A method for recycling high-salt printing and dyeing wastewater based on a dual-mode system

Abstract

The present invention belongs to the technical field of multi-stage treatment of printing and dyeing wastewater, and mainly relates to a method for recycling high-salt printing and dyeing wastewater based on a dual-mode system. The purpose of the present invention is to solve the problem that it is difficult to efficiently classify and treat high-salt printing and dyeing wastewater in the prior art. The high-salt printing and dyeing wastewater is subjected to preliminary precipitation treatment to obtain wastewater to be recycled; the wastewater to be recycled is subjected to inorganic salt recovery treatment to obtain desalted wastewater and inorganic salt recovery products; after the desalted wastewater is detected by a fiber content detection unit, it is classified and sent to mode A or mode B according to the fiber content to obtain dye-enriched wastewater; the dye-enriched wastewater is subjected to dye recovery treatment and reverse osmosis separation treatment to obtain dye recovery products and reclaimed water. The method for recycling high-salt printing and dyeing wastewater proposed by the present invention can classify and treat different types of printing and dyeing wastewater, effectively improve the operation efficiency of each section, effectively purify the water body, and can fully recycle high-value components such as inorganic salts and dyes in the printing and dyeing wastewater.

Description

Technical Field

[0001] The present invention belongs to the technical field of multi-stage treatment of printing and dyeing wastewater, and mainly relates to a method for recycling high-salt printing and dyeing wastewater based on a dual-mode system. Background Art

[0002] As an important part of the textile industry, the printing and dyeing industry plays an important role in social production. After thousands of years of development, the modern printing and dyeing industry has long entered an automated and intensive production mode. Through complex printing and dyeing processes, various types of textiles can form rich colors and patterns, becoming important necessities in people's lives. The complex processes in the printing and dyeing industry usually include multi-stage chemical treatments, accompanied by a large amount of production water and electricity consumption. During pretreatment, dyeing, printing, etc., a large amount of residual dyes, auxiliaries, inorganic salts, etc. will be discharged together with the production water to form printing and dyeing wastewater. Printing and dyeing wastewater has a large volume, complex water quality, many difficult-to-decompose components, and great harm to the environment. Therefore, the rapid development of the printing and dyeing industry has also put forward new requirements for wastewater treatment processes.

[0003] Existing printing and dyeing wastewater treatment processes usually mainly rely on traditional physical and chemical methods such as coagulation, precipitation, adsorption, etc., supplemented by aerobic biological treatment technologies such as activated sludge method and biofilm method, and can effectively treat specific wastewater. However, the pollutants contained in printing and dyeing wastewater are diverse in types, cumbersome to treat in multi-stage treatment processes, and it is difficult to achieve the classified recovery of valuable components and the harmless treatment of other components. To solve these key problems, the industrial community has conducted a lot of research and exploration in the field of printing and dyeing wastewater treatment in recent years and made certain progress.

[0004] For example, Chinese Patent CN110156249B proposes an integrated method for the pretreatment of high-concentration printing and dyeing wastewater based on tubular membranes. This invention combines a pretreatment unit, a biochemical treatment unit, a deep recycling treatment unit, and a sludge treatment unit. Using the tubular membrane as the core structure of the reactor, it effectively removes the highly polluting and difficult-to-degrade organic matter in the raw water, reduces the COD of the wastewater, and completes the recycling of inorganic salts such as sodium sulfate while significantly reducing the process cost. However, this invention cannot classify the wastewater generated by different production lines and cannot recycle other high-value products. Chinese Patent CN114538576B proposes a printing and dyeing wastewater treatment system and a printing and dyeing wastewater treatment method. This invention designs a capacitive deionization module, which can efficiently remove organic pollutants in printing and dyeing wastewater by using physical electroadsorption and the oxidation effect of electrode materials during the treatment process. This invention has a high removal efficiency for organic pollutants but does not have the function of recycling high-value components in printing and dyeing wastewater. Chinese Patent CN117228906B proposes a printing and dyeing wastewater treatment process, which realizes a higher COD removal rate and zero discharge of wastewater after pretreatment and salt separation and concentration treatment. The treatment process is efficient and simple. The problem with this invention is that the treatment process does not consider the various fiber components unique to printing and dyeing wastewater and cannot efficiently classify different types of printing and dyeing wastewater.

[0005] Currently, it remains a major problem in the industry to efficiently classify high-salt printing and dyeing wastewater.

[0006] Therefore, a method for recycling high-salt printing and dyeing wastewater based on a dual-mode system is proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for recycling high-salt printing and dyeing wastewater based on a dual-mode system. The high-salt printing and dyeing wastewater is subjected to preliminary precipitation treatment to obtain the wastewater to be recycled; the wastewater to be recycled is subjected to inorganic salt recycling treatment to obtain desalted wastewater and inorganic salt recycling products; the desalted wastewater is classified and sent to Mode A or Mode B according to the fiber content after being detected by a fiber content detection unit, and after treatment, dye-enriched wastewater is obtained; the dye-enriched wastewater is subjected to dye recycling treatment and reverse osmosis separation treatment to obtain dye recycling products and reclaimed water. The method for recycling high-salt printing and dyeing wastewater proposed by the present invention can classify different types of printing and dyeing wastewater, effectively improve the operation efficiency of each section, has a high water purification effect, and can fully recycle high-value components such as inorganic salts and dyes in printing and dyeing wastewater.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The high-salt printing and dyeing wastewater is preliminarily precipitated through a primary sedimentation tank, a filtration tank, and a combined sedimentation-flotation treatment unit; among them, the aeration intensity of the primary sedimentation tank is 10:1 - 12:1, and the aeration time is 3 - 4 hours; the filtration tank is a rapid sand filtration tank, and the filtration rate is 15 - 20m 3 / h; the average particle size of quartz sand in the rapid sand filtration tank is 0.8 - 1.2mm; the high-salt printing and dyeing wastewater passing through the filtration tank is introduced into the sedimentation tank, and the pH is adjusted to 6 - 8. The high-salt printing and dyeing wastewater stays in the sedimentation tank for 2 hours to obtain post-sedimentation wastewater; the post-sedimentation wastewater is introduced into the flotation tank, and 200mg / L of ferrous sulfate is added. The post-sedimentation wastewater stays in the flotation tank for 1 hour to obtain pre-flotation wastewater; 3 - 7mg / L of polyacrylamide is added to the pre-flotation wastewater; dissolved air water is introduced into the pre-flotation wastewater, and after 1 hour, the floating scum and sediment are removed to obtain the wastewater to be recycled;

[0010] The wastewater to be recycled is subjected to inorganic salt recovery treatment through an electrodialysis unit, a sodium sulfate mechanical vapor recompression evaporation (MVR, the same below) unit, a high-pressure reverse osmosis unit, and a sodium chloride MVR unit; the wastewater to be recycled is introduced into the electrodialysis unit to obtain a sodium sulfate concentrate and desulfated wastewater; the desulfated wastewater is introduced into the high-pressure reverse osmosis unit to obtain a sodium chloride concentrate and desalted wastewater; the sodium sulfate concentrate is introduced into the sodium sulfate MVR unit to obtain industrial sodium sulfate; the sodium chloride concentrate is introduced into the sodium chloride MVR unit to obtain industrial sodium chloride; among them, the inorganic salt recovery products include: industrial sodium sulfate and industrial sodium chloride;

[0011] The desalted wastewater is introduced into a fiber content detection unit to detect whether the fiber content in the desalted wastewater is higher than the threshold; if the fiber content is lower than the threshold, the desalted wastewater is output as low-fiber-content wastewater for treatment in Mode A to obtain pre-treated wastewater in Mode A; Mode A includes aerobic biological treatment; if the fiber content is higher than the threshold, the desalted wastewater is output as high-fiber-content wastewater for treatment in Mode B to obtain pre-treated wastewater in Mode B; Mode B includes COD chemical treatment and COD biological treatment;

[0012] The pre-treated wastewater in Mode A and the pre-treated wastewater in Mode B pass through a sedimentation and aeration unit to obtain dye-enriched wastewater; the dye-enriched wastewater is subjected to dye recovery treatment to obtain an intermediate product; the intermediate product is subjected to reverse osmosis separation treatment to obtain dye recovery products and reclaimed water.

[0013] Preferably, the fiber content detection unit includes: a feed pipeline, a control valve, an outlet pipeline A, an outlet pipeline B, and a laser particle size analyzer; the fiber content is the total content of chemical fibers and natural fibers; chemical fibers include polyester fibers and nylon fibers; natural fibers include cotton fibers, hemp fibers, and silk fibers; the fiber content threshold is 1000mg / L.

[0014] Preferably, the desalinated wastewater is introduced through a feed pipe, and the fiber particle size and distribution in the desalinated wastewater are tested by a laser particle size analyzer to calculate the fiber content in the desalinated wastewater. If the fiber content is lower than 1000 mg / L, the desalinated wastewater is output as low-fiber wastewater, which is controlled by a control valve and conveyed to the discharge pipe A. If the fiber content is higher than 1000 mg / L, the desalinated wastewater is output as high-fiber wastewater, which is controlled by a control valve and conveyed to the discharge pipe B.

[0015] Preferably, the aerobic biological treatment includes: an activated sludge unit and a biological contact oxidation unit; after the low-fiber wastewater is introduced into the activated sludge unit for treatment for 2 hours, it is introduced into the biological contact oxidation unit for treatment for 1-2 hours to obtain the pre-treated wastewater in Mode A.

[0016] Preferably, the COD chemical treatment includes: an adsorption-coagulation unit and a redox unit; the COD biological treatment includes: an upflow anaerobic sludge unit; after the high-fiber wastewater is introduced into the adsorption-coagulation unit for 2 hours, it is introduced into the redox unit for 3 hours, and then introduced into the upflow anaerobic sludge unit for 1-2 hours to obtain the pre-treated wastewater in Mode B; the adsorbent put into the adsorption-coagulation unit is activated carbon, with an input concentration of 50 mg / L and an adsorption time of 100 min; the coagulant put in is polyaluminum chloride, with an input amount of 50 mg / L and a coagulation time of 30 min; the electrochemical oxidation method is used in the redox unit, with a current density of 80 mA / cm 2 , the electrode used is a graphite electrode, and the electrolysis time is 50 minutes; the hydraulic retention time of the upflow anaerobic sludge unit is 8 hours, the organic loading rate is 5 kg COD / m 3 ·d, the rising flow rate is 1 m / h, and the reaction temperature is 35°C.

[0017] Preferably, the dye recovery treatment includes: an adsorption precipitation separation unit and a coagulation unit; the dye-enriched wastewater is introduced into the adsorption precipitation separation unit for 1-3 hours, and then introduced into the coagulation unit for 1 hour to obtain an intermediate product.

[0018] Preferably, the reverse osmosis separation treatment includes: a reverse osmosis separation unit; the intermediate product is introduced into the reverse osmosis separation unit, and after treatment for 3-5 hours, reclaimed water and a dye recovery product are obtained; the water flux of the reverse osmosis separation unit is 30-50 L / (m 2 ·h), and the temperature is 35-40°C.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. An inorganic salt recovery and treatment process is set at the front end of the high-salt printing and dyeing wastewater recovery process, effectively reducing the concentration of inorganic salts in the wastewater. This not only facilitates subsequent biochemical treatment but also greatly reduces the technical difficulty of recovering other high-value components. At the same time, high-purity industrial sodium chloride and industrial sodium sulfate can be obtained using the MVR process, enabling the present invention to have a high inorganic salt recovery rate.

[0021] 2. A fiber content detection unit is introduced before treating the desalted wastewater to classify different types of printing and dyeing wastewater. This significantly improves the wastewater treatment scope of the recovery system, enabling efficient classification treatment of various wastewaters, effectively solving the problem that the prior art can only treat wastewater from a single production line. At the same time, there is no need to design multiple recovery systems, and the co-line treatment of various wastewaters can be completed within the dual-mode system designed in the present invention.

[0022] 3. For wastewater with a low fiber content, aerobic biological treatment is directly carried out. The process is simple and can achieve a good effect of reducing COD. For wastewater with a high fiber content, redox treatment and upflow anaerobic sludge treatment are carried out, effectively decomposing the high-concentration fibers in the wastewater, reducing COD and the difficulty of subsequent dye recovery treatment.

[0023] 4. Recover azo dyes, anthraquinone dyes, cationic dyes, etc. in the dye-enriched wastewater. While recovering some high-value products, it significantly reduces the COD of the wastewater, solving the problem that the prior art is not comprehensive enough in recovering high-value components in printing and dyeing wastewater.

[0024] 5. Through multi-stage wastewater treatment, high-value components in the wastewater are fully recovered, and difficult-to-recover and low-value pollutants are treated more thoroughly, achieving harmless discharge of the wastewater. The reclaimed water discharged by the recovery process proposed in the present invention meets the Class V water quality standard specified in GB3838 - 2002, achieving green treatment of printing and dyeing wastewater. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the principle of the high-salt printing and dyeing wastewater recovery and utilization method based on a dual-mode system in the present invention.

[0026] Figure 2 It is a process flow diagram of the high-salt printing and dyeing wastewater recovery and utilization method based on a dual-mode system in the present invention.

[0027] Figure 3 It is a structural schematic diagram of the fiber content detection unit in the present invention.

[0028] In the figure: 1. Feed pipeline; 2. Control valve; 21. Discharge pipeline A; 22. Discharge pipeline B; 3. Laser particle size analyzer. Detailed Embodiments

[0029] The technical solutions of the present invention will be clearly and completely described below through some embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0030] Referring to Figure 1 the schematic diagram of the principle shown, the present invention provides a method for recycling high-salt printing and dyeing wastewater based on a dual-mode system, and the technical solutions are as follows:

[0031] The substance information involved in the present invention is as follows:

[0032] Ferrous sulfate: CAS: 7720-78-7; Polyacrylamide: CAS: 9003-05-8; Polyaluminium chloride: CAS: 1327-41-9; Acid Red G: CAS: 3734-67-6; Disperse Blue 2BLN: CAS: 12217-79-7; Brilliant Red 5GN: CAS: 235-399-2; Reactive Brilliant Blue KN-R: CAS: 2580-78-1; Direct Lake Blue 5B: CAS: 2429-74-5; Disperse Yellow RGFL: CAS: 6250-23-3; Disperse Blue 2BLN: CAS: 12217-79-7; Hematoxylin: CAS: 517-28-2; Direct Light Fast Yellow RS: CAS: 25738-24-3; Vat Blue RSN: CAS: 81-77-6.

[0033] Example 1

[0034] Source A of high-salt printing and dyeing wastewater: Nylon fabric printing and dyeing section, with a salt content of 4.25 g / L and a fiber content of 354.2 mg / L.

[0035] Referring to the Figure 2 process flow chart shown, the high-salt printing and dyeing wastewater is preliminarily precipitated through a primary sedimentation tank, a filtration tank, and a combined sedimentation-flotation treatment unit; among them, the aeration intensity of the primary sedimentation tank is 10:1, and the aeration time is 4 hours; the filtration tank is a rapid sand filtration tank, and the filtration speed is 20 m 3 / h; the average particle size of quartz sand in the rapid sand filtration tank is 0.8 mm; the high-salt printing and dyeing wastewater passing through the filtration tank is introduced into the sedimentation tank, and the pH is adjusted to 6. The high-salt printing and dyeing wastewater stays in the sedimentation tank for 2 hours to obtain post-sedimentation wastewater; the post-sedimentation wastewater is introduced into the flotation tank, and 200 mg / L of ferrous sulfate is added. The post-sedimentation wastewater stays in the flotation tank for 1 hour to obtain pre-flotation wastewater; 7 mg / L of polyacrylamide is added to the pre-flotation wastewater and then dissolved air water is introduced. After 1 hour, the floating scum and sediment are removed to obtain the wastewater to be recycled.

[0036] The wastewater to be recycled is subjected to inorganic salt recovery treatment through an electrodialysis unit, a sodium sulfate MVR unit, a high-pressure reverse osmosis unit, and a sodium chloride MVR unit; the wastewater to be recycled is introduced into the electrodialysis unit with a current density of 2.5 mA / cm 2 , an operating voltage of 120 V, and a wastewater flow rate of 3 cm / s to obtain a sodium sulfate concentrate and desulfated wastewater; the desulfated wastewater is introduced into the high-pressure reverse osmosis unit with an operating pressure of 7.5 MPa to obtain a sodium chloride concentrate and desalted wastewater; the sodium sulfate concentrate is introduced into the sodium sulfate MVR unit with an evaporation temperature of 80 °C and an evaporation pressure of 100 kPa, and industrial sodium sulfate is obtained after evaporation; the sodium chloride concentrate is introduced into the sodium chloride MVR unit with an evaporation temperature of 80 °C and an evaporation pressure of 100 kPa, and industrial sodium chloride is obtained after evaporation.

[0037] The desalted wastewater is introduced through the feed pipe 1 in the fiber amount detection unit as shown in Figure 3 . The fiber particle size and distribution in the desalted wastewater are detected by a laser particle size analyzer 3 to determine that the wastewater is low-fiber amount wastewater; the low-fiber amount wastewater is controlled by a control valve 2 and conveyed to the discharge pipe A21 for treatment in mode A.

[0038] The low-fiber amount wastewater is introduced into the activated sludge unit for treatment for 2 hours and then into the biological contact oxidation unit for treatment for 1 hour to obtain pre-treated wastewater in mode A. The pre-treated wastewater in mode A is treated by a sedimentation aeration unit for 1 hour to obtain dye-enriched wastewater. The dye-enriched wastewater is introduced into the adsorption precipitation separation unit for 3 hours and then into the coagulation unit for 1 hour to obtain an intermediate product. The intermediate product is introduced into the reverse osmosis separation unit and treated for 3 hours under the conditions of a water flux of 30 L / (m 2 ·h) and a temperature of 35 °C to obtain reclaimed water and a dye recovery product.

[0039] Comparative Example 1

[0040] Different from Example 1, the inorganic salt recovery treatment process is not carried out, and the high-salt printing and dyeing wastewater is directly sent to the fiber amount detection unit for subsequent treatment after preliminary precipitation treatment, and other process parameters remain unchanged.

[0041] Comparative Example 2

[0042] Different from Example 1, the high-salt printing and dyeing wastewater is directly sent to the fiber amount detection unit for subsequent treatment after preliminary precipitation treatment, the obtained dye-enriched wastewater is subjected to inorganic salt recovery treatment, and the obtained desalted wastewater is subjected to reverse osmosis separation treatment to obtain reclaimed water, and other process parameters remain unchanged.

[0043] Experimental Example 1

[0044] According to GB3838-2002 standard, the reclaimed water obtained from Example 1 and Comparative Example 1 and Comparative Example 2 was tested, and the test data were pH value, dissolved oxygen, permanganate index, COD and the contents of sulfate, chloride, nitrate, iron and manganese. The relevant results are summarized in Table 1.

[0045] Table 1 Effects of different treatment processes on reclaimed water quality

[0046]

[0047] As shown in the water quality data of Table 1, when the inorganic salt recovery and treatment section is missing or placed after other treatments, the quality of the resulting reclaimed water will deteriorate significantly. Example 1 Because the main inorganic salts are separated and recovered in the front section of the recovery process, the water treatment process in the subsequent section is not easily affected by high concentrations of inorganic salts, and the overall process has a good effect on wastewater treatment. The resulting reclaimed water meets the Class V water quality standard specified in GB3838-2002, and can achieve harmless discharge of wastewater. For Comparative Example 1, the lack of an inorganic salt recovery and treatment section not only makes the sulfate and chloride content of the reclaimed water produced by its process far higher than the normal standard, but also causes other sections to have poor treatment effects on wastewater, resulting in overall water quality deterioration. For Comparative Example 2, the post-placed inorganic salt recovery and treatment section can greatly reduce the content of sulfate and chloride in the reclaimed water, but the effect is worse than that of Example 1, and the impact of high concentrations of inorganic salts on other sections is still very serious, causing the quality of the reclaimed water to fail to meet the discharge standards. High concentrations of inorganic salts have significant negative effects on biological treatment units and membrane treatment units in multi-stage wastewater treatment processes. The high osmotic pressure of the living environment caused by high salt content will lead to reduced microbial activity in activated sludge tanks and other sections. Pre-removal of inorganic salts can maintain the osmotic pressure balance of the microbial living environment, which is beneficial to improving the removal efficiency of organic pollutants in the biological treatment stage. At the same time, high concentrations of inorganic salts can cause membrane pollution, reduce membrane flux and separation efficiency, and pre-removal of inorganic salts can help improve the efficiency of membrane separation methods such as reverse osmosis.

[0048] Example 2

[0049] Source A of high-salt printing and dyeing wastewater: nylon fabric printing and dyeing section, with a salt content of 4.25 g / L and a fiber content of 354.2 mg / L.

[0050] References Figure 2 The process flow chart shown in the figure is to treat the high-salt printing and dyeing wastewater through the primary sedimentation tank, the filtration tank and the sedimentation-flotation combined treatment unit for preliminary sedimentation treatment; the aeration intensity of the primary sedimentation tank is 12:1, and the aeration time is 3 hours; the filtration tank is a fast sand filter tank with a filtration speed of 17m / s. 3 / h; the average particle size of quartz sand in the rapid sand filter is 1.2 mm; the high-salt printing and dyeing wastewater passing through the filter tank is introduced into the sedimentation tank, and the pH is adjusted to 8. The high-salt printing and dyeing wastewater stays in the sedimentation tank for 2 hours to obtain the post-sedimentation wastewater; the post-sedimentation wastewater is introduced into the air flotation tank, and 200 mg / L of ferrous sulfate is added. The post-sedimentation wastewater stays in the air flotation tank for 1 hour to obtain the pre-air flotation wastewater; 3 mg / L of polyacrylamide is added to the pre-air flotation wastewater and then dissolved air water is introduced. After 1 hour, the floating scum and sediment are removed to obtain the wastewater to be recycled.

[0051] The wastewater to be recycled is subjected to inorganic salt recovery treatment through an electrodialysis unit, a sodium sulfate MVR unit, a high-pressure reverse osmosis unit, and a sodium chloride MVR unit; the wastewater to be recycled is introduced into the electrodialysis unit, the current density is 2.5 mA / cm 2 , the operating voltage is 120 V, and the wastewater flow rate is 3 cm / s to obtain a sodium sulfate concentrate and desulfated wastewater; the desulfated wastewater is introduced into the high-pressure reverse osmosis unit, and the operating pressure is 7.5 MPa to obtain a sodium chloride concentrate and desalted wastewater; the sodium sulfate concentrate is introduced into the sodium sulfate MVR unit, the evaporation temperature is 80 °C, and the evaporation pressure is 100 kPa. After evaporation is completed, industrial sodium sulfate is obtained; the sodium chloride concentrate is introduced into the sodium chloride MVR unit, the evaporation temperature is 80 °C, and the evaporation pressure is 100 kPa. After evaporation is completed, industrial sodium chloride is obtained.

[0052] The desalted wastewater is introduced through the feed pipe 1 in the fiber quantity detection unit as shown in Figure 3 . The fiber particle size and distribution in the desalted wastewater are detected by a laser particle size analyzer 3 to determine that the wastewater is low-fiber-content wastewater; the low-fiber-content wastewater is controlled by a control valve 2 and conveyed to the discharge pipe A21 and sent to be treated in mode A.

[0053] The low-fiber-content wastewater is introduced into the activated sludge unit for treatment for 2 hours and then into the biological contact oxidation unit for treatment for 1 hour to obtain the pre-treated wastewater in mode A. The pre-treated wastewater in mode A is treated in the sedimentation and aeration unit for 1 hour to obtain dye-enriched wastewater. The dye-enriched wastewater is introduced into the adsorption and precipitation separation unit for 1 hour and then into the coagulation unit for 1 hour to obtain an intermediate product. The intermediate product is introduced into the reverse osmosis separation unit and treated for 5 hours under the conditions of a water flux of 50 L / (m 2 ·h) and a temperature of 40 °C to obtain reclaimed water and a dye recovery product.

[0054] Example 3

[0055] Differing from Example 2, different sources of high-salt printing and dyeing wastewater are used, and the other process parameters are the same except for mode switching.

[0056] High-salt printing and dyeing wastewater source B: Acrylic-cotton blended fabric printing and dyeing section, with a salt content of 6.88 g / L and a fiber content of 1534.7 mg / L.

[0057] The desalted wastewater is introduced through the feed pipe 1 in the fiber amount detection unit as shown in Figure 3 . The fiber diameter and distribution in the desalted wastewater are detected by a laser particle size analyzer 3 to determine that the wastewater is high-fiber-content wastewater. The high-fiber-content wastewater is controlled by a control valve 2 and transported to the discharge pipe B22 for treatment in mode B.

[0058] After the high-fiber-content wastewater is introduced into the adsorption-coagulation unit for 2 hours, it is introduced into the redox unit for 3 hours, and then into the upflow anaerobic sludge unit for 1 hour to obtain the pretreated wastewater in mode B; among them, the adsorbent input in the adsorption-coagulation unit is activated carbon, with an input concentration of 50 mg / L and an adsorption time of 100 min; the coagulant input is polyaluminum chloride, with an input amount of 50 mg / L and a coagulation time of 30 min; the redox unit uses the electro-chemical oxidation method, with a current density of 80 mA / cm 2 , the electrode used is a graphite electrode, and the electrolysis time is 50 minutes; the hydraulic retention time of the upflow anaerobic sludge unit is 8 hours, the organic loading rate is 5 kg COD / m 3 ·d, the upward flow rate is 1 m / h, and the reaction temperature is 35 °C.

[0059] Comparative Example 3

[0060] Different from Example 2, the fiber amount detection unit is removed, and the wastewater in high-salt printing and dyeing wastewater source B is treated with the same process, and other process parameters are the same.

[0061] Comparative Example 4

[0062] Different from Example 3, the fiber amount detection unit is removed, and the wastewater in high-salt printing and dyeing wastewater source A is treated with the same process, and other process parameters are the same.

[0063] Experimental Example 2

[0064] According to the GB3838-2002 standard, the reclaimed water obtained from Examples 2-3 and Comparative Examples 3-4 is detected, and the pH value, dissolved oxygen, permanganate index, and COD are tested. The time required to treat 15 m 3 of wastewater in each process is counted, and the obtained results are summarized in Table 2.

[0065] Table 2 Improvement of the wastewater treatment efficiency by the dual-mode system

[0066]

[0067] As can be seen from Table 2, Mode A can effectively complete the recovery and purification of wastewater with a low fiber content and takes less time, while Mode B can effectively complete the recovery and purification of wastewater with both low and high fiber contents but takes a longer time. Mode B has a higher treatment effect compared to Mode A, but the process is longer and takes more time. Therefore, it is of great significance to set up a fiber content detection unit to classify and treat wastewater. In the presence of the fiber content detection unit, both Example 2 and Example 3 can automatically select the appropriate treatment mode according to the type of wastewater and can achieve harmless discharge of the wastewater. If the fiber content detection unit is not used and a single Mode A or Mode B is used as a process section in the multi-stage wastewater treatment process, problems such as poor treatment effect of high-fiber wastewater in Comparative Example 3 or excessive treatment time of low-fiber wastewater in Comparative Example 4 will occur. The fiber content detection unit and the dual-mode treatment system can effectively solve the problem of parallel treatment of various wastewaters. Treating low-fiber wastewater with Mode A has a simple process and good effects; treating high-fiber wastewater with Mode B can effectively decompose the high-concentration fibers in the wastewater and also achieve good wastewater treatment effects. Therefore, the design of the fiber content detection unit and the dual-mode design of Mode A and Mode B in the present invention effectively achieve a balance between treatment effect and treatment cost and have significant application value.

[0068] Example 4

[0069] Source A of high-salt printing and dyeing wastewater: Nylon fabric printing and dyeing section, with a salt content of 4.25 g / L, a fiber content of 354.2 mg / L, and the main components of the dye being Acid Red G and Disperse Blue 2BLN.

[0070] Refer to the process flow chart as Figure 2 shown. The high-salt printing and dyeing wastewater is subjected to preliminary sedimentation treatment through a primary sedimentation tank, a filtration tank, and a combined sedimentation-flotation treatment unit. Among them, the aeration intensity of the primary sedimentation tank is 11:1, and the aeration time is 4 hours; the filtration tank is a rapid sand filter, and the filtration rate is 15 m 3 / h; the average particle size of quartz sand in the rapid sand filter is 0.8 mm; the high-salt printing and dyeing wastewater passing through the filtration tank is introduced into the sedimentation tank, and the pH is adjusted to 7. The high-salt printing and dyeing wastewater stays in the sedimentation tank for 2 hours to obtain post-sedimentation wastewater; the post-sedimentation wastewater is introduced into the flotation tank, and 200 mg / L of ferrous sulfate is added. The post-sedimentation wastewater stays in the flotation tank for 1 hour to obtain pre-flotation wastewater; 5 mg / L of polyacrylamide is added to the pre-flotation wastewater and then introduced into the dissolved air water. After 1 hour, the floating scum and sediment are removed to obtain the wastewater to be recycled.

[0071] The wastewater to be recycled is subjected to inorganic salt recovery treatment through an electrodialysis unit, a sodium sulfate MVR unit, a high-pressure reverse osmosis unit, and a sodium chloride MVR unit. The wastewater to be recycled is introduced into the electrodialysis unit, and the current density is 2.5 mA / cm 2, the operating voltage is 120 V, the wastewater flow rate is 3 cm / s, and concentrated sodium sulfate solution and desulfated sodium wastewater are obtained; the desulfated sodium wastewater is fed into a high-pressure reverse osmosis unit with an operating pressure of 7.5 MPa to obtain concentrated sodium chloride solution and desalted wastewater; the concentrated sodium sulfate solution is fed into a sodium sulfate MVR unit with an evaporation temperature of 80 °C and an evaporation pressure of 100 kPa, and industrial sodium sulfate is obtained after evaporation; the concentrated sodium chloride solution is fed into the sodium chloride MVR unit with an evaporation temperature of 80 °C and an evaporation pressure of 100 kPa, and industrial sodium chloride is obtained after evaporation.

[0072] The desalted wastewater is fed through the feed pipe 1 in the fiber amount detection unit as shown in Figure 3 . The fiber diameter and distribution in the desalted wastewater are detected by a laser particle size analyzer 3 to determine that the wastewater is low-fiber-content wastewater; the low-fiber-content wastewater is controlled by a control valve 2 and conveyed to the discharge pipe A21 for treatment in mode A.

[0073] The low-fiber-content wastewater is fed into an activated sludge unit for treatment for 2 hours and then into a biological contact oxidation unit for treatment for 1 hour to obtain pre-treated wastewater in mode A. The pre-treated wastewater in mode A is treated in a sedimentation aeration unit for 1 hour to obtain dye-enriched wastewater. The dye-enriched wastewater is fed into an adsorption precipitation separation unit for 2 hours and then into a coagulation unit for 1 hour to obtain an intermediate product. The intermediate product is fed into a reverse osmosis separation unit and treated for 4 hours under the conditions of a water flux of 40 L / (m 2 ·h) and a temperature of 37 °C to obtain reclaimed water and a dye recovery product.

[0074] Example 5

[0075] Different from Example 4, different sources of high-salt printing and dyeing wastewater are used, and the other process parameters are the same except for mode switching.

[0076] Source B of high-salt printing and dyeing wastewater: Acrylic-cotton blended fabric printing and dyeing section, with a salt content of 6.88 g / L, a fiber content of 1534.7 mg / L, and the main dye components being Brilliant Red 5GN and Reactive Brilliant Blue KN-R.

[0077] Among them, the process parameters of mode B are the same as those in Example 3.

[0078] Example 6

[0079] Different from Example 4, different sources of high-salt printing and dyeing wastewater are used, and the other process parameters are the same except for mode switching.

[0080] Source C of high-salt printing and dyeing wastewater: Silk fabric printing and dyeing section, with a salt content of 3.75 g / L, a fiber content of 769.2 mg / L, and the main dye components being Brilliant Red 5GN and Direct Lake Blue 5B.

[0081] Example 7

[0082] Different from Example 4, different sources of high-salt printing and dyeing wastewater were used, and the other process parameters were the same except for the mode switching.

[0083] Source D of high-salt printing and dyeing wastewater: the printing and dyeing section of polyester fabrics, with a salt content of 5.24 g / L, a fiber content of 783.4 mg / L, and the main components of the dyes being Disperse Yellow RGFL and Disperse Blue 2BLN.

[0084] Example 8

[0085] Different from Example 4, different sources of high-salt printing and dyeing wastewater were used, and the other process parameters were the same except for the mode switching.

[0086] Source E of high-salt printing and dyeing wastewater: the printing and dyeing section of linen fabrics, with a salt content of 5.24 g / L, a fiber content of 2139.5 mg / L, and the main components of the dyes being hematoxylin, Direct Fast Yellow RS, and Vat Blue RSN.

[0087] Among them, the process parameters of Mode B are the same as those in Example 3.

[0088] Experimental Example 3

[0089] The reclaimed water obtained in Examples 4 - 8 was detected according to the GB3838 - 2002 standard, and the test data were the pH value, dissolved oxygen, permanganate index, COD, and the contents of sulfate, chloride, nitrate, iron, and manganese. The relevant results are summarized in Table 3.

[0090] The content of dye molecules in the high-salt printing and dyeing wastewater sources A - E was analyzed by spectrophotometry, and the mass of dye molecules contained in the wastewater was calculated for 15 m 3 and compared with the mass of the recovered dyes obtained after treating 15 m 3 of wastewater in Examples 4 - 8. The relevant results are summarized in Table 4.

[0091] Table 3 Treatment effects of different types of wastewater

[0092]

[0093] Table 4 Dye recovery of different types of wastewater

[0094]

[0095] As shown in the wastewater treatment results in Table 3, the recovery processes corresponding to Examples 4-8 have good treatment effects on different types of printing and dyeing wastewater, and there is no need to establish additional treatment sections. The classification treatment of different types of wastewater can be completed through the automatic switching of the dual-mode system. For five different types of high-salt printing and dyeing wastewater, the reclaimed water after treatment meets the Class V water quality standard and can be recycled as industrial water or discharged harmlessly. Therefore, the recovery method designed by the present invention has excellent wastewater treatment effects and is applicable to various types of printing and dyeing wastewater.

[0096] As shown in the dye recovery data in Table 4, the recovery processes corresponding to Examples 4-8 not only efficiently treat different types of printing and dyeing wastewater but also have good dye recovery effects. The dyes involved in Wastewaters A-E mainly include azo dyes: Acid Red G, Direct Lake Blue 5B, Direct Fast Yellow RS, and Disperse Yellow RGFL; anthraquinone dyes: Disperse Blue 2BLN, Reactive Brilliant Blue KN-R, and Vat Blue RSN; and cationic dyes: hematoxylin and Brilliant Red 5GN. Therefore, the recovery process of the present invention has a certain recovery ability for different types of dyes such as azo dyes, anthraquinone dyes, and cationic dyes, and can comprehensively recover the high-value components while efficiently treating the sewage harmlessly.

[0097] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for recycling high-salt printing and dyeing wastewater based on a dual-mode system, characterized in that: The recycling method is as follows: The recycling method includes: preliminary precipitation treatment, inorganic salt recovery treatment, fiber quantity detection unit, A mode, B mode, dye recovery treatment and reverse osmosis separation treatment; The high-salt printing and dyeing wastewater is subjected to the preliminary precipitation treatment to obtain wastewater to be recycled; The wastewater to be recycled is subjected to the inorganic salt recovery treatment to obtain desalinated wastewater and inorganic salt recovery products; The desalinated wastewater is passed into the fiber content detection unit to detect whether the fiber content in the desalinated wastewater is higher than a threshold value; if the fiber content is lower than the threshold value, the desalinated wastewater is output as low-fiber wastewater for A-mode treatment to obtain A-mode pretreated wastewater; the A-mode includes aerobic biological treatment; if the fiber content is higher than the threshold value, the desalinated wastewater is output as high-fiber wastewater for B-mode treatment to obtain B-mode pretreated wastewater; the B-mode includes COD chemical treatment and COD biological treatment; Wherein, the COD biological treatment includes: an upflow anaerobic sludge unit; The A-mode pretreated wastewater and the B-mode pretreated wastewater are passed through a sedimentation aeration unit to obtain dye-enriched wastewater; the dye-enriched wastewater is subjected to the dye recovery treatment to obtain an intermediate product; the intermediate product is subjected to reverse osmosis separation treatment to obtain a dye recovery product and reclaimed water.

2. The method for recycling high-salt printing and dyeing wastewater based on a dual-mode system according to claim 1, characterized in that: The preliminary sedimentation treatment includes: a primary sedimentation tank, a filtration tank and a sedimentation-flotation combined treatment unit; the aeration intensity of the primary sedimentation tank is 10:1-12:1, and the aeration time is 3-4 hours; the filtration tank is a fast sand filter tank, wherein the filtration speed is 15-20m 3 / h; the average particle size of the quartz sand in the rapid sand filter is 0.8-1.2mm.

3. The method for recycling high-salt printing and dyeing wastewater based on a dual-mode system according to claim 2, characterized in that: The sedimentation-flotation combined treatment unit is as follows: the high-salt printing and dyeing wastewater passing through the filtration tank is passed into a sedimentation tank, the pH value is adjusted to 6-8, the high-salt printing and dyeing wastewater stays in the sedimentation tank for 2 hours to obtain post-settlement wastewater; the post-settlement wastewater is passed into a flotation tank, ferrous sulfate is added, and the addition amount of ferrous sulfate is 200 mg / L; the post-settlement wastewater stays in the flotation tank for 1 hour to obtain pre-flotation wastewater; polyacrylamide is added to the pre-flotation wastewater, wherein the addition amount of polyacrylamide is 3-7 mg / L; dissolved air water is passed into the pre-flotation wastewater, and scum and precipitate are removed after 1 hour to obtain the wastewater to be recycled.

4. The method for recycling high-salt printing and dyeing wastewater based on a dual-mode system according to claim 1, characterized in that: The inorganic salt recovery treatment comprises: an electrodialysis unit, a sodium sulfate mechanical vapor recompression evaporation unit, a high-pressure reverse osmosis unit and a sodium chloride mechanical vapor recompression evaporation unit; the wastewater to be recovered is passed through the electrodialysis unit to obtain a sodium sulfate concentrate and desulfurized sodium wastewater; the desulfurized sodium wastewater is passed through the high-pressure reverse osmosis unit to obtain a sodium chloride concentrate and the desalinated wastewater; the sodium sulfate concentrate is passed through the sodium sulfate mechanical vapor recompression evaporation unit to obtain industrial sodium sulfate; the sodium chloride concentrate is passed through the sodium chloride mechanical vapor recompression evaporation unit to obtain industrial sodium chloride; the desalinated wastewater is passed through the fiber amount detection unit for further treatment; the inorganic salt recovery products comprise: the industrial sodium sulfate and the industrial sodium chloride.

5. The method for recycling high-salt printing and dyeing wastewater based on a dual-mode system according to claim 1, characterized in that: The fiber quantity detection unit comprises: a feed pipe (1), a control valve (2), a discharge pipe A (21), a discharge pipe B (22) and a laser particle size analyzer (3); the fiber content is the total content of chemical fibers and natural fibers; the chemical fibers include polyester fibers and nylon fibers; the natural fibers include cotton fibers, hemp fibers and silk fibers; the fiber content threshold is 1000 mg / L.

6. The method for recycling high-salt printing and dyeing wastewater based on a dual-mode system according to claim 5, characterized in that: The working process of the fiber quantity detection unit is as follows: The desalinated wastewater is introduced through a feed pipe (1), and the fiber particle size and distribution in the desalinated wastewater are tested by a laser particle size analyzer (3), and the fiber content in the desalinated wastewater is calculated; If the fiber content is lower than 1000 mg / L, the desalinated wastewater is output as the low-fiber wastewater and is controlled by the control valve (2) to be transported to the discharge pipe A (21); If the fiber content is higher than 1000 mg / L, the desalinated wastewater is output as the high-fiber wastewater, which is controlled by the control valve (2) and transported to the discharge pipe B (22); The discharge pipe A (21) leads to the A mode; the discharge pipe B (22) leads to the B mode.

7. The method for recycling high-salt printing and dyeing wastewater based on a dual-mode system according to claim 1, characterized in that: The aerobic biological treatment comprises: an activated sludge unit and a biological contact oxidation unit; after the low-fiber wastewater is treated in the activated sludge unit for 2 hours, it is treated in the biological contact oxidation unit for 1-2 hours to obtain the A-mode pretreated wastewater.

8. The method for recycling high-salt printing and dyeing wastewater based on a dual-mode system according to claim 1, characterized in that: The COD chemical treatment includes: an adsorption-coagulation unit and a redox unit; after the high-fiber wastewater is passed through the adsorption-coagulation unit for 2 hours, it is passed through the redox unit for 3 hours, and then passed through the upflow anaerobic sludge unit for 1-2 hours to obtain B-mode pretreated wastewater.

9. The method for recycling high-salt printing and dyeing wastewater based on a dual-mode system according to claim 1, characterized in that: The dye recovery process comprises: an adsorption precipitation separation unit and a coagulation unit; the dye-enriched wastewater is passed through the adsorption precipitation separation unit for 1-3 hours, and then passed through the coagulation unit for 1 hour to obtain the intermediate product.

10. The method for recycling high-salt printing and dyeing wastewater based on a dual-mode system according to claim 1, characterized in that: The reverse osmosis separation treatment comprises: a reverse osmosis separation unit; passing the intermediate product into the reverse osmosis separation unit, and obtaining the reclaimed water and the dye recovery product after 3-5 hours of treatment; the water flux of the reverse osmosis separation unit is 30-50L / (m 2 h), the temperature is 35-40°C.

Images