluent water quality meets the discharge standards. The dissolved oxygen is controlled at above 2 mg / L to provide sufficient oxygen for the microorganisms, which is conducive to degrading organic matter and removing color, making the effluent clearer. The appropriate residence time ensures sufficient treatment of the microorganisms, reduces the color and organic pollutant content in the effluent, and ensures that the wastewater meets the discharge standards or meets the reuse requirements.

[0097] COD removal rate R of anaerobic reaction tank COD厌氧 Satisfies the following formula:

[0098]

[0099] Among them, R COD厌氧 is the COD removal rate of the anaerobic reaction tank, COD 进 is the chemical oxygen demand entering the anaerobic reaction tank, COD 出 The chemical oxygen demand of the effluent from the anaerobic reaction tank;

[0100] COD indicates the amount of oxygen consumed by the oxidation of reducing substances in a water sample under the action of a strong oxidant.

[0101] The anaerobic reaction tank decomposes the macromolecular organic matter in the wastewater into small molecular compounds and releases gas through the metabolism of anaerobic bacteria, significantly reducing the chemical oxygen demand content of the wastewater. The reduction of chemical oxygen demand can effectively improve the pollution load of the wastewater, create more suitable water inlet conditions for subsequent aerobic treatment, and improve the efficiency of the overall treatment system;

[0102] The anaerobic reactor can significantly remove the chemical oxygen demand in the early stage of wastewater treatment, effectively reducing the organic matter load entering the aerobic reactor, thereby reducing the treatment burden of the aerobic reactor, improving the efficiency of aerobic treatment, shortening the treatment time, and making the treatment process more stable and economical;

[0103] The methane gas produced by anaerobic reaction can be collected and used to provide energy for the wastewater treatment process, realize partial energy recycling, and reduce the energy consumption of the system. At the same time, anaerobic treatment does not require oxygenation and is more energy-efficient than aerobic treatment, which helps to reduce the operating cost of the treatment system.

[0104] After anaerobic treatment, the macromolecular organic matter in the wastewater is partially degraded into small molecular organic acids, which improves the biodegradability of the wastewater, enhances the biodegradation effect of subsequent aerobic and biological filters, improves the organic matter removal rate of the system, and makes the effluent water quality more in line with the discharge or reuse standards.

[0105] The deep oxidation and membrane treatment stages include:

[0106] Electrocatalytic oxidation: TiO2 electrode is used to generate hydroxyl radicals to decompose organic matter in wastewater, with a current density of 50A / m 2 -100A / m 2 , reaction time is 1h;

[0107] Activated carbon adsorption: wastewater enters the activated carbon adsorption tower, the adsorption time is 1 hour, and the replacement cycle of activated carbon is 6 months / time;

[0108] Ultrafiltration membrane separation: The pore size of the ultrafiltration membrane should be controlled at 0.01 micron-0.1 micron, and the operating pressure should be controlled at 0.1MPa-0.2MPa to prevent pollutant deposition;

[0109] Reverse osmosis reuse: When wastewater needs to be reused, the reverse osmosis system is used to further remove soluble salts and trace pollutants, with an operating pressure of 1MPa-2MPa.

[0110] Electrocatalytic oxidation can effectively decompose the refractory organic matter and trace residual pollutants in wastewater, improve the cleanliness of water quality, and the strong oxidizing property of hydroxyl radicals enables it to quickly oxidize and decompose various organic molecules, achieving deep purification of wastewater. In addition, the process does not require chemical agents, reduces secondary pollution caused by chemical treatment, and improves the environmental protection and treatment effect of the treatment system;

[0111] Activated carbon has a highly developed pore structure and a large specific surface area, which can effectively adsorb residual trace organic matter, odor and color substances in wastewater, further improving the clarity and quality of effluent. The adsorption step provides cleaner influent for subsequent membrane separation units, reduces the risk of membrane fouling, and extends the service life of the membrane. At the same time, the long-term effectiveness of activated carbon makes the adsorption operation cost lower, which helps to reduce operating costs;

[0112] Ultrafiltration membranes can effectively filter tiny suspended particles and microorganisms in water, remove residual tiny particle pollutants, and ensure the purity of water. By controlling the appropriate pore size and pressure conditions, ultrafiltration membranes can prevent pollutants from depositing on the membrane surface, reduce membrane pollution, and increase the service life of the membrane. At the same time, ultrafiltration separation provides clean water for the subsequent reverse osmosis treatment of wastewater, improving the overall treatment effect of the system;

[0113] The reverse osmosis membrane has an extremely fine pore size, which can remove soluble salts, heavy metal ions and trace organic pollutants in wastewater, so that the water quality meets high standards for reuse. After reverse osmosis treatment, the wastewater can be used for production reuse or equipment cleaning, reducing the consumption of fresh water, effectively realizing the recycling of water resources, reducing production costs and water waste, and meeting the goals of environmental protection and sustainable development.

[0114] In step 2, the automatic control system uses a proportional integral differential control algorithm to adjust the amount of added NaOH or H2SO4 according to the pH value of the wastewater, wherein the proportional integral differential control algorithm formula is:

[0115]

[0116] Among them, u(t) is the output of the controller, e(t) is the current error, K p is the proportional gain, K i is the integral gain, K d is the differential gain, t is the time variable, τ is the integral variable, dt is the time increment, de(t) is the change of the error e(t), and e(t) is the error.

[0117] The proportional-integral-differential control algorithm can adjust the dosage of NaOH or H2SO4 according to the real-time error, so that the pH value of the wastewater can quickly reach and stabilize within the target range. The proportional control quickly responds to the current error, the integral control eliminates the cumulative error, and the differential control predicts the change trend of the error, ensuring the precise control of the pH value, providing the best reaction environment for the subsequent micro-electrolysis reaction, and significantly improving the overall treatment efficiency.

[0118] The proportional-integral-differential control algorithm can accurately adjust the dosage of NaOH or H2SO4 to avoid over-dosage. The control algorithm monitors and dynamically adjusts in real time, which can effectively reduce the waste of chemical agents and reduce operating costs. In addition, the precise addition of agents reduces secondary pollution caused by residual agents and ensures the stability of effluent quality.

[0119] Automatically adjust the pH value during wastewater treatment to reduce the frequency of manual operations, and be able to respond quickly when the influent water quality fluctuates to maintain system stability. The automated characteristics of the proportional-integral-differential control algorithm reduce the need for manual intervention, improve the system's operational reliability, and ensure the continuity of the treatment effect.

[0120] By stabilizing the pH value and ensuring that treatment units such as micro-electrolysis and coagulation reactions always operate under optimal conditions, the pollutant removal rate is higher and the effluent water quality is clearer. Precise pH control and chemical dosage adjustment further reduce the potential impact on the environment during wastewater treatment, achieving a more environmentally friendly wastewater treatment solution.

[0121] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for treating wastewater in a carton printing production process, characterized in that: include: Step 1: Filter the carton printing wastewater through coarse and fine grids in sequence to further remove suspended particles; Step 2: The filtered wastewater enters the regulating tank, and the pH value of the wastewater is monitored by an online pH sensor. The automatic control system accurately adds NaOH or H2SO4 according to the monitoring results to adjust the pH value to 6-8, and the residence time of the wastewater in the regulating tank is controlled to 6h-8h; Step 3: The conditioned wastewater is introduced into a micro-electrolysis device, which is filled with iron-carbon fillers to generate Fe 2+ and gas H2, and the ratio of iron to carbon in the device is 1:1, and the residence time of the wastewater is controlled at 1h-2h; Step 4: The wastewater after micro-electrolysis treatment is introduced into a primary coagulation sedimentation tank, and polyaluminium chloride and polyacrylamide are added to the wastewater as coagulants and coagulant aids to perform a coagulation reaction so that the suspended particles and ink particles in the wastewater form flocs; Step 5: After the precipitation, the wastewater supernatant is pumped to a subsequent physical and chemical treatment or biological treatment unit for further treatment; Step 6: In the physical and chemical unit, suspended solids and ink particles are further removed through flotation, secondary coagulation sedimentation and sand filtration processes; in the biological treatment unit, the wastewater is degraded through anaerobic and aerobic reaction tanks to degrade organic pollutants, and color and residual pollutants are removed in the biological filter.

2. The method for treating wastewater in a carton printing production process according to claim 1, characterized in that: In step 4, the reaction rate r in the micro-electrolysis process satisfies the following formula: Where r is the reaction rate, k is the reaction rate constant, and C Fe is the iron concentration, is the hydrogen ion concentration.

3. The method for treating wastewater in a carton printing production process according to claim 1, characterized in that: In step 1, the coarse grid spacing is 10 mm-20 mm, and the fine grid spacing is 1 mm-5 mm.

4. The method for treating wastewater in a carton printing production process according to claim 1, characterized in that: In step 4, the dosage of polyaluminium chloride is controlled at 20mg / L-50mg / L, the dosage of polyacrylamide is controlled at 1mg / L-2mg / L, and the coagulation reaction time is 30min.

5. The method for treating wastewater in a carton printing production process according to claim 1, characterized in that: In step 6, the flotation treatment step includes: The pressure of the dissolved gas tank is 0.3MPa-0.5MPa, and the bubble diameter is 20 microns-50 microns; During the flotation process, 0.5 mg / L of surfactant was added; The wastewater forms a scum layer in the flotation tank, which is regularly removed by a scraper. The secondary coagulation and sedimentation step further coagulates by adding a secondary coagulant after flotation, the dosage of polyaluminium chloride is 20mg / L-30mg / L, the dosage of polyacrylamide is 1mg / L, and the residence time is 1.5h; The sand filter layer has a thickness of 700 mm, a filtration rate of 10 m / h, and is backwashed once to twice a day.

6. The method for treating wastewater in a carton printing production process according to claim 1, characterized in that: In step 6, the multi-stage biological treatment stage includes: Anaerobic reaction tank: wastewater enters the upflow anaerobic sludge blanket reactor, where anaerobic bacteria degrade macromolecular organic matter into small molecules. The residence time is 10h-12h and the temperature is 35°C. Aerobic reaction tank: wastewater is aerobically degraded in the aerobic tank through aeration, dissolved oxygen is controlled at 2mg / L-4mg / L, and the aeration time is 8h; Biofilter: Wastewater enters the biofilter, the dissolved oxygen in the filter is maintained above 2 mg / L, and the residence time is 2 hours to remove residual organic matter and color.

7. The method for treating wastewater in a carton printing production process according to claim 6, characterized in that: The COD removal rate R of the anaerobic reaction tank COD厌氧 Satisfies the following formula: Among them, R COD厌氧 is the COD removal rate of the anaerobic reaction tank, COD 进 is the chemical oxygen demand entering the anaerobic reaction tank, COD 出 It is the chemical oxygen demand of the effluent from the anaerobic reaction tank; COD indicates the amount of oxygen consumed by the oxidation of reducing substances in a water sample under the action of a strong oxidant.

8. The method for treating wastewater in a carton printing production process according to claim 1, characterized in that: The deep oxidation and membrane treatment stage includes: Electrocatalytic oxidation: TiO2 electrode is used to generate hydroxyl radicals to decompose organic matter in wastewater, with a current density of 50A / m 2 -100A / m 2 , reaction time is 1h; Activated carbon adsorption: wastewater enters the activated carbon adsorption tower, the adsorption time is 1 hour, and the replacement cycle of activated carbon is 6 months / time; Ultrafiltration membrane separation: The pore size of the ultrafiltration membrane should be controlled at 0.01 micron-0.1 micron, and the operating pressure should be controlled at 0.1MPa-0.2MPa to prevent pollutant deposition; Reverse osmosis reuse: When wastewater needs to be reused, the reverse osmosis system is used to further remove soluble salts and trace pollutants, with an operating pressure of 1MPa-2MPa.

9. The method for treating wastewater in a carton printing production process according to claim 1, characterized in that: In step 2, the automatic control system uses a proportional-integral-differential control algorithm to adjust the amount of added NaOH or H2SO4 according to the pH value of the wastewater, wherein the proportional-integral-differential control algorithm formula is: Among them, u(t) is the output of the controller, e(t) is the current error, K p is the proportional gain, K i is the integral gain, K d is the differential gain, t is the time variable, τ is the integral variable, dt is the time increment, de(t) is the change of the error e(t), and e(t) is the error.

10. The method for treating wastewater in a carton printing production process according to claim 1, characterized in that: In the step 4, polyaluminium chloride and polyacrylamide are added to the wastewater to carry out a coagulation reaction, and the flocs formed by the coagulation reaction are settled in a sedimentation tank, and the residence time in the sedimentation tank is controlled to be 2 hours.

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