Two-stage ozone treatment process for printing and dyeing wastewater

Abstract

The application relates to a two-stage ozone treatment printing and dyeing wastewater process and relates to the technical field of industrial wastewater treatment processes, which mainly comprises three treatment systems, namely, a first-stage ozone catalytic oxidation system, a biochemical treatment system and a second-stage ozone catalytic oxidation system. The first-stage ozone catalytic oxidation system performs pre-oxidation on printing and dyeing wastewater; the biochemical treatment system is an AAO biochemical tank, has the functions of removing organic matters and denitrification and phosphorus removal, and has the advantages of low operation cost and small secondary pollution; the second-stage ozone catalytic oxidation system performs re-oxidation on residual organic matters after biochemical treatment, so that the effluent quality reaches the first-stage A standard of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB-18918-2002). The process can efficiently, economically, stably and reliably treat printing and dyeing wastewater, and the amount of generated sludge is small.

Description

Technical Field

[0001] This application relates to the technical field of industrial wastewater treatment processes, and in particular to a two-stage ozone treatment process for dyeing and printing wastewater. Background Technology

[0002] Dyeing and printing wastewater is characterized by its complex composition, deep color, and poor biodegradability. With the development of the dye industry and advancements in dyeing and printing processing technology, large amounts of non-biodegradable organic matter, such as PVA sizing agents, new auxiliaries, and new dyes, are entering the wastewater, significantly increasing the difficulty of treatment. Traditional processes (physical + biological methods) can generally handle single-source dyeing and printing wastewater, but are insufficient for treating complex, large-scale, high-emission-standard combined wastewater. Furthermore, the government is continuously raising the standards for wastewater from dyeing and printing enterprises entering the pipe network, meaning that most of the dyeing and printing wastewater received by wastewater treatment plants is already treated at the point source, characterized by high salinity and high biological toxicity. Moreover, the wastewater in these plants is a combination of wastewater from multiple dyeing and printing enterprises, making its composition even more complex. Against the backdrop of the national "upgrading" of wastewater reuse projects for dyeing and printing enterprises, the standards for wastewater reuse and discharge are constantly increasing, requiring not only the removal of organic matter but also good decolorization. All of these factors render existing processes inadequate to cope with increasingly complex wastewater and meet increasingly stringent emission standards.

[0003] Therefore, most wastewater treatment plants or dyeing and printing enterprises have begun to adopt advanced oxidation technologies such as Fenton oxidation and ozone oxidation at the end of the dyeing and printing wastewater treatment process to improve the treatment effect. Summary of the Invention

[0004] In order to solve the technical problems of high difficulty in treating dyeing and printing wastewater, low efficiency of single-stage ozone treatment, insufficient ozone utilization, unstable effluent quality, and inability to meet increasingly stringent emission standards in the existing technology, this application provides a two-stage ozone treatment process for dyeing and printing wastewater.

[0005] This application provides a two-stage ozone treatment process for dyeing and printing wastewater, which adopts the following technical solution: A two-stage ozone treatment process for dyeing and printing wastewater includes an equalization tank, a multi-effect separation tank, a first-stage ozone catalytic oxidation tank, an AAO biochemical tank, a secondary sedimentation tank, a second-stage ozone catalytic oxidation tank, and a BAF filter connected in sequence by pipelines. The dyeing and printing wastewater passes through each of the above treatment units in sequence through pipelines. Through staged pretreatment, primary oxidation, biochemical treatment, deep oxidation, and filtration, the wastewater is purified in stages, gradually degrading pollutants in the wastewater and ensuring that the effluent consistently meets standards.

[0006] Optionally, the interior of the Class II ozone catalytic oxidation tank is divided into a front-end aeration zone and a rear-end adsorption zone by a partition component, and the partition component is provided with a fluid communication channel; the rear-end adsorption zone is filled with porous catalytic adsorption packing, and a gas phase distribution device is provided at the bottom of the porous catalytic adsorption packing.

[0007] By adopting the above technical solution, the secondary ozone tank is divided into two functional zones. The front-end aeration zone first achieves preliminary mixing and mass transfer between ozone and wastewater, rapidly degrading most of the easily oxidizable pollutants in the wastewater. The back-end adsorption zone utilizes the adsorption effect of porous catalytic adsorption packing to enrich the residual recalcitrant pollutants in the wastewater. At the same time, the catalytic effect of the packing can activate ozone molecules, generating a large number of hydroxyl radicals, achieving deep oxidation of recalcitrant pollutants, while prolonging the contact time between pollutants and ozone, significantly improving the utilization rate of ozone and avoiding ineffective ozone dissipation.

[0008] Optionally, the separating component is a vertical partition, and the fluid communication channel is a through hole at the bottom of the vertical partition; the porous catalytic adsorption packing is granular activated carbon, and the gas phase distribution device is a microporous aeration disc.

[0009] By adopting the above technical solution, the through holes at the bottom allow wastewater to flow from the bottom of the aeration zone to the adsorption zone, ensuring the uniformity of water flow and avoiding short-circuiting problems; granular activated carbon itself has good adsorption performance and can also serve as a catalyst carrier to enhance the catalytic oxidation effect; the microporous aeration disc can generate tiny bubbles, effectively increasing the gas-liquid contact area, significantly improving mass transfer efficiency, and further enhancing the ozone solubility.

[0010] Optionally, the first-stage ozone catalytic oxidation tank is equipped with a water jet injector, which includes a water inlet, an air intake, and a mixing chamber. The air intake is connected to a gas source delivery pipeline.

[0011] By adopting the above technical solution, the water jet can efficiently draw in ozone gas using the pressure of the incoming water and achieve high-intensity gas-liquid mixing in the mixing chamber. Compared with traditional aeration methods, the water jet has a better gas-liquid mixing effect and higher ozone dissolution efficiency, avoiding ozone waste. At the same time, the structure is simple, the operation is stable, and the maintenance cost is low.

[0012] Optionally, the multi-effect separation tank includes a coagulation zone and a sedimentation zone, which are separated by a partition wall with water passage holes.

[0013] By adopting the above technical solution, the coagulation zone can achieve full mixing and reaction between the reagent and the wastewater, allowing colloidal pollutants in the wastewater to form flocs. Then, the sedimentation zone achieves solid-liquid separation, effectively removing suspended solids and some colloidal organic matter from the wastewater, reducing the load on subsequent treatment units, and at the same time avoiding the covering and passivation of subsequent ozone catalysts by suspended solids, thus ensuring the efficiency of catalytic oxidation.

[0014] Optionally, the AAO biological treatment tank includes an anaerobic zone, an anoxic zone, and an aerobic zone, which are connected sequentially by pipelines.

[0015] By adopting the above technical solutions and combining anaerobic, anoxic, and aerobic treatment, not only can biodegradable organic matter in wastewater be effectively degraded, but nitrogen and phosphorus removal can also be achieved, comprehensively improving the wastewater treatment effect and meeting the nitrogen and phosphorus requirements of the discharge standards.

[0016] Optionally, the BAF filter is an aerated biological filter, including a filter media layer and a bottom aeration device. The filter media layer includes ceramsite filter media with a biofilm attached to its surface. The bottom aeration device includes an aeration pipe group and air distribution branch pipes. The aeration pipe group is connected to an external air source, and the air distribution branch pipes are distributed below the filter media layer.

[0017] By adopting the above technical solution, the aerated biological filter combines the dual functions of biological treatment and filtration. The biofilm on the surface of the ceramsite filter media can degrade residual trace organic matter, while the filter media layer can filter and remove suspended solids in the wastewater, further ensuring the quality of the effluent and making the various indicators of the effluent consistently meet the standards.

[0018] Optionally, the regulating tank is provided with a stirring device and an overflow port; the stirring device includes a drive motor, a transmission shaft and a stirring paddle, the drive motor is located at the top of the regulating tank, the transmission shaft extends downward into the tank, and the stirring paddle is located at the end of the transmission shaft; the overflow port is located on the upper part of the side wall of the regulating tank.

[0019] By adopting the above technical solution, the stirring device can mix the wastewater entering the equalization tank, equalize the quality and quantity of the wastewater, avoid large fluctuations in the quality of the influent from impacting the subsequent treatment units, and the overflow outlet can cope with sudden water overload situations to ensure the safe operation of the system.

[0020] Optionally, the secondary sedimentation tank includes a central cylinder and a sludge scraper; the central cylinder is located in the central area of ​​the secondary sedimentation tank and is used to evenly distribute the mud-water mixture into the tank for sedimentation and separation; the sludge scraper is located at the bottom of the secondary sedimentation tank and is used to collect the settled sludge into the sludge hopper and discharge it.

[0021] By adopting the above technical solution, the central cylinder can evenly distribute the biochemically treated mud-water mixture, ensuring the uniformity of sedimentation and improving the mud-water separation effect. The sludge scraper can promptly discharge the settled sludge, preventing sludge from accumulating at the bottom of the tank and affecting the sedimentation effect.

[0022] Optionally, the ozone dosage in the Stage I ozone catalytic oxidation tank is 20-30 mg / L, and the ozone dosage in the Stage II ozone catalytic oxidation tank is 30-50 mg / L.

[0023] By adopting the above technical solution, the ozone dosage is adjusted in stages according to the concentration of pollutants in wastewater at different stages. The first-stage ozone is used for high-concentration pre-treated wastewater, and a moderate dosage is used to break down organic matter. The second-stage ozone is used for low-concentration biological effluent, and a higher dosage is used to achieve deep oxidation. This not only ensures the treatment effect but also avoids ozone waste and optimizes operating costs.

[0024] In summary, this application includes at least one of the following beneficial technical effects: 1. Cascaded purification for excellent treatment results: This application adopts a cascaded treatment process of "pretreatment - primary ozone oxidation - biochemical treatment - secondary ozone oxidation - deep filtration". Addressing the complex composition of dyeing and printing wastewater, it degrades pollutants in stages. Primary ozone oxidation first breaks down the molecular structure of recalcitrant organic matter, increasing the B / C ratio of the wastewater from 0.18 to 0.35, significantly improving its biodegradability and creating favorable conditions for biochemical treatment. Secondary ozone oxidation then deeply purifies the biochemical effluent, thoroughly removing residual COD and color. Actual operation data shows that the final effluent COD can be stably reduced to below 50 mg / L, and the color removal rate can reach over 95%, meeting the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002), and under some operating conditions, it can even meet the reuse water standard. 2. High ozone utilization rate and low operating cost: Through the staged addition of ozone in two stages, combined with the catalytic oxidation structure design, the mass transfer efficiency and reaction efficiency of ozone are greatly improved. The overall ozone utilization rate can be increased to more than 90%. Compared with the traditional single-stage ozone process, the ozone dosage is reduced by more than 20%, and the operating cost is reduced by about 30%. At the same time, it avoids the large amount of chemical sludge generated by the Fenton process, reduces secondary pollution, and lowers the cost of sludge disposal. 3. Strong resistance to shock loads and stable operation: This process has good buffering capacity. When the influent water quality fluctuates, such as when the influent COD is as high as 228 mg / L, the COD of the final effluent can still be stably controlled below 50 mg / L after the synergistic treatment of this process. It will not cause the effluent to exceed the standard due to the sudden deterioration of the influent water quality, thus ensuring the long-term stable operation of the treatment system and making it suitable for the characteristics of large fluctuations in the wastewater quality of industrial parks. 4. Strong process adaptability and easy to upgrade: This process can be adapted to dyeing and printing wastewater of different water qualities. For complex wastewater mixed by different enterprises, the effective treatment of wastewater with different loads can be achieved by adjusting the dosage of two-stage ozone and the dosage of pretreatment agents. It has strong adaptability and does not require large-scale modification of the main structure of the existing sewage treatment plant. Upgrading can be completed by simply adding two ozone treatment units. The modification cost is low and it is easy to promote and apply. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process flow structure of this application.

[0026] Figure reference numerals: 1. Equalization tank; 11. Stirring device; 2. Multi-effect separation tank; 21. Coagulation zone; 22. Sedimentation zone; 3. Stage I ozone catalytic oxidation tank; 31. Water jet injector; 4. AAO biological treatment tank; 41. Anaerobic zone; 42. Anoxic zone; 43. Aerobic zone; 5. Secondary sedimentation tank; 51. Central cylinder; 52. Sludge scraper; 6. Stage II ozone catalytic oxidation tank; 61. Front aeration zone; 62. Rear adsorption zone; 63. Separating component; 7. BAF filter; 71. Filter media layer; 72. Bottom aeration device. Detailed Implementation

[0027] The following is in conjunction with the appendix Figure 1 This application will be described in further detail.

[0028] This application discloses a two-stage ozone treatment process for dyeing and printing wastewater. Example 1

[0029] Reference Figure 1 The two-stage ozone treatment process for dyeing and printing wastewater in this embodiment has the following specific treatment flow: 1. Treatment in equalization tank 1: The dyeing and printing wastewater first enters the equalization tank 1. The stirring device 11 in the equalization tank 1 stirs and mixes the wastewater, equalizes the water quality and quantity, and avoids the impact of fluctuations in the influent water quality on the subsequent treatment units. The hydraulic retention time of the equalization tank 1 is 8 hours, and the fluctuations in the water quality of the treated wastewater are effectively buffered.

[0030] 2. Treatment in Multi-Effect Separator 2: The effluent from the equalization tank 1 enters the multi-effect separator 2. The wastewater first enters the coagulation zone 21, where polyferric sulfate (1600 mg / L) and polyacrylamide (4 mg / L) are added. By stirring, the agents are fully mixed with the wastewater, and the colloidal suspended solids and some organic pollutants in the wastewater undergo a coagulation reaction to form flocs. Subsequently, the wastewater enters the sedimentation zone 22 through the water passages in the partition wall. The flocs undergo gravity sedimentation in the sedimentation zone 22, achieving solid-liquid separation. This unit achieves a COD removal rate of 32.6%, effectively reducing the load on subsequent treatment units, while removing suspended solids in the wastewater and preventing suspended solids from covering and passivating the subsequent ozone catalyst.

[0031] 3. Stage I Ozone Catalytic Oxidation Tank 3 Treatment: The wastewater after coagulation and sedimentation enters the Stage I ozone catalytic oxidation tank 3. The water jet 31 in the tank uses the pressure of the inlet water to draw ozone gas into the mixing chamber, achieving efficient gas-liquid mixing. The ozone dosage is 25 mg / L. At the same time, 20 mg / L of hydrogen peroxide is added to the tank as a catalyst to catalyze the decomposition of ozone to generate hydroxyl radicals, which oxidize and break down the recalcitrant organic matter in the wastewater, decomposing large-molecule dye molecules, PVA slurry, etc. into small-molecule organic matter. After treatment in this unit, the B / C ratio of the wastewater increases from 0.18 to 0.35, and the biodegradability is greatly improved, providing favorable conditions for subsequent biological treatment.

[0032] 4. AAO Biological Treatment Tank 4: Wastewater after primary oxidation enters AAO biological treatment tank 4, passing sequentially through anaerobic zone 41, anoxic zone 42, and aerobic zone 43. The anaerobic zone 41 has a residence time of 2 hours for anaerobic phosphorus release and hydrolysis acidification; the anoxic zone 42 has a residence time of 3 hours for denitrification; and the aerobic zone 43 has a residence time of 8 hours, where aerobic microorganisms fully degrade small-molecule organic matter in the wastewater and simultaneously complete the nitrification reaction. This unit achieves a COD removal rate of over 60%, effectively removing most of the biodegradable organic matter.

[0033] 5. Secondary sedimentation tank 5 treatment: The sludge-water mixture after biological treatment enters the secondary sedimentation tank 5. The central cylinder 51 evenly distributes the mixture into the tank. The sludge settles and separates under gravity. The supernatant enters the subsequent treatment unit. Part of the settled sludge is returned to the AAO biological treatment tank 4, and the remaining sludge is discharged for treatment. This unit achieves effective separation of sludge and water, ensuring the suspended solids index of the effluent.

[0034] 6. Stage II Ozone Catalytic Oxidation Tank 6 Treatment: The effluent from the secondary sedimentation tank 5 enters the Stage II ozone catalytic oxidation tank 6. The wastewater first enters the front-end aeration zone 61, where microporous aeration discs disperse ozone gas into tiny bubbles, which undergo preliminary mixing and reaction with the wastewater. The ozone dosage is 40 mg / L, removing most of the easily oxidizable residual pollutants. Subsequently, the wastewater enters the rear-end adsorption zone 62 through the through holes at the bottom of the baffle. The granular activated carbon packing in the adsorption zone adsorbs and enriches the residual recalcitrant pollutants. At the same time, the packing catalyzes the decomposition of ozone, generating hydroxyl radicals, which deeply oxidize the adsorbed pollutants. This unit achieves a COD removal rate of 28.8% and also achieves highly efficient decolorization, with a color removal rate of over 95%.

[0035] 7. BAF Filter Treatment: Wastewater after secondary oxidation enters the BAF aerated biological filter. The biofilm attached to the surface of the ceramic filter media in the filter further degrades the trace organic matter remaining in the wastewater. At the same time, the filtration effect of the filter media removes suspended solids from the wastewater. The final effluent indicators are: CODcr average 48mg / L, color less than 10 times, SS less than 10mg / L, stably meeting the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002).

[0036] The working principle of this application embodiment is as follows: Through a two-stage ozone catalytic oxidation process, combined with intermediate biochemical treatment, step-by-step purification of dyeing and printing wastewater is achieved. The first-stage ozone breaks down recalcitrant organic matter, improving biodegradability and allowing the biochemical treatment to play its full role. The second-stage ozone deeply oxidizes residual pollutants that cannot be treated by biochemical methods, ensuring that the effluent meets standards. At the same time, the optimized tank structure improves the utilization rate of ozone, reduces operating costs, and has good shock resistance. Even when the influent COD is as high as 228 mg / L, the final effluent can still reach 48 mg / L, meeting the discharge standards. Example 2

[0037] The difference between Example 2 and Example 1 is that, in order to meet the requirements of reclaimed water with higher emission standards, the BAF filter 7 has been optimized. The ceramic filter media in the BAF filter 7 is modified ceramic, and a trace amount of iron-based catalytic components are loaded on the surface of the ceramic. This allows the filter to catalytically decompose residual ozone while carrying out biological treatment, further improving the degradation effect of residual organic matter, and avoiding the problem of residual ozone in the effluent.

[0038] In this Example 2, the COD of the final effluent can be stably reduced to below 50 mg / L, and the color can be reduced to below 5 times, meeting the standard of "Water Quality for Reclaimed Water in Textile Dyeing and Finishing Industry" (FZ / T01107-2011). The treated effluent can be reused in the production process of dyeing and printing enterprises, realizing the resource-based reuse of wastewater and further improving the utilization rate of water resources.

[0039] The working principle of this application embodiment is as follows: By combining biological treatment with catalytic oxidation through modified ceramic filter media, the effect of deep treatment is further enhanced, enabling the effluent to meet the requirements for reuse, realizing the recycling of wastewater, and reducing the water costs for enterprises.

[0040] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A two-stage ozone treatment process for dyeing and printing wastewater, comprising a regulating tank (1), a multi-effect separation tank (2), a primary ozone catalytic oxidation tank (3), an AAO biochemical tank (4), a secondary sedimentation tank (5), a secondary ozone catalytic oxidation tank (6), and a BAF filter (7) connected sequentially by pipelines, characterized in that: The dyeing and printing wastewater passes through the equalization tank (1), multi-effect separation tank (2), primary ozone catalytic oxidation tank (3), AAO biochemical tank (4), secondary sedimentation tank (5), primary ozone catalytic oxidation tank (6) and BAF filter (7) in sequence via pipeline.

2. The two-stage ozone treatment process for dyeing and printing wastewater according to claim 1, characterized in that: The Class II ozone catalytic oxidation tank (6) is divided into a front aeration zone (61) and a rear adsorption zone (62) by a partition component (63). The partition component (63) is provided with a fluid communication channel. The rear adsorption zone (62) is filled with porous catalytic adsorption packing, and a gas phase distribution device is provided at the bottom of the porous catalytic adsorption packing.

3. The two-stage ozone treatment process for dyeing and printing wastewater according to claim 1, characterized in that: The separating component (63) is a partition plate, and the fluid communication channel is a through hole opened on the partition plate; the porous catalytic adsorption packing is granular activated carbon, and the gas phase distribution device is a microporous aeration disc.

4. The two-stage ozone treatment process for dyeing and printing wastewater according to claim 1, characterized in that: The Class I ozone catalytic oxidation tank (3) is equipped with a water jet injector (31), which includes a water inlet, an air intake, and a mixing chamber. The air intake is connected to the gas source delivery pipeline.

5. The two-stage ozone treatment process for dyeing and printing wastewater according to claim 1, characterized in that: The multi-effect separation tank (2) includes a coagulation zone (21) and a sedimentation zone (22), which are separated by a partition wall with water passage holes.

6. The two-stage ozone treatment process for dyeing and printing wastewater according to claim 1, characterized in that: The AAO biochemical tank (4) includes an anaerobic zone (41), an anoxic zone (42) and an aerobic zone (43), which are connected in sequence by pipelines.

7. The two-stage ozone treatment process for dyeing and printing wastewater according to claim 1, characterized in that: The BAF filter (7) is an aerated biological filter, including a filter media layer (71) and a bottom aeration device (72). The filter media layer (71) includes ceramsite filter media, and a biofilm is attached to the surface of the ceramsite filter media. The bottom aeration device (72) includes an aeration pipe group and an air distribution branch pipe. The aeration pipe group is connected to an external air source, and the air distribution branch pipe is distributed below the filter media layer (71).

8. The two-stage ozone treatment process for dyeing and printing wastewater according to claim 1, characterized in that: The regulating tank (1) is provided with a stirring device (11) and an overflow port; the stirring device (11) includes a drive motor, a transmission shaft and a stirring paddle, the drive motor is located at the top of the regulating tank (1), the transmission shaft extends downward into the tank, and the stirring paddle is located at the end of the transmission shaft; the overflow port is located on the upper part of the side wall of the regulating tank (1).

9. The two-stage ozone treatment process for dyeing and printing wastewater according to claim 1, characterized in that: The secondary sedimentation tank (5) includes a central cylinder (51) and a sludge scraper (52); the central cylinder (51) is located in the central area of ​​the secondary sedimentation tank (5) and is used to evenly distribute the mud-water mixture into the tank for sedimentation and separation; the sludge scraper (52) is located at the bottom of the secondary sedimentation tank (5) and is used to collect the settled sludge into the sludge hopper and discharge it.

10. The two-stage ozone treatment process for dyeing and printing wastewater according to claim 1, characterized in that: The ozone dosage in the first-stage ozone catalytic oxidation tank (3) is 20~30 mg / L, and the ozone dosage in the second-stage ozone catalytic oxidation tank (6) is 30~50 mg / L.

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