Method for efficiently removing algae through ultraviolet coupling sodium percarbonate advanced oxidation technology

Abstract

The invention provides a method for efficiently removing algae through an ultraviolet coupling sodium percarbonate advanced oxidation technology, and belongs to the technical field of algae removal. The method for efficiently removing algae through the ultraviolet coupling sodium percarbonate advanced oxidation technology comprises the steps that microcystis aeruginosa is cultured, experimental algae-containing water is prepared, a proper amount of the algae-containing water obtained in S2 is taken and transferred into a reaction device, and the algae-containing water is added into the reaction device; under the conditions of ultraviolet light emitted by a mercury lamp with the power of 10w, SPC dosage of 6mmol / L and pH of 7.0, the algae removal effects of three oxidation technologies of independent ultraviolet light degradation, independent SPC oxidation and ultraviolet coupling SPC are compared, and the influence of UV / SPC on the algae removal effects under different conditions is explored through experiments; the invention provides a method for efficiently removing algae by an ultraviolet coupling sodium percarbonate advanced oxidation technology, which is used for solving the technical problem that in the prior art, an ultraviolet / chlorine advanced oxidation technology may generate harmful byproducts through a UV / SPC (Ultraviolet / Sodium Percarbonate) process.

Description

Technical Field

[0001] This invention belongs to the field of algae removal technology, specifically, it relates to a method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology. Background Technology

[0002] Among water pollution issues, eutrophication of inland lakes and reservoirs is one of the most pressing environmental problems for many countries and governments, and it has become a global challenge. Eutrophication refers to water pollution caused by excessive levels of nutrients such as nitrogen and phosphorus in water bodies. Eutrophication leads to cyanobacterial blooms, severely damaging aquatic ecosystems, reducing water body functions, and causing mass deaths of fish and other aquatic organisms. The algal toxins and algal-derived odor substances produced by cyanobacterial blooms also directly affect drinking water safety, ultimately impacting human health and safety.

[0003] Microcystis aeruginosa is a specific type of cyanobacteria. Microcystis aeruginosa cells are negatively charged in normal water and have a high zeta potential, making them difficult for coagulants to adsorb and aggregate. Microcystis aeruginosa cells are tiny, and the flocs they form in the water are also small and have a slow settling speed. During its growth, Microcystis aeruginosa secretes a large amount of extracellular organic matter. During the coagulation process, this organic matter reacts with the hydrolysis products of the coagulant to form complexes, affecting the coagulation effect and making it difficult to remove in the traditional coagulation-filtration process in water plants.

[0004] In recent years, advanced ultraviolet (UV) oxidation technology has emerged as a highly efficient new technology for removing recalcitrant pollutants, demonstrating significant advantages in the removal of Microcystis aeruginosa. On one hand, UV advanced oxidation technology typically generates highly oxidizing free radicals, such as hydroxyl radicals, which rapidly attack the cell structure of Microcystis aeruginosa, damaging its cell wall and cell membrane, leading to leakage of cell contents and ultimately causing algal death. On the other hand, advanced oxidation technology generally features rapid reaction speed and high removal efficiency. Compared to traditional algae removal methods, it can achieve large-scale removal of Microcystis aeruginosa in a shorter time, effectively addressing emergencies such as algal blooms. Simultaneously, this technology has a relatively small environmental impact, producing no secondary pollution or easily controllable secondary pollution. Furthermore, UV advanced oxidation technology possesses adaptability and flexibility, allowing for the selection of appropriate oxidants and UV light intensity based on different water conditions and algae removal requirements, achieving targeted removal of Microcystis aeruginosa.

[0005] The master's thesis from Huazhong University of Science and Technology, titled "Study on Algae Removal Using Ultraviolet / Chlorine Advanced Oxidation Technology and Its Impact on the Formation of Chlorinated Byproducts," demonstrates that ultraviolet / chlorine advanced oxidation technology can optimize the combination of the advantages of ultraviolet light and chlorination alone to achieve algae removal and control. However, existing technologies have the disadvantage of generating disinfection byproducts.

[0006] ① Reason: During chlorine disinfection, chlorine reacts chemically with organic matter in the water to produce disinfection byproducts such as trihalomethanes and haloacetic acids. These substances have potential carcinogenic, teratogenic, and mutagenic risks, which can harm human health and the ecological environment.

[0007] ②Results: In the UV-chlorination combined technology, although UV light itself does not produce disinfection byproducts, if chlorine disinfection is used, these harmful byproducts may still be generated, increasing the safety risks to water quality and the pollution to the environment. It is necessary to monitor and control disinfection byproducts, which increases the treatment requirements and costs. Summary of the Invention

[0008] Therefore, the purpose of this invention is to provide a method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology, which solves the technical problem that ultraviolet / chlorine advanced oxidation technology may produce harmful byproducts in the prior art, and can efficiently remove Microcystis aeruginosa without the risk of secondary pollution.

[0009] This invention is implemented as follows:

[0010] This invention provides a method for efficient algae removal using ultraviolet light coupled with sodium percarbonate advanced oxidation technology, comprising the following steps:

[0011] S1: Cultivation of Microcystis aeruginosa;

[0012] S2: Prepare the algae-containing water for the experiment;

[0013] S3: Take an appropriate amount of the algae-containing water obtained in S2 and transfer it into the reaction device. Control the experimental temperature of the reaction device to 25℃ and the reaction time to 60min through the reaction circulation device. Immediately after the reaction is completed, take a sample and add 200μL Na2S2O3 to quench the unreacted active substances.

[0014] S4: Under the conditions of ultraviolet light emitted by a 10W mercury lamp, SPC dosage of 6mmol / L, and pH of 7.0, the algae removal efficiency of three oxidation technologies—ultraviolet light oxidation alone, SPC oxidation alone, and ultraviolet-coupled SPC oxidation—was compared.

[0015] S5: MeOH and TBA are added to the UV / SPC process, respectively, and react with ·OH and CO3· - The reaction was investigated to determine the effect of free radicals on algae removal efficiency;

[0016] S6: Investigate the influencing factors on algae removal in the UV / SPC advanced oxidation system under five different conditions.

[0017] Based on the above technical solution, the method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology of the present invention can be further improved as follows:

[0018] Furthermore, the culture conditions described in S1 are as follows: Microcystis aeruginosa is cultured in BG11 medium with a light-dark ratio of 12h:12h, a light intensity of 2500 lx, a temperature of 25±1℃, and is shaken once a day.

[0019] Furthermore, S2 includes the following steps:

[0020] S21: Take an appropriate amount of Microcystis aeruginosa cells grown to the logarithmic growth phase and place them in a centrifuge tube. Centrifuge at 6000 r / min for 10 min, discard the supernatant, centrifuge again to remove the supernatant, and dilute the algal cells to 1×10⁻⁶ with 500 ml of ultrapure water. 6 / ml;

[0021] S22: The pH of the algal solution obtained in S21 was adjusted to 7.0 using 0.2 mol / L NaOH and 0.2 mol / L phosphoric acid, which is the algal-containing water used in the experiment.

[0022] Furthermore, the first case of S6 is: the effect of SPC dosage on algae removal effect;

[0023] Under the conditions of ultraviolet light emitted by a 10W mercury lamp and pH 7.0, the effect of SPC dosage range of 1–10 mmol / L on the algae removal efficiency of the UV / SPC oxidation system was compared.

[0024] Furthermore, the second scenario of S6 is: the effect of algae density on algae removal efficiency;

[0025] Under the conditions of SPC dosage of 6 mmol / L, ultraviolet light emitted by a 10W mercury lamp, and pH 7.0, the control algal density concentration range was 5 × 10⁻⁶. 5 / ml to 1×10 7 The effect of / ml on the algae removal efficiency of the UV / SPC oxidation system.

[0026] Furthermore, the third case of S6 is: the effect of pH on algae removal effect;

[0027] The effect of SPC dosage of 6 mmol / L on algae removal efficiency of UV / SPC oxidation system under ultraviolet light emitted by a 10W mercury lamp was compared with that of pH value range 5 to 11.

[0028] Furthermore, the fourth case of S6 is: the effect of inorganic ions on algae removal effect;

[0029] Under ultraviolet light emitted by a 10W mercury lamp, with an SPC dosage of 6 mmol / L and a pH of 7.0, Cl - Within the range of 0–10 mmol / L, HCO3 -The effect of 0–10 mmol / L on algae removal efficiency in UV / SPC oxidation systems.

[0030] Furthermore, the fifth case of S6 is: the effect of natural organic matter on algae removal effect;

[0031] The effects of HA concentrations of 0, 0.5, 1, 3 and 5 mg / L on algae removal in a UV / SPC oxidation system under the conditions of ultraviolet light emitted by a 10W mercury lamp, SPC dosage of 6 mmol / L, and pH of 7.0.

[0032] Furthermore, the reaction apparatus described in S3 includes:

[0033] A magnetic stirrer, on which a quartz column reaction vessel is placed, and an ultraviolet lamp quartz sleeve is provided inside the reaction vessel. The quartz column reaction vessel and the quartz sleeve form a cavity, which is filled with a reaction solution.

[0034] The magnetic stirrer has a water inlet at the lower end of its circumferential surface that communicates with the interior, and a water outlet at the upper end of its circumferential surface that communicates with the interior.

[0035] The reaction vessel is provided with a sampling port at the top, and the bottom wall of the magnetic stirrer is provided with a rotor that rotates with the magnetic stirrer to agitate the reaction solution.

[0036] Furthermore, the UV lamp should be turned on and preheated for at least 30 minutes before each experiment.

[0037] Compared with existing technologies, the beneficial effects of the method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology provided by this invention are:

[0038] I. Comparison with UV / Cl technology

[0039] (1) Types of free radicals and their oxidizing power

[0040] ①UV / SPC: Generates hydroxyl radicals (·OH, oxidation potential 2.8V) and carbonate radicals (CO3· - (1.5V), forming a complex free radical network of "strong oxidizing + long lifetime". Among them, CO3· - High stability under neutral and alkaline conditions (lifespan 10). -4 -10 -3 s), which can compensate for the short lifespan of ·OH (10 -9 To address the shortcomings of s), and adapt to the transport needs of free radicals in complex water bodies.

[0041] ②UV / Cl: Primarily relies on ·OH and chlorine radicals (Cl·, 2.4V), but Cl· readily combines with chloride ions (Cl-) in water to form chlorine radical complexes (Cl2·). - Cl· reduces the efficiency of free radical utilization; and Cl· oxidation is more selective, with a lower degradation efficiency for certain inert organic matter (such as cellulose) in algal cells than ·OH.

[0042] (2) By-product risk

[0043] ①UV / SPC: The decomposition product of sodium percarbonate is Na + CO3 2- / HCO3 - It leaves no toxic residue; CO3·- reacts with organic matter to ultimately produce CO2 and H2O, without secondary pollution.

[0044] ②UV / Cl: Chlorine reacts with natural organic matter (NOM) in water to easily generate disinfection byproducts (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). Among them, chloroform has been listed as a carcinogen. When algae contain a lot of protein, Cl- may also react with amines to generate nitrosamines, which are strong carcinogens.

[0045] II. Comparison with traditional algae removal methods

[0046] (1) Traditional chemical agents (such as copper sulfate, bleaching powder)

[0047] Dependence on heavy metal toxicity (e.g., Cu) 2+ ) or strong oxidizing agents (such as ClO) - It damages algal cells but cannot completely mineralize organic matter; the algal toxins released after the algae die can easily lead to secondary pollution; and Cu 2+ Accumulation in water can disrupt the food chain (such as inhibiting zooplankton reproduction), and long-term use may lead to algal resistance.

[0048] (2) Biological / physical methods (such as algae release, mechanical harvesting)

[0049] Biological methods are greatly affected by temperature and pH (e.g., algae and bacteria have reduced activity at low temperatures) and have limited inhibitory effects on dominant algal species such as cyanobacteria; physical methods are energy-intensive (e.g., air flotation requires continuous aeration), are only suitable for small-scale water bodies, and cannot cope with sudden algal blooms.

[0050] III. Innovative Combination of Core Technology Solutions

[0051] UV-sodium percarbonate coupling system

[0052] A "UV / SPC advanced oxidation technology" was constructed by combining ultraviolet (UV) light with sodium percarbonate (SPC). SPC dissolves in water, releasing hydrogen peroxide (H₂O₂) and sodium carbonate (Na₂CO₃). Under UV irradiation, H₂O₂ is activated to generate hydroxyl radicals (·OH) and carbonate radicals (CO₃·OH). - This forms a strong oxidizing complex system.

[0053] IV. Breakthrough Design of Mechanism of Action

[0054] (1) Synergistic effect of two free radicals

[0055] •OH (oxidation potential 2.8V) has extremely strong oxidizing properties and rapidly destroys algal cell structure; CO3· - (Oxidation potential 1.5V) High stability under neutral conditions (lifetime 10) -4 -10 -3 s), to compensate for the short lifetime of ·OH (10 -9 To overcome the deficiencies of s), a complex free radical network of "strong oxidation + long lifespan" is formed, achieving efficient degradation of Microcystis aeruginosa.

[0056] (2) Synergistic effect enhances algae removal efficiency

[0057] UV or SPC alone has limited algae removal efficiency (40% and nearly 0%, respectively), but the UV / SPC process achieves an algae removal rate of 88.64%, demonstrating that the synergistic effect of UV and SPC significantly improves free radical production and algal cell destruction ability.

[0058] V. Improvements to address the shortcomings of existing technologies

[0059] (1) Solving the problem of disinfection byproducts

[0060] Compared to UV / Cl technology, the decomposition product of SPC is Na. + CO3 2- / HCO3 - It leaves no toxic residues and avoids the reaction of chlorine with organic matter to produce carcinogenic byproducts such as trihalomethanes (THMs) and haloacetic acids (HAAs), thus achieving "zero secondary pollution".

[0061] (2) Enhance the broad-spectrum and long-lasting oxidation properties

[0062] ① Overcoming the tendency of chlorine free radicals (Cl·) in UV / Cl to react with Cl - In light of the issue of reduced efficiency, CO3· - It exhibits stronger transport properties in complex water bodies and is more effective at degrading inert organic matter (such as cellulose) within algal cells.

[0063] ② It avoids the heavy metal accumulation toxicity of traditional chemical agents (such as copper sulfate) and the environmental limitations of biological methods, and is suitable for large-scale algae removal in water bodies.

[0064] VI. Integration of Advantages in Practical Applications

[0065] (1) High efficiency and adaptability

[0066] Targeting the negative charge and poor coagulation properties of Microcystis aeruginosa, UV / SPC directly attacks the cell structure with free radicals, breaking through the removal bottleneck of traditional coagulation processes and achieving a removal rate of 88.64% within 180 minutes. It is suitable for emergency treatment of sudden algal blooms.

[0067] (2) Environmental friendliness and sustainability

[0068] The reaction products are CO2 and H2O, with no chemical residues and no disruption to the ecological balance of the water body. Compared with biological / physical methods (such as mechanical dredging and algae / bacteria release), it is not limited by temperature / pH, has lower energy consumption, and can be applied on a large scale to the treatment of eutrophic water bodies such as lakes and reservoirs. Attached Figure Description

[0069] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0070] Figure 1 This is a schematic diagram of the reaction apparatus;

[0071] Figure 2 The degradation effects of three processes on Microcystis aeruginosa;

[0072] Figure 3 The effect of two quenching agents on algae removal efficiency;

[0073] Figure 4 The effect of sodium percarbonate dosage on algae removal efficiency;

[0074] Figure 5 The effect of algae density on algae removal efficiency;

[0075] Figure 6 The effect of pH on algae removal efficiency;

[0076] Figure 7 For Cl - and HCO3 - Impact on algae removal efficiency;

[0077] Figure 8The impact of natural organic matter on algae removal effectiveness;

[0078] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0079] 1. Sampling port; 2. Water outlet; 3. Reaction solution; 4. Rotor; 5. Water inlet; 6. Magnetic stirrer. Detailed Implementation

[0080] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0081] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0082] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0083] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0084] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0085] Example 1

[0086] like Figure 1-8 As shown, this invention provides a method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology, comprising the following steps:

[0087] S1: Cultivation of Microcystis aeruginosa;

[0088] S2: Prepare the algae-containing water for the experiment;

[0089] S3: Take an appropriate amount of the algae-containing water obtained in S2 and transfer it into the reaction device. Control the experimental temperature of the reaction device to 25℃ and the reaction time to 60min through the reaction circulation device. Take a sample immediately after the reaction is completed and add 200μL of Na2S2O3. The amount added here is determined by calculation to quench the unreacted active substances.

[0090] Among them, active substances refer to hydroxyl radicals (·OH) and carbonate radicals (CO3· - );

[0091] S4: Under the conditions of ultraviolet light emitted by a 10W mercury lamp, SPC dosage of 6mmol / L, and pH of 7.0 (the same below), the algae removal efficiency of three oxidation technologies—ultraviolet light oxidation alone, SPC oxidation alone, and ultraviolet-coupled SPC oxidation—was compared.

[0092] Among them, such as Figure 2 The algae removal efficiencies of three processes—ultraviolet (UV) alone, sodium percarbonate (SPC) alone, and UV / SPC—were compared over 180 minutes. At an SPC dosage of 6 mmol / L, the UV / SPC algae removal efficiency was significantly higher than that of UV alone and SPC alone. With SPC alone, the algal cell removal rate was almost zero, indicating that SPC alone cannot directly oxidize algal cells, consistent with previous studies. In contrast, UV alone had a certain destructive effect on Microcystis aeruginosa, with a removal rate of 40% after 180 minutes, which is consistent with the conclusion that UV radiation alone is unlikely to induce large-scale algal cell lysis.

[0093] Among the three processes, the UV / SPC process achieved the highest removal rate (88.64%). Since both UV and SPC alone had limited removal effects on Microcystis aeruginosa, and research indicates that UV-activated sodium percarbonate (SPC) can generate hydroxyl radicals (·OH) and carbonate radicals (CO3··OH). - These free radicals can effectively remove Microcystis aeruginosa, suggesting that the UV / SPC process is mainly a reaction of free radicals.

[0094] S5: MeOH and TBA are added to the UV / SPC process, respectively, and react with ·OH and CO3· -The reaction was investigated to determine the effect of free radicals on algae removal efficiency;

[0095] Among them, such as Figure 3 To determine the types of free radicals generated during algae removal in the UV / SPC process, MeOH and TBA were added to the UV / SPC process, respectively, and their effects on algae removal efficiency were observed. The reaction rate of TBA with ·OH was k. ·OH，TBA = (3.8~7.6)×10 8 m -1 ·s -1 And CO3· - TBA barely reacts ( <1.6×10 2 m -1 ·s -1 MeOH can react with CO3· - ( =2.2×10 7 m -1 ·s -1 ) and ·OH(k ·OH，MeOH =6.0×10 8 m -1 ·s -1 Rapid response

[0096] Both MeOH and TBA significantly inhibited the removal of algae in the UV / SPC system, but MeOH showed a stronger inhibitory effect at the same concentration. When the system contained excess MeOH and TBA (molar ratio of MeOH to SPC was 10:1), the removal rate of Microcystis aeruginosa decreased from 88.64% to 37.21% and 49.59%, respectively. This indicates that the removal of MeOH and TBA by MeOH and TBA by TBA was significantly reduced by MeOH and TBA by TBA. - It participated in the degradation process of Microcystis aeruginosa. Furthermore, the synergistic effect between ultraviolet radiation and sodium percarbonate was mainly due to ·OH rather than CO3· - ·OH, as a strong oxidizing agent, has been proven to effectively inactivate algae and a variety of microorganisms.

[0097] S6: Investigate the influencing factors on algae removal in the UV / SPC advanced oxidation system under five different conditions.

[0098] Optionally, in the above technical solution, the culture conditions in S1 are as follows: Microcystis aeruginosa is cultured in BG11 medium with a light-dark ratio of 12h:12h, a light intensity of 2500lx, a temperature of 25±1℃, and the medium is shaken once a day.

[0099] Optionally, in the above technical solution, S2 includes the following steps:

[0100] S21: Take an appropriate amount of Microcystis aeruginosa cells grown to the logarithmic growth phase and place them in a centrifuge tube. Centrifuge at 6000 r / min for 10 min, discard the supernatant, centrifuge again to remove the supernatant, and dilute the algal cells to 1×10⁻⁶ with 500 ml of ultrapure water. 6 / ml;

[0101] S22: The pH of the algal solution obtained in S21 was adjusted to 7.0 using 0.2 mol / L NaOH and 0.2 mol / L phosphoric acid, which is the algal-containing water used in the experiment.

[0102] Optionally, in the above technical solution, the first case of S6 is: the effect of SPC dosage on algae removal effect;

[0103] Under the conditions of ultraviolet light emitted by a 10W mercury lamp and pH 7.0, the effect of SPC dosage range of 1–10 mmol / L on the algae removal efficiency of the UV / SPC oxidation system was compared.

[0104] Optionally, in the above technical solution, the second case of S6 is: the effect of algae density on algae removal effect;

[0105] Under the conditions of SPC dosage of 6 mmol / L, ultraviolet light emitted by a 10W mercury lamp, and pH 7.0, the control algal density concentration range was 5 × 10⁻⁶. 5 / ml to 1×10 7 The effect of / ml on the algae removal efficiency of the UV / SPC oxidation system.

[0106] Optionally, in the above technical solution, the third case of S6 is: the effect of pH on algae removal effect;

[0107] The effect of SPC dosage of 6 mmol / L on algae removal efficiency of UV / SPC oxidation system under ultraviolet light emitted by a 10W mercury lamp was compared with that of pH value range 5 to 11.

[0108] Optionally, in the above technical solution, the fourth case of S6 is: the effect of inorganic ions on algae removal effect;

[0109] Under ultraviolet light emitted by a 10W mercury lamp, with an SPC dosage of 6 mmol / L and a pH of 7.0, Cl - Within the range of 0–10 mmol / L, HCO3 - The effect of 0–10 mmol / L on algae removal efficiency in UV / SPC oxidation systems.

[0110] Optionally, in the above technical solution, the fifth case of S6 is: the influence of natural organic matter on the algae removal effect;

[0111] The effects of HA concentrations of 0, 0.5, 1, 3 and 5 mg / L on algae removal in a UV / SPC oxidation system under the conditions of ultraviolet light emitted by a 10W mercury lamp, SPC dosage of 6 mmol / L, and pH of 7.0.

[0112] Optionally, in the above technical solution, the reaction apparatus for S3 includes:

[0113] A magnetic stirrer 6 is placed on the magnetic stirrer 6. A quartz column reaction vessel is provided inside the reaction vessel. A quartz sleeve with an ultraviolet lamp is provided inside the reaction vessel. The quartz column reaction vessel and the quartz sleeve form a cavity, which is filled with reaction solution 3.

[0114] The magnetic stirrer 6 has a water inlet 5 at the lower end of its circumferential surface that communicates with the interior, and a water outlet 2 at the upper end of its circumferential surface that communicates with the interior.

[0115] The top of the reaction vessel is provided with a sampling port 1, and the bottom wall of the magnetic stirrer 6 is provided with a rotor 4 that rotates with the magnetic stirrer 6 to agitate the reaction solution 3.

[0116] The inlet 5 and outlet 2 of the reaction device are both connected to a constant temperature water circulation device.

[0117] Optionally, in the above technical solution, the ultraviolet lamp should be turned on and preheated for at least 30 minutes before each experiment.

[0118] The experimental materials included: Microcystis aeruginosa purchased from the Institute of Hydrobiology, Chinese Academy of Sciences, serial number: HB905; centrifuge model: Flying Pigeon brand, TGL-15B; sodium percarbonate (SPC) purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; other chemical reagents were from China National Pharmaceutical Group Chemical Reagent Co., Ltd.; and the ultrapure water (18.2 MΩ·cm) used in the experiment was prepared using the Millipore ultrapure water system.

[0119] During the experiment, in order to ensure stable UV light source output, the UV lamp needs to be preheated for 30 minutes before the experiment begins; the experimental temperature is controlled by a constant temperature water circulation system and is 25℃.

[0120] To investigate the effects of operating parameters on the removal of Microcystis aeruginosa, the initial concentrations of SPC and Microcystis aeruginosa were set at 1–10 mmol / L and 5 × 10⁻⁶ mmol / L, respectively. 5 / ml~1×10 7 The pH was varied within the range of / ml; the pH of the solution was adjusted to 7.0 using 0.2mol / L NaOH and 0.2mol / L phosphoric acid.

[0121] In investigating the effect of pH on Microcystis aeruginosa, the pH was maintained during the reaction process using a 4 mmol / L phosphate buffer (PB) solution.

[0122] In investigating the effects of aquatic matrix on the removal of Microcystis aeruginosa, natural organic matter and Cl- were considered. - 、HCO3 - The concentration ranges were 0–5 mg / L, 0–30 mmol / L, and 0–10 mmol / L, respectively.

[0123] All experiments were repeated at least three times.

[0124] The concentration of *Microcystis aeruginosa* was determined spectrophotometrically. The density of *Microcystis aeruginosa* was positively correlated with the absorbance of the algal cell solution at 680 nm; therefore, the removal rate of *Microcystis aeruginosa* cells was calculated using the OD680 absorbance before and after the reaction. The UV radiation intensity and effective depth were determined using the iodide / potassium iodate spectrophotometric method. The pH value was measured using a FE28 Mettler Toledo pH meter.

[0125] Furthermore, the specific influencing factors of UV / SPC oxidation algae removal in step S6 are as follows:

[0126] I. The effect of SPC dosage on algae removal efficiency

[0127] The amount of sodium percarbonate added directly affects the free radicals, namely ·OH and CO3·, in the UV / SPC process. - The amount of algae generated. Therefore, within the SPC dosage range of 1–10 mmol / L, the effect of dosage on algae removal efficiency was investigated, and the experimental results are as follows: Figure 4 As shown.

[0128] It can be seen that as the SPC dosage increased from 1 to 10 mmol / L, the removal efficiency of the UV / SPC process for Microcystis aeruginosa gradually increased, with the removal rate of algal cells rising from 59.54% to 90.37% after 180 min. Increasing the dosage of sodium percarbonate can generate more active free radicals, continuously increasing oxidative stress, completely inhibiting the algal cell repair mechanism, and ultimately leading to algal cell death.

[0129] Studies have shown that excess H₂O₂ can react with ·OH to generate HO₂·, which has even lower activity. The oxidizing power of HO₂· (redox potential approximately 1.4V) is much lower than that of ·OH (2.8V), leading to a decrease in the effective free radical concentration and a decline in the efficiency of algal cell removal. This phenomenon was also observed in our experiment; the removal rate hardly increased when the sodium percarbonate (SPC) dosage increased from 6 mmol / L to 10 mmol / L. Therefore, as the initial SPC concentration continues to increase, the rate of increase in algal cell degradation decreases with increasing initial SPC concentration; that is, the rate of increase in algal cell degradation slows down or even decreases.

[0130] II. The Influence of Algae Density on Algae Removal Efficiency

[0131] This experiment investigated the effect of different algae concentrations on the algae removal efficiency of the UV / SPC oxidation system at an SPC dosage of 6 mmol / L. The results are as follows: Figure 5 As shown.

[0132] As the initial concentration of Microcystis aeruginosa increased from 5 × 10⁻⁶, 5 / ml increased to 1×10 7 At a concentration of / ml, the removal rate of *Microcystis aeruginosa* decreased from 92.86% to 62.75% after 180 min. Under the same sodium percarbonate dosage, the concentration of active free radicals generated by the UV / SPC oxidation system is limited. When the initial concentration of *Microcystis aeruginosa* is low, these free radicals can relatively fully contact the algal cells and exert an oxidizing effect, thus effectively removing algae. However, as the algal concentration increases, the active free radicals need to react with more algal cells simultaneously, leading to a decrease in the average amount of active substances that each algal cell can contact, resulting in a decline in algal removal efficiency. On the other hand, as turbidity decreases, UV light penetrates the reaction solution more easily, resulting in higher activation efficiency of SPC and thus faster generation of active free radicals to oxidize and remove algae.

[0133] III. The Effect of pH on Algae Removal Efficiency

[0134] The pH of natural water bodies (lakes, reservoirs, etc.) is typically in the neutral to slightly alkaline range. Studying the effects of pH can provide adaptive strategies for practical engineering. Furthermore, pH can influence the generation, transformation, and reaction pathways of free radicals in the UV / SPC advanced oxidation system, thus affecting the algae removal efficiency of UV / SPC advanced oxidation technology. This experiment investigated the effect of different pH values ​​on the algae removal efficiency of the UV / SPC oxidation system at an SPC dosage of 6 mmol / L. The results are as follows: Figure 6 As shown.

[0135] As the initial pH increased from 5 to 11, the removal efficiency of the UV / SPC process for *Microcystis aeruginosa* decreased, with the removal rate dropping from 91.34% to 74.22%. The influence of solution pH on the degradation of *Microcystis aeruginosa* is as follows: First, the oxidizing power of ·OH decreases with increasing pH; under acidic conditions, the oxidizing power of ·OH is higher than under alkaline conditions. On the other hand, under alkaline pH conditions, the self-recombination of ·OH produces H₂O₂, and ·OH is then converted by OH⁻. - Both are rapidly consumed, and both reduce the ·OH concentration to slow the reaction rate. Furthermore, the dissociation of H₂O₂ (pKa = 11.6) will occur at pH = 11.0, producing hydroperoxide anions (HO₂). - This will remove ·OH and capture H2O2. Therefore, the effect of solution pH on the degradation rate of pollutants in the UV / SPC system is mainly due to the decrease in the oxidizing capacity of ·OH.

[0136] IV. The Influence of Inorganic Ions on Algae Removal Efficiency

[0137] Chloride ions (Cl) - ) and bicarbonate ions (HCO3) 3- Cl- and α-ions are two common anions found in natural water bodies, and both of these ions affect the generation and transformation of free radicals in the UV / SPC oxidation system. Therefore, it is necessary to explore the role of Cl- in this process. - and HCO3 - The effect of different Cl- concentrations on algae removal efficiency. This experiment selected different Cl- concentrations... - Concentration (0–30 mmol / L) and HCO3 - The effect of (0–10 mmol / L) on the degradation of pollutants in the UV / SPC system is as follows: Figure 7 As shown.

[0138] Cl - Within the range of 0–10 mmol / L, it has almost no effect on the algae removal effect in the UV / SPC oxidation system, except for Cl. - At a concentration of 30 mmol / L, it exhibited a small inhibitory effect, with the removal rate decreasing slightly by 7.10%. In studying the degradation of Microcystis aeruginosa by the UV / PS system, Cl... - The impact is negligible, only Cl - A smaller inhibitory effect is only observed at higher concentrations. Because Cl... - The reaction with ·OH and Cl· is reversible, therefore adding Cl... - Afterwards, the steady-state concentrations of ·OH and Cl· do not change significantly. Furthermore, with the increase of Cl... - With increasing concentration, ·OH and Cl in the UV / SPC system - The reaction is enhanced, which reduces the steady-state concentration of ·OH, but Cl· also participates in the degradation of Microcystis aeruginosa, thus making up for the consumption of ·OH.

[0139] HCO3 - It has a slight inhibitory effect on algae removal in the UV / SPC oxidation system within the range of 0–10 mmol / L, when HCO3 - When the concentration increased from 0 to 10 mmol / L, the removal rate of *Microcystis aeruginosa* decreased from 88.64% to 76.98% after 180 min of reaction. ·OH is a key free radical in the UV / SPC oxidation system, while HCO3- - It is a typical ·OH scavenger; the two react to produce CO3· - CO3· - The oxidation capacity of α-hydroxyl (oxidation potential of approximately 1.78V) is much weaker than that of ·OH (oxidation potential of approximately 2.80V), resulting in a decrease in the removal efficiency of the UV / SPC advanced oxidation system for Microcystis aeruginosa.

[0140] V. The Influence of Natural Organic Matter on Algae Removal Efficacy

[0141] Natural organic matter (NOM) exists in various water bodies and has a complex composition, mainly consisting of carbohydrates, lipids, proteins, and humic substances. Humic acid (HA) accounts for up to 90% of the dissolved organic matter in natural water bodies. Therefore, this study used HA as a representative of natural organic matter components to investigate the effects of different HA concentrations (0, 0.5, 1, 3, and 5 mg / L) on the removal of Microcystis aeruginosa by a UV / SPC system. The results are as follows: Figure 8 As shown.

[0142] from Figure 8 It was found that HA had a slight inhibitory effect on the removal of Microcystis aeruginosa by UV / SPC. When the concentration of HA increased from 0 mg / L to 5 mg / L, the removal rate of Microcystis aeruginosa decreased from 88.64% to 78.12% after a reaction time of 180 min. The effects of NOM on the UV / SPC system included the following two aspects: firstly, NOM can react with ·OH and CO3· - A reaction occurs, and as the HA concentration increases, the competitive effect between HA and Microcystis aeruginosa intensifies, leading to a decrease in its removal rate. Secondly, NOM contains unsaturated functional groups, which have a strong absorption capacity for ultraviolet light, thus causing the ·OH and CO3· in the UV / SPC system to react. - The decrease in concentration further inhibited the degradation of Microcystis aeruginosa. In this experiment, the inhibitory effect of HA on algae removal efficiency was not significant, possibly due to the high concentration of added SPC (6 mmol / L), which generated ·OH and CO3· - The concentration of HA is relatively high. When the concentration of HA is low, free radicals can quickly degrade it, resulting in a lower impact on the algae removal efficiency of UV / SPC.

[0143] Explanation of relevant terms:

[0144] ①UV: UV is an abbreviation for "Ultraviolet," meaning ultraviolet light. In advanced oxidation technologies, UV usually refers to the use of ultraviolet light to excite or activate certain oxidants, thereby generating highly oxidizing free radicals, which are used to degrade pollutants in water or inactivate microorganisms. UV light sources can be low-pressure mercury lamps, medium-pressure mercury lamps, or other types of ultraviolet lamps, with wavelengths typically ranging from 200 to 400 nm.

[0145] ②SPC: SPC is an abbreviation for "Sodium Percarbonate," meaning sodium percarbonate. Sodium percarbonate is a solid peroxide, also known as "solid hydrogen peroxide." When dissolved in water, it decomposes to release hydrogen peroxide (H₂O₂) and sodium carbonate (Na₂CO₃).

[0146] ③UV / SPC: UV / SPC is an advanced oxidation technology, short for Ultraviolet / Sodium Percarbonate. In this technology, sodium percarbonate (SPC) dissolves in water and decomposes to release hydrogen peroxide (H2O2) and sodium carbonate (Na2CO3). When irradiated with ultraviolet (UV) light, the H2O2 in SPC is activated, producing hydroxyl radicals (·OH) and carbonate radicals (CO3· · OH). - These free radicals, such as α, β, and γ, are highly oxidizing free radicals. These free radicals have extremely high redox potentials, effectively degrading organic pollutants and inactivating microorganisms in water, thus achieving efficient and safe water purification.

[0147] ④Na2S2O3: Sodium thiosulfate

[0148] ⑤OD 680 : Absorbance at 680nm using a spectrophotometer

[0149] ⑥·OH: The hydroxyl radical (·OH) is an important reactive oxygen species. From its molecular formula, it is composed of hydroxide ions (·OH). ˉ It is formed by losing an electron. Hydroxyl radicals have a very strong ability to gain electrons, that is, an oxidizing ability, with an oxidation potential of 2.8V.

[0150] ⑦CO3· - Carbonate radical: A type of free radical with weak oxidizing power and an oxidation potential of 1.5V.

[0151] ⑧Cl: Available chlorine (all values ​​mentioned in this article refer to sodium hypochlorite)

[0152] in conclusion:

[0153] ① SPC alone cannot directly oxidize Microcystis aeruginosa. Although UV alone can damage algal cells, its removal effect is very limited. However, the UV / SPC oxidation system can efficiently remove 88.64% of algal cells.

[0154] ②Through free radical inhibition experiments with MeOH and TBA, it was demonstrated that ·OH and CO3· - It participated in the degradation process of Microcystis aeruginosa. Furthermore, the synergistic effect between ultraviolet radiation and sodium percarbonate was mainly due to ·OH rather than CO3·. - .

[0155] ③The UV / SPC system improves with increasing SPC dosage;

[0156] As the pH increased from 5 to 11, the removal rate of algal cells gradually decreased.

[0157] As the algae concentration increases, the removal rate of algae cells gradually decreases.

[0158] low concentration of Cl - It has little impact on the algae removal efficiency of the UV / SPC oxidation system.

[0159] HCO3 - It has a slight inhibitory effect on the removal efficiency of algal cells, and the inhibitory effect decreases with increasing HCO3 content. - The effect increases with increasing concentration;

[0160] Low concentrations of HA have little effect on the removal of algal cells.

[0161] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology, characterized in that, Includes the following steps: S1: Cultivation of Microcystis aeruginosa; S2: Prepare the algae-containing water for the experiment; S3: Take an appropriate amount of the algae-containing water obtained in S2 and transfer it into the reaction apparatus. The experimental temperature of the reaction apparatus is 25℃ and the reaction time is 60min. After the reaction is completed, take a sample immediately and add 200μL Na2S2O3 to quench the unreacted active substances. S4: Under the conditions of ultraviolet light emitted by a 10W mercury lamp, SPC dosage of 6mmol / L, and pH of 7.0, the algae removal efficiency of three oxidation technologies—ultraviolet light oxidation alone, SPC oxidation alone, and ultraviolet-coupled SPC oxidation—was compared. S5: MeOH and TBA are added to the UV / SPC process, respectively, and react with ·OH and CO3· - The reaction was investigated to determine the effect of free radicals on algae removal efficiency; S6: Investigate the influencing factors on algae removal in the UV / SPC advanced oxidation system under five different conditions.

2. The method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology according to claim 1, characterized in that, The culture conditions described in S1 are as follows: Microcystis aeruginosa is cultured in BG11 medium with a light-dark ratio of 12h:12h, a light intensity of 2500 lx, a temperature of 25±1℃, and is shaken once a day.

3. The method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology according to claim 1, characterized in that, S2 includes the following steps: S21: Take an appropriate amount of Microcystis aeruginosa cells grown to the logarithmic growth phase and place them in a centrifuge tube. Centrifuge at 6000 r / min for 10 min, discard the supernatant, centrifuge again to remove the supernatant, and dilute the algal cells to 1×10⁻⁶ with 500 ml of ultrapure water. 6 / ml; S22: The pH of the algal solution obtained in S21 was adjusted to 7.0 using 0.2 mol / L NaOH and 0.2 mol / L phosphoric acid, which is the algal-containing water used in the experiment.

4. The method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology according to claim 1, characterized in that, The first case of S6 is: the effect of SPC dosage on algae removal effect; Under the conditions of ultraviolet light emitted by a 10W mercury lamp and pH 7.0, the effect of SPC dosage range of 1–10 mmol / L on the algae removal efficiency of the UV / SPC oxidation system was compared.

5. The method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology according to claim 1, characterized in that, The second case of S6 is: the effect of algae density on algae removal effect; Under the conditions of SPC dosage of 6 mmol / L, ultraviolet light emitted by a 10W mercury lamp, and pH 7.0, the control algal density concentration range was 5 × 10⁻⁶. 5 / ml to 1×10 7 The effect of / ml on the algae removal efficiency of the UV / SPC oxidation system.

6. The method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology according to claim 1, characterized in that, The third case of S6 is: the effect of pH on algae removal effect; The effect of SPC dosage of 6 mmol / L on algae removal efficiency of UV / SPC oxidation system under ultraviolet light emitted by a 10W mercury lamp was compared with that of pH value range 5 to 11.

7. The method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology according to claim 1, characterized in that, The fourth case in S6 is: the effect of inorganic ions on algae removal effect; Under ultraviolet light emitted by a 10W mercury lamp, with an SPC dosage of 6 mmol / L and a pH of 7.0, Cl - Within the range of 0–10 mmol / L, HCO3 - The effect of 0–10 mmol / L on algae removal efficiency in UV / SPC oxidation systems.

8. The method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology according to claim 1, characterized in that, The fifth case in S6 is: the effect of natural organic matter on algae removal effect; The effects of HA concentrations of 0, 0.5, 1, 3 and 5 mg / L on algae removal in a UV / SPC oxidation system under the conditions of ultraviolet light emitted by a 10W mercury lamp, SPC dosage of 6 mmol / L, and pH of 7.

0.

9. The method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology according to claim 1, characterized in that, The reaction apparatus described in S3 includes: A magnetic stirrer (6) is provided with a quartz column reaction vessel. The reaction vessel is equipped with a quartz sleeve for ultraviolet lamps. The quartz column reaction vessel and the quartz sleeve form a cavity, which is filled with a reaction solution (3). The magnetic stirrer (6) has a water inlet (5) at the lower end of its circumferential surface that is connected to the interior, and a water outlet (2) at the upper end of its circumferential surface that is connected to the interior. The top of the reaction vessel is provided with a sampling port (1), and the bottom wall of the magnetic stirrer (6) is provided with a rotor (4) that rotates with the magnetic stirrer (6) to stir the reaction solution (3).

10. The method for efficient algae removal using ultraviolet-coupled sodium percarbonate advanced oxidation technology according to claim 1, characterized in that, Before each experiment, turn on the UV lamp to preheat for at least 30 minutes.

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