A dyeing and finishing wastewater treatment system based on nylon fabric acid control dyeing and finishing process

Abstract

The application discloses a dyeing and finishing wastewater treatment system based on a nylon fabric acid control dyeing and finishing process, and relates to the technical field of wastewater treatment. The application discloses a dyeing and finishing wastewater treatment system based on a nylon fabric acid control dyeing and finishing process, and relates to the technical field of wastewater treatment. The inlet of the wastewater collecting pool is connected with a dyeing and finishing process drainage pipe, the outlet of the wastewater collecting pool is communicated with the water inlet of the pH adjusting pool through a lifting pump, the concentrated water outlet of the membrane separation device is connected to the water inlet end of the catalytic oxidation pool through a reflux pipe, and the clean water outlet of the membrane separation device is connected with the clean water recycling pool. The multi-stage adsorption and filtration unit realizes gradient adsorption and purification functions of the wastewater, solves the problems of low zeolite adsorption capacity and poor selectivity, and significantly reduces the material replacement frequency and operation cost.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a dyeing and finishing wastewater treatment system based on the acid-controlled dyeing and finishing process of nylon fabric. Background Technology

[0002] In the textile industry, nylon fabrics are widely used in high-end sportswear, outdoor products, and other fields due to their excellent abrasion resistance, elasticity, and dyeing properties. Acid dyeing is a common dyeing method for nylon fabrics. Its principle is to adjust the pH of the dye bath to acidic conditions (usually 4-6), allowing the dye anions to combine with the amine groups on the surface of the nylon fibers, achieving a bright color and high colorfastness. However, traditional acid dyeing processes for nylon have significant drawbacks: on the one hand, the dyeing process requires the use of large amounts of strong acids such as acetic acid and sulfuric acid to adjust the pH, resulting in highly acidic wastewater (pH≤4), high color intensity (up to 5000 times higher), and COD concentrations as high as 15000-20000 mg / L; on the other hand, the dye utilization rate is low (usually only 70%-80%), with a large amount of unfixed dye discharged with the wastewater, not only wasting resources but also posing a serious threat to aquatic ecosystems.

[0003] Patent CN108529818B discloses a comprehensive waste treatment system for dyeing and finishing. The patent enables centralized treatment of a large amount of wastewater, solid waste and exhaust gas generated during the dyeing and finishing process, reducing the emission of wastewater, solid waste and exhaust gas. At the same time, the three systems work together to avoid secondary pollution to the environment caused by wastewater, solid waste and exhaust gas generated by the wastewater treatment system, sludge treatment system and exhaust gas treatment system.

[0004] The aforementioned patent effectively solves the pollution problem of exhaust gas emissions during the dyeing and finishing process by constructing a synergistic system that includes exhaust gas treatment and wastewater treatment. Its exhaust gas treatment system integrates multiple treatment units such as an SNCR denitrification reactor and a semi-dry quench deacidification tower, while the wastewater treatment system achieves wastewater purification and reuse through processes such as neutralization, pressure filtration, and oxidation ditches. However, the wastewater from the acid-controlled dyeing and finishing process for nylon fabrics not only contains conventional dyeing and finishing pollutants but also presents a specific acidic environment and a combination of recalcitrant organic matter due to the acid-controlled process, posing requirements for precise pH adjustment, deep removal of organic matter, and efficient water reuse.

[0005] Therefore, this application proposes a dyeing and finishing wastewater treatment system based on the acid-controlled dyeing and finishing process of nylon fabric, which can achieve targeted treatment and water reuse of acidic wastewater through synergistic oxidation of ultraviolet photocatalysis and ozone aeration, as well as composite adsorption. Summary of the Invention

[0006] The purpose of this invention is to provide a dyeing and finishing wastewater treatment system based on the acid-controlled dyeing and finishing process of nylon fabric, so as to solve the technical problems mentioned in the background art, which require the use of large amounts of strong acids such as acetic acid and sulfuric acid to adjust the pH value during the dyeing process, resulting in highly acidic wastewater, high COD concentration, low dye utilization, resource waste, and serious threats to aquatic ecosystems.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a wastewater treatment system for dyeing and finishing processes based on acid-controlled dyeing and finishing of nylon fabrics, comprising a wastewater collection tank, a pH adjustment tank, a catalytic oxidation tank, a multi-stage adsorption filtration unit, a membrane separation device, and a clean water reuse tank connected in sequence; the inlet of the wastewater collection tank is connected to the dyeing and finishing process drainage pipe, the outlet of the wastewater collection tank is connected to the inlet of the pH adjustment tank through a booster pump, the concentrated water outlet of the membrane separation device is connected to the inlet of the catalytic oxidation tank through a return pipe, and the clean water outlet of the membrane separation device is connected to the clean water reuse tank; The multi-stage adsorption filtration unit includes an activated carbon adsorption layer and a composite zeolite layer, which are stacked and connected in series. The composite zeolite layer is filled with a mixture of modified zeolite and nano-alumina particles.

[0008] Preferably, a pH sensor is provided in the middle of the inner wall side of the pH adjustment tank, and an automatic dosing device is provided at the top of the inner wall of the pH adjustment tank. The automatic dosing device includes an alkali storage tank and an acid storage tank. The bottom of the alkali storage tank is connected to the dosing port of the pH adjustment tank via a first metering pump. The end of the alkali dosing pipe connected to the dosing port is equipped with a spiral nozzle. The alkali dosing pipe extends 20cm above the bottom of the pH adjustment tank. The bottom of the acid storage tank is connected to the inlet of the catalytic oxidation tank via a second metering pump.

[0009] Preferably, the catalytic oxidation tank is equipped with an ultraviolet photocatalytic component and an ozone aeration disc. The ultraviolet photocatalytic component consists of an ultraviolet lamp group and a honeycomb ceramic plate. The ultraviolet lamp group is covered with a quartz sleeve. The ultraviolet lamp group includes a germicidal lamp with a main wavelength of 254nm and a catalytic lamp with a main wavelength of 365nm. The ratio of germicidal lamps to catalytic lamps is 2:1. The outer wall of the honeycomb ceramic plate is loaded with titanium dioxide. The honeycomb ceramic plate is configured with a hexagonal channel structure. The ozone aeration disc is connected to an external gas source through an ozone generator. The ozone aeration disc has a pore diameter of 0.5-1mm, arranged in a ring array. The ozone aeration disc is fixedly installed at the bottom of the inner wall of the catalytic oxidation tank. A baffle is installed 20cm above the ozone aeration disc. The ultraviolet photocatalytic component is fixed to the inner wall of the catalytic oxidation tank by a bracket. The bracket suspends the ultraviolet photocatalytic component 10-20cm above the liquid surface. The bottom of the bracket is detachably connected to the inner wall of the catalytic oxidation tank by a flange. The inlet of the catalytic oxidation tank is located at the upper part of one side of the tank body, and the outlet is located at the lower part of the other side of the tank body. The inlet and outlet are diagonally arranged. A hydrogen peroxide dosing device is installed at the inlet of the catalytic oxidation tank. The dosing pump of the hydrogen peroxide dosing device and the power control terminal of the ozone generator are respectively connected to the controller. The controller dynamically adjusts the addition ratio of hydrogen peroxide and ozone based on the COD value of the influent and the ORP value of the reaction system.

[0010] Preferably, the modified zeolite in the composite zeolite layer is clinoptilolite treated with a silane coupling agent, the particle size of the nano-alumina particles is 50-100 nm, and the mass ratio of modified zeolite to nano-alumina is 3:1. The activated carbon adsorption layer is filled within a stainless steel mesh frame. The activated carbon in the adsorption layer is coconut shell activated carbon with a particle size of 2-4 mm and a filling density of 400-600 kg / m³. A backwashing pipe is installed at the bottom of the activated carbon adsorption layer, with a backwashing cycle of 24-48 hours. An exhaust port is installed at the top of the multi-stage adsorption filtration unit, which is connected to the activated carbon adsorber. The activated carbon adsorber is filled with granular activated carbon with a particle size of 4-6 mm and a filling height of 50-80 cm.

[0011] Preferably, the membrane separation device includes a spiral wound nanofiltration membrane module and a porous central tube. The membrane of the spiral wound nanofiltration membrane module is spirally wound around the outer wall of the porous central tube. A flow control valve is fixedly installed at the concentrate outlet of the spiral wound nanofiltration membrane module. A transparent detection tube section is provided at the front end of the flow control valve. A conductivity meter is installed inside the transparent detection tube section. The clean water outlet is connected to a PE pipe. The inlet of the membrane separation device is equipped with a security filter. The filter element of the security filter is a pleated polypropylene filter element with a filtration accuracy of 5-10μm. A differential pressure sensor is installed on the outside of the filter element. The membrane pore size is 1-4nm and the operating pressure is 0.8-1.5Mpa. The membrane separation device is equipped with a protective shell. A shock-absorbing buffer layer is installed between the protective shell and the spiral wound nanofiltration membrane module.

[0012] Preferably, a sludge treatment unit is provided downstream of the sludge discharge port of the catalytic oxidation tank; The sludge treatment unit includes a sedimentation tank, a sludge thickening tank, and a plate and frame filter press. An ultrasonic oscillator is installed at the bottom of the sludge thickening tank, and the transducer of the ultrasonic oscillator is embedded in the inner wall of the sludge thickening tank. An agitator is installed at the top of the sludge thickening tank. The sludge thickening tank is connected to the sludge discharge port of the sedimentation tank through a screw pump. The inlet of the sedimentation tank is connected to the sludge discharge port of the catalytic oxidation tank. The filtrate outlet of the plate and frame filter press is connected to the inlet of the pH adjustment tank through a pipeline. The feed inlet of the plate and frame filter press is connected to the bottom of the sludge thickening tank through a high-pressure hose.

[0013] Preferably, the sedimentation tank is equipped with inclined plate packing, the inclination angle of the inclined plates is 60°, the plate spacing is 5-8cm, the inclined plate packing is made of polypropylene, the thickness is 0.8-1.2mm, the surface roughness Ra is 5-10μm, and the inclined plate packing is fixedly installed on the inner wall of the sedimentation tank by a slot.

[0014] Preferably, the clean water reuse tank is connected to the rinsing water inlet of the dyeing and finishing process via a reuse water pump, and another path of the reuse water pump is connected to the backwash pipe. The backwash pipe is equipped with a backwash water flow meter and a backwash water pressure gauge on its outer wall. The backwash water flow meter and the backwash water pressure gauge are connected to the controller via wireless communication technology. The clean water reuse tank is equipped with a residual chlorine detector and an activated carbon filter layer. The residual chlorine detector is fixedly installed at the outlet flange. The activated carbon filter layer is a 50cm thick columnar packing layer, and a stainless steel support mesh is installed at the bottom of the activated carbon filter layer.

[0015] Preferably, the pH sensor is connected to the controller via a signal converter, the controller is connected to the signal converter via a data cable, the signal converter is connected to the conductivity detector and the residual chlorine detector respectively, and the controller is connected to the ozone generator, the first metering pump, the first metering pump and the flow control valve via a data bus. The controller has a preset pH dynamic adjustment program. An intermediate water tank is set between the catalytic oxidation tank and the multi-stage adsorption filtration unit. The inlet of the intermediate water tank is connected to the outlet of the catalytic oxidation tank, and the outlet of the intermediate water tank is connected to the inlet of the multi-stage adsorption filtration unit through a booster pump. A liquid level sensor is installed inside the intermediate water tank, and the liquid level sensor is connected to the controller signal.

[0016] Preferably, the wastewater collection tank is equipped with a bar screen and a pre-aeration device. The pre-aeration device is located at the bottom of the wastewater collection tank, the bar screen is installed at an angle at the inlet end of the wastewater collection tank, and a vibration motor is installed below the bar screen. The bar screen spacing is 2-4mm. The pre-aeration device includes a microporous aeration head assembly and a Roots blower. The microporous aeration head assembly is distributed at the bottom of the wastewater collection tank with a spacing of 30cm between the microporous aeration heads. The microporous aeration head assembly is connected to the Roots blower for air supply through UPVC pipes, and the air-to-water ratio is 3:1-5:1.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention achieves gradient adsorption and purification of organic matter, heavy metal ions and color in wastewater through a multi-stage adsorption and filtration unit, solving the problems of low adsorption capacity and poor selectivity of single zeolite, and significantly reducing the frequency of material replacement and operating costs. 2. This invention combines an ultraviolet photocatalytic component with an ozone aeration disc to achieve efficient catalytic oxidation degradation of recalcitrant organic matter, solving the problems of high energy consumption and blind addition of oxidants in traditional catalytic oxidation processes, and effectively improving the decomposition efficiency of azo dyes in nylon dyeing and finishing wastewater. 3. This invention uses a membrane separation device connected to a catalytic oxidation tank to achieve water resource recycling, solves the problem of secondary pollution of concentrated water, and improves solid-liquid separation efficiency; 4. This invention achieves fully automated monitoring and control of the entire process from wastewater collection to clean water reuse through an automatic dosing device, solving the problems of slow dosing and acid / alkali waste in traditional manual dosing, and improving the stability of system operation. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall process flow of the system of the present invention; Figure 2 This is a schematic diagram of the multi-stage adsorption filtration unit structure of the present invention; Figure 3 This is a schematic diagram of the sludge treatment unit process flow of the present invention; Figure 4 This is a topology diagram of the automatic control system of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figure 1 , Figure 2 , Figure 3 and Figure 4 The present invention provides an embodiment of a dyeing and finishing wastewater treatment system based on the acid-controlled dyeing and finishing process of nylon fabric, comprising a wastewater collection tank, a pH adjustment tank, a catalytic oxidation tank, a multi-stage adsorption filtration unit, a membrane separation device, and a clean water reuse tank connected in sequence; the inlet of the wastewater collection tank is connected to the dyeing and finishing process drainage pipe, the outlet of the wastewater collection tank is connected to the inlet of the pH adjustment tank through a booster pump, the concentrated water outlet of the membrane separation device is connected to the inlet of the catalytic oxidation tank through a return pipe, and the clean water outlet of the membrane separation device is connected to the clean water reuse tank; The multi-stage adsorption filtration unit includes an activated carbon adsorption layer and a composite zeolite layer, which are stacked and connected in series. The composite zeolite layer is filled with a mixture of modified zeolite and nano-alumina particles. The modified zeolite in the composite zeolite layer is clinoptilolite treated with a silane coupling agent, and the particle size of the nano-alumina particles is 50-100 nm. The mass ratio of modified zeolite to nano-alumina is 3:1. The activated carbon adsorption layer is filled in a stainless steel mesh frame. The activated carbon in the activated carbon adsorption layer is coconut shell activated carbon with a particle size of 2-4 mm and a filling density of 400-600 kg / m³. A backwashing pipe is installed at the bottom of the activated carbon adsorption layer, and the backwashing cycle is 24-48 hours. An exhaust port is installed at the top of the multi-stage adsorption filtration unit, and the exhaust port is connected to the activated carbon adsorber. The activated carbon adsorber is filled with granular activated carbon with a particle size of 4-6 mm and a filling height of 50-80 cm. Furthermore, firstly, the drain valve of the dyeing and finishing process is opened for wastewater collection and pretreatment. The wastewater flows into the wastewater collection tank, where a 30° inclined grid with a 3mm spacing intercepts large-particle impurities such as fibers and dye particles. The vibration motor below starts every 15 minutes at a vibration frequency of 50Hz. The vibration of the eccentric wheel shakes off the grid-retained material to the collection hopper below. The Roots blower supplies air to the microporous aeration head group at an air-to-water ratio of 4:1. The 2mm diameter micropores generate bubbles with a diameter of 1-3mm. The wastewater is stirred evenly for 30 minutes to ensure uniform mixing and increase dissolved oxygen to 3-4mg / L. Then, pH adjustment and catalytic oxidation are performed. A booster pump pumps wastewater into the pH adjustment tank at a flow rate of 5 m³ / h. A pH sensor in the middle of the tank monitors the water quality in real time. When the pH value is detected to be below 6.5, the controller receives a signal and triggers the first metering pump at the bottom of the alkali storage tank. The first metering pump sprays a 10% NaOH solution into the pH adjustment tank through a spiral nozzle 20 cm from the bottom. The solution mixes with the wastewater under the action of a stirrer within the tank. Dosing stops when the pH value reaches 7.5. The adjusted wastewater enters the catalytic oxidation tank from the upper side of the pH adjustment tank. The controller simultaneously starts the hydrogen peroxide dosing device and the ozone generator. The germicidal lamps and the catalytic lamps of the ultraviolet photocatalytic assembly have a light transmittance of ≥90% through their external quartz sleeves. The wastewater is irradiated from a distance of 15 cm from the liquid surface. Titanium dioxide loaded on the surface of the 5 mm hexagonal porous honeycomb ceramic plate generates hydroxyl radicals under ultraviolet light excitation. The ozone released from the aeration holes of the ozone aeration disc forms an advanced oxidation system with hydrogen peroxide. The inlet and outlet are set diagonally to create a flow reaction, and the reaction residence time is 60 minutes. Finally, after adsorption filtration, membrane separation, and water reuse, the catalytically oxidized wastewater flows by gravity into the intermediate tank. When the level sensor detects that the water level reaches 2 / 3 of the tank, the booster pump pumps the wastewater into the multi-stage adsorption filtration unit at a flow rate of 8 m³ / h. First, the wastewater passes through an activated carbon adsorption layer composed of coconut shell activated carbon, flowing from top to bottom through a stainless steel mesh frame for 30 minutes. The bottom backwash pipe is activated every 24 hours, rinsing from bottom to top for 10 minutes with clean water at 1.5 times the treatment flow rate. Subsequently, it enters a composite zeolite layer composed of modified clinoptilolite and 50nm nano-alumina particles in a 3:1 ratio. The zeolite is modified by soaking in a silane coupling agent for 24 hours, increasing the specific surface area to 300 m² / g. The nanoparticles fill the pores of the zeolite, enhancing the adsorption of heavy metal ions. After filtration, the wastewater enters the membrane separation unit. The pleated polypropylene filter cartridge first removes particles ≥5μm. A differential pressure sensor monitors the filter cartridge differential pressure; when the differential pressure is ≥0.1MPa, an abnormal signal is transmitted to the controller. The controller's digital signal is converted to an alarm message displayed on the panel screen, prompting for replacement. The spiral wound nanofiltration membrane module separates the wastewater. The purified water flows through a PE pipe into the purified water reuse tank, while the concentrated water returns to the inlet of the catalytic oxidation tank at a flow rate of 2m³ / h via a return pipe. In the purified water tank, an activated carbon filter layer further adsorbs trace organic matter. A residual chlorine detector monitors the outlet water quality in real time. After receiving a compliance signal, the controller sends a signal to control the reuse water pump to deliver the water to the dyeing and finishing rinsing process at a flow rate of 10m³ / h.

[0021] Please see Figure 1 , Figure 2 and Figure 4 An embodiment of the present invention provides a dyeing and finishing wastewater treatment system based on the acid-controlled dyeing and finishing process of nylon fabric, wherein a pH sensor is provided in the middle of the side of the inner wall of the pH adjustment tank, and an automatic dosing device is provided at the top of the inner wall of the pH adjustment tank. The automatic dosing device includes an alkali storage tank and an acid storage tank. The bottom of the alkali storage tank is connected to the dosing port of the pH adjustment tank via a first metering pump. The end of the alkali dosing pipe connected to the dosing port is equipped with a spiral nozzle. The alkali dosing pipe extends 20cm above the bottom of the pH adjustment tank. The bottom of the acid storage tank is connected to the inlet of the catalytic oxidation tank via a second metering pump. A sludge treatment unit is installed downstream of the sludge discharge port of the catalytic oxidation tank. The sludge treatment unit includes a sedimentation tank, a sludge thickening tank, and a plate and frame filter press. An ultrasonic oscillator is installed at the bottom of the sludge thickening tank, and the transducer of the ultrasonic oscillator is embedded in the inner wall of the sludge thickening tank. An agitator is installed at the top of the sludge thickening tank. The sludge thickening tank is connected to the sludge discharge port of the sedimentation tank through a screw pump. The inlet of the sedimentation tank is connected to the sludge discharge port of the catalytic oxidation tank. The filtrate outlet of the plate and frame filter press is connected to the inlet of the pH adjustment tank through a pipeline. The feed port of the plate and frame filter press is connected to the bottom of the sludge thickening tank through a high-pressure hose. Furthermore, firstly, when the ultrasonic level gauge installed at the top of the wastewater collection tank detects that the liquid level has reached 80% of the total height of the tank, the analog signal output by the ultrasonic level gauge is transmitted to the controller via a shielded cable. The controller's built-in logic program immediately executes the following steps: 1. Signal verification: Three consecutive times, with a 10-second interval between each time, to confirm that the liquid level signal is stable within the range of 80%±2% to avoid false triggering; 2. Equipment self-check: The status of the booster pump is queried via the MODBUS protocol; 3. Execution: The controller sends a start command to the frequency converter, which is directly connected to the booster pump. The frequency converter gradually increases the frequency from 5Hz to 50Hz to avoid starting current surges. At the same time, it outputs a switch signal to the indicator light on the booster pump control cabinet, opening the electric valve on the pipeline between the wastewater collection tank and the pH adjustment tank. The valve position feedback signal is returned to the controller via a limit switch. This allows the controller to control the booster pump to automatically input wastewater into the pH adjustment tank. The pH sensor in the middle of the inner wall of the pH adjustment tank collects data every 10 seconds, and the signal is transmitted to the controller via a signal converter. If the initial wastewater pH is 5.2 (commonly acidic in nylon dyeing and finishing wastewater), the controller invokes the preset dynamic pH adjustment program to calculate the required amount of NaOH solution to be added: the first metering pump is started, and the alkali solution is delivered through a DN25 dosing pipe to a spiral nozzle 20cm above the bottom of the tank, forming an atomized spray. Three sets of agitators inside the tank operate synchronously, with a 50cm spacing between the upper and lower layers of each set, ensuring thorough mixing of the solution and wastewater. When the pH sensor reading stabilizes at 7.8 (the optimal pH range for catalytic oxidation), the metering pump automatically stops; the adjustment process takes approximately 15 minutes. Then, the adjusted wastewater flows into the upper inlet of the catalytic oxidation tank. At this time, the controller calculates the dosage ratio of hydrogen peroxide and ozone using a PID algorithm based on the real-time influent COD value and the ORP value of the reaction system input from the online COD detector. When the ORP value rises to +600mV, the controller adjusts the hydrogen peroxide dosing pump frequency from 40Hz to 50Hz, and simultaneously increases the ozone generator power from 80% to 100%. The UV lamps of the UV photocatalytic component continuously irradiate the tank, and the quartz sleeve is cleaned weekly with a soft brush to ensure light transmittance. The aeration holes of the ozone aeration disc, fixed to the bottom of the tank and 10cm from the tank wall, alternate aeration at 0.5-second intervals, forming a pulsed ozone release. A baffle plate, with a diameter of 1 / 2 the tank body and 20cm from the aeration disc, prevents the water flow from directly impacting the tank wall, forcing the wastewater to form a circulation and extending the ozone contact time to 45 minutes. Finally, the wastewater after catalytic oxidation flows into the intermediate water tank through the DN100 outlet at the bottom of the tank. A level sensor in the wastewater tank monitors the water level in real time. When the water level is below 20%, the booster pump automatically stops upon receiving a limiting signal; when it is above 80%, an alarm prompts the front-end treatment equipment to reduce its speed. The controller synchronously collects data from the pH sensor, COD analyzer, and ORP analyzer to generate a real-time process curve. If the COD removal rate after catalytic oxidation is detected to be below 60% for three consecutive times, the cleaning procedure for the UV lamp assembly and ozone aeration disc is automatically triggered: the power is turned off, the UV components are disassembled through the flange at the bottom of the support, and the surface of the honeycomb ceramic plate is rinsed with deionized water to remove any adhering substances; the ozone aeration disc is then purged with compressed air through the backwash pipe for 10 minutes.

[0022] Please see Figure 1 , Figure 2 and Figure 3 The present invention provides an embodiment of a dyeing and finishing wastewater treatment system based on acid-controlled dyeing and finishing process of nylon fabric. The membrane separation device includes a spiral nanofiltration membrane module and a porous central tube. The membrane of the spiral nanofiltration membrane module is spirally wound around the outer wall of the porous central tube. A flow control valve is fixedly installed at the concentrate outlet of the spiral nanofiltration membrane module. A transparent detection tube section is provided at the front end of the flow control valve. A conductivity meter is installed inside the transparent detection tube section. The clean water outlet is connected to a PE pipe. The inlet of the membrane separation device is equipped with a security filter. The filter element of the security filter is a pleated polypropylene filter element with a filtration accuracy of 5-10μm. A differential pressure sensor is installed on the outside of the filter element. The membrane pore size is 1-4nm and the operating pressure is 0.8-1.5Mpa. The membrane separation device is equipped with a protective shell. A shock-absorbing buffer layer is installed between the protective shell and the spiral wound nanofiltration membrane module. The catalytic oxidation tank is equipped with an ultraviolet photocatalytic component and an ozone aeration plate. The ultraviolet photocatalytic component consists of an ultraviolet lamp group and a honeycomb ceramic plate. The ultraviolet lamp group is covered with a quartz sleeve. The ultraviolet lamp group includes a germicidal lamp with a main wavelength of 254nm and a catalytic lamp with a main wavelength of 365nm. The ratio of germicidal lamps to catalytic lamps is 2:1. The outer wall of the honeycomb ceramic plate is loaded with titanium dioxide and the honeycomb ceramic plate is set with a hexagonal channel structure. The ozone aeration plate is connected to an external gas source through an ozone generator. The ozone aeration disc has a pore diameter of 0.5-1mm, arranged in a ring array. The ozone aeration disc is fixedly installed at the bottom of the inner wall of the catalytic oxidation tank. A baffle is installed 20cm above the ozone aeration disc. The ultraviolet photocatalytic component is fixed to the inner wall of the catalytic oxidation tank by a bracket. The bracket suspends the ultraviolet photocatalytic component 10-20cm above the liquid surface. The bottom of the bracket is detachably connected to the inner wall of the catalytic oxidation tank by a flange. The inlet of the catalytic oxidation tank is located at the upper part of one side of the tank body, and the outlet is located at the lower part of the other side of the tank body. The inlet and outlet are arranged diagonally. A hydrogen peroxide dosing device is installed at the inlet of the catalytic oxidation tank. The dosing pump of the hydrogen peroxide dosing device and the power control terminal of the ozone generator are respectively connected to the controller. The controller dynamically adjusts the addition ratio of hydrogen peroxide and ozone based on the COD value of the influent and the ORP value of the reaction system. Furthermore, firstly, a pneumatic butterfly valve is installed at the front end of the exhaust port, which is vertically installed at the center of the top of the multi-stage adsorption filtration unit, and a rain cap is added to the outlet end. Wastewater lifted from the intermediate pool enters the multi-stage adsorption filtration unit. The top exhaust port is opened for 30 seconds, allowing air inside the unit to be naturally expelled by gravity and pre-pressurization by the water flow. This prevents air resistance caused by air in the pores of the activated carbon adsorption layer and the composite zeolite layer, which could lead to uneven water flow distribution. The wastewater first contacts the activated carbon adsorption layer: a stainless steel mesh frame filled with coconut shell activated carbon at a density of 600 kg / m³, forming a filter layer with a porosity of 45%. Wastewater flows from top to bottom at a filtration rate of 0.5 m / h. The micropores on the surface of activated carbon adsorb dye molecules and organic matter. After 24 hours of operation, backwashing is started: the inlet valve is closed, the backwash pipe valve is opened, and the recycled water from the clean water reuse tank is flushed in the reverse direction from the bottom backwash pipe at a flow rate of 15 m³ / h and a water flow speed of 2 m / s for 15 minutes to flush the trapped impurities to the sewage ditch. After the backwashing is completed, the exhaust port is opened again for 5 seconds to balance the pressure. Then, the wastewater adsorbed by activated carbon enters the upper composite zeolite layer. Modified clinoptilolite is treated with silane coupling agent KH-550: the zeolite is soaked in a 5% concentration of the coupling agent ethanol solution, stirred in a 60℃ water bath for 2 hours, filtered, and dried at 100℃ for 4 hours. Amino groups are grafted onto the surface, increasing the adsorption capacity for heavy metal ions such as Cu²+ and Zn²+ by 40%. Nano-alumina particles and modified zeolite are mixed at a mass ratio of 3:1 in a mixer for 30 minutes and uniformly filled into the filter layer. Wastewater passes through from bottom to top; the ion exchange of the zeolite and the surface adsorption of the nanoparticles synergistically remove residual pollutants, with a residence time of 20 minutes. An activated carbon adsorber connected to the top exhaust port operates synchronously, adsorbing a small amount of volatile organic waste gas during the filtration process. The activated carbon is replaced quarterly. Finally, the filtered wastewater enters the membrane separation unit through pipelines. It first passes through a security filter, monitored in real-time by a differential pressure sensor on the outside of the filter element. When the differential pressure reaches 0.2 MPa, a replacement signal is issued. The wastewater then enters the spiral-wound nanofiltration membrane module at a pressure of 1.0 MPa. The membrane sheet is spirally wound around the porous central tube, forming a filtration unit with a flow channel width of 0.8 mm. The flow control valve at the concentrate outlet adjusts its opening based on conductivity meter data: when the concentrate conductivity is ≥1500 μS / cm, the valve opening remains at 80%, and the concentrate is returned to the catalytic oxidation tank at a rate of 3 m³ / h; when it is below 1000 μS / cm, the opening is adjusted to 60% to reduce return flow. An online turbidity meter is installed on the PE pipeline at the clean water outlet. If the measured value is <0.5 NTU, it meets the standard and enters the clean water reuse tank; otherwise, it automatically switches to the backwash process, flushing the membrane surface with clean water at 1.5 times the operating flow rate for 10 minutes to restore membrane flux.

[0023] Please see Figure 1 , Figure 3 and Figure 4 The present invention provides an embodiment of a dyeing and finishing wastewater treatment system based on the acid-controlled dyeing and finishing process of nylon fabric. The sedimentation tank is equipped with inclined plate packing. The inclined plate inclination angle is 60° and the plate spacing is 5-8cm. The inclined plate packing is made of polypropylene with a thickness of 0.8-1.2mm and a surface roughness Ra of 5-10μm. The inclined plate packing is fixedly installed on the inner wall of the sedimentation tank by a slot. The clean water reuse tank is connected to the rinsing water inlet of the dyeing and finishing process via a reuse water pump. Another path of the reuse water pump is connected to the backwash pipe. The backwash pipe is equipped with a backwash water flow meter and a backwash water pressure gauge on its outer wall. The backwash water flow meter and the backwash water pressure gauge are connected to the controller via wireless communication technology. The clean water reuse tank is equipped with a residual chlorine detector and an activated carbon filter layer. The residual chlorine detector is fixedly installed at the outlet flange. The activated carbon filter layer is a 50cm thick columnar packing layer, and a stainless steel support mesh is installed at the bottom of the activated carbon filter layer. Furthermore, firstly, solid-liquid separation is achieved in the sedimentation tank. The sludge discharge port of the catalytic oxidation tank, located at the center of the tank bottom, is opened periodically, once a day for 10 minutes each time, to discharge sludge-containing wastewater into the sedimentation tank. The inclined plate packing inside the tank is installed at a 60° angle with a plate spacing of 6cm, and is fixed to the tank wall using slots. Wastewater flows into the sedimentation tank from the lower inlet, rises along the channels between the inclined plates, and the flow velocity is controlled at 0.3mm / s. The sludge particles, mainly titanium dioxide catalytic residue and organic flocculants, slide down the surface of the inclined plates to the bottom of the tank under gravity, improving the separation efficiency by 30% compared to traditional horizontal flow sedimentation tanks. The inclined plates are manually cleaned monthly, using a high-pressure water gun to wash away sediment and prevent clogging. Then, the sludge discharge pipe with a pneumatic diaphragm valve at the bottom of the sedimentation tank is opened every 2 hours to pump the sludge into the sludge thickening tank. An ultrasonic oscillator embedded at the bottom of the tank runs for 30 minutes and stops for 10 minutes, breaking up the sludge flocs through cavitation and promoting water release. A top agitator continuously stirs the sludge to prevent sedimentation. During the thickening process, the sludge moisture content decreases from 98% to 95%. When the tank level reaches 80%, a screw pump is started to transport the sludge to a plate and frame filter press. Before feeding into the filter press, a 0.1% polyacrylamide solution is added to the thickening tank at a rate of 5 kg / m³ of sludge, and the mixture is stirred for 15 minutes to improve sludge dewatering performance. Finally, after the plate and frame filter press is started, the high-pressure hose pumps the conditioned sludge into the filter chamber. When the feed pressure reaches 0.8 MPa, feeding is stopped, and the pressure is maintained for 30 minutes. Monofilament polyester fiber filter cloth intercepts sludge particles, and the filtrate passes through the filter cloth and flows into the pipeline through the filtrate outlet. A solenoid valve switches the flow directly back to the pH adjustment tank inlet. When the filtrate exceeds the standard, the controller receives the signal and switches the solenoid valve, discharging the excess filtrate into the wastewater collection tank. After filtration is complete, the filter plates are loosened, and a mechanical scraper automatically removes the sludge cake, which is then collected and transported for disposal. Each batch of filtration takes 2 hours. The filter cloth is rinsed weekly with a neutral detergent to prevent clogging.

[0024] Please see Figure 1 , Figure 3 and Figure 4 An embodiment of the present invention provides a dyeing and finishing wastewater treatment system based on acid-controlled dyeing and finishing process of nylon fabric. The wastewater collection tank is equipped with a bar screen and a pre-aeration device. The pre-aeration device is located at the bottom of the wastewater collection tank. The bar screen is installed at an inclination at the inlet end of the wastewater collection tank. A vibration motor is installed below the bar screen. The bar screen spacing is 2-4mm. The pre-aeration device includes a microporous aeration head assembly and a Roots blower. The microporous aeration head assembly is distributed at the bottom of the wastewater collection tank with a spacing of 30cm between the microporous aeration heads. The microporous aeration head assembly is connected to the Roots blower for air supply through a UPVC pipe, and the air-to-water ratio is 3:1-5:1. The pH sensor is connected to the controller via a signal converter, the controller is connected to the signal converter via a data cable, the signal converter is connected to the conductivity detector and the residual chlorine detector respectively, and the controller is connected to the ozone generator, the first metering pump and the flow control valve via a data bus. The controller has a preset pH dynamic adjustment program. An intermediate water tank is set between the catalytic oxidation tank and the multi-stage adsorption filtration unit. The inlet of the intermediate water tank is connected to the outlet of the catalytic oxidation tank, and the outlet of the intermediate water tank is connected to the inlet of the multi-stage adsorption filtration unit through a booster pump. A liquid level sensor is installed inside the intermediate water tank, and the liquid level sensor is connected to the controller signal. Furthermore, firstly, the purified water from the membrane separation unit enters the purified water reuse tank. A 50cm thick columnar activated carbon filter layer is supported by a stainless steel support mesh at the bottom of the tank. Wastewater flows from bottom to top, with a residence time of 15 minutes, further adsorbing residual trace dyes and disinfection byproducts. A residual chlorine detector at the outlet flange monitors the flow in real time. When the detected value is >0.5mg / L, the controller initiates the backwashing procedure for the activated carbon filter layer: the backwashing pipe valve at the bottom of the tank is opened, and recycled water is used to flush the filter for 20 minutes at 1.2 times the treatment flow rate, removing excess residual chlorine and adsorbents from the activated carbon surface. Then, two reclaimed water pumps are installed in the clean water reuse tank. The main pump is connected to the rinsing water inlet of the dyeing and finishing process via a DN100 pipe. An electromagnetic flow meter and pressure sensor are installed on the pipe to monitor the reclaimed water volume and pressure in real time. Another backwash pipe is connected to the backwash port of the activated carbon adsorption layer of the multi-stage adsorption filtration unit. The backwash water flow meter and pressure gauge on the pipeline transmit data to the controller via a wireless communication module. When the activated carbon adsorption layer needs backwashing, the controller switches the water pump valve. The differential pressure sensor triggers the controller to prioritize the backwashing requirement. After backwashing is completed, the controller closes the backwash butterfly valve and keeps the water pump running for 30 seconds to drain the residual flushing water in the pipeline. After the valve switches back to its original position, the system can be restored to reuse mode. Finally, the controller integrates all sensor signals: the bar screen vibration motor and pre-aeration fan in the wastewater collection tank; the dosing pump and agitator in the pH adjustment tank; the UV lamp and ozone generator in the catalytic oxidation tank; the level sensor in the intermediate water tank; the backwash valve of the multi-stage adsorption filtration unit; the flow control valve and conductivity meter of the membrane separation unit; and the residual chlorine detector in the clear water reuse tank, all connected via an RS485 bus. The operating interface displays the operating parameters of each unit in real time and has preset alarm thresholds: when the ORP value of the catalytic oxidation tank is <+400mV for more than 10 minutes, or the pressure difference of the membrane separation unit is >0.3MPa, the system automatically triggers an audible and visual alarm and suspends water intake, while simultaneously sending an SMS to the administrator's mobile phone. Daily operating reports are automatically generated, recording data such as treated water volume, reagent consumption, and equipment operating time, with a storage period of one year. The system performs automatic calibration weekly: the pH sensor is calibrated using a standard buffer solution.

[0025] Working principle: First, dyeing and finishing wastewater enters the wastewater collection tank through the drain pipe. A screen in the tank removes larger solid impurities, and a pre-aeration device aerates the wastewater through microporous aerators, performing preliminary mixing and pretreatment. Afterward, the wastewater is pumped to the pH adjustment tank. In the pH adjustment tank, a pH sensor monitors the acidity and alkalinity of the wastewater in real time. Based on the monitoring data, the controller activates an automatic dosing device to add chemicals to the tank through either an alkali or acid storage tank, adjusting the pH value of the wastewater to a suitable range for catalytic oxidation. Then, the pH-adjusted wastewater enters the catalytic oxidation tank. Ozone is released from the ozone aeration discs within the tank, while simultaneously, the ultraviolet lamps in the ultraviolet photocatalytic component work synergistically with the titanium dioxide-loaded honeycomb ceramic plate. Under the combined catalytic oxidation of ultraviolet light and ozone, the organic pollutants in the wastewater are decomposed and degraded. The treated wastewater then enters a multi-stage adsorption filtration unit, first passing through an activated carbon adsorption layer to adsorb organic impurities and odors, and then further adsorbing heavy metal ions and other pollutants through a composite zeolite layer. Finally, the wastewater after adsorption filtration enters the membrane separation unit, where it is separated by a spiral wound nanofiltration membrane module. The purified water flows into the purified water reuse tank through the purified water outlet; the concentrated water returns to the catalytic oxidation tank through the return pipe for further treatment. The sludge produced in the catalytic oxidation tank enters the sludge treatment unit through the sludge discharge port, where it is treated by a sedimentation tank, a sludge thickening tank, and a plate and frame filter press. The filtrate is returned to the pH adjustment tank for further recycling.

[0026] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A wastewater treatment system for dyeing and finishing processes based on acid-controlled dyeing and finishing of nylon fabrics, characterized in that: It includes a wastewater collection tank, a pH adjustment tank, a catalytic oxidation tank, a multi-stage adsorption filtration unit, a membrane separation device, and a clean water reuse tank connected in sequence. The inlet of the wastewater collection tank is connected to the dyeing and finishing process drainage pipe, the outlet of the wastewater collection tank is connected to the inlet of the pH adjustment tank through a booster pump, the concentrated water outlet of the membrane separation device is connected to the inlet of the catalytic oxidation tank through a return pipe, and the clear water outlet of the membrane separation device is connected to the clear water reuse tank. The multi-stage adsorption filtration unit includes an activated carbon adsorption layer and a composite zeolite layer, which are stacked and connected in series. The composite zeolite layer is filled with a mixture of modified zeolite and nano-alumina particles. A pH sensor is installed in the middle of the inner wall side of the pH adjustment tank, and an automatic dosing device is installed at the top of the inner wall of the pH adjustment tank. The automatic dosing device includes an alkali storage tank and an acid storage tank. The bottom of the alkali storage tank is connected to the dosing port of the pH adjustment tank via a first metering pump. The end of the alkali dosing pipe connected to the dosing port is equipped with a spiral nozzle. The alkali dosing pipe extends 20cm above the bottom of the pH adjustment tank. The bottom of the acid storage tank is connected to the inlet of the catalytic oxidation tank via a second metering pump. The catalytic oxidation tank is equipped with an ultraviolet photocatalytic component and an ozone aeration plate. The ultraviolet photocatalytic component consists of an ultraviolet lamp group and a honeycomb ceramic plate. The ultraviolet lamp group is covered with a quartz sleeve. The ultraviolet lamp group includes a germicidal lamp with a main wavelength of 254nm and a catalytic lamp with a main wavelength of 365nm. The ratio of germicidal lamps to catalytic lamps is 2:

1. The outer wall of the honeycomb ceramic plate is loaded with titanium dioxide and the honeycomb ceramic plate is set with a hexagonal channel structure. The ozone aeration plate is connected to an external gas source through an ozone generator. The ozone aeration disc has a pore diameter of 0.5-1mm, arranged in a ring array. The ozone aeration disc is fixedly installed at the bottom of the inner wall of the catalytic oxidation tank. A baffle is installed 20cm above the ozone aeration disc. The ultraviolet photocatalytic component is fixed to the inner wall of the catalytic oxidation tank by a bracket. The bracket suspends the ultraviolet photocatalytic component 10-20cm above the liquid surface. The bottom of the bracket is detachably connected to the inner wall of the catalytic oxidation tank by a flange. The inlet of the catalytic oxidation tank is located at the upper part of one side of the tank body, and the outlet is located at the lower part of the other side of the tank body. The inlet and outlet are arranged diagonally. A hydrogen peroxide dosing device is installed at the inlet of the catalytic oxidation tank. The dosing pump of the hydrogen peroxide dosing device and the power control terminal of the ozone generator are respectively connected to the controller. The controller dynamically adjusts the addition ratio of hydrogen peroxide and ozone based on the COD value of the influent and the ORP value of the reaction system. The modified zeolite in the composite zeolite layer is clinoptilolite treated with a silane coupling agent, and the particle size of the nano-alumina particles is 50-100 nm. The mass ratio of modified zeolite to nano-alumina is 3:

1. The activated carbon adsorption layer is filled in a stainless steel mesh frame. The activated carbon in the activated carbon adsorption layer is coconut shell activated carbon with a particle size of 2-4 mm and a filling density of 400-600 kg / m³. A backwashing pipe is installed at the bottom of the activated carbon adsorption layer, and the backwashing cycle is 24-48 hours. An exhaust port is installed at the top of the multi-stage adsorption filtration unit, and the exhaust port is connected to the activated carbon adsorber. The activated carbon adsorber is filled with granular activated carbon with a particle size of 4-6 mm and a filling height of 50-80 cm. A sludge treatment unit is installed downstream of the sludge discharge port of the catalytic oxidation tank. The sludge treatment unit includes a sedimentation tank, a sludge thickening tank, and a plate and frame filter press. An ultrasonic oscillator is installed at the bottom of the sludge thickening tank, and the transducer of the ultrasonic oscillator is embedded in the inner wall of the sludge thickening tank. An agitator is installed at the top of the sludge thickening tank. The sludge thickening tank is connected to the sludge discharge port of the sedimentation tank through a screw pump. The inlet of the sedimentation tank is connected to the sludge discharge port of the catalytic oxidation tank. The filtrate outlet of the plate and frame filter press is connected to the inlet of the pH adjustment tank through a pipeline. The feed port of the plate and frame filter press is connected to the bottom of the sludge thickening tank through a high-pressure hose. The wastewater collection tank is equipped with a screen and a pre-aeration device. The pre-aeration device is located at the bottom of the wastewater collection tank. The screen is installed at an angle at the inlet end of the wastewater collection tank. A vibration motor is installed below the screen. The screen spacing is 2-4mm. The pre-aeration device includes a microporous aeration head assembly and a Roots blower. The microporous aeration head assembly is distributed at the bottom of the wastewater collection tank with a spacing of 30cm between the microporous aeration heads. The microporous aeration head assembly is connected to the Roots blower for air supply through UPVC pipes, and the air-to-water ratio is 3:1-5:

1.

2. The dyeing and finishing wastewater treatment system based on the acid-controlled dyeing and finishing process of nylon fabric according to claim 1, characterized in that: The membrane separation device includes a spiral-wound nanofiltration membrane module and a porous central tube. The membrane of the spiral-wound nanofiltration membrane module is spirally wound around the outer wall of the porous central tube. A flow control valve is fixedly installed at the concentrate outlet of the spiral-wound nanofiltration membrane module. A transparent detection tube section is provided at the front end of the flow control valve. A conductivity meter is installed inside the transparent detection tube section. The clean water outlet is connected to a PE pipe. The inlet of the membrane separation device is equipped with a security filter. The filter element of the security filter is a pleated polypropylene filter element with a filtration accuracy of 5-10μm. A differential pressure sensor is installed on the outside of the filter element. The membrane pore size is 1-4nm and the operating pressure is 0.8-1.5Mpa. The membrane separation device is equipped with a protective shell. A shock-absorbing buffer layer is installed between the protective shell and the spiral wound nanofiltration membrane module.

3. The dyeing and finishing wastewater treatment system based on the acid-controlled dyeing and finishing process of nylon fabric according to claim 1, characterized in that: The sedimentation tank is equipped with inclined plate packing. The inclined plate inclination angle is 60° and the plate spacing is 5-8cm. The inclined plate packing is made of polypropylene with a thickness of 0.8-1.2mm and a surface roughness Ra of 5-10μm. The inclined plate packing is fixedly installed on the inner wall of the sedimentation tank by a slot.

4. The dyeing and finishing wastewater treatment system based on the acid-controlled dyeing and finishing process of nylon fabric according to claim 1, characterized in that: The clean water reuse tank is connected to the rinsing water inlet of the dyeing and finishing process via a reuse water pump. Another path of the reuse water pump is connected to the backwash pipe. The backwash pipe is equipped with a backwash water flow meter and a backwash water pressure gauge on its outer wall. The backwash water flow meter and the backwash water pressure gauge are connected to the controller via wireless communication technology. The clean water reuse tank is equipped with a residual chlorine detector and an activated carbon filter layer. The residual chlorine detector is fixedly installed at the outlet flange. The activated carbon filter layer is a 50cm thick columnar packing layer, and a stainless steel support mesh is installed at the bottom of the activated carbon filter layer.

5. The dyeing and finishing wastewater treatment system based on the acid-controlled dyeing and finishing process of nylon fabric according to claim 1, characterized in that: The pH sensor is connected to the controller via a signal converter, the controller is connected to the signal converter via a data cable, the signal converter is connected to the conductivity detector and the residual chlorine detector respectively, and the controller is connected to the ozone generator, the first metering pump and the flow control valve via a data bus. The controller has a preset pH dynamic adjustment program. An intermediate water tank is set between the catalytic oxidation tank and the multi-stage adsorption filtration unit. The inlet of the intermediate water tank is connected to the outlet of the catalytic oxidation tank, and the outlet of the intermediate water tank is connected to the inlet of the multi-stage adsorption filtration unit through a booster pump. A liquid level sensor is installed inside the intermediate water tank, and the liquid level sensor is connected to the controller signal.

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