Printing and dyeing wastewater concentration method and system

Abstract

The invention provides a printing and dyeing wastewater concentration method and system, and the method comprises the steps: carrying out pretreatment on desizing wastewater, so that suspended particles and colloidal impurities in the wastewater are intercepted and adsorbed by a filtering medium; carrying out buffering and flow regulation on the pretreated wastewater, and meanwhile, carrying out heat exchange on hot condensate water generated in the printing and dyeing production process and the pretreated wastewater; raising the temperature of the wastewater to 40 DEG C or above; pressurizing the heated wastewater and then carrying out membrane separation and concentration treatment, forming dialysate by micromolecular substances and part of water, and gradually accumulating intercepted macromolecular substances to form concentrated solution; when the concentration of the concentrated solution reaches the discharge standard, pollutants are treated by adopting a chemical precipitation method and a biological treatment method, or useful substances are recycled. The wastewater concentration process flow is optimized, the wastewater is filtered, intercepted and adsorbed through multiple media, a good water inlet condition is provided for concentration treatment, modified starch and PVA in the wastewater are effectively concentrated, and the follow-up treatment volume and difficulty are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a method and system for concentrating printing and dyeing wastewater. Background Art

[0002] The printing and dyeing industry is a major consumer of industrial water and wastewater. According to incomplete statistics, my country's printing and dyeing wastewater discharges approximately 3 million to 4 million cubic meters per day, accounting for approximately 35% of total industrial wastewater discharge. However, the reuse rate is less than 10%. Printing and dyeing wastewater is characterized by high water consumption, high levels of organic pollutants, high alkalinity, and significant variability in water quality, making it challenging to treat. Currently, there are various methods for treating printing and dyeing wastewater, including physical and chemical methods, biochemical methods, chemical methods, and methods combining several processes. Concentration of printing and dyeing wastewater is a crucial step in these treatment processes. Concentration can reduce the amount of water required for subsequent treatment, improve treatment efficiency, reduce treatment costs, and facilitate the recovery and utilization of useful substances in the wastewater.

[0003] However, the existing printing and dyeing wastewater concentration equipment and processes have some shortcomings: Some wastewater concentration equipment has complex process flow, occupies a large area, and requires a lot of manpower and material resources for management and maintenance; Some wastewater concentration equipment consumes high energy during the concentration process, which increases the operating costs of enterprises; Some wastewater concentration equipment has poor adaptability to wastewater and cannot effectively treat printing and dyeing wastewater of different types and water quality, resulting in poor concentration effect and difficulty in meeting increasingly stringent environmental protection requirements and the actual needs of enterprises. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to design an efficient, energy-saving and highly adaptable printing and dyeing wastewater concentration method and concentration system, optimize the wastewater concentration process, make the wastewater flow from top to bottom through the filter medium layer of different filter materials, effectively treat printing and dyeing wastewater of different types and water quality, improve the adaptability to wastewater treatment, and provide good water inlet conditions for subsequent concentration treatment; buffer the impurities in the wastewater through raw water, and adjust the wastewater flow rate to reduce the impact on subsequent concentration treatment; effectively concentrate the macromolecular substances such as modified starch and PVA in the wastewater through membrane separation and concentration process, thereby reducing the wastewater volume and treatment difficulty of subsequent treatment.

[0005] The present invention provides a method for concentrating printing and dyeing wastewater, comprising the following steps: Pre-treat the desizing wastewater so that the suspended particles and colloidal impurities in the wastewater are intercepted and adsorbed by the filter medium; After pretreatment, the turbidity of the wastewater is significantly reduced and the water quality is preliminarily purified, providing better water inlet conditions for subsequent concentration treatment.

[0006] The pretreated wastewater is buffered and flow-regulated, and hot condensed water (e.g., hot condensed water having a temperature of approximately 60° C.) generated during the printing and dyeing production process is heat exchanged with the pretreated wastewater; during the heat exchange process, the heat of the hot condensed water is transferred to the wastewater, causing the temperature of the wastewater to rise to above 40° C.; After heat exchange, the temperature of the hot condensate can be reduced to around 30°C before subsequent treatment or discharge. Heat exchange raises the wastewater temperature from ambient temperature (approximately 25°C) to over 40°C, improving the efficiency of the subsequent membrane separation process. This increase in temperature helps reduce wastewater viscosity, minimize membrane fouling, and increase membrane flux.

[0007] The heated wastewater is pressurized and then subjected to membrane separation and concentration treatment, whereby the polyvinyl alcohol (PVA) and modified starch macromolecules in the wastewater are retained, and the small molecules in the wastewater and part of the water form a dialysate, which is collected and reused as raw water or further treated according to the water quality; the retained macromolecules gradually accumulate to form a concentrated solution; In a membrane separation system, wastewater passes through an organic membrane at a certain pressure (e.g., 0.5 MPa). Because the organic membrane's molecular weight cutoff is below 10,000, macromolecules such as PVA and modified starch in the wastewater are retained by the membrane, while small molecules and some water pass through the membrane to form dialysate. The dialysate flows through the dialysate outlet into a dialysate collection device for reuse or further treatment depending on the water quality. The retained macromolecules gradually accumulate on the membrane surface, forming a concentrate.

[0008] When the concentration of the concentrated liquid reaches the set discharge standard (such as the PVA concentration reaches 20g / L), chemical precipitation or biological treatment is used to further treat the pollutants in the concentrated liquid, or useful substances in the concentrated liquid (such as PVA) are recycled.

[0009] Preferably, specific chemical agents can be added to precipitate the PVA in the concentrate, and then the PVA precipitate can be separated by filtration or other methods to achieve PVA recovery. The recovered PVA can be used in other industrial production processes, reducing resource waste and reducing the pollution of printing and dyeing wastewater to the environment.

[0010] Furthermore, the method for pretreating desizing wastewater includes: filtering the wastewater with multiple media, using multiple layers of filter media with different filter materials, arranging the filter media in layers according to different particle sizes and densities, and reducing the suspended particle content in the wastewater to below 10 mg / L.

[0011] A variety of filter media are arranged in layers according to different particle sizes and densities, which can effectively remove suspended particles, colloids, organic matter, residual chlorine and other impurities in wastewater. Larger suspended particles are first intercepted by the quartz sand in the upper layer, while smaller particles and colloids are captured by the finer filter media in the lower layer. Activated carbon can absorb some organic matter and pigments in the wastewater, further improving water quality. In one embodiment of the present invention, after multi-media filtration, the suspended particle content in the wastewater is reduced from an initial 100 mg / L to below 10 mg / L, greatly reducing the risk of clogging of subsequent treatment equipment.

[0012] Furthermore, the method of pressurizing the heated wastewater and then performing membrane separation and concentration treatment comprises: According to the liquid level, flow rate and pressure parameters of the heated wastewater in the buffer tank, the pressurization state is accurately adjusted to control the stable operation of the entire membrane separation and concentration process; when the liquid level of the buffer wastewater is lower than the set lower limit, the flow rate of the wastewater transportation is reduced; when the liquid level of the buffer wastewater is higher than the set upper limit, the flow rate of the wastewater transportation is increased to ensure the continuous operation of the membrane separation and concentration.

[0013] During the entire operation process of wastewater concentration, the present invention monitors the parameters of the liquid level, flow rate and pressure of the wastewater (raw water) after buffering and flow adjustment in real time, and controls and adjusts the pressure and flow working state when the raw water is transported to membrane separation and concentration according to these parameters.

[0014] Specifically, when the liquid level in the raw water buffer tank is lower than the set lower limit, the controller issues an instruction to the raw water feed pump to reduce the delivery flow rate; when the liquid level is higher than the set upper limit, the controller controls the raw water feed pump to increase the delivery flow rate to ensure stable operation of the system.

[0015] Furthermore, the membrane separation and concentration treatment method includes: The wastewater is passed through an organic membrane with a cut-off molecular weight below 10,000 Da at a set pressure (such as 0.5 MPa), and the macromolecular substances of PVA and modified starch in the wastewater are retained. The small molecular substances and part of the water pass through the organic membrane to form a dialysate. The retained macromolecular substances gradually accumulate on the surface of the organic membrane to form a concentrated solution. When the concentrated solution reaches the set concentration, the concentrated solution is refluxed and mixed with the raw water.

[0016] As the concentration process progresses, the concentration of PVA and modified starch in the concentrate continues to increase. When the concentrate reaches a certain concentration (for example, the PVA concentration reaches 10g / L), the concentrate is returned to the tank where it mixes with the raw water to further increase its concentration.

[0017] For example, after membrane separation and concentration treatment, the volume of wastewater was reduced by 80%, while the concentration of macromolecular substances such as PVA and modified starch in the concentrated liquid increased by more than 5 times, achieving effective concentration of related substances in printing and dyeing wastewater.

[0018] Furthermore, the dyeing wastewater concentration method further includes: regularly backwashing the filter media used in the multi-media filtration to remove impurities accumulated on the filter media surface and restore filtration performance; and cleaning the organic membrane used in the membrane separation and concentration using a combination of chemical and physical cleaning methods to remove contaminants on the organic membrane surface and extend the membrane's service life.

[0019] For example, the multi-media filter is backwashed once every week of operation; the membrane separation system is chemically cleaned once every month of operation, effectively ensuring the long-term stable operation of the equipment and good concentration effect.

[0020] The present invention also provides a printing and dyeing wastewater concentration system for implementing the printing and dyeing wastewater concentration method as described in any of the above items, comprising: a multi-media filter for removing impurities in wastewater, the multi-media filter comprising multiple filter media layers of different filter materials, the multi-media filter being connected to a raw water buffer tank for buffering and regulating the water volume, and the raw water buffer tank being connected to a membrane separation system for concentrating the wastewater.

[0021] Preferably, the filter medium comprises quartz sand, activated carbon, and anthracite arranged in sequence from top to bottom.

[0022] Printing and dyeing wastewater first enters a multi-media filter, where it flows downward through layers of filter media composed of different filter materials (quartz sand, activated carbon, anthracite, etc.). This filter effectively treats printing and dyeing wastewater of varying types and qualities. Impurities such as suspended particles and colloids in the wastewater are intercepted and adsorbed by the filter media. After multi-media filtration, the wastewater's turbidity is significantly reduced, achieving preliminary purification. This provides optimal inlet conditions for subsequent concentration treatment, reduces the burden on subsequent treatment units, and protects the normal operation of subsequent treatment equipment.

[0023] In one embodiment of the present invention, after multi-media filtration, the suspended particle content in the wastewater is reduced from an initial 100 mg / L to below 10 mg / L, greatly reducing the risk of clogging of subsequent treatment equipment.

[0024] The wastewater that has been filtered through the multi-media system flows into the raw water buffer tank, which plays a role in buffering and regulating the water volume, ensuring the stability of the wastewater flow and pressure entering the membrane separation system. When the wastewater stays in the raw water buffer tank, the sediment, suspended matter and other impurities in the water will naturally settle down, thereby reducing the difficulty and cost of subsequent treatment. The raw water buffer tank can also regulate the wastewater flow to ensure the uniform and stable operation of the subsequent treatment system. After the wastewater passes through the raw water buffer tank, the impact on the entire concentration system will be reduced, which helps to maintain the normal progress of the subsequent treatment. The wastewater in the raw water buffer tank is transported to the membrane separation system, through which part of the modified starch and PVA in the wastewater can be concentrated.

[0025] Furthermore, a heat recovery device is provided around the raw water buffer tank, and hot condensed water generated by the printing and dyeing production is introduced into the heat recovery device.

[0026] Wastewater filtered through the multi-media filter flows into the raw water buffer tank. Heat recovery devices installed around the raw water buffer tank are connected to the external hot condensate from the printing and dyeing process. The hot condensate flows through the heat recovery device, exchanging heat with the wastewater in the raw water buffer tank, thereby heating the wastewater in the raw water buffer tank. This design fully utilizes the waste heat generated during the printing and dyeing process, realizing energy recovery and utilization, saving energy and significantly reducing energy consumption.

[0027] The existing technology directly discharges the hot condensed water generated in the printing and dyeing production process. The present invention transfers the heat of the hot condensed water to the printing and dyeing wastewater in the raw water buffer tank, thereby increasing the temperature of the wastewater. The hot condensed water undergoes heat exchange, and its own temperature is lowered before subsequent treatment or discharge, effectively avoiding heat waste.

[0028] Furthermore, a raw water delivery pump is provided on the communication pipeline between the raw water buffer tank and the membrane separation system, and the raw water delivery pump is electrically connected to a controller.

[0029] The wastewater in the raw water buffer tank is transported to the membrane separation system via a raw water feed pump. A controller controls the operation of the raw water feed pump and other equipment. The controller precisely adjusts the operating status of the raw water feed pump based on parameters such as the raw water buffer tank liquid level, wastewater flow rate, and pressure, achieving automated control and ensuring stable operation throughout the concentration process. When the liquid level in the raw water buffer tank is low, the controller reduces the raw water feed pump flow rate to prevent the pump from running dry. When the liquid level is high, the controller increases the raw water feed pump flow rate to ensure continuous operation of the printing and dyeing wastewater concentration system.

[0030] Furthermore, the membrane separation system includes an organic membrane with a cut-off molecular weight below 10,000 Da, the membrane separation system is provided with a PVA concentrate outlet, the raw water buffer tank includes a second water inlet, and the PVA concentrate outlet is connected to the second water inlet of the raw water buffer tank.

[0031] Wastewater from the raw water buffer tank is transported to the membrane separation system. This membrane separation system utilizes an organic membrane with a molecular weight cutoff below 10,000 Da, effectively retaining macromolecules such as PVA (polyvinyl alcohol) and modified starch in the wastewater. During the membrane separation process, wastewater passes through the organic membrane under pressure. Small molecules and some water permeate the membrane to form a dialysate, which is collected in a dialysate collection device. Macromolecules such as PVA and modified starch are retained on the other side of the membrane, forming a concentrate.

[0032] Through the membrane separation system, part of the modified starch and PVA in the desizing wastewater can be effectively concentrated by at least 10 times. The dialysate does not contain any PVA components, and the concentrated liquid contains a high content of modified starch and PVA and is relatively small in volume, which is convenient for subsequent process treatment.

[0033] After membrane separation, the original large amount of low-concentration printing and dyeing wastewater containing PVA and modified starch is concentrated into a small amount of high-concentration concentrated liquid, greatly reducing the volume and difficulty of subsequent treatment.

[0034] The concentrated liquid produced by the membrane separation system flows back to the second water inlet of the raw water buffer tank through the PVA concentrated liquid outlet, and is mixed with the raw water in the raw water buffer tank to further increase the concentration of substances such as PVA and modified starch in the concentrated liquid.

[0035] Furthermore, the raw water buffer tank is provided with a three-way connecting pipe, which is connected to a concentrate discharge device; the membrane separation system is provided with a dialysate outlet, which is connected to a dialysate collection device.

[0036] When the concentration of PVA, modified starch and other substances in the concentrate in the raw water buffer tank reaches a certain concentration, the concentrate is discharged to the concentrate discharge device through the three-way connecting pipe for subsequent treatment.

[0037] The dialysate produced by the membrane separation system is collected into the dialysate collection device through the dialysate outlet. The dialysate can be further processed or reused according to its water quality.

[0038] Preferably, if the dialysate has good water quality, the dialysate can be directly reused in certain links of the printing and dyeing production process, such as the rinsing process, to achieve the recycling of water resources and reduce the use of fresh water.

[0039] Compared with the prior art, the present invention has the following beneficial effects: The printing and dyeing wastewater concentration method and concentration system provided by the present invention enable the desizing wastewater to directly enter the concentration device after passing through the multi-media filter, without the need for complex pretreatment processes such as dosing, precipitation, and impurity removal, thereby simplifying the process flow. The shorter process flow reduces equipment investment, floor space, and maintenance costs; the multi-media filtration can effectively remove various impurities in the printing and dyeing wastewater, providing relatively stable and high-quality water inlet conditions for subsequent membrane separation and concentration, and can adapt to printing and dyeing wastewater of different water quality and types, thereby improving the versatility and adaptability of the equipment; the macromolecular substances such as PVA and modified starch in the printing and dyeing wastewater are effectively intercepted and concentrated, achieving at least 10 times the volume concentration, which greatly reduces the subsequent treatment The water volume is increased, thus improving the treatment efficiency; the waste heat of the hot condensed water generated in the printing and dyeing production process is transferred to the printing and dyeing wastewater in the raw water buffer tank, realizing the effective recycling of waste heat, saving energy, reducing heat energy loss, and making the recovered heat energy fully meet the energy consumption required for system operation. Compared with traditional concentration equipment that requires external heating or cooling, it greatly reduces energy consumption and reduces the operating costs of the enterprise; through the effective concentration of printing and dyeing wastewater, it is beneficial to the subsequent treatment of pollutants in the wastewater and the recycling of useful substances. The concentrated PVA and modified starch and other substances can be further recycled, reducing resource waste, while reducing the discharge volume of wastewater and reducing pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Various other advantages and benefits will become apparent to those skilled in the art by reading the following detailed description of the preferred embodiment.The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present invention.

[0041] In the attached figure: Figure 1 It is a process flow diagram of a printing and dyeing wastewater concentration system according to an embodiment of the present invention.

[0042] The symbols in the accompanying drawings are: 1. Multi-media filter, 2. Raw water buffer tank, 3. Heat recovery device, 4. Membrane separation system, 5. Dialysate collection device, 6. Concentrate discharge device, 7. Concentrate cleaning device. DETAILED DESCRIPTION

[0043] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present disclosure. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present disclosure, as detailed in the appended claims.

[0044] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. As used in this disclosure and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0045] It should be understood that although the terms first, second, and third may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining."

[0046] Example An embodiment of the present invention provides a method for concentrating printing and dyeing wastewater, comprising: pre-treating desizing wastewater; performing multi-media filtration on the wastewater using multiple layers of filter media composed of different filter materials. The filter media are arranged in layers according to different particle sizes and densities, and comprise, from top to bottom, quartz sand, activated carbon, and anthracite. Suspended particles and colloidal impurities in the wastewater are intercepted and adsorbed by the filter media, reducing the suspended particle content in the wastewater to below 10 mg / L. The multiple filter media are arranged in layers according to different particle sizes and densities, effectively removing suspended particles, colloids, organic matter, residual chlorine, and other impurities from the wastewater. Larger suspended particles are first intercepted by the upper layer of quartz sand, while smaller particles and colloids are captured by the finer filter media in the lower layer. The activated carbon adsorbs some organic matter and pigments in the wastewater, further improving water quality. After multi-media filtration, the suspended particle content in the wastewater is reduced from an initial 100 mg / L to below 10 mg / L, reducing the risk of clogging in subsequent treatment equipment.

[0047] After pretreatment, the wastewater's turbidity is reduced, achieving preliminary purification. The pretreated wastewater is buffered and its flow rate is regulated. Simultaneously, a heat exchange is performed with hot condensate, approximately 60°C, generated during the printing and dyeing process. During the heat exchange, the heat from the hot condensate is transferred to the wastewater, raising its temperature to above 40°C. After the heat exchange, the temperature of the hot condensate drops to approximately 30°C before subsequent treatment or discharge. This heat exchange raises the wastewater temperature from approximately 25°C to above 40°C. This appropriate temperature increase helps reduce wastewater viscosity, minimize membrane fouling, increase membrane flux, and enhance the efficiency of subsequent membrane separation processes.

[0048] Based on the level, flow rate, and pressure parameters of the heated wastewater in the buffer tank, the pressurization state is precisely adjusted to control the stable operation of the entire membrane separation and concentration process. When the buffer wastewater level falls below the set lower limit, the wastewater delivery flow rate is reduced; when the buffer wastewater level rises above the set upper limit, the wastewater delivery flow rate is increased to ensure continuous operation of the membrane separation and concentration process. Throughout the wastewater concentration process, the level, flow rate, and pressure parameters of the buffered and flow-regulated wastewater (raw water) are monitored in real time. Based on these parameters, the pressure and flow rate of the raw water when it is transported to the membrane separation and concentration process are controlled and adjusted.

[0049] The heated wastewater is pressurized to 0.5 MPa and then passed through an organic membrane with a cut-off molecular weight of less than 10,000 Da, intercepting macromolecular substances such as PVA and modified starch in the wastewater, while small molecular substances and part of the water pass through the organic membrane to form a dialysate, which is then collected; the intercepted macromolecular substances gradually accumulate on the surface of the organic membrane to form a concentrate; when the concentration of the concentrate reaches the set emission standard (PVA concentration reaches 20 g / L), chemical precipitation and biological treatment methods are used to further treat the pollutants in the concentrate; for the useful substance polyvinyl alcohol (PVA) in the concentrate, specific chemical agents are added to precipitate the PVA in the concentrate, and then the PVA precipitate is separated by filtration to achieve PVA recovery.

[0050] As the concentration process progresses, the concentration of PVA and modified starch in the concentrate continuously increases. When the PVA concentration reaches 10g / L, the concentrate flows back into the tank containing the raw water, where it mixes with the raw water and the concentration of the concentrate is further increased. After membrane separation and concentration, the wastewater volume is reduced by 80%, while the concentration of macromolecular substances such as PVA and modified starch in the concentrate increases by more than fivefold, effectively concentrating the relevant substances in the printing and dyeing wastewater.

[0051] In this embodiment, the filter medium used in the multi-media filtration is backwashed once every week of operation to remove impurities accumulated on the surface of the filter medium and restore the filtration performance. Once every month of operation, the organic membrane used in membrane separation and concentration is cleaned using a combination of chemical cleaning and physical cleaning to remove pollutants on the surface of the organic membrane, extend the service life of the organic membrane, and ensure long-term stable operation of the equipment and good concentration effect.

[0052] The embodiment of the present invention also provides a printing and dyeing wastewater concentration system for implementing any of the above-mentioned printing and dyeing wastewater concentration methods, such as Figure 1The system shown includes a multi-media filter 1 for removing impurities from wastewater. The multi-media filter 1 comprises multiple filter media layers made of different filter materials. The multi-media filter 1 is connected to a raw water buffer tank 2 for buffering and regulating water volume. This raw water buffer tank 2 is then connected to a membrane separation system 4 for concentrating the wastewater. Dyeing wastewater first enters the multi-media filter 1. Within the filter, the wastewater flows downward through filter media layers made of different filter materials (such as quartz sand, activated carbon, and anthracite). This effectively treats wastewater of varying types and qualities. Impurities such as suspended particles and colloids in the wastewater are intercepted and adsorbed by the filter media. After multi-media filtration, the wastewater's turbidity is significantly reduced, achieving preliminary water purification. This provides optimal inlet conditions for subsequent concentration treatment, reduces the burden on subsequent treatment units, and ensures the normal operation of subsequent treatment equipment. After multi-media filtration, the suspended particle content in the wastewater is reduced from an initial 100 mg / L to below 10 mg / L, significantly reducing the risk of clogging in subsequent treatment equipment. After multi-media filtration, wastewater flows into raw water buffer tank 2, which acts as a buffer and regulates water flow, ensuring a stable flow and pressure for the wastewater entering membrane separation system 4. While the wastewater remains in raw water buffer tank 2, impurities such as silt and suspended matter naturally settle, reducing the difficulty and cost of subsequent treatment. Raw water buffer tank 2 also regulates wastewater flow, ensuring uniform and stable operation of subsequent treatment systems.

[0053] Heat recovery devices 3 are installed around the raw water buffer tank 2, and hot condensed water generated by the printing and dyeing process is introduced into the heat recovery devices 3. Wastewater filtered by the multi-media filter 1 flows into the raw water buffer tank 2. The heat recovery devices 3, installed around the raw water buffer tank 2, are connected to the hot condensed water from the external printing and dyeing process. The hot condensed water flows through the heat recovery devices 3, exchanging heat with the wastewater in the raw water buffer tank 2, thereby heating the wastewater in the raw water buffer tank 2. This fully utilizes the waste heat generated during the printing and dyeing process, realizes energy recovery and utilization, saves energy, and significantly reduces energy consumption.

[0054] A raw water feed pump is installed in the pipeline connecting the raw water buffer tank 2 and the membrane separation system 4. Its electrical signals are connected to a controller. The pump delivers wastewater from the raw water buffer tank 2 to the membrane separation system 4. The controller controls the operation of the raw water feed pump and other equipment. The controller precisely adjusts the operating state of the raw water feed pump based on parameters such as the liquid level in the raw water buffer tank 2, the wastewater flow rate, and pressure, achieving automated control and ensuring stable operation of the entire concentration process. When the liquid level in the raw water buffer tank 2 is low, the controller instructs the raw water feed pump to reduce the delivery rate to prevent the pump from running dry. When the liquid level in the raw water buffer tank 2 falls below a set lower limit, the controller instructs the raw water feed pump to reduce the delivery rate. When the liquid level exceeds a set upper limit, the controller instructs the raw water feed pump to increase the delivery rate to ensure stable system operation. After the wastewater passes through raw water buffer tank 2, the impact on the entire concentration system is reduced, helping to maintain the normal progress of subsequent processing. The wastewater in raw water buffer tank 2 is transported to membrane separation system 4, which contains an organic membrane with a molecular weight cutoff below 10,000 Da. This membrane concentrates some of the modified starch and PVA in the wastewater. During the membrane separation process, the wastewater passes through the organic membrane under pressure. Small molecules and some water pass through the membrane to form a dialysate, which is collected in dialysate collection device 5. Macromolecules such as PVA (polyvinyl alcohol) and modified starch are effectively retained on the other side of the organic membrane, forming a concentrated solution. The membrane separation system 4 effectively concentrates some of the modified starch and PVA in the desizing wastewater by at least 10 times, resulting in a dialysate that contains no PVA. The concentrated solution contains a high content of modified starch and PVA and is relatively small in volume, making it easier to process in subsequent processes.

[0055] Membrane separation system 4 is equipped with a PVA concentrate outlet. Raw water buffer tank 2 includes a second water inlet, and the PVA concentrate outlet is connected to the second water inlet of raw water buffer tank 2. The concentrate produced by membrane separation system 4 flows back through the PVA concentrate outlet to the second water inlet of raw water buffer tank 2, where it mixes with the raw water in raw water buffer tank 2, further increasing the concentration of substances such as PVA and modified starch in the concentrate. After membrane separation, the original large amount of low-concentration printing and dyeing wastewater containing PVA and modified starch is concentrated into a small amount of high-concentration concentrate, reducing the volume and difficulty of subsequent processing.

[0056] The raw water buffer tank 2 is provided with a three-way connecting pipe, which is connected to the concentrate discharge device 6. When the concentration of substances such as PVA and modified starch in the concentrate in the raw water buffer tank 2 reaches a certain concentration, the concentrate is discharged to the concentrate discharge device 6 through the three-way connecting pipe for subsequent treatment. The membrane separation system 4 is provided with a dialysate outlet, which is connected to the dialysate collection device 5. The dialysate produced by the membrane separation system 4 is collected into the dialysate collection device 5 through the dialysate outlet. The dialysate can be further processed or reused according to its water quality. If the dialysate water quality is good, the dialysate can be directly reused in certain links of the printing and dyeing production process, such as the rinsing process, to achieve the recycling of water resources and reduce the use of fresh water.

[0057] In practical applications, the embodiments of the present invention mainly include the following specific processing stages: 1. Wastewater pretreatment: Dyeing wastewater from the printing and dyeing plant is piped into a multi-media filtration system. In multi-media filter 1, the wastewater flows downward through different filter media layers. Impurities such as suspended particles and colloids in the wastewater are intercepted and adsorbed by the filter media. After multi-media filtration, the suspended particle content in the wastewater is reduced to below 10 mg / L. 2. Heat Recovery and Raw Water Buffering Stage: Wastewater filtered through the multi-media filter flows into raw water buffer tank 2. Simultaneously, hot condensate (approximately 60°C) generated during the printing and dyeing process is passed into heat recovery device 3. Within heat recovery device 3, the hot condensate flows around raw water buffer tank 2, exchanging heat with the wastewater within. During the heat exchange process, the heat from the hot condensate is transferred to the wastewater in raw water buffer tank 2, raising the raw water temperature. After the heat exchange, the wastewater temperature in raw water buffer tank 2 rises from ambient temperature (approximately 25°C) to approximately 40°C, while the hot condensate temperature drops to approximately 30°C before being processed or discharged. 3. Membrane Separation and Concentration Stage: The wastewater in raw water buffer tank 2 is pressurized by the raw water feed pump and then transported to membrane separation system 4. In membrane separation system 4, the wastewater passes through an organic membrane at a pressure of 0.5 MPa. When the PVA concentration of the concentrate reaches 10 g / L, it flows back through the PVA concentrate outlet to raw water buffer tank 2, where it mixes with the raw water in raw water buffer tank 2, further increasing the concentration of the concentrate. Treatment in membrane separation system 4 reduces the wastewater volume by 80%, and increases the concentration of macromolecular substances such as PVA and modified starch in the concentrate by more than five times. 4. Concentrate Discharge and Treatment Stage: When the PVA concentration in the concentrate in the raw water buffer tank 2 reaches 20 g / L, the concentrate is discharged to the concentrate discharge device 6 via a three-way connection. The concentrate discharge device 6 transports the concentrate to subsequent processing units, where pollutants in the concentrate are further treated using chemical precipitation, biological treatment, or other methods, and the useful substances (PVA) in the concentrate are recovered and reused. The PVA in the concentrate is precipitated by adding specific chemicals, and the precipitated PVA is separated through filtration and other methods, achieving PVA recovery. 5. Equipment Control and Maintenance Phase: During the operation of the dyeing and printing wastewater progressive concentration equipment, the controller monitors parameters such as the liquid level in the raw water buffer tank 2, the wastewater flow rate, and pressure in real time, and automatically adjusts the operating status of the raw water feed pump based on these parameters. When the liquid level in the raw water buffer tank 2 falls below the set lower limit, the controller instructs the raw water feed pump to reduce the delivery rate; when the liquid level rises above the set upper limit, the controller instructs the raw water feed pump to increase the delivery rate, ensuring stable system operation. Simultaneously, the multi-media filter 1 is regularly backwashed to remove impurities accumulated on the filter media surface and restore filtration performance. The membrane separation system 4 is cleaned using a concentrate cleaning device 7, which uses a combination of chemical and physical cleaning methods to remove contaminants from the membrane surface and extend the membrane's service life.

[0058] The printing and dyeing wastewater concentration method and concentration system of this embodiment allow the desizing wastewater to directly enter the concentration device after passing through the multi-media filter, without the need for complex pretreatment processes such as dosing, precipitation, and impurity removal, thereby simplifying the process flow. The shorter process flow reduces equipment investment, floor space, and maintenance costs; the multi-media filtration can effectively remove various impurities in the printing and dyeing wastewater, providing relatively stable and high-quality water inlet conditions for subsequent membrane separation and concentration, and can adapt to printing and dyeing wastewater of different water quality and types, thereby improving the versatility and adaptability of the equipment; the macromolecular substances such as PVA and modified starch in the printing and dyeing wastewater are effectively intercepted and concentrated, achieving a volume concentration of at least 10 times, which greatly reduces the subsequent treatment The water volume is increased, thus improving the treatment efficiency; the waste heat of the hot condensed water generated in the printing and dyeing production process is transferred to the printing and dyeing wastewater in the raw water buffer tank, realizing the effective recycling of waste heat, saving energy, reducing heat energy loss, and making the recovered heat energy fully meet the energy consumption required for system operation. Compared with traditional concentration equipment that requires external heating or cooling, it greatly reduces energy consumption and reduces the operating costs of the enterprise; through the effective concentration of printing and dyeing wastewater, it is beneficial to the subsequent treatment of pollutants in the wastewater and the recycling of useful substances. The concentrated PVA and modified starch and other substances can be further recycled, reducing resource waste, while reducing the discharge volume of wastewater and reducing pollution to the environment.

[0059] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for concentrating printing and dyeing wastewater, characterized in that: The following steps are involved: Pre-treat the desizing wastewater so that the suspended particles and colloidal impurities in the wastewater are intercepted and adsorbed by the filter medium; Buffering and flow regulating the pretreated wastewater, while heat exchanging the hot condensed water generated in the printing and dyeing production process with the pretreated wastewater; During the heat exchange process, the heat of the hot condensed water is transferred to the wastewater, causing the temperature of the wastewater to rise to above 40°C; The heated wastewater is pressurized and then subjected to membrane separation and concentration treatment, whereby the polyvinyl alcohol (PVA) and modified starch macromolecules in the wastewater are retained, and the small molecules in the wastewater and part of the water form a dialysate, which is collected and reused as raw water or further treated according to the water quality; the retained macromolecules gradually accumulate to form a concentrated solution; When the concentration of the concentrated liquid reaches the set discharge standard, the pollutants in the concentrated liquid are further treated by chemical precipitation or biological treatment, or the useful substances in the concentrated liquid are recycled.

2. The method for concentrating printing and dyeing wastewater according to claim 1, wherein The method for pretreating desizing wastewater includes: performing multi-media filtration on the wastewater, using multiple layers of filter media with different filter materials, arranging the filter media in layers according to different particle sizes and densities, and reducing the suspended particle content in the wastewater to below 10 mg / L.

3. The method for concentrating printing and dyeing wastewater according to claim 1, wherein The method of pressurizing the wastewater after heating and then performing membrane separation and concentration treatment comprises: According to the liquid level, flow rate and pressure parameters of the heated wastewater in the buffer tank, the pressurization state is accurately adjusted to control the stable operation of the entire membrane separation and concentration process; when the liquid level of the buffer wastewater is lower than the set lower limit, the flow rate of the wastewater transportation is reduced; when the liquid level of the buffer wastewater is higher than the set upper limit, the flow rate of the wastewater transportation is increased to ensure the continuous operation of the membrane separation and concentration.

4. The method for concentrating printing and dyeing wastewater according to claim 1, wherein The membrane separation and concentration treatment method comprises: The wastewater is passed through the organic membrane with a cut-off molecular weight of less than 10,000 Da at a set pressure, and the macromolecular substances of PVA and modified starch in the wastewater are retained. The small molecular substances and part of the water pass through the organic membrane to form a dialysate. The retained macromolecular substances gradually accumulate on the surface of the organic membrane to form a concentrated solution. When the concentrated solution reaches the set concentration, the concentrated solution is refluxed and mixed with the raw water.

5. The method for concentrating printing and dyeing wastewater according to claim 2, wherein: Also includes: Regularly backwashing the filter medium used in the multi-media filtration to remove impurities accumulated on the surface of the filter medium and restore the filtration performance; The organic membrane used for membrane separation and concentration is cleaned by combining chemical cleaning and physical cleaning to remove pollutants on the surface of the organic membrane.

6. A printing and dyeing wastewater concentration system, used to implement the printing and dyeing wastewater concentration method according to any one of claims 1 to 5, characterized in that: include: A multi-media filter for removing impurities from wastewater, wherein the multi-media filter comprises multiple filter media layers of different filter materials, the multi-media filter is connected to a raw water buffer tank for buffering and regulating water volume, and the raw water buffer tank is connected to a membrane separation system for concentrating the wastewater.

7. The printing and dyeing wastewater concentration system according to claim 6, characterized in that: Heat recovery devices are provided around the raw water buffer tank, and hot condensed water generated by the printing and dyeing production is introduced into the heat recovery device.

8. The printing and dyeing wastewater concentration system according to claim 6, characterized in that: A raw water delivery pump is provided on the communication pipeline between the raw water buffer tank and the membrane separation system, and the raw water delivery pump is electrically connected to a controller.

9. The printing and dyeing wastewater concentration system according to claim 6, characterized in that: The membrane separation system includes an organic membrane with a cut-off molecular weight below 10,000 Da. The membrane separation system is provided with a PVA concentrate outlet. The raw water buffer tank includes a second water inlet. The PVA concentrate outlet is connected to the second water inlet of the raw water buffer tank.

10. The printing and dyeing wastewater concentration system according to claim 9, characterized in that: The raw water buffer tank is provided with a three-way connecting pipe, and the three-way connecting pipe is connected to a concentrated liquid discharge device; the membrane separation system is provided with a dialysate outlet, and the dialysate outlet is connected to a dialysate collection device.

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