Integral pollution-reducing and water-saving method for sewage treatment and recycling in photovoltaic industrial park

Abstract

The invention relates to the technical field of sewage treatment and water resource recycling, in particular to an integral sewage-reducing and water-saving method for sewage treatment and recycling in a photovoltaic industrial park, which comprises a primary sewage-reducing and water-saving strategy, internal circulation of pull rod slicing production wastewater and internal circulation of photovoltaic cell production wastewater. According to the second-stage pollution-reducing and water-saving strategy, after tail water of a sewage treatment plant in the park is treated, the tail water serves as recycled water to be provided for enterprises and used for production and living links with non-pure water requirements; after being treated, the tail water of the sewage treatment plant is supplied to enterprises as reclaimed water for pure water production; according to the three-stage pollution-reducing and water-saving strategy, fluorine-containing wastewater and fluorine-free wastewater of enterprises are treated according to quality and conveyed to a sewage treatment plant according to quality, so that the fluorine-containing wastewater treatment cost of the sewage treatment plant is reduced, the fluorine-free regenerated water amount is increased, and the influence of photovoltaic industrial wastewater on the water ecological environment is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment and water resource recycling, and specifically to an overall pollution reduction and water saving method for sewage treatment and recycling in a photovoltaic industrial park. Background Art

[0002] Guided by the "dual carbon" goals, the global energy structure is accelerating its transition to a green, low-carbon one. As a key 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. Leveraging their respective resource advantages, industrial foundations, and policy support, Jiangsu, Inner Mongolia, and Sichuan have established specialized photovoltaic industrial parks, becoming core regions for the development of China's photovoltaic industry.

[0003] Amidst the booming photovoltaic industry, the issue of industrial wastewater treatment in photovoltaic industrial parks has become increasingly prominent. The photovoltaic industry, particularly in key processes such as monocrystalline silicon ingot drawing and slicing, and cell production, generates large quantities of industrial wastewater. This wastewater exhibits significant water quality characteristics, with fluoride, a characteristic pollutant, occurring at high concentrations. For example, in wastewater discharged from some monocrystalline silicon production plants, fluoride concentrations can reach 100-500 mg / L, far exceeding the environmental carrying capacity. Furthermore, the wastewater also contains high concentrations of salts such as sulfates and chlorides. These salts not only complicate wastewater treatment but also significantly impact the aquatic ecosystem. Discharge of high concentrations of fluoride and other salts into water bodies without effective treatment can cause multiple detrimental effects on aquatic ecosystems. Fluoride can disrupt the normal physiological functions of fish, affecting their growth and reproduction. Studies have shown that when fluoride concentrations in water reach 5 mg / L, fish growth is significantly slowed, reproductive capacity is inhibited, egg hatchability is reduced, and deformity rates among juveniles increase. High concentrations of salts will change the osmotic pressure of the water, affect the normal growth of aquatic plants, destroy the ecological balance of the water, and thus affect the stability and health of the entire aquatic ecosystem.

[0004] Faced with a challenging wastewater treatment situation, domestic photovoltaic parks have developed a traditional model for wastewater treatment: first, fluoride removal pretreatment is carried out within the photovoltaic enterprise. By adding chemical agents such as calcium salts, the enterprise converts fluoride ions into insoluble fluoride precipitates, initially reducing the fluoride concentration in the wastewater. Subsequently, the wastewater is transported to the park's sewage treatment facilities, where the fluoride-containing wastewater undergoes a two-stage fluoride removal treatment. After this series of treatment processes, the wastewater generally meets the industry emission standard of 10mg / L. However, for some areas with more fragile ecological environments and higher environmental management needs, relying solely on the above-mentioned end-of-pipe treatment methods is difficult to further reduce fluoride concentrations and meet more stringent environmental protection requirements.

[0005] Problems with this system:

[0006] (1) Fluoride removal in enterprises and sewage treatment plants generally adopt similar two-stage in-depth defluoridation treatment processes. Excessive treatment in enterprises increases the difficulty of defluoridation in sewage treatment plants.

[0007] (2) Excessive fluoride removal by enterprises and sewage treatment plants results in excessively high concentrations of chloride ions, sulfate ions, and total salt in wastewater discharged from industrial parks, causing secondary pollution.

[0008] (3) Photovoltaic enterprises have high requirements for fresh water and use a large amount of fresh water. 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 recovery and reuse of fluorine-containing wastewater in the photovoltaic industry

[0011] Description: The present invention provides a process for the resource recovery and reuse of fluorine-containing wastewater in the photovoltaic industry, which comprises classifying and collecting concentrated acid wastewater, concentrated alkali wastewater, dilute acid wastewater and dilute alkali wastewater; adding sodium salt or potassium salt to the concentrated acid wastewater according to the fluorosilicate ion concentration of the concentrated acid wastewater for crystallization reaction to obtain fluorosilicate, and adding calcium salt to the concentrated acid wastewater according to the fluoride ion concentration of the concentrated acid wastewater for crystallization reaction to obtain calcium fluoride; sending the dilute alkali wastewater and the dilute acid wastewater into a reaction tank for defluorination treatment, and then sending them into a sedimentation tank for precipitation treatment, and then chemically softening treatment, and then passing through a sand filter, an activated carbon filter, a resin softener and a reverse osmosis device to obtain product water; the system effluent after the crystallization reaction of the concentrated acid wastewater and the concentrated alkali wastewater are sent to the reaction tank for defluorination treatment, and then sent to the sedimentation tank for precipitation treatment, and then passed through an evaporator to obtain condensed product water. In addition, a system for the resource recovery and reuse of fluorine-containing wastewater in the photovoltaic industry is provided.

[0012] Differences: This technology only addresses the end-of-pipe treatment of fluoride-containing wastewaters from photovoltaic cell manufacturers: concentrated acid, concentrated alkali, dilute acid, and dilute alkali. It reuses the dilute acid and dilute alkali wastewater with low salt content; conducts secondary resource recovery for the concentrated acid wastewater with high fluoride ion concentration; and evaporates the concentrated alkali wastewater with high organic matter concentration and other backwash water. This technology uses activated carbon, resin, and reverse osmosis, resulting in high treatment costs. This technology does not address each of these four chlorine-containing wastewaters individually at the end of the process. Instead, it separates all water used by photovoltaic enterprises into fluoride-containing and non-fluoride-containing wastewater. The non-fluoride-containing wastewater is recycled for other processes within the enterprise, while the fluoride-containing wastewater is treated separately. This technology differs from this approach by not requiring processes such as reverse osmosis, which significantly increase treatment costs. Furthermore, this technology also addresses the treatment of fluoride-containing wastewater from rod drawing and slicing plants. It also considers pollution reduction from a plant-wide and park-wide perspective, reducing the amount of fluoride-containing wastewater treated and discharged through water reuse and conservation. These are not considered in this technology.

[0013] (2) CN116062941B A method for collaborative defluorination and dechlorination of high-fluorine and chlorine wastewater in the photovoltaic industry

[0014] Description: A method for fluorine resource recovery and simultaneous deep defluorination and dechlorination of fluorine- and chlorine-containing wastewater from various sources during photovoltaic module production is provided. Concentrated acid wastewater is pumped into a reaction tank, where NaOH and NaAlO2 are slowly added to react with the fluoride ions in the concentrated acid wastewater. After the reaction is complete, solid-liquid separation is performed, and the precipitate undergoes deep dehydration and drying to produce cryolite. The supernatant is mixed with concentrated alkaline wastewater, dilute acid wastewater, and dilute alkaline wastewater, filtered through a membrane, and then fed into a capacitive deionization unit for defluorination and dechlorination. The electrode material of the capacitive deionization unit is iron-manganese-doped sludge-based carbon electrode. The produced water is then introduced into a deep defluorination tank, where lime milk is added to adjust the pH to 7-8. A chlorine-free defluoridant is then added, followed by PAM flocculation to accelerate sedimentation. Once the pH reaches the standard, the water is discharged. After fluorine recovery, capacitive deionization and dechlorination using iron-manganese-doped sludge-based electrodes, and deep defluorination, the effluent fluoride and chloride ion content meets national emission standards. In this method, after fluorine recovery - iron-manganese-doped sludge-based electrode capacitive deionization and dechlorination - deep defluoridation, the fluorine ion content in the effluent is 1-2 mg / L, and the chloride ion content is stably lower than 200 mg / L, which meets the national emission standards. In addition, the operating cost is low and cryolite products that meet the standards can be recovered.

[0015] Difference: This technology reduces the fluoride and chloride ion concentrations in the effluent through deep defluorination and dechlorination, but only considers the terminal treatment of four streams of fluoride-containing wastewater, namely concentrated acid, concentrated alkali, dilute acid, and dilute alkali. It does not consider pollution reduction from the perspective of the entire plant and the entire park, and does not reduce the treatment volume and discharge of fluoride-containing wastewater by recycling water and saving water. In addition, this method does not consider the removal of fluoride ions at concentration levels from 2 mg / L to below 1 mg / L, and does not clearly state the changes in sulfate concentration while reducing chloride. This technology fully considers the reuse and treatment of wastewater from the entire photovoltaic industry plant, reduces the amount of fluoride-containing wastewater, and simultaneously reduces the cost and treatment volume of fluoride-containing wastewater. It proposes a feasible path to control fluoride to below 1 mg / L, and simultaneously considers the reduction and management of chloride and sulfate through the total salt content index.

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

[0017] Description: This paper relates to a photovoltaic wastewater advanced treatment system and method. The system comprises a sequentially connected coagulation and sedimentation tank, a primary ozone advanced oxidation tank, a secondary ozone catalytic advanced oxidation tank, and a tertiary ozone catalytic advanced oxidation tank. The system is suitable for treating COD concentrations of 70 to 100 mg / L. After biochemical treatment, photovoltaic wastewater cannot meet the discharge requirement of a COD concentration below 25 mg / L. Further advanced treatment in this system can reduce the final effluent COD to below 25 mg / L, or even below 20 mg / L.

[0018] Differences: This technology only considers COD, not fluoride, a characteristic pollutant in the photovoltaic industry. It also considers only the wastewater treatment of photovoltaic enterprises, not the linkage between photovoltaic park enterprises and wastewater treatment facilities. This technology fully considers the reduction of fluoride.

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

[0020] Description: It relates to a water resource optimization configuration system and method for near-zero discharge of sewage in an industrial park. The system includes a river ecosystem, industrial enterprises in the industrial park, enterprise sewage treatment stations, a sewage treatment plant in the industrial park, a tailwater purification wetland for the sewage treatment plant in the industrial park, and a recycled water plant. The method clarifies the objective function and constraints based on the water use and drainage characteristics of different enterprises in the industrial park, and constructs a mathematical model for optimizing the allocation of water resources in the industrial park with the goal of minimizing fresh water consumption, minimizing economic costs, and maximizing environmental benefits. The mathematical model is solved using a genetic algorithm to obtain and output the optimal water resource configuration plan for the industrial park. The present invention clarifies the optimal effluent destination and water volume of each level of treatment facilities, and estimates the selection and treatment degree of water treatment processes at each level, providing a scientific basis for the management of the zero-discharge network of sewage in industrial parks, the design of sewage treatment facilities, and the upgrading and transformation of sewage treatment technologies.

[0021] Difference: This technology is a universal water resource allocation method for recycled water utilization in industrial parks, and adopts a configuration method based on mathematical model algorithms; this technology is a recycled water allocation method for photovoltaic parks, and carries out water resource allocation around the problems of fluoride, chloride, sulfate, etc. unique to photovoltaic parks, and explores the organic relationship between rod drawing and slicing companies, battery cell production companies and park sewage treatment plants. The water resource allocation method adopted is based on the principle of water withdrawal and use balance.

[0022] (5) CN106630388B An overall energy-saving method for industrial park sewage treatment

[0023] Description: This optimization scheme optimizes the overall wastewater treatment process in industrial parks, comprehensively considering the relationship between enterprise wastewater pretreatment and the park's terminal wastewater treatment processes. This approach eliminates the aerobic biochemical process in enterprise wastewater pretreatment, allowing organic matter to be treated at the park's wastewater treatment plant. This addresses the carbon source shortage in the denitrification and denitrification stages of the terminal wastewater treatment plant. Furthermore, an energy extraction process is incorporated into the park's wastewater treatment system, including enhanced primary treatment, high-load biochemical treatment, and sludge anaerobic digestion to recover energy. This reduces wastewater treatment energy consumption and achieves the goal of extracting energy from wastewater to feed back into wastewater treatment. This approach is particularly effective for industrial park wastewater treatment plants with a water volume exceeding 100,000 tons per day.

[0024] Difference: This technology is an overall energy-saving method for universal industrial park wastewater treatment, mainly targeting industrial park wastewater treatment with a water treatment volume greater than 100,000 tons / day. The main technical methods adopted are to improve the dosage of chemical agents, treatment processes, energy recovery systems and waste resource utilization. It focuses on solving the application of duplicate construction of aerobic biochemical process links in the end-of-waste treatment of enterprises and parks. It does not propose targeted water-saving and pollution reduction strategies based on the characteristics of the photovoltaic industry and the layout of photovoltaic industrial parks. This technology is an industry wastewater treatment strategy for the photovoltaic industry and photovoltaic industrial parks. It does not consider the treatment scale of sewage treatment plants and does not involve energy conservation issues. Instead, it carries out water resource allocation and tertiary pollution reduction around pollution indicators such as fluoride, chloride, and sulfate that are unique to photovoltaic parks.

[0025] (6) CN111470740A Industrial Park Sewage Intelligent Management and Control Platform and Control Method

[0026] Description: An intelligent wastewater management and control platform for industrial parks includes a water quality regulation system, a water quality monitoring system, and an emergency disposal system. The water quality regulation system includes a separate collection unit and a homogenization regulation unit, which collect and homogenize wastewater from heavily polluting enterprises, lightly polluting enterprises, and residential areas, and then homogenizes and regulates the collected wastewater to the sewage treatment plant's biochemical system. The water quality monitoring system includes a monitoring unit, a data processing unit, and a control unit, which monitor wastewater quality at every stage of the platform, track enterprises with excessive discharges, predict the water quality characteristics of their discharges, and control the start and stop, flow rate, and residence time of each stage of the drainage system. The emergency disposal system treats accidental wastewater and delivers it to the sewage treatment plant's biochemical system. This platform enables separate wastewater collection and regulation, as well as emergency disposal of accidental wastewater. It also realizes real-time wastewater quality analysis, monitoring, and allocation, resulting in greater control and safety at the sewage treatment plant's front-end wastewater source.

[0027] Difference: This technology is a technology for developing and controlling intelligent wastewater management and control platforms for universal industrial parks. It focuses on changing the current situation of low control over industrial wastewater source strength, poor water allocation capacity of sewage treatment plants, and low intelligent management and control capabilities. It is based on the use of computational analysis to optimize the link between enterprise wastewater and park sewage treatment plants, realize the discharge and allocation of industrial wastewater, and trace enterprises that exceed emission standards. This technology is an industry wastewater treatment strategy for the photovoltaic industry and photovoltaic industrial parks, focusing on the emission and treatment of characteristic pollutants such as fluoride in photovoltaic wastewater. This technology is a three-level pollution reduction and water conservation strategy, including three levels: in-plant, plant-to-plant, and water replenishment. It is essentially different from the focus and technical path of this technology. Summary of the Invention

[0028] The purpose of the present invention is to provide an overall pollution reduction and water-saving method for sewage treatment and recycling in photovoltaic industrial parks. A three-level pollution reduction and water-saving strategy and method of "in-plant circulation", "factory reuse" and "ecological water replenishment" are designed to enable the use of tail water from photovoltaic industrial parks for ecological water replenishment, reduce fluoride emissions from the park, and at the same time reduce the total salt content in the wastewater.

[0029] To achieve the above objectives, the present invention provides the following technical solution: an integrated pollution reduction and water conservation method for sewage treatment and recycling in a photovoltaic industrial park, comprising the following steps:

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

[0031] S1.1: Internal circulation of wastewater from rod drawing and slicing production;

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

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

[0034] S2.1: After the tailwater from the photovoltaic park sewage treatment plant is treated to meet the surface water Class III standard requirements of GB 3838-2002 Surface Water Environmental Quality Standard, it will be provided to enterprises as recycled water for use in production and living areas that require non-pure water.

[0035] S2.2: After the tailwater from the photovoltaic park sewage treatment plant is treated to meet the requirements of GB 3838-2002 Class III standard, it will be provided to enterprises as recycled water for pure water production;

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

[0037] S3.1: The enterprise's fluoride-containing wastewater and non-fluoride-containing wastewater are treated separately and transported to the sewage treatment plant according to their quality. This allows the sewage treatment plant to reduce the cost of treating fluoride-containing wastewater while increasing the amount of non-fluoride-containing recycled water, making it more suitable for ecological water replenishment;

[0038] S3.2: The PV park sewage treatment plant has two outlets for fluoride-containing wastewater and non-fluoride-containing wastewater into the river. Fluoride-containing wastewater will be discharged after treatment, and non-fluoride-containing wastewater will be used for ecological water replenishment;

[0039] S3.3: The key physical and chemical indicators of non-fluorinated wastewater used for ecological water replenishment can be as follows: fluoride (in F) ≤ 1 mg / L, sulfate (SO4 2- )≤500mg / L, chloride (Cl)≤250mg / L.

[0040] Preferably, in the internal circulation of the rod drawing and slicing production wastewater, the enterprise tap water intake is 100%, the fluorine-containing section wastewater accounts for 14.3%, and the non-fluorine section wastewater is reused after treatment, reducing the fresh water intake by 26.7%.

[0041] Preferably, the yield of pure water prepared by the rod drawing and 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 circulation of the photovoltaic cell production wastewater, the enterprise tap water intake is 100%, the fluorine-containing section wastewater accounts for 59.8%, and the non-fluorine section wastewater is reused after treatment, reducing the fresh water intake by 15.2%.

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

[0044] Preferably, in the "factory reuse" water resource optimization allocation model, the constraints include: when the fresh water price C1 ≥ the fluorine-free wastewater treatment cost C2 + the fluorine-free ultrafiltration reverse osmosis cost loss C3 - the subsidy price C4, the enterprise uses the fluorine-free tail water regeneration water for pure water production;

[0045] When C1≥fluorine-containing wastewater treatment cost C2+C3-C4, the enterprise uses fluorine-containing tail water regeneration water for pure water production.

[0046] Preferably, in the three-level pollution reduction and water conservation strategy, the fluorine-free wastewater used for ecological water replenishment is treated by separation to reduce the salt content, thereby avoiding the impact on young fish in the water body.

[0047] Preferably, in the ecological water replenishment link, the fluoride-free wastewater used for ecological water replenishment needs to be regularly monitored for fluoride, sulfate, and chloride concentrations, with a monitoring frequency of not less than once a week to ensure that fluoride (in F) is ≤1 mg / L, sulfate (SO4 2- )≤500mg / L, chloride (Cl)≤250mg / L.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. The photovoltaic industrial park's integrated approach to wastewater treatment and recycling reduces pollution and conserves water. Through a primary pollution-reduction and water-saving strategy of on-site recycling and a secondary pollution-reduction and water-saving strategy of on-site reuse, this approach separates fluoride-containing wastewater from non-fluoride-containing wastewater, transporting the fluoride-containing wastewater to the industrial park's wastewater treatment plant for single-line treatment. This addresses the common problem of photovoltaic companies over-defluoridating fluoride-containing wastewater before leaving the plant, making it difficult for wastewater treatment plants to remove fluoride. This approach reduces the two repeated defluoridation steps to a single defluoridation step at the wastewater treatment plant, reducing both the difficulty and cost of defluoridation.

[0050] 2. The photovoltaic industrial park's integrated approach to wastewater treatment and recycling reduces pollution and water conservation. This approach avoids repeated defluorination, reduces the repeated addition of defluoridation agents, and reduces the input of sulfate and chloride ions in the defluoridation agents, indirectly reducing the total salt content in the tailwater discharged from the photovoltaic industrial park's wastewater treatment plant. The in-plant pollution reduction and water conservation processes at the rod drawing and slicing plants and photovoltaic cell plants were modified. All water used by the photovoltaic plants is treated separately, separating fluoride-containing and non-fluoride-containing wastewater. Fluoride-free wastewater is recycled for other plant processes, while fluoride-containing wastewater is treated separately. This approach reduces fluoride discharge concentrations and reduces treatment costs without resorting to high-cost wastewater treatment technologies such as ultrafiltration and reverse osmosis.

[0051] 3. The overall pollution reduction and water conservation method for sewage treatment and recycling in the photovoltaic industrial park can reduce the fresh water consumption of rod drawing and slicing enterprises by 26.7% and photovoltaic cell enterprises by 15.2% through the first-level water conservation strategy. Through the second-level water conservation strategy, the tail water of the sewage treatment plant in the photovoltaic industrial park can be treated to meet the surface water Class III standard requirements in GB 3838-2002 Surface Water Environmental Quality Standard, and then provided to enterprises as recycled water for production and living links with non-pure water needs. After being subsidized, it can be used for pure water preparation, thereby improving the recycling rate of wastewater in the photovoltaic industrial park and reducing the overall fresh water consumption of the photovoltaic industrial park.

[0052] 4. The photovoltaic industrial park's overall pollution reduction and water conservation method for wastewater treatment and recycling has reduced the overall cost and volume of fluoride-containing wastewater treatment in the photovoltaic industrial park, proposed a feasible path to control fluoride to less than 1 mg / L, and simultaneously considered the reduction and control of chloride and sulfate through the total salt content index. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

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

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

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

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

[0058] Figure 5 This is a schematic diagram of the overall sewage treatment strategy after the photovoltaic industrial park transformation of the present invention. DETAILED DESCRIPTION

[0059] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0060] See also Figure 1-Figure 5 The present invention provides a technical solution: an overall pollution reduction and water saving method for sewage treatment and recycling in photovoltaic industrial parks.

[0061] The following steps are involved:

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

[0063] S1.1: Internal circulation of wastewater from rod drawing and slicing production;

[0064] Internal circulation of wastewater from rod drawing and slicing production (see the original water balance of rod drawing and slicing enterprises Figure 1 Rod drawing and slicing refers to the production process of cleaning and pulling polysilicon raw materials into polysilicon rods, and then slicing them into solar cell raw materials.

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

[0066] (1) Rod drawing and slicing enterprises use tap water to prepare pure water through a pure water station (pure water preparation rate is 51.1%). 17.7% of the total water intake is used in the fluorine-containing process, including the acid washing and rinsing sections of the silicon material cleaning unit, as well as ultrasonic cleaning, rinsing and other water-related sections. Excluding evaporation losses, this part of the fluorine-containing wastewater discharge accounts for 14.3%.

[0067] (2) Rod drawing and slicing enterprises use tap water to prepare pure water through a pure water station (pure water preparation rate is 51.1%). 33.4% of the total water intake is used in the fluorine-free process, including all water-related processes such as squaring, rounding, chamfering, sizing, and polishing in the machining unit; and all water-related processes such as stick gluing, slicing, pre-cleaning and degumming, cleaning, and drying in the slicing unit. This part discharges fluorine-free wastewater. Excluding evaporation loss, fluorine-free wastewater accounts for 26.7%.

[0068] (3) After pre-treatment at the in-plant wastewater treatment facility, the non-fluorinated wastewater from the rod-drawing and slicing enterprises is reused for other production processes and greening needs of the rod-drawing and slicing enterprises (water demand is 36.3%, with a loss rate of approximately 70%, and all non-fluorinated wastewater can be used). 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 the utilization rate of water resources. At the same time, this in-plant circulation method avoids the enterprise's excessive wastewater treatment, simplifies the process that may have required multiple treatments, and reduces the difficulty and cost of treatment.

[0069] (4) After the fluoride-containing wastewater (14.3%) of the rod-drawing and slicing enterprises passes through the fluoride-containing wastewater treatment pool, the fluoride concentration is controlled at ≤10mg / L and connected to the fluoride-containing wastewater treatment section of the industrial park sewage treatment plant through a single pipe. Compared with the original 63.3% total outlet discharge, the drainage is reduced by 41%. This treatment method enables the fluoride-containing wastewater to be specially treated, improves the treatment efficiency, and also reduces the burden on the subsequent centralized treatment of the park sewage treatment plant. (The water balance of the rod-drawing and slicing enterprises after the transformation is shown in Figure 2 )

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

[0071] Photovoltaic cell production wastewater internal circulation (a photovoltaic cell enterprise water balance see Figure 3 Photovoltaic cell production refers to the production process of photovoltaic cells using the Topcon solar cell process as the mainstream. The production process includes texturing - front boron diffusion - SE - thermal oxidation - (BSG removal + alkaline polishing) - Poly - annealing - (PSG removal + RCA) - ALD - front coating - back coating - screen printing - sintering - light injection - testing and sorting - packaging.

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

[0073] (1) Photovoltaic cell companies use tap water to prepare pure water through a pure water station (pure water preparation rate is 61%). 57.5% of the total water intake is used in the fluorine-containing section, including the texturing, BSG removal + alkali polishing, and PSG removal + RCA sections. This section discharges four types of fluorine-containing wastewater: concentrated acid water, concentrated alkaline water, dilute acid water, and dilute alkaline water. Excluding evaporation losses and taking into account chemical substitution, the final fluorine-containing wastewater is 59.8%.

[0074] (2) PV cell companies use tap water to prepare pure water through a pure water station (pure water preparation rate is 61%). 3.5% of the total water intake is used in the fluorine-free process, including all water-related processes other than process (1). This part of the wastewater discharged is fluorine-free, accounting for 3.5%.

[0075] (3) The pure water station of the photovoltaic cell enterprise produces 20% concentrated water, which is mixed with fluoride-free wastewater (3.5%) and a small amount of domestic water to form 28.7% fluoride-free wastewater. After purification through the sewage treatment facilities in the factory, it is reused for other production links of the photovoltaic cell enterprise and greening water needs (water demand 15.2%, loss rate of about 11.7%). This measure reduces the amount of fresh water used by 15.2%, greatly improving the recycling efficiency of water resources. Moreover, in this process, the reuse of wastewater is achieved without the use of high-cost sewage treatment technologies such as ultrafiltration and reverse osmosis, which effectively reduces the treatment cost while reducing the concentration of fluoride emissions.

[0076] (4) After the fluoride-containing wastewater (59.8%) of photovoltaic cell enterprises passes through the fluoride-containing wastewater treatment pool, the fluoride concentration is controlled at ≤10mg / L and connected to the fluoride-containing wastewater treatment section of the industrial park sewage treatment plant through a single pipe. The total tailwater discharge volume is reduced by 75% compared to the original 88.5%. This separate treatment method allows fluoride-containing wastewater and non-fluoride-containing wastewater to be treated in a targeted manner, laying a good foundation for the subsequent overall sewage treatment of the park. (See the water balance after the transformation of the photovoltaic cell enterprise. Figure 4 )

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

[0078] S2.1: After the tailwater from the park's sewage treatment plant is treated to meet the Class III surface water standard in GB 3838-2002, the tailwater will be provided to enterprises as recycled water for use in production and living areas that require non-pure water.

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

[0080] Assuming there are m rod drawing and slicing companies and n battery cell production companies in the park, the mathematical model can be expressed as:

[0081]

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

[0083]

[0084] Where Q 园区进水is the water inflow of the industrial park sewage treatment plant, Q 企业排 is the drainage volume of all industrial enterprises in the industrial park, Q i排 is the displacement of the i-th rod-pulling and slicing enterprise, Q i排 is the drainage volume of the pth photovoltaic cell enterprise.

[0085] Q i排 =Q i1 +Q i2 (Formula 3)

[0086] Where Q i1 Q is the amount of fluorine-free wastewater discharged from the i-th rod drawing and slicing enterprise to the industrial park sewage treatment plant through the main outlet, i2 The amount of fluorine-containing wastewater discharged from the i-th rod drawing and slicing enterprise is transported to the industrial park sewage treatment plant through a single pipe.

[0087] Q p排 =Q p1 +Q p2 (Formula 4)

[0088] Where Q p1 Q is the amount of fluorine-free wastewater discharged from the p-th photovoltaic cell enterprise to the industrial park sewage treatment plant through the main outlet, p2 The amount of fluorine-containing wastewater discharged from the pth photovoltaic cell enterprise is transported to the industrial park sewage treatment plant through a single pipe.

[0089] Fluoride-free wastewater delivered to the industrial park sewage treatment plant through the main outlet can be provided as recycled water to enterprises for use in production and living areas with non-pure water needs, and can also be used for park greening after being treated to meet the surface water Class III standard requirements in GB 3838-2002 Surface Water Environmental Quality Standard. The maximum recycled water production volume is:

[0090]

[0091] Where Q 再生 is the recycled water production of the entire industrial park. i1 Q is the amount of fluorine-free wastewater discharged from the i-th rod drawing and slicing enterprise to the industrial park sewage treatment plant through the main outlet, p1 It is the discharge volume of fluorine-free wastewater transported by the p-th photovoltaic cell enterprise to the industrial park sewage treatment plant through the main outlet.

[0092] By treating wastewater treatment plant tailwater and reusing it as recycled water to meet the non-pure water needs of businesses, the photovoltaic industrial park has significantly improved its wastewater recycling capacity. For example, rod drawing and slicing companies, which still require 9.6% of their non-pure water for production and daily life, can use recycled water from the park instead of fresh water. This has significantly reduced the photovoltaic industrial park's overall fresh water consumption, effectively conserving water resources.

[0093] S2.2: After the tailwater from the sewage treatment plant is treated to meet the requirements of GB 3838-2002 Class III standard, it will be provided to enterprises as recycled water for pure water production;

[0094] After achieving the first-level pollution reduction and water conservation strategy, the rod drawing and slicing enterprises still have 9.6% of their non-pure water demand in production and living stages, which can use the park's recycled water instead of fresh water. Photovoltaic cell enterprises no longer have any demand for recycled water in production and living stages. 再生 If there are no other industrial enterprises in the park, it may not be possible to fully absorb the wastewater. To further promote water conservation in the photovoltaic industrial park, the tailwater from the sewage treatment plant is treated to meet the requirements of GB 3838-2002 Class III standards and then provided to enterprises as recycled water for pure water production.

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

[0096] The photovoltaic industrial park treats the wastewater treatment plant tail water to meet the requirements of GB 3838-2002 Class III standard. The treatment cost per ton of water is C 2氟 (Yuan / ton), non-fluorine wastewater C 2无氟 (Yuan / ton), this cost is collected in advance from the enterprise.

[0097] When photovoltaic companies use recycled water that meets the requirements of GB 3838-2002 Class III standards to prepare pure water, the cost loss of ultrafiltration and reverse osmosis will increase, which is converted into C3 (yuan / ton).

[0098] In order to reduce wastewater discharge from photovoltaic enterprises, the park can subsidize the use of recycled water to prepare pure water. The subsidy price is C4 (yuan / ton), C4 ≥ 0 (Formula 6).

[0099] When C1≥C 2无氟 When C1≥C2fluorine+C3-C4 (Formula 8), companies will be motivated to use recycled water from sewage treatment plants that has been treated 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 the subsidy price, companies will be more inclined to use fluoride-free tailwater reclaimed water for pure water production. Similarly, when the corresponding price conditions for fluoride-containing wastewater are met, companies will use fluoride-containing tailwater reclaimed water. This mechanism not only reduces the overall fluoride wastewater treatment cost and treatment volume of photovoltaic industrial parks, but also saves water costs for companies, achieving a win-win situation in both economic and environmental benefits.

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

[0102] S3.1: The enterprise's fluoride-containing wastewater and non-fluoride-containing wastewater are treated separately and transported to the sewage treatment plant according to their quality. This allows the sewage treatment plant to reduce the cost of treating fluoride-containing wastewater while increasing the amount of non-fluoride-containing recycled water, making it more suitable for ecological water replenishment;

[0103] Enterprises treat fluoride-containing wastewater and non-fluoride-containing wastewater separately and then deliver them to sewage treatment plants based on their quality. In this way, sewage treatment plants can adopt more targeted treatment processes for different types of wastewater, thereby reducing the treatment costs of fluoride-containing wastewater. At the same time, since non-fluoride-containing wastewater is better treated and utilized, the amount of non-fluoride-containing recycled water is increased, and this recycled water is more suitable for ecological water replenishment. In this process, the excessive addition of sulfate or chloride ions during sewage treatment, which leads to high total salt values ​​and affects young fish in the water body, is avoided. For example, according to an acute toxicity test on rare goby fry, the average swimming speed of rare goby fry exposed to chloride ions exceeding 250 mg / L is significantly lower than that of the clear water control group, which may have a certain inhibitory effect on the movement behavior of rare goby fry. Through separate treatment, the total salt content can be effectively controlled and the water ecological environment can be protected.

[0104] S3.2: The enterprise's fluoride-containing wastewater and non-fluoride-containing wastewater are separated into river discharge outlets. Fluoride-containing wastewater is discharged after treatment, and non-fluoride-containing wastewater is used for ecological water replenishment;

[0105] To better separate and utilize wastewater, the company separates fluoride-containing and non-fluoride-containing wastewater into river outlets. Fluoride-containing wastewater undergoes rigorous treatment and meets discharge standards before being discharged, ensuring no water pollution. Non-fluoride-containing wastewater, on the other hand, is treated and used for ecological replenishment, providing water resources and improving the surrounding ecological environment.

[0106] S3.3: The key physical and chemical indicators of non-fluorinated wastewater used for ecological water replenishment can be as follows: fluoride (in F) ≤ 1 mg / L, sulfate (SO4 2- )≤500mg / L, chloride (Cl)≤250mg / L.

[0107] While reducing fluoride emissions, avoid excessive addition of sulfate or chloride ions during sewage treatment, which can lead to high total salt values ​​and affect juvenile fish in the water (according to acute toxicity tests on rare goby fry, the average swimming speed of rare goby fry exposed to more than 250 mg / L of chloride ions was significantly lower than that of the clear water control group, regardless of whether it was in light or darkness, which may have a certain inhibitory effect on the movement behavior of rare goby fry).

[0108] In the ecological water replenishment link, the fluoride, sulfate and chloride concentrations of the fluoride-free wastewater used for ecological water replenishment should be monitored regularly, with a monitoring frequency of no less than once a week to ensure that the fluoride (in F) is ≤1mg / L, sulfate (SO4 2- )≤500mg / L, chloride (Cl - ) ≤ 250mg / L. Through this rigorous indicator control and regular monitoring, a feasible path has been proposed to control fluoride to below 1mg / L, further reducing fluoride emissions compared to traditional processes. At the same time, by controlling sulfate and chloride, the reduction and management of total salt content indicators are simultaneously considered, effectively reducing secondary pollution and protecting the health and stability of the aquatic ecosystem.

[0109] Secondary pollution reduction strategy and tertiary pollution reduction strategy are shown in Figure 5 .

[0110] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

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

Claims

1. An overall pollution reduction and water saving method for sewage treatment and recycling in photovoltaic industrial parks, characterized in that: The following steps are involved: S1: Primary pollution reduction and water conservation strategy S1.1: Internal circulation of wastewater from rod drawing and slicing production; S1.2: Internal circulation of photovoltaic cell production wastewater; S2: Secondary pollution reduction and water conservation strategy S2.1: After the tailwater from the photovoltaic park sewage treatment plant is treated to meet the surface water Class III standard requirements of GB 3838-2002 Surface Water Environmental Quality Standard, it will be provided to enterprises as recycled water for use in production and living areas that require non-pure water. S2.2: After the tailwater from the photovoltaic park sewage treatment plant is treated to meet the requirements of GB 3838-2002 Class III standard, it will be provided to enterprises as recycled water for pure water production; S3: Three-level pollution reduction and water conservation strategy S3.1: The enterprise's fluoride-containing wastewater and non-fluoride-containing wastewater are treated separately and transported to the photovoltaic park sewage treatment plant according to their quality. This allows the sewage treatment plant to reduce the cost of treating fluoride-containing wastewater while increasing the amount of fluoride-free recycled water, making it more suitable for ecological water replenishment; S3.2: The PV park sewage treatment plant has two outlets for fluoride-containing wastewater and non-fluoride-containing wastewater into the river. Fluoride-containing wastewater will be discharged after treatment, and non-fluoride-containing wastewater will be used for ecological water replenishment; S3.3: The key physical and chemical indicators of non-fluorinated wastewater used for ecological water replenishment can be as follows: fluoride (in F) ≤ 1 mg / L, sulfate (SO4 2- )≤500mg / L, chloride (Cl)≤250mg / L.

2. The integrated pollution reduction and water conservation method for sewage treatment and recycling in a photovoltaic industrial park according to claim 1, characterized in that: In the internal circulation of the rod drawing and slicing production wastewater, the enterprise's tap water intake is 100%, the fluorine-containing section wastewater accounts for 14.3%, and the non-fluorine-containing section wastewater is reused after treatment. The fresh water intake is reduced by 26.7%, avoiding excessive wastewater treatment by the enterprise, simplifying the process, and reducing the difficulty and cost of treatment.

3. The integrated pollution reduction and water conservation method for sewage treatment and recycling in a photovoltaic industrial park according to claim 1 is characterized by: The yield of pure water prepared by the rod drawing and 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%.

4. The integrated pollution reduction and water conservation method for sewage treatment and recycling in a photovoltaic industrial park according to claim 1, characterized in that: In the internal circulation of photovoltaic cell production wastewater, the enterprise's tap water intake is 100%, the fluorine-containing section wastewater accounts for 59.8%, and the non-fluorine-containing section wastewater is reused after treatment. The fresh water intake is reduced by 15.2%, the fluoride emission concentration is reduced, and the treatment cost is simultaneously reduced.

5. The integrated pollution reduction and water conservation method for sewage treatment and recycling in a photovoltaic industrial park according to claim 1 is characterized by: In the secondary pollution reduction and water conservation strategy, a water resource optimization allocation model for the park's "factory-to-factory reuse" based on water balance is constructed, with the goal of reducing fresh water consumption and minimizing the amount of fluoride-containing wastewater treated by the park's sewage treatment plants.

6. The integrated pollution reduction and water conservation method for sewage treatment and recycling in a photovoltaic industrial park according to claim 1, characterized in that: In the "factory reuse" water resource optimization allocation model, the constraints include: when the fresh water price C1 ≥ the fluorine-free wastewater treatment cost C2 + the fluorine-free ultrafiltration and reverse osmosis cost loss C3 - the subsidy price C4, the enterprise uses fluorine-free tail water regeneration water for pure water production; When C1≥fluorine-containing wastewater treatment cost C2+C3-C4, the enterprise uses fluorine-containing tail water regeneration water for pure water production.

7. The integrated pollution reduction and water conservation method for sewage treatment and recycling in a photovoltaic industrial park according to claim 1, characterized in that: In the three-level pollution reduction and water conservation strategy, the fluorine-free wastewater used for ecological water replenishment is treated by quality separation to reduce the total salt content, thereby avoiding the impact on young fish in the water body.

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

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