A sewage treatment method and system based on upflow stirring mode for efficiently saving medicaments

Abstract

The present application relates to sewage treatment technical field, especially to a kind of sewage treatment method and sewage treatment system based on upflow stirring mode high-efficiency saving reagent for effluent after biochemical treatment, utilize packing in system large circulation and carry out pollutant enrichment, improve local pollutant concentration, promote the chain reaction of advanced oxidation;Using ferrous sulfate pre-adding method improves local ferrous concentration, enhances ferrous catalytic ability, promotes reagent mixing by upflow mixing method, reduces waste reagent caused by effluent hydrogen peroxide residue, while treating the pollutant adsorbed by packing, regenerate packing, finally achieve the purpose of reducing fenton reagent dosage, suitable for treating various biochemical tail water.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a wastewater treatment method and system based on an upflow mixing method for treating effluent after biological treatment. The main purpose is to utilize packing material in a large-scale circulation within the system to enrich pollutants, increase local pollutant concentrations, and promote chain reactions of advanced oxidation. The method uses ferrous sulfate pre-dosing to increase local ferrous concentration and enhance ferrous catalytic activity. Upflow mixing promotes reagent mixing, reducing reagent waste caused by residual hydrogen peroxide in the effluent. The system treats pollutants adsorbed by the packing material while simultaneously regenerating the packing material, ultimately reducing the amount of Fenton reagent required. This method is suitable for treating various types of biological effluent. Background Technology

[0002] Fenton oxidation is a core process that utilizes Fe²⁺ to catalyze the generation of hydroxyl radicals from H₂O₂ to degrade pollutants, but traditional Fenton technology suffers from three major drawbacks: High chemical costs: Ferrous sulfate, hydrogen peroxide, and other chemicals are consumed in large quantities, resulting in poor operational economy; Iron sludge is difficult to dispose of: If the iron sludge generated by the reaction is discharged directly, it will waste resources and increase the burden of solid waste treatment. Low processing efficiency: Conventional Fenton hydraulic retention time (HRT) is long, and the gas attached to the iron sludge causes the flocs to float, affecting the sludge-water separation effect.

[0003] To address the shortcomings of existing Fenton oxidation processes, numerous Fenton-like technologies have been developed. However, due to their suspended reaction mechanism and particle-fluid interaction characteristics, they suffer from significant deficiencies in catalyst recovery, operating condition adaptability, engineering scale-up, energy consumption costs, and mass transfer efficiency. Although some problems have been alleviated in recent years through improvements in reactor structure (such as multi-stage reactors and internal circulation reactors) and optimization of particle characteristics (such as high-strength biological packing materials), these limitations remain the main obstacles to the further promotion and application of Fenton-like technologies.

[0004] The purpose of this invention is to provide a wastewater treatment method and system based on an upflow stirring method that is efficient and saves on chemicals. Through an upflow coupled packing dynamic reuse process of "pre-adsorption of chemicals - Fenton reaction - post-treatment", the high adsorption capacity of porous packing is used to increase the local concentration of pollutants, and the upflow is used to enhance the Fenton reaction rate, thereby achieving chemical saving, high efficiency and resource recycling. Summary of the Invention

[0005] To address the issues of high cost and high iron sludge content in conventional Fenton treatment agents, and in light of the aforementioned background technology, this invention provides a dynamic reuse process for upflow coupled packing material, consisting of "pre-adsorption with added chemicals - Fenton reaction - post-treatment". The main content is: a wastewater treatment system and method based on upflow stirring, which is highly efficient and saves on chemicals.

[0006] The technical solution of the present invention is as follows: A wastewater treatment method based on upflow stirring is highly efficient and economical in terms of reagents. The wastewater treatment system used in this method includes a pre-adsorption and reagent dosing unit, a Fenton reaction unit, and a post-treatment unit. Pre-adsorption and reagent dosing unit: This unit pre-treats the biochemical effluent. The main structures include an equalization tank and a first vertical flow sedimentation tank. The packing material separated from the second vertical flow sedimentation tank is pumped to the equalization tank inlet pipe and fed into the equalization tank for adsorption for 1-30 minutes. During the pre-adsorption of pollutants by the packing material, sulfuric acid and ferrous sulfate are added to the equalization tank and aerated and stirred evenly. The sulfuric acid effectively protects the ferrous sulfate from oxidation. The effluent then enters the first vertical flow sedimentation tank for sedimentation for 1-30 minutes. The packing material settled at the bottom is pumped separately into an upflow Fenton reactor. The effluent enters the upflow Fenton reactor through a water path. Part of the effluent passes through an online COD analyzer. Based on the online COD reading, the hydrogen peroxide dosage is calculated online. At this point, the molar ratio of hydrogen peroxide to COD is 0.3-5.

[0007] Fenton Reaction Unit: The Fenton reaction unit includes an upflow Fenton reactor with a hydraulic retention time of 1-30 minutes. It is internally filled with one or more porous packing materials that do not react with Fenton reagents, such as activated carbon, zeolite, lightweight ceramsite, or volcanic rock. The packing density is between 1-1.4 g / cm³, and the static packing volume is between 1 / 10 and 1 / 2 of the reactor's capacity. The packing needs to be fluidized to the outlet and enter the second vertical flow sedimentation tank with the water. The height difference between the outlet and circulation port of the upflow Fenton reactor is less than 30 cm. The hydrogen peroxide addition point is located at the packing layer to ensure thorough mixing of hydrogen peroxide and ferrous sulfate. At this point, the hydrogen peroxide concentration in the effluent does not exceed 10 mg / L.

[0008] Post-treatment unit: includes a second vertical flow sedimentation tank and an inclined plate sedimentation tank. The effluent from the upflow Fenton reactor enters the post-treatment unit, and the wastewater enters the second vertical flow sedimentation tank. The hydraulic retention time is 1-30 minutes. It is separated from the iron-containing effluent by gravity. The packing material is pumped to the equalization tank. The effluent enters the inclined plate sedimentation tank, and the pH value is adjusted to 6-8 with sodium hydroxide. At the same time, polyacrylamide is added to aid coagulation. The hydraulic retention time is 1-30 minutes. After that, the supernatant is discharged.

[0009] A further improvement of the present invention is: After the biochemical effluent enters the system, the porous packing material, after being regenerated by Fenton fluidized bed oxidation, is separated and then re-adsorbs organic matter from the wastewater in the equalization tank, causing local enrichment of pollutants. This allows for a chain reaction in the upflow Fenton reactor, reducing the amount of Fenton reagent required. Ferrous sulfate is added in the equalization tank to ensure pH compatibility and mixing uniformity. The low pH value in the equalization tank dissolves the small amount of iron precipitate attached to the packing material and improves the adsorption capacity of the porous packing material, ensuring high adsorption efficiency, preventing caking, and protecting the ferrous sulfate from oxidation in the equalization tank. Aeration and stirring not only ensure uniform mixing of the reagents but also allow the packing material to further remove attached iron solids through collision.

[0010] Adding hydrogen peroxide inside the reactor separates the hydrogen peroxide and iron mixing process, reducing ineffective consumption caused by excessively high local reagent concentrations. Furthermore, the initial addition of ferrous sulfate to achieve a high local ferrous concentration better catalyzes the hydrogen peroxide, ensuring the regeneration of the packing material within the reactor. The reactor is filled with one or more non-reactive particles (0.3-4 mm in diameter) consisting of activated carbon, zeolite, lightweight ceramsite, and volcanic rock, with a density of 1-1.4 g / cm³. This filling level (10%-50%) enhances mass transfer while avoiding side reactions. Increasing the upward flow velocity prevents iron sludge from adhering to the packing material, increasing its adsorption capacity, and preventing CO2 / O2 from adhering to iron flocs and causing subsequent precipitation, thus ensuring sedimentation efficiency. The HRT (High-Resolution Time) of the Fenton reaction section is only 1-30 minutes, and the overall system HRT is ≤60 minutes, demonstrating significant treatment efficiency.

[0011] The key features of this invention are: optimized existing Fenton oxidation processes, forming a large-scale reflux throughout the packing process. This not only increases the local concentration of pollutants and promotes chain reactions, but also reduces the amount of Fenton reagent required, while ensuring the stability of the adsorption-regeneration process. Furthermore, improvements to the Fenton reactor enhance reagent mass transfer and ensure sedimentation efficiency, thereby reducing wastewater treatment costs for enterprises. This invention provides a simpler, more energy-efficient, and easier-to-control Fenton treatment method for treating biological effluent. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a highly efficient and chemical-saving wastewater treatment system based on an upflow stirring method. Figure Labels

[0013] 1-Effluent from biological treatment tank; 2-Equalization tank; 3-Sulfuric acid; 4-Ferrous sulfate; 5-First vertical flow sedimentation tank; 6-Online COD analyzer; 7-Upflow Fenton reactor; 8-Hydrogen peroxide; 9-Packaging material; 10-Second vertical flow sedimentation tank; 11-Inclined plate sedimentation tank; 12-Sodium hydroxide; 13-PAM; 14-Sludge pump one; 15-Sludge pump two; 16-Circulation pump; 17-Iron sludge; I-Pre-adsorption and reagent dosing unit; II-Fenton reaction unit; III-Sedimentation unit. Detailed Implementation

[0014] The invention will be further described below with reference to the accompanying drawings and examples: Figure 1 This is a schematic diagram of a highly efficient and chemical-saving wastewater treatment system based on an upflow stirring method.

[0015] Establishing the Fenton reaction process as follows Figure 1 As shown, the internal operation of this process flow is described as follows: When the effluent 1 from the biological treatment tank enters the system, the packing material 9 separated from the second vertical flow sedimentation tank 10 directly enters the equalization tank 2. After adding sulfuric acid 3 and ferrous sulfate 4, it undergoes pre-adsorption for 1-30 minutes through aeration and stirring. Then, the mixture enters the first vertical flow sedimentation tank 5 for sedimentation for 1-30 minutes. Here, the packing material 9 is pumped by sludge pump 2 14. Part of the first vertical flow sedimentation tank 5 passes through the online COD analyzer 6. Based on the value displayed by the online COD analyzer 6, the dosage of hydrogen peroxide 8 is calculated online. At this time, the molar ratio of hydrogen peroxide 8 to COD is 0.3-5.

[0016] The effluent from the first vertical flow sedimentation tank 5 enters the upflow Fenton reactor 7, with a hydraulic retention time of 1-30 minutes. The upflow Fenton reactor 7 is filled with packing material 9, which is mainly composed of one or more types of particles with a particle size of 0.3-4 mm and the same density that do not react with Fenton reagent, consisting of activated carbon, zeolite, lightweight ceramsite, and volcanic rock. The packing density is between 1.0-1.4 g / cm³. The static height of the packing material 9 is between 1 / 10 and 1 / 2 of the height of the upflow Fenton reactor 7, and it needs to be fluidized by the circulation pump 16. The hydrogen peroxide 8 is added at the packing layer to ensure that the hydrogen peroxide 8 and ferrous sulfate 4 are fully mixed. The upflow Fenton reactor 7 is circulated by the return pump 16. To ensure that the packing material can be effectively discharged from the reactor, the height difference between the outlet and the circulation port of the upflow Fenton reactor is less than 30 cm.

[0017] The effluent from the upflow Fenton reactor 7 enters the second vertical flow sedimentation tank 10, where the packing material and the mixture of water and iron sludge are separated. The packing material and a small amount of settled iron sludge are pumped into the equalization tank 2 via sludge pump 2 15. The supernatant enters the inclined plate sedimentation tank 11, where the pH is adjusted using sodium hydroxide 12, and polyacrylamide 13 is added to aid coagulation. The hydraulic retention time is 1-30 minutes, after which the supernatant and the generated iron sludge 17 are discharged. The total hydraulic retention time of this system is less than 60 minutes. Example 1

[0018] Leather wastewater biological treatment pond effluent treatment Wastewater quality: taken from the effluent of the biological treatment tank of a leather processing plant, COD=120 mg / L, pH=8.01.

[0019] Process parameters:

[0020] Pre-adsorption and reagent addition unit: Pre-adsorption time in the equalization tank is 10 min, sedimentation time in the first sedimentation tank is 15 min, and the packing material is 100% fed into the upflow Fenton reactor; sulfuric acid (98% concentrated sulfuric acid) is added to the equalization tank to adjust the pH value, and ferrous sulfate (10% aqueous solution) is added and mixed evenly with sulfuric acid. Fenton reactor unit: Upflow Fenton reactor with an effective volume of 2 m³ and a hydraulic retention time of 10 min; internally filled with activated carbon (particle size 0.5–3 mm, density 1.01 g / cm³). 3 ) and zeolite (particle size 0.5–1.1 mm, density 1.01 g / cm³) 3 The packing material is mixed in a 1:1 mass ratio and the static filling height is 1 / 5 of the reactor height. The entire reactor is fluidized. The molar ratio of hydrogen peroxide (30% industrial grade) to COD is 2:1. Post-treatment unit: The sedimentation time in the second vertical flow sedimentation tank is 15 minutes. After that, the supernatant enters the inclined plate sedimentation tank, where sodium hydroxide (30% liquid alkali) is added to adjust the pH value, and polyacrylamide (0.1% mass fraction) is added to aid coagulation. The hydraulic retention time is 10 minutes, and the water and sludge are discharged separately.

[0021] Treatment results: Effluent COD = 40 mg / L; All reagent costs for the Fenton process are reduced by 35% compared to the traditional Fenton process; Iron sludge production is reduced by 40%. Example 2

[0022] Treatment of coking wastewater from biological treatment ponds Wastewater quality: taken from the effluent of a coking plant's biological treatment pond, COD=350 mg / L, pH=7.35.

[0023] Process parameters:

[0024] Pre-adsorption and reagent addition unit: Pre-adsorption time in the equalization tank is 5 min, sedimentation time in the first vertical flow sedimentation tank is 10 min, and 100% of the sedimentation packing is pumped into the upflow Fenton reactor; sulfuric acid (98% concentrated sulfuric acid) is added to the equalization tank to adjust the pH value, and ferrous sulfate (10% aqueous solution) is added and mixed evenly with sulfuric acid. Fenton reactor unit: Upflow Fenton reactor with an effective volume of 2 m³ and a hydraulic retention time of 15 min; internally filled with zeolite (particle size 0.7–1.3 mm, density 1.1 g / cm³). 3 ) and lightweight ceramsite (particle size 1–2 mm, density 1.1 g / cm³) 3 The packing material is mixed at a mass ratio of 1:2, and the static filling height is 1 / 6 of the reactor height. The entire reactor is fluidized. The molar ratio of hydrogen peroxide (30% industrial grade) to COD is 2:1. Post-treatment unit: The second vertical flow sedimentation tank is used for 5 minutes to separate the packing material from the water. The wastewater enters the second sedimentation tank and sodium hydroxide (30% liquid alkali) is added to adjust the pH value. Polyacrylamide (0.1% mass fraction) is added to aid coagulation. The hydraulic retention time is 8 minutes. Water and sludge are discharged separately.

[0025] Treatment results: Effluent COD = 90 mg / L; Fenton process costs 30% less than traditional Fenton process; Iron sludge production reduced by 45%. Example 3

[0026] Fertilizer wastewater biological treatment pond effluent treatment Wastewater quality: taken from the effluent of a biological treatment pond in a fertilizer plant, COD=200 mg / L, pH=7.46.

[0027] Process parameters:

[0028] Pre-adsorption and reagent addition unit: Pre-adsorption time in the equalization tank is 10 min, sedimentation time in the first vertical flow sedimentation tank is 8 min, sedimentation packing is 100% pumped into the upflow Fenton reactor, sulfuric acid (98% concentrated sulfuric acid) is added to the equalization tank to adjust the pH and then mixed evenly with ferrous sulfate (10% aqueous solution). Fenton reactor unit: Upflow Fenton reactor with an effective volume of 2 m³ and a hydraulic retention time of 10 min; internally filled with volcanic rock packing (particle size 1–2 mm, density 1.1 g / cm³). 3 The static filling height is 1 / 7 of the reactor height, and the entire reactor is fluidized; the molar ratio of hydrogen peroxide (30% industrial grade) to COD is 2:1. Post-treatment unit: The second vertical flow sedimentation tank is used for 8 minutes to separate the packing material from the water. The wastewater enters the second sedimentation tank and sodium hydroxide (30% liquid alkali) is added to adjust the pH value. Polyacrylamide (0.1% mass fraction) is added to aid coagulation. The hydraulic retention time is 8 minutes. Water and sludge are discharged separately.

[0029] Treatment results: Effluent COD = 30 mg / L; Fenton process costs 50% less than traditional Fenton process; Iron sludge production reduced by 60%. Comparative Example 1

[0030] Treatment of coking wastewater from biological treatment ponds Wastewater quality: taken from the effluent of a coking plant's biological treatment pond, COD=350 mg / L, pH=7.35.

[0031] Process parameters:

[0032] Pre-adsorption and reagent dosing unit: only the equalization tank is used to add sulfuric acid (98% concentrated sulfuric acid) to adjust the pH value, and ferrous sulfate (10% aqueous solution) is added and mixed evenly with the wastewater; Fenton reactor unit: Upflow Fenton reactor with an effective volume of 2 m³ and a hydraulic retention time of 10 min; internally filled with activated carbon (particle size 0.5–3 mm, density 1.01 g / cm³). 3 ) and zeolite (particle size 0.5–1.1 mm, density 1.01 g / cm³) 3 The packing material is mixed in a 1:1 mass ratio and the static filling height is 1 / 5 of the reactor height. The packing material expands to 1 / 3 of the reactor height. The molar ratio of hydrogen peroxide (30% industrial grade) to COD is 2:1. Post-treatment unit: Sodium hydroxide (30% liquid alkali) is added to the sedimentation tank to adjust the pH value, polyacrylamide (0.1% mass fraction) is added to aid coagulation, the hydraulic retention time is 10 min, and water and sludge are discharged separately.

[0033] Treatment results: Effluent COD = 120 mg / L; The cost of all chemicals in the Fenton process is only 11% lower than that of the traditional Fenton process; The amount of iron sludge produced is only reduced by 15%, and there is obvious iron sludge adhering to the packing after operation. Comparative Example 2

[0034] Leather wastewater biological treatment pond effluent treatment Wastewater quality: taken from the effluent of the biological treatment tank of a leather processing plant, COD=120 mg / L, pH=8.01.

[0035] Process parameters:

[0036] Pre-adsorption and reagent addition unit: Pre-adsorption time in the equalization tank is 3 min, sedimentation time in the first sedimentation tank is 10 min, and the packing material is a 100% upflow Fenton reactor; sulfuric acid (98% concentrated sulfuric acid) is added to the equalization tank to adjust the pH value; Fenton reactor unit: Upflow Fenton reactor with an effective volume of 2 m³ and a hydraulic retention time of 10 min; internally filled with activated carbon (particle size 0.5–3 mm, density 1.01 g / cm³).3 ) and zeolite (particle size 0.5–1.1 mm, density 1.01 g / cm³) 3 The packing material is mixed in a 1:1 mass ratio and the static height of the packing material is 1 / 5 of the reactor height. The entire reactor is fluidized. The molar ratio of hydrogen peroxide (30% industrial grade) to COD is 2:1. Ferrous sulfate (10% aqueous solution) is added together with hydrogen peroxide in the upflow Fenton reactor. Post-treatment unit: The sedimentation time in the second vertical flow sedimentation tank is 15 minutes. After that, the supernatant enters the inclined plate sedimentation tank, where sodium hydroxide (30% liquid alkali) is added to adjust the pH value, and polyacrylamide (0.1% mass fraction) is added to aid coagulation. The hydraulic retention time is 10 minutes, and the water and sludge are discharged separately.

[0037] Treatment results: Effluent COD = 50 mg / L; Fenton process costs 20% less than traditional Fenton process; Iron sludge production reduced by 30%.

Claims

1. A highly efficient and reagent-saving wastewater treatment method based on an upflow stirring method, characterized in that: The wastewater treatment system used in the method includes a pre-adsorption and reagent dosing unit (I), a Fenton reaction unit (II), and a post-treatment unit (III); wherein: Pre-adsorption and reagent addition unit (I): includes equalization tank (2) and first vertical flow sedimentation tank (5); the effluent (1) from the biochemical tank enters the equalization tank (2), the equalization tank (2) is provided with a packing material (9) inlet, the packing material (9) comes from the second vertical flow sedimentation tank (10) and is transported by sludge pump two (15); the equalization tank (2) is provided with a sulfuric acid (3) and ferrous sulfate (4) reagent addition area and an aeration and stirring device; the first vertical flow sedimentation tank (5) is used to separate the packing material (9) from the effluent of the equalization tank (2), the inlet of the first vertical flow sedimentation tank (5) is connected to the outlet of the equalization tank (2), and the packing material (9) settled at the bottom is sent into the upflow Fenton reactor (7) by sludge pump one (14); Fenton reactor unit (II): includes an upflow Fenton reactor (7), whose wastewater inlet is connected to the wastewater outlet of the first vertical flow sedimentation tank (5), and is filled with packing material (9); the upflow Fenton reactor (7) is ensured to be fully fluidized by a circulating pump (16); the effluent from the upflow Fenton reactor (7) is fed into the second vertical flow sedimentation tank (10). Post-treatment unit (III): includes a second vertical flow sedimentation tank (10) and an inclined plate sedimentation tank (11); the second vertical flow sedimentation tank (10) is used to separate the effluent from the upflow Fenton reactor (7) by packing (9) and send it to the equalization tank (2) by sludge pump two (15); the effluent from the second vertical flow sedimentation tank (10) is connected to the inlet of the inclined plate sedimentation tank (11), sodium hydroxide (12) is added to the inclined plate sedimentation tank (11) to adjust the pH value, and polyacrylamide (13) is added to aid coagulation. After sedimentation, the supernatant and iron sludge (17) from the inclined plate sedimentation tank (11) are discharged separately.

2. The method as described in claim 1, characterized in that: The packing material (9) is composed of one or more of activated carbon, zeolite, lightweight ceramsite and volcanic rock, and the density of the packing material (9) is 1.0-1.4 g / cm³; the static height of the packing material (9) is 1 / 10-1 / 2 of the height of the upflow Fenton reactor (7); the height difference between the outlet and the circulation port of the upflow Fenton reactor (7) is less than 30 cm.

3. The method as described in claim 1, characterized in that: The pre-adsorption time of the equalization tank (2) is 1-30 minutes, and the stirring method is aeration stirring.

4. The method as described in claim 1, characterized in that: The sedimentation time in the first vertical flow sedimentation tank (5) is 1-30 minutes.

5. The method as described in claim 1, characterized in that: In the upflow Fenton reactor (7), the hydrogen peroxide (8) is added at the packing layer, and the reaction time is 1-30 minutes.

6. The method as described in claim 1, characterized in that: The hydraulic retention time of the second vertical flow sedimentation tank (10) is 1-30 minutes.

7. The method as described in claim 1, characterized in that: The hydraulic retention time of the inclined plate sedimentation tank (11) is 1-30 minutes.

8. The method as described in claim 1, characterized in that: The total hydraulic residence time is less than 60 minutes.

9. A highly efficient and reagent-saving wastewater treatment system based on an upflow stirring method, characterized in that: The wastewater treatment system includes the pre-adsorption and reagent dosing unit (I), the Fenton reaction unit (II), and the post-treatment unit (III) as described in claim 1.

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