A method for reducing pollution and saving water in a photovoltaic industrial park sewage treatment and recycling

Abstract

The present application relates to sewage treatment and water resource recycling technical field, especially to a kind of photovoltaic industrial park sewage treatment and recycling integrated pollution reduction water-saving method, including first pollution reduction water-saving strategy, pull rod slice production wastewater internal circulation, photovoltaic cell piece production wastewater internal circulation;Second pollution reduction water-saving strategy, after tail water treatment of park sewage treatment plant, as recycled water is provided to enterprise, for the production, life link of non pure water demand;After tail water treatment of sewage treatment plant, as recycled water is provided to enterprise, for pure water production;Third pollution reduction water-saving strategy, enterprise fluorine-containing wastewater, fluorine-free wastewater is treated by quality, and quality is transported to sewage treatment plant, so that sewage treatment plant reduces fluorine-containing wastewater treatment cost, while increasing fluorine-free recycled water volume, reduce the influence of photovoltaic industrial wastewater on water ecological environment.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment and water resource recycling technology, specifically to an integrated method for wastewater treatment and reuse in photovoltaic industrial parks to reduce pollution and save water. Background Technology

[0002] Guided by the "dual carbon" goals, the global energy structure is accelerating its transformation towards green and low-carbon development. As a crucial pillar of the new energy sector, the photovoltaic industry has experienced rapid growth in recent years. In China, the photovoltaic industry has become a key force driving energy transformation and promoting green economic growth. Jiangsu, Inner Mongolia, Sichuan, and other regions, leveraging their respective resource advantages, industrial foundations, and policy support, have established specialized photovoltaic industrial parks, becoming core areas for the development of China's photovoltaic industry.

[0003] Behind the booming development of the photovoltaic industry, the problem of industrial wastewater treatment in photovoltaic industrial parks is becoming increasingly prominent. During the photovoltaic production process, especially in key stages such as monocrystalline silicon ingot pulling and slicing and cell production, a large amount of industrial wastewater is generated. This wastewater has significant water quality characteristics, with fluoride being a characteristic pollutant at high concentrations. For example, in the wastewater discharged by some monocrystalline silicon production enterprises, the fluoride concentration can reach 100-500 mg / L, far exceeding the environmental carrying capacity. At the same time, the wastewater also contains high concentrations of sulfates, chlorides, and other salts. These salts not only increase the difficulty of wastewater treatment but also have a significant impact on the aquatic ecosystem. If high concentrations of fluoride and salts are discharged directly into water bodies without effective treatment, they will cause multifaceted damage to the aquatic ecosystem. For aquatic organisms, fluoride interferes with the normal physiological functions of fish, affecting their growth and reproduction. Related studies have shown that when the fluoride concentration in water reaches 5 mg / L, the growth rate of fish slows down significantly, their reproductive capacity is inhibited, the hatching rate of fish eggs decreases, and the deformity rate of juvenile fish increases. High concentrations of salt can alter the osmotic pressure of water, affecting the normal growth of aquatic plants, disrupting the ecological balance of water bodies, and consequently impacting the stability and health of the entire aquatic ecosystem.

[0004] Faced with a severe wastewater treatment situation, domestic photovoltaic industrial parks have established a traditional model for wastewater treatment: First, pre-treatment with defluorination is carried out within the photovoltaic companies. These companies add chemical agents, such as calcium salts, to cause fluoride ions to form insoluble fluoride precipitates, initially reducing the concentration of fluoride in the wastewater. Subsequently, the wastewater is transported to the park's wastewater treatment facilities, where it undergoes two stages of defluorination treatment. After this series of treatment processes, the wastewater generally meets the industry discharge standard of 10 mg / L. However, for some ecologically fragile areas with higher environmental management requirements, relying solely on the above-mentioned end-of-pipe treatment methods is insufficient to further reduce fluoride concentrations and meet more stringent environmental protection requirements.

[0005] Problems with this system:

[0006] (1) Both enterprises and wastewater treatment plants generally use similar two-stage advanced defluorination processes. Over-treatment by enterprises increases the difficulty of defluorination in wastewater treatment plants.

[0007] (2) Excessive defluorination by enterprises and sewage treatment plants leads to excessively high concentrations of chloride ions, sulfate ions and total salts in wastewater discharge from industrial parks, resulting in secondary pollution.

[0008] (3) Photovoltaic enterprises have high requirements for fresh water and consume large quantities of it. The recycling of wastewater in photovoltaic industrial parks is seriously insufficient, resulting in a waste of fresh water.

[0009] Comparison documents:

[0010] (1) CN106746113B A process and system for resource utilization and reuse of fluoride-containing wastewater in the photovoltaic industry

[0011] Description: This invention provides a process for the resource recovery and reuse of fluoride-containing wastewater in the photovoltaic industry. The process involves classifying and collecting concentrated acid wastewater, concentrated alkali wastewater, dilute acid wastewater, and dilute alkali wastewater. Sodium or potassium salts are added to the concentrated acid wastewater based on its fluorosilicate ion concentration to induce crystallization and obtain fluorosilicates. Calcium salts are added to the concentrated acid wastewater based on its fluoride ion concentration to induce crystallization and obtain calcium fluoride. The dilute alkali and acid wastewater are sent to a reaction tank for defluorination treatment, then to a sedimentation tank for sedimentation treatment, followed by chemical softening treatment. The wastewater then passes through a sand filter, an activated carbon filter, a resin softener, and a reverse osmosis unit to obtain permeable water. The system effluent from the crystallization reaction of the concentrated acid wastewater and the concentrated alkali wastewater are sent to a reaction tank for defluorination treatment, then to a sedimentation tank for sedimentation treatment, and finally to an evaporator to obtain condensate permeable water. Furthermore, a system for the resource recovery and reuse of fluoride-containing wastewater in the photovoltaic industry is also provided.

[0012] Differences: This technology only considers the end-of-pipe treatment of four streams of fluoride-containing wastewater from photovoltaic cell manufacturing enterprises: concentrated acid, concentrated alkali, dilute acid, and dilute alkali. It focuses on reusing dilute acid and alkali wastewater with low salt content; secondary resource recovery for concentrated acid wastewater with high fluoride ion concentration; and evaporation treatment for concentrated alkali wastewater with high organic matter concentration and other backwash water. This technology uses activated carbon, resin, and reverse osmosis for treatment, resulting in high costs. This technology does not treat each of the four streams of chlorine-containing wastewater individually at the end of the process. Instead, it treats all water used by photovoltaic enterprises separately as fluoride-containing or fluoride-free wastewater. Fluoride-free wastewater is recycled for other processes, while fluoride-containing wastewater is treated separately. It does not propose processes like reverse osmosis, which significantly increases treatment costs, unlike this technology. Furthermore, this technology also considers fluoride-containing wastewater treatment from rod pulling and slicing enterprises; it considers pollution reduction from a plant-wide and park-wide perspective; and it reduces the amount of fluoride-containing wastewater treated and discharged through water reuse and water conservation—all aspects not considered in this technology.

[0013] (2) CN116062941B A method for synergistic defluorination and dechlorination of high-fluoride and chlorine wastewater from the photovoltaic industry

[0014] Description: This paper provides a method for fluoride resource recovery and simultaneous deep defluorination and dechlorination of fluoride- and chlorine-containing wastewater from different sources during photovoltaic module production. Concentrated acid wastewater is pumped into a reaction tank, while NaOH and NaAlO2 are slowly added to react with fluoride ions in the concentrated acid wastewater. After the reaction, solid-liquid separation is performed. The precipitate is deeply dehydrated and dried to obtain cryolite. The supernatant is mixed with concentrated alkaline wastewater, dilute acid wastewater, and dilute alkaline wastewater, filtered through a filter membrane, and then enters a capacitor deionization device for defluorination and dechlorination. The electrode material of the capacitor deionization device is an iron-manganese-doped sludge carbon material electrode. The permeate is then introduced into a deep defluorination tank, where lime slurry is added to adjust the pH to 7-8, followed by the addition of a chlorine-free defluorination agent, and then PAM flocculation to accelerate sedimentation. The treated water is then discharged after meeting the standards. After fluoride recovery, iron-manganese-doped sludge-based electrode capacitor deionization and deep defluorination, the fluoride and chloride ion content of the effluent meets national emission standards. In this method, fluoride and chlorine-containing wastewater undergoes fluoride recovery, iron-manganese doped sludge-based electrode capacitor deionization and deep defluorination. The effluent fluoride content is 1-2 mg / L, and the chloride content is consistently below 200 mg / L, meeting national emission standards. Moreover, the operating cost is low, and cryolite products that meet the standards can be recovered.

[0015] Differences: This technology reduces the concentrations of fluoride and chloride ions in the effluent through deep defluorination and dechlorination, but it only considers the end-of-pipe treatment of four streams of fluoride-containing wastewater: concentrated acid, concentrated alkali, dilute acid, and dilute alkali. It does not consider pollution reduction from the perspective of the entire plant and industrial park, nor does it reduce the volume of fluoride-containing wastewater treated and discharged through water reuse and water conservation. Furthermore, this method does not consider the removal of fluoride ions at concentrations from 2 mg / L to below 1 mg / L, and it does not clearly explain the changes in sulfate concentration while reducing chloride. This technology fully considers the reuse and treatment of wastewater from the entire photovoltaic industry plant, reducing the volume of fluoride-containing wastewater, simultaneously reducing the cost and volume of fluoride-containing wastewater treatment, proposing a feasible path to control fluoride to below 1 mg / L, and simultaneously considering the reduction and control of chloride and sulfate through total salt content indicators.

[0016] (3) CN116239211B A photovoltaic wastewater treatment system and treatment method

[0017] Description: This invention relates to a photovoltaic wastewater advanced treatment system and method. The photovoltaic wastewater treatment system includes a coagulation sedimentation tank, a primary ozone advanced oxidation tank, a secondary ozone catalytic advanced oxidation tank, and a tertiary ozone catalytic advanced oxidation tank connected in sequence. It is suitable for COD concentrations of 70–100 mg / L. If the photovoltaic wastewater, after biological treatment, cannot meet the discharge requirement of a COD concentration below 25 mg / L, this system's further advanced treatment can reduce the final effluent COD of the photovoltaic wastewater to below 25 mg / L, or even below 20 mg / L.

[0018] Differences: This technology only considers COD (Chemical Oxygen Demand) and does not take into account fluoride, a characteristic pollutant of the photovoltaic industry; it only considers wastewater treatment from photovoltaic enterprises and does not consider the linkage between photovoltaic park enterprises and wastewater treatment facilities. This technology fully considers fluoride reduction.

[0019] (4) CN113159387B A water resource optimization allocation system and method for near-zero wastewater discharge in industrial parks

[0020] Description: This invention relates to a water resource optimization allocation system and method for near-zero wastewater discharge in industrial parks. The system includes a river ecosystem, industrial enterprises within the park, enterprise wastewater treatment plants, the park's wastewater treatment plant, a wastewater treatment plant effluent purification wetland, and a reclaimed water plant. The method involves defining the objective function and constraints based on the water usage and discharge characteristics of different enterprises within the park. With the goals of minimizing fresh water consumption, reducing economic costs, and maximizing environmental benefits, a mathematical model for optimal water resource allocation in the park is constructed. A genetic algorithm is used to solve the mathematical model to obtain and output the optimal water resource allocation scheme for the industrial park. This invention clarifies the optimal effluent destination and volume prediction for each level of treatment facilities, and the selection and treatment level of each stage of water treatment processes, providing a scientific basis for zero-discharge wastewater network management, wastewater treatment facility design, and wastewater treatment technology upgrading in industrial parks.

[0021] Differences: This technology is a universal water resource allocation method for the utilization of reclaimed water in industrial parks, and it adopts an allocation method based on mathematical model algorithms; This technology is a reclaimed water allocation method for photovoltaic parks, which focuses on water resource allocation to address the unique problems of fluoride, chloride, and sulfate in photovoltaic parks, and explores the organic relationship between rod pulling and slicing enterprises, solar cell manufacturing enterprises and park sewage treatment plants. The water resource allocation method adopted is based on the principle of water intake and water use balance.

[0022] (5) CN106630388B An integrated energy-saving method for wastewater treatment in industrial parks

[0023] Description: This project optimizes the overall wastewater treatment process in industrial parks, comprehensively considering the relationship between enterprise wastewater pretreatment and the park's end-of-pipe wastewater treatment processes. Specifically, it omits the aerobic biological pretreatment process for enterprise wastewater, reserving organic matter for treatment at the park's wastewater treatment plant. This addresses the issue of insufficient carbon source in the denitrification stage of the end-of-pipe treatment plant. Simultaneously, it incorporates energy extraction processes within the park's wastewater treatment system, including enhanced primary treatment, high-load biological treatment, and anaerobic sludge digestion to recover energy. This reduces energy consumption in wastewater treatment and achieves the goal of extracting energy from wastewater to support wastewater treatment. The effects are particularly significant for industrial park wastewater treatment plants with a treatment capacity exceeding 100,000 tons / day.

[0024] Differences: The first technology is a general energy-saving method for wastewater treatment in industrial parks, primarily targeting those with a daily treatment capacity exceeding 100,000 tons. Its main technical approaches involve improving reagent dosing, treatment processes, energy recovery systems, and waste resource utilization. It focuses on addressing the duplication of aerobic biological treatment processes at the end of wastewater treatment in enterprises and industrial parks, and does not propose specific water-saving and pollution-reduction strategies tailored to the characteristics of the photovoltaic industry and the layout of photovoltaic industrial parks. The second technology is an industry-specific wastewater treatment strategy for the photovoltaic industry and photovoltaic industrial parks. It does not consider the scale of wastewater treatment plants or energy conservation issues, but rather focuses on water resource allocation and three-stage pollution reduction based on the specific pollution indicators of photovoltaic parks, such as fluoride, chloride, and sulfate.

[0025] (6) CN111470740A Intelligent Management Platform for Wastewater in Industrial Parks and its Control Method

[0026] Description: An intelligent wastewater management platform for industrial parks includes a water quality regulation system, a water quality monitoring system, and an emergency response system. The water quality regulation system includes a separate collection unit and a homogenization unit, which separately collect wastewater from heavily polluting enterprises, lightly polluting enterprises, and residential areas. The wastewater collected through homogenization is then sent to the biological treatment system of the wastewater treatment plant. The water quality monitoring system includes a monitoring unit, a data processing unit, and a control unit, which monitors the wastewater quality at each stage of the platform, traces enterprises exceeding emission standards, predicts the characteristics of enterprise wastewater discharge, and controls the start / stop, flow rate, and retention time of drainage at each stage. The emergency response system is used to treat accidental wastewater and send it to the biological treatment system of the wastewater treatment plant. This platform enables separate collection and regulation of wastewater, as well as emergency response to accidental wastewater, achieving real-time analysis, monitoring, and allocation of wastewater quality. This makes the wastewater source at the front end of the wastewater treatment plant more controllable and safer.

[0027] Differences: This technology is designed for the development and control of intelligent wastewater management platforms in general industrial parks. Its focus is on addressing the current situation where industrial wastewater management suffers from low source control, poor influent distribution capacity at wastewater treatment plants, and limited intelligent management capabilities. It optimizes the wastewater-industry wastewater treatment plant process through computational analysis to achieve wastewater discharge and distribution, and to trace enterprises exceeding discharge standards. This technology, on the other hand, is a wastewater treatment strategy specifically for the photovoltaic industry and photovoltaic industrial parks. It focuses on the emission and treatment of characteristic pollutants such as fluorides in photovoltaic wastewater. Furthermore, this technology employs a three-tiered pollution reduction and water conservation strategy, encompassing in-plant, inter-plant, and makeup water stages, fundamentally differing from this technology in its focus and technical approach. Summary of the Invention

[0028] The purpose of this invention is to provide an overall pollution reduction and water saving method for wastewater treatment and reuse in photovoltaic industrial parks. It designs a three-level pollution reduction and water saving strategy and method of "in-plant circulation", "plant-to-plant reuse" and "ecological water replenishment", so as to realize the use of wastewater from photovoltaic industrial parks for ecological water replenishment, reduce the amount of fluoride emissions in the park, and reduce the total salt content in wastewater.

[0029] To achieve the above objectives, the present invention provides the following technical solution: a comprehensive method for wastewater treatment and reuse in photovoltaic industrial parks, comprising the following steps:

[0030] S1: Primary pollution reduction and water conservation strategy

[0031] S1.1: Internal circulation of wastewater from bar slicing production;

[0032] S1.2: Internal recycling of wastewater from photovoltaic cell production;

[0033] S2: Secondary pollution reduction and water conservation strategy

[0034] S2.1: The wastewater from the photovoltaic park's wastewater treatment plant is treated to meet the Class III standard requirements of surface water in GB 3838-2002 Surface Water Environmental Quality Standard, and then provided to enterprises as reclaimed water for production and domestic use that does not require pure water.

[0035] S2.2: The effluent from the wastewater treatment plant in the photovoltaic industrial park is treated to meet the requirements of Class III standard GB 3838-2002 and then provided to enterprises as reclaimed water for pure water production.

[0036] S3: Three-tiered pollution reduction and water conservation strategy

[0037] S3.1: Enterprises treat fluoride-containing wastewater and non-fluoride-containing wastewater separately and transport them to the sewage treatment plant separately. This allows the sewage treatment plant to reduce the treatment cost of fluoride-containing wastewater while increasing the volume of non-fluoride-containing reclaimed water, making it more suitable for ecological water replenishment.

[0038] S3.2: The wastewater treatment plant in the photovoltaic park has separate discharge outlets for fluoride-containing wastewater and non-fluoride-containing wastewater into the river. The fluoride-containing wastewater is discharged after treatment, while the non-fluoride-containing wastewater is used for ecological water replenishment.

[0039] S3.3: Fluoride-free wastewater used for ecological water replenishment, whose key physicochemical indicators can meet the following requirements: fluoride (as F) ≤ 1 mg / L, sulfate (SO4) ≤ 1 mg / L. 2- )≤500mg / L, chloride (Cl)≤250mg / L.

[0040] Preferably, in the internal circulation of wastewater from the bar-pulling and slicing production, the amount of tap water taken from the enterprise is 100%, the wastewater from the fluoride-containing section accounts for 14.3%, and the wastewater from the non-fluoride-containing section is treated and reused, reducing the amount of fresh water taken by 26.7%.

[0041] Preferably, the yield of pure water prepared by the rod slicing enterprise through the pure water station is 51.1%, and the yield of pure water prepared by the photovoltaic enterprise through the pure water station is 61%.

[0042] Preferably, in the internal recycling of photovoltaic cell production wastewater, the amount of tap water taken from the enterprise is 100%, the wastewater from the fluoride-containing process accounts for 59.8%, and the wastewater from the non-fluoride-containing process is treated and reused, reducing the amount of fresh water taken by 15.2%.

[0043] Preferably, in the secondary pollution reduction and water conservation strategy, a water resource optimization allocation model based on water balance for "factory-to-factory reuse" in the park is constructed, with the goal of reducing the consumption of fresh water and minimizing the amount of fluoride-containing wastewater treated by the park's sewage treatment plant.

[0044] Preferably, in the "factory-to-factory reuse" water resource optimization allocation model, the constraints include: when the price of fresh water C1 ≥ the cost of treating fluoride-free wastewater C2 + the cost loss of fluoride-free ultrafiltration reverse osmosis C3 - the subsidy price C4, the enterprise uses fluoride-free wastewater reclaimed water for pure water production.

[0045] When C1 ≥ the cost of treating fluoride-containing wastewater C2 + C3 - C4, the company uses fluoride-containing wastewater reclaimed water for pure water production.

[0046] Preferably, in the three-level pollution reduction and water conservation strategy, the fluoride-free wastewater used for ecological water replenishment is treated separately to reduce its salt content, thereby avoiding any impact on juvenile fish in the water.

[0047] Preferably, in the ecological water replenishment process, the fluoride-free wastewater used for ecological water replenishment needs to be monitored regularly for fluoride, sulfate, and chloride concentrations, with a monitoring frequency of no less than once a week, to ensure that fluoride (as F) ≤ 1 mg / L and sulfate (SO4) ≤ 1 mg / L. 2- )≤500mg / L, chloride (Cl)≤250mg / L.

[0048] Compared with the prior art, the beneficial effects of the present invention are:

[0049] 1. This photovoltaic industrial park's comprehensive pollution reduction and water conservation method for wastewater treatment and reuse separates fluoride-containing and non-fluoride-containing wastewater through a primary pollution reduction and water conservation strategy of in-plant circulation and a secondary pollution reduction and water conservation strategy of plant-to-plant reuse. The fluoride-containing wastewater is then transported via a single pipeline to the industrial park's wastewater treatment plant for single-line treatment. Addressing the common problem of photovoltaic companies over-defluorinating fluoride-containing wastewater before it leaves the plant, which makes defluorination at the wastewater treatment plant difficult, this method reduces the two-stage defluorination process to a single stage at the wastewater treatment plant, thus lowering the difficulty and cost of defluorination.

[0050] 2. The overall pollution reduction and water conservation method for wastewater treatment and reuse in this photovoltaic industrial park, while avoiding repeated defluorination, reduces the repeated addition of defluorinating agents and the input of sulfate and chloride ions in the defluorinating agents, indirectly reducing the total salt content in the effluent discharged from the photovoltaic industrial park's wastewater treatment plant. The pollution reduction and water conservation processes in the rod pulling and slicing enterprises and photovoltaic cell enterprises were modified respectively. All water used by the photovoltaic enterprises is treated separately as fluoride-containing and fluoride-free wastewater. Fluoride-free wastewater is recycled for reuse in other processes, while fluoride-containing wastewater is treated separately. This reduces fluoride emission concentration and lowers treatment costs without relying on high-cost wastewater treatment technologies such as ultrafiltration and reverse osmosis.

[0051] 3. The overall pollution reduction and water conservation method for wastewater treatment and reuse in this photovoltaic industrial park, through the primary water conservation strategy, can reduce the fresh water consumption of rod pulling and slicing enterprises by 26.7% and that of photovoltaic cell enterprises by 15.2%. Through the secondary water conservation strategy, the effluent from the wastewater treatment plant in the photovoltaic industrial park can be treated to meet the Class III standard requirements of surface water in GB 3838-2002 Surface Water Environmental Quality Standard, and then provided to enterprises as reclaimed water for production and domestic processes that do not require pure water. With subsidies, it can be used for pure water production, thereby improving the degree of wastewater recycling in the photovoltaic industrial park and reducing the overall fresh water consumption of the photovoltaic industrial park.

[0052] 4. The overall pollution reduction and water saving method for wastewater treatment and reuse in the photovoltaic industrial park reduces the overall cost and volume of fluoride-containing wastewater treatment in the photovoltaic industrial park. It proposes a feasible path to control fluoride to below 1 mg / L and simultaneously considers the reduction and control of chloride and sulfate through the total salt content index. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the 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.

[0054] Figure 1 This is a schematic diagram of the raw water balance of wastewater from photovoltaic rod pulling and slicing production according to the present invention;

[0055] Figure 2 This is a schematic diagram of the water balance after the modification of the photovoltaic rod pulling and slicing production wastewater according to the present invention;

[0056] Figure 3 This is a schematic diagram of the raw water balance of wastewater from photovoltaic cell production according to the present invention;

[0057] Figure 4This is a schematic diagram of the water balance after the modification of the photovoltaic cell production wastewater according to the present invention.

[0058] Figure 5 This is a schematic diagram of the overall wastewater treatment strategy after the transformation of the photovoltaic industrial park according to the present invention. Detailed Implementation

[0059] 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.

[0060] Please see Figures 1-5 This invention provides a technical solution: an integrated method for wastewater treatment and reuse in photovoltaic industrial parks to reduce pollution and save water.

[0061] Includes the following steps:

[0062] S1: Primary pollution reduction and water conservation strategy

[0063] S1.1: Internal circulation of wastewater from bar slicing production;

[0064] Internal recycling of wastewater from rod drawing and chipping production (see raw water balance of rod drawing and chipping enterprises) Figure 1 Ingot pulling and slicing refers to the production process of pulling polycrystalline silicon raw materials into polycrystalline silicon rods after cleaning, and then slicing them into solar cell raw materials.

[0065] Assuming the enterprise's tap water intake is 100%, the internal recycling of wastewater from rod slicing production includes the following steps:

[0066] (1) The silicon wafer slicing company uses tap water to produce pure water through a pure water station (pure water production yield is 51.1%). 17.7% of the total water intake goes into the fluoride-containing process, including the acid washing and rinsing sections of the silicon material cleaning unit, as well as water-related sections such as ultrasonic cleaning and rinsing. This part discharges fluoride-containing wastewater, accounting for 14.3% after deducting evaporation losses.

[0067] (2) The bar-pulling and slicing enterprise uses tap water to produce pure water through a pure water station (pure water production yield is 51.1%). 33.4% of the total water intake goes into the fluoride-free processing section, including all water-related processes in the machining unit such as squaring, rounding, chamfering, dimensional correction, and polishing; and all water-related processes in the slicing unit such as bar bonding, slicing, pre-cleaning and degumming, cleaning, and drying. This part discharges fluoride-free wastewater, which, after accounting for evaporation losses, accounts for 26.7% of the total discharge.

[0068] (3) The fluoride-free wastewater from the rod cutting and slicing enterprise is pretreated by the on-site wastewater treatment facility and then reused for other production processes and landscaping water needs (36.3% water requirement, approximately 70% loss rate, and all fluoride-free wastewater can be accepted). Through this treatment, the amount of fresh water used is reduced by 26.7%, effectively reducing the enterprise's dependence on fresh water resources and improving water resource utilization. At the same time, this on-site recycling method avoids over-treatment of wastewater by the enterprise, simplifies processes that may otherwise require multiple treatments, and reduces treatment difficulty and costs.

[0069] (4) Fluoride-containing wastewater (14.3%) from the rod-drawing and slicing enterprise is treated in a fluoride-containing wastewater treatment pond, with the fluoride concentration controlled at ≤10mg / L. A single pipe connects to the fluoride-containing wastewater treatment section of the industrial park's wastewater treatment plant. Compared to the original total discharge of 63.3%, this represents a 41% reduction in wastewater discharge. This treatment method allows for specialized treatment of the fluoride-containing wastewater, improving treatment efficiency and reducing the burden on the subsequent centralized treatment at the industrial park's wastewater treatment plant. (See the water balance after the rod-drawing and slicing enterprise's renovation for details.) Figure 2 )

[0070] S1.2: Internal recycling of wastewater from photovoltaic cell production;

[0071] Internal recycling of wastewater from photovoltaic cell production (see water balance of a photovoltaic cell company) Figure 3 Photovoltaic cell production refers to the production process of photovoltaic cells with Topcon solar cell technology as the mainstream. The production process includes texturing, pre-boron expansion, SE, thermal oxidation, (BSG removal + alkaline polishing) - Polying, annealing, (PSG removal + RCA) - ALD, front coating, back coating, screen printing, sintering, light injection, testing and sorting, and packaging.

[0072] Assuming the enterprise's tap water intake is 100%, the internal recycling of photovoltaic cell production wastewater includes the following steps:

[0073] (1) Photovoltaic cell manufacturers use tap water to produce pure water through a pure water station (pure water production yield is 61%). 57.5% of the total water intake enters the fluoride-containing process, including texturing, BSG removal + alkali polishing, and PSG removal + RCA removal. This part discharges four types of fluoride-containing wastewater: concentrated acid water, concentrated alkali water, dilute acid water, and dilute alkali water. After accounting for evaporation losses and considering the substitution of chemicals, the final fluoride-containing wastewater is 59.8%.

[0074] (2) Photovoltaic cell manufacturers take tap water and process it into pure water at a pure water station (pure water preparation yield is 61%). 3.5% of the total water intake goes into the fluoride-free process section, including all water-related processes other than (1). This part discharges fluoride-free wastewater, accounting for 3.5%.

[0075] (3) The photovoltaic cell factory's pure water station generates 20% concentrated water, which, after mixing with fluoride-free wastewater (3.5%) and a small amount of domestic water, forms 28.7% fluoride-free wastewater. This wastewater is purified through the factory's wastewater treatment facilities and then reused in other production processes of the photovoltaic cell factory and for greening water needs (15.2% water requirement, approximately 11.7% loss rate). This measure reduces fresh water consumption by 15.2%, significantly improving the efficiency of water resource recycling. Moreover, this process achieves wastewater reuse without relying on high-cost wastewater treatment technologies such as ultrafiltration and reverse osmosis, effectively reducing treatment costs while lowering fluoride emission concentrations.

[0076] (4) Fluoride-containing wastewater (59.8%) from photovoltaic cell manufacturers is treated in a fluoride-containing wastewater treatment pond, with the fluoride concentration controlled to ≤10mg / L. A single pipe connects to the fluoride-containing wastewater treatment section of the industrial park's wastewater treatment plant. The total effluent discharge is reduced by 75% compared to the original 88.5%. This differentiated treatment method allows for targeted treatment of fluoride-containing and non-fluoride-containing wastewater, laying a solid foundation for the subsequent overall wastewater treatment in the industrial park. (See the water balance after the photovoltaic cell manufacturer's upgrade for details.) Figure 4 )

[0077] S2: Secondary pollution reduction and water conservation strategy

[0078] S2.1: The wastewater from the industrial park's wastewater treatment plant is treated to meet the Class III standard requirements of surface water in GB 3838-2002 Surface Water Environmental Quality Standard, and then provided to enterprises as reclaimed water for production and domestic use that does not require pure water.

[0079] Based on the water usage and drainage characteristics of various types of production enterprises in the photovoltaic industrial park, the water intake and water balance situation in the park is clarified, and a water resource optimization allocation model for "factory-to-factory reuse" is constructed. This model is a mathematical model based on water balance, aiming to minimize fresh water consumption and the amount of fluoride-containing wastewater treated by the industrial park's wastewater treatment plant.

[0080] Assuming there are m rod-drawing and slicing companies and n solar cell manufacturing companies in the industrial park, the mathematical model can be expressed as follows:

[0081]

[0082] In the formula, Q 工业园区用 Q represents the fresh water consumption for the entire industrial park. i用 Let be the fresh water consumption of the i-th enterprise. The constraint is to minimize the fresh water consumption of the industrial park.

[0083]

[0084] In the formula, Q 园区进水Q represents the influent volume of the industrial park's wastewater treatment plant. 企业排 Q represents the total wastewater discharge from all industrial enterprises in the industrial park. i排 Q represents the water displacement of the i-th bar slicing company. i排 This represents the drainage volume of the p-th photovoltaic cell manufacturer.

[0085] Q i排 =Q i1 +Q i2 (Equation 3)

[0086] In the formula, Q i1 Let Q be the volume of fluoride-free wastewater discharged by the i-th bar-drawing and slicing enterprise to the industrial park's wastewater treatment plant through the main discharge outlet. i2 The amount of fluoride-containing wastewater discharged by the i-th bar-cutting enterprise through a single pipe to the industrial park's wastewater treatment plant.

[0087] Q p排 =Q p1 +Q p2 (Equation 4)

[0088] In the formula, Q p1 Q represents the volume of fluoride-free wastewater discharged by the p-th photovoltaic cell manufacturer to the industrial park's wastewater treatment plant via the main discharge outlet. p2 This represents the volume of fluoride-containing wastewater discharged by the pth photovoltaic cell manufacturer through a single pipe to the industrial park's wastewater treatment plant.

[0089] Fluoride-free wastewater discharged through the main discharge outlet to the industrial park's wastewater treatment plant, after treatment to meet the Class III standard requirements of GB 3838-2002 Surface Water Environmental Quality Standard, can be provided to enterprises as reclaimed water for production and domestic processes requiring non-pure water, and can also be used for park landscaping. The maximum reclaimed water production capacity is:

[0090]

[0091] In the formula, Q 再生 This represents the total amount of reclaimed water produced in the entire industrial park. Q i1 Let Q be the volume of fluoride-free wastewater discharged by the i-th bar-drawing and slicing enterprise to the industrial park's wastewater treatment plant through the main discharge outlet. p1 This refers to the volume of fluoride-free wastewater discharged by the pth photovoltaic cell manufacturer through the main discharge outlet to the industrial park's wastewater treatment plant.

[0092] By treating wastewater effluent from wastewater treatment plants and reusing it as reclaimed water for non-pure water needs of enterprises, the level of wastewater recycling in photovoltaic industrial parks has been greatly improved. For example, in rod pulling and slicing enterprises, 9.6% of their non-pure water needs in production and daily life can be met by using reclaimed water from the park instead of fresh water. This has significantly reduced the overall fresh water consumption of the photovoltaic industrial park and effectively saved water resources.

[0093] S2.2: Wastewater treatment plant effluent, after being treated to meet the requirements of GB 3838-2002 Class III standard, is provided to enterprises as reclaimed water for pure water production;

[0094] After implementing the primary pollution reduction and water conservation strategy, the ingot pulling and slicing enterprises can still use reclaimed water from the industrial park to replace fresh water in 9.6% of their non-pure water needs in production and daily life processes. Photovoltaic cell manufacturers no longer have any need for reclaimed water in their production and daily life processes. The industrial park's reclaimed water production volume Q 再生 In the absence of other businesses in the industrial park, it may not be able to fully absorb the wastewater. To further promote water conservation in the photovoltaic industrial park, the effluent from the wastewater treatment plant will be treated to meet the requirements of GB 3838-2002 Class III standards and then provided to enterprises as reclaimed water for pure water production.

[0095] According to water balance, 60.1% of fresh water used by rod slicing companies is used for pure water production, while 81.4% of fresh water used by photovoltaic cell companies is used for pure water production. The price of fresh industrial water is C1 (yuan / ton).

[0096] The photovoltaic industrial park treats the wastewater from its sewage treatment plant to meet the Class III standard requirements of GB 3838-2002, with a treatment cost per ton of fluoride-containing wastewater (C). 2氟 (RMB / ton), Fluoride-free wastewater C 2无氟 (RMB / ton), this cost is prepaid to the enterprise.

[0097] Photovoltaic companies using reclaimed water that meets the requirements of GB 3838-2002 Class III standard to produce pure water will increase the cost of ultrafiltration and reverse osmosis, which is converted to C3 (yuan / ton).

[0098] To reduce wastewater discharge from photovoltaic enterprises, the industrial park can subsidize the use of recycled water to produce pure water, with a subsidy price of C4 (yuan / ton), where C4 ≥ 0 (Equation 6).

[0099] When C1≥C 2无氟 When C1 ≥ C2(fluoride) + C3 - C4 (Equation 7), enterprises will be motivated to use reclaimed water that has been treated from fluoride-free wastewater treatment plants to meet the requirements of GB 3838-2002 Class III standards for pure water production. When C1 ≥ C2(fluoride) + C3 - C4 (Equation 8), enterprises will be motivated to use reclaimed water that has been treated from fluoride-containing wastewater treatment plants to meet the requirements of GB 3838-2002 Class III standards for pure water production.

[0100] By setting these economic constraints, when the price of fresh water exceeds the cost of treating fluoride-free wastewater plus the cost of fluoride-free ultrafiltration and reverse osmosis, minus subsidies, companies will be more inclined to use fluoride-free wastewater reclaimed for pure water production. Similarly, when the corresponding price conditions for fluoride-containing wastewater are met, companies will use fluoride-containing wastewater reclaimed. This mechanism not only reduces the overall cost and volume of fluoride-containing wastewater treatment in the photovoltaic industrial park but also saves companies water costs, achieving a win-win situation for both economic and environmental benefits.

[0101] S3: Three-tiered pollution reduction and water conservation strategy

[0102] S3.1: Enterprises treat fluoride-containing wastewater and non-fluoride-containing wastewater separately and transport them to the sewage treatment plant separately. This allows the sewage treatment plant to reduce the treatment cost of fluoride-containing wastewater while increasing the volume of non-fluoride-containing reclaimed water, making it more suitable for ecological water replenishment.

[0103] The company separately treats fluoride-containing and fluoride-free wastewater before sending them to wastewater treatment plants. This allows wastewater treatment plants to employ more targeted treatment processes for different types of wastewater, thereby reducing the treatment cost of fluoride-containing wastewater. Simultaneously, the better treatment and utilization of fluoride-free wastewater increases the volume of fluoride-free reclaimed water, which is more suitable for ecological water replenishment. This process avoids the negative impact on juvenile fish caused by excessive addition of sulfate or chloride ions during wastewater treatment, which could lead to high total salinity levels. For example, acute toxicity tests on rare gudgeon larvae showed that larvae exposed to chloride ions exceeding 250 mg / L had significantly lower average swimming speeds than the clean water control group, potentially inhibiting their movement. Separate treatment effectively controls total salinity, protecting the aquatic ecosystem.

[0104] S3.2: The enterprise shall set up separate sewage outlets for fluoride-containing wastewater and non-fluoride-containing wastewater into the river. Fluoride-containing wastewater shall be discharged after treatment, while non-fluoride-containing wastewater shall be used for ecological water replenishment.

[0105] To better achieve the classification, treatment, and utilization of wastewater, the company separates fluoride-containing and non-fluoride-containing wastewater into separate river discharge outlets. The fluoride-containing wastewater undergoes rigorous treatment to meet discharge standards before being released, ensuring it does not pollute the water body. The non-fluoride-containing wastewater, after treatment, is used for ecological water replenishment, providing water resources to support the surrounding ecosystem and improving its quality.

[0106] S3.3: Fluoride-free wastewater used for ecological water replenishment, whose key physicochemical indicators can meet the following requirements: fluoride (as F) ≤ 1 mg / L, sulfate (SO4) ≤ 1 mg / L. 2- )≤500mg / L, chloride (Cl)≤250mg / L.

[0107] While reducing fluoride emissions, it is important to avoid excessive addition of sulfate or chloride ions during wastewater treatment, which could lead to high total salt levels and negatively impact juvenile fish in the water. (According to acute toxicity tests on rare gudgeon larvae, juvenile rare gudgeon exposed to chloride ions exceeding 250 mg / L had significantly lower average swimming speeds than the clean water control group, regardless of whether they were exposed to light or darkness, which may have a certain inhibitory effect on the movement behavior of rare gudgeon larvae.)

[0108] In the ecological water replenishment process, the fluoride-free wastewater used for ecological water replenishment needs to be monitored regularly for fluoride, sulfate, and chloride concentrations, with a monitoring frequency of no less than once a week, to ensure that fluoride (as F) ≤ 1 mg / L and sulfate (SO4) ≤ 1 mg / L. 2- ≤500mg / L, chloride (Cl) - The concentration of fluoride was ≤250 mg / L. Through this stringent control and regular monitoring, a feasible pathway to reduce fluoride levels to below 1 mg / L was proposed, further reducing fluoride emissions compared to traditional processes. Simultaneously, by controlling sulfate and chloride, the reduction and management of total salinity were considered, effectively mitigating secondary pollution and protecting the health and stability of the aquatic ecosystem.

[0109] The secondary and tertiary pollution reduction strategies are discussed in the following sections. Figure 5 .

[0110] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0111] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for overall pollution reduction and water saving in a photovoltaic industrial park wastewater treatment and recycling, characterized in that, The method comprises the following steps: S1: primary pollution reduction and water saving strategy S1.1: internal recycling of pull rod slice production wastewater; The pull rod slice enterprise takes tap water to prepare pure water through a pure water station, 17.7% of the total water intake enters a fluorine-containing section, 33.4% of the total water intake enters a non-fluorine-containing section, the non-fluorine-containing wastewater of the pull rod slice enterprise is pretreated by an internal sewage treatment facility and then is used for other production links and greening water demand of the pull rod slice enterprise, and the fluorine-containing wastewater of the pull rod slice enterprise is connected to an industrial park sewage treatment plant fluorine-containing wastewater treatment section after being treated by a fluorine-containing wastewater treatment pool. S1.2: internal recycling of photovoltaic cell production wastewater; The photovoltaic cell enterprise takes tap water to prepare pure water through a pure water station, 57.5% of the total water intake enters a fluorine-containing section, 3.5% of the total water intake enters a non-fluorine-containing section, 20% of the pure water generated by the pure water station of the photovoltaic cell enterprise is mixed with non-fluorine-containing wastewater and part of domestic water to form non-fluorine-containing wastewater, and the non-fluorine-containing wastewater is purified by an internal sewage treatment facility and then is used for other production links and greening water demand of the photovoltaic cell enterprise and is connected to an industrial park sewage treatment plant fluorine-containing wastewater treatment section. S2: secondary pollution reduction and water saving strategy S2.1: tail water of the park sewage treatment plant is used for production and living links with non-pure water demand; Assuming that there are m pull rod slice enterprises and n cell production enterprises in the park, the mathematical model is expressed as: ; In the formula, Q 工业园区用 is the total fresh water consumption of the industrial park, Q i用 is the fresh water consumption of the i-th enterprise, and the constraint condition is to minimize the fresh water consumption of the industrial park; ; In the formula, Q 园区进水 is the influent quantity of the industrial park sewage treatment plant, Q 企业排 is the drainage quantity of all industrial enterprises in the industrial park, Q i排 is the drainage quantity of the i-th solar wafer slicing enterprise, Q i排 is the drainage quantity of the p-th photovoltaic cell enterprise; ; wherein Q i1 is the amount of non-fluorine-containing wastewater discharged by the i-th slice enterprise through the total discharge outlet to the industrial park sewage treatment plant, Q i2 is the amount of fluorine-containing wastewater discharged by the i-th slice enterprise through a single pipe to the industrial park sewage treatment plant; ; In the formula, Q p1 Qp is the amount of non-fluorine-containing wastewater discharged by the pth photovoltaic cell enterprise to the industrial park sewage treatment plant through the total drain; Q p2 Qp is the amount of fluorine-containing wastewater discharged by the pth photovoltaic cell enterprise to the industrial park sewage treatment plant through the single pipe. The non-fluorine-containing wastewater transported to the industrial park sewage treatment plant through a total discharge port is treated to meet the surface water III standard requirements in the GB 3838-2002 surface water environmental quality standard and then is provided to the enterprises as reclaimed water for production and living links with non-pure water demand or is used for park greening, and the maximum production amount of the reclaimed water is: ; In the formula, Q 再生 is the total production of reclaimed water of the industrial park, Q i1 is the waste water discharge amount of the i-th wafer slicing enterprise not containing fluorine transported to the industrial park sewage treatment plant through the total discharge port, Q p1 is the waste water discharge amount of the p-th photovoltaic cell enterprise not containing fluorine transported to the industrial park sewage treatment plant through the total discharge port; S2.2: tail water of the sewage treatment plant is used for pure water production The price of fresh industrial water is C1 (yuan / ton). The photovoltaic industrial park will treat the wastewater from the sewage treatment plant to meet the requirements of GB 3838-2002 Class III standard. The cost per ton of water treated is C for fluoride-containing wastewater. 2氟 (RMB / ton), fluoride-free wastewater C 2无氟 (RMB / ton) Photovoltaic enterprises using reclaimed water that meets the requirements of GB 3838-2002 Class III standard to prepare pure water will increase the cost loss of ultrafiltration and reverse osmosis, which is converted to C3 (RMB / ton). In order to reduce the wastewater discharge of photovoltaic enterprises, the park can subsidize the use of reclaimed water to prepare pure water, with a subsidy price of C4 (RMB / ton), where C4≥0. When C1≥C 2无氟 +C3-C4, the enterprise will have the impetus to use the recycled water after the fluorine-free tail water of the sewage treatment plant is treated to meet the requirements of GB 3838-2002 Class III standard for pure water production. 2氟 When C1≥C 2氟 +C3-C4, the enterprise will have the impetus to use the recycled water after the fluorine-containing tail water of the sewage treatment plant is treated to meet the requirements of GB 3838-2002 Class III standard for pure water production. S3: tertiary pollution reduction and water saving strategy The fluorine-containing wastewater and the non-fluorine-containing wastewater are treated separately, and then are transported to a sewage treatment plant. The fluorine-containing wastewater is discharged after treatment, and the non-fluorine-containing wastewater is used for ecological water supplement. The key physical and chemical indexes of the non-fluorine-containing wastewater used for ecological water supplement can reach: fluoride (calculated as F) ≤1 mg / L, sulfate (SO4 2- ) ≤500 mg / L, and chloride (Cl) ≤250 mg / L.

2. The integrated pollution-reducing and water-saving method for treating and recycling wastewater in a photovoltaic industrial park according to claim 1, characterized in that: In the internal recycling of the pull rod slice production wastewater, the fluorine-containing section wastewater accounts for 14.3% of the enterprise tap water intake, the non-fluorine-containing section wastewater is reused after treatment, and the fresh water intake amount is reduced by 26.7%.

3. The integrated pollution-reducing and water-saving method for treating and recycling wastewater in a photovoltaic industrial park according to claim 1, characterized in that: The yield of pure water prepared by the pull rod slice enterprise through the pure water station is 51.1%, and the yield of pure water prepared by the photovoltaic enterprise through the pure water station is 61%.

4. The integrated pollution-reducing and water-saving method for treating and recycling wastewater in a photovoltaic industrial park according to claim 1, characterized in that: In the internal recycling of the photovoltaic cell production wastewater, the fluorine-containing section wastewater accounts for 59.8% of the enterprise tap water intake, the non-fluorine-containing section wastewater is reused after treatment, and the fresh water intake amount is reduced by 15.2%.

5. The integrated pollution-reducing and water-saving method for treating and recycling wastewater in a photovoltaic industrial park according to claim 1, characterized in that: In the ecological water replenishment link, the fluoride, sulfate, and chloride concentrations of the fluoride-free wastewater used for ecological water replenishment need to be monitored regularly, with a monitoring frequency of no less than once a week, to ensure that the fluoride (calculated as F) is ≤1 mg / L, the sulfate (SO4 2- ) is ≤500 mg / L, and the chloride (Cl) is ≤250 mg / L.

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