Process for treating printing and dyeing wastewater through membrane

Abstract

The invention relates to the technical field of sewage treatment, in particular to a process for membrane treatment of printing and dyeing wastewater. Printing and dyeing wastewater is sequentially treated by an adjusting tank, an air floatation tank, a deep well aeration tank, a degassing tank and a primary sedimentation tank, activated sludge at the bottom of the primary sedimentation tank flows back to the deep well aeration tank, water at the upper part automatically flows into an MBR membrane tank, and COD (Chemical Oxygen Demand) and ammonia nitrogen in the wastewater are removed; effluent of the MBR membrane tank enters an RO system to be separated, purified and concentrated, pure water and concentrated water are generated, most pollutants in the pure water are removed, the pure water can be directly recycled in a workshop, the concentrated water enters a Fenton reaction tank, and most COD and chroma in wastewater are removed; effluent of the Fenton reaction tank enters a flocculation sedimentation tank for flocculation sedimentation and then enters a discharge tank to be discharged to a nearby sewage plant. According to the invention, the high-concentration printing and dyeing wastewater can be discharged after reaching the standard after being treated, and most treated water can be recycled, so that the technical problems that the existing printing and dyeing wastewater treatment process is large in occupied area and poor in chroma removal effect and the treated water cannot be recycled can be effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a membrane treatment process for printing and dyeing wastewater. Background Art

[0002] With the continuous improvement of people's living standards, the types of printing and dyeing products are growing, and the treatment of printing and dyeing wastewater has gradually attracted attention. Printing and dyeing wastewater contains complex pollutants such as dyes, slurries, additives, oils, acid and alkali substances, fiber impurities, sand substances, inorganic salts, etc. Among them, the concentration of pollutants such as chromaticity, COD, ammonia nitrogen, and total nitrogen is high, the B / C ratio is very low, and most of the pollutants are difficult to biodegrade, which makes it difficult to treat.

[0003] At present, the treatment methods of printing and dyeing wastewater at home and abroad can be divided into physical treatment, chemical treatment, biological treatment and electrolytic treatment according to the principle. In order to improve the treatment effect of wastewater, a long process combining multiple methods is usually adopted. The current common treatment process of printing and dyeing wastewater mainly adopts the steps of regulating tank-coagulation sedimentation-anoxic tank-aerobic tank-secondary sedimentation tank for treatment and purification. This treatment process occupies a large area, has poor effect on color removal, and the treated and purified water cannot be reused, which makes it difficult to meet the increasingly stringent emission standards. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a membrane treatment process for printing and dyeing wastewater, which can make high-concentration printing and dyeing wastewater meet the discharge standards after treatment, and can reuse most of the treated water, which can effectively solve the technical problems of the existing printing and dyeing wastewater treatment process, such as large occupation of area, poor color removal effect and inability to reuse the treated water.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: A technical solution of the present invention provides a membrane treatment process for printing and dyeing wastewater, comprising the following steps: (1) Printing and dyeing wastewater is transported to the regulating pool to adjust the water quality and water quantity; (2) The wastewater in the regulating tank is transported to the flotation tank to remove most of the suspended matter and animal and vegetable oils in the wastewater; (3) The wastewater in the flotation tank is transported to the deep well aeration tank for aeration, and the wastewater temperature is reduced by a cooling tower; (4) The wastewater treated in the deep well aeration tank flows by gravity into the degassing tank to reduce the dissolved oxygen in the wastewater and prevent the sludge from flowing back and affecting the anoxic state at the bottom of the deep well aeration tank; (5) The wastewater treated in the degassing tank is transported to the primary sedimentation tank, and the activated sludge at the bottom is returned to the deep well aeration tank; (6) The water in the upper part of the primary sedimentation tank flows into the MBR membrane tank by gravity, removing COD and ammonia nitrogen from the wastewater and playing a filtering role; (7) The effluent from the MBR membrane pool enters the RO system (i.e., reverse osmosis system) for separation, purification, and concentration to produce pure water and concentrated water. Most of the pollutants are removed from the pure water, and the pure water can be directly reused in the workshop. The concentrated water has a high content of pollutants and needs further treatment; (8) The concentrated water output from the RO system enters the Fenton reaction tank to remove most of the COD and chromaticity in the wastewater, and the COD removal rate can reach more than 60%; (9) The effluent from the Fenton reaction tank enters the flocculation sedimentation tank, into which a coagulant is added to precipitate the suspended solids in the wastewater. The effluent from the flocculation sedimentation tank enters the external discharge tank and is finally discharged to a nearby sewage treatment plant.

[0006] In the above scheme of the present invention, a large amount of suspended matter, animal and plant oils and other substances contained in the printing and dyeing wastewater can be removed by setting up an air flotation tank, thereby ensuring the stability of the activated sludge in the deep well aeration tank and improving the treatment effect of the deep well aeration tank; by adding a cooling tower, the impact of high temperature in summer on the activated sludge can be prevented, thereby improving the biochemical stability; the deep well aeration greatly reduces the floor space compared with the traditional anoxic-aerobic process, and the sludge load is also significantly improved compared with the traditional activated sludge method, which can increase the amount of treated water; an MBR membrane tank is set up to increase a primary biochemical treatment, further remove COD and ammonia nitrogen in the wastewater, and can intercept suspended matter in the wastewater, thereby improving the process stability; an RO system is set up, and the treated pure water can be reused, thereby reducing the amount of wastewater discharged and saving water resource costs; a Fenton reaction tank is set up, and an advanced oxidation process is used to remove most of the COD and chromaticity in the wastewater, thereby ensuring that the effluent meets the discharge standards.

[0007] In some possible implementations, in step (2), liquid alkali is added to the flotation tank to adjust the pH of the wastewater to 9.0-10.5; and flocculants are added to the flotation tank to flocculate and settle to reduce the effluent COD.

[0008] Furthermore, the liquid alkali in the flotation tank is liquid sodium hydroxide with a concentration of 30%. The dosage of the liquid alkali is 0.4-0.6 ppm. Preferably, the dosage of the liquid alkali is 0.5 ppm.

[0009] Furthermore, the flocculant added into the flotation tank is polyaluminium chloride (PAC) and / or polyacrylamide (PAM), and the amount of the flocculant is 50-200 ppm; preferably, the amount of the flocculant is 100 ppm.

[0010] Furthermore, the temperature in the flotation tank is relatively high, and the wastewater temperature is reduced to 25-30° C. by the cooling tower before being transported to the deep well aeration tank.

[0011] In some possible implementations, in step (3), the depth of the deep well aeration tank is not less than 200 meters, and aeration is performed by connecting an air compressor, and the aeration residence time is 6 to 10 hours. The lower part of the deep well aeration tank used in the present invention is in anoxic state, and the upper part is in aerobic state. Nitrification and denitrification reactions are carried out simultaneously in the tank. The deep well aeration tank occupies a small area, which is only 1 / 20 of the area occupied by the traditional anoxic + aerobic process, and can remove most of the ammonia nitrogen, total nitrogen and part of the COD in the wastewater.

[0012] In some possible implementations, in step (3), glucose is regularly added to the deep well aeration tank to provide substances required for denitrification reaction and growth of microorganisms.

[0013] Furthermore, in step (3), the amount of glucose added to the deep well aeration tank is 0.5-2 ppm, and preferably, the amount of glucose added is 1 ppm.

[0014] In some possible implementations, in step (5), a scraper is used to collect the activated sludge at the bottom of the primary sedimentation tank, and a sludge return pump is used to return the degassed and precipitated activated sludge to the deep well aeration tank. Sludge return can increase the sludge concentration in the deep well aeration tank and improve the treatment effect, while reducing the discharge of excess sludge and reducing the cost of sludge treatment.

[0015] In some possible implementations, the MBR membrane pool in step (6) realizes solid-liquid separation through the membrane equipment provided, and is aerated through the aeration pipe provided, and the aeration pipe is connected to the external blower to provide oxygen for the microorganisms, promote the growth and metabolism of the microorganisms, and effectively degrade the organic matter in the wastewater. The MBR membrane pool combines membrane separation technology and activated sludge method, and utilizes the efficient interception effect of the membrane to effectively intercept nitrifying bacteria. The organisms are completely intercepted in the membrane pool, so that the nitrification reaction is ensured to proceed smoothly, ammonia nitrogen is effectively removed, sludge loss is avoided, sludge age is increased, and a high activated sludge concentration in the membrane pool is maintained.

[0016] In some possible implementations, in step (7), a bactericide is added to the RO system to reduce the bacterial content in the wastewater; a reductant is added to the RO system to reduce the ORP value (i.e., the oxidation-reduction potential value) of the wastewater to below 200 mv; and a scale inhibitor is added to the RO system to prevent calcium and magnesium substances from scaling on the RO membrane.

[0017] Furthermore, in step (7), the concentration of the bactericide is 1-10 ppm, the concentration of the reducing agent is 1-5 ppm, and the concentration of the antiscalant is 1-10 ppm. Preferably, the concentration of the bactericide is 3 ppm, the concentration of the reducing agent is 2 ppm, and the concentration of the antiscalant is 3 ppm.

[0018] The RO system (reverse osmosis system) of the present invention is based on the selective filtration function of the reverse osmosis membrane, so that most of the impurities in the wastewater are trapped on one side of the reverse osmosis membrane to form concentrated water, while the other side produces high-purity pure water, achieving the purpose of separation, purification and concentration. Most of the pollutants are removed from the pure water, which can be directly reused in the workshop. The concentrated water has a high content of pollutants and needs to be transported to the Fenton reaction tank for further purification.

[0019] In some possible implementations, sulfuric acid is added to the reaction zone of the Fenton reaction tank in step (8) to control the pH value to 3.5-4.0; ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction, and liquid alkali is added to the effluent of the Fenton reaction tank to control the pH value to 7.5-8.

[0020] Furthermore, in step (8), the sulfuric acid concentration is 98%, and the dosage is 100 ppm; the liquid alkali is liquid sodium hydroxide or liquid calcium hydroxide, and the concentration is 30%, and the dosage is 60 ppm.

[0021] In some possible implementations, the dosage of ferrous sulfate in step (8) is 300 ppm, the dosage of hydrogen peroxide is 120 ppm, the dosage of hydrogen peroxide is positively correlated with the COD content, the Fenton reaction temperature is controlled at 25-45° C., and the wastewater stays in the Fenton reaction tank for 2-3 hours.

[0022] The Fenton reaction in the Fenton reaction tank of the present invention can effectively decompose pollutants such as chromophores in printing and dyeing wastewater and convert them into harmless inorganic substances, thereby achieving the purpose of decolorizing printing and dyeing wastewater and removing COD in wastewater. The reaction temperature is controlled at 25-45°C to activate hydroxyl radicals. Too high a temperature will decompose hydrogen peroxide into water and oxygen.

[0023] In some possible implementations, the coagulant in step (9) is polyacrylamide (PAM) and / or polyferric sulfate (PFS), and the amount of the coagulant is 50-150 ppm; preferably, the amount of the coagulant is 100 ppm.

[0024] The present invention has the following beneficial effects: The membrane treatment process for printing and dyeing wastewater provided by the present invention can save equipment floor space, can effectively remove pollutants such as ammonia nitrogen, chroma, COD, etc. in wastewater, and can reuse most of the treated water, and the various indicators of concentrated water after treatment can also meet the direct discharge standard. The pure water treated by the RO system of the present invention can control the COD value to below 20 mg / L, the ammonia nitrogen content to below 1.5 mg / L, and the chroma to 1, which can fully meet the reuse water standard; after the concentrated water treated by the RO system is further treated in the Fenton reaction tank, the effluent COD value is controlled to below 100 mg / L, the ammonia nitrogen content is controlled to below 5 mg / L, and the chroma is controlled to below 5, which can meet the direct discharge standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0026] Figure 1 The present invention is a flow chart of the membrane treatment process for printing and dyeing wastewater. DETAILED DESCRIPTION

[0027] The following specific embodiments illustrate the implementation of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, it does not mean that the features of this invention are limited to the implementation.

[0028] To make the purpose, technical scheme and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings. In the following examples, unless otherwise specified, the raw materials used are all common commercial products, and the reagents are analytically pure reagents.

[0029] Example 1 refer to Figure 1 In this embodiment, a membrane treatment process for printing and dyeing wastewater is provided, comprising the following steps: (1) Printing and dyeing wastewater is transported to the regulating tank through pipes to adjust the water quality and quantity.

[0030] (2) The wastewater in the regulating tank is transported to the flotation tank through a lifting pump to remove most of the suspended matter and animal and plant oils in the wastewater to prevent impurities from affecting the subsequent system. A 30% concentration of liquid alkali is added to the conveying pipeline from the regulating tank to the flotation tank. The dosage of liquid alkali is 0.5ppm to adjust the pH of the wastewater to 9. At the same time, PAC and PAM are added to the flotation tank. The dosage of PAC and PAM is 100ppm respectively, to flocculate and settle to reduce the effluent COD.

[0031] (3) The wastewater in the flotation tank is transported to the deep well aeration tank for aeration through a lifting pump, and the wastewater temperature is reduced to 25~30℃ through a cooling tower. The deep well aeration tank is 200 meters deep and is aerated by connecting two air compressors. The aeration retention time is 6 hours. 1ppm of glucose is regularly added to the deep well aeration tank to provide the substances required for microbial denitrification and growth. The lower part of the deep well aeration tank is in anoxic state, and the upper part is in an aerobic state. Nitrification and denitrification reactions occur simultaneously in the tank.

[0032] (4) The wastewater treated in the deep well aeration tank flows by gravity into the degassing tank to reduce the dissolved oxygen in the wastewater and prevent the sludge from flowing back and affecting the anoxic state at the bottom of the deep well aeration tank.

[0033] (5) The wastewater treated in the degassing tank is transported to the primary sedimentation tank. The activated sludge at the bottom of the primary sedimentation tank is collected by a scraper, and the activated sludge that has been degassed and precipitated is returned to the deep well aeration tank by a sludge return pump.

[0034] (6) The water from the upper part of the primary sedimentation tank flows by gravity into the MBR membrane pool. The concentration of activated sludge in the MBR membrane pool is 20g / L. The MBR membrane pool is equipped with an aeration pipe for aeration. The aeration pipe is connected to an external blower to provide oxygen for microorganisms, promote their growth and metabolism, and effectively degrade organic matter in the wastewater. The sewage is separated into solid and liquid through the internal membrane equipment, COD and ammonia nitrogen in the wastewater are removed and filtering is performed.

[0035] (7) The effluent from the MBR membrane pool enters the RO system for separation, purification, and concentration to produce pure water and concentrated water. Most of the pollutants are removed from the pure water, and the pure water can be directly reused in the workshop. The concentrated water has a high content of pollutants and needs further treatment. The RO system adds 3ppm of bactericide to reduce the bacterial content in the wastewater, adds 2ppm of reductant to reduce the ORP value of the wastewater to below 200mv, and adds 3ppm of scale inhibitor to prevent calcium and magnesium substances from scaling on the RO membrane. The bactericide, reductant, and scale inhibitor can all be commercially available membrane cleaning reagents.

[0036] (8) The concentrated water output from the RO system enters the Fenton reaction tank to remove most of the COD and color in the wastewater, and the COD removal rate can reach more than 60%. Among them, sulfuric acid with a concentration of 98% and a dosage of 100ppm is added to the reaction zone of the Fenton reaction tank to control the pH to 4.0; 300ppm ferrous sulfate and 120ppm hydrogen peroxide are added for Fenton reaction, the reaction temperature is controlled at 40℃, and the wastewater stays in the Fenton reaction tank for 2 hours; the effluent of the Fenton reaction tank is added with liquid sodium hydroxide with a concentration of 30% and a dosage of 60ppm to control the pH value to 7.5.

[0037] (9) The effluent from the Fenton reaction tank enters the flocculation sedimentation tank, into which 100 ppm of coagulant PAM is added to precipitate the suspended solids in the wastewater. The effluent from the flocculation sedimentation tank enters the external discharge tank and is finally discharged to a nearby sewage treatment plant.

[0038] Example 2 refer to Figure 1 In this embodiment, a membrane treatment process for printing and dyeing wastewater is provided, comprising the following steps: (1) Printing and dyeing wastewater is transported to the regulating tank through pipes to adjust the water quality and quantity.

[0039] (2) The wastewater in the regulating tank is transported to the flotation tank through a lifting pump to remove most of the suspended matter and animal and plant oils in the wastewater to prevent impurities from affecting the subsequent system. A 30% concentration of liquid alkali is added to the conveying pipeline from the regulating tank to the flotation tank. The dosage of liquid alkali is 0.6ppm to adjust the pH of the wastewater to 10. At the same time, PAC and PAM are added to the flotation tank. The dosage of PAC and PAM is 100ppm respectively, to flocculate and settle to reduce the effluent COD.

[0040] (3) The wastewater in the flotation tank is transported to the deep well aeration tank for aeration through a lifting pump, and the wastewater temperature is reduced to 25~30℃ through a cooling tower. The deep well aeration tank is 200 meters deep and is aerated by connecting two air compressors. The aeration retention time is 8 hours. 1ppm of glucose is regularly added to the deep well aeration tank to provide the substances required for microbial denitrification and growth. The lower part of the deep well aeration tank is in anoxic state, and the upper part is in aerobic state. Nitrification and denitrification reactions occur simultaneously in the tank.

[0041] (4) The wastewater treated in the deep well aeration tank flows by gravity into the degassing tank to reduce the dissolved oxygen in the wastewater and prevent the sludge from flowing back and affecting the anoxic state at the bottom of the deep well aeration tank.

[0042] (5) The wastewater treated in the degassing tank is transported to the primary sedimentation tank. The activated sludge at the bottom of the primary sedimentation tank is collected by a scraper, and the activated sludge that has been degassed and precipitated is returned to the deep well aeration tank by a sludge return pump.

[0043] (6) The water from the upper part of the primary sedimentation tank flows by gravity into the MBR membrane pool. The concentration of activated sludge in the MBR membrane pool is 10g / L. The MBR membrane pool is equipped with an aeration pipe for aeration. The aeration pipe is connected to an external blower to provide oxygen for microorganisms, promote their growth and metabolism, and effectively degrade organic matter in the wastewater. The sewage is separated into solid and liquid through the internal membrane equipment, COD and ammonia nitrogen in the wastewater are removed and a filtering effect is played.

[0044] (7) The effluent from the MBR membrane pool enters the RO system for separation, purification, and concentration to produce pure water and concentrated water. Most of the pollutants are removed from the pure water, and the pure water can be directly reused in the workshop. The concentrated water has a high content of pollutants and needs further treatment. The RO system adds 3ppm of bactericide to reduce the bacterial content in the wastewater, adds 2ppm of reducing agent to reduce the ORP value of the wastewater to below 200mv, and adds 3ppm of scale inhibitor to prevent calcium and magnesium substances from scaling on the RO membrane.

[0045] (8) The concentrated water output from the RO system enters the Fenton reaction tank to remove most of the COD and color in the wastewater, and the COD removal rate can reach more than 60%. Among them, sulfuric acid with a concentration of 98% and a dosage of 100ppm is added to the reaction zone of the Fenton reaction tank to control the pH to 4.0; 300ppm ferrous sulfate and 120ppm hydrogen peroxide are added for Fenton reaction, the reaction temperature is controlled at 40℃, and the wastewater stays in the Fenton reaction tank for 2 hours; the effluent of the Fenton reaction tank is added with liquid alkali calcium hydroxide with a concentration of 30% and a dosage of 60ppm to control the pH value to 8.

[0046] (9) The effluent from the Fenton reaction tank enters the flocculation sedimentation tank, into which 100 ppm of coagulant PAM is added to precipitate the suspended solids in the wastewater. The effluent from the flocculation sedimentation tank enters the external discharge tank and is finally discharged to a nearby sewage treatment plant.

[0047] Example 3 refer to Figure 1 In this embodiment, a membrane treatment process for printing and dyeing wastewater is provided, comprising the following steps: (1) Printing and dyeing wastewater is transported to the regulating tank through pipes to adjust the water quality and quantity.

[0048] (2) The wastewater in the regulating tank is transported to the flotation tank through a lifting pump to remove most of the suspended matter and animal and plant oils in the wastewater to prevent impurities from affecting the subsequent system. A 30% concentration of liquid alkali is added to the conveying pipeline from the regulating tank to the flotation tank. The dosage of liquid alkali is 0.6ppm to adjust the pH of the wastewater to 10. At the same time, PAC and PAM are added to the flotation tank. The dosage of PAC and PAM is 100ppm respectively, to flocculate and settle to reduce the effluent COD.

[0049] (3) The wastewater in the flotation tank is transported to the deep well aeration tank for aeration through a lifting pump, and the wastewater temperature is reduced to 25~30℃ through a cooling tower. The deep well aeration tank is 200 meters deep and is aerated by connecting two air compressors. The aeration retention time is 10 hours. 1ppm of glucose is regularly added to the deep well aeration tank to provide the substances required for microbial denitrification and growth. The lower part of the deep well aeration tank is in anoxic state, and the upper part is in aerobic state. Nitrification and denitrification reactions occur simultaneously in the tank.

[0050] (4) The wastewater treated in the deep well aeration tank flows by gravity into the degassing tank to reduce the dissolved oxygen in the wastewater and prevent the sludge from flowing back and affecting the anoxic state at the bottom of the deep well aeration tank.

[0051] (5) The wastewater treated in the degassing tank is transported to the primary sedimentation tank. The activated sludge at the bottom of the primary sedimentation tank is collected by a scraper, and the activated sludge that has been degassed and precipitated is returned to the deep well aeration tank by a sludge return pump.

[0052] (6) The water in the upper part of the primary sedimentation tank flows by gravity into the MBR membrane pool. The concentration of activated sludge in the MBR membrane pool is 15g / L. The MBR membrane pool is equipped with an aeration pipe for aeration. The aeration pipe is connected to an external blower to provide oxygen for microorganisms, promote their growth and metabolism, and effectively degrade organic matter in the wastewater. The sewage is separated into solid and liquid through the internal membrane equipment, COD and ammonia nitrogen in the wastewater are removed and a filtering effect is played.

[0053] (7) The effluent from the MBR membrane pool enters the RO system for separation, purification, and concentration to produce pure water and concentrated water. Most of the pollutants are removed from the pure water, and the pure water can be directly reused in the workshop. The concentrated water has a high content of pollutants and needs further treatment. The RO system adds 3ppm of bactericide to reduce the bacterial content in the wastewater, adds 2ppm of reducing agent to reduce the ORP value of the wastewater to below 200mv, and adds 3ppm of scale inhibitor to prevent calcium and magnesium substances from scaling on the RO membrane.

[0054] (8) The concentrated water output from the RO system enters the Fenton reaction tank to remove most of the COD and color in the wastewater, and the COD removal rate can reach more than 60%. Among them, sulfuric acid with a concentration of 98% and a dosage of 100ppm is added to the reaction zone of the Fenton reaction tank to control the pH to 4.0; 300ppm ferrous sulfate and 120ppm hydrogen peroxide are added for Fenton reaction, the reaction temperature is controlled at 35℃, and the wastewater stays in the Fenton reaction tank for 2 hours; the effluent of the Fenton reaction tank is added with liquid sodium hydroxide with a concentration of 30% and a dosage of 60ppm to control the pH value to 7.5.

[0055] (9) The effluent from the Fenton reaction tank enters the flocculation sedimentation tank, into which 100 ppm of coagulant PFS is added to precipitate the suspended solids in the wastewater. The effluent from the flocculation sedimentation tank enters the external discharge tank and is finally discharged to a nearby sewage treatment plant.

[0056] The water in the membrane treatment process of Examples 1 to 3 was measured, and the results are shown in Tables 1 and 2 below.

[0057] Table 1 Test data of inlet and outlet water of RO system in Examples 1 to 3

[0058] As can be seen from Table 1 above, the RO system of the present invention has a strong removal effect on COD and chromaticity in wastewater, and the indicators of the generated pure water fully meet the standards for recycled water.

[0059] Table 2 Test data of inlet and outlet water of Fenton reaction pool in Examples 1 to 3

[0060] It can be seen from Table 2 above that the Fenton reaction tank of the present invention has a strong removal ability for COD and chromaticity, can significantly reduce the COD concentration and chromaticity in the wastewater, and ensure that the external drainage indicators are qualified.

[0061] Although the preferred embodiments of the present invention have been disclosed as above, they are not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the contents of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A membrane treatment process for printing and dyeing wastewater, characterized in that: The following steps are involved: (1) Printing and dyeing wastewater is transported to the regulating pool to adjust the water quality and water quantity; (2) The wastewater in the regulating tank is transported to the flotation tank to remove most of the suspended matter and animal and vegetable oils in the wastewater; (3) The wastewater in the flotation tank is transported to the deep well aeration tank for aeration, and the wastewater temperature is reduced by a cooling tower; (4) The wastewater treated in the deep well aeration tank flows by gravity into the degassing tank to reduce the dissolved oxygen in the wastewater; (5) The wastewater treated in the degassing tank is transported to the primary sedimentation tank, and the activated sludge at the bottom is returned to the deep well aeration tank; (6) The water in the upper part of the primary sedimentation tank flows into the MBR membrane tank by gravity to remove COD and ammonia nitrogen from the wastewater; (7) The effluent from the MBR membrane pool enters the RO system for separation, purification, and concentration to produce pure water and concentrated water; (8) The concentrated water output from the RO system enters the Fenton reaction tank to remove most of the COD and color in the wastewater; (9) The effluent from the Fenton reaction tank enters the flocculation sedimentation tank, into which a coagulant is added to precipitate the suspended solids in the wastewater. The effluent from the flocculation sedimentation tank enters the external discharge tank and is finally discharged to a nearby sewage treatment plant.

2. The membrane treatment process for printing and dyeing wastewater according to claim 1, characterized in that: In step (2), liquid alkali is added into the flotation tank to adjust the pH value of the wastewater to 9.0-10.5; and flocculant is added into the flotation tank to flocculate and settle to reduce the effluent COD.

3. The membrane treatment process for printing and dyeing wastewater according to claim 1, characterized in that: In step (3), the deep well aeration tank has a depth of not less than 200 meters, and aeration is performed by connecting two air compressors, and the aeration residence time is 6 to 10 hours.

4. The membrane treatment process for printing and dyeing wastewater according to claim 1, characterized in that: In step (3), glucose is added into the deep well aeration tank to provide substances required for the denitrification reaction and growth of microorganisms.

5. The membrane treatment process for printing and dyeing wastewater according to claim 1, characterized in that: In step (5), a scraper is used to collect the activated sludge at the bottom of the primary sedimentation tank, and a sludge return pump is used to return the activated sludge to the deep well aeration tank.

6. The membrane treatment process for printing and dyeing wastewater according to claim 1, characterized in that: The MBR membrane pool in step (6) realizes solid-liquid separation through the membrane equipment provided, and is aerated through the aeration pipe provided, and the aeration pipe is connected to an external blower.

7. The membrane treatment process for printing and dyeing wastewater according to claim 1, characterized in that: In step (7), a bactericide is added to the RO system to reduce the bacterial content in the wastewater; a reductant is added to the RO system to reduce the ORP value of the wastewater to below 200 mv; and an antiscalant is added to the RO system to prevent scaling of the RO membrane.

8. The membrane treatment process for printing and dyeing wastewater according to claim 1, characterized in that: In step (8), sulfuric acid is added to the reaction zone of the Fenton reaction tank to control the pH to 3.5-4.0; ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction, and liquid alkali is added to the effluent of the Fenton reaction tank to control the pH value to 7.5-8.

9. The membrane treatment process for printing and dyeing wastewater according to claim 8, characterized in that: In step (8), the dosage of ferrous sulfate is 300 ppm, the dosage of hydrogen peroxide is 120 ppm, the dosage of hydrogen peroxide is positively correlated with the COD content, the Fenton reaction temperature is controlled at 25-45°C, and the wastewater stays in the Fenton reaction tank for 2-3 hours.

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