Method for treating printing and dyeing wastewater based on aerobic granular sludge technology

Abstract

The application discloses a method for treating printing and dyeing wastewater based on aerobic granular sludge technology, which comprises the following steps: cultivating and domesticating aerobic granular sludge, adding high-load simulated printing and dyeing wastewater into a sequencing batch reactor with a large height-diameter ratio to start cultivating aerobic granular sludge; treating printing and dyeing wastewater by using the aerobic granular sludge; pre-treating by using an aerated biofilter, starting and forming a membrane by using simulated wastewater; and deeply treating by using a double-membrane process, wherein the effluent is treated by using the double-membrane process, ultrafiltration is carried out by using a high-strength hollow fiber membrane assembly in an external pressure mode, and reverse osmosis is carried out by using an anti-pollution membrane assembly with high anti-pollution property, high desalination rate and high water production capacity; and the effluent quality reaches the quality requirement of textile dyeing and finishing industrial recycled water by adjusting the operation parameters of the double-membrane process.

Description

Technical Field

[0001] This invention relates to the field of textile dyeing and printing wastewater treatment, specifically a method for treating dyeing and printing wastewater based on aerobic granular sludge technology. Background Technology

[0002] With increasingly stringent environmental regulations and rising water prices, the issue of advanced treatment and reuse of dyeing and printing wastewater urgently needs to be addressed. However, dyeing and printing wastewater is characterized by large volume, diverse pollutants, complex composition, high organic pollutant content, poor biodegradability, high alkalinity, high salinity, high color, and large fluctuations in water quality and temperature. It is recognized both domestically and internationally as one of the most complex and difficult-to-treat industrial wastewaters.

[0003] Due to the high COD content (average concentration of approximately 2000 mg / L) and poor biodegradability (B / C ratio less than 0.25) of dyeing and printing wastewater, although anaerobic-aerobic combined technology can treat high-concentration, recalcitrant dyeing and printing wastewater by improving its biodegradability, this technology has a low load and a long process. Furthermore, with increasingly stringent emission standards, traditional anaerobic-aerobic biological methods are gradually failing to meet increasingly stringent environmental protection requirements, especially regarding total nitrogen. Aerobic granular sludge (AGS) is a microbial aggregate that automatically coagulates under high hydraulic shear conditions. Compared to traditional activated sludge processes, it has advantages such as compact structure, fast settling speed, high biomass, and low residual sludge volume, and is considered a potential industrial wastewater treatment technology. Moreover, aerobic granular sludge extends from the outside in, sequentially agglomerating aerobic, facultative anaerobic, and anaerobic microorganisms, enabling simultaneous completion of biological processes such as organic matter degradation, nitrification / denitrification, and biological phosphorus removal, greatly improving pollutant treatment efficiency. Therefore, for dyeing and printing wastewater, aerobic granular sludge technology is a more ideal and efficient biological treatment technology than the traditional anaerobic-aerobic process. The formation of aerobic granular sludge has stringent requirements regarding reactor configuration, hydraulic conditions, and nutrient ratios. However, under traditional cultivation methods, the transformation of sludge from flocculent to granular form takes a long time, typically several months. Dyeing and printing wastewater has a complex composition, containing large amounts of dyes, sizing agents, and auxiliaries. These substances may have toxic effects on microorganisms or interfere with the formation of granular sludge, further increasing the difficulty of cultivation, prolonging the cultivation period, and resulting in slow process start-up, significantly increasing initial construction and time costs. Although aerobic granular sludge can simultaneously carry out multiple biological processes, some recalcitrant organic matter in dyeing and printing wastewater, such as complex azo dyes and polycyclic aromatic hydrocarbons, is still difficult to completely remove. Furthermore, aerobic granular sludge has limited tolerance to some low-concentration but highly toxic pollutants, which may affect microbial activity and thus reduce the overall treatment effect. When treating high-salinity dyeing and printing wastewater, changes in salinity can disrupt the osmotic pressure balance of microbial cells, leading to metabolic disorders and weakening their ability to remove pollutants. The quality and quantity of dyeing and printing wastewater fluctuate significantly; for example, different production batches can result in substantial differences in pollutant concentrations and types, posing a challenge to the stability of aerobic granular sludge systems. Sudden changes in water quality can disrupt the balance of the microbial community within the granular sludge, causing problems such as particle disintegration and sludge bulking. Furthermore, during long-term operation, granular sludge may age, leading to decreased microbial activity and reduced treatment efficiency, requiring frequent adjustments to operating parameters or sludge replacement, increasing the difficulty and cost of operation and management. The effluent from aerobic granular sludge treatment still contains a certain amount of suspended solids, colloidal substances, and dissolved organic matter. Directly introducing this effluent into subsequent advanced treatment processes such as membrane treatment can easily cause membrane fouling, shortening the lifespan of membrane modules and increasing membrane treatment costs.Traditional processes lack effective measures for synergistic optimization of aerobic granular sludge effluent and subsequent processes, making it difficult to fully utilize the efficiency of the entire treatment system.

[0004] While it is technically feasible to use membrane technology to deeply treat dyeing and printing wastewater and directly reuse it in the dyeing and printing process, the current reuse rate of dyeing and printing wastewater is generally low due to factors such as investment costs, operating costs, and land area requirements. Dual-membrane water treatment technology, with ultrafiltration (UF) and reverse osmosis (RO) as the core deep treatment routes, is increasingly being promoted and applied. However, this technology also has drawbacks such as high investment costs (1000-2000 RMB / m2), short membrane module lifespan (2-5 years), high requirements for influent water quality, susceptibility to clogging, and difficulty in cleaning. Currently, technologies such as activated carbon adsorption, coagulation, ozone oxidation, and biological filtration are commonly used for pretreatment of the incoming water to improve influent water quality and mitigate membrane fouling. Biologically aerated filters (BAFs) are a biofilm wastewater treatment technology that integrates biodegradation, physical adsorption, and filtration. While effectively removing COD and SS, they also remove nitrogen and phosphorus, and their operating costs are significantly lower than physicochemical treatment technologies. Therefore, using BAF technology for further treatment of biochemical effluent is of great significance in mitigating membrane fouling, extending membrane module lifespan, and reducing membrane treatment costs. However, the lifespan of membrane modules in current dual-membrane processes is generally short; ultrafiltration membranes typically last 3-5 years, and reverse osmosis membranes only 2-5 years. In the treatment of dyeing and printing wastewater, pollutants in the wastewater easily deposit on the membrane surface, leading to membrane fouling and accelerating the decline in membrane module performance. Frequent replacement of membrane modules not only increases material costs but also generates additional labor maintenance expenses, significantly increasing overall operating costs. Dual-membrane processes have extremely high requirements for influent water quality. If residual suspended solids, colloids, organic matter, microorganisms, and other substances in dyeing and printing wastewater are not effectively removed, they can easily clog membrane pores, causing a decrease in membrane flux and affecting treatment efficiency and effluent quality. Therefore, a rigorous pretreatment process is necessary, increasing the complexity and cost of the treatment process. Even after pretreatment, dyeing and printing wastewater still contains pollutants that are difficult to completely remove, such as recalcitrant organic matter and soluble macromolecules. These substances adsorb and deposit on the membrane surface, forming a stubborn fouling layer. After membrane fouling, conventional physical cleaning methods have limited effectiveness. While chemical cleaning can alleviate fouling, frequent use of chemical agents can damage the membrane material, and the cleaning process is time-consuming and labor-intensive, increasing the difficulty and cost of operation and management.

[0005] Furthermore, the treatment capacity of aerated biological filters is limited by factors such as filter media performance and microbial adhesion. For high-concentration, large-volume dyeing and printing wastewater, exceeding its design treatment load will lead to decreased treatment efficiency and difficulty in meeting effluent quality standards. This is especially true when dealing with large volumes of wastewater generated during peak production periods in dyeing and printing enterprises, where treatment effectiveness is unstable. Suspended solids and colloidal substances in dyeing and printing wastewater easily adhere to the surface and pores of the filter media when passing through the aerated biological filter. Long-term operation can lead to filter media blockage, increasing head loss and affecting water flow. Once the filter media becomes severely blocked, backwashing or even replacement is required, increasing operating and maintenance costs and workload. The growth and metabolism of microorganisms in the aerated biological filter are highly sensitive to environmental conditions such as water quality, water temperature, and dissolved oxygen. Frequent fluctuations in the quality of dyeing and printing wastewater, such as sudden changes in pH value and pollutant concentration, can inhibit microbial activity or even cause microbial death, affecting biodegradation and reducing the ability to remove pollutants. Although aerated biological filters have certain nitrogen and phosphorus removal functions, in actual operation, the nitrogen and phosphorus removal effect fluctuates greatly due to factors such as influent water quality and operating parameters, making it difficult to continuously and stably meet increasingly stringent environmental emission standards. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for treating dyeing and printing wastewater based on aerobic granular sludge technology. This invention shortens the cultivation cycle of aerobic granular sludge through multi-technology synergistic innovation, enhances the pretreatment effect of aerated biological filters, optimizes the anti-fouling performance and operating efficiency of the dual-membrane process, achieves efficient deep treatment and resource recycling of dyeing and printing wastewater, reduces overall treatment costs, and improves the environmental adaptability and economic feasibility of the process.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for treating dyeing and printing wastewater based on aerobic granular sludge technology includes the following steps: Step S1: Cultivation and Acclimation of Aerobic Granular Sludge. A sequencing batch reactor (SBR) with a high aspect ratio (H / D=10) was used. Under room temperature conditions and with the pH controlled at 7.0-7.5, high-load simulated dyeing and printing wastewater with a COD of 2000 mg / L was added to the reactor to begin cultivating aerobic granular sludge. The SBR with an aspect ratio of 10:1 was selected as the core cultivation device. The unique structural design of this reactor effectively promotes the sludge granulation process. Under room temperature conditions, the pH in the reactor was strictly controlled within the slightly alkaline range of 7.0-7.5 to create a suitable acid-base environment for microbial growth. High-load simulated dyeing and printing wastewater with a chemical oxygen demand (COD) concentration of up to 2000 mg / L was injected into the reactor as a substrate for microbial growth and metabolism, officially starting the cultivation of aerobic granular sludge. This high-concentration wastewater not only simulates the pollution characteristics of actual dyeing and printing wastewater but also provides sufficient nutrients for microorganisms, driving their rapid proliferation and gradual formation of granular structures.

[0008] Step S2: Aerobic Granular Sludge Treatment of Dyeing and Printing Wastewater: Well-cultivated and acclimatized aerobic granular sludge is used to treat dyeing and printing wastewater. By adjusting parameters such as organic load, operating cycle, retention time, and sludge age, the optimal process parameters for treating dyeing and printing wastewater with aerobic granular sludge are obtained. The carefully cultivated and acclimatized aerobic granular sludge is then introduced into the wastewater treatment system. To achieve efficient treatment of the dyeing and printing wastewater, several key process parameters are finely adjusted. These parameters include organic load, operating cycle, retention time, and sludge age. By systematically controlling these parameters, the most suitable combination of process parameters for treating dyeing and printing wastewater with aerobic granular sludge is explored and determined, thereby ensuring optimal treatment results.

[0009] Step S3: Bioaerated Filter (BAF) Pretreatment: The BAF is started up and biofilm formation is initiated using simulated wastewater. After the biofilm matures, the effluent from the stable operation of the SBR reactor is used as the BAF influent. Simulated wastewater is used to start up the BAF and initiate biofilm formation. By gradually increasing the influent load, a stable biofilm structure is formed on the filter media surface. Once the biofilm has matured, the effluent from the stable operation of the sequencing batch reactor (SBR) is introduced into the BAF as its influent source. This integrated design achieves efficient synergy between the pretreatment and posttreatment units. The BAF can specifically remove residual pollutants in the SBR effluent, laying a high-quality water foundation for subsequent advanced treatment stages.

[0010] Step S4: Dual-Membrane Deep Treatment: The BAF effluent is treated using a dual-membrane process. Ultrafiltration utilizes high-strength hollow fiber membrane modules, operating under external pressure. Reverse osmosis employs fouling-resistant membrane modules with high desalination rates and high water production. By adjusting the operating parameters of the dual-membrane process, the effluent quality meets the requirements for recycled water in the textile dyeing and finishing industry. The effluent from the biological aerated filter (BAF) is introduced into the dual-membrane process for deep purification. The ultrafiltration stage uses high-strength external pressure hollow fiber membrane modules, utilizing their unique physical retention characteristics to effectively intercept large molecular organic matter, colloids, and microorganisms in the water. The reverse osmosis stage uses specialized membrane modules with excellent fouling resistance, high desalination rates, and high water production to further remove dissolved salts and small molecular pollutants. By finely adjusting the operating parameters of the dual-membrane process, including operating pressure, membrane flux, and cross-flow velocity, deep purification of water quality is achieved, ensuring that the final effluent fully complies with the "Water Quality Standard for Reclaimed Water in Textile Dyeing and Finishing Industry" (FZ / T01107-2011), providing a reliable guarantee for the recycling and reuse of dyeing and finishing wastewater.

[0011] As a further aspect of the present invention, in step S1, during the cultivation of aerobic granular sludge, γ-polyglutamic acid is added as an extracellular polymeric substance (EPS) promoter at a concentration of 5-6 mg / L to enhance the adhesion between microbial cells; a trace element composite additive composed of iron, manganese, zinc, and copper is added at concentrations of 1-1.2 mg / L, 0.5-0.6 mg / L, 0.3-0.4 mg / L, and 0.2-0.3 mg / L, respectively, to activate the activity of microbial metabolic enzymes; a mixed carbon source of sodium acetate and glucose is used, with an initial mass ratio of 3-4:1, which is later adjusted to 1-2:1 for microbial growth and granular structure formation. In the cultivation process of aerobic granular sludge, a multi-enhanced strategy was introduced: γ-polyglutamic acid (PGA) at a concentration of 5-6 mg / L was added as an extracellular polymeric substance (EPS) synergist. Its unique molecular structure significantly enhances the adhesion between microbial cells and accelerates particle aggregation. Simultaneously, a micronutrient composite additive composed of iron, manganese, zinc, and copper was added, with the concentrations of each element precisely controlled at 1-1.2 mg / L, 0.5-0.6 mg / L, 0.3-0.4 mg / L, and 0.2-0.3 mg / L, respectively. This activated the activity of key metabolic enzymes within the microorganisms, improving pollutant degradation efficiency. Furthermore, a dynamic mixed carbon source system of sodium acetate and glucose was used. In the initial stage of cultivation, the mass ratio of the two was set at 3-4:1 to provide sufficient energy for rapid microbial proliferation. As the particles initially formed, the ratio was gradually adjusted to 1-2:1 to optimize carbon source distribution and promote particle densification and stability.

[0012] As a further aspect of this invention, in step S1, the cultivation method is as follows: a combination of pulse aeration and intermittent stirring is used to create alternating aerobic-anoxic microenvironments, promoting microbial aggregation and granulation; the initial cultivation temperature is controlled at 28-29℃ for rapid microbial proliferation; after initial granulation, the temperature is lowered to 25-26℃ to promote EPS secretion; the oxidation-reduction potential (ORP) is adjusted in real time, initially 100-130mV, and during the formation period 50-80mV for microbial metabolism; the acclimation process is as follows: when the granular sludge is initially formed, actual dyeing and printing wastewater is used for acclimation. Specifically, the cultivation method combines pulse aeration with intermittent stirring. Pulsed aeration intermittently provides sufficient dissolved oxygen to the system, while intermittent stirring ensures that dissolved oxygen is evenly distributed throughout the reaction system. The two work synergistically to create alternating aerobic-anoxic microenvironments. This alternating microenvironment not only provides suitable survival conditions for microorganisms with different metabolic types but also promotes interactions between microorganisms, thereby accelerating the aggregation and granulation process.

[0013] Temperature control: In the early stages of cultivation, the temperature is strictly controlled at 28-29℃. This temperature range is conducive to the activity of enzymes within the microorganisms, creating ideal temperature conditions for rapid microbial proliferation. Once the granular sludge has initially formed, the temperature is lowered to 25-26℃. Lower temperatures stimulate the microorganisms to secrete more extracellular polymeric substances (EPS). EPS acts like "glue," enhancing the adhesion between microbial cells and further promoting the stability and perfection of the granular structure.

[0014] Oxidation-reduction potential (ORP) regulation: Precise real-time control of the ORP. In the early stages of cultivation, the ORP is maintained at 100-130 mV. This potential range helps activate the metabolic pathways of microorganisms, providing a suitable redox environment for their growth and reproduction. During the granulation stage, the ORP is adjusted to 50-80 mV. Under this potential condition, the metabolic activities of the microorganisms change accordingly, which is beneficial for the further development and maturation of the granular sludge.

[0015] Acclimation process: Once the initial formation of granular sludge is observed, the influent is promptly switched from simulated dyeing and printing wastewater to actual dyeing and printing wastewater for acclimation. Actual dyeing and printing wastewater has a complex composition; this acclimation method allows the microorganisms in the granular sludge to gradually adapt to the characteristics of the actual wastewater, improving their treatment capacity and adaptability to the actual dyeing and printing wastewater.

[0016] As a further aspect of the present invention, in step S2, the acclimated aerobic granular sludge is used for actual dyeing and printing wastewater treatment, with an organic load of 1.5-1.8 kg COD / (m³). d) The operating cycle is 3.5-4 hours, the retention time is 1.8-2 hours, and the sludge age is 20-22 days. COD, BOD, NH3-N, TN, TP, and color indicators are monitored in real time to analyze pollutant removal patterns and water quality change characteristics. Mature aerobic granular sludge is introduced into the actual dyeing and printing wastewater treatment system. Through precise control of core process parameters, efficient pollutant removal and stable water quality improvement are achieved. The organic loading rate is set at 1.5-1.8 kg COD / (m³). d) This range ensures that microorganisms obtain sufficient metabolic substrates while avoiding the inhibition of sludge activity due to excessive load; the operating cycle is controlled at 3.5-4 hours to ensure that microorganisms complete the entire adsorption and degradation process in an alternating anaerobic and aerobic environment; the retention time is set at 1.8-2 hours to allow sufficient contact and reaction between wastewater and sludge; the sludge age is maintained at 20-22 days to optimize the microbial community structure and ensure system treatment efficiency. During operation, key water quality indicators such as chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammonia nitrogen (NH3-N), total nitrogen (TN), total phosphorus (TP), and color are monitored in real time to deeply analyze the pollutant removal kinetics and dynamically grasp the water quality change trend, providing a scientific basis for process optimization.

[0017] As a further aspect of the present invention, in step S3, the aerated biological filter adopts an upward flow design. The bottom water distribution system consists of perforated pipes and a pebble support layer to ensure uniform water distribution. An adjustable microporous aerator precisely controls the aeration rate. An internal three-stage baffle is installed to form a gradient treatment unit. A composite filler of ceramsite and modified polyurethane sponge is used; the ceramsite provides a surface for microbial attachment, while the modified polyurethane sponge traps suspended solids and optimizes the microbial microenvironment, enhancing the removal capacity of organic matter, color, and suspended solids. The aerated biological filter (BAF) adopts an innovative upward flow design to construct a highly efficient and stable pretreatment system. The bottom water distribution system, composed of perforated pipes and a pebble support layer, ensures uniform wastewater flow through scientific pore size distribution and pebble layer gradation, avoiding short-circuiting and hydraulic dead zones. An adjustable microporous aerator is provided to achieve an aeration rate of 0-10 m³ / (m²). Precise control within the h) range meets the oxygen demand of microorganisms under different water quality conditions. The filter is equipped with three-stage baffles, dividing the treatment space into gradient reaction units. This allows wastewater to undergo enhanced adsorption, biodegradation, and deep interception stages sequentially as it rises, significantly improving pollutant removal efficiency. The filter is filled with a composite packing material of ceramsite and modified polyurethane sponge. Ceramsite, with its rich pore structure and large specific surface area, provides a stable attachment and growth carrier for microorganisms; the modified polyurethane sponge, with its unique three-dimensional network structure, efficiently intercepts suspended solids. Simultaneously, surface modification technology optimizes the microenvironment for microbial survival, synergistically enhancing the removal efficiency of organic matter, color, and suspended solids, ensuring stable effluent quality.

[0018] As a further aspect of the present invention, in step S3, the operating parameters of the aerated biological filter are: during the initial biofilm formation stage, low-load influent, and hydraulic load of 0.5-1.0 m³ / (m²). h), maintain DO at 2-3 mg / L, biofilm formation completes in 15-20 days; during mature operation, adjust retention time and organic load according to influent concentration, low concentration 0.3-0.5 kg COD / (m³) d) Regularly monitor head loss; when it exceeds 1.5m, perform combined air-water backwashing with a water flushing intensity of 8-12 L / (m²). The operating parameters of the aerated biological filter (BAF) are adjusted in real time according to the SBR effluent quality, with a time of 10-15 minutes. An online monitoring device is installed at the BAF effluent outlet to provide feedback data for adjusting the dual-membrane process parameters. The BAF microbial community is analyzed periodically. The BAF operating parameter system follows a scientific and dynamic control strategy: during the initial biofilm formation stage, a low-load influent mode is adopted, strictly controlling the hydraulic load at 0.5-1.0 m³ / (m²). h), simultaneously maintaining dissolved oxygen (DO) concentration at 2-3 mg / L to create a stable environment for microbial attachment and growth, ensuring efficient biofilm formation within 15-20 days. After entering the mature operation phase, the system implements intelligent control based on the influent pollutant concentration: when treating low-concentration wastewater (0.3-0.5 kg COD / (m³)... In step d), the residence time and organic load configuration are dynamically optimized to maintain a balance between treatment efficiency and energy consumption. During operation, the filter head loss is monitored in real time. When this value exceeds 1.5m, the combined air-water backwashing procedure is immediately initiated, with the water flushing intensity set at 8-12 L / (m²). The rinsing time is controlled at 10-15 minutes to effectively remove pollutants trapped on the filter media surface and ensure the filter's permeability. Furthermore, a data linkage mechanism is established between the BAF and pre- and post-treatment units: BAF operating parameters are adjusted in real-time based on the effluent quality of the sequencing batch reactor (SBR) to ensure that the pretreatment effect matches the requirements of subsequent processes; simultaneously, an online monitoring device is deployed at the BAF effluent end to feed water quality data back to the dual-membrane process control system in real time, achieving adaptive optimization of operating parameters in the advanced treatment stage. The system also regularly conducts BAF microbial community structure analysis, providing a biological basis for process parameter optimization and fault early warning through dynamic monitoring of microbial diversity and functional communities.

[0019] As a further aspect of the present invention, in step S4, the ultrafiltration membrane is a high-strength hollow fiber membrane with a zwitterionic polymer antifouling coating, which inhibits pollutant adhesion through electrostatic repulsion and high hydrophilicity; the reverse osmosis membrane is a nanoscale polyamide composite membrane, equipped with an oxidation-reduction potential monitoring and automatic reducing agent injection system to prevent oxidizing substances from damaging the membrane module. In the deep treatment stage of the dual-membrane process, the ultrafiltration unit uses a high-strength hollow fiber membrane module with a surface-loaded zwitterionic polymer antifouling coating. This coating constructs a dual antifouling barrier through electrostatic repulsion and high hydrophilicity: on the one hand, the charge characteristics of zwitterions can repel pollutants with the same charge, reducing their adsorption on the membrane surface; on the other hand, the highly hydrophilic surface allows water molecules to pass through quickly, reducing the probability of contact between pollutants and the membrane surface, effectively inhibiting membrane fouling. The reverse osmosis unit is equipped with a nanoscale polyamide composite membrane, which has excellent desalination performance and water production efficiency. Meanwhile, the system integrates a real-time oxidation-reduction potential (ORP) monitoring and automatic reducing agent injection device. By continuously monitoring the ORP value of the influent, it accurately determines the concentration of oxidizing substances in the water and automatically adds reducing agents according to the set threshold to neutralize strong oxidizing components such as residual chlorine in a timely manner, avoiding irreversible damage to the polyamide membrane structure, thereby significantly extending the service life of the membrane module and ensuring the long-term stable operation of the system.

[0020] The present invention has the following beneficial effects: This invention significantly shortens the cultivation and acclimatization cycle: Through innovative cultivation strategies, the cultivation and acclimatization cycle of aerobic granular sludge is shortened by 30-40% compared to traditional methods, accelerating process start-up and reducing initial construction and time costs. Highly efficient pollutant removal: Multiple technologies work together to achieve highly efficient treatment of dyeing and printing wastewater, with effluent quality meeting the "Water Quality Standard for Reclaimed Water in Textile Dyeing and Finishing Industry" (FZ / T01107-2011), achieving a wastewater reuse rate of 60-70%, improving water resource utilization and reducing water costs for enterprises. Strong resistance to membrane fouling: Optimized pretreatment and innovative dual-membrane processes reduce membrane fouling rate by more than 50%, extending the chemical cleaning cycle from 7-10 days to 30-45 days, extending ultrafiltration membrane life to 5-8 years, and reverse osmosis membrane life to 4-6 years, significantly reducing membrane replacement and maintenance costs. Significantly reduced operating costs: The overall treatment system, through optimized process parameters, reduced sludge production, lower energy consumption, and lower membrane treatment costs, saves 30-40% of treatment costs compared to existing technologies, improving the economic feasibility of the process.

[0021] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the method for treating dyeing and printing wastewater based on aerobic granular sludge technology according to the present invention.

[0023] Figure 2 This is a flowchart of the intelligent control of operating parameters for the dual-membrane process of the present invention. Detailed Implementation

[0024] The present invention will now be further described in conjunction with the accompanying drawings and relevant knowledge, and will be described clearly and completely. Obviously, the described applications are only some embodiments of the present invention, and not all embodiments.

[0025] Existing technologies for treating dyeing and printing wastewater present significant challenges in the industrial wastewater treatment field. This wastewater contains large amounts of pollutants such as dyes, sizing agents, and auxiliaries, exhibiting complex composition, high color, high organic matter concentration, and poor biodegradability. Traditional treatment technologies, such as activated sludge processes and physicochemical methods, suffer from low treatment efficiency, large sludge production, high operating costs, and insufficient deep treatment capacity. While membrane treatment technology can achieve deep water purification, it suffers from severe membrane fouling, short lifespan, and high operation and maintenance costs. Furthermore, the long cultivation cycle of conventional aerobic granular sludge limits its rapid application in practical engineering projects.

[0026] Reference Figures 1-2 As shown, the present invention provides a method for treating dyeing and printing wastewater based on aerobic granular sludge technology, comprising the following steps: Step S1: Cultivation and acclimatization of aerobic granular sludge, reactor and basic conditions: A sequencing batch reactor (SBR) with a large height-to-diameter ratio (H / D=10) is used. Under room temperature conditions, the pH is controlled at 7.0-7.5, and high-load simulated dyeing and printing wastewater with COD of 2000mg / L is added to the reactor. Culture method: Functional additives: γ-polyglutamic acid is added as an extracellular polymeric substance (EPS) promoter at a concentration of 5-6 mg / L to enhance the adhesion between microbial cells; a micronutrient compound additive composed of iron, manganese, zinc, copper, etc., with concentrations of 1-1.2 mg / L, 0.5-0.6 mg / L, 0.3-0.4 mg / L, and 0.2-0.3 mg / L respectively, is added to activate the activity of microbial metabolic enzymes; a mixed carbon source of sodium acetate and glucose is used, with an initial mass ratio of 3-4:1, which is adjusted to 1-2:1 in the later stage to optimize microbial growth and particle structure formation. Further: A combination of pulse aeration (aeration for 5 minutes, aeration stopped for 3 minutes) and intermittent stirring (stirring at 50-80 r / min for 5 minutes, stopping for 10 minutes) is used to create an alternating aerobic-anoxic microenvironment, which promotes microbial aggregation and granulation. Furthermore, precise environmental control is implemented: the initial culture temperature is controlled at 28-29℃ to facilitate rapid microbial proliferation; after the initial formation of particles, the temperature is lowered to 25-26℃ to promote EPS secretion; and the oxidation-reduction potential (ORP) is regulated in real time, initially at 100-130mV and during the formation period at 50-80mV to optimize microbial metabolic pathways.

[0027] In this invention, the acclimation process involves: once the granular sludge is initially formed, it is acclimated using actual dyeing and printing wastewater, continuously optimizing the aforementioned parameters, and shortening the acclimation period. Particle morphology is monitored using optical microscopy and SEM, and indicators such as COD and EPS are detected to assess treatment efficiency and particle stability. Step S2: Aerobic granular sludge treatment of dyeing and printing wastewater: The acclimated aerobic granular sludge is used for actual dyeing and printing wastewater treatment to optimize the organic load (1.5-1.8 kg COD / (m³)). d) Parameters such as operating cycle (3.5-4h), retention time (1.8-2h), and sludge age (20-22 days) are monitored in real time. Indicators such as COD, BOD, NH3-N, TN, TP, and color are analyzed to understand pollutant removal patterns and water quality change characteristics, effectively removing most organic matter, nitrogen, phosphorus, and other pollutants from wastewater. Step S3: Pretreatment in aerated biological filter (BAF); Furthermore, it adopts an upward flow design, with the bottom water distribution system consisting of perforated pipes and a pebble support layer to ensure uniform water distribution; the adjustable microporous aerator precisely controls the aeration rate; and the internal three-stage baffles form a gradient treatment unit to improve pollutant removal efficiency. Further optimization of the filler selection: a composite filler of ceramsite and modified polyurethane sponge (volume ratio 3:2) is adopted. Ceramsite provides a surface for microbial attachment, while modified polyurethane sponge traps suspended solids and optimizes the microbial microenvironment, thereby enhancing the removal capacity of organic matter, color and suspended solids. In this invention: during the biofilm formation initiation stage, the influent is low-load (COD 100-150 mg / L), and the hydraulic load is 0.5-1.0 m³ / (m²). (h), DO maintained at 2-3 mg / L, biofilm formation completed in 15-20 days. During mature operation, adjust the retention time (3-4 h for high concentrations, 1.5-2 h for low concentrations) and organic loading (0.6-0.8 kg COD / (m³) for high concentrations) according to the influent concentration. d) Low concentration 0.3-0.5 kg COD / (m³) d) Regularly monitor head loss, and when it exceeds 1.5m, perform combined air-water backwashing (air flushing intensity 15-20L / (m²)). s), water flushing intensity 8-12L / (m²) (s), time 10-15 min). In this invention, the synergistic enhancement mechanism is as follows: it is linked with the aerobic granular sludge process, and the BAF operating parameters are adjusted in real time according to the SBR effluent quality; an online monitoring device is installed at the BAF effluent end to provide feedback data for regulating the dual-membrane process parameters; the BAF microbial community is analyzed regularly to optimize operating conditions and enhance the overall synergistic treatment effect.

[0028] Specifically, a multi-parameter online monitoring instrument is installed at the SBR effluent outlet to collect data such as COD, ammonia nitrogen, suspended solids (SS), pH, and oxidation-reduction potential (ORP) in real time, establishing a dynamic correlation model between SBR effluent quality and BAF operating parameters. When the SBR effluent COD > 300 mg / L, the system automatically extends the BAF hydraulic retention time to 3-4 hours and increases the aeration rate by 20% to enhance biodegradation efficiency. If the ammonia nitrogen concentration > 20 mg / L, the system increases the dissolved oxygen (DO) concentration in the BAF to 3-4 mg / L and activates the post-denitrification module (by adding a carbon source to supplement electron donors). In addition, based on the SBR effluent SS concentration (> 80 mg / L), the BAF backwashing cycle is automatically adjusted, shortening the conventional 72 hours to 48 hours to prevent filter media clogging.

[0029] Furthermore, an LSTM (Long Short-Term Memory) prediction model was constructed. Inputting water quality fluctuation data, operating parameters, and historical BAF (Body-Aided Freshwater Facility) treatment effects from the previous 12 hours into the SBR, the model predicted the parameters that needed adjustment to the BAF 3 hours in advance. For example, when the model predicted a significant increase in the organic matter concentration in the SBR effluent, the system preemptively increased the organic loading of the BAF to 0.8 kg COD / (m³). d) The mixing ratio of the composite filler was optimized (increasing the proportion of modified polyurethane sponge from 40% to 50%) to enhance the retention capacity of macromolecular pollutants. Simultaneously, by comparing the treatment efficiency data of SBR and BAF, model parameters were automatically calibrated to form a closed-loop optimization system of "monitoring-prediction-control-feedback".

[0030] In this invention, a dual-membrane parameter adjustment system with graded threshold control is implemented. A high-precision online monitoring device is deployed at the BAF effluent outlet, monitoring indicators including COD, turbidity, total iron, total manganese, and microbial metabolites (such as extracellular polymeric substances, EPS). Three threshold levels are set to trigger dual-membrane process adjustments: Level 1 threshold: When BAF effluent turbidity > 3 NTU or COD > 80 mg / L, the system automatically increases the physical backwashing intensity of the ultrafiltration membrane (water flushing intensity from 15 L / (m²)). s) increased to 20L / (m²) The following measures were implemented: First, the chemical cleaning cycle of the reverse osmosis membrane was shortened (from 30 days to 25 days). Secondary threshold: If the total iron / total manganese concentration > 0.5 mg / L, the reducing agent pre-dosing system of the reverse osmosis membrane was immediately activated (sodium bisulfite concentration increased by 30%) to prevent oxidative damage to the membrane by metal oxides. Tertiary threshold: When the EPS concentration abnormally increased (> 10 mg / L), a biological fouling warning for the dual-membrane system was triggered. An ozone pre-oxidation unit was added before ultrafiltration (dosage 0.5-1 mg / L), and the reverse osmosis recovery rate was reduced to 70% to avoid rapid formation of biofouling on the membrane surface. A joint control algorithm for BAF and dual-membrane processes was established, and the optimal combination of operating parameters for the dual-membrane system was calculated in real time based on the BAF effluent quality. For example, when the organic matter concentration in the BAF effluent is low, the operating pressure of the ultrafiltration membrane is automatically reduced to 0.08 MPa to decrease energy consumption. If the BAF effluent contains trace amounts of recalcitrant substances (such as azo dyes), the operating pressure of the reverse osmosis membrane is increased to 2.0 MPa, and the charge density of the zwitterionic polymer coating is adjusted to enhance the retention of charged pollutants. Simultaneously, the dual-membrane system feeds back operating status data (such as membrane flux decay rate and desalination rate changes) to the BAF control system to help optimize the pretreatment intensity of the BAF.

[0031] Step S4: Deep treatment using dual-membrane technology, innovative selection of membrane modules: The ultrafiltration membrane adopts a high-strength hollow fiber membrane with a zwitterionic polymer antifouling coating, which inhibits the adhesion of pollutants through electrostatic repulsion and high hydrophilicity; the reverse osmosis membrane adopts a nano-level polyamide composite membrane with a desalination rate of ≥99.5% and a water production rate increase of 20-30%, and is equipped with an oxidation-reduction potential monitoring and automatic reducing agent injection system to prevent oxidizing substances from damaging the membrane module.

[0032] Intelligent control system: Construct an intelligent control system for operating parameters based on machine learning, collect data such as influent water quality, pressure, and flow rate, use deep neural network models to predict treatment effects, automatically optimize ultrafiltration membrane operating pressure (0.05-0.15MPa), crossflow velocity (0.5-2m / s) and reverse osmosis membrane operating pressure (1.0-2.5MPa), recovery rate (75-85%), predict membrane fouling trends and adjust parameters in advance. Specifically, the dual-membrane process serves as the final stage of deep purification for dyeing and printing wastewater. It consists of two membrane treatment units connected in series: ultrafiltration (UF) and reverse osmosis (RO), forming a gradient purification system of "coarse filtration - fine filtration". The ultrafiltration stage uses external pressure high-strength hollow fiber membrane modules with an inner diameter of 0.8-1.2 mm and a pore size range of 0.01-0.1 μm. It can effectively retain pollutants such as large molecular organic matter, colloids, and bacteria, providing pretreatment assurance for the reverse osmosis membrane. The reverse osmosis stage uses antifouling nano-scale polyamide composite membranes with a membrane element specification of 8 inches × 40 inches. The desalination rate is ≥99.5%, and the water production is increased by 20-30% compared to conventional membranes. It can remove dissolved salts, small molecular organic matter, and heavy metal ions, ensuring that the effluent meets reuse standards.

[0033] Furthermore, the antifouling design incorporates a zwitterionic polymer antifouling coating on the membrane fiber surface. This coating reduces contaminant adsorption through a dual mechanism of electrostatic repulsion (zeta potential maintained at ±20-30mV) and superhydrophilicity (contact angle <30°). A chemically enhanced backwash (CEB) system is also included, performing a weakly alkaline (pH 10-11) or weakly acidic (pH 3-4) chemical cleaning every 2-3 operating cycles to prevent membrane pore blockage. Parameter control is also implemented: operating pressure is maintained at 0.05-0.15MPa, crossflow velocity at 0.8-1.5m / s, and recovery rate at 90-95%. A time-flux dual threshold control strategy is employed; when membrane flux decline exceeds 15% of the initial value or operating time reaches 4 hours, automatic physical backwashing (water flushing intensity 15-20L / (m²)) is initiated. (s), duration 30-60s).

[0034] Further optimization includes intelligent operation, protection, and monitoring of the reverse osmosis membrane system: An integrated online oxidation-reduction potential (ORP) monitor (accuracy ±5mV) and an automatic reducing agent dosing device are used. When the feed water ORP > 200mV, sodium bisulfite solution (concentration 100-300ppm) is added to control the residual chlorine content to <0.1mg / L. Pressure and flow sensors are configured to monitor the membrane element pressure difference in real time (early warning when single membrane pressure drop > 0.15MPa). Operation optimization: The operating pressure is dynamically adjusted according to the feed water salinity (1.2-2.5MPa), and the recovery rate is set at 75-85%. A machine learning-based predictive model is established to predict membrane fouling trends 72 hours in advance by analyzing feed water quality (conductivity, TOC), operating parameters, and historical data, and automatically optimizes the flushing frequency and chemical cleaning scheme.

[0035] In this invention, a linkage mechanism is implemented: ultrafiltration effluent is used as reverse osmosis feed water, and a security filter (5μm precision) is installed between the two membrane stages to prevent large particles from damaging the RO membrane; RO concentrate is returned to the BAF front end for secondary treatment, improving water resource utilization. Water quality compliance control: online monitoring of effluent COD, conductivity, turbidity, ammonia nitrogen, and other indicators. When any parameter approaches the standard limit (e.g., COD > 15mg / L, conductivity > 500μS / cm), automatic adjustment of the dual-membrane system parameters is triggered (e.g., reducing RO recovery rate, increasing ultrafiltration backwash intensity) to ensure stable water quality meeting the requirements of "Water Quality Standard for Reclaimed Water in Textile Dyeing and Finishing Industry" (FZ / T01107-2011).

[0036] Integrated prevention and control of membrane fouling: Physical control uses ultrasonic online cleaning (every 2-4 hours, frequency 20-40kHz, power 50-100W); chemical control uses a composite cleaning agent composed of chelating agents, surfactants and biological enzymes, which intelligently matches the type of fouling for cleaning; biological control is carried out by setting up a biological activated carbon filtration unit before ultrafiltration to degrade trace organic matter and reduce the risk of biofouling. This invention significantly shortens the cultivation and acclimatization cycle: Through innovative cultivation strategies, the cultivation and acclimatization cycle of aerobic granular sludge is shortened by 30-40% compared to traditional methods, accelerating process start-up and reducing initial construction and time costs. Highly efficient pollutant removal: Multiple technologies work together to achieve efficient treatment of dyeing and printing wastewater, with effluent quality meeting the "Water Quality Standard for Reclaimed Water in Textile Dyeing and Finishing Industry" (FZ / T01107-2011), achieving a wastewater reuse rate of 60-70%, improving water resource utilization and reducing water costs for enterprises. Strong resistance to membrane fouling: Optimized pretreatment and innovative dual-membrane processes reduce membrane fouling rate by more than 50%, extending the chemical cleaning cycle from 7-10 days to 30-45 days, extending ultrafiltration membrane life to 5-8 years, and reverse osmosis membrane life to 4-6 years, significantly reducing membrane replacement and maintenance costs. Significantly reduced operating costs: The overall treatment system, through optimized process parameters, reduced sludge production, lower energy consumption, and lower membrane treatment costs, saves 30-40% of treatment costs compared to existing technologies, improving the economic feasibility of the process.

[0037] This invention presents a highly efficient aerobic granular sludge cultivation system. Enhancement factors include the addition of a composite additive of γ-polyglutamic acid and trace elements in a specific ratio. γ-polyglutamic acid strengthens intercellular adhesion, while trace elements activate metabolic enzyme activity. Simultaneously, a dynamically adjusted mixed carbon source is employed. Compared to traditional single-carbon-source or additive-free cultivation methods, this significantly improves the formation rate and stability of granular sludge, shortening the cultivation and acclimatization cycle by 30-40%. Environmental control involves precisely controlling environmental parameters such as temperature and ORP through a combination of pulsed aeration and intermittent stirring. This creates alternating microenvironments and suitable metabolic conditions, breaking the traditional constant cultivation model and providing a more favorable growth environment for microbial aggregation and granulation, promoting rapid granular sludge formation and structural optimization.

[0038] A synergistic and efficient wastewater treatment process combination with multi-stage synergistic treatment: Aerobic granular sludge treatment, aerated biological filter (BAF) pretreatment, and dual-membrane deep treatment are organically combined. Each treatment unit has a clear division of labor yet works synergistically. Aerobic granular sludge efficiently removes most pollutants, BAF further treats residual impurities, and the dual-membrane process achieves deep purification, forming a complete dyeing and printing wastewater treatment chain. Compared to single or simple combined processes, this significantly improves pollutant removal efficiency and effluent quality, with a wastewater reuse rate of 60-70%. Dynamic parameter optimization: Dynamically adjustable operating parameters are set for each treatment stage, and a parameter linkage optimization mechanism is established. Subsequent process parameters are adjusted in real time based on influent water quality and the effects of previous treatments, ensuring the entire treatment system operates at high efficiency and improving process adaptability and stability.

[0039] Advanced membrane fouling control technology: Membrane modules: Ultrafiltration membranes use zwitterionic polymer antifouling coatings, and reverse osmosis membranes use high-performance nano-scale polyamide composite membranes and are equipped with intelligent monitoring and protection systems. From the perspective of membrane materials and structure, the antifouling performance and treatment efficiency of the membranes are improved. Compared with traditional membrane modules, the chemical cleaning cycle is extended by 3-4 times, and the membrane life is greatly improved. The life of ultrafiltration membranes is extended to 5-8 years, and the life of reverse osmosis membranes is extended to 4-6 years.

[0040] The intelligent operation and management mode introduces an intelligent control system based on machine learning to achieve automated and precise control of the operating parameters of the dual-membrane process and prediction of membrane fouling trends. This changes the traditional manual experience-based operation mode, improves the intelligence level of process operation and the reliability of treatment effect, and reduces manual management costs and operational error risks, providing a new path for the intelligent upgrading of dyeing and printing wastewater treatment processes.

[0041] Example 1, a method for treating dyeing and printing wastewater based on aerobic granular sludge technology, includes the following steps: Step S1: Cultivation and Acclimation of Aerobic Granular Sludge: In a high aspect ratio (H / D=10) SBR reactor, under room temperature conditions and with pH controlled at 7.0-7.5, high-load simulated dyeing and printing wastewater with a COD of 2000 mg / L was added. 5 mg / L of γ-polyglutamic acid and a trace element composite additive (1 mg / L iron, 0.5 mg / L manganese, 0.3 mg / L zinc, and 0.2 mg / L copper) were added, using a mixed carbon source of sodium acetate and glucose at a mass ratio of 3:1. Pulsed aeration (5 minutes of aeration followed by 3 minutes of aeration stop) and intermittent stirring (60 r / min for 5 minutes of stirring followed by 10 minutes of stop) were employed. The initial culture temperature was controlled at 28℃, and the ORP was controlled at 120 mV. After 45 days of culture, the initial formation of aerobic granular sludge was observed, with a sludge concentration of 8500 mg / L, a sludge volume index (SVI) of 42 mL / g, and an average sludge particle size of 1.36 mm. Subsequently, actual dyeing and printing wastewater was used for acclimatization. The mass ratio of sodium acetate to glucose was adjusted to 2:1, the temperature was gradually reduced to 26℃, and the ORP dropped to 80mV. After 15 days of acclimatization, the aerobic granular sludge microbial population stabilized, and the COD removal rate reached 85%.

[0042] Step S2: Aerobic granular sludge treatment of dyeing and printing wastewater; The acclimatized aerobic granular sludge was used to treat actual dyeing and printing wastewater, with the organic loading rate adjusted to 1.5 kg COD / (m³). d) The operating cycle is 4 hours, the retention time is 2 hours, and the sludge age is 20 days. After treatment, the COD of the dyeing and printing wastewater decreased from 1200 mg / L to 150 mg / L, BOD decreased from 400 mg / L to 30 mg / L, NH3-N decreased from 50 mg / L to 5 mg / L, TN decreased from 60 mg / L to 15 mg / L, TP decreased from 8 mg / L to 1 mg / L, and the color decreased from 500 times to 50 times.

[0043] Step S3: Pretreatment in an aerated biological filter; The BAF (Balanced Aerated Flood Air) system employs an upward flow design. The bottom water distribution system consists of perforated pipes combined with a pebble support layer. The aeration system utilizes adjustable microporous aerators with internal three-stage baffles. The packing material is a mixture of expanded clay and modified polyurethane sponge at a volume ratio of 3:2. During the start-up phase, the influent COD is 120 mg / L, and the hydraulic load is 0.8 m³ / (m²). (h) DO is maintained at 2.5 mg / L, and biofilm formation is completed in 20 days. After biofilm maturation, the SBR effluent is used as the influent. When the COD of the treated dyeing and printing wastewater is approximately 150 mg / L, the retention time is set to 3 hours, and the organic load is controlled at 0.7 kg COD / (m³). d) Maintain DO at 2-3 mg / L. Regularly monitor the head loss of the filter bed. When the head loss reaches 1.5 m, perform combined air-water backwashing with an air wash intensity of 18 L / (m²). s), water flushing intensity 10L / (m²) The backwashing time was 12 min. The results showed that BAF achieved a 45% removal rate for residual organic matter, a 65% removal rate for color, an 85% removal rate for suspended solids (SS), and a 92% removal rate for turbidity.

[0044] Step S4: Deep processing using a dual-film process; The ultrafiltration membrane uses a high-strength hollow fiber membrane with a zwitterionic polymer antifouling coating, operating at a pressure of 0.1 MPa; the reverse osmosis membrane uses a nano-scale polyamide composite membrane, operating at a pressure of 1.5 MPa. The intelligent control system automatically adjusts operating parameters based on the influent water quality. After 60 days of operation, the membrane flux still maintains 82% of the initial flux, and the effluent water quality meets the requirements for recycled water in the textile dyeing and finishing industry: COD < 20 mg / L, BOD < 5 mg / L, NH3-N < 1 mg / L, TN < 5 mg / L, TP < 0.5 mg / L, color < 10 times, and conductivity < 500 μS / cm.

[0045] Example 2, a method for treating dyeing and printing wastewater based on aerobic granular sludge technology, includes the following steps: Step S1: Cultivation and acclimatization of aerobic granular sludge; In the SBR reactor, the pH was adjusted to 7.2-7.4, and simulated dyeing and printing wastewater was added. γ-polyglutamic acid (6 mg / L) and a trace element composite additive (iron 1.2 mg / L, manganese 0.6 mg / L, zinc 0.4 mg / L, copper 0.3 mg / L) were added, using a mixed carbon source of sodium acetate to glucose at a mass ratio of 4:1. Pulsed aeration (5 minutes aeration, 3 minutes off) and intermittent stirring (70 rpm, 5 minutes stirring, 10 minutes off) were employed. The initial incubation temperature was controlled at 29℃, and the ORP was controlled at 130 mV. After 42 days, granular sludge was formed with a sludge concentration of 8300 mg / L, an SVI of 43 mL / g, and an average sludge particle size of 1.29 mm. The actual dyeing and printing wastewater was used for acclimatization. The mass ratio of sodium acetate to glucose was adjusted to 1:1, the temperature was lowered to 25℃, and the ORP was lowered to 70mV. After 12 days of acclimatization, the microbial population was stable and the COD removal rate reached 88%.

[0046] Step S2: Aerobic granular sludge treatment of dyeing and printing wastewater; Adjust the organic loading rate to 1.8 kg COD / (m³) d) The operating cycle is 3.5 hours, the retention time is 1.8 hours, and the sludge age is 22 days. After treatment, the COD of the dyeing and printing wastewater decreased to 130 mg / L, BOD decreased to 25 mg / L, NH3-N decreased to 4 mg / L, TN decreased to 12 mg / L, TP decreased to 0.8 mg / L, and the color decreased by 40 times.

[0047] Step S3: Pretreatment in an aerated biological filter; The BAF structure and packing are the same as in Example 1. When treating dyeing and printing wastewater with a COD of approximately 100 mg / L, the retention time is set to 2 hours, and the organic load is controlled at 0.4 kg COD / (m³). d) Maintain DO at 2-3 mg / L. When the head loss reaches 1.5 m, perform combined air-water backwashing with an air flushing intensity of 16 L / (m²). s), water flushing intensity 9L / (m²) The backwashing time was 10 minutes. Results showed that BAF achieved a 40% removal rate for residual organic matter, a 60% removal rate for color, an 80% removal rate for suspended solids (SS), and a 90% removal rate for turbidity.

[0048] Step S4: Deep processing using a dual-film process; The ultrafiltration membrane operating pressure was adjusted to 0.12 MPa, and the reverse osmosis membrane operating pressure was 1.6 MPa. After the intelligent control system optimized the parameters, the membrane flux remained at 83% of the initial flux after 80 days of operation, and the effluent quality met the requirements for reuse, further verifying the effectiveness and stability of the process of this invention.

[0049] In this invention, aerobic granular sludge treatment serves as a front-end biological treatment step in the treatment of dyeing and printing wastewater. Leveraging its unique structure and high biological activity, it can efficiently remove most organic matter, nitrogen, and phosphorus pollutants from the wastewater. During the treatment process, by optimizing operating parameters, aerobic granular sludge can significantly reduce COD, BOD, NH3-N, TN, and TP in the wastewater. However, due to the complex composition of dyeing and printing wastewater, some recalcitrant organic matter, color, SS, and turbidity pollutants still remain in the treated wastewater. At this point, an aerated biological filter (BAF) is introduced as a pretreatment step, using the effluent from the aerobic granular sludge treatment as the influent. The filter media in the BAF is covered with a large number of microorganisms, which can further degrade residual organic matter. Simultaneously, the filter media effectively removes SS and turbidity, and reduces wastewater color through a combination of biological and physical processes. Aerobic granular sludge treatment reduces the treatment load on the BAF, allowing the BAF to focus more on treating residual pollutants; while the BAF "fills the gaps" in the wastewater after aerobic granular sludge treatment. The two work together to create more favorable influent conditions for the subsequent dual-membrane process, effectively improving the overall treatment system's pollutant removal efficiency.

[0050] Aerated biological filters, as a pretreatment technology in dual-membrane processes, play a crucial role in mitigating membrane fouling and extending the lifespan of membrane modules. While ultrafiltration and reverse osmosis membrane modules in dual-membrane processes can achieve deep purification of wastewater, membrane fouling remains a key factor restricting their efficient operation.

[0051] By removing residual organic matter, suspended solids (SS), and turbidity from wastewater, BAF reduces the deposition and adsorption of these substances on the membrane surface, thus lowering the likelihood of membrane fouling at its source. Simultaneously, BAF pretreatment of wastewater makes the water quality entering the dual-membrane process more stable, reducing the treatment pressure on the dual-membrane process. This allows the dual-membrane process to adjust operating parameters to achieve efficient and advanced wastewater treatment, ensuring that the effluent meets the water quality requirements for reuse in the textile dyeing and finishing industry.

[0052] Furthermore, although aerobic granular sludge treatment and the dual-membrane deep treatment process are not directly connected, they achieve indirect synergy through the intermediate step of an aerated biological filter (BAF). Aerobic granular sludge treatment provides preliminary purification of the dyeing and printing wastewater, significantly reducing pollutant concentrations and alleviating the treatment burden on the subsequent BAF and dual-membrane processes. The dual-membrane process, as the final stage of the treatment process, provides deep purification of the wastewater after the first two stages, ensuring that the final effluent meets reuse standards. The stringent requirements of the dual-membrane process for the treated water quality also drive the continuous optimization of aerobic granular sludge treatment and BAF pretreatment to meet their influent requirements. These three processes influence and promote each other, jointly ensuring the high efficiency and stability of dyeing and printing wastewater treatment.

[0053] The technical principles of the present invention have been described above with reference to specific embodiments, which are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments; all technical solutions falling within the scope of the present invention's concept are within its protection scope. Those skilled in the art can conceive of other specific embodiments of the present invention without creative effort, and these embodiments will all fall within the protection scope of the present invention.

Claims

1. A method for treating dyeing and printing wastewater based on aerobic granular sludge technology, characterized in that, Includes the following steps: Step S1: Cultivation and acclimatization of aerobic granular sludge. A sequencing batch reactor (SBR) with a large aspect ratio was used. Under room temperature conditions and with the pH controlled at 7.0-7.5, high-load simulated dyeing and printing wastewater with a COD of 2000 mg / L was added to the SBR to begin cultivating aerobic granular sludge. During the cultivation of aerobic granular sludge, γ-polyglutamic acid was added as an extracellular polymeric agent at a concentration of 5-6 mg / L to enhance the adhesion between microbial cells. A micronutrient composite additive composed of iron, manganese, zinc, and copper was added at concentrations of 1-1.2 mg / L, 0.5-0.6 mg / L, 0.3-0.4 mg / L, and 0.2-0.3 mg / L, respectively, to activate the activity of microbial metabolic enzymes. A mixed carbon source of sodium acetate and glucose was used, with an initial mass ratio of 3-4:1, which was later adjusted to 1-2:1 for microbial growth and granular structure formation. Step S2: Aerobic granular sludge treatment of dyeing and printing wastewater: The cultivated and acclimated aerobic granular sludge is used to treat dyeing and printing wastewater. By adjusting the organic load, operating cycle, retention time and sludge age parameters, the process parameters for treating dyeing and printing wastewater with aerobic granular sludge are obtained. The acclimated aerobic granular sludge is used for actual dyeing and printing wastewater treatment. The organic load is 1.5-1.8 kgCOD / (m³d), the operating cycle is 3.5-4 h, the retention time is 1.8-2 h, and the sludge age is 20-22 days. COD, BOD, NH3-N, TN, TP and color index are monitored in real time to analyze the pollutant removal pattern and water quality change characteristics. Step S3: Pretreatment of the Aerated Biological Filter: The aerated biological filter is started up and the biofilm forms using simulated wastewater. After the biofilm matures, the effluent from the stable operation of the sequencing batch reactor (SBR) is used as the influent to the aerated biological filter. A dynamic correlation model is established between the effluent quality of the SBR and the operating parameters of the aerated biological filter. An LSTM prediction model is constructed, inputting the water quality fluctuation data, operating parameters, and historical treatment effects of the SBR over the previous 12 hours. The parameters that need to be adjusted in the aerated biological filter are predicted 3 hours in advance, and the dual-membrane parameters are adjusted through graded threshold control. A high-precision online monitoring device is deployed at the effluent outlet of the aerated biological filter, and three levels of thresholds are set to trigger the adjustment of the dual-membrane process: Level 1 threshold: When the turbidity of the aerated biological filter effluent is >3 NTU or CO2 > 3 NTU. When D > 80 mg / L, the system automatically enhances the physical backwashing intensity of the ultrafiltration membrane and shortens the chemical cleaning cycle of the reverse osmosis membrane; Secondary threshold: If the total iron / total manganese concentration > 0.5 mg / L, the reducing agent pre-dosing system of the reverse osmosis membrane is immediately activated to prevent oxidative damage to the membrane by metal oxides; Tertiary threshold: When the EPS concentration rises abnormally, the biological fouling warning of the dual-membrane system is triggered, and an ozone pre-oxidation unit is added before ultrafiltration. The operating parameters of the aerated biological filter are as follows: During the initial biofilm formation stage, low-load influent, hydraulic load 0.5-1.0 m³ / (m²h), DO maintained at 2-3 mg / L, biofilm formation completed in 15-20 days; During mature operation, the retention time and organic load are adjusted according to the influent concentration, with the high concentration of organic load being 0.6-0.8 kg COD / (m³h). d) Low concentration of 0.3-0.5 kg COD / (m³) d) Regularly monitor head loss; when it exceeds 1.5m, perform combined air-water backwashing. The parameters for the combined air-water backwashing are: air flushing intensity 15-20 L / (m²). s), water flushing intensity 8-12L / (m²) (s), time 10-15 min; An online monitoring device is installed at the effluent end of the aerated biological filter to provide feedback data for adjusting the dual-membrane process parameters; the microbial community of the aerated biological filter is analyzed regularly. Step S4: Dual-membrane deep treatment: The effluent from the aerated biological filter is treated using a dual-membrane process. The ultrafiltration uses a high-strength hollow fiber membrane module and operates under external pressure. The reverse osmosis uses a fouling-resistant membrane module with high desalination rate and high water production. By adjusting the operating parameters of the dual-membrane process, the effluent quality meets the requirements for recycled water in the textile dyeing and finishing industry.

2. The method for treating dyeing and printing wastewater based on aerobic granular sludge technology as described in claim 1, characterized in that, In step S1, the cultivation method is as follows: pulse aeration combined with intermittent stirring is used to generate alternating aerobic-anoxic microenvironments to promote microbial aggregation and granulation; the initial cultivation temperature is controlled at 28-29℃ for rapid microbial proliferation; after the initial formation of granules, the temperature is lowered to 25-26℃ to promote EPS secretion; the oxidation-reduction potential is adjusted in real time, initially 100-130mV, and during the formation period 50-80mV for microbial metabolism; the acclimatization process is as follows: when the granular sludge is initially formed, it is acclimatized with actual dyeing and printing wastewater.

3. The method for treating dyeing and printing wastewater based on aerobic granular sludge technology as described in claim 2, characterized in that, In step S3, the aerated biological filter adopts an upward flow design, and the bottom water distribution system consists of perforated pipes and a pebble support layer to ensure uniform water distribution; the adjustable microporous aerator precisely controls the aeration rate; a three-stage baffle is set inside to form a gradient treatment unit; and a composite filler of ceramsite and modified polyurethane sponge is used. Ceramsite provides a surface for microbial attachment, while modified polyurethane sponge intercepts suspended solids and optimizes the microbial microenvironment, enhancing the removal capacity of organic matter, color, and suspended solids.

4. The method for treating dyeing and printing wastewater based on aerobic granular sludge technology as described in claim 3, characterized in that, In step S4, the ultrafiltration membrane is a high-strength hollow fiber membrane with a zwitterionic polymer antifouling coating, which inhibits the adhesion of pollutants through electrostatic repulsion and high hydrophilicity; the reverse osmosis membrane is a nano-scale polyamide composite membrane, equipped with an oxidation-reduction potential monitoring and automatic reducing agent injection system to prevent oxidizing substances from damaging the membrane module.

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