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

Abstract

The invention discloses a method for treating printing and dyeing wastewater based on an aerobic granular sludge technology, which comprises the following steps: culturing and domesticating aerobic granular sludge: adopting a sequencing batch activated sludge reactor with a large height-diameter ratio, adding high-load simulated printing and dyeing wastewater into the reactor, and starting to culture the aerobic granular sludge; treating the printing and dyeing wastewater by using the aerobic granular sludge: treating the printing and dyeing wastewater by using the cultured and domesticated aerobic granular sludge; carrying out biological aerated filter pretreatment: carrying out starting and biofilm formation by adopting simulated wastewater; advanced treatment with a double-membrane process: treating the effluent with the double-membrane process, wherein ultrafiltration adopts a high-strength hollow fiber membrane module, and the operation mode is an external pressure mode; an anti-pollution membrane assembly with pollution resistance, high desalination rate and high water yield is adopted for reverse osmosis, and by adjusting operation parameters of a double-membrane process, the effluent quality meets the water quality requirement of recycled water in the textile dyeing and finishing industry.

Description

Technical Field

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

[0002] With the increasingly strict environmental regulations and the continuous rise of water prices, the problem of advanced treatment and recycling of printing and dyeing wastewater needs to be solved urgently. However, printing and dyeing wastewater has the characteristics of large water volume, many types of pollutants, complex wastewater composition, high content of organic pollutants, poor biodegradability, high alkalinity, high salinity, high chroma, and large changes in water quality and water temperature. It is one of the industrial wastewaters with complex composition and the most difficult to treat recognized at home and abroad.

[0003] Due to the high COD content of printing and dyeing wastewater (average concentration about 2000 mg / L) and poor biodegradability (B / C value less than 0.25), although the anaerobic-aerobic combined technology can treat high-concentration and refractory printing and dyeing wastewater by improving the biodegradability of the wastewater, this technology has a low load, a long process, and with the continuous improvement of emission standards, the traditional anaerobic-aerobic biological method has gradually been unable to meet the increasingly stringent environmental protection requirements, especially for the requirement of total nitrogen. Aerobic granular sludge (AGS) is a microbial aggregate that automatically coagulates under high hydraulic shear conditions. Compared with the traditional activated sludge method, it has the advantages of a compact structure, a fast sedimentation rate, a high biomass, and a small amount of excess sludge, and is considered a potential industrial wastewater treatment technology. In addition, aerobic granular sludge grows aggregately in sequence from the outside to the inside with aerobic, facultative anaerobic, and anaerobic microorganisms, and can simultaneously complete biological processes such as organic matter degradation, nitrification and denitrification, and biological phosphorus removal, greatly improving the treatment efficiency of pollutants. Therefore, for printing and dyeing wastewater, the aerobic granular sludge technology is a more ideal and efficient wastewater biological treatment technology than the traditional anaerobic-aerobic method. The formation of aerobic granular sludge has strict requirements for reactor configuration, hydraulic conditions, nutrient ratio, etc. However, under the traditional cultivation method, it takes a long time to realize the transformation of sludge from flocculent to granular, and the cultivation period is usually as long as several months. The composition of printing and dyeing wastewater is complex, containing a large number of substances such as dyes, sizing agents, and auxiliaries. These substances may have a toxic effect on microorganisms or interfere with the formation process of granular sludge, further increasing the cultivation difficulty and prolonging the cultivation period, resulting in a slow start of the process and a significant increase in the upfront construction cost and time cost. Although aerobic granular sludge can carry out multiple biological processes simultaneously, some refractory organic matters in printing and dyeing wastewater, such as azo dyes and polycyclic aromatic hydrocarbons with complex structures, are still difficult to be completely removed. In addition, for some pollutants with low concentration but strong toxicity, the tolerance of aerobic granular sludge is limited, which may affect the microbial activity and thus reduce the overall treatment effect. When treating high-salinity printing and dyeing wastewater, the change in salinity will affect the osmotic pressure balance of microbial cells, leading to microbial metabolic disorders and weakening its ability to remove pollutants. The water quality and quantity of printing and dyeing wastewater fluctuate greatly. For example, different production batches result in obvious differences in the concentration and type of pollutants in the wastewater, which poses a challenge to the stability of the aerobic granular sludge system. The sudden change in water quality may break the balance of the microbial community inside the granular sludge, causing problems such as granular disintegration and sludge bulking. At the same time, during the long-term operation process, the granular sludge may age, the microbial activity decreases, and the treatment efficiency reduces, requiring frequent adjustment of operation parameters or sludge renewal, increasing the operation management difficulty and cost. The effluent after treatment by aerobic granular sludge still contains a certain amount of suspended solids, colloidal substances, and dissolved organic matter. If it directly enters subsequent advanced treatment processes such as membrane treatment, it is easy to cause membrane fouling, shorten the service life of the membrane module, and increase the membrane treatment cost.In traditional processes, there are no effective measures to synergistically optimize the effluent of aerobic granular sludge and subsequent processes, making it difficult to fully exert the efficiency of the entire treatment system.

[0004] It is technically feasible to directly reuse the dyeing wastewater after advanced treatment using membrane technology in the dyeing process. However, restricted by many factors such as investment costs, operating costs, and floor area, the current reuse rate of dyeing wastewater is generally not high. The dual-membrane water treatment technology with ultrafiltration (UF) and reverse osmosis (RO) as the core advanced treatment routes has been increasingly promoted and applied. However, this technology also has deficiencies such as high investment costs (1000 - 2000 yuan / m²), short membrane module lifespan (2 - 5 years), high requirements for influent water quality, easy blockage, and difficult cleaning. Currently, technologies such as activated carbon adsorption, coagulation, ozone oxidation, and biological filtration are usually used to pretreat the influent water to improve the influent water quality and mitigate membrane fouling. The biological aerated filter (BAF), a biological membrane wastewater treatment technology integrating functions such as biodegradation, physical adsorption, and filtration, not only effectively removes COD and SS but also has the function of nitrogen and phosphorus removal, and its operating cost is much lower than that of physicochemical treatment technologies. Therefore, using the BAF process to further treat the biochemical effluent is of great significance for mitigating membrane fouling, increasing the lifespan of membrane modules, and reducing membrane treatment costs. However, currently, the service life of membrane modules in the dual-membrane process is generally short. The ultrafiltration membrane usually lasts for 3 - 5 years, and the reverse osmosis membrane only lasts for 2 - 5 years. During the treatment of dyeing wastewater, pollutants in the wastewater are extremely easy to deposit on the membrane surface, resulting in membrane fouling and accelerating the decline in the performance of membrane modules. Frequent replacement of membrane modules not only increases the material cost but also generates additional labor maintenance costs, significantly increasing the overall operating cost. The dual-membrane process has extremely high requirements for influent water quality. Substances such as suspended solids, colloids, organic matter, and microorganisms remaining in the dyeing wastewater, if not effectively removed, are extremely easy to block the membrane pores, causing a decrease in membrane flux and affecting the treatment efficiency and effluent water quality. Therefore, a strict pretreatment process must be equipped, increasing the complexity and cost of the treatment process. Even after pretreatment, there are still pollutants in the dyeing wastewater that are difficult to completely remove, such as refractory organic matter and dissolved macromolecular substances. These substances adsorb and deposit on the membrane surface, forming a stubborn pollution layer. After membrane fouling, the effect of conventional physical cleaning methods is limited. Although chemical cleaning can alleviate fouling, frequent use of chemical agents will damage the membrane material, and the cleaning process is time-consuming and laborious, increasing the operation and management difficulty and cost.

[0005] In addition, the treatment capacity of the biological aerated filter is restricted by factors such as the performance of the filter media and the amount of attached microorganisms. For high-concentration and large-volume printing and dyeing wastewater, if it exceeds its designed treatment load, the treatment efficiency will decline, and it will be difficult to meet the effluent quality standards. Especially in the face of a large amount of wastewater generated during the peak production period of printing and dyeing enterprises, the treatment effect is unstable. Suspended solids and colloidal substances in printing and dyeing wastewater are likely to adhere to the surface and pores of the filter media when passing through the biological aerated filter. Long-term operation will lead to filter media blockage, increase the head loss, and affect the water flow throughability. Once the filter media is severely blocked, backwashing or even replacement of the filter media is required, increasing the operation and maintenance costs and workload. The growth and metabolism of microorganisms in the biological aerated filter are relatively sensitive to environmental conditions such as water quality, water temperature, and dissolved oxygen. The water quality of printing and dyeing wastewater fluctuates frequently. For example, sudden changes in pH value and pollutant concentration will inhibit the activity of microorganisms, even cause the death of microorganisms, affect the biodegradation effect, and reduce the removal ability of pollutants. Although the biological aerated filter has a certain denitrification and phosphorus removal function, in actual operation, affected by factors such as influent water quality and operation parameters, the denitrification and phosphorus removal effects fluctuate greatly and it is difficult to continuously and stably meet the increasingly strict environmental protection discharge standards. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention provides a method for treating printing and dyeing wastewater based on the aerobic granular sludge technology. Through multi-technology collaborative innovation, the present invention shortens the cultivation period of aerobic granular sludge, strengthens the pretreatment effect of the biological aerated filter, optimizes the anti-pollution performance and operation efficiency of the dual-membrane process, realizes the high-efficiency and in-depth treatment and resource recycling of printing and dyeing wastewater, reduces the overall treatment cost, and improves the environmental adaptability and economic feasibility of the process.

[0007] To achieve the above object, the present invention provides the following technical solutions: A method for treating printing and dyeing wastewater based on the aerobic granular sludge technology, comprising the following steps: Step S1: Cultivation and domestication of aerobic granular sludge. 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. A high-load simulated printing and dyeing wastewater with a COD of 2000 mg / L is added to the reactor to start cultivating aerobic granular sludge. A sequencing batch reactor (SBR) with a height-to-diameter ratio of 10:1 is selected as the core cultivation device. The unique structural design of this reactor can effectively promote the process of sludge granulation. Under room temperature conditions, the pH in the reactor is strictly controlled in the weak alkaline range of 7.0 - 7.5 to create a suitable acid-base environment for the growth of microorganisms. A high-load simulated printing and dyeing wastewater with a chemical oxygen demand (COD) concentration as high as 2000 mg / L is injected into the reactor as the substrate for the growth and metabolism of microorganisms, and the cultivation of aerobic granular sludge is officially started. This high-concentration wastewater not only simulates the pollution characteristics of actual printing and dyeing wastewater but also provides sufficient nutrient sources for microorganisms, driving their rapid proliferation and gradually forming a granular structure.

[0008] Step S2: Treatment of printing and dyeing wastewater with aerobic granular sludge. The cultivated and domesticated aerobic granular sludge is used to treat printing and dyeing wastewater. By adjusting process parameters such as organic load, operation cycle, retention time, and sludge age, the process parameters for treating printing and dyeing wastewater with aerobic granular sludge are obtained. The carefully cultivated and domesticated aerobic granular sludge is put into the printing and dyeing wastewater treatment system. To achieve efficient treatment of printing and dyeing wastewater, multiple key process parameters are finely adjusted. These parameters include organic load, operation cycle, retention time, and sludge age. By systematically regulating these parameters, the optimal combination of process parameters for treating printing and dyeing wastewater with aerobic granular sludge is explored and determined to ensure that the treatment effect reaches the optimal level.

[0009] Step S3: Pretreatment of biological aerated filter (BAF). The BAF is started and biofilm is formed using simulated wastewater. After the biofilm is mature, the effluent from the SBR reactor during stable operation is used as the influent of the BAF. The biological aerated filter (BAF) is started and biofilm is formed using simulated wastewater. By gradually increasing the influent load, microorganisms are induced to form a stable biofilm structure on the filter media surface. After the biofilm is mature, the effluent from the sequencing batch reactor (SBR) during stable operation is introduced into the BAF as its influent water source. This connection design enables the efficient coordination of the front and back treatment units. The BAF can specifically remove the residual pollutants in the SBR effluent, laying a high-quality water quality foundation for the subsequent advanced treatment stage.

[0010] Step S4: Advanced treatment by dual-membrane process: Treat the effluent from BAF by the dual-membrane process. Among them, ultrafiltration uses high-strength hollow fiber membrane modules, and the operation mode is external pressure type; reverse osmosis uses anti-fouling membrane modules with anti-fouling property, high salt rejection rate and high water production rate. By adjusting the operation parameters of the dual-membrane process, the effluent quality meets the requirements of the reclaimed water quality for textile dyeing and finishing industry. Introduce the effluent from the biological aerated filter (BAF) into the dual-membrane process for advanced purification treatment. The ultrafiltration stage uses high-strength external pressure type hollow fiber membrane modules, which utilize their unique physical interception characteristics to effectively intercept macromolecular organic matters, colloids and microorganisms in water; the reverse osmosis stage selects special membrane modules with excellent anti-fouling performance, high salt rejection rate and high water production rate to further remove dissolved salts and small molecular pollutants. By finely adjusting the operation parameters of the dual-membrane process, including operating pressure, membrane flux, cross-flow velocity, etc., achieve advanced purification of water quality, ensure that the final effluent fully meets the standard of "Reclaimed Water Quality for Textile Dyeing and Finishing Industry" (FZ / T01107-2011), and provide a reliable guarantee for the recycling of printing and dyeing wastewater.

[0011] As a further solution of the present invention, in step S1, during the cultivation of aerobic granular sludge, add γ-polyglutamic acid as an extracellular polymer (EPS) promoter with a concentration of 5-6 mg / L to enhance the adhesion force between microbial cells; add a trace element composite additive composed of iron, manganese, zinc, and copper, and the concentrations of each element are 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; use a mixed carbon source of sodium acetate and glucose, with an initial mass ratio of 3-4:1 and a later adjustment to 1-2:1 for microbial growth and particle structure formation. During the cultivation process of aerobic granular sludge, introduce a multi-strengthening strategy: add γ-polyglutamic acid with a concentration of 5-6 mg / L as an extracellular polymer (EPS) synergist, and its unique molecular structure can significantly enhance the adhesion force between microbial cells and accelerate particle aggregation; at the same time, add a trace element composite additive composed of iron, manganese, zinc, and copper, and the concentrations of each element are accurately 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 to improve the pollutant degradation efficiency by activating the activity of key metabolic enzymes in microorganisms. In addition, adopt a dynamic mixed carbon source system of sodium acetate and glucose. Set the mass ratio of the two at 3-4:1 at the initial stage of cultivation to provide sufficient energy for the rapid proliferation of microorganisms; as the particles are initially formed, gradually adjust it to 1-2:1 in the later stage to optimize the carbon source distribution and promote the densification and stability improvement of the particle structure.

[0012] As a further solution of the present invention, in step S1, the cultivation method is as follows: pulse aeration is combined with intermittent stirring to create an alternating aerobic-anaerobic microenvironment, promoting microbial aggregation and granulation; the temperature is controlled at 28-29 °C in the initial stage of cultivation for rapid microbial proliferation; after the initial formation of granules, it is reduced to 25-26 °C to promote EPS secretion; the oxidation-reduction potential (ORP) is regulated in real time, 100-130 mV in the initial stage and 50-80 mV in the formation stage for microbial metabolism; the domestication process is as follows: when the granular sludge is initially formed, the actual printing and dyeing wastewater is used for domestication. The specific cultivation method: the method of combining pulse aeration and intermittent stirring is used. Pulse aeration can intermittently provide sufficient dissolved oxygen to the system, while intermittent stirring makes the dissolved oxygen evenly distributed throughout the reaction system. The two work together to create an alternating aerobic-anaerobic microenvironment. This alternating change of the microenvironment not only provides suitable living conditions for different metabolic types of microorganisms, but also promotes the interaction between microorganisms, thus accelerating the process of microbial aggregation and granulation.

[0013] Temperature regulation: In the initial stage of cultivation, the temperature is strictly controlled at 28-29 °C. This temperature range is beneficial to the activity of enzymes in microorganisms and creates ideal temperature conditions for the rapid proliferation of microorganisms. After the initial formation of granular sludge, the temperature is reduced to 25-26 °C. The lower temperature stimulates microorganisms to secrete more extracellular polymeric substances (EPS). EPS is like "glue" and can enhance the adhesion between microbial cells, further promoting the stability and perfection of the granular structure.

[0014] Oxidation-reduction potential (ORP) regulation: The oxidation-reduction potential is precisely regulated in real time. In the initial stage of cultivation, the ORP is maintained at 100-130 mV. This potential range helps to activate the metabolic pathways of microorganisms and provides a suitable oxidation-reduction environment for the growth and reproduction of microorganisms. When entering the granule formation stage, the ORP is adjusted to 50-80 mV. Under this potential condition, the metabolic activities of microorganisms will change accordingly, which is beneficial to the further development and maturation of granular sludge.

[0015] Domestication process: When it is observed that the granular sludge is initially formed, the influent water is promptly switched from simulated printing and dyeing wastewater to actual printing and dyeing wastewater for domestication. The actual printing and dyeing wastewater has a complex composition. Through this domestication method, the microorganisms in the granular sludge can gradually adapt to the water quality characteristics of the actual wastewater, improving its treatment capacity and adaptability to the actual printing and dyeing wastewater.

[0016] As a further solution of the present invention, in step S2, the domesticated aerobic granular sludge is used for the treatment of actual printing and dyeing wastewater, and the organic load is 1.5-1.8 kgCOD / (m³ d), with a running cycle of 3.5 - 4 h, a residence time of 1.8 - 2 h, and a sludge age of 20 - 22 days. Real-time monitor the COD, BOD, NH3-N, TN, TP, and chromaticity indicators, and analyze the pollutant removal law and water quality change characteristics. Put the domesticated mature aerobic granular sludge into the actual printing and dyeing wastewater treatment system, and through precise regulation of the core process parameters, achieve efficient removal of pollutants and stable improvement of water quality. Set the organic load to 1.5 - 1.8 kg COD / (m³ d). This range can not only ensure that microorganisms obtain sufficient metabolic substrates but also avoid the inhibition of sludge activity caused by too high a load; control the running cycle within 3.5 - 4 h to ensure that microorganisms complete the whole process of adsorption and degradation in an anaerobic-aerobic alternating environment; set the residence time to 1.8 - 2 h to enable the wastewater to fully contact and react with the sludge; maintain the sludge age at 20 - 22 days to optimize the microbial population structure and ensure the treatment efficiency of the system. During the operation process, real-time monitor 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 chromaticity, deeply analyze the pollutant removal kinetic law, dynamically master the water quality change trend, and provide a scientific basis for process optimization.

[0017] As a further solution of the present invention, in step S3, the biological aerated filter adopts an upward flow design. The bottom water distribution system consists of a perforated pipe and a pebble support layer to ensure uniform water distribution; an adjustable microporous aerator precisely controls the aeration volume; three-level partitions are arranged inside 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, and the modified polyurethane sponge intercepts suspended solids and optimizes the microbial microenvironment, enhancing the removal ability of organic matter, chromaticity, and suspended solids. The biological aerated filter (BAF) adopts an innovative upward flow design to construct an efficient and stable pretreatment system. The bottom water distribution system consists of a composite structure of a perforated pipe and a pebble support layer. Through scientific pore size distribution and support layer gradation, it ensures that the wastewater rises evenly, avoiding short-circuit flow and hydraulic dead ends; is equipped with an adjustable microporous aerator to achieve precise regulation of the aeration volume within the range of 0 - 10 m³ / (m² h) to meet the oxygen consumption requirements of microorganisms under different water quality conditions. Three-level partitions are arranged inside the filter to divide the treatment space into gradient reaction units, enabling the wastewater to successively experience treatment stages such as enhanced adsorption, biodegradation, and deep interception during the rising process, significantly improving the pollutant removal efficiency. The filter is filled with a composite filler of ceramsite and modified polyurethane sponge. Among them, the ceramsite, with its rich pore structure and large specific surface area, provides a stable attachment and growth carrier for microorganisms; the modified polyurethane sponge uses its unique three-dimensional network structure to efficiently intercept suspended solids, and at the same time optimizes the microbial living microenvironment through surface modification technology, synergistically improving the removal efficiency of organic matter, chromaticity, and suspended solids, and ensuring stable effluent water quality.

[0018] As a further solution of the present invention, in step S3, the operating parameters of the biological aerated filter are as follows: in the start-up and film-forming stage, the influent water is at a low load, and the hydraulic load is 0.5-1.0 m³ / (m² h), the DO is maintained at 2-3 mg / L, and the film formation is completed in 15-20 days; during the mature operation, the retention time and the organic load are adjusted according to the influent concentration. For low concentrations, it is 0.3-0.5 kg COD / (m³ d)), the head loss is regularly monitored, and when it exceeds 1.5 m, air-water combined backwashing is carried out, and the water washing intensity is 8-12 L / (m² s), and the time is 10-15 min; and the operating parameters of the BAF are adjusted in real time according to the effluent quality of the SBR; an on-line monitoring device is installed at the effluent end of the BAF to feedback data to regulate the parameters of the dual-membrane process; the microbial flora of the BAF is analyzed regularly. The operating parameter system of the biological aerated filter (BAF) follows a scientific and dynamic regulation strategy: in the start-up and film-forming stage, a low-load influent water mode is adopted, and the hydraulic load is strictly controlled at 0.5-1.0 m³ / (m² h), while maintaining the dissolved oxygen (DO) concentration at 2-3 mg / L synchronously to create a stable environment for the attachment and growth of microorganisms, and ensuring the efficient film formation of the biofilm within 15-20 days. After entering the mature operation stage, the system implements intelligent regulation according to the influent pollutant concentration: when treating low-concentration wastewater (0.3-0.5 kg COD / (m³ d)), the retention time and the organic load configuration are dynamically optimized to maintain the balance between treatment efficiency and energy consumption. During the operation process, by monitoring the head loss of the filter in real time, when the value exceeds 1.5 m, the air-water combined backwashing procedure is immediately started, where the water washing intensity is set at 8-12 L / (m² s), and the washing duration is controlled within 10-15 min to effectively remove the pollutants intercepted on the surface of the filter media and ensure the permeability of the filter. In addition, a data linkage mechanism is constructed between the BAF and the front and back treatment units: the operating parameters of the BAF are adjusted in real time according to the effluent quality of the sequencing batch reactor (SBR) to ensure that the pretreatment effect matches the requirements of the subsequent process; at the same time, an on-line monitoring device is deployed at the effluent end of the BAF to feedback the water quality data to the dual-membrane process control system in real time to realize the adaptive optimization of the operating parameters in the advanced treatment link. The system also regularly conducts an analysis of the microbial flora structure of the BAF. Through the dynamic monitoring of microbial diversity and functional flora, it provides a biological basis for the optimization of process parameters and fault warning.

[0019] As a further solution of the present invention, in step S4, the ultrafiltration membrane uses a high-strength hollow fiber membrane with an amphoteric ion polymer anti-fouling coating to inhibit pollutant attachment through electrostatic repulsion and high hydrophilicity; the reverse osmosis membrane selects a nanoscale polyamide composite membrane, equipped with an oxidation-reduction potential monitoring and reductant automatic injection system to prevent oxidative substances from damaging the membrane module. In the advanced treatment link of the dual-membrane process, the ultrafiltration unit uses a high-strength hollow fiber membrane module with an amphoteric ion polymer anti-fouling coating loaded on the surface. This coating constructs a dual anti-fouling barrier through electrostatic repulsion effect and high hydrophilicity characteristics: on the one hand, the charge characteristics of amphoteric ions can repel pollutants with the same charge, reducing their adsorption on the membrane surface; on the other hand, the highly hydrophilic surface enables water molecules to pass through quickly, reducing the contact probability between pollutants and the membrane surface, and effectively inhibiting the occurrence of membrane fouling. The reverse osmosis unit is equipped with a nanoscale polyamide composite membrane, which has excellent desalination performance and water production efficiency. At the same time, the system integrates an oxidation-reduction potential (ORP) real-time monitoring and reductant automatic injection device. By continuously monitoring the ORP value of the influent water, it accurately judges the concentration of oxidative substances in the water, and automatically adds reductants according to the set threshold to neutralize strong oxidative components such as residual chlorine in time, avoiding irreversible damage to the polyamide membrane structure, thus 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: The present invention significantly shortens the cultivation and domestication period: Through innovative cultivation strategies, the cultivation and domestication period of aerobic granular sludge is shortened by 30 - 40% compared with traditional methods, accelerating the process startup speed and reducing the upfront construction cost and time cost. High-efficiency pollutant removal: Multiple technologies work together to achieve efficient treatment of printing and dyeing wastewater. The effluent quality meets the standard of "Recycled Water Quality for Textile Dyeing and Finishing Industry" (FZ / T01107 - 2011), and the wastewater reuse rate reaches 60 - 70%, improving the water resource utilization rate and reducing the enterprise's water use cost. Strong anti-membrane fouling performance: Optimization of pretreatment and innovation of the dual-membrane process reduce the membrane fouling rate by more than 50%. The chemical cleaning period is extended from 7 - 10 days to 30 - 45 days. The service life of the ultrafiltration membrane is extended to 5 - 8 years, and the service life of the reverse osmosis membrane is extended to 4 - 6 years, significantly reducing the membrane replacement and maintenance cost. Significantly reduce the operating cost: The overall treatment system optimizes process parameters, reduces sludge production, reduces energy consumption and membrane treatment cost, saving 30 - 40% of the treatment cost compared with the existing technology, and enhancing the economic feasibility of the process.

[0021] To more clearly illustrate the structural features and functions of the present invention, the following will combine the drawings with specific embodiments to elaborate on the present invention in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the overall flow chart of the method for treating printing and dyeing wastewater based on aerobic granular sludge technology of the present invention.

[0023] Figure 2 It is the intelligent regulation flowchart of the operation parameters of the double-membrane process of the present invention. Specific embodiments

[0024] The present invention will be further described below in conjunction with the drawings and relevant knowledge, and will be described clearly and completely. Obviously, the described applications are only a part of the embodiments of the present invention, rather than all embodiments.

[0025] In view of the fact that the existing printing and dyeing wastewater contains a large number of pollutants such as dyes, sizing agents, and auxiliaries, it has the characteristics of complex composition, high chroma, high organic matter concentration, and poor biodegradability, which is a difficult problem in the field of industrial wastewater treatment. Traditional treatment technologies such as the activated sludge method and the physicochemical method have problems such as low treatment efficiency, large sludge production, high operating cost, and insufficient advanced treatment ability; while the membrane treatment technology can achieve deep purification of water quality, but the membrane pollution is serious, the service life is short, and the operation and maintenance cost is high. In addition, the conventional aerobic granular sludge cultivation period is long, which limits its rapid application in actual projects.

[0026] Referring to Figure 1 - Figure 2 As shown, the present invention provides a method for treating printing and dyeing wastewater based on aerobic granular sludge technology, including the following steps: Step S1: Cultivation and domestication 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 a high-load simulated printing and dyeing wastewater with a COD of 2000 mg / L is added to the reactor. Cultivation method: Functional additive components: Add γ-polyglutamic acid as an extracellular polymer (EPS) promoter with a concentration of 5 - 6 mg / L to enhance the adhesion between microbial cells; Add a trace element composite additive composed of iron, manganese, zinc, copper, etc., and the concentrations of each element are 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; Use a mixed carbon source of sodium acetate and glucose, with an initial mass ratio of 3 - 4:1 and a later adjustment to 1 - 2:1 to optimize the growth of microorganisms and the formation of particle structure. Furthermore: Combine pulsed aeration (aeration for 5 minutes, aeration stop for 3 minutes) with intermittent stirring (rotation speed 50 - 80 r / min, stirring for 5 minutes, stopping for 10 minutes) to create an alternating aerobic-anaerobic microenvironment and promote microbial aggregation and granulation. Furthermore, precise environmental regulation: The temperature is controlled at 28 - 29°C in the initial stage of cultivation, which is conducive to the rapid proliferation of microorganisms; after the initial formation of granules, it is reduced to 25 - 26°C to promote EPS secretion; the redox potential (ORP) is regulated in real-time, 100 - 130 mV in the initial stage and 50 - 80 mV in the formation stage to optimize the microbial metabolic pathway.

[0027] In the present invention, the domestication process: When the granular sludge is initially formed, the actual printing and dyeing wastewater is used for domestication, continuously optimizing the above parameters to shorten the domestication cycle. The morphology of the granules is monitored by optical microscopy and SEM, and indicators such as COD and EPS are detected to evaluate the treatment efficiency and granule stability. Step S2: Treatment of printing and dyeing wastewater with aerobic granular sludge: The domesticated aerobic granular sludge is used for the treatment of actual printing and dyeing wastewater, optimizing parameters such as organic loading (1.5 - 1.8 kgCOD / (m³ d)), operation cycle (3.5 - 4 h), residence time (1.8 - 2 h), sludge age (20 - 22 days), etc. COD, BOD, NH3-N, TN, TP, chromaticity and other indicators are monitored in real-time to analyze the removal law of pollutants and the water quality change characteristics, and most of the organic matter, nitrogen, phosphorus and other pollutants in the wastewater are efficiently removed. Step S3: Pretreatment of biological aerated filter (BAF); Furthermore: An upward flow design is adopted, and the bottom water distribution system consists of a perforated pipe and a pebble supporting layer to ensure uniform water distribution; an adjustable microporous aerator is used to precisely control the aeration volume; three-stage partitions are arranged inside to form a gradient treatment unit to improve the pollutant removal efficiency. More preferably, the packing is optimally selected: A composite packing of ceramsite and modified polyurethane sponge (volume ratio 3:2) is used. The ceramsite provides a surface for microbial attachment, and the modified polyurethane sponge intercepts suspended solids and optimizes the microbial microenvironment, enhancing the removal ability of organic matter, chromaticity and suspended solids. In the present invention: In the start-up and film-forming stage, the influent is at a low load (COD 100 - 150 mg / L), the hydraulic load is 0.5 - 1.0 m³ / (m² h), DO is maintained at 2 - 3 mg / L, and the film formation is completed in 15 - 20 days. During mature operation, the residence time (3 - 4 h for high concentration, 1.5 - 2 h for low concentration) and organic loading (0.6 - 0.8 kgCOD / (m³ d) for high concentration, 0.3 - 0.5 kgCOD / (m³ d) for low concentration) are adjusted according to the influent concentration. The head loss is monitored regularly, and when it exceeds 1.5 m, air-water combined backwashing is carried out (air washing intensity 15 - 20 L / (m² s), water washing intensity 8 - 12 L / (m² s), time 10 - 15 min). In the present invention, the synergistic enhancement mechanism is as follows: linked with the aerobic granular sludge process, the BAF operating parameters are adjusted in real time according to the SBR effluent quality; an online monitoring device is set at the BAF outlet end to feedback data to regulate the double membrane process parameters; the BAF microbial flora is regularly analyzed to optimize the operating conditions and enhance the overall synergistic treatment effect.

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

[0029] Furthermore, an LSTM (Long Short-Term Memory Network) prediction model was constructed, and the water quality fluctuation data, operating parameters and historical BAF treatment effects of the SBR in the previous 12 hours were input to predict the parameters that need to be adjusted for BAF 3 hours in advance. For example, when the model predicts that the organic matter concentration in the SBR effluent will increase significantly, the system will pre-increase the organic load of BAF to 0.8kgCOD / (m³ d) and optimize the mixing ratio of composite fillers (increasing the proportion of modified polyurethane sponge from 40% to 50%) to enhance the interception capacity of macromolecular pollutants. At the same time, by comparing the treatment efficiency data of SBR and BAF, the model parameters are automatically calibrated to form a closed-loop optimization system of "monitoring-prediction-control-feedback".

[0030] In the present invention, the dual membrane parameters are adjusted by graded threshold control, and high-precision online monitoring equipment is deployed at the BAF outlet. The monitoring indicators include COD, turbidity, total iron, total manganese and microbial metabolites (such as extracellular polymers EPS). Set three-level thresholds to trigger dual membrane process adjustment: Level 1 threshold: When the BAF outlet turbidity is greater than 3NTU or COD is greater than 80mg / L, the system automatically increases the physical backwashing intensity of the ultrafiltration membrane (the water flushing intensity is increased from 15L / (m² s) increased to 20L / (m² s), and shorten the chemical cleaning cycle of the reverse osmosis membrane (adjusted from 30 days to 25 days); Secondary threshold: If the total iron / total manganese concentration is greater than 0.5 mg / L, immediately start the reducing agent pre-dosing system of the reverse osmosis membrane (sodium bisulfite concentration increased by 30%) to prevent metal oxides from oxidative damage to the membrane; Third-level threshold: When the EPS concentration increases abnormally (>10 mg / L), the biological pollution warning of the double membrane system is triggered, and an ozone pre-oxidation unit is added before ultrafiltration (dosage 0.5-1 mg / L), and the reverse osmosis recovery rate is reduced to 70% to avoid the rapid formation of biofouling on the membrane surface. Establish a joint control algorithm for BAF and dual membrane processes, and calculate the optimal operating parameter combination of the dual membrane system in real time according to the BAF effluent water quality. For example, when the concentration of organic matter in BAF effluent is low, the operating pressure of the ultrafiltration membrane is automatically reduced to 0.08MPa to reduce energy consumption; if the BAF effluent contains trace amounts of difficult-to-degrade substances (such as azo dyes), the reverse osmosis membrane operating pressure is linked to 2.0MPa, and the charge density of the zwitterionic polymer coating is adjusted to enhance the interception effect of charged pollutants. At the same time, the dual-membrane system feeds back the operating status data (such as membrane flux attenuation rate and desalination rate changes) to the BAF control system to assist in optimizing the pretreatment intensity of the BAF.

[0031] Step S4: Double membrane process for deep processing, innovative membrane component selection: The ultrafiltration membrane uses a high-strength hollow fiber membrane with a zwitterionic polymer anti-pollution coating, which inhibits the attachment of pollutants through electrostatic repulsion and high hydrophilicity; the reverse osmosis membrane uses a nano-scale polyamide composite membrane with a rejection rate of ≥99.5%, and a water output increased by 20-30%. It is equipped with a redox potential monitoring and reductant automatic injection system to prevent oxidizing substances from damaging the membrane components.

[0032] Intelligent control system: Build an intelligent control system for operating parameters based on machine learning, collect data such as inlet water quality, pressure, flow, etc., use deep neural network models to predict treatment effects, automatically optimize ultrafiltration membrane operating pressure (0.05-0.15MPa), cross-flow flow rate (0.5-2m / s) and reverse osmosis membrane operating pressure (1.0-2.5MPa), recovery rate (75-85%), predict membrane pollution trends and adjust parameters in advance. Specifically, the double-membrane process is the terminal link for deep purification of printing and dyeing wastewater. It is composed of two-stage membrane treatment units, ultrafiltration (UF) and reverse osmosis (RO), connected in series to form a gradient purification system of "coarse filtration-fine filtration". The ultrafiltration link uses an external pressure high-strength hollow fiber membrane component with an inner diameter of 0.8-1.2mm and a membrane pore size range of 0.01-0.1μm, which can effectively intercept macromolecular organic matter, colloids, bacteria and other pollutants, and provide pretreatment guarantee for the reverse osmosis membrane; the reverse osmosis link uses an anti-pollution nano-scale polyamide composite membrane with a membrane element specification of 8 inches × 40 inches, a desalination rate of ≥99.5%, and a water output that is 20-30% higher than that of conventional membranes. It can remove soluble salts, small molecular organic matter and heavy metal ions to ensure that the effluent meets the reuse standard.

[0033] Furthermore, anti-pollution design: the membrane surface is coated with a zwitterionic polymer anti-pollution coating, which reduces the adsorption of pollutants through the dual mechanisms of electrostatic repulsion (zeta potential maintained at ±20-30mV) and super-hydrophilicity (contact angle <30°); equipped with a chemical enhanced backwash (CEB) system, a weak alkaline (pH10-11) or weak acid (pH3-4) chemical cleaning is performed every 2-3 cycles to prevent membrane pore blockage. Parameter control: the operating pressure is controlled at 0.05-0.15MPa, the cross-flow flow rate is maintained at 0.8-1.5m / s, and the recovery rate is set to 90-95%; the time-flux dual threshold control strategy is adopted. When the membrane flux decay exceeds the initial value by 15% or the operating time reaches 4 hours, the physical backwash is automatically started (water flushing intensity 15-20L / (m² s), duration 30-60s).

[0034] Optimize the intelligent operation, protection and monitoring of the reverse osmosis membrane system: integrate the online redox potential (ORP) monitor (accuracy ±5mV) and the automatic dosing device of the reducing agent. When the inlet ORP is greater than 200mV, sodium bisulfite solution (concentration 100-300ppm) is added to control the residual chlorine content to less than 0.1mg / L; configure pressure sensors and flow sensors to monitor the pressure difference of membrane elements in real time (warning when the pressure drop of a single membrane is greater than 0.15MPa). Operation optimization: The operating pressure is dynamically adjusted according to the inlet salinity (1.2-2.5MPa), and the recovery rate is set to 75-85%; establish a prediction model based on machine learning, and predict the membrane pollution trend 72 hours in advance by analyzing the inlet water quality (conductivity, TOC), operating parameters and historical data, and automatically optimize the flushing frequency and chemical cleaning plan.

[0035] In the present invention, the linkage mechanism is as follows: the ultrafiltration effluent serves as the reverse osmosis influent, and a security filter (with a precision of 5 μm) is set between the two-stage membranes to prevent large particulate matter from damaging the RO membrane; the RO concentrated water is refluxed to the front end of the BAF for secondary treatment to improve the water resource utilization rate. Water quality compliance control: online monitor the effluent indexes such as COD, conductivity, turbidity, ammonia nitrogen, etc. When a certain parameter approaches the standard limit value (such as COD > 15 mg / L, conductivity > 500 μS / cm), automatically trigger the adjustment of the dual-membrane system parameters (such as reducing the RO recovery rate, enhancing the ultrafiltration backwashing intensity) to ensure that the water quality stably meets the requirements of "Textile Dyeing and Finishing Industry Reclaimed Water Quality" (FZ / T01107 - 2011).

[0036] Comprehensive prevention and control of membrane pollution: For physical prevention, ultrasonic online cleaning is adopted (every 2 - 4 hours, with a frequency of 20 - 40 kHz and a power of 50 - 100 W); for chemical prevention, a composite cleaning agent composed of a chelating agent, a surfactant, and a bioenzyme is used, and the cleaning is carried out by intelligently matching the pollution type; for biological prevention, a biological activated carbon filtration unit is set before ultrafiltration to degrade trace organic matters and reduce the risk of biological pollution. In the present invention, the cultivation and domestication period is significantly shortened: through innovative cultivation strategies, the cultivation and domestication period of aerobic granular sludge is shortened by 30 - 40% compared with the traditional method, accelerating the process startup speed and reducing the upfront construction cost and time cost. High-efficiency pollutant removal: Multiple technologies cooperate to achieve efficient treatment of printing and dyeing wastewater. The effluent water quality meets the standards of "Textile Dyeing and Finishing Industry Reclaimed Water Quality" (FZ / T01107 - 2011), and the wastewater reuse rate reaches 60 - 70%, improving the water resource utilization rate and reducing the enterprise's water use cost. Strong anti-membrane fouling performance: Optimization of pretreatment and innovation of the dual-membrane process reduce the membrane fouling speed by more than 50%. The chemical cleaning period is extended from 7 - 10 days to 30 - 45 days. The service life of the ultrafiltration membrane is extended to 5 - 8 years, and the service life of the reverse osmosis membrane is extended to 4 - 6 years, significantly reducing the membrane replacement and maintenance cost. Significantly reduce the operating cost: The overall treatment system optimizes process parameters, reduces sludge production, reduces energy consumption and membrane treatment cost, saving 30 - 40% of the treatment cost compared with the existing technology and enhancing the economic feasibility of the process.

[0037] In the present invention, for the efficient aerobic granular sludge cultivation system, strengthening factors: adding γ-polyglutamic acid and a composite additive of trace elements with a specific ratio. γ-polyglutamic acid enhances the adhesion between cells, and trace elements activate the activity of metabolic enzymes. At the same time, a dynamically adjusted mixed carbon source is adopted. Compared with the traditional single carbon source or the cultivation method without additives, it significantly improves the formation speed and stability of granular sludge, shortening the cultivation and domestication period by 30 - 40%. Environmental regulation: By combining pulsed aeration and intermittent stirring, accurately control environmental parameters such as temperature and ORP, creating an alternating microenvironment and suitable metabolic conditions, breaking the traditional constant cultivation mode, providing a more favorable growth environment for microbial aggregation and granulation, and promoting the rapid formation and structural optimization of granular sludge.

[0038] A collaborative and efficient wastewater treatment process combination with multi-stage treatment collaboration: The aerobic granular sludge treatment, biological aerated filter pretreatment, and advanced treatment by dual-membrane process are organically combined. Each treatment unit has a clear division of labor and works in coordination with each other. The aerobic granular sludge efficiently removes most pollutants, the BAF further treats the residual impurities, and the dual-membrane process achieves deep purification, forming a complete printing and dyeing wastewater treatment chain. Compared with single or simple combined processes, it significantly improves the pollutant removal efficiency and the quality of the effluent, and the wastewater reuse rate reaches 60 - 70%. Parameter dynamic optimization: Set dynamically adjustable operating parameters for each treatment link and establish a parameter linkage optimization mechanism to adjust the subsequent process parameters in real time according to the influent water quality and the effect of the previous treatment, ensuring that the entire treatment system is always in a highly efficient operating state and enhancing the adaptability and stability of the process.

[0039] Advanced membrane fouling prevention and control technology, membrane module: The ultrafiltration membrane uses an amphoteric ion polymer anti-fouling coating, and the reverse osmosis membrane selects a high-performance nanoscale polyamide composite membrane and is equipped with an intelligent monitoring and protection system, improving the anti-fouling performance and treatment efficiency of the membrane from the aspects of membrane material and structure. 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 the ultrafiltration membrane is extended to 5 - 8 years, and the life of the reverse osmosis membrane is extended to 4 - 6 years.

[0040] Intelligent operation and management mode, introducing an intelligent control system based on machine learning to achieve automatic and precise control of the operating parameters of the dual-membrane process and predict the trend of membrane fouling, changing the traditional manual operation mode based on experience, improving the intelligent level of process operation and the reliability of treatment effect, while reducing the labor management cost and the risk of operation errors, providing a new path for the intelligent upgrade of the printing and dyeing wastewater treatment process.

[0041] Example 1, a method for treating printing and dyeing wastewater based on aerobic granular sludge technology, comprising the following steps: Step S1: Cultivation and domestication of aerobic granular sludge: In an SBR reactor with a large height-to-diameter ratio (H / D = 10), at room temperature, the pH is controlled at 7.0 - 7.5, and a high-load simulated printing and dyeing wastewater with a COD of 2000 mg / L is added. 5 mg / L of γ-polyglutamic acid and a trace element composite additive (1 mg / L of iron, 0.5 mg / L of manganese, 0.3 mg / L of zinc, 0.2 mg / L of copper) are added, and a mixed carbon source with a mass ratio of sodium acetate to glucose of 3:1 is used. Pulsed aeration (aeration for 5 minutes, aeration stop for 3 minutes) and intermittent stirring (rotation speed 60 r / min, stirring for 5 minutes, stop for 10 minutes) are adopted. In the initial stage of cultivation, the temperature is controlled at 28 °C and the ORP is controlled at 120 mV. After 45 days of cultivation, the preliminary formation of aerobic granular sludge is observed. At this time, the sludge concentration reaches 8500 mg / L, the sludge volume index (SVI) is 42 mL / g, and the average sludge particle size is 1.36 mm. Subsequently, actual printing and dyeing wastewater is used for domestication, the mass ratio of sodium acetate to glucose is adjusted to 2:1, the temperature is gradually reduced to 26 °C, and the ORP is reduced to 80 mV. After 15 days of domestication, the microbial population of aerobic granular sludge is stable, and the removal rate of COD reaches 85%.

[0042] Step S2: Treat printing and dyeing wastewater with aerobic granular sludge; The domesticated aerobic granular sludge is used to treat actual printing and dyeing wastewater, and the organic load is adjusted to 1.5 kgCOD / (m³ d), the operation cycle is 4 h, the residence time is 2 h, and the sludge age is 20 days. After treatment, the COD of the printing and dyeing wastewater is reduced from 1200 mg / L to 150 mg / L, the BOD is reduced from 400 mg / L to 30 mg / L, the NH3-N is reduced from 50 mg / L to 5 mg / L, the TN is reduced from 60 mg / L to 15 mg / L, the TP is reduced from 8 mg / L to 1 mg / L, and the chromaticity is reduced from 500 times to 50 times.

[0043] Step S3: Pretreatment by biological aerated filter; The BAF adopts an up-flow design. The bottom water distribution system is a perforated pipe combined with a pebble support layer. The aeration system uses adjustable microporous aerators, and three-level partition plates are arranged inside. A mixed filler of ceramsite and modified polyurethane sponge with a volume ratio of 3:2 is selected. In the startup stage, the influent COD is 120 mg / L, the hydraulic load is 0.8 m³ / (m² h), the DO is maintained at 2.5 mg / L, and the membrane is formed in 20 days. After the membrane formation is mature, the SBR effluent is used as the influent. When the COD of the treated printing and dyeing wastewater is about 150 mg / L, the residence time is set to 3 h, and the organic load is controlled at 0.7 kgCOD / (m³ d), and the DO is maintained at 2 - 3 mg / L. Regularly monitor the head loss of the filter. When the head loss reaches 1.5 m, air-water combined backwashing is carried out, and the air scouring intensity is 18 L / (m² s), the water flushing intensity is 10 L / (m² s), and the backwashing time is 12 min. The operation results show that the removal rate of residual organic matter by BAF reaches 45%, the chromaticity removal rate reaches 65%, the SS removal rate reaches 85%, and the turbidity removal rate reaches 92%.

[0044] Step S4: Advanced treatment by dual-membrane process; The ultrafiltration membrane uses a high-strength hollow fiber membrane with an amphoteric ion polymer anti-pollution coating, and the operating pressure is 0.1 MPa; the reverse osmosis membrane selects a nanoscale polyamide composite membrane, and the operating pressure is 1.5 MPa. The intelligent control system automatically adjusts the operating parameters according to the influent water quality. After 60 days of operation, the membrane flux can still maintain 82% of the initial flux, and the effluent water quality meets the requirements of the recycled water quality for the textile dyeing and finishing industry, with COD < 20 mg / L, BOD < 5 mg / L, NH3-N < 1 mg / L, TN < 5 mg / L, TP < 0.5 mg / L, chromaticity < 10 times, and conductivity < 500 μS / cm.

[0045] Example 2, a method for treating printing and dyeing wastewater based on aerobic granular sludge technology, includes the following steps: Step S1: Cultivation and domestication of aerobic granular sludge; In the SBR reactor, the pH is adjusted to 7.2 - 7.4, and simulated printing and dyeing wastewater is added. γ-Polyglutamic acid 6 mg / L and trace element composite additive (iron 1.2 mg / L, manganese 0.6 mg / L, zinc 0.4 mg / L, copper 0.3 mg / L) are added, and a mixed carbon source with a mass ratio of sodium acetate to glucose of 4:1 is used. Pulse aeration (aeration for 5 minutes, aeration stop for 3 minutes) and intermittent stirring (rotation speed 70 r / min, stirring for 5 minutes, stopping for 10 minutes) are adopted. In the initial stage of cultivation, the temperature is controlled at 29 °C, and the ORP is controlled at 130 mV. After 42 days, granular sludge is formed, the sludge concentration is 8300 mg / L, the SVI is 43 mL / g, and the average sludge particle size is 1.29 mm. It is changed to domestication with actual printing and dyeing wastewater, the mass ratio of sodium acetate to glucose is adjusted to 1:1, the temperature is reduced to 25 °C, and the ORP is reduced to 70 mV. After 12 days of domestication, the microbial population is stable, and the COD removal rate reaches 88%.

[0046] Step S2: Treatment of printing and dyeing wastewater by aerobic granular sludge; Adjust the organic load to 1.8 kgCOD / (m³ d), the operation cycle is 3.5 h, the residence time is 1.8 h, and the sludge age is 22 days. After treatment, the COD of the printing and dyeing wastewater is reduced to 130 mg / L, the BOD is reduced to 25 mg / L, the NH3-N is reduced to 4 mg / L, the TN is reduced to 12 mg / L, the TP is reduced to 0.8 mg / L, and the chromaticity is reduced to 40 times.

[0047] Step S3: pretreatment in aerated biological filter; The structure and filler of BAF are the same as those in Example 1. When treating printing and dyeing wastewater with a COD of about 100 mg / L, the residence time is set to 2 h, and the organic load is controlled at 0.4 kgCOD / (m³ d), DO is maintained at 2-3mg / L. When the head loss reaches 1.5m, air-water combined backwashing is carried out, and the air flushing intensity is 16L / (m² s), water impact strength 9L / (m² s), backwashing time 10min. The operation results show that the removal rate of BAF for residual organic matter is 40%, the removal rate of chroma is 60%, the removal rate of SS is 80%, and the removal rate of turbidity is 90%.

[0048] Step S4: double membrane process deep treatment; The operating pressure of the ultrafiltration membrane was adjusted to 0.12MPa, and the operating pressure of the reverse osmosis membrane was 1.6MPa. After the intelligent control system optimized the parameters, the membrane flux remained 83% of the initial flux after 80 days of operation, and the effluent quality met the requirements for reused water, further verifying the effectiveness and stability of the process of the present invention.

[0049] In the present invention, aerobic granular sludge treatment is used as the front-end biological treatment link of printing and dyeing wastewater treatment. With its unique structure and high biological activity, it can efficiently remove most of the organic matter, nitrogen, phosphorus and other pollutants in the printing and dyeing wastewater. During the treatment process, by optimizing the operating parameters, aerobic granular sludge can significantly reduce the COD, BOD, NH3-N, TN, TP and other indicators in the wastewater. However, due to the complex composition of printing and dyeing wastewater, some pollutants such as difficult-to-degrade organic matter, chromaticity, SS and turbidity still remain in the wastewater after treatment. At this time, the aerated biological filter is connected to the treatment process as a pretreatment link, and the effluent after aerobic granular sludge treatment is used as the inlet. A large number of microorganisms are attached to the surface of the filter material in BAF, which can further degrade the residual organic matter, and at the same time, the interception effect of the filter material is used to effectively remove SS and turbidity, and the chromaticity of the wastewater is reduced by the dual effects of biology and physics. Aerobic granular sludge treatment reduces the processing load for BAF, allowing BAF to focus more on treating residual pollutants; while BAF "checks for leaks and fills in the gaps" in the wastewater after aerobic granular sludge treatment. The two work together to create more favorable water inlet conditions for the subsequent double-membrane process, effectively improving the pollutant removal effect of the entire treatment system.

[0050] As a pretreatment technology for the dual-membrane process, aerated biological filter plays a vital role in slowing down membrane pollution and extending the service life of membrane components. Although the ultrafiltration and reverse osmosis membrane components in the dual-membrane process can achieve deep purification of wastewater, membrane pollution has always been a key factor restricting its efficient operation.

[0051] By removing pollutants such as residual organic matter, SS, and turbidity in the wastewater, BAF reduces the deposition and adsorption of these substances on the membrane surface, thereby reducing the possibility of membrane fouling at the source. At the same time, the pretreatment of wastewater by BAF makes the water quality entering the dual-membrane process more stable, reduces the treatment pressure of the dual-membrane process, and is conducive to the dual-membrane process to achieve efficient and in-depth treatment of wastewater by adjusting operating parameters, so that the effluent water quality meets the requirements for reclaimed water quality in the textile dyeing and finishing industry.

[0052] In addition, although the aerobic granular sludge treatment and the in-depth treatment by the dual-membrane process are not directly connected, they achieve indirect cooperation through the intermediate link of the biological aerated filter. The aerobic granular sludge treatment preliminarily purifies the printing and dyeing wastewater, significantly reducing the pollutant concentration and reducing the treatment burden for the subsequent BAF and dual-membrane processes. As the terminal of the treatment process, the dual-membrane process deeply purifies the wastewater treated by the previous two processes to ensure that the final effluent water quality meets the reclaimed water standard. The strict requirements of the dual-membrane process for the treated water quality also prompt the continuous optimization of the aerobic granular sludge treatment and BAF pretreatment to meet its influent requirements. The three influence and promote each other, jointly ensuring the efficiency and stability of the printing and dyeing wastewater treatment.

[0053] The technical principle of the present invention has been described above in combination with specific embodiments, which are only the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. Those skilled in the art can think of other specific embodiments of the present invention without creative labor, and these embodiments will fall within the protection scope of the present invention.

Claims

1. A method for treating printing and dyeing wastewater based on aerobic granular sludge technology, characterized in that It includes the following steps: Step S1: Cultivation and domestication of aerobic granular sludge. A sequencing batch activated sludge reactor with a large height-diameter ratio is used. Under room temperature conditions, the pH is controlled at 7.0 - 7.

5. A high-load simulated printing and dyeing wastewater with a COD of 2000 mg / L is added to the reactor to start cultivating aerobic granular sludge; Step S2: Treatment of printing and dyeing wastewater with aerobic granular sludge: The cultivated and domesticated aerobic granular sludge is used to treat printing and dyeing wastewater. By adjusting process parameters such as organic load, operation cycle, retention time, and sludge age, the process parameters for treating printing and dyeing wastewater with aerobic granular sludge are obtained; Step S3: Pretreatment of biological aerated filter: The biological aerated filter is started up and biofilm is formed using simulated wastewater. After the biofilm is mature, the effluent from the reactor during stable operation is used as the influent of the biological aerated filter; Step S4: Advanced treatment by dual-membrane process: The effluent from the biological aerated filter is treated by the dual-membrane process. Among them, ultrafiltration uses a high-strength hollow fiber membrane module with an external pressure operation mode; reverse osmosis uses an anti-pollution membrane module with anti-pollution property, high salt rejection rate, and high water production rate. By adjusting the operation parameters of the dual-membrane process, the effluent quality meets the requirements of the recycled water quality for textile dyeing and finishing industry.

2. The method for treating printing and dyeing wastewater based on aerobic granular sludge technology according to claim 1, characterized in that, In Step S1, during the cultivation of aerobic granular sludge, γ-polyglutamic acid is added as an extracellular polymer promoter with a concentration of 5 - 6 mg / L to enhance the adhesion force between microbial cells; a trace element composite additive composed of iron, manganese, zinc, and copper is added, and the concentrations of each element are 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 and adjusted to 1 - 2:1 later for microbial growth and granule structure formation.

3. The method for treating printing and dyeing wastewater based on the aerobic granular sludge technology according to claim 2, wherein, In Step S1, the cultivation method is: a combination of pulsed aeration and intermittent stirring is used to generate an alternating aerobic-anaerobic microenvironment to promote microbial aggregation and granulation; the temperature is controlled at 28 - 29 °C in the initial stage of cultivation for rapid microbial proliferation; after the granules are initially formed, it is reduced to 25 - 26 °C to promote EPS secretion; the redox potential is regulated in real time, 100 - 130 mV in the initial stage and 50 - 80 mV in the formation stage for microbial metabolism; the domestication process is: when the granular sludge is initially formed, actual printing and dyeing wastewater is used for domestication.

4. The method for treating printing and dyeing wastewater based on aerobic granular sludge technology according to claim 3, characterized in that, In step S2, the domesticated aerobic granular sludge is used for the actual treatment of printing and dyeing wastewater, with an organic load of 1.5 - 1.8 kg COD / (m³ d), the operation cycle is 3.5 - 4 h, the residence time is 1.8 - 2 h, the sludge age is 20 - 22 days, and the COD, BOD, NH3-N, TN, TP, and chromaticity indicators are monitored in real time to analyze the pollutant removal law and water quality change characteristics.

5. The method for treating printing and dyeing wastewater based on the aerobic granular sludge technology according to claim 4, characterized in that, In Step S3, the biological aerated filter adopts an upward flow design. The bottom water distribution system consists of a perforated pipe and a pebble support layer to ensure uniform water distribution; an adjustable microporous aerator accurately controls the aeration volume; three-stage partition plates are arranged inside to form a gradient treatment unit; a composite filler of ceramsite and modified polyurethane sponge is used. Ceramsite provides a surface for microbial attachment, and the modified polyurethane sponge intercepts suspended solids and optimizes the microbial microenvironment, enhancing the removal ability of organic matter, chromaticity, and suspended solids.

6. The method for treating printing and dyeing wastewater based on the aerobic granular sludge technology according to claim 5, characterized in that, In step S3, the operating parameters of the biological aerated filter are as follows: during the start-up and biofilm formation stage, the influent is fed at a low load, with a hydraulic load of 0.5 - 1.0 m³ / (m² h), the DO is maintained at 2 - 3 mg / L, and biofilm formation is completed in 15 - 20 days; during mature operation, the retention time and organic load are adjusted according to the influent concentration. For low concentrations of 0.3 - 0.5 kg COD / (m³ d)), the head loss is monitored regularly. When it exceeds 1.5 m, combined air-water backwashing is carried out, with a water washing intensity of 8 - 12 L / (m² s) and a time of 10 - 15 min. And adjust the operation parameters of the biological aerated filter in real time according to the effluent quality of the reactor; an on-line monitoring device is installed at the effluent end of the biological aerated filter to feedback data and regulate the parameters of the dual-membrane process; regularly analyze the microbial flora of the biological aerated filter.

7. The method for treating printing and dyeing wastewater based on aerobic granular sludge technology according to claim 6, characterized in that, In step S4, the ultrafiltration membrane uses a high-strength hollow fiber membrane with an amphoteric ion polymer anti-fouling coating to inhibit pollutant attachment through electrostatic repulsion and high hydrophilicity; the reverse osmosis membrane selects a nanoscale polyamide composite membrane and is equipped with a redox potential monitoring and reductant automatic injection system to prevent oxidative substances from damaging the membrane module.

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