CN110194559B - Process method for zero discharge and resource recycling of colored spun yarn dyeing wastewater - Google Patents

Abstract

The invention relates to a process method for zero discharge and resource recycling of colored spun yarn dyeing wastewater, which comprises the following steps: (1) carrying out biochemical treatment on the colored spun yarn dyeing wastewater; (2) performing ultrafiltration and reverse osmosis treatment on the wastewater after biochemical treatment; (3) the reverse osmosis concentrated water enters a nanofiltration separation system, decolorization is firstly carried out, the decolorized concentrated water is treated as hazardous waste through evaporative crystallization, the decolorized clear water is purified again, the purified concentrated water is used for a dyeing process after being decolorized and softened, and the purified clear water and the reverse osmosis filtered clear water are combined and used for a whole-stage production process. In the invention, the concentrated brine obtained by concentrating the purified concentrated water is used for dyeing in the dyeing process section, so that the addition amount of anhydrous sodium sulphate is saved; meanwhile, the reuse rate of the printing and dyeing wastewater in the invention is up to 95%, and more than 80% of the inorganic salt in the recovered wastewater can be used for the dyeing process; because the evaporation capacity is reduced by 95 percent, the total cost of water treatment per ton is greatly reduced, thereby having good economic benefit and social benefit.

Description

Process method for zero discharge and resource recycling of colored spun yarn dyeing wastewater

Technical Field

The invention relates to the field of printing and dyeing wastewater treatment, in particular to a process method for zero discharge and resource recycling of colored spun yarn dyeing wastewater.

Background

The colored spun yarn is produced by dyeing fiber into colored fiber, mixing two or more kinds of fiber in different colors, and spinning to obtain yarn with unique color mixing effect. Compared with the traditional process, the dyeing-first spinning production process of the colored spun yarn saves water and reduces emission by more than 50 percent, and meets the requirements of low carbon and environmental protection. In the whole textile industry, the traditional process accounts for about 65%, the dyed yarns account for about 20%, and the colored spun yarns account for about 15%, so that the growing space of the colored spun yarns is large. At present, the production is pulled by circulation, and if the consumption pulling production is realized in the future, the prospect of the colored spun yarn is immeasurable.

The dye mainly used in the current stage of colored spun yarn is reactive dye, and about 6 percent of anhydrous sodium sulphate (sodium sulfate) is required to be added as a solubilizer to increase the coloring rate in the dyeing process, so that the coloring rate is improved. Therefore, the main component of the salt of the TDS in the dyeing wastewater of the colored spun yarns is sodium sulfate. The salt can not be removed in the biochemical treatment, and the waste water can be discharged into the environment along with the waste water after the biochemical treatment, thereby causing serious pollution to the environment.

When 1t of cotton loose fiber or yarn is dyed, about 80t of dyeing wastewater is generated. Due to the improvement of the dyeing process, wastewater which is difficult to be biochemically treated, such as desizing wastewater, alkali decrement wastewater, vulcanizing wastewater and the like, is not generated, and in addition, active dye is mainly used, so the biochemical treatment difficulty of the wastewater is lower, and the COD content of effluent can be treated to be below 100 mg/l; the TDS content of the waste water is about 0.8-1%, and the main component of the waste water is sodium sulfate added in the dyeing process. The basic treatment mode at the present stage is that after the wastewater is subjected to biochemical treatment, the wastewater is recovered by a reverse osmosis membrane by 50 percent, and the other 50 percent of the wastewater is discharged.

In 50% of discharged wastewater, 1.6% -2% of sodium sulfate is contained, and the wastewater is discharged into the environment, so that not only is the environment polluted, but also the waste of water resources and sodium sulfate is caused. Therefore, the wastewater is treated to recover water resources and sodium sulfate resources, and the method has good economic and social benefits.

If the wastewater is treated by a zero-emission process, the traditional process route is that the RO concentrated solution is continuously concentrated to about TDS 10% by high-pressure reverse osmosis processes such as DTRO and the like again. The DTRO concentrated solution is treated by multiple-effect evaporation or MVR and other thermal concentration processes, and the evaporated solid becomes hazardous waste for additional treatment. The process has high investment cost, a large amount of heat energy is used for evaporation, the process running cost is high, about 10kg of dangerous waste is generated when 1 ton of wastewater is treated, and about 17-30 KWh of electric energy and medicament loss are consumed.

CN206244574U discloses a zero discharge system of high-salt printing and dyeing wastewater, which adopts a salt-separating selective electric drive membrane to separate sulfate ions and chloride ions from the wastewater at different concentrations; the method only concentrates partial anions in the salt solution, and has narrow application range.

CN104086043A discloses a method for treating printing and dyeing wastewater, which adopts a biochemical process, an ultrafiltration process and an ion exchange process, and has the problems that an ultrafiltration membrane is easy to pollute and is not easy to clean and ion exchange resin is regenerated to pollute regenerated liquid. And only water resources are recycled, and other mineral resources in the wastewater are not recycled.

CN101293726A discloses a process for treating printing and dyeing wastewater by using biochemical treatment, ultrafiltration and reverse osmosis and using the wastewater according to different qualities. One of the cores of the process is ultrafiltration and reverse osmosis treatment, and the process has the defects that the problems of pollution and service life of the ultrafiltration membrane cannot be solved. According to engineering experience, the problem that the cleaning flux of the ultrafiltration membrane cannot be recovered after pollution occurs. And mineral resources in the wastewater are not recycled, so that the water recovery rate is low.

CN207468344U discloses a effluent treatment plant, the device includes waste water preliminary sedimentation pond, buffer pool, elevator pump, neutralization tank, reaction box, flocculation box, concentration clarification tank, play water tank mud buffer tank and hydroextractor. The device has weak pertinence and insufficient treatment capacity for printing and dyeing wastewater.

Although the above documents provide certain help for the treatment of dyeing wastewater, the problems of no recycling of mineral resources in wastewater, low water recovery rate and the like still exist, so that the development of a process for zero discharge of dyeing wastewater of colored spun yarns and recycling of resources is of great significance.

Disclosure of Invention

In view of the technical problems in the prior art, the invention aims to provide a process method for zero discharge of colored spun yarn dyeing wastewater and resource recycling, which comprises biochemical treatment, reverse osmosis treatment and nanofiltration separation treatment; the recovery rate of water is more than 95 percent, the recovery rate of sodium sulfate is more than 80 percent, and the recycled water can be used for the working procedures of boiling, cleaning, dyeing and the like; and inorganic salts such as sodium sulfate and the like in the wastewater are extracted and reused in the dyeing process, so that water resources and mineral resources are saved.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a process method for zero discharge of colored spun yarn dyeing wastewater and resource recycling, which comprises the following steps:

(1) carrying out biochemical treatment on the colored spun yarn dyeing wastewater;

(2) performing ultrafiltration and reverse osmosis treatment on the wastewater after biochemical treatment;

(3) the reverse osmosis concentrated water enters a nanofiltration separation system, decolorization is carried out firstly, and residues obtained by evaporating and crystallizing the decolorized concentrated water are treated as hazardous waste; and (3) purifying the decolored clear water, decoloring and softening the purified concentrated water, using the concentrated water in a dyeing process to replace anhydrous sodium sulphate, and combining the purified clear water and the reverse osmosis filtered clear water for a full-section production process.

After biochemical treatment, ultrafiltration and reverse osmosis treatment, carrying out nanofiltration separation treatment on reverse osmosis concentrated water, wherein the decolorized concentrated water can collect 60-85% of total organic matters and 7-15% of total inorganic salts in the colored spun yarn dyeing wastewater; the residue obtained by evaporating and crystallizing the decolored concentrated water can be directly used as hazardous waste for treatment, so that most of the treatment on the colored spinning wastewater is realized; meanwhile, the salt content of the concentrated water obtained after purification reaches 5-15%, and the concentrated water can be directly used for a dyeing process to replace anhydrous sodium sulphate, so that the addition amount of the anhydrous sodium sulphate is saved, and the discharge of the anhydrous sodium sulphate to the environment is reduced.

The process method provided by the invention enables the reuse rate of the printing and dyeing wastewater to be more than 95%, and only water lost in the production and evaporation processes is supplemented every day; in addition, more than 80% of inorganic salt in the wastewater can be recycled and used for the dyeing process, so that the cost for purchasing a large amount of inorganic salt is saved for enterprises, the discharge of the inorganic salt is reduced, and good economic benefit is generated.

Preferably, the biochemical treatment in step (1) comprises anaerobic acidification hydrolysis and aerobic biochemical treatment.

Preferably, the treatment time of the anaerobic acidification hydrolysis is 12-24 h, such as 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h and 24 h.

Preferably, the time of the aerobic biochemical treatment is 24-36 h, such as 24h, 26h, 28h, 30h, 32h, 33.5h, 34h and 36 h.

Preferably, the colored spun yarn dyeing wastewater in the step (1) firstly enters an anaerobic acidification hydrolysis tank, the anaerobic residence time is 12-24 hours, the effluent of the acidification hydrolysis tank enters an aerobic biological tank, and the aerobic tank residence time is 24-36 hours.

Preferably, the COD of the effluent of the aerobic tank is less than 200mg/L, and the turbidity is less than 10 NTU.

Preferably, the reverse osmosis treatment in step (2) has an operating pressure of 2.0 to 4.0MPa, such as 2.0MPa, 2.1MPa, 2.2MPa, 2.5MPa, 3.0MPa, 3.2MPa, 3.5MPa, 4.0 MPa.

Preferably, the pressurization mode of the reverse osmosis treatment is a two-stage or three-stage interstage pressurization design.

Preferably, the ultrafiltration membrane elements used in the ultrafiltration and reverse osmosis treatment have a molecular weight cut-off of 5000-300000D, such as 5000D, 8000D, 10000D, 200000D, 300000D.

The ultrafiltration system of the invention preferably adopts an internal MBR membrane or an external column type hollow fiber membrane for filtration, and has more excellent filtration effect.

Preferably, the pressure of the decoloring treatment in the step (3) is 1.0 to 3.0MPa, such as 1.0MPa, 1.1MPa, 1.2MPa, 1.5MPa, 2.0MPa, 2.2MPa, 2.5MPa, and 3.0 MPa.

Preferably, the decoloring treatment is performed by using a decoloring nanofiltration membrane.

Preferably, the membrane elements adopted by the decolorizing nanofiltration membrane have the molecular weight cut-off of 200-1000D, such as 200D, 300D, 500D, 800D and 1000D.

Preferably, the working temperature of the membrane element is 10 to 80 ℃, such as 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃ and 80 ℃.

Preferably, the decolorizing nanofiltration membrane is a roll-type or tubular nanofiltration membrane.

Preferably, the purification of the clear water after decolorization in the step (3) is performed by using a purification nanofiltration membrane.

Preferably, the molecular weight cut-off of a membrane element adopted by the purification nanofiltration membrane is 100-800D, such as 100D, 200D, 300D, 500D and 800D.

Preferably, the working temperature of the membrane element is 10-80 ℃.

Preferably, the concentrated water obtained by purification is decolorized by powdered activated carbon or ozone oxidation.

Preferably, the powdered activated carbon used for decoloring is added in an amount of 0.1 to 0.5%, for example, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%.

In the invention, the water recovery rate after reverse osmosis treatment in the step (2) is 65-85%; and (4) the water recovery rate after the decolorization treatment in the step (3) is 85-96%.

In the invention, 60-85% of organic matters and 7-15% of inorganic salt in the decolored concentrated water gathering colored spun yarn dyeing wastewater; the residue of the decolored concentrated water after evaporation and crystallization can be directly used as hazardous waste for treatment.

As a preferred technical scheme, the process method for zero discharge of the colored spun yarn dyeing wastewater and resource recycling specifically comprises the following steps of:

(1) biochemical treatment: carrying out anaerobic acidification hydrolysis on the dyed yarn dyeing wastewater for 12-24 h, and then carrying out aerobic biochemical treatment for 24-36 h, wherein COD (chemical oxygen demand) in the treated water is less than 200mg/L, and turbidity is less than 10 NTU;

(2) ultrafiltration and reverse osmosis treatment: performing ultrafiltration and reverse osmosis treatment on the wastewater after biochemical treatment, and recycling reverse osmosis filtered clear water for production; the molecular weight cut-off of a membrane element adopted in the ultrafiltration treatment process is 5000-300000D, and ultrafiltration produced water enters reverse osmosis treatment; the pressure of the reverse osmosis treatment is 2.0-4.0 MPa; the pressurizing mode of the reverse osmosis treatment adopts a two-section or three-section inter-section pressurizing design; the water recovery rate of the reverse osmosis treatment is 65-85%;

(3) nanofiltration separation treatment: the reverse osmosis concentrated water enters a nanofiltration system, and a decoloring nanofiltration membrane is used for decoloring; the clear water filtered by the obtained decolorizing nanofiltration membrane is further purified by using a purifying nanofiltration membrane, and the concentrated water obtained by the purifying membrane is decolorized and softened and is used as a dyeing process section to replace anhydrous sodium sulphate for dyeing; the pressure of the decoloring treatment is 1.0-3.0 MPa; the yield of the water produced in the decoloring process is 85-96%; the nanofiltration concentrated water obtained through the decolorization treatment gathers 60-85% of organic matters and 7-15% of inorganic salts in the colored spun yarn dyeing wastewater; evaporating and crystallizing the nanofiltration concentrated water, and treating evaporation residues as hazardous wastes; the salt content in the purified concentrated water is 5-15%; the molecular weight of a membrane element adopted in the decoloring treatment process is 200-1000D; the molecular weight cut-off of a membrane element adopted in the purification treatment process is 100-800D; the working temperature of the decolorizing nanofiltration membrane and the purifying membrane is 10-80 ℃; the decolorizing nanofiltration membrane comprises a roll type or tubular nanofiltration membrane; the decoloring method comprises the steps of decoloring by using powdered activated carbon; the addition amount of the powdered activated carbon for decoloring the powdered activated carbon is 0.1-0.5%.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) the water recovery rate of the method is more than 95 percent, and the sodium sulfate recovery rate is more than 80 percent;

(2) the method has simple process and is easy for industrial application;

(3) the recycled water obtained by the method can be used for boiling, cleaning, dyeing and other processes; and inorganic salts such as sodium sulfate and the like in the extracted wastewater are recycled for the dyeing process, so that water resources and mineral resources are saved, and green production is realized.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

1.1, 1000t of colored spun yarn dyeing wastewater per day is treated by the processes of pH regulation, temperature reduction, homogenization, coagulating sedimentation, hydrolytic acidification, aerobic treatment, secondary sedimentation and the like, and the biochemical effluent indexes are as follows:

TABLE 1.1 Biochemical effluent quality

Contaminants

COD

NH3-N

BOD5

Electrical conductivity of

Color intensity

TDS

Amount of water

Content (wt.)

110mg/l

0.5mg/l

5mg/l

11.8ms/cm

70

0.8％

1000t/d

1.2 the biochemical effluent enters an Ultrafiltration (UF) system after being pretreated by a high-density clarification tank, wherein the UF system adopts an internal MBR membrane or an external column type hollow fiber membrane for filtration, the filtration pressure is 0.2MPa, the yield of the produced water is 90 percent, and the 10 percent concentrated water is returned to a secondary sedimentation tank for treatment and then is continuously subjected to ultrafiltration. The UF water yield is 1000t/d, and the effluent quality indexes are as follows:

TABLE 1.2 Ultrafiltration of the effluent quality

Contaminants

COD

NH3-N

BOD5

Electrical conductivity of

Color intensity

TDS

Amount of water

Content (wt.)

90mg/l

0.5mg/l

4.5mg/l

12.4ms/cm

65

0.8％

1000t/d

1.3UF effluent is concentrated by reverse osmosis

The UF produced water uses a Reverse Osmosis (RO) system, the operating pressure is 2.8MPa, and the yield of the produced water is 73 percent. The reverse osmosis produced water is 730t/d, and the reverse osmosis concentrated water is 270 t/d. The conductivity of the reverse osmosis produced water of 730t/d is 450us/cm, the COD is less than 20mg/l, and the reverse osmosis produced water is used in the whole process flow. The water quality indexes of the reverse osmosis concentrated water at 270t/d are as follows:

TABLE 1.3 quality of reverse osmosis concentrated effluent

Contaminants

COD

NH3-N

BOD5

TDS

Color intensity

PH

Amount of water

Content (wt.)

280mg/l

1.1mg/l

14mg/l

3％

240

7.6

270t/d

And feeding the 270t/d reverse osmosis concentrated water into a decolorizing membrane for further treatment.

1.4 the reverse osmosis concentrated water is decolorized by a decolorizing membrane to remove COD

The 270t/d reverse osmosis concentrated water is decolorized and COD is removed by using a nanofiltration membrane decolorization system, the yield of water produced by a decolorization membrane is 90 percent, the chroma is reduced from 240 times to 8 times, the COD is reduced from 280mg/l of raw water to 55mg/l, and the salt content is 2.7 percent; the COD of the concentrated water of the decolorizing membrane rises to 2300mg/l, and the salt content is 5.7 percent. The water produced by the decolorizing membrane system is 243t/d, and the produced water enters a purifying membrane system for further purification; and (3) carrying out 27t/d on concentrated water of the decolorizing membrane, evaporating the concentrated water by using triple-effect evaporation equipment, and conveying evaporation residues to a hazardous waste treatment plant for treatment, wherein the evaporation residues are hazardous wastes.

1.5 the water produced by the decolorizing membrane enters a purification membrane for purification and is used for dyeing

And (3) treating the 243t/d decolorization membrane produced water in a purification membrane system, wherein the produced water in the purification membrane system is 163t/d, the produced water conductivity is 6500us/cm, the COD is 32mg/l, and the produced water of the front-stage RO are combined together and used in the whole process flow of production dyeing. The concentrated water produced by the purification membrane system is 80t/t, the salt content is 8 percent, the concentrated water is used for the dyeing process after being decolored and softened by active carbon, and when the water is used for dyeing, the auxiliary dye anhydrous sodium sulfate (sodium sulfate) is not needed to be added, so that the using amount of the anhydrous sodium sulfate in the dyeing process is reduced, and the discharge of the anhydrous sodium sulfate to the environment is reduced.

In the whole process, the water reuse rate is 97.3 percent, the salt reuse rate is 80 percent, the treatment cost per ton of water is 8.5 yuan/t, and good economic and social benefits are obtained.

Example 2

2.1 the dyeing wastewater of the colored spun yarn is 500t per day, and the biochemical effluent indexes are as follows after the processes of pH regulation, temperature reduction, homogenization, coagulating sedimentation, hydrolytic acidification, aerobic treatment, secondary sedimentation and the like:

TABLE 2.1 Biochemical effluent quality

Contaminants

COD

NH3-N

BOD5

Electrical conductivity of

Color intensity

TDS

Amount of water

Content (wt.)

100mg/l

0.8mg/l

5mg/l

15.8ms/cm

70

1％

500t/d

2.2 the biochemical effluent enters an Ultrafiltration (UF) system after being pretreated by a high-density clarification tank, wherein the UF system adopts an internal MBR membrane or an external column type hollow fiber membrane for filtration, the filtration pressure is 0.2MPa, the yield of the produced water is 90 percent, and the 10 percent concentrated water is returned to a secondary sedimentation tank for treatment and then is continuously subjected to ultrafiltration. UF water yield is 500t/d, and the quality of the birth water is as follows:

TABLE 2.2 Ultrafiltration of the effluent quality

Contaminants

COD

NH3-N

BOD5

Electrical conductivity of

Color intensity

TDS

Amount of water

Content (wt.)

80mg/l

0.5mg/l

4.5mg/l

15.8ms/cm

65

1％

500t/d

2.3UF effluent was concentrated by reverse osmosis

The UF produced water uses a Reverse Osmosis (RO) system, the operating pressure is 3.5MPa, and the yield of the produced water is 65%. The reverse osmosis produced water is 325t/d, and the reverse osmosis concentrated water is 175 t/d. The conductivity of the reverse osmosis water production is 650us/cm at 325t/d, the COD is less than 20mg/l, and the reverse osmosis water production is used in the whole process flow. The water quality indexes of the reverse osmosis concentrated water at 175t/d are as follows:

TABLE 2.3 quality of reverse osmosis concentrated effluent

Contaminants

COD

NH3-N

BOD5

TDS

Color intensity

PH

Amount of water

Content (wt.)

191mg/l

1.1mg/l

14mg/l

2.8％

180

7.6

175t/d

And (4) feeding the 175t/d reverse osmosis concentrated water into a decolorizing membrane for further treatment.

2.4 the reverse osmosis concentrated water is decolorized by a decolorizing membrane to remove COD

The 175t/d reverse osmosis concentrated water is decolorized and COD is removed by using a nanofiltration membrane decolorization system, the water yield of the decolorization membrane is 95 percent, the chroma of the produced water is reduced to 12 times from 180 times of the water entering the system, the COD is reduced to 40mg/l from 191mg/l, the salt content is 2.6 percent, the water yield of the decolorization membrane system is 166.25t/d, and the produced water enters a purification membrane system for further purification; the COD of the concentrated water of the decolorizing membrane is increased to 3060mg/l, and the salt content is 6.6 percent. The concentrated water of the decolorizing membrane is 8.75t/d, the concentrated water is evaporated by using triple-effect evaporation equipment, and evaporation residues are hazardous wastes and are sent to a hazardous waste treatment plant for treatment.

2.5 the water produced by the decolorizing membrane enters a purification membrane for purification and is used for dyeing

166.25t/d decolorization membrane produced water enters a purification membrane system for treatment, 96.25t/d purification membrane system produced water, the conductivity of the produced water is 4500us/cm, the COD is 30mg/l, and the produced water and the front-stage RO produced water are combined together and used for the whole-stage process flow of production and dyeing. The concentrated water produced by the purification membrane system is 70t/t, the salt content is 6.1%, the concentrated water is used for the dyeing process after being decolored and softened by active carbon, and when the water is used for dyeing, auxiliary dye anhydrous sodium sulfate (sodium sulfate) is not needed to be added, so that the using amount of the anhydrous sodium sulfate in the dyeing process is reduced, and the discharge of the anhydrous sodium sulfate to the environment is reduced.

In the whole process, the water reuse rate is 98.25%, the salt reuse rate is 85.4%, the treatment cost per ton of water is 8.8 yuan/t, and good economic and social benefits are obtained.

The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims (16)

1. A process method for zero discharge of colored spun yarn dyeing wastewater and resource recycling is characterized by comprising the following steps:

(1) carrying out biochemical treatment on the colored spun yarn dyeing wastewater;

(2) performing ultrafiltration and reverse osmosis treatment on the wastewater after biochemical treatment;

(3) the reverse osmosis concentrated water enters a nanofiltration separation system, decolorization is carried out firstly, and residues obtained by evaporating and crystallizing the decolorized concentrated water are treated as hazardous waste; purifying the decolored clear water, decoloring and softening the concentrated water obtained after purification, using the concentrated water in a dyeing process to replace anhydrous sodium sulphate, and combining the purified clear water with reverse osmosis filtered clear water to be used in a full-section production process;

the pressure of the decoloring treatment is 1.0-3.0 MPa, the decoloring treatment is carried out by adopting a decoloring nanofiltration membrane, and the molecular weight cut-off of a membrane element adopted by the decoloring nanofiltration membrane is 200-1000D; the water recovery rate after the decoloring treatment is 85-96%, 60-85% of organic matters and 7-15% of inorganic salts in the concentrated water after the decoloring collection colored spun yarn dyeing wastewater are purified by adopting a purification nanofiltration membrane, the interception molecular weight of a membrane element adopted by the purification nanofiltration membrane is 100-800D, and the salt content of the concentrated water obtained by the purification is 5-15%.

2. The method of claim 1, wherein the biochemical treatment of step (1) comprises anaerobic acidification hydrolysis and aerobic biochemical treatment.

3. The method according to claim 2, wherein the treatment time of anaerobic acidification hydrolysis is 12-24 h.

4. The method of claim 2, wherein the aerobic biochemical treatment is performed for 24-36 hours.

5. The method as claimed in claim 2, wherein the colored spun yarn dyeing wastewater in the step (1) firstly enters an anaerobic acidification hydrolysis tank, the anaerobic standing lasts for 12-24 h, the effluent of the acidification hydrolysis tank enters an aerobic biological tank, and the aerobic tank stays for 24-36 h.

6. The method of claim 5, wherein the effluent COD of the aerobic tank is <200mg/L and the turbidity is <10 NTU.

7. The method of claim 1, wherein the reverse osmosis treatment in the step (2) is performed at a working pressure of 2.0 to 4.0 MPa.

8. The method of claim 7, wherein the reverse osmosis process is pressurized in a two-stage or three-stage interstage pressurization design.

9. The method of claim 1, wherein the ultrafiltration and reverse osmosis processes employ ultrafiltration membrane elements having a molecular weight cut-off of 5000 to 300000D.

10. The method according to claim 1, wherein the operating temperature of the membrane element used for the decolorization treatment is 10 to 80 ℃.

11. The method of claim 1, wherein the decolorizing nanofiltration membrane is a roll-type or tubular nanofiltration membrane.

12. The method of claim 1, wherein the operating temperature of the membrane element adopted by the purification nanofiltration membrane is 10-80 ℃.

13. The method according to claim 1, wherein the concentrated water obtained by purification is decolorized by powdered activated carbon or ozone oxidation.

14. The method of claim 13, wherein the powdered activated carbon is added in an amount of 0.1 to 0.5% for decolorization.

15. The method of claim 1, wherein the water recovery rate after the reverse osmosis treatment in the step (2) is 65-85%.

16. The method of claim 1, wherein the method comprises the steps of:

(1) biochemical treatment: carrying out anaerobic acidification hydrolysis on the dyed yarn dyeing wastewater for 12-24 h, and then carrying out aerobic biochemical treatment for 24-36 h, wherein COD (chemical oxygen demand) in the treated water is less than 200mg/L, and turbidity is less than 10 NTU;

(2) ultrafiltration and reverse osmosis treatment: performing ultrafiltration treatment and reverse osmosis treatment on the wastewater after biochemical treatment, and recycling reverse osmosis filtered clear water for production; the molecular weight cut-off of a membrane element adopted in the ultrafiltration treatment process is 5000-300000D, and ultrafiltration produced water enters reverse osmosis treatment; the pressure of the reverse osmosis treatment is 2.0-4.0 MPa; the pressurizing mode of the reverse osmosis treatment adopts a two-section or three-section inter-section pressurizing design; the water recovery rate of the reverse osmosis treatment is 65-85%;

(3) nanofiltration separation treatment: the reverse osmosis concentrated water enters a nanofiltration system, and a decoloring nanofiltration membrane is used for decoloring; the clear water filtered by the obtained decolorizing nanofiltration membrane is further purified by using a purifying nanofiltration membrane, and the concentrated water obtained by the purifying membrane is decolorized and softened and is used as a dyeing process section to replace anhydrous sodium sulphate for dyeing; the pressure of the decoloring treatment is 1.0-3.0 MPa; the yield of the water produced in the decoloring process is 85-96%; the nanofiltration concentrated water obtained through the decolorization treatment gathers 60-85% of organic matters and 7-15% of inorganic salts in the colored spun yarn dyeing wastewater; evaporating and crystallizing the nanofiltration concentrated water, and treating evaporation residues as hazardous wastes; the salt content in the purified concentrated water is 5-15%; the molecular weight of a membrane element adopted in the decoloring treatment process is 200-1000D; the molecular weight cut-off of a membrane element adopted in the purification treatment process is 100-800D; the working temperature of the decolorizing nanofiltration membrane and the purifying membrane is 10-80 ℃; the decolorizing nanofiltration membrane comprises a roll type or tubular nanofiltration membrane; the decoloring method comprises the steps of decoloring by using powdered activated carbon; the addition amount of the powdered activated carbon for decoloring the powdered activated carbon is 0.1-0.5%.