A method for resourceful treatment of high-salt organic wastewater in a dye production process

Abstract

The application provides a resourceful treatment method of high-salt organic wastewater in a dye production process, and relates to the technical field of sewage treatment. The resourceful treatment method of high-salt organic wastewater in the dye production process comprises the following steps: S1. collecting high-salt organic wastewater discharged by a dye production workshop, and making the wastewater enter a homogenizing adjusting tank; S2. realizing the balance of wastewater quality and quantity through stirring and residence time control of the homogenizing adjusting tank, and adjusting the wastewater pH value to 6.0-8.0 by using a dilute acid or a dilute alkali solution. The application provides a resourceful treatment method of high-salt organic wastewater in a dye production process, through accurate control of persulfate oxidation conditions, selectively modifies the refractory macromolecular organic matter in the wastewater into specific intermediates containing hydrophilic groups, and uses a special flocculating agent to efficiently separate and dry the intermediates, and converts the intermediates into chemical raw materials with market value, so that the resourceful recovery of the organic matter is realized.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for the resource-based treatment of high-salt organic wastewater from dye production processes. Background Technology

[0002] The production process of dyes (such as reactive dyes, acid dyes, disperse dyes, etc.) involves multiple unit operations such as nitration, reduction, coupling, and salting out, which inevitably generates a large amount of complex high-concentration organic wastewater. This type of wastewater not only contains aromatic organic compounds that are difficult to biodegrade, such as benzene series, naphthalene series, anthraquinones, and azo compounds, but also has high color and high toxicity. In addition, due to the large amount of inorganic salts (mainly sodium chloride and sodium sulfate) used in the production process for salting out, separation and purification, the salt concentration of the wastewater is extremely high, usually reaching 5% to 20% or even higher, forming typical high-salt organic wastewater. This "three-high" characteristic of high salt, high organic matter and high color makes it a recognized problem in the field of industrial wastewater treatment.

[0003] Currently, most methods involve mixing high-salinity wastewater with large amounts of low-salinity wastewater to dilute it to a level tolerable for microorganisms before it enters a conventional biological treatment system. While this method is simple, the severe dilution results in large treatment facilities, high investment and operating costs, and it does not truly remove salt and recalcitrant organic matter. To improve biodegradability, advanced oxidation technologies such as Fenton oxidation, ozone oxidation, and wet catalytic oxidation are often used as pretreatment to break down large organic molecules into smaller molecules before entering the biological treatment system. However, advanced oxidation processes aim to indiscriminately mineralize organic matter, resulting in huge energy and reagent consumption and extremely high treatment costs.

[0004] Therefore, a resource-based treatment method for high-salt organic wastewater in dye production is proposed to address the above problems. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a method for the resource-based treatment of high-salt organic wastewater in the dye production process, solving the long-standing problems of low resource recovery rate, low product value, and difficult final disposal in the treatment of high-salt organic wastewater in the dye industry.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for the resource-based treatment of high-salinity organic wastewater from dye production includes the following steps:

[0010] S1. Collect the high-salt organic wastewater discharged from the dye production workshop and let the wastewater enter the homogenization and equalization tank;

[0011] S2. The wastewater quality and quantity are balanced by stirring and controlling the residence time in the homogenization tank, and the pH value of the wastewater is adjusted to 6.0-8.0 using dilute acid or dilute alkali solution.

[0012] S3. Pump the adjusted wastewater into the advanced oxidation reactor, and add persulfate based on the real-time COD detection value of the wastewater, calculated at 25%-40% of the theoretical amount of reagent required for complete oxidation.

[0013] S4. Simultaneously add ferrous sulfate catalyst and control the molar ratio of persulfate to ferrous sulfate to be (8:1)-(15:1).

[0014] S5. Start the stirring and heating system to allow the reaction to proceed. During the reaction, through the chain breaking and oxidative modification of some organic molecules, the molecular weight distribution is shifted to the range of 500Da-3000Da, and carboxyl groups, sulfonic acid groups or hydrophilic groups are introduced.

[0015] S6. After the reaction is complete, the effluent enters the intermediate buffer tank, ready for flocculation separation;

[0016] S7. The oxidized wastewater is introduced into the flocculation reaction tank at a controllable flow rate, and zwitterionic polymeric flocculant is added.

[0017] S8. During the flocculation process, a rapid mixing stage and a slow flocculation stage are carried out respectively. After flocculation is completed, the mixture enters an immersion centrifuge or a high-efficiency sedimentation tank for solid-liquid separation.

[0018] S9. The separated organic enriched sludge is conveyed to the drying system by a screw conveyor and dried at 80℃-110℃ with a moisture content of ≤10%, yielding a dark brown particulate product.

[0019] S10. Collect the supernatant and then filter it through a precision filter to remove residual suspended particles;

[0020] S11. The filtrate enters the fouling-resistant disc tube reverse osmosis system:

[0021] (1) The operating pressure is set to 4.0-7.0 MPa;

[0022] (2) The system controls the freshwater recovery rate to be 70%-80%;

[0023] (3) The high-quality freshwater generated is directly reused in production or discharged in compliance with standards;

[0024] (4) DTRO concentrate enters the next unit;

[0025] S12. DTRO concentrate enters the selective electroosmosis system:

[0026] (1) The SED membrane stack uses a special ion exchange membrane with higher selectivity for monovalent ions than for divalent ions;

[0027] (2) Operate under the conditions of DC voltage 15-30 V / membrane pair and flow rate 3-6 cm / s;

[0028] (3) The mixed salt is separated into concentrated stream A and concentrated stream B by selective migration of the membrane;

[0029] (4) The permeate from the desalination chamber of the SED system is returned to the DTRO inlet for further concentration;

[0030] (5) Monitor the ion concentration of concentrate streams A and B in real time, control the concentration ratio, and ensure that concentrate streams A and B meet the feed requirements for subsequent salt separation and crystallization;

[0031] S13. Pump the concentrated stream A into the MVR evaporator crystallizer and control the evaporation temperature at 70℃-85℃. When the NaCl concentration reaches saturation, start the crystallization process. By adding seed crystals and controlling the supersaturation, uniform sodium chloride crystals are produced. The crystal slurry is centrifuged, washed with a small amount of pure water, and dried in a fluidized bed to obtain industrial-grade sodium chloride.

[0032] S14. At the same time, the concentrated stream B is pumped into another MVR evaporator crystallizer, the evaporation temperature is controlled at 95℃-105℃, the cooling rate is controlled during the crystallization process, and anhydrous sodium sulfate crystals are obtained. After centrifugation, washing and drying, the crystal slurry is used to obtain industrial grade anhydrous sodium sulfate.

[0033] S15. The mother liquor from both crystallization systems can be partially recycled to the concentrate end of the upstream SED or DTRO process to improve the overall recovery rate. A small amount of final mother liquor can be returned to the advanced oxidation step for deep treatment, achieving a high proportion of wastewater reuse and waste resource utilization within the system, with extremely low wastewater discharge.

[0034] Preferably, in step S2, the stirring speed is 100rpm-400rpm and the residence time is 4h-12h.

[0035] Preferably, the advanced oxidation reactor in step S3 is made of corrosion-resistant material and has both a stirring mechanism and a heating mechanism, wherein the amount of persulfate added is 0.5 g to 1.2 g per gram of COD.

[0036] Preferably, in step S5, the stirring system speed is 80 rpm-150 rpm, the reaction temperature is 40℃-55℃, and the reaction time is 15 minutes-30 minutes.

[0037] Preferably, the zwitterionic polymeric flocculant in step S7 has the structure of acrylamide, methacryloyloxyethyltrimethylammonium chloride, and methacrylic acid copolymer, and the dosage is adjusted to 20 mg / L-60 mg / L according to the TOC concentration in the wastewater.

[0038] Preferably, in step S8, the speed of the rapid mixing stage is 200rpm-300rpm and the time is 1 minute-2 minutes, while the speed of the slow flocculation stage is 40rpm-60rpm and the time is 8 minutes-15 minutes.

[0039] Preferably, the precision of the security filter in step S10 is 5μm-10μm.

[0040] Preferably, the dark brown granular product in step S9 contains carboxylates, sulfonates, and active components, and can be utilized as a dye dispersant or building material additive.

[0041] Preferably, in step S11, the high-quality freshwater has a conductivity ≤ 200 μS / cm, COD ≤ 50 mg / L, and the salinity of the DTRO concentrate is 12%-25%.

[0042] Preferably, in step S12, the concentrated stream A is rich in NaCl and Cl. - SO4 2- Mass ratio >10:1, concentrated stream B is rich in Na2SO4, SO4 2- / CI - Mass ratio > 8:1.

[0043] (III) Beneficial Effects

[0044] This invention provides a method for the resource-based treatment of high-salinity organic wastewater from dye production processes. It offers the following advantages:

[0045] 1. This invention provides a resource-based treatment method for high-salt organic wastewater in dye production. By precisely controlling the oxidation reaction conditions based on sulfate free radicals, the originally toxic and difficult-to-degrade macromolecular organic matter is selectively modified into intermediates containing specific functional groups, rather than pursuing complete mineralization. Subsequently, a specially formulated zwitterionic polymeric flocculant is used to efficiently capture these modified intermediates, forming easily separable organic-enriched sludge. After simple treatment, this sludge can be directly used as a raw material for low-quality dye dispersants or building material additives, thus realizing for the first time the transformation of harmful organic matter in dye wastewater into bulk chemical products with market value.

[0046] 2. This invention provides a resource-based treatment method for high-salt organic wastewater during dye production. By utilizing selective electrodialysis as a salt separation hub, sodium chloride and sodium sulfate in the pretreated concentrated brine are efficiently pre-separated using ion exchange membranes with different selectivities for monovalent and divalent ions before evaporation and crystallization. This yields two high-purity single-salt concentrates, which are then subjected to independent evaporation and crystallization to ultimately obtain sodium chloride and sodium sulfate crystals with purity meeting industrial standards. This process completely breaks the predicament that high-salt organic wastewater can only produce hazardous waste containing mixed salts. For the first time, it realizes a closed-loop cycle from mixed waste salts to commercial products, solving the most critical problem of inorganic salt disposal in resource-based treatment. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] Example:

[0049] A method for the resource-based treatment of high-salinity organic wastewater from dye production includes the following steps:

[0050] S1. Collect the high-salt organic wastewater discharged from the dye production workshop and let the wastewater enter the homogenization and equalization tank;

[0051] S2. The wastewater quality and quantity are balanced by stirring and controlling the residence time in the homogenization tank, and the pH value of the wastewater is adjusted to 6.0-8.0 using dilute acid or dilute alkali solution.

[0052] S3. Pump the adjusted wastewater into the advanced oxidation reactor, and add persulfate based on the real-time COD detection value of the wastewater, calculated at 25%-40% of the theoretical amount of reagent required for complete oxidation.

[0053] S4. Simultaneously add ferrous sulfate catalyst and control the molar ratio of persulfate to ferrous sulfate to be (8:1)-(15:1).

[0054] S5. Start the stirring and heating system to allow the reaction to proceed. During the reaction, through the chain breaking and oxidative modification of some organic molecules, the molecular weight distribution is shifted to the range of 500Da-3000Da, and carboxyl groups, sulfonic acid groups or hydrophilic groups are introduced.

[0055] S6. After the reaction is complete, the effluent enters the intermediate buffer tank, ready for flocculation separation;

[0056] S7. The oxidized wastewater is introduced into the flocculation reaction tank at a controllable flow rate, and zwitterionic polymeric flocculant is added.

[0057] S8. During the flocculation process, a rapid mixing stage and a slow flocculation stage are carried out respectively. After flocculation is completed, the mixture enters an immersion centrifuge or a high-efficiency sedimentation tank for solid-liquid separation.

[0058] S9. The separated organic enriched sludge is conveyed to the drying system by a screw conveyor and dried at 80℃-110℃ with a moisture content of ≤10%, yielding a dark brown particulate product.

[0059] S10. Collect the supernatant and then filter it through a precision filter to remove residual suspended particles;

[0060] S11. The filtrate enters the fouling-resistant disc tube reverse osmosis system:

[0061] (1) The operating pressure is set to 4.0-7.0 MPa;

[0062] (2) The system controls the freshwater recovery rate to be 70%-80%;

[0063] (3) The high-quality freshwater generated is directly reused in production or discharged in compliance with standards;

[0064] (4) DTRO concentrate enters the next unit;

[0065] S12. DTRO concentrate enters the selective electroosmosis system:

[0066] (1) The SED membrane stack uses a special ion exchange membrane with higher selectivity for monovalent ions than for divalent ions;

[0067] (2) Operate under the conditions of DC voltage 15-30 V / membrane pair and flow rate 3-6 cm / s;

[0068] (3) The mixed salt is separated into concentrated stream A and concentrated stream B by selective migration of the membrane;

[0069] (4) The permeate from the desalination chamber of the SED system is returned to the DTRO inlet for further concentration;

[0070] (5) Monitor the ion concentration of concentrate streams A and B in real time, control the concentration ratio, and ensure that concentrate streams A and B meet the feed requirements for subsequent salt separation and crystallization;

[0071] S13. Pump the concentrated stream A into the MVR evaporator crystallizer and control the evaporation temperature at 70℃-85℃. When the NaCl concentration reaches saturation, start the crystallization process. By adding seed crystals and controlling the supersaturation, uniform sodium chloride crystals are produced. The crystal slurry is centrifuged, washed with a small amount of pure water, and dried in a fluidized bed to obtain industrial-grade sodium chloride.

[0072] S14. At the same time, the concentrated stream B is pumped into another MVR evaporator crystallizer, the evaporation temperature is controlled at 95℃-105℃, the cooling rate is controlled during the crystallization process, and anhydrous sodium sulfate crystals are obtained. After centrifugation, washing and drying, the crystal slurry is used to obtain industrial grade anhydrous sodium sulfate.

[0073] S15. The mother liquor from both crystallization systems can be partially recycled to the concentrate end of the upstream SED or DTRO process to improve the overall recovery rate. A small amount of final mother liquor can be returned to the advanced oxidation step for deep treatment, achieving a high proportion of wastewater reuse and waste resource utilization within the system, with extremely low wastewater discharge.

[0074] In step S2, the stirring speed is 100 rpm-400 rpm, and the residence time is 4 h-12 h. In step S3, the advanced oxidation reactor is made of corrosion-resistant material and has both a stirring mechanism and a heating mechanism. The dosage of persulfate is 0.5 g-1.2 g per gram of COD. In step S5, the stirring system speed is 80 rpm-150 rpm, the reaction temperature is 40℃-55℃, and the reaction time is 15 minutes-30 minutes. In step S7, the zwitterionic polymeric flocculant has the structure of acrylamide, methacryloyloxyethyltrimethylammonium chloride, and methacrylic acid copolymer, and the dosage is determined by... The TOC concentration in the wastewater is adjusted to 20 mg / L-60 mg / L. In step S8, the rapid mixing stage has a rotation speed of 200 rpm-300 rpm and a time of 1-2 minutes, while the slow flocculation stage has a rotation speed of 40 rpm-60 rpm and a time of 8-15 minutes. In step S10, the security filter has a precision of 5 μm-10 μm. In step S9, the dark brown granular product contains carboxylates, sulfonates, and active components, and can be used as a dye dispersant or building material additive for resource utilization. In step S11, the high-quality freshwater has a conductivity ≤200 μS / cm and a COD ≤50 mg / L, with the DTRO concentrate having a salinity of 12%-25%. In step S12, the concentrated stream A is rich in NaCl and Cl. - SO4 2- Mass ratio >10:1, concentrated stream B is rich in Na2SO4, SO4 2- / CI - Mass ratio > 8:1.

[0075] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for the resource-based treatment of high-salinity organic wastewater from dye production, characterized in that: Includes the following steps: S1. Collect the high-salt organic wastewater discharged from the dye production workshop and let the wastewater enter the homogenization and equalization tank; S2. The wastewater quality and quantity are balanced by stirring and controlling the residence time in the homogenization tank, and the pH value of the wastewater is adjusted to 6.0-8.0 using dilute acid or dilute alkali solution. S3. Pump the adjusted wastewater into the advanced oxidation reactor, and add persulfate based on the real-time COD detection value of the wastewater, calculated at 25%-40% of the theoretical amount of reagent required for complete oxidation. S4. Simultaneously add ferrous sulfate catalyst and control the molar ratio of persulfate to ferrous sulfate to be (8:1)-(15:1). S5. Start the stirring and heating system to allow the reaction to proceed. During the reaction, through the chain breaking and oxidative modification of some organic molecules, the molecular weight distribution is shifted to the range of 500Da-3000Da, and carboxyl groups, sulfonic acid groups or hydrophilic groups are introduced. S6. After the reaction is complete, the effluent enters the intermediate buffer tank, ready for flocculation separation; S7. The oxidized wastewater is introduced into the flocculation reaction tank at a controllable flow rate, and zwitterionic polymeric flocculant is added. S8. During the flocculation process, a rapid mixing stage and a slow flocculation stage are carried out respectively. After flocculation is completed, the mixture enters an immersion centrifuge or a high-efficiency sedimentation tank for solid-liquid separation. S9. The separated organic enriched sludge is conveyed to the drying system by a screw conveyor and dried at 80℃-110℃ with a moisture content of ≤10%, yielding a dark brown particulate product. S10. Collect the supernatant and then filter it through a precision filter to remove residual suspended particles; S11. The filtrate enters the fouling-resistant disc tube reverse osmosis system: (1) The operating pressure is set to 4.0-7.0 MPa; (2) The system controls the freshwater recovery rate to be 70%-80%; (3) The high-quality freshwater generated is directly reused in production or discharged in compliance with standards; (4) DTRO concentrate enters the next unit; S12. DTRO concentrate enters the selective electroosmosis system: (1) The SED membrane stack uses a special ion exchange membrane with higher selectivity for monovalent ions than for divalent ions; (2) Operate under the conditions of DC voltage 15-30 V / membrane pair and flow rate 3-6 cm / s; (3) The mixed salt is separated into concentrated stream A and concentrated stream B by selective migration of the membrane; (4) The permeate from the desalination chamber of the SED system is returned to the DTRO inlet for further concentration; (5) Monitor the ion concentration of concentrate streams A and B in real time, control the concentration ratio, and ensure that concentrate streams A and B meet the feed requirements for subsequent salt separation and crystallization; S13. Pump the concentrated stream A into the MVR evaporator crystallizer and control the evaporation temperature at 70℃-85℃. When the NaCl concentration reaches saturation, start the crystallization process. By adding seed crystals and controlling the supersaturation, uniform sodium chloride crystals are produced. The crystal slurry is centrifuged, washed with a small amount of pure water, and dried in a fluidized bed to obtain industrial-grade sodium chloride. S14. At the same time, the concentrated stream B is pumped into another MVR evaporator crystallizer, the evaporation temperature is controlled at 95℃-105℃, the cooling rate is controlled during the crystallization process, and anhydrous sodium sulfate crystals are obtained. After centrifugation, washing and drying, the crystal slurry is used to obtain industrial grade anhydrous sodium sulfate. S15. The mother liquor from both crystallization systems can be partially recycled to the concentrate end of the upstream SED or DTRO process to improve the overall recovery rate. A small amount of final mother liquor can be returned to the advanced oxidation step for deep treatment, achieving a high proportion of wastewater reuse and waste resource utilization within the system, with extremely low wastewater discharge.

2. The method for resource-based treatment of high-salinity organic wastewater in dye production process according to claim 1, characterized in that: In step S2, the stirring speed is 100rpm-400rpm and the residence time is 4h-12h.

3. The method for resource-based treatment of high-salinity organic wastewater in dye production process according to claim 1, characterized in that: In step S3, the advanced oxidation reactor is made of corrosion-resistant material and is equipped with both a stirring mechanism and a heating mechanism. The amount of persulfate added is 0.5-1.2 grams per gram of COD.

4. The method for resource-based treatment of high-salinity organic wastewater in dye production process according to claim 1, characterized in that: In step S5, the stirring system rotates at 80 rpm to 150 rpm, the reaction temperature is between 40℃ and 55℃, and the reaction time is between 15 minutes and 30 minutes.

5. The method for resource-based treatment of high-salinity organic wastewater in dye production process according to claim 1, characterized in that: In step S7, the zwitterionic polymeric flocculant has the structure of acrylamide, methacryloyloxyethyltrimethylammonium chloride, and methacrylic acid copolymer, and the dosage is adjusted to 20 mg / L-60 mg / L according to the TOC concentration in the wastewater.

6. The method for resource-based treatment of high-salinity organic wastewater in dye production process according to claim 1, characterized in that: In step S8, the speed of the rapid mixing stage is 200-300 rpm and the time is 1-2 minutes, while the speed of the slow flocculation stage is 40-60 rpm and the time is 8-15 minutes.

7. The method for resource-based treatment of high-salinity organic wastewater in dye production process according to claim 1, characterized in that: The precision of the security filter in step S10 is 5μm-10μm.

8. The method for resource-based treatment of high-salinity organic wastewater in dye production process according to claim 1, characterized in that: The dark brown granular product in step S9 contains carboxylates, sulfonates, and active components, and can be utilized as a dye dispersant or building material additive.

9. A method for resource-based treatment of high-salinity organic wastewater in dye production process according to claim 1, characterized in that: In step S11, the high-quality freshwater has a conductivity ≤ 200 μS / cm and a COD ≤ 50 mg / L, with the DTRO concentrate having a salinity of 12%-25%.

10. A method for resource-based treatment of high-salinity organic wastewater in dye production process according to claim 1, characterized in that: In step S12, the concentrated stream A is rich in NaCl and Cl. - SO4 2- Mass ratio >10:1, concentrated stream B is rich in Na2SO4, SO4 2- / CI - Mass ratio > 8:1.