Photovoltaic wastewater resourceful treatment process

Abstract

The application discloses a photovoltaic wastewater resource treatment process and relates to the technical field of photovoltaic wastewater treatment. The process comprises the following steps: adding photovoltaic wastewater into a primary stirring crystallization pool to generate a mixed solution with a first rising flow rate, so that the mixed solution is separated into calcium fluoride crystals and primary treatment water containing calcium fluoride crystal nuclei; introducing the primary treatment water and a sodium carbonate precipitant into a crystallization fluidized bed to form calcium carbonate crystals and calcium carbonate nuclei by inducing the calcium fluoride crystal nuclei, and promoting the reaction solution to form a second rising flow rate, so that the reaction solution is separated into the calcium carbonate crystals and secondary treatment water containing the calcium carbonate nuclei; the calcium carbonate nuclei are arranged to flow into the crystallization fluidized bed; and the secondary treatment water is sequentially subjected to pH adjustment, nitrogen removal treatment, carbon removal treatment and filtration treatment to obtain fourth treatment water. The resource treatment process can separate crystalline bodies with different particle sizes, thereby improving the crystallization efficiency in fluorine removal treatment and hardness removal treatment.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic wastewater treatment technology, and specifically to a photovoltaic wastewater resource utilization treatment process. Background Technology

[0002] Wastewater discharged during the photovoltaic (PV) manufacturing process contains large amounts of fluoride and nitrate nitrogen. Excessive fluoride emissions can cause crop death, steel corrosion, and cancer in animals and humans, while excessive nitrate nitrogen emissions can lead to eutrophication of water bodies. Therefore, fluoride and nitrogen in PV manufacturing wastewater must be treated before discharge. Traditionally, fluoride in wastewater is treated by adding calcium hydroxide or calcium chloride to form calcium fluoride precipitate. However, traditional precipitation defluorination processes result in excessive calcium in the effluent, leading to high hardness in the treated water and causing serious problems such as scaling in pipes and equipment downstream. Furthermore, traditional coagulation and sedimentation can only remove fluoride ions from PV wastewater to 1 ppm-8 ppm, indicating poor defluorination efficiency.

[0003] Conventional defluorination processes typically involve adding excess calcium ions and using a fluidized bed crystallization method, followed by granulation with sodium carbonate precipitate in the fluidized bed to remove calcium. Fine, uniform silica sand or expensive fillers are used as seed crystals. However, the issue of calcium carbonate crystal size cannot be avoided during crystal discharge, and the crystals produced by the fluidized bed defluorination process are not uniform in size, with smaller nuclei mixing with larger crystals and being discharged from the reactor. In other words, existing defluorination and dehardening technologies suffer from the technical problem of low crystallization efficiency due to uneven calcium fluoride or calcium carbonate crystallization. Summary of the Invention

[0004] One objective of this invention is to provide a photovoltaic wastewater resource utilization treatment process to solve the technical problem of low crystallization efficiency in existing photovoltaic wastewater treatment processes.

[0005] Another objective of this invention is to improve the defluorination efficiency and quality of the resource recovery process.

[0006] According to the purpose of this invention, a process for the resource-based treatment of photovoltaic wastewater is provided, comprising the following steps:

[0007] Photovoltaic wastewater is added to a primary stirred crystallization tank containing a fluorination reaction solution to generate a mixed solution, wherein the fluorination reaction solution includes lime solution and fluorite powder;

[0008] The mixture is caused to form a first upward flow velocity, so that the mixture is separated into calcium fluoride crystals and primary treated water containing calcium fluoride crystal nuclei;

[0009] The primary treated water and a sodium carbonate precipitant of a preset concentration are introduced into a crystallization fluidized bed so that the sodium carbonate precipitant reacts with calcium ions in the primary treated water to generate calcium carbonate precipitate, and calcium carbonate crystals and calcium carbonate nuclei are induced by the calcium fluoride crystal nuclei to form calcium carbonate crystals.

[0010] The reaction solution formed by the sodium carbonate precipitant and the primary treated water is induced to form a second upward flow rate, so that the reaction solution is separated into calcium carbonate crystals and secondary treated water containing calcium carbonate crystal nuclei, the calcium carbonate crystal nuclei being arranged to flow into the crystallization fluidized bed;

[0011] The secondary treated water is subjected to pH adjustment, denitrification, and decarbonization treatment in sequence to obtain tertiary treated water;

[0012] The tertiary treated water is filtered to obtain quaternary treated water and concentrate. The concentrate is then subjected to defluorination and hardness removal treatments, followed by pH adjustment, denitrification, decarbonization, and filtration to obtain the quaternary treated water.

[0013] Optionally, the first upward flow velocity is any value in the range of 2 m / h to 15 m / h, and the second upward flow velocity is any value in the range of 50 m / h to 120 m / h.

[0014] Optionally, the fluorination reaction solution further includes:

[0015] A calcium chloride solution is used to react with fluoride ions in the photovoltaic wastewater to generate calcium fluoride.

[0016] Optionally, the lime solution in the fluorination reaction solution has a mass fraction ranging from 1.0% to 10.0%, and the calcium chloride solution has a mass fraction ranging from 1.0% to 5.0%.

[0017] Optionally, the preset concentration is any value in the range of 100 mg / L to 10000 mg / L.

[0018] Optionally, the sodium carbonate precipitant is prepared from the fourth-stage treated water and sodium carbonate.

[0019] Optionally, the filtration process includes ultrafiltration and reverse osmosis.

[0020] Optionally, the volume ratio of the fluorite powder is any value in the range of 30%-60%.

[0021] Optionally, the step of sequentially performing pH adjustment, denitrification, and decarbonization treatment on the secondary treated water to obtain tertiary treated water further includes:

[0022] The pH adjustment was performed using concentrated acidic wastewater.

[0023] Optionally, the pH after pH adjustment is any value in the range of 6.0-7.0.

[0024] This invention utilizes fluorite powder to induce the formation of calcium fluoride crystals and calcium fluoride nuclei, and separates these crystals under the action of a mixed solution with a first upward flow rate. This process yields calcium fluoride crystals with a water content of less than 1%. The smaller-sized calcium fluoride nuclei are effectively used as seed crystals in a fluidized bed to induce calcium carbonate precipitation, forming calcium carbonate crystals and nuclei. A reaction solution with a second upward flow rate removes the calcium carbonate crystals from the fluidized bed, while the calcium carbonate nuclei are recycled back into the fluidized bed as seed crystals to induce calcium carbonate precipitation. This process completes the hardening treatment and the recycling of calcium carbonate nuclei, achieving particle size separation between calcium fluoride and calcium carbonate crystals. It avoids the problem of uneven crystal size affecting crystallization efficiency during defluorination and hardening treatments, thus improving the crystallization efficiency and treatment effect of defluorination and hardening treatments.

[0025] Furthermore, the fluorination reaction solution of the present invention also includes a calcium chloride solution, which contains calcium ions that can combine with fluoride ions to form calcium fluoride precipitate. The lime solution and calcium chloride solution in the fluorination reaction solution work together to completely form calcium fluoride precipitate from the fluoride ions in the photovoltaic wastewater, thereby improving the fluoride removal efficiency and stability.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0027] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0028] Figure 1 This is a schematic flowchart of a resource recovery process according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of a resource recovery process according to an embodiment of the present invention. Detailed Implementation

[0030] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0031] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It is to be understood that the specific embodiments described herein are merely illustrative of this application and not intended to limit it. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0032] The terms “comprising” and “having”, and any variations thereof, in this application are intended to cover non-exclusive inclusion. For example, it may include a series of steps, but may also optionally include steps not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0033] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0034] Figure 1 This is a schematic flowchart of a resource recovery process according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a resource recovery process according to an embodiment of the present invention.

[0035] like Figure 1 As shown, the present invention provides a photovoltaic wastewater resource utilization treatment process, comprising the following steps:

[0036] Step S100: Photovoltaic wastewater is added to a primary stirred crystallization tank containing a fluorination reaction solution to generate a mixed solution, the fluorination reaction solution including lime solution and fluorite powder;

[0037] Step S200: Inducing the mixed solution to form a first upward flow velocity so that the mixed solution is separated into calcium fluoride crystals and primary treated water containing calcium fluoride crystal nuclei;

[0038] Step S300: The primary treated water and sodium carbonate precipitant with a preset concentration are introduced into a crystallization fluidized bed so that the sodium carbonate precipitant reacts with the calcium ions in the primary treated water to generate calcium carbonate precipitate, and calcium carbonate crystals and calcium carbonate nuclei are induced by calcium fluoride crystal nuclei to form calcium carbonate crystals.

[0039] Step S400: The reaction solution formed by sodium carbonate precipitant and primary treated water is made to form a second upward flow rate, so that the reaction solution is separated into calcium carbonate crystals and secondary treated water containing calcium carbonate crystal nuclei, and the calcium carbonate crystal nuclei are set to flow into the crystallization fluidized bed.

[0040] Step S500: The secondary treated water is subjected to pH adjustment, denitrification treatment, and decarbonization treatment in sequence to obtain tertiary treated water;

[0041] Step S600: The tertiary treated water is filtered to obtain quaternary treated water and concentrate. The concentrate is then subjected to defluorination and hardness removal treatments, as well as pH adjustment, denitrification, decarbonization, and filtration to obtain the quaternary treated water.

[0042] In this embodiment, fluoride ions in the photovoltaic wastewater first react with calcium ions in the lime solution of the fluorination reaction solution to form a calcium fluoride solution. Under the action of fluorite powder, calcium fluoride crystals and calcium fluoride crystal nuclei are formed. Due to the first upward flow velocity of the mixed solution, the primary treated water containing calcium fluoride crystals and calcium fluoride crystal nuclei can be separated to achieve defluorination. Calcium ions in the primary treated water react with carbonate ions in the calcium carbonate precipitant to form calcium carbonate precipitate. Under the action of calcium fluoride crystal nuclei, calcium carbonate crystals and calcium carbonate crystal nuclei are formed. The reaction solution has a second upward flow velocity to form calcium carbonate crystals and secondary treated water containing calcium carbonate crystal nuclei. The calcium carbonate crystals flow from the crystallization fluidized bed... The process involves separation, with calcium carbonate nuclei flowing into a fluidized bed of crystallization. This fluidized bed replaces the calcium fluoride nuclei, further inducing calcium carbonate precipitation to form calcium carbonate crystals and nuclei, thus achieving hardness removal. The secondary treated water undergoes sequential pH adjustment, denitrification, and decarbonation to obtain tertiary treated water. This tertiary treated water is then filtered to obtain treated water and concentrate. The concentrate undergoes further defluorination and hardness removal, followed by pH adjustment, denitrification, decarbonation, and filtration to obtain quaternary treated water. This quaternary treated water is fresh water that meets discharge standards, thus achieving resource recovery of photovoltaic wastewater and yielding directly usable calcium fluoride crystals, calcium carbonate crystals, and quaternary treated water. Here, the particle size of calcium fluoride crystals is any value within the range of 30μm-100μm, the particle size of calcium fluoride nuclei is any value less than 30μm, the particle size of calcium carbonate crystals is any value within the range of 0.2mm-2.0mm, and the particle size of calcium carbonate nuclei is any value less than 0.2mm.

[0043] In this embodiment, calcium fluoride crystals and nuclei are induced to form using fluorite powder. These crystals are then separated under the action of a mixed solution with a first upward flow rate, resulting in calcium fluoride crystals with a water content of less than 1%. The smaller-sized calcium fluoride nuclei are effectively used as seed crystals in a fluidized bed to induce calcium carbonate precipitation, forming calcium carbonate crystals and nuclei. Calcium carbonate crystals are discharged from the fluidized bed via a reaction solution with a second upward flow rate, while calcium carbonate nuclei are recycled back into the fluidized bed as seed crystals to induce calcium carbonate precipitation. This process completes the hardening treatment and the recycling of calcium carbonate nuclei, achieving particle size separation between calcium fluoride and calcium carbonate crystals. It avoids the problem of uneven crystal size affecting crystallization efficiency during defluorination and hardening treatments, thus improving the crystallization efficiency and treatment effect of defluorination and hardening treatments.

[0044] In steps S100 and S200, the defluorination treatment of photovoltaic wastewater is carried out in a primary stirred crystallization tank, which contains lime solution and fluorite powder. After the photovoltaic wastewater is added to the primary stirred crystallization tank, it reacts and crystallizes. The solution containing calcium fluoride crystal nuclei obtained by separating the mixed solution enters the primary sedimentation tank. After sedimentation, the primary treated water and calcium fluoride crystal nuclei flow into the crystallization fluidized bed for further de-hardening treatment. This separates the calcium fluoride crystals and calcium fluoride crystal nuclei, and eliminates the need to add external seed crystals in the subsequent de-hardening treatment, effectively integrating resources and reducing process costs.

[0045] In steps S300 and S400, the hardness removal treatment of photovoltaic wastewater is carried out in a crystallization fluidized bed. Specifically, primary treated water containing calcium ions and calcium fluoride crystal nuclei, along with a calcium carbonate precipitant, are simultaneously introduced into the crystallization fluidized bed. Calcium fluoride acts as a seed crystal to induce the formation of calcium carbonate crystals and calcium carbonate crystal nuclei. The calcium carbonate crystals are then discharged from the crystallization fluidized bed via a reaction solution with a second upward flow rate. The solution containing calcium carbonate crystal nuclei enters a secondary sedimentation tank. After sedimentation, the secondary treated water undergoes further pH adjustment. Calcium carbonate crystal nuclei are continuously refluxed back into the crystallization fluidized bed, allowing them to fully exert their inducing effect and replace the initially added calcium fluoride crystal nuclei, resulting in high-purity calcium carbonate crystals. These high-purity calcium carbonate crystals can be directly utilized as a chemical raw material.

[0046] In step S500, the pH of the secondary treated water is adjusted sequentially to ensure that its acidity and alkalinity meet the requirements of subsequent denitrification and decarbonization treatments. The denitrification treatment utilizes a denitrifying fluidized bed to remove nitrogen and phosphorus from the photovoltaic wastewater. The decarbonization treatment utilizes an aerobic tank to remove carbon source organic matter from the photovoltaic wastewater. Suspended solids and particulate impurities in the photovoltaic wastewater are removed through filtration to obtain tertiary treated water. The tertiary treated water is then subjected to defluorination, hardness removal, pH adjustment, denitrification, decarbonization, and filtration in step S600 to obtain quaternary treated water that meets wastewater discharge standards, effectively improving the resource utilization rate of photovoltaic wastewater.

[0047] In step S500, the packing material of the denitrification fluidized bed in the denitrification treatment is an organometallic framework that has biocompatibility with sludge. The metal in the organometallic framework can be any one of aluminum-based, calcium-based, or iron-based metals. The metal in the organometallic framework can specifically chemically adsorb elements such as phosphorus and nitrogen in biological cells, thereby removing phosphorus and nitrogen from the pH-adjusted secondary treated water and further treating the organic elements in the photovoltaic wastewater.

[0048] In step S500, the aerobic tank in the decarbonization treatment is filled with dissolved oxygen. Under sufficient oxygen conditions, aerobic microorganisms use the organic matter in the photovoltaic wastewater as a carbon source and energy source to carry out aerobic respiration, decomposing the organic matter into carbon dioxide and water. This can effectively remove organic matter from the photovoltaic wastewater, reduce the chemical oxygen demand and biochemical oxygen demand in the photovoltaic wastewater, and thus improve the overall water quality of the photovoltaic wastewater.

[0049] In this embodiment, the pH value of the mixed solution during the defluorination process is any value within the range of 6.0-8.0. That is, the pH value of the mixed solution can be 6.0, 6.2, 6.4, 6.8, 7.0, 7.4, 7.6, or 8.0, or any value within the range of 6.0-8.0. In other words, when the pH value of the mixed solution is within the above range, the precipitation rate of calcium fluoride is relatively moderate, which is beneficial for controlling the precipitation process and ensuring the uniformity of the precipitation product. It also reduces interference from impurities and improves the purity of the precipitation product. When the pH value is less than 6.0, the precipitation rate may be slower, and the precipitate may contain more impurities. When the pH value is greater than 8.0, although the precipitation rate may be faster, it may also lead to smaller precipitate particles, loss of physical properties, and affect subsequent processing and application.

[0050] In a further embodiment, the first upward flow rate is any value within the range of 2 m / h to 15 m / h, and the second upward flow rate is any value within the range of 50 m / h to 120 m / h. That is, the upward flow rate of the mixed solution can be 2 m / h, 3 m / h, 4 m / h, 5 m / h, 6 m / h, 8 m / h, 10 m / h, 12 m / h, 14 m / h, or 15 m / h, or any value within the range of 2 m / h to 15 m / h, and the upward flow rate of the reaction solution can be 50 m / h, 60 m / h, 70 m / h, 80 m / h, 90 m / h, 100 m / h, 110 m / h, or 120 m / h, or any value within the range of 50 m / h to 120 m / h. In other words, when the upward flow rate of the mixed solution is within the above range, it can effectively separate calcium fluoride crystals and calcium fluoride crystal nuclei, avoiding the situation where the uneven particle size of the calcium fluoride crystals obtained during the defluorination process leads to a decrease in crystallization efficiency. When the upward flow rate of the reaction solution is within the above range, it can effectively separate calcium carbonate crystals and calcium carbonate crystal nuclei, avoiding the situation where the uneven particle size of the calcium carbonate crystals obtained during the hardening process leads to a decrease in crystallization efficiency, thereby ensuring the treatment effect of defluorination and hardening processes.

[0051] In a further embodiment, the fluorination reaction solution also includes a calcium chloride solution, which reacts with fluoride ions in the photovoltaic wastewater to generate calcium fluoride. In this embodiment, the fluorination reaction solution further includes a calcium chloride solution containing calcium ions capable of combining with fluoride ions to form calcium fluoride precipitate. The lime solution and calcium chloride solution in the fluorination reaction solution work together to completely precipitate fluoride ions in the photovoltaic wastewater into calcium fluoride, thereby improving defluorination efficiency and stability. Furthermore, the calcium chloride solution can more directly provide calcium ions, reducing the introduction of additional hydroxide ions due to pH adjustment, reducing the introduction of impurities into the photovoltaic wastewater, and further improving the efficiency of wastewater resource recovery.

[0052] In a further embodiment, the lime solution in the fluorination reaction solution has a mass fraction ranging from 1.0% to 10.0%, and the calcium chloride solution has a mass fraction ranging from 1.0% to 5.0%. In this embodiment, the mass fraction of the lime solution in the fluorination reaction solution can be 1.0%, 3.0%, 5.0%, 7.0%, 9.0%, or 10.0%, or any value ranging from 1.0% to 10.0%. The mass fraction of the calcium chloride solution can be 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, or 5.0%, or any value ranging from 1.0% to 5.0%. That is, within the above concentration ranges, the lime solution in the fluorination reaction solution can gradually increase the pH value of the wastewater, creating an alkaline environment for the combination of fluoride ions and calcium ions. This results in a relatively mild defluorination effect and helps reduce the problems of excessive precipitate or increased treatment costs caused by excessive addition. Furthermore, lime solution provides sufficient calcium and hydroxide ions to promote the formation and precipitation of calcium fluoride. By adjusting the mass fraction of the lime solution, the pH value of the wastewater and the amount of precipitate can be effectively controlled. When the mass fraction of the calcium chloride solution is within the above-mentioned range, the calcium chloride solution provides sufficient calcium ions, and in combination with the lime solution, provides even more calcium ions. This allows a sufficient amount of calcium ions to react rapidly with fluoride ions to form calcium fluoride precipitate, resulting in high defluorination efficiency and better control over defluorination effect and cost.

[0053] In this embodiment, the total calcium-to-fluoride molar ratio in the mixed solution is any value within the range of 0.8-1.0. That is, the molar ratio of calcium ions to fluoride ions in the mixed solution can be 0.8, 0.85, 0.9, 0.95, or 1.0, or any value within the range of 0.8-1.0. In other words, when the molar ratio of calcium ions to fluoride ions in the mixed solution is within the above range, it can be ensured that the amount of calcium ions in the mixed solution is always more than half the amount of fluoride ions. This ensures that calcium ions can combine with all fluoride ions in the mixed solution to form calcium fluoride, thereby improving the defluorination efficiency and quality.

[0054] In a further embodiment, the preset concentration is any value within the range of 100 mg / L to 10000 mg / L. In this embodiment, the concentration of the sodium carbonate precipitant can be 100 mg / L, 300 mg / L, 500 mg / L, 700 mg / L, 1000 mg / L, 3000 mg / L, 5000 mg / L, 7000 mg / L, or 10000 mg / L, or any value within the range of 100 mg / L to 10000 mg / L. That is to say, when the concentration of the sodium carbonate precipitant is in the range of 100 mg / L to 10000 mg / L, the carbonate ions in the sodium carbonate precipitant can completely react with the calcium ions in the primary treated water to form calcium carbonate precipitate, and under the action of calcium fluoride crystal nuclei, calcium carbonate crystals and calcium carbonate crystal nuclei are formed, thereby improving the hardness removal efficiency. In a preferred embodiment, the concentration of the sodium carbonate precipitant can be any value in the range of 1000 mg / L to 2000 mg / L, that is, the concentration of the sodium carbonate precipitant can be 1000 mg / L, 1100 mg / L, 1200 mg / L, 1400 mg / L, 1600 mg / L, 1700 mg / L, 1800 mg / L or 2000 mg / L, or any value in the range of 1000 mg / L to 2000 mg / L.

[0055] In a further embodiment, the sodium carbonate precipitant is prepared from quaternary treated water and sodium carbonate. In this embodiment, the sodium carbonate precipitant is prepared using quaternary treated water, and a reaction solution with a second upward velocity is provided to separate calcium carbonate crystals and calcium carbonate nuclei. This means that the preparation of the sodium carbonate precipitant using quaternary treated water achieves effective resource integration of the resource-based treatment process. Furthermore, the reaction solution formed by the sodium carbonate precipitant prepared with quaternary treated water and quaternary treated water supplies the high hydraulic requirements of the calcium carbonate crystallization system, effectively controlling the supersaturation of calcium carbonate crystallization and improving crystallization efficiency.

[0056] In a further embodiment, the filtration process includes ultrafiltration and reverse osmosis. In this embodiment, after defluorination, hardness removal, pH adjustment, denitrification, and decarbonization, the photovoltaic wastewater enters a three-stage sedimentation tank. The effluent after sedimentation is the tertiary treated water. The tertiary treated water is then filtered to obtain quaternary treated water to remove impurities. The filtration process includes ultrafiltration and reverse osmosis. The ultrafiltration membrane has a tiny pore size, which can effectively trap suspended solids and colloids in the water. The reverse osmosis membrane has an extremely high desalination rate, which can effectively remove dissolved salts, heavy metal ions, organic matter, and other impurities from the effluent, thereby improving the water quality of the quaternary treated water and thus improving the operational quality of the photovoltaic wastewater resource utilization treatment process.

[0057] In a further embodiment, the volume ratio of fluorite powder is any value within the range of 30%-60%. In this embodiment, the volume ratio of fluorite powder can be 30%, 35%, 40%, 45%, 50%, 55%, or 60%, or any value within the range of 30%-60%. The main component of fluorite powder is calcium fluoride seed crystals. In defluorination treatment, by using fluorite powder as seed crystals to induce calcium fluoride crystallization, the necessary nuclei are provided for calcium fluoride crystallization, accelerating the crystallization reaction and effectively removing fluoride ions from photovoltaic wastewater. When the volume ratio of fluorite powder is within the above range, the fluorite powder provides sufficient nuclei, allowing the calcium fluoride crystallization reaction to proceed rapidly, which helps to quickly reduce the concentration of fluoride ions in the water. Simultaneously, defluorination by inducing calcium fluoride crystallization may produce fewer byproducts compared to other chemical treatment methods, helping to reduce the burden on subsequent treatments. Furthermore, the use of fluorite powder as seed crystals helps to stabilize water quality parameters during the defluorination process and improve the stability of the effluent water quality.

[0058] In a further embodiment, the step of sequentially performing pH adjustment, denitrification, and decarbonization treatment on the secondary treated water to obtain tertiary treated water further includes:

[0059] Step S510: Adjust the pH using concentrated acid wastewater.

[0060] In this embodiment, the pH adjustment step for the secondary treated water utilizes concentrated acid wastewater, eliminating the need for external sulfuric acid or hydrochloric acid. This reduces the salinity of the effluent from the entire resource recovery process, effectively integrating resource utilization. Here, the concentrated acid wastewater can be acidic photovoltaic wastewater.

[0061] In a further embodiment, the pH after pH adjustment is any value within the range of 6.0-7.0. In this embodiment, the pH value of the secondary treated water after pH adjustment can be 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, or 7.0, or any value within the range of 6.0-7.0. The optimal pH range for denitrification is 6.5-7.5. Therefore, a pH value within the range of 6.0-7.0 is conducive to the growth and metabolism of denitrifying bacteria, thereby effectively promoting the denitrification reaction, helping to reduce the accumulation of ammonia nitrogen and nitrite, and avoiding adverse effects on subsequent treatment processes. Simultaneously, during the decarbonization process, the activity of microorganisms is affected by pH. A pH value within the range of 6.0-7.0 is conducive to the growth and metabolism of microorganisms, thereby accelerating the degradation process of organic matter, helping to shorten treatment time, and improving overall treatment efficiency.

[0062] The present application will be further described in detail below with reference to specific embodiments.

[0063] Example 1

[0064] The average concentration of fluoride ions in the homogeneous photovoltaic wastewater is 1000 mg / L, and the concentration of nitrate nitrogen is 200 mg / L. The photovoltaic wastewater enters a primary stirred crystallization tank, where a 10% (w / w) lime solution and a 5% (w / w) calcium chloride solution are added to form a mixed solution with a total calcium-to-fluoride molar ratio of 0.9. Fluorite powder with a particle size of 100 μm is used as seed crystals, with a volume ratio of 30%. The upward flow velocity provided by the mixed solution in the primary stirred crystallization tank is 10 m / h. Calcium fluoride crystals with particle sizes of 30μm-100μm and calcium fluoride nuclei smaller than 30μm were prepared. Primary treated water from the primary sedimentation tank, along with a sodium carbonate precipitant concentration of 2000 mg / L, was introduced into a crystallization fluidized bed. The upward flow velocity of the reaction solution in the crystallization fluidized bed was 85 m / h to prepare calcium carbonate crystals with particle sizes of 0.5mm-1.5mm and calcium carbonate nuclei smaller than 0.5mm. The purity of the obtained calcium carbonate crystals was 96%, and the moisture content of the calcium carbonate crystals after natural drying was 1%. Secondary treated water from the secondary sedimentation tank entered a pH adjustment tank to adjust the pH of the secondary treated water to 6. Then, denitrification and decarbonation treatments were performed sequentially to prepare tertiary treated water. The tertiary treated water was filtered to obtain quaternary treated water and concentrate. The concentrate underwent further defluorination and hardness removal treatments, followed by pH adjustment, denitrification, decarbonation, and filtration to obtain quaternary treated water that meets emission standards.

[0065] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A photovoltaic wastewater resource utilization treatment process, characterized in that, Includes the following steps: Photovoltaic wastewater is added to a primary stirred crystallization tank containing a fluorination reaction solution to generate a mixed solution, wherein the fluorination reaction solution includes lime solution and fluorite powder; The mixture is caused to form a first upward flow velocity, so that the mixture is separated into calcium fluoride crystals and primary treated water containing calcium fluoride crystal nuclei; The primary treated water and a sodium carbonate precipitant of a preset concentration are introduced into a crystallization fluidized bed so that the sodium carbonate precipitant reacts with calcium ions in the primary treated water to generate calcium carbonate precipitate, and calcium carbonate crystals and calcium carbonate nuclei are induced by the calcium fluoride crystal nuclei to form calcium carbonate crystals. The reaction solution formed by the sodium carbonate precipitant and the primary treated water is induced to form a second upward flow rate, so that the reaction solution is separated into calcium carbonate crystals and secondary treated water containing calcium carbonate crystal nuclei, the calcium carbonate crystal nuclei being arranged to flow into the crystallization fluidized bed; The secondary treated water is subjected to pH adjustment, denitrification, and decarbonization treatment in sequence to obtain tertiary treated water; The tertiary treated water is filtered to obtain quaternary treated water and concentrate. The concentrate undergoes further defluorination and hardness removal treatments, followed by pH adjustment, denitrification, decarbonization, and filtration to obtain the quaternary treated water. The calcium fluoride crystals have a particle size of any value between 30 μm and 100 μm, the calcium fluoride crystal nuclei have a particle size of less than 30 μm, the calcium carbonate crystals have a particle size of any value between 0.2 mm and 2.0 mm, and the calcium carbonate crystal nuclei have a particle size of less than 0.2 mm. The first upward flow velocity is any value in the range of 2 m / h to 15 m / h, and the second upward flow velocity is any value in the range of 50 m / h to 120 m / h.

2. The processing technology according to claim 1, characterized in that, The fluorination reaction solution also includes: A calcium chloride solution is used to react with fluoride ions in the photovoltaic wastewater to generate calcium fluoride.

3. The processing technology according to claim 2, characterized in that, The mass fraction of the lime solution in the fluorination reaction solution is in the range of 1.0% to 10.0%, and the mass fraction of the calcium chloride solution is in the range of 1.0% to 5.0%.

4. The processing technology according to claim 3, characterized in that, The preset concentration is any value within the range of 100 mg / L to 10000 mg / L.

5. The processing technology according to claim 4, characterized in that, The sodium carbonate precipitant is prepared from the fourth-stage treated water and sodium carbonate.

6. The processing method according to any one of claims 1-5, characterized in that, The filtration process includes ultrafiltration and reverse osmosis.

7. The processing technology according to claim 6, characterized in that, The step of sequentially performing pH adjustment, denitrification, and decarbonization treatment on the secondary treated water to obtain tertiary treated water further includes: The pH adjustment was performed using concentrated acidic wastewater.

8. The processing technology according to claim 7, characterized in that, The pH value after pH adjustment is any value in the range of 6.0-7.0.

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