Digital printing guide belt sewage treatment system and method

Abstract

The application provides a digital printing guide belt sewage treatment system and method, adopts a closed loop recycling system, improves the recycling rate of guide belt cleaning water, and greatly reduces the water cost of enterprises. The synergistic purification process can effectively remove dyes, slurry and suspended solids in the sewage. After purification, the water quality is clear, and the pH value is stable in the neutral interval of 6-8. It completely meets the reuse requirements of guide belt cleaning and slurry configuration, and breaks through the industry bottleneck of poor purification effect and unreusable of the existing process. The physical + chemical dual deodorization technology can 100% inhibit the reproduction of anaerobic bacteria, completely eliminate the generation of hydrogen sulfide and other foul-smelling gases, and the unorganized emission of foul-smelling gases in the production workshop completely meets the emission standard of foul-smelling pollutants, greatly improves the production operation environment, and protects the occupational health of front-line operators. The purified water can be used for guide belt cleaning and slurry configuration, two core production processes, forming a complete closed loop of "sewage generation-purification-reuse-disposal".

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a digital printing conveyor belt wastewater treatment system and method. Background Technology

[0002] Digital printing technology, with its advantages of personalized customization, low pollution, and high flexibility, has become the core development direction of the modern textile printing and dyeing industry. As the core load-bearing component of a digital printing machine, the surface cleanliness of the printing guide belt directly determines the printing accuracy and the quality of the finished fabric. After each batch of fabric is printed, it must be subjected to high-pressure water spraying combined with mechanical brushing to remove residual ink, paste, and fiber impurities from the surface of the guide belt. This process continuously generates a large amount of industrial wastewater containing organic dyes, polymer pastes, and suspended solids.

[0003] In the existing technologies of the industry, there are five major pain points that cannot be overcome in the treatment and reuse of wastewater from digital printing conveyor belts, which seriously restrict the green, low-cost and sustainable development of the industry:

[0004] 1. Extremely low water resource utilization rate and serious waste: The traditional conveyor belt cleaning process adopts a linear mode of "fresh water spraying once - sewage direct discharge". The daily water consumption of a single industrial-grade digital printing machine for conveyor belt cleaning can reach 5-10 tons, and the monthly water consumption of a large-scale production workshop exceeds 1,000 tons. The water resource utilization efficiency is less than 10%, which not only significantly increases the production cost of enterprises, but also completely fails to meet the national dual-carbon policy requirements of "water conservation and emission reduction".

[0005] 2. Inadequate wastewater purification processes fail to meet reuse requirements: Existing conventional wastewater treatment processes mostly employ a single flocculation and sedimentation model, which can only remove some large suspended particles in wastewater. It cannot effectively remove the color of reactive dyes, disperse dyes, and acid dyes, as well as high-molecular-weight colloidal impurities in printing pastes. The treated water is turbid, highly colored, and contains many residual impurities, making it only suitable for low-value applications such as factory floor washing. It cannot be reused in the core process of conveyor belt cleaning, and it certainly cannot meet the refined requirements of printing production.

[0006] 3. The wastewater exhibits severe odor pollution, seriously endangering the working environment and personnel health: The wastewater from conveyor belt cleaning contains a large amount of easily degradable organic matter such as organic dyes and slurries. When left stagnant, it rapidly breeds obligate anaerobic bacteria, whose metabolic process produces hydrogen sulfide, mercaptans, and other odorous gases with a strong rotten egg smell. These gases diffuse uncontrollably throughout the production workshop, strongly irritating the respiratory tract and eye mucous membranes of operators. Long-term exposure can cause occupational health damage. Furthermore, the emission of these odorous gases does not meet the environmental protection requirements of the "Odor Pollutant Emission Standard."

[0007] 4. Immense environmental compliance pressure makes it impossible to achieve zero wastewater discharge: The core indicators of wastewater treated by existing processes, such as chemical oxygen demand, ammonia nitrogen, and total nitrogen, are far below the direct discharge limits stipulated in the "Water Pollutant Discharge Standard for Textile Dyeing and Finishing Industry". Direct discharge by enterprises will face heavy environmental penalties or even production shutdowns and rectification. On the other hand, the investment in advanced treatment processes that meet the discharge standards is large and the operating costs are high, which is difficult for small and medium-sized digital printing enterprises to afford. The industry urgently needs a low-cost and compliant wastewater treatment path.

[0008] 5. Limited Wastewater Reuse Scenario and Lack of a Closed-Loop System: Current technologies, even when partially reusing treated wastewater, limit it to non-core processes like belt washing, achieving a reuse rate of less than 30%. This makes it impossible to integrate into the core production process of digital printing. The limitations of wastewater reuse scenarios mean companies still need to continuously replenish large amounts of fresh water while simultaneously generating and discharging wastewater. This prevents the achievement of a complete closed-loop water cycle of "generation-treatment-reuse-disposal," ultimately failing to address the root cause of wastewater discharge. Summary of the Invention

[0009] To address the technical problems existing in the prior art, the present invention provides the following technical solution:

[0010] On one hand, a digital printing conveyor belt wastewater treatment system is provided, including a circulating water tank, a conveyor belt digital printer cluster, a wastewater treatment filter press, and a treated clean water tank. The conveyor belt digital printer cluster has a built-in printing conveyor belt, wherein:

[0011] The circulating water tank has a built-in liquid level sensor and a pH online monitoring probe, which are used to temporarily store the return wastewater after the guide belt is cleaned;

[0012] The wastewater treatment filter press is an integrated chamber filter press, which has a flocculation reaction chamber, a frequency conversion stirring device, an activated carbon adsorption chamber, a filter press plate group and a supernatant collection chamber connected in sequence, for the flocculation purification and solid-liquid separation of wastewater.

[0013] The water tank is equipped with an antibacterial dosing port, a residual chlorine monitoring probe, and a liquid level control device, and is used to store purified water.

[0014] The circulating water tank, the belt digital printer cluster, the sewage treatment filter press, and the treated water tank are connected in sequence to the automatic control valve through corrosion-resistant industrial pipelines, forming a closed-loop water flow path of "cleaning-return-circulation-purification-reuse".

[0015] The water outlet of the water treatment tank is divided into two reuse branches. The first branch is a belt cleaning reuse branch connected to the belt digital printer cluster, and the second branch is a sizing process reuse branch connected to the digital printing sizing system.

[0016] Preferably, the system further includes a booster power unit, which comprises a pressure pump, a water pump, and a circulation pump. All three pumps are corrosion-resistant chemical centrifugal pumps equipped with a frequency converter control cabinet. The pressure pump is located at the outlet of the treated water tank and provides 0.3-0.5 MPa of booster power for the belt cleaning process. The water pump is located between the belt digital printer cluster and the circulation tank to transport the cleaned wastewater to the circulation tank. The circulation pump is located between the inlet and outlet of the circulation tank to drive the wastewater circulation.

[0017] Preferably, the digital printer cluster of the printing belt also has a built-in cleaning execution unit, which includes a spray pipe, a high-pressure atomizing nozzle and a brush roller; the high-pressure atomizing nozzle is evenly distributed above the printing belt, and the spray angle is at an angle of 30-60° with the surface of the printing belt; the brush roller is made of wear-resistant nylon material, which makes elastic contact with the surface of the printing belt, and the speed of the brush roller is linked and matched with the running speed of the printing belt.

[0018] Preferably, the digital printer cluster with a guide belt also has a built-in wastewater collection unit, which includes a wastewater tank, a water collection tray, and a guide pipe. The water collection tray covers the entire area below the printing guide belt and is used to collect wastewater after washing. The wastewater tank has a built-in stainless steel grid filter screen to filter fabric fibers and lint impurities in the wastewater. The guide pipe is used to guide the wastewater collected in the water collection tray to the wastewater tank.

[0019] Preferably, it also includes a circulating odor suppression unit, which includes a circulating pipeline and an automatic Kathon dosing device; the circulating pipeline connects the inlet and outlet of the circulating water tank to form a closed-loop sewage circulation path; the automatic Kathon dosing device is connected to the antibacterial dosing port of the treated water tank, and the automatic Kathon dosing device is signal-interlocked with the residual chlorine monitoring probe and the liquid level automatic control device for quantitative dosing of Kathon agent.

[0020] On the other hand, a method for treating wastewater from digital printing conveyor belts is provided, implemented based on the aforementioned wastewater treatment system for digital printing conveyor belts, including the following steps:

[0021] Wastewater recycling: The clean water in the treated water tank is pressurized and then transported to the digital printer cluster to spray and wash the printing guide belt. The wastewater after cleaning is collected and filtered and then transported to the circulating water tank. The water quality parameters of the wastewater in the circulating water tank are monitored in real time. When the water quality reaches the set threshold or the circulation cycle is completed, the wastewater is transported to the wastewater treatment filter press equipment.

[0022] Multi-stage wastewater purification: Wastewater output from the circulating water tank is sent into the flocculation reaction chamber of the wastewater treatment filter press equipment. With the cooperation of the variable frequency stirring device, the five-step purification process is executed in sequence to complete the flocculation, adsorption, sedimentation and solid-liquid separation of the wastewater, and obtain the purified supernatant and filter cake. The supernatant is transported to the treated clean water tank.

[0023] Dual antibacterial and deodorizing: In the entire process of sewage circulation and purification reuse, physical deodorization is achieved by driving the continuous circulation of sewage to increase the dissolved oxygen content, while chemical antibacterial and deodorizing are achieved by quantitatively adding Kathon preservative to the purified water in the treated water tank.

[0024] Zero-discharge reuse of purified water: The purified water in the treated water tank is fully reused in two ways. The first way is reused to the conveyor belt cleaning process to enter the next cycle. The second way is sent to the digital printing sizing process to replace tap water to prepare printing paste. The water in the paste is evaporated into water vapor in the fabric drying process, realizing zero discharge of liquid wastewater.

[0025] Preferably, in step S1, the water quality parameters are color and suspended solids concentration, with thresholds set as color exceeding 200 times and suspended solids concentration exceeding 500 mg / L; the circulation cycle is set to 3 days, during which the wastewater is driven at a speed of 8-12 m 3 The continuous circulation of the flow rate per hour keeps the dissolved oxygen content in the wastewater above 2 mg / L.

[0026] Preferably, in step S2, the five-step purification process is operated as follows:

[0027] Step 1: Pre-flocculation with quicklime. Add quicklime powder at 5-10 parts per ten thousand of the wastewater volume and stir continuously at 80 r / min for 10 minutes to adjust the pH of the wastewater to 9-10.

[0028] Step 2: Polyaluminum chloride as the main flocculator, add liquid polyaluminum chloride at a volume of 4-12 parts per ten thousand of the wastewater, and stir continuously for 10 minutes;

[0029] Step 3: Activated carbon adsorption and decolorization. Add 200-mesh powdered activated carbon at 5-15 parts per ten thousand of the wastewater volume and stir continuously for 15-20 minutes.

[0030] Step 4: Add 0.1% polyacrylamide liquid at a concentration of 4-10% of the wastewater volume, reduce the stirring speed to 30r / min and stir slowly for 5 minutes, then stop stirring.

[0031] Step 5: Alum-assisted coagulation and sedimentation. Add alum powder at a volume of 1 / 10,000 to 8 parts per ten thousand of the wastewater, stir continuously for 10 minutes, and then let it stand for 30 to 40 minutes to settle. Finally, the pH value of the supernatant will stabilize at 6 to 8.

[0032] Preferably, in step S3, the dosage of Kathon preservative is 1-8 parts per ten thousand of the volume of purified water, and the antibacterial effect after addition is not less than 3 days, which matches the sewage circulation treatment cycle.

[0033] Preferably, in step S4, the two-way reuse ratio of purified water is: 70% of the purified water is reused in the first channel to the conveyor belt cleaning process, and 30% of the purified water is reused in the second channel to the digital printing sizing process; the drying temperature of the fabric drying process is 120-150℃.

[0034] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0035] This application represents a comprehensive technological breakthrough, bringing significant economic, environmental, and social benefits, as detailed below:

[0036] 1. Completely solve the problem of serious water waste and achieve ultimate water conservation: The closed-loop recycling system of this application increases the recycling rate of belt cleaning water to 100% and reduces the amount of fresh water replenishment by more than 90%; large-scale production workshops can save more than 900 tons of water resources per month, significantly reducing the company's water costs and fully complying with the national water conservation and emission reduction policy requirements.

[0037] 2. Overcoming the shortcomings of poor wastewater purification effect and achieving deep purification and reuse: The five-step synergistic purification process can effectively remove dyes, slurries, and suspended solids from wastewater, with a decolorization rate of ≥95% and a suspended solids removal rate of ≥98%. The purified water is clear and the pH value is stable in the neutral range of 6-8, which fully meets the reuse requirements of conveyor belt cleaning and slurry preparation, and breaks through the industry bottleneck of poor purification effect and inability to reuse existing processes.

[0038] 3. Overcoming the shortcomings of odor pollution and achieving comprehensive improvement of the working environment: The dual physical and chemical deodorization technology can 100% inhibit the reproduction of anaerobic bacteria and completely eliminate the generation of odorous gases such as hydrogen sulfide. The fugitive odor gas emissions from the production workshop fully comply with the "Odor Pollutant Emission Standard", greatly improving the production working environment and protecting the occupational health of front-line operators.

[0039] 4. Addressing the shortcomings of high environmental compliance pressure and achieving zero wastewater discharge: This application breaks through the traditional mindset of "treatment to meet standards for discharge" by incorporating all purified water into the printing production process and achieving zero liquid wastewater discharge through drying and evaporation. This completely avoids the environmental compliance risks of wastewater discharge, eliminates the need for high-cost deep treatment equipment, and significantly reduces the environmental costs of small and medium-sized digital printing enterprises.

[0040] 5. Overcoming the shortcomings of single reuse scenarios and achieving a complete closed-loop cycle: The purified water can be used simultaneously for two core production processes: conveyor belt cleaning and slurry preparation. The reuse scenarios are fully covered, and the recycling rate is 100%. This forms a complete closed loop of "wastewater generation-purification-reuse-disposal", which completely solves the root cause problems of low reuse rate and wastewater discharge in existing technologies. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the system composition structure provided in the embodiment of the present invention;

[0043] Figure 2 This is a diagram of a wastewater treatment mechanism provided in an embodiment of the present invention. Detailed Implementation

[0044] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0045] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0046] In the embodiments of this invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning. Similarly, the terms "of," "corresponding (relevant)," and "corresponding" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning.

[0047] In this embodiment of the invention, sometimes a subscript such as W1 may be mistakenly written as a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0048] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0049] This application develops a digital printing conveyor belt wastewater treatment system and method, constructing a fully closed-loop industrial system of "conveyor belt cleaning - wastewater circulation - multi-stage purification - antibacterial deodorization - zero-discharge reuse", which completely breaks through the core bottleneck of existing technologies and realizes 100% recycling and zero-discharge treatment of conveyor belt wastewater.

[0050] Example 1: Processing System Composition

[0051] (I) Composition of the Digital Printing Conveyor Belt Wastewater Treatment System

[0052] This system adopts a modular integrated design to adapt to the continuous production needs of large-scale digital printing workshops. The core hardware includes core modules such as circulating water tank, conveyor belt digital printer cluster, sewage treatment filter press equipment, and treated clean water tank (the system also has other auxiliary facilities, which can be combined with existing facilities). Each module is connected to the automatic control valve through corrosion-resistant industrial pipelines to form a closed-loop water flow path.

[0053] 1. Core Hardware

[0054] like Figure 1 As shown, the processing system mainly includes the following facilities:

[0055] (1) Circulating water tank: Made of 304 stainless steel corrosion-resistant material, with a volume matching the daily wastewater production of 3 digital printing machines. It has a built-in liquid level sensor, pH online monitoring probe, and temperature sensor. Its core function is to temporarily store the return wastewater after the conveyor belt is cleaned, so as to achieve the homogenization and circulation of wastewater, provide a stable influent water quality for subsequent purification treatment, and provide a circulating carrier for the circulating odor suppression unit to prevent the growth of anaerobic bacteria when the wastewater is left to stand.

[0056] (2) Belt Digital Printer Cluster: Multiple industrial-grade belt digital printers (Belt Digital Printer 1, Belt Digital Printer 2, Belt Digital Printer 3, etc.) are installed. Each device integrates a printing belt, brush roller, and spray pipe. It is the source of wastewater and the core terminal for cleaning water reuse. Among them, the printing belt is made of food-grade polyurethane material and is used to carry the printing fabric to complete the digital inkjet printing operation; the brush roller is made of wear-resistant nylon material, which makes elastic contact with the surface of the belt and can rotate synchronously with the belt to dissolve the residual ink on the surface of the belt through mechanical brushing; the spray pipe is connected to the outlet of the pressure pump, which can spray the pressurized cleaning water evenly onto the surface of the belt to complete the mechanical rinsing of residual ink.

[0057] (3) Wastewater treatment filter press equipment: An integrated chamber filter press is adopted, which has a built-in flocculation reaction chamber, a variable frequency stirring device, an activated carbon adsorption chamber, a filter plate assembly, and a supernatant collection chamber. It is the core unit of wastewater purification. Its core function is to complete the flocculation, adsorption, sedimentation, and solid-liquid separation of wastewater through a five-step reagent dosing process, purifying high-concentration wastewater into reusable clean water, and at the same time pressing the flocculated sludge into sludge cakes with a water content of less than 60%, thereby achieving the reduction and compliant disposal of solid waste.

[0058] (4) Treatment water tank: Made of food-grade 304 stainless steel, with built-in antibacterial dosing port, residual chlorine monitoring probe and liquid level control device. Its core function is to store purified water, provide a stable water source for the conveyor belt cleaning and reuse and the sizing process reuse, and provide a chemical dosing medium for chemical antibacterial and deodorizing agents to ensure the stability of the water quality of reused water.

[0059] The wastewater from digital printing conveyor belts typically contains: reactive dye ink components, disperse dye pattern components, acid dye ink components, paste components, and other impurities.

[0060] The water circulation process for cleaning the digital printing conveyor belt in this application is as follows:

[0061] The cleaning water for the digital printing guide belt is sprayed onto the printing guide belt under the drive of a pressure pump. As the printing guide belt rotates and the brush rollers rotate, the residual ink on the printing guide belt is dissolved and washed away. The rinsing wastewater flows back into the wastewater tank, where it is pumped out again to rinse the guide belt. This cycle is repeated, and the wastewater gradually becomes more concentrated. When the wastewater reaches a certain level, it needs to be replaced with treated clean water for reuse. The wastewater needs to be purified to become clean water for recycling. The recycling of the guide belt cleaning water can save water resources. The clean water can also replace the tap water used to prepare the sizing process and evaporate into the air during the drying process of the fabric sizing process.

[0062] 2. Auxiliary facilities

[0063] (1) Boosting power unit: including pressure pump, water pump and circulation pump, all of which are corrosion-resistant chemical centrifugal pumps, and are equipped with frequency converter control cabinet to achieve precise control of flow and pressure. Among them, the pressure pump is set at the outlet of the treated water tank to provide a stable boosting power of 0.3-0.5MPa for the belt cleaning spray water, thereby improving the residual ink rinsing effect; the water pump is set between the sewage tank and the circulation tank to continuously transport the sewage after belt cleaning to the circulation tank, thereby realizing the circulation of sewage; the circulation pump is set between the inlet and outlet of the circulation tank to drive the sewage to circulate continuously, thereby achieving physical odor suppression.

[0064] (2) Cleaning execution unit: including spray pipe, high pressure atomizing nozzle, brush roller. The high pressure nozzle is evenly arranged above the guide belt, and the spray angle is 45° with the surface of the guide belt to ensure that the cleaning water fully covers the surface of the guide belt without dead corners. The speed of the brush roller is linked and matched with the running speed of the guide belt to realize the synergistic effect of mechanical brushing and water flushing, greatly improve the cleaning effect and reduce the consumption of clean water.

[0065] (3) Wastewater collection unit: including wastewater tank, water collection tray and diversion pipeline. The water collection tray is located below the guide belt and receives the wastewater after cleaning in the whole range. It flows into the wastewater tank through the diversion pipeline. The wastewater tank has a built-in stainless steel grid filter screen, which can filter out large particles such as fabric fibers and lint in the wastewater to avoid clogging subsequent pipelines and equipment.

[0066] (4) Circulating deodorization unit: including circulating pump, circulating pipeline, and automatic dosing device of Kathon. The circulating pipeline is connected to the inlet and outlet of the circulating water tank to form a closed-loop circulation path; the Kathon dosing device is connected to the treated water tank and can accurately control the amount of agent added to achieve physical + chemical dual antibacterial and deodorizing.

[0067] The entire system's water flow path forms a complete closed loop of "cleaning-return-circulation-purification-reuse", as detailed below:

[0068] The process involves: treating the clean water tank → pressurizing with a pressure pump → cleaning the guide belt spray pipe → high-pressure nozzles spraying onto the printing guide belt of the digital printer → brush rollers washing and dissolving residual ink on the guide belt surface → after cleaning, the wastewater flows into the wastewater tank through the collection tray and guide pipe under the guide belt → after being filtered by the grid filter, the wastewater is pumped to the circulating water tank → the water from the circulating water tank is sent to the wastewater treatment filter press to complete the five-step purification process → the purified water is returned to the treated clean water tank.

[0069] The purified water from the water treatment tank is divided into two reuse paths:

[0070] The first route is for cleaning and reuse, which is transported to the belt cleaning spray pipeline and the above-mentioned circulating rinsing process is repeated.

[0071] The second route is for sizing reuse, which is transported to the digital printing sizing process to replace tap water in preparing the printing paste. Finally, it is evaporated into water vapor through the fabric drying process, achieving zero emissions.

[0072] (II) Wastewater Treatment Mechanism

[0073] The core technical principles of this application revolve around four major innovations: "circular water conservation, multi-stage purification, dual deodorization, and zero-emission closed-loop". Combining the physicochemical properties of wastewater treatment agents with digital printing production processes, a complete technical system with synergistic effects has been formed, fundamentally solving the core defects of existing technologies.

[0074] 1. Principles of wastewater recycling technology

[0075] Based on the water-saving principle of "tiered water use and closed-loop reuse," the traditional linear mode of "single-use and discharge" for conveyor belt cleaning water is transformed into a closed-loop mode of "circulating flushing - concentration control - purification and regeneration - repeated reuse." After the conveyor belt cleaning water is sprayed and scrubbed, the concentration of dyes and slurries in the wastewater gradually increases. Before the concentration reaches the threshold that affects the cleaning effect, it is continuously circulated for conveyor belt rinsing, making full use of the tiered use value of the cleaning water. When the concentration reaches the threshold, it is sent to the purification equipment to be regenerated into clean water and re-enters the circulation system. This principle reduces the amount of fresh water replenishment from the source and maximizes the utilization of water resources.

[0076] 2. Principle of Five-Step Multi-Stage Wastewater Purification Technology

[0077] Based on the wastewater treatment principles of "stepwise flocculation, gradient adsorption, deep decolorization, and acid-base neutralization," and combined with the physicochemical properties of five agents, a synergistic deep purification system has been formed. The mechanisms of action and synergistic logic of each agent are as follows:

[0078] (1) Mechanism of pre-flocculation and alkali adjustment of quicklime: quicklime (CaO) undergoes hydrolysis reaction with water to produce calcium hydroxide. On the one hand, it increases the pH value of the wastewater, providing a suitable alkaline environment for subsequent flocculation reactions; on the other hand, calcium hydroxide colloidal particles can adsorb and encapsulate fine suspended solids and slurry colloids in the wastewater, forming preliminary flocs, while neutralizing the surface negative charge of dye molecules, reducing colloidal stability, and laying the foundation for subsequent deep flocculation and sedimentation.

[0079] (2) Electroneutralization flocculation mechanism of polyaluminum chloride: As an inorganic polymer flocculant, polyaluminum chloride (PAC) hydrolyzes in water to generate polynuclear hydroxy complexes. Through strong electroneutralization, it compresses the double electric layer of dye and suspended particles, causing colloidal particles to destabilize and coagulate rapidly, forming dense flocs. This achieves the primary removal of slurry and dyes and is the core flocculation link of the entire purification system.

[0080] (3) Activated carbon adsorption decolorization and deodorization mechanism: Special activated carbon has a well-developed microporous structure and a huge specific surface area. Through the dual action of physical adsorption and chemical adsorption, it can accurately capture dye molecules, organic odor-causing substances and residual colloidal impurities in sewage, achieve deep decolorization and deodorization, and at the same time adsorb the residual micro flocs in the water, further improving the water quality clarity. It is the core link to ensure that the effluent color meets the standards and has no odor.

[0081] (4) Mechanism of polyacrylamide bridging: As an organic polymer bridging agent, polyacrylamide (PAM) has long molecular chains that can form a strong bridging effect between dispersed flocs, connecting small flocs into large-volume, high-density flocs, greatly improving the settling speed and solid-liquid separation effect, facilitating subsequent pressure filtration, and further improving the suspended solids removal rate.

[0082] (5) Alum-enhanced sedimentation and acid-base neutralization mechanism: Alum (potassium aluminum sulfate dodecahydrate) hydrolyzes in water to generate aluminum hydroxide colloid, which can further adsorb the fine suspended particles and colloidal impurities remaining in the sewage, thereby enhancing sedimentation and making the settling and stratification more thorough and the supernatant clearer. At the same time, the alkalinity of quicklime and the acidity of polyaluminum chloride and alum form a precise neutralization effect, ultimately stabilizing the pH value of the clean water in the neutral range of 6-8, perfectly meeting the reuse requirements.

[0083] 3. Principle of Dual Antibacterial and Deodorizing Technology

[0084] Based on the synergistic deodorization principle of "physical dissolved oxygen inhibition + chemical sterilization and bacteriostasis", it eliminates the generation of foul odors from the root cause of anaerobic bacteria reproduction, rather than simply masking the odor:

[0085] (1) Physical Flowing Water Odor Suppression Mechanism: Anaerobic bacteria are obligate anaerobic microorganisms that cannot reproduce and metabolize normally in an aerobic environment. By driving the continuous circulation of sewage through a circulating pump, the contact area between sewage and air is greatly increased, raising the dissolved oxygen content in sewage to above 2 mg / L, creating an aerobic environment, fundamentally inhibiting the growth and reproduction of anaerobic bacteria, and reducing the production of malodorous gases such as hydrogen sulfide, which is the core principle of "flowing water does not stagnate".

[0086] (2) Mechanism of chemical Kathon antibacterial action: Kathon (isothiazolinone preservative) achieves broad-spectrum bactericidal and bacteriostatic effects on bacteria, fungi and algae by destroying the cell membrane, nucleic acid and enzyme system of microorganisms. Extremely low concentrations (1-8 parts per ten thousand) can effectively kill anaerobic bacteria in sewage and completely block the generation of malodorous gases. Moreover, the antibacterial effect can last for more than 3 days, which perfectly matches the production cycle of sewage replacement treatment every 3 days.

[0087] Prolonged use and storage of recycled wastewater can lead to the growth of anaerobic bacteria, releasing hydrogen sulfide and other substances that smell like rotten eggs. This can deteriorate the working environment and harm the health of workers.

[0088] This application utilizes the principle that flowing water does not stagnate. By using a circulating pump, the wastewater is used while it is in motion, allowing it to fully contact the air and reducing the generation of anaerobic bacteria, thereby reducing odor. A trace amount (1-8 parts per ten thousand) of Kathon (a preservative) is added to the replaced clean water to inhibit and kill bacteria, further reducing the generation of anaerobic bacteria and preventing odor. As the concentration of wastewater gradually increases, it can also prevent odor. Typically, the wastewater is replaced every 3 days, meaning that adding Kathon can basically prevent odor for 3 days.

[0089] 4. Principles of Zero-Discharge Water Treatment Technology

[0090] Based on the zero-emission principle of "component matching and source elimination," this method breaks through the traditional approach of "treatment to meet emission standards," completely eliminating purified water within the digital printing production process. Composition analysis and production verification show that the main pollutants in the purified water are residual dyes and paste components, similar to the paste components used in the digital printing sizing process. When used to prepare printing pastes, it will not affect the color development of reactive / disperse / acid dyes or the sizing quality of the fabric. During the drying process after fabric sizing, the water in the paste is completely converted into water vapor and released into the air through 120-150℃ heat drying, with no liquid wastewater discharged. This truly achieves zero wastewater discharge and zero pollution, forming a virtuous cycle of "wastewater-purification-reuse-evaporation."

[0091] Example 2: Wastewater Treatment Method for Digital Printing Conveyor Belts

[0092] like Figure 2 As shown, the wastewater treatment method for digital printing conveyor belts in this application is implemented based on the above system, and the detailed operation and process parameters for each stage are as follows:

[0093] Phase 1: Wastewater Recycling

[0094] 1. System initialization: Inject fresh tap water into the treated water tank, set the pressure pump output pressure to 0.4MPa, the circulation pump flow rate to 10m³ / h, open the automatic control valves of the system pipeline to form a complete water flow path, and test the normal operation of each sensor and automatic control device.

[0095] 2. Belt Cleaning Cycle: After the digital printing machine completes a single batch of fabric printing, it automatically starts the pressure pump. The clean water in the treated water tank is pressurized and then evenly sprayed onto the surface of the printing belt through the high-pressure nozzles of the spray pipe. The brush roller rotates synchronously with the belt at a speed of 60r / min to brush and dissolve the residual ink on the surface of the belt. The wastewater after rinsing flows into the wastewater tank through the water collection tray and guide pipe under the belt. After being filtered by the grid filter to remove fabric fiber impurities, it is pumped to the circulating water tank and then pumped back to the spray pipe for belt rinsing, forming a continuous cycle rinsing process.

[0096] 3. Circulation Concentration Control: The color and suspended solids concentration of the wastewater in the circulating water tank are monitored in real time by online monitoring equipment. When the color exceeds 200 times and the suspended solids concentration exceeds 500mg / L, the circulation flushing is automatically stopped and the wastewater is transported to the wastewater treatment filter press for purification. The purified water is then injected back into the treated water tank to replace the original high-concentration wastewater and start a new round of circulation flushing.

[0097] 4. Cycle Management: In line with the continuous production rhythm of digital printing, a complete treatment cycle of 3 days is set for wastewater. That is, after 3 days of recycling, regardless of whether the concentration meets the standard, a comprehensive purification treatment is carried out to avoid the growth of anaerobic bacteria due to long-term stagnation of wastewater and to ensure that the working environment is odorless.

[0098] Phase Two: Five-Step Wastewater Purification

[0099] High-concentration wastewater from the circulating water tank is pumped into the flocculation reaction chamber of the wastewater treatment filter press equipment. The variable frequency agitator is turned on, and the agitation speed is set to 80 r / min. The five-step purification process is strictly implemented.

[0100] Step 1: Pre-flocculation with quicklime: Add quicklime powder at a volume of 5-10 per ten thousand of the wastewater and stir continuously for 10 minutes to allow the quicklime to fully hydrolyze and generate calcium hydroxide colloids, which adsorb and encapsulate the fine suspended matter in the wastewater to form preliminary flocs. At this time, the pH value of the wastewater will rise to 9-10, providing a suitable alkaline environment for subsequent flocculation.

[0101] Step 2: Polyaluminum chloride primary flocculation: Add liquid polyaluminum chloride at a volume of 0.04-12 parts per ten thousand of the wastewater and stir continuously for 10 minutes. Visible flocculent flocculation forms in the wastewater, and the dye and slurry colloids rapidly destabilize and coagulate.

[0102] Step 3: Activated carbon adsorption and decolorization: Add 200-mesh special powdered activated carbon at 0.05-15 parts per ten thousand of the wastewater volume, and stir continuously for 15 minutes to fully mix the activated carbon with the wastewater, adsorbing the dyes, pigments, and odor-causing organic matter in the wastewater. The wastewater will begin to show obvious solid-liquid stratification, and the upper layer of water will gradually become clearer and the color will be greatly reduced.

[0103] Step 4: Polyacrylamide coagulation aid: Add 0.1% polyacrylamide liquid at a concentration of 4-10% of the wastewater volume, reduce the stirring speed to 30r / min and stir slowly for 5 minutes, then stop stirring. The fine flocs in the wastewater quickly coagulate into large flocs and settle rapidly to the bottom of the reaction chamber, resulting in a significant flocculation and stratification effect.

[0104] Step 5: Alum-assisted coagulation and sedimentation: Add alum powder at a volume of 1 / 10,000 to 8 parts per ten thousand of the wastewater, stir continuously for 10 minutes, and let it stand for 30 minutes to settle. The wastewater will be completely separated into layers, the supernatant will be clear and transparent, and the flocs at the bottom will be compacted. Online monitoring shows that the pH value of the supernatant is stable in the neutral range of 6-8, thus completing the wastewater purification.

[0105] The purified supernatant is pumped into the treatment water tank, and the sedimented sludge at the bottom is filtered by a chamber filter press into sludge cake with a moisture content of less than 60%, which is then handed over to a qualified solid waste disposal unit for compliant treatment.

[0106] Phase 3: Dual Deodorization of Wastewater

[0107] Throughout the entire process of wastewater recycling and purification reuse, physical and chemical dual deodorization are performed simultaneously to achieve full-cycle odor control:

[0108] 1. Physical flow-based odor suppression: During the wastewater recycling process, the circulation pump is run 24 hours a day, driving the wastewater in the circulation tank at a flow rate of 10m³ / h. 3 The continuous circulation of the wastewater at a flow rate of / h allows for full contact between the wastewater and the air, increasing the dissolved oxygen content to over 2mg / L, creating an aerobic environment, inhibiting the growth of anaerobic bacteria, and reducing the generation of malodorous gases at the source.

[0109] 2. Chemical antibacterial and deodorizing: Add Kathon preservative to the purified water in the treatment tank at a volume of 1-8 parts per ten thousand of the water volume through an automatic dosing device. After stirring evenly, use it for conveyor belt circulation rinsing. Kathon can effectively inhibit the growth of anaerobic bacteria and fungi in sewage. Even if the sewage concentration gradually increases, it can effectively prevent the generation of odor within a 3-day cycle and completely eliminate the release of hydrogen sulfide malodorous gas.

[0110] Phase Four: Zero Discharge Treatment of Purified Water

[0111] The purified water is divided into two streams for full reuse, achieving zero-discharge treatment of wastewater:

[0112] 1. Conveyor belt cleaning and reuse: 70% of the purified water is reused in the conveyor belt cleaning process as spray rinsing water, which enters the circulating rinsing process to realize the closed-loop reuse of water resources without the need to add fresh tap water.

[0113] 2. Zero-discharge reuse in the sizing process: 30% of the purified water is supplied to the digital printing sizing process, completely replacing tap water for preparing printing paste; according to the fabric sizing process requirements, the purified water is mixed with the printing paste and thickener in proportion, stirred evenly, and then evenly coated onto the fabric surface through the sizing machine; the fabric with sizing enters the drying chamber, and at a drying temperature of 120-150℃, the water in the sizing is completely evaporated into water vapor and discharged into the air, with no liquid wastewater discharged, achieving zero-discharge treatment of wastewater.

[0114] Examples of wastewater treatment applications with different reagent ratios are as follows:

[0115] This application sets up three application examples with different reagent dosage ratios for wastewater from digital printing conveyor belts with different pollution loads. All embodiments use the wastewater treatment system of this application.

[0116] Application Example 1: Low-Pollution Load Wastewater - Low-Dosage Chemical Treatment Solution

[0117] 1. Processing Object

[0118] The wastewater from the low-pollution-load digital printing conveyor belt comes from the conveyor belt cleaning process after printing on light-colored fabrics. The initial wastewater quality is as follows: pH 8.2, color 150 times, chemical oxygen demand (COD) 850 mg / L, ammonia nitrogen 28.5 mg / L, total phosphorus 0.03 mg / L, total nitrogen 72.4 mg / L, and suspended solids 86 mg / L.

[0119] 2. Processing procedure

[0120] Take 1000L of the above-mentioned wastewater and pump it into the flocculation reaction chamber of the wastewater treatment filter press equipment. Turn on the stirring device (80r / min) and execute the five-step purification process:

[0121] Step 1: Add 50g of quicklime (0.05%), stir for 10 minutes to complete the pre-flocculation;

[0122] Step 2: Add 40g of polyaluminum chloride (0.04%), stir for 10 minutes, and form obvious flocs;

[0123] Step 3: Add 50g of special activated carbon (0.05%), stir for 15 minutes, and adsorb and decolorize;

[0124] Step 4: Add 4L of 0.1% polyacrylamide liquid (4 parts per thousand), stir slowly for 5 minutes to aid coagulation and stratification;

[0125] Step 5: Add 10g of alum (1 / 10,000), stir for 10 minutes, and let it stand and settle for 30 minutes;

[0126] Simultaneous dual deodorization is performed: the circulating pump continuously circulates the sewage, and 10g of Kathon (1 / 10,000) is added to the purified water.

[0127] 3. Testing process and results

[0128] The treated water underwent comprehensive testing in accordance with national testing standards.

[0129] pH value: Tested according to HJ 1147-2020 "Determination of pH value of water by electrode method";

[0130] Chemical oxygen demand (COD): Detected according to HJ 828-2017 "Determination of Chemical Oxygen Demand in Water - Dichromate Method";

[0131] Ammonia nitrogen: Detected according to HJ 535-2009 "Determination of Ammonia Nitrogen in Water - Nessler's Reagent Spectrophotometric Method";

[0132] Total phosphorus: Detected according to GB / T 11893-1989 "Determination of Total Phosphorus in Water - Ammonium Molybdate Spectrophotometric Method";

[0133] Total nitrogen: Detected according to HJ 636-2012 "Determination of total nitrogen in water quality by alkaline potassium persulfate digestion ultraviolet spectrophotometry";

[0134] Suspended solids: Tested according to GB / T 11901-1989 "Determination of suspended solids in water by gravimetric method".

[0135] The test results are shown in Table 1 below:

[0136] Colorless and clear 7.2 620 21.6 0.005 45.8 4

[0137] Table 1

[0138] This embodiment targets wastewater with low pollution load and adopts a low-dose reagent scheme, which reduces reagent costs by 40% while ensuring purification effect. The treated water is colorless and clear with a neutral pH value, a suspended solids removal rate of 95.3%, and a decolorization rate of 100%, fully meeting the reuse requirements for conveyor belt cleaning and slurry preparation. After the addition of Kathon, no odor is generated within 3 days, and there is no foul odor pollution in the working environment.

[0139] Example 2: Wastewater with Medium Pollution Load - Standard Dosage Chemical Treatment Scheme

[0140] 1. Processing Object

[0141] The medium-pollution load digital printing conveyor belt wastewater comes from the conveyor belt cleaning process after conventional fabric printing. The initial wastewater quality is as follows: pH value 8.5, color 300 times, chemical oxygen demand (COD) 1560 mg / L, ammonia nitrogen 45.8 mg / L, total phosphorus 0.02 mg / L, total nitrogen 115 mg / L, and suspended solids 128 mg / L.

[0142] 2. Processing procedure

[0143] Take 1000L of the above-mentioned wastewater and pump it into the flocculation reaction chamber of the wastewater treatment filter press equipment. Turn on the stirring device (80r / min) and execute the five-step purification process:

[0144] Step 1: Add 80g of quicklime (0.08%), stir for 10 minutes to complete pre-flocculation;

[0145] Step 2: Add 80g of polyaluminum chloride (0.08%), stir for 10 minutes, and form obvious flocs;

[0146] Step 3: Add 100g of special activated carbon (10 / 10,000), stir for 15 minutes, and adsorb and decolorize;

[0147] Step 4: Add 7L of 0.1% polyacrylamide liquid (7 parts per thousand), stir slowly for 5 minutes to aid coagulation and stratification;

[0148] Step 5: Add 50g of alum (0.05%), stir for 10 minutes, and let it stand and settle for 30 minutes;

[0149] Simultaneous dual deodorization is performed: the circulating pump continuously circulates the sewage, and 50g of Kathon (0.05%) is added to the purified water.

[0150] 3. Testing process and results

[0151] The testing standards are completely consistent with those in Example 1, and the test results are shown in Table 2 below:

[0152] Colorless and slightly turbid 7.5 1.17×10³ 43.2 0.01 109 11

[0153] Table 2

[0154] This embodiment represents the optimal solution under standard production conditions. The five-step purification process works synergistically to achieve a neutral pH of 7.5 in the treated water, fully meeting the requirements for reuse in digital printing production. The suspended solids removal rate reaches 91.4%, the decolorization rate reaches 98%, and the purification effect is stable. The dual deodorization scheme can completely suppress odor generation within a 3-day production cycle, with no hydrogen sulfide gas release. After the purified water is used to prepare printing paste, the fabric printing color is uniform, without any color difference or color variation issues, fully meeting the requirements of digital printing production and achieving full reuse and zero discharge of wastewater.

[0155] Example 3: High-Pollution Load Wastewater - High-Dosage Chemical Treatment Scheme

[0156] 1. Processing Object

[0157] The wastewater from the high-pollution-load digital printing conveyor belt comes from the conveyor belt cleaning process after printing on dark and rich-colored fabrics. The initial wastewater quality is as follows: pH value 8.8, color 800 times, chemical oxygen demand (COD) 3200 mg / L, ammonia nitrogen 86.4 mg / L, total phosphorus 0.05 mg / L, total nitrogen 240 mg / L, and suspended solids 260 mg / L.

[0158] 2. Processing procedure

[0159] Take 1000L of the above-mentioned wastewater and pump it into the flocculation reaction chamber of the wastewater treatment filter press equipment. Turn on the stirring device (80r / min) and execute the five-step purification process:

[0160] Step 1: Add 100g of quicklime (10 / 10,000), stir for 10 minutes to complete the pre-flocculation;

[0161] Step 2: Add 120g of polyaluminum chloride (12 parts per ten thousand), stir for 10 minutes, and obvious flocs will form;

[0162] Step 3: Add 150g of special activated carbon (15 parts per ten thousand), stir for 20 minutes, and perform deep adsorption and decolorization;

[0163] Step 4: Add 10L of 1 / 1000 concentration polyacrylamide liquid, stir slowly for 5 minutes to aid coagulation and stratification;

[0164] Step 5: Add 80g of alum (0.08%), stir for 10 minutes, and let it stand for 40 minutes to settle;

[0165] Simultaneous dual deodorization is performed: the circulating pump continuously circulates the sewage, and 80g of Kathon (0.08%) is added to the purified water.

[0166] 3. Testing process and results

[0167] The testing standards are completely consistent with those in Example 1, and the test results are shown in Table 3 below:

[0168] Colorless and slightly turbid 7.8 1850 52.7 0.008 168 18

[0169] Table 3

[0170] This embodiment targets dark-colored printing wastewater with high pollution loads. A high-dose reagent solution was used, achieving excellent purification results with a decolorization rate of 96% and a suspended solids removal rate of 93.1%, completely solving the industry problem of difficult decolorization and reuse of high-color wastewater. The treated water's pH value remained stable in the neutral range of 7.8, fully meeting reuse requirements. Even with a rapid increase in wastewater concentration after high-dose Kathon addition, anaerobic bacteria growth was completely inhibited within 3 days, with no foul odor. The purified water was reused in the conveyor belt cleaning process, with residual ink rinsing effect indistinguishable from fresh tap water, achieving closed-loop reuse of highly polluted wastewater.

[0171] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A digital printing conveyor belt wastewater treatment system, comprising a circulating water tank, a conveyor belt digital printer cluster, a wastewater treatment filter press, and a treated clean water tank, wherein the conveyor belt digital printer cluster has a built-in printing conveyor belt, characterized in that: The circulating water tank has a built-in liquid level sensor and a pH online monitoring probe for temporarily storing the return wastewater after the conveyor belt is cleaned; The wastewater treatment filter press is an integrated chamber filter press, which has a flocculation reaction chamber, a frequency conversion stirring device, an activated carbon adsorption chamber, a filter press plate group and a supernatant collection chamber connected in sequence, for the flocculation purification and solid-liquid separation of wastewater. The water tank is equipped with an antibacterial dosing port, a residual chlorine monitoring probe, and a liquid level control device, and is used to store purified water. The circulating water tank, the belt digital printer cluster, the sewage treatment filter press, and the treated water tank are connected in sequence to the automatic control valves through corrosion-resistant industrial pipelines, forming a closed-loop water flow path of "cleaning-return-circulation-purification-reuse". The water outlet of the water treatment tank is divided into two reuse branches. The first branch is a belt cleaning reuse branch connected to the belt digital printer cluster, and the second branch is a sizing process reuse branch connected to the digital printing sizing system.

2. The digital printing conveyor belt wastewater treatment system according to claim 1, characterized in that, It also includes a booster power unit, which comprises a pressure pump, a water pump, and a circulation pump. All three pumps are corrosion-resistant chemical centrifugal pumps equipped with a frequency converter control cabinet. The pressure pump is located at the outlet of the treated water tank and provides 0.3-0.5 MPa of booster power for the belt cleaning process. The water pump is located between the belt digital printer cluster and the circulation tank to transport the cleaned wastewater to the circulation tank. The circulation pump is located between the inlet and outlet of the circulation tank to drive the wastewater circulation.

3. The digital printing conveyor belt wastewater treatment system according to claim 1, characterized in that, The digital printer cluster also has a built-in cleaning execution unit, which includes a spray pipe, a high-pressure atomizing nozzle, and a brush roller. The high-pressure atomizing nozzle is evenly distributed above the printing guide belt, and the spray angle is at a 30-60° angle with the surface of the printing guide belt. The brush roller is made of wear-resistant nylon material, which makes elastic contact with the surface of the printing guide belt, and the speed of the brush roller is linked and matched with the running speed of the printing guide belt.

4. The digital printing conveyor belt wastewater treatment system according to any one of claims 1 to 3, characterized in that, The digital printer cluster also has a built-in wastewater collection unit, which includes a wastewater tank, a water collection tray, and a guide pipe. The water collection tray covers the entire area below the printing guide belt and is used to collect wastewater after washing. The wastewater tank has a built-in stainless steel grid filter screen to filter fabric fibers and lint impurities in the wastewater. The guide pipe is used to guide the wastewater collected in the water collection tray to the wastewater tank.

5. The digital printing conveyor belt wastewater treatment system according to any one of claims 1 to 4, characterized in that, It also includes a circulating odor suppression unit, which includes a circulating pipeline and an automatic Kathon dosing device; the circulating pipeline connects the inlet and outlet of the circulating water tank to form a closed-loop sewage circulation path; the automatic Kathon dosing device is connected to the antibacterial dosing port of the treated water tank, and the automatic Kathon dosing device is signal-interlocked with the residual chlorine monitoring probe and the liquid level control device for quantitative dosing of Kathon agent.

6. A method for treating wastewater from digital printing conveyor belts, characterized in that, The implementation of the digital printing conveyor belt wastewater treatment system according to any one of claims 1 to 5 includes the following steps: Wastewater recycling: The clean water in the treated water tank is pressurized and then transported to the digital printer cluster to spray and wash the printing guide belt. The wastewater after cleaning is collected and filtered and then transported to the circulating water tank. The water quality parameters of the wastewater in the circulating water tank are monitored in real time. When the water quality reaches the set threshold or the circulation cycle is completed, the wastewater is transported to the wastewater treatment filter press equipment. Multi-stage wastewater purification: Wastewater output from the circulating water tank is sent into the flocculation reaction chamber of the wastewater treatment filter press equipment. With the cooperation of the variable frequency stirring device, the five-step purification process is executed in sequence to complete the flocculation, adsorption, sedimentation and solid-liquid separation of the wastewater, and obtain the purified supernatant and filter cake. The supernatant is transported to the treated clean water tank. Dual antibacterial and deodorizing: In the entire process of sewage circulation and purification reuse, physical deodorization is achieved by driving the continuous circulation of sewage to increase the dissolved oxygen content, while chemical antibacterial and deodorizing are achieved by quantitatively adding Kathon preservative to the purified water in the treated water tank. Zero-discharge reuse of purified water: The purified water in the treated water tank is fully reused in two ways. The first way is reused to the conveyor belt cleaning process to enter the next cycle. The second way is sent to the digital printing sizing process to replace tap water to prepare printing paste. The water in the paste is evaporated into water vapor in the fabric drying process, realizing zero discharge of liquid wastewater.

7. The wastewater treatment method for digital printing conveyor belts according to claim 6, characterized in that, In step S1, the water quality parameters are color and suspended solids concentration, with thresholds set at color exceeding 200 times and suspended solids concentration exceeding 500 mg / L; the circulation cycle is set to 3 days, during which the wastewater is driven at a speed of 8-12 m 3 The continuous circulation of the flow rate per hour keeps the dissolved oxygen content in the wastewater above 2 mg / L.

8. The wastewater treatment method for digital printing conveyor belts according to claim 6, characterized in that, In step S2, the specific operation of the five-step purification process is as follows: Step 1: Pre-flocculation with quicklime. Add quicklime powder at 5-10 parts per ten thousand of the wastewater volume and stir continuously at 80 r / min for 10 minutes to adjust the pH of the wastewater to 9-10. Step 2: Polyaluminum chloride as the main flocculator, add liquid polyaluminum chloride at a volume of 4-12 parts per ten thousand of the wastewater, and stir continuously for 10 minutes; Step 3: Activated carbon adsorption and decolorization. Add 200-mesh powdered activated carbon at 5-15 parts per ten thousand of the wastewater volume and stir continuously for 15-20 minutes. Step 4: Add 0.1% polyacrylamide liquid at a concentration of 4-10% of the wastewater volume, reduce the stirring speed to 30r / min and stir slowly for 5 minutes, then stop stirring. Step 5: Alum-assisted coagulation and sedimentation. Add alum powder at a volume of 1 / 10,000 to 8 parts per ten thousand of the wastewater, stir continuously for 10 minutes, and then let it stand for 30 to 40 minutes to settle. Finally, the pH value of the supernatant will stabilize at 6 to 8.

9. The wastewater treatment method for digital printing conveyor belts according to claim 6, characterized in that, In step S3, the dosage of Kathon preservative is 1-8 parts per ten thousand of the volume of purified water, and the antibacterial effect after addition is not less than 3 days, which matches the wastewater circulation treatment cycle.

10. The wastewater treatment method for digital printing conveyor belts according to claim 6, characterized in that, In step S4, the two-way reuse ratio of purified water is as follows: 70% of the purified water is reused in the first channel to the conveyor belt cleaning process, and 30% of the purified water is reused in the second channel to the digital printing sizing process; the drying temperature of the fabric drying process is 120-150℃.

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