Sewage filtering treatment method

Abstract

The invention discloses a sewage filtration treatment method, which belongs to the field of sewage treatment, and comprises a pretreatment stage, a composite membrane filtration stage, an advanced oxidation-adsorption coupling filtration stage, a deep purification stage and a resource recovery stage, and is characterized in that suspended particulate matters and part of organic matters are removed by adjusting the pH value of sewage and adding a modified diatomite adsorbent; carrying out pressure filtration through a three-stage composite membrane assembly to obtain a primary filtrate; then, a ferrous ion-sodium persulfate-ozone-ultraviolet synergistic oxidation process is adopted, coupling filtration is achieved in combination with a double-layer modified activated carbon filter layer, and then deep purification is completed through ion exchange and ultraviolet disinfection. According to the sewage filtering treatment method, adsorption, filtering and advanced oxidation technologies are efficiently coupled, the treatment effect and the resource utilization rate are considered, operation is easy and convenient, running is stable, the content of COD, suspended particulate matter and ionic pollutants in sewage can be effectively reduced, and the sewage filtering treatment method is suitable for various industrial and domestic sewage treatment scenes.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a wastewater filtration treatment method. Background Technology

[0002] With rapid industrial development and accelerated urbanization, wastewater discharge has been increasing year by year. The wastewater contains suspended particulate matter, organic pollutants, heavy metal ions, and other harmful substances, posing a serious threat to aquatic ecosystems and human health. The efficiency, environmental friendliness, and resource utilization of wastewater treatment technologies have become a research hotspot in the industry. Existing wastewater filtration treatment methods mainly include single or combined processes such as physical adsorption, membrane filtration, oxidative degradation, and ion exchange.

[0003] Physical adsorption methods often use adsorbents such as diatomaceous earth and activated carbon, but their adsorption capacity is limited, and unmodified adsorbents have poor selectivity for pollutants, easily leading to saturation failure and poor treatment results. Membrane filtration technology is widely used due to its high retention accuracy, but single membrane modules are susceptible to fouling, experience rapid flux decay, and are difficult to remove pollutants of different particle sizes and dissolved organic matter simultaneously, requiring the use of pretreatment processes. Advanced oxidation technologies can effectively degrade recalcitrant organic pollutants, but traditional oxidation processes (such as ozone oxidation and ultraviolet oxidation alone) suffer from low oxidation efficiency and high energy consumption, making it difficult to achieve complete removal of pollutants.

[0004] Therefore, there is an urgent need for a wastewater filtration treatment method that has strong process synergy, good treatment effect, and high resource utilization rate. Summary of the Invention

[0005] The purpose of this invention is to address the problems of existing wastewater treatment methods, such as the obvious limitations of single processes, weak synergy of combined processes, low resource utilization, and easy occurrence of secondary pollution, and to propose a wastewater filtration treatment method.

[0006] To achieve the above objectives, the present invention employs the following technology: a wastewater filtration treatment method, comprising the following steps: S1. Pretreatment stage: The wastewater to be treated is introduced into the equalization tank, and the pH value of the wastewater is adjusted to 6.5-7.5 by pH adjuster. At the same time, modified diatomaceous earth adsorbent is added. The modified diatomaceous earth adsorbent is obtained by soaking and modifying in 5-8% aluminum chloride solution, drying and pulverizing, with a particle size of 80-120 mesh. The addition amount is 0.3-0.5% of the wastewater mass. The stirring rate is 200-300 r / min, the stirring time is 20-30 min, and the mixture is allowed to stand for 1-2 h to remove suspended particulate matter and some organic pollutants, thus obtaining pretreated wastewater. S2, Composite Membrane Filtration Stage: The pretreated wastewater is pumped to the composite membrane module via a pressurized pump. The composite membrane module is composed of a surface polyvinylidene fluoride ultrafiltration membrane, a middle polyamide nanofiltration membrane, and a bottom ceramic support membrane. The surface ultrafiltration membrane has a pore size of 50-100 nm, the middle nanofiltration membrane has a pore size of 1-5 nm, the pressurization pressure is controlled at 0.3-0.5 MPa, and the filtration temperature is 25-35℃ to obtain the primary filtrate. S3, Advanced Oxidation-Adsorption Coupled Filtration Stage: The primary filtrate is introduced into the integrated reaction filtration tank. The COD content is first detected using an online water quality monitor. Then, ferrous ion catalyst and sodium persulfate oxidant are added at 1.2-1.5 times the COD content. After addition, the mixture is stirred for 10 minutes. Ozone is then introduced at a rate of 0.9-1.1 mg / L, with a residence time of 15 minutes. Simultaneously, intermittent ultraviolet irradiation is activated. The ultraviolet wavelength is 254 nm, and the power is 120-140 W. The irradiation mode is 5 minutes of irradiation followed by a 2-minute pause, repeated until the reaction is complete. The total reaction time is 32-38 minutes. During the reaction, the filtrate is simultaneously filtered through a double-layer modified activated carbon filter layer. The upper layer is granular modified activated carbon, and the lower layer is powdered modified activated carbon, with a total thickness of 10-11 cm and a filtration rate of 1.2-1.8 m / h. The waste carbon layer produced during filtration is collected and used as a conditioner in the anaerobic digester to obtain the intermediate filtrate. S4. Deep purification stage: The intermediate filtrate is introduced into the ion exchange column and treated by ion exchange through a mixed bed of cation exchange resin and anion exchange resin. The volume ratio of cation exchange resin to anion exchange resin is 1:1.2-1:1.5, and the treatment flow rate is 0.5-1m / h. Then, it is disinfected by an ultraviolet sterilizer for 15-20 minutes to obtain treated water that meets the standards. S5. Resource recovery stage: Collect sludge and waste adsorbent generated in each treatment stage and carry out in-situ resource recovery treatment.

[0007] As a further description of the above technical solution: In step S1, when the wastewater to be treated is introduced into the equalization tank, large debris with a particle size ≥5mm is first removed by a screen. The pH adjuster is a compound adjuster, which is composed of 12-14% hydrochloric acid solution, 9-11% sodium hydroxide solution and 0.5% potassium dihydrogen phosphate solution in a volume ratio of 5:5:1. It can maintain the pH value of wastewater within the target range of ±0.1.

[0008] As a further description of the above technical solution: In step S1, the sludge produced by static sedimentation is introduced into the anaerobic digester. The biogas produced by the anaerobic digester is desulfurized by a desulfurization tower to remove hydrogen sulfide, and then stored in a gas storage tank. It is then used by a biogas burner to provide a heat source for the temperature control tank and the membrane module heat treatment process. The waste heat is recovered by a heat exchanger for heating in the ion exchange resin regeneration stage, thereby realizing energy recycling.

[0009] As a further description of the above technical solution: In step S2, the surface modified polyvinylidene fluoride ultrafiltration membrane is modified by dopamine grafting and has a porosity of 75-80%; the middle cross-linked polyamide nanofiltration membrane is prepared by cross-linking piperazine and trimesoyl chloride; the bottom ceramic support membrane is an alumina-zirconia composite ceramic with a pore size of 200-300 nm and a thickness of 3-5 mm.

[0010] As a further description of the above technical solution: In step S2, when the membrane flux drops to 70% of the initial flux, online flushing is started. The online flushing first uses a sodium hydroxide solution with a mass fraction of 0.6-0.8% at room temperature for 35 minutes and a flushing flow rate of 0.8 m / s. Then, it uses a hydrochloric acid solution with a mass fraction of 0.4% at room temperature for 35 minutes. Finally, it is rinsed with deionized water until the pH value of the effluent is neutral. After flushing, the membrane flux recovers to more than 90% of the initial flux.

[0011] As a further description of the above technical solution: In step S3, the ultraviolet irradiation device uses multiple sets of ring lamps evenly arranged on the inner wall of the reaction filtration tank. The distance between the lamps and the tank wall is 15-20cm, and the distance between adjacent lamps is 30cm, to ensure that the primary filtrate is uniformly illuminated and the ultraviolet light intensity is maintained at 10-12mW / cm² in the reaction area.

[0012] As a further description of the above technical solution: In step S4, the regeneration process of the ion exchange resin is as follows: the cation exchange resin is regenerated by soaking in a 5% hydrochloric acid solution at a regeneration temperature of 40°C for 1 hour; the anion exchange resin is regenerated by soaking in a 4% sodium hydroxide solution at a regeneration temperature of 40°C for 1 hour; the mixed ion exchange bed first regenerates the anion resin with an alkaline solution, and then regenerates the cation resin with an acid solution. After regeneration, the effluent is rinsed with deionized water until the pH value of the effluent is 6.5-7.5 before it can be put into use again.

[0013] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This method deeply couples modified diatomaceous earth adsorption, three-stage composite membrane filtration, multi-element synergistic advanced oxidation and ion exchange technologies, which can efficiently remove suspended particulate matter, some organic matter, recalcitrant COD and ionic pollutants from wastewater layer by layer. The synergistic effect is significantly better than single processes or simple combination processes, ensuring that the effluent water quality meets the standards stably.

[0014] 2. The various treatment stages are closely linked. Pretreatment provides high-quality feed water for composite membrane filtration, reducing membrane fouling and delaying flux decline. Advanced oxidation-adsorption coupled filtration simultaneously achieves pollutant degradation and retention, significantly shortening the treatment cycle. The design of intermittent ultraviolet irradiation and precise reagent dosing balances treatment efficiency and energy consumption control, resulting in high operational stability.

[0015] 3. Through in-situ resource recovery design, the waste carbon of the double-layer modified activated carbon filter layer can be used as a conditioner for anaerobic digestion tanks. Sludge and waste adsorbents at each stage are uniformly recycled and treated, avoiding waste of by-products and secondary pollution. Modified diatomaceous earth adsorbents are low in cost and easy to prepare. The composite membrane module and reagent dosage are optimized to further reduce operating and consumable costs. Attached Figure Description

[0016] Figure 1 A principle block diagram provided according to an embodiment of the present invention is shown. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Reference Figure 1 This embodiment provides a wastewater filtration treatment method, which includes the following steps: S1. Pretreatment stage: The wastewater to be treated is introduced into the equalization tank, and the pH value of the wastewater is adjusted to 6.5-7.5 by pH adjuster. At the same time, modified diatomaceous earth adsorbent is added at a rate of 0.3-0.5% of the wastewater mass. The stirring rate is 200-300 r / min, the stirring time is 20-30 min, and the mixture is allowed to stand for sedimentation for 1-2 h to remove suspended particulate matter and some organic pollutants, thus obtaining pretreated wastewater. The preparation process of modified diatomaceous earth adsorbent is as follows: take natural diatomaceous earth, dry it at 105℃ for 2 hours, crush it through a 100-mesh sieve, place it in an aluminum chloride solution with a mass fraction of 6-7%, soak it at a constant temperature of 60℃ for 4 hours, and stir it once every 30 minutes during the soaking period at a stirring rate of 150 r / min. After soaking, filter it, dry the filter residue at 110℃ to constant weight, crush it again through a 120-mesh sieve, and control the particle size to 90-110 mesh.

[0019] When the wastewater to be treated is introduced into the equalization tank, large debris with a particle size ≥5mm is first removed by a screen. The pH adjuster is a compound adjuster, which is composed of 12-14% hydrochloric acid solution, 9-11% sodium hydroxide solution and 0.5% potassium dihydrogen phosphate solution in a volume ratio of 5:5:1. It can maintain the pH value of the wastewater within the target range of ±0.1.

[0020] It should be noted that the sludge produced by static sedimentation is introduced into the anaerobic digester. The biogas produced in the anaerobic digester is desulfurized by a desulfurization tower to remove hydrogen sulfide, then stored in a gas storage tank. The biogas burner then provides a heat source for the temperature control tank and the membrane module heat treatment process. The waste heat is recovered by a heat exchanger for heating in the ion exchange resin regeneration stage, thus realizing energy recycling.

[0021] S2, Composite Membrane Filtration Stage: The pretreated wastewater is pumped to the composite membrane module via a pressurized pump. The composite membrane module is composed of a surface polyvinylidene fluoride ultrafiltration membrane, a middle polyamide nanofiltration membrane, and a bottom ceramic support membrane. The surface ultrafiltration membrane has a pore size of 50-100 nm, the middle nanofiltration membrane has a pore size of 1-5 nm, the pressurization pressure is controlled at 0.3-0.5 MPa, and the filtration temperature is 25-35℃ to obtain the primary filtrate. The surface layer is a modified polyvinylidene fluoride ultrafiltration membrane with dopamine grafting modification and a porosity of 75-80%; the middle layer is a cross-linked polyamide nanofiltration membrane prepared by cross-linking piperazine and trimesoyl chloride; the bottom layer is alumina-zirconia composite ceramic with a pore size of 200-300 nm and a thickness of 3-5 mm.

[0022] When the membrane flux drops to 70% of the initial flux, online flushing is initiated. The online flushing first uses a 0.6-0.8% sodium hydroxide solution at room temperature for 35 minutes at a flow rate of 0.8 m / s, then uses a 0.4% hydrochloric acid solution at room temperature for 35 minutes, and finally rinses with deionized water until the pH of the effluent is neutral. After flushing, the membrane flux recovers to more than 90% of the initial flux.

[0023] It should be noted that the preparation method of the composite membrane module is as follows: 1. Immerse the alumina-zirconia composite ceramic support membrane in a 5% hydrofluoric acid solution for 30 min, wash until neutral, and dry at 120℃; 2. Immerse the pretreated ceramic support membrane in a polyamide casting solution (piperazine concentration 2wt%, trimesoyl chloride concentration 0.5wt%, solvent N,N-dimethylformamide), pull at a rate of 2 mm / s, air dry at room temperature, and then heat treat at 80℃ for 1 h; 3. Immerse the support membrane coated with nanofiltration membrane in a modified polyvinylidene fluoride casting solution (polyvinylidene fluoride concentration 15wt%, dopamine concentration 0.8wt%, solvent N-methylpyrrolidone), pull at a rate of 1.5 mm / s, place in a coagulation bath (water-ethanol volume ratio 7:3) to solidify, and finally heat treat at 130-140℃ for 2.5 h, cool to room temperature for later use.

[0024] S3, Advanced Oxidation-Adsorption Coupled Filtration Stage: The primary filtrate is introduced into the integrated reaction filtration tank. The COD content is first detected using an online water quality monitor. Then, ferrous ion catalyst and sodium persulfate oxidant are added at 1.2-1.5 times the COD content. After addition, the mixture is stirred for 10 minutes. Ozone is then introduced at a rate of 0.9-1.1 mg / L, with a residence time of 15 minutes. Simultaneously, intermittent ultraviolet irradiation is activated. The ultraviolet wavelength is 254 nm, and the power is 120-140 W. The irradiation mode is 5 minutes of irradiation followed by a 2-minute pause, repeated until the reaction is complete. The total reaction time is 32-38 minutes. During the reaction, the filtrate is simultaneously filtered through a double-layer modified activated carbon filter layer. The upper layer is granular modified activated carbon, and the lower layer is powdered modified activated carbon, with a total thickness of 10-11 cm and a filtration rate of 1.2-1.8 m / h. The waste carbon layer produced during filtration is collected and used as a conditioner in the anaerobic digester to obtain the intermediate filtrate. The ultraviolet irradiation device uses multiple sets of ring lamps evenly arranged on the inner wall of the reaction filtration tank. The distance between the lamps and the tank wall is 15-20cm, and the distance between adjacent lamps is 30cm, to ensure that the primary filtrate is uniformly illuminated and the ultraviolet light intensity is maintained at 10-12mW / cm² in the reaction area.

[0025] S4. Deep purification stage: The intermediate filtrate is introduced into the ion exchange column and treated by ion exchange through a mixed bed of cation exchange resin and anion exchange resin. The volume ratio of cation exchange resin to anion exchange resin is 1:1.2-1:1.5, and the treatment flow rate is 0.5-1m / h. Then, it is disinfected by an ultraviolet sterilizer for 15-20 minutes to obtain treated water that meets the standards. The regeneration process of ion exchange resins is as follows: cation exchange resins are regenerated by soaking in a 5% hydrochloric acid solution at a regeneration temperature of 40℃ for 1 hour; anion exchange resins are regenerated by soaking in a 4% sodium hydroxide solution at a regeneration temperature of 40℃ for 1 hour. The mixed ion exchange bed first regenerates the anion resins with an alkaline solution, then regenerates the cation resins with an acid solution. After regeneration, the effluent is rinsed with deionized water until the pH value of the effluent is 6.5-7.5 before it can be put into use again.

[0026] S5. Resource recovery stage: Collect sludge and waste adsorbent generated in each treatment stage and carry out in-situ resource recovery treatment.

[0027] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A wastewater filtration treatment method, characterized in that, Includes the following steps: S1. Pretreatment stage: The wastewater to be treated is introduced into the equalization tank, and the pH value of the wastewater is adjusted to 6.5-7.5 by pH adjuster. At the same time, modified diatomaceous earth adsorbent is added. The modified diatomaceous earth adsorbent is obtained by soaking and modifying in 5-8% aluminum chloride solution, drying and pulverizing, with a particle size of 80-120 mesh. The addition amount is 0.3-0.5% of the wastewater mass. The stirring rate is 200-300 r / min, the stirring time is 20-30 min, and the mixture is allowed to stand for 1-2 h to remove suspended particulate matter and some organic pollutants, thus obtaining pretreated wastewater. S2, Composite Membrane Filtration Stage: The pretreated wastewater is pumped to the composite membrane module via a pressurized pump. The composite membrane module is composed of a surface polyvinylidene fluoride ultrafiltration membrane, a middle polyamide nanofiltration membrane, and a bottom ceramic support membrane. The surface ultrafiltration membrane has a pore size of 50-100 nm, the middle nanofiltration membrane has a pore size of 1-5 nm, the pressurization pressure is controlled at 0.3-0.5 MPa, and the filtration temperature is 25-35℃ to obtain the primary filtrate. S3, Advanced Oxidation-Adsorption Coupled Filtration Stage: The primary filtrate is introduced into the integrated reaction filtration tank. The COD content is first detected using an online water quality monitor. Then, ferrous ion catalyst and sodium persulfate oxidant are added at 1.2-1.5 times the COD content. After addition, the mixture is stirred for 10 minutes. Ozone is then introduced at a rate of 0.9-1.1 mg / L, with a residence time of 15 minutes. Simultaneously, intermittent ultraviolet irradiation is activated. The ultraviolet wavelength is 254 nm, and the power is 120-140 W. The irradiation mode is 5 minutes of irradiation followed by a 2-minute pause, repeated until the reaction is complete. The total reaction time is 32-38 minutes. During the reaction, the filtrate is simultaneously filtered through a double-layer modified activated carbon filter layer. The upper layer is granular modified activated carbon, and the lower layer is powdered modified activated carbon, with a total thickness of 10-11 cm and a filtration rate of 1.2-1.8 m / h. The waste carbon layer produced during filtration is collected and used as a conditioner in the anaerobic digester to obtain the intermediate filtrate. S4. Deep purification stage: The intermediate filtrate is introduced into the ion exchange column and treated by ion exchange through a mixed bed of cation exchange resin and anion exchange resin. The volume ratio of cation exchange resin to anion exchange resin is 1:1.2-1:1.5, and the treatment flow rate is 0.5-1m / h. Then, it is disinfected by an ultraviolet sterilizer for 15-20 minutes to obtain treated water that meets the standards. S5. Resource recovery stage: Collect sludge and waste adsorbent generated in each treatment stage and carry out in-situ resource recovery treatment.

2. The wastewater filtration treatment method according to claim 1, characterized in that, In step S1, when the wastewater to be treated is introduced into the equalization tank, large debris with a particle size ≥5mm is first removed by a screen. The pH adjuster is a compound adjuster, which is composed of 12-14% hydrochloric acid solution, 9-11% sodium hydroxide solution and 0.5% potassium dihydrogen phosphate solution in a volume ratio of 5:5:

1. It can maintain the pH value of wastewater within the target range of ±0.

1.

3. The wastewater filtration treatment method according to claim 2, characterized in that, In step S1, the sludge produced by static sedimentation is introduced into the anaerobic digester. The biogas produced in the anaerobic digester is desulfurized by a desulfurization tower to remove hydrogen sulfide, then stored in a gas storage tank, and then used by a biogas burner to provide a heat source for the temperature control tank and the membrane module heat treatment process. The waste heat is recovered by a heat exchanger for heating in the ion exchange resin regeneration stage, thus realizing energy recycling.

4. The wastewater filtration treatment method according to claim 1, characterized in that, In step S2, the surface-modified polyvinylidene fluoride ultrafiltration membrane is modified with dopamine grafting and has a porosity of 75-80%; the middle-layer cross-linked polyamide nanofiltration membrane is prepared by cross-linking piperazine and trimesoyl chloride; the bottom ceramic support membrane is an alumina-zirconia composite ceramic with a pore size of 200-300 nm and a thickness of 3-5 mm.

5. The wastewater filtration treatment method according to claim 4, characterized in that, In step S2, when the membrane flux drops to 70% of the initial flux, online flushing is initiated. The online flushing first uses a sodium hydroxide solution with a mass fraction of 0.6-0.8% at room temperature for 35 minutes and a flushing flow rate of 0.8 m / s. Then, it uses a hydrochloric acid solution with a mass fraction of 0.4% at room temperature for 35 minutes. Finally, it is rinsed with deionized water until the pH of the effluent is neutral. After flushing, the membrane flux recovers to more than 90% of the initial flux.

6. The wastewater filtration treatment method according to claim 1, characterized in that, In step S3, the ultraviolet irradiation device uses multiple sets of ring lamps evenly arranged on the inner wall of the reaction filtration tank. The distance between the lamps and the tank wall is 15-20cm, and the distance between adjacent lamps is 30cm, to ensure that the primary filtrate is uniformly illuminated and the ultraviolet light intensity is maintained at 10-12mW / cm² in the reaction area.

7. The wastewater filtration treatment method according to claim 1, characterized in that, In step S4, the regeneration process of the ion exchange resin is as follows: the cation exchange resin is regenerated by soaking in a 5% hydrochloric acid solution at a regeneration temperature of 40°C for 1 hour; the anion exchange resin is regenerated by soaking in a 4% sodium hydroxide solution at a regeneration temperature of 40°C for 1 hour; the mixed ion exchange bed first regenerates the anion resin with an alkaline solution, and then regenerates the cation resin with an acid solution. After regeneration, the effluent is rinsed with deionized water until the pH value of the effluent is 6.5-7.5 before it can be put into use again.

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