A process for treating and recycling printing and dyeing wastewater

Abstract

The invention relates to the technical field of printing and dyeing wastewater treatment. In order to solve the problems of poor treatment effect and high treatment cost of printing and dyeing wastewater under the prior art, a printing and dyeing wastewater reaching standard and reuse treatment process is disclosed, which comprises the following steps: aeration after removing floating objects from the printing and dyeing wastewater, and then adding a coagulant to the printing and dyeing wastewater; acid adjustment after removing precipitation, and then iron-carbon micro-electrolysis; alkali adjustment pH, and then mixing with a coagulant, a coagulant aid and tourmaline; hydrolysis acidification and A / O treatment after removing suspended objects, and then mixing with a coagulant and a coagulant aid; after removing precipitation, filtering through an ultrafiltration membrane and a reverse osmosis membrane to obtain recycled water; after iron-carbon micro-electrolysis and Fenton oxidation of reverse osmosis concentrated water, mixing with ultrafiltration backwash water, and then adding a coagulant, a coagulant aid and tourmaline, and removing precipitation and discharging. The recycled water treated by the treatment process can be used again in the textile printing and dyeing process, which reduces water pressure, reduces wastewater treatment costs, and the water quality of the external drainage meets the standard and contains less antimony.

Description

Technical Field

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

[0002] Printing and dyeing wastewater is a type of industrial wastewater that is difficult to treat. It has the characteristics of large water volume, high content of organic pollutants, deep chroma, high alkalinity, and large changes in water quality. Printing and dyeing wastewater is mainly produced in the pre-treatment, dyeing, printing and finishing processes in the printing and dyeing process. Its main pollutants are hemicellulose, pulp, oil, residual dyes and auxiliaries. The auxiliaries used in the printing and dyeing process contain heavy metals chromium and antimony, and some dyes are biologically toxic, such as phthalobromonium salt dyes and azo dyes. Therefore, printing and dyeing wastewater cannot be directly treated by biochemical treatment methods, but requires pretreatment to improve the biodegradability of printing and dyeing wastewater, and combined with other treatment technologies to improve the treatment effect. At present, the printing and dyeing wastewater treatment process still has problems such as poor effluent quality and high treatment costs.

[0003] For example, the "A Printing and Dyeing Wastewater Treatment Process" disclosed in the Chinese patent literature, with the publication number CN105481205A, includes the following steps: the wastewater is filtered through a grid and then pumped into a regulating tank to adjust its pH; the treated wastewater in the previous step is pumped into a primary reaction tank, and activated sludge is added, and after standing for 0.5 hours, the pH value is adjusted at 2-4 g / m 3 Add MgSO4 and 1-3g / m 3 FeSO4 is added to the wastewater, and 120-150V direct current is introduced to keep the wastewater for 2-4 hours; the wastewater is pumped into a closed aerobic tank and kept in the aerobic tank for 4-7 hours; the wastewater is pumped into an anaerobic bioreactor and the impurities in the wastewater are removed by anaerobic treatment; the effluent from the anaerobic bioreactor is pumped into a flotation tank for flotation treatment. This process improves the degradation effect of difficult-to-decompose organic molecules in wastewater through direct current electrolysis, but it consumes a lot of energy, has high wastewater treatment costs, and has poor removal effect on heavy metal elements. Summary of the invention

[0004] In order to overcome the problems of poor treatment effect and high treatment cost of printing and dyeing wastewater under the prior art, the present invention provides a printing and dyeing wastewater reaching standard and recycling treatment process, which has good treatment effect on printing and dyeing wastewater, and the treated recycled water can be used again in textile printing and dyeing process, thereby alleviating the water pressure of enterprises and reducing the wastewater treatment cost.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A printing and dyeing wastewater treatment process for reaching standards and recycling, comprising the following steps:

[0007] (1) After removing floating matter from the printing and dyeing wastewater, aeration is performed, and then a coagulant is added to the printing and dyeing wastewater for reaction;

[0008] (2) After removing the precipitate from the printing and dyeing wastewater, acid is added to adjust the pH, and then iron-carbon micro-electrolysis is performed;

[0009] (3) adding alkali to the printing and dyeing wastewater after iron-carbon micro-electrolysis to adjust the pH, and then mixing it with coagulant, coagulant aid and tourmaline;

[0010] (4) After the suspended solids are removed from the printing and dyeing wastewater, it is hydrolyzed and acidified, and then A / O treated, and then mixed with a coagulant and a coagulant aid;

[0011] (5) After the precipitation is removed from the printing and dyeing wastewater, it is filtered through an ultrafiltration membrane and a reverse osmosis membrane to obtain recycled water;

[0012] (6) The reverse osmosis concentrate is subjected to iron-carbon micro-electrolysis and Fenton oxidation, then mixed with ultrafiltration backwash water, and coagulant, coagulant aid and tourmaline are added to remove the precipitate and discharge it.

[0013] The printing and dyeing process is carried out at high temperature and also includes steps such as reduction cleaning and alkaline washing. Therefore, the printing and dyeing wastewater has the characteristics of high temperature and strong alkalinity. The present invention first removes large particles of garbage and fiber in the printing and dyeing wastewater by filtering, then uses aeration to even out the water quality of the printing and dyeing wastewater and reduce the temperature of the printing and dyeing wastewater, and then adds a coagulant and a coagulant aid to remove flocculent precipitates in the printing and dyeing wastewater; the iron-carbon micro-electrolysis treatment can degrade the difficult-to-degrade organic pollutants in the printing and dyeing wastewater, so that the wastewater is decolorized, COD is reduced and the biodegradability of the printing and dyeing wastewater is improved, and the insoluble matter in the printing and dyeing wastewater can be coagulated and flocculated by Fe(OH)2 and Fe(OH)3 generated in the iron-carbon micro-electrolysis and separated from the wastewater; the printing and dyeing wastewater treated with micro-electrolysis can hydrolyze the insoluble organic matter in the printing and dyeing wastewater into soluble organic matter by hydrolysis and acidification, and convert the difficult-to-biodegrade macromolecular substances into easily biodegradable small molecular substances, thereby improving the biodegradability of the wastewater to remove COD, and improving the subsequent A / O treatment effect, and then further decomposing the organic matter through A / O biochemical treatment, and finally obtaining recycled water through an ultrafiltration-reverse osmosis process, and the recycled water can be reused in the textile printing and dyeing process. The concentrated water produced by ultrafiltration-reverse osmosis has a higher concentration of pollutants. After mixing with backwash water, the concentration of pollutants is reduced. The organic matter is decomposed through iron-carbon micro-electrolysis and Fenton reaction, and the precipitate is removed to make the wastewater meet the discharge standard.

[0014] Preferably, the coagulant is polyferric sulfate or polyaluminium sulfate, and the coagulant aid is polyacrylamide, wherein the dosage of polyferric sulfate is 0.10-0.15% of the mass of the printing and dyeing wastewater, the dosage of polyaluminium sulfate is 0.05-0.10% of the mass of the printing and dyeing wastewater, and the dosage of polyacrylamide is 0.02-0.03% of the mass of the printing and dyeing wastewater.

[0015] Printing and dyeing wastewater contains heavy metal elements such as antimony and chromium, among which antimony is a wastewater pollutant that the country has focused on monitoring in recent years. Since antimony-containing catalysts are used in the synthesis of polyester fibers, the antimony element in the fibers will be released into the printing and dyeing wastewater during printing and dyeing, resulting in a high antimony content in the printing and dyeing wastewater. Both polyferric sulfate and polyaluminium sulfate have good flocculation effects, among which polyferric sulfate has a better effect on removing antimony.

[0016] Preferably, the particle size of the tourmaline is 0.1-1 μm, and the dosage of the tourmaline is 0.5-0.1% of the mass of the printing and dyeing wastewater.

[0017] Tourmaline solution can further enhance the precipitation effect of flocculants, reduce turbidity and reduce the concentration of heavy metal ions.

[0018] Preferably, in the step (2), the printing and dyeing wastewater after removing the precipitate is acidified to adjust the pH to 3-4, and then iron-carbon micro-electrolysis is carried out under the action of iron-carbon filler, and the wastewater is aerated during the iron-carbon micro-electrolysis, and the iron-carbon micro-electrolysis time is 20-60 minutes.

[0019] Iron-carbon micro-electrolysis is carried out in an acidic environment, and the acid can be sulfuric acid, hydrochloric acid or oxalic acid. The free hydrogen [H] and O· generated during the iron-carbon micro-electrolysis process have strong redox activity, which can destroy the carbon chains of some difficult-to-degrade organic pollutants and improve the biodegradability of printing and dyeing wastewater; aeration during iron-carbon micro-electrolysis can promote full contact between wastewater and iron-carbon filler and reduce the caking of iron-carbon filler; some organic pollutants can also be subsequently precipitated as coagulation and flocculation of Fe(OH)2 and Fe(OH)3 and removed.

[0020] Preferably, in the step (3), alkali is added to the printing and dyeing wastewater after iron-carbon micro-electrolysis to adjust the pH value to 8.5-9.5.

[0021] After iron-carbon micro-electrolysis, the pH of the wastewater is still acidic. After adjusting to alkalinity, the coagulation effect of Fe(OH)2 and Fe(OH)3 is achieved.

[0022] Preferably, after the printing and dyeing wastewater is biochemically treated in step (4), sodium carbonate is added to adjust the pH to 6-7, and then mixed with polyaluminium sulfate and polyacrylamide, wherein the amount of polyaluminium sulfate added is 0.05-0.10% of the mass of the printing and dyeing wastewater, and the amount of polyacrylamide added is 0.02-0.03% of the mass of the printing and dyeing wastewater.

[0023] Iron ions can easily contaminate the reverse osmosis membrane, so polyaluminum sulfate and polyacrylamide are used for precipitation in the step, which has a good precipitation effect and reduces the iron ion content in the wastewater.

[0024] Preferably, in the step (5), after the precipitation is removed from the printing and dyeing wastewater, it is first filtered through a quartz sand filter layer and then filtered through an ultrafiltration membrane and a reverse osmosis membrane.

[0025] Preferably, in the step (6), the iron-carbon micro-electrolysis and Fenton oxidation process is to add acid to the reverse osmosis concentrated water to a pH of 3-4, then mix with the iron-carbon filler for reaction for 40-75 minutes, and then mix with hydrogen peroxide and ferrous sulfate, wherein the addition amount of hydrogen peroxide is 50-200 mg / L, and the addition amount of ferrous sulfate is 15-100 mg / L.

[0026] Iron-carbon micro-electrolysis and Fenton reaction can further remove refractory pollutants in reverse osmosis concentrate.

[0027] Preferably, the step (6) further comprises subjecting the reverse osmosis concentrate to iron-carbon micro-electrolysis and Fenton oxidation, and then mixing it with ultrafiltration backwash water, adding a coagulant and a coagulant aid, removing the precipitate, and discharging it after modified polyacrylamide gel filtration.

[0028] Modified polyacrylamide gel can adsorb heavy metal ions in wastewater, so that the concentration of heavy metal ions in the external drainage can be further reduced on the basis of meeting the discharge standards.

[0029] Preferably, the modified polyacrylamide gel in step (6) is prepared by the following steps:

[0030] A. Add 1,2-diaminetetraacetic acid and ammonium persulfate into water and stir for 10-20 minutes;

[0031] B. Add acrylamide and N,N'-methylenebisacrylamide, stir for 3-8 minutes and then stand at room temperature for 2-4 hours to obtain a gel;

[0032] C. Wash and dry the gel for later use;

[0033] The mass volume ratio of propane-1,2-diaminetetraacetic acid, ammonium persulfate, acrylamide, N,N'-methylenebisacrylamide and water is (0.5-1): (2-5) g: (10-15) g: (2-3) g: 100 mL.

[0034] The polyacrylamide in the modified polyacrylamide gel is grafted with 1,2-diaminetetraacetic acid, which has a good adsorption effect on heavy metal ions in wastewater and can further reduce the concentration of heavy metal ions in the external drainage.

[0035] Therefore, the present invention has the following beneficial effects: (1) it can effectively reduce the COD, chromaticity and heavy metal concentration in printing and dyeing wastewater, obtain recycled water with good water quality that can be reused in textile printing and dyeing, and reduce the water pressure of enterprises; (2) it can further treat the reverse osmosis concentrated water and ultrafiltration backwash water generated in the ultrafiltration-reverse osmosis process to meet the discharge standards; (3) the wastewater treatment cost is low and can be promoted and applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a specific flow chart of Example 1. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0038] In the following specific implementation method, wastewater from the textile industrial park is taken as the treatment object, and its water quality is shown in Table 1.

[0039] Table 1. Wastewater quality

[0040]

[0041] Example 1

[0042] A printing and dyeing wastewater treatment process for reaching standards and recycling, such as Figure 1 As shown, the following steps are included:

[0043] (1) The printing and dyeing wastewater passes through a grating with a grating gap of 5 mm to remove the large screen residue in the wastewater, and then flows into the regulating tank by gravity, and aeration is carried out by bubbles generated by the aeration pipe;

[0044] (2) The wastewater from the regulating tank is pumped to the coagulation sedimentation tank, and polyferric sulfate and PAM are added. The dosage of polyferric sulfate and PAM is 0.12wt% and 0.02wt%. After sufficient reaction, the sludge is separated from the water in the high-efficiency sedimentation tank. The sludge enters the sludge thickening tank, and the supernatant of the sedimentation tank enters the acid adjustment tank;

[0045] (3) adding sulfuric acid to the acid adjustment tank to adjust the pH to 3, and then flowing into the intermediate water tank, and then being lifted by a pump into the EBR iron-carbon micro-electrolysis tower, which is equipped with a Φ12mm iron-carbon filler, and an aeration pipe at the bottom to generate bubbles for aeration. The effective contact reaction time of the wastewater in the EBR iron-carbon micro-electrolysis tower is 30 minutes, and the effluent after the reaction enters the neutralization sedimentation tank;

[0046] (4) After the pH value of the neutralization sedimentation tank is adjusted to 8.5 by adding sodium hydroxide, the pH value enters the secondary coagulation sedimentation tank, and the reaction precipitation is carried out by adding polyferric sulfate, PAM and tourmaline. The dosage of polyferric sulfate, PAM and tourmaline is 0.12wt%, 0.02wt% and 0.5wt% respectively. The precipitated water enters the ABR high-efficiency hydrolysis system;

[0047] (5) After hydrolysis and acidification, the wastewater enters the Bio-Sim integrated multi-organism optimization reaction tank. The influent is mixed with the sludge pushed by the scraper below after the inclined tube sedimentation in the aerobic zone and then enters the gallery aerobic tank. The effluent from the aerobic tank enters the high-density sedimentation tank;

[0048] (6) After the wastewater in the high-density sedimentation tank is stirred and mixed, 0.1wt% PAC and 0.02wt% PAM are added for coagulation and then efficiently precipitated. The effluent from the high-density sedimentation tank enters the final sedimentation tank and the V-type filter tank respectively. The effluent volume ratio entering the final sedimentation tank and the V-type filter tank is 1:5;

[0049] (7) After the wastewater in the V-type filter is filtered through the quartz sand filter layer of the V-type filter, it is pumped to the ultrafiltration system and then enters the reverse osmosis system for treatment. The recycled water flows into the clean water tank. The effluent from the clean water tank can be reused for production water in printing and dyeing enterprises.

[0050] (8) The reverse osmosis concentrated water produced by the reverse osmosis system enters the EBR iron-carbon micro-electrolysis tower to react for 60 minutes, and then enters the Fenton oxidation tank to react with hydrogen peroxide and ferrous sulfate. The dosage of hydrogen peroxide and ferrous sulfate is 150 mg / L, and the dosage of ferrous sulfate is 80 mg / L. After the reaction, it is mixed with the ultrafiltration backwash water produced by the ultrafiltration system and discharged into the final sedimentation tank;

[0051] (9) The wastewater in the final sedimentation tank is subjected to coagulation reaction with 0.12wt% polyferric sulfate, 0.02wt% PAM and 0.5wt% tourmaline solution, and is discharged after final sedimentation and meets the standards;

[0052] (10) The sludge thickening tank collects the sludge from the coagulation sedimentation tank, neutralization sedimentation tank, high-density sedimentation tank, final sedimentation tank, and the residual sludge from the Bio-Sim integrated multi-organism optimization reaction tank, and then pumps it into the plate and frame filter press. After dehydration, the sludge is spirally conveyed to the solid waste disposal center for centralized treatment, and the filtered clear liquid is returned to the screen well.

[0053] Example 2

[0054] A process for treating and reusing printing and dyeing wastewater, which differs from Example 1 in that in step (9), the wastewater in the final sedimentation tank is subjected to coagulation reaction with 0.12wt% polyferric sulfate, 0.02wt% PAM and 0.5wt% tourmaline, and the supernatant is made to flow into a pipe containing modified polyacrylamide gel and then discharged;

[0055] The modified polyacrylamide gel is prepared by the following steps:

[0056] A. Add 50g of propane-1,2-diaminetetraacetic acid and 250g of ammonium persulfate into 5L of water and stir for 10min;

[0057] B. Add 750 g acrylamide and 150 g N,N'-methylenebisacrylamide, stir for 3 min and let stand for 4 h at room temperature to obtain a gel;

[0058] C. Wash the gel and put it into the pipeline.

[0059] The water quality of the recycled water obtained by the process described in Example 1 and the water quality of the external drainage of Example 1 and Example 2 were respectively detected. The detection method referred to the "Textile Dyeing and Finishing Industry Recycled Water Quality Standard" (FZT 01107-2011) and the "Textile Dyeing and Finishing Industry Water Pollutant Discharge Standard" (GB4287-2012). The results are shown in Tables 2 and 3.

[0060] Table 2. Recycled water quality

[0061]

[0062] Table 3. External drainage water quality

[0063]

[0064] The quality of the recycled water obtained in Example 1 is good, and the concentrations of various pollutants are far lower than the limit values ​​specified in the water quality standard for recycled water in the textile dyeing and finishing industry. In addition, the water quality of the external drainage of Example 1 is better than the water pollutant discharge standard for the textile dyeing and finishing industry, and the total antimony concentration in the external drainage of Example 2 is further reduced, which shows that the modified polyacrylamide gel has a good adsorption effect on low-concentration heavy metal ions.

Claims

1. A process for treating and recycling printing and dyeing wastewater, characterized in that it includes: Follow these steps: (1) After removing floating matter from the printing and dyeing wastewater, aeration is performed, and then a coagulant is added to the printing and dyeing wastewater for reaction; (2) After removing the precipitate from the printing and dyeing wastewater, acid is added to adjust the pH, and then iron-carbon micro-electrolysis is performed; (3) After iron-carbon micro-electrolysis, the printing and dyeing wastewater is added with alkali to adjust the pH, and then mixed with coagulant, coagulant aid and tourmaline; (4) After removing suspended solids from the printing and dyeing wastewater, it is hydrolyzed and acidified, treated with A / O, and then mixed with coagulants and coagulant aids; (5) After the printing and dyeing wastewater is freed from sediment, it is filtered through an ultrafiltration membrane and a reverse osmosis membrane to obtain recycled water; (6) After the reverse osmosis concentrate is subjected to iron-carbon micro-electrolysis and Fenton oxidation, it is mixed with ultrafiltration backwash water, and then a coagulant, a coagulant aid and tourmaline are added to remove the precipitate and filter it through modified polyacrylamide gel before discharge; The modified polyacrylamide gel is prepared by the following steps: A. Add 1,2-diaminetetraacetic acid and ammonium persulfate into water and stir for 10-20 minutes; B. Add acrylamide and N,N'-methylenebisacrylamide, stir for 3-8 minutes and then stand at room temperature for 2-4 hours to obtain a gel; C. Wash and dry the gel for later use; The mass volume ratio of propane-1,2-diaminetetraacetic acid, ammonium persulfate, acrylamide, N,N'-methylenebisacrylamide and water is (0.5-1): (2-5) g: (10-15) g: (2-3) g: 100 mL.

2. A printing and dyeing wastewater treatment process for reaching standards and recycling according to claim 1, characterized in that: The coagulant is polyferric sulfate or polyaluminium sulfate, and the coagulant aid is polyacrylamide, wherein the dosage of polyferric sulfate is 0.10-0.15% of the mass of the printing and dyeing wastewater, the dosage of polyaluminium sulfate is 0.05-0.10% of the mass of the printing and dyeing wastewater, and the dosage of polyacrylamide is 0.02-0.03% of the mass of the printing and dyeing wastewater.

3. A printing and dyeing wastewater treatment process for reaching standards and recycling according to claim 1 or 2, characterized in that: The particle size of the tourmaline is 0.1-1 μm, and the dosage of the tourmaline is 0.5-0.1% of the mass of the printing and dyeing wastewater.

4. A printing and dyeing wastewater treatment process for reaching standards and recycling according to claim 1, characterized in that: In the step (2), the printing and dyeing wastewater after the precipitation is removed is acidified to adjust the pH value to 3-4, and then iron-carbon micro-electrolysis is performed under the action of iron-carbon filler. During the iron-carbon micro-electrolysis, the wastewater is aerated, and the iron-carbon micro-electrolysis time is 20-60 minutes.

5. A printing and dyeing wastewater treatment process for reaching standards and recycling according to claim 1, characterized in that: In the step (3), alkali is added to the printing and dyeing wastewater after iron-carbon micro-electrolysis to adjust the pH value to 8.5-9.

5.

6. A printing and dyeing wastewater treatment process for reaching standards and recycling according to claim 1 or 5, characterized in that: After the printing and dyeing wastewater is biochemically treated in step (4), sodium carbonate is added to adjust the pH to 6-7, and then the wastewater is mixed with polyaluminium sulfate and polyacrylamide, wherein the amount of polyaluminium sulfate added is 0.05-0.10% of the mass of the printing and dyeing wastewater, and the amount of polyacrylamide added is 0.02-0.03% of the mass of the printing and dyeing wastewater.

7. A dyeing wastewater treatment process for reaching standards and recycling according to claim 1, characterized in that: In the step (5), after the precipitation is removed from the printing and dyeing wastewater, it is first filtered through a quartz sand filter layer and then filtered through an ultrafiltration membrane and a reverse osmosis membrane.

8. A process for treating and recycling printing and dyeing wastewater according to claim 1, characterized in that: In the step (6), the iron-carbon micro-electrolysis and Fenton oxidation process is to add acid to the reverse osmosis concentrated water until the pH is 3-4, then mix with the iron-carbon filler for reaction for 40-75 minutes, and then mix with hydrogen peroxide and ferrous sulfate, wherein the addition amount of hydrogen peroxide is 50-200 mg / L, and the addition amount of ferrous sulfate is 15-100 mg / L.

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