A micro-bubble enhanced cascade discharge plasma reactor and algae removal method

Abstract

The present application relates to the technical field of water pollution treatment, in particular to a micro-bubble enhanced cascade discharge plasma reactor and an algae removal method. The micro-bubble enhanced cascade discharge plasma reactor provided by the present application adopts a three-electrode coaxial structure, connects a high-voltage power supply to a middle porous electrode, and grounds a center and a peripheral electrode, thereby constructing an inner-layer gas-phase pre-ionization zone and an outer-layer gas-liquid mixed-phase reaction zone. Working gas is first discharged in the inner layer to generate high-concentration active particles, then sprayed out through micro-holes to form a micro-bubble group carrying active substances, and induce secondary discharge in the outer layer. Ultraviolet light, shock waves and active substances generated by cascade discharge are used to cooperatively destroy the structure of algae cells, so that the algae cells are inactivated and flocculated, and the algae residue is quickly separated by virtue of the micro-bubble air floatation effect. The method is efficient, low in consumption and free of secondary pollution, and is suitable for emergency and deep treatment of eutrophic water bodies.

Description

Technical Field

[0001] This invention relates to the field of water pollution control technology, specifically to a microbubble-enhanced cascaded discharge plasma reactor and an algae removal method. Background Technology

[0002] Eutrophication leading to algal blooms (especially cyanobacteria) is a global environmental problem. Existing algae control technologies, such as physical harvesting, chemical disinfection, and biological regulation, generally suffer from drawbacks such as low efficiency, secondary pollution, long cycles, or poor adaptability. Low-temperature plasma technology, due to its ability to generate various highly reactive substances in situ (such as hydroxyl radicals and ozone), is considered a green and efficient alternative.

[0003] However, existing plasma water treatment technologies face three major technical bottlenecks in practical applications: 1. High energy consumption: Direct liquid-phase discharge needs to overcome the high dielectric strength of water, resulting in extremely high breakdown voltage, and most of the energy is dissipated as heat; 2. Low mass transfer efficiency: Traditional aeration produces large bubbles with short residence time, making it difficult for the active substances generated by plasma to be efficiently transferred to the water body; 3. Poor adaptability and easy fouling: Fluctuations in the conductivity of outdoor water bodies can easily lead to unstable discharge or electrode ablation, and the electrode surface is easily covered by algal biofilm, resulting in rapid decline in treatment efficiency.

[0004] Therefore, there is an urgent need for a new plasma algae removal method that can simultaneously solve the above problems and achieve efficient, energy-saving, and stable operation. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing methods, this invention provides a microbubble-enhanced cascaded discharge plasma method for algae removal that features low energy consumption, high mass transfer efficiency, adaptability to water quality fluctuations, and self-cleaning function.

[0006] The present invention provides a microbubble-enhanced cascaded discharge plasma reactor, the reactor comprising a central electrode (1), an intermediate electrode (2), an outer electrode (3), an air inlet (4), a fixing plate (5), a fixing rod (6), and a fixture (7).

[0007] The first discharge region is formed between the inner walls of the central electrode (1) and the intermediate electrode (2), with a gap of 1.0 mm to 5.0 mm.

[0008] The outer wall of the intermediate electrode (2) and the outer electrode (3) form a second discharge region with a gap of 5.0 mm to 20.0 mm.

[0009] The effective discharge length of the reactor is 50mm to 500mm;

[0010] This invention controls the electric field intensity ratio between the first discharge region (i.e., the gas phase region) and the second discharge region (i.e., the gas-liquid mixed phase discharge region) by adjusting the above-mentioned gap ratio, so that the gas phase region is preferentially ionized;

[0011] In practical applications of the present invention, the microbubble-enhanced cascaded discharge plasma reactor further includes a gas flow controller for controlling the gas flow rate entering the annular cavity between the central electrode (1) and the intermediate electrode (2) through the inlet (4).

[0012] In this invention, the central electrode (1), intermediate electrode (2) and peripheral electrode (3) in the reactor are three-electrode coaxial structures;

[0013] The central electrode (1) is a solid metal rod, made of stainless steel, titanium or copper, with a polished surface to reduce roughness and prevent local overheating or arc erosion caused by tip discharge. The diameter of the central electrode (1) is 2 mm to 10 mm.

[0014] The intermediate electrode (2) is a metal cylinder with a microporous structure. The intermediate electrode (2) is connected to a high-voltage power supply and is used as a gas phase discharge electrode and a microbubble generator. The material is sintered titanium powder, sintered stainless steel powder, perforated stainless steel or porous foam nickel. The porosity of the microporous structure is 10% to 65%, and the micropore diameter is 10 μm to 500 μm. In actual operation, after the gas is ejected through the micropores, the microbubble diameter formed under the action of surface tension and shear force ranges from 10 μm to 500 μm.

[0015] The peripheral electrode (3) is a water-permeable metal wire mesh or a perforated metal plate, and the material includes 304 stainless steel, 316L stainless steel or titanium. When using metal wire mesh, the metal mesh number is 20 mesh to 100 mesh and the wire diameter is 0.1 mm to 1.0 mm to ensure water permeability and serve as the grounding electrode. The peripheral electrode (3) is coaxially sleeved outside the intermediate electrode (2) and is mechanically fixed and electrically insulated from the center electrode (1) and the intermediate electrode (2) through an insulating flange assembly.

[0016] In this invention, the air inlet (4) is located on the fixed plate (5) and connected to the intermediate electrode (2);

[0017] The number of fixing plates (5) is ≥2, and they are arranged in parallel.

[0018] The air inlet (4) is on the fixed plate (5) and located between the center electrode (1) and the intermediate electrode (2);

[0019] The fixing rod (6) and the fixing device (7) are used to fix the fixing plate (5).

[0020] This invention also provides a method for removing algae and algae-borne harmful aquatic organisms from water using microbubble-enhanced cascaded discharge plasma, the method comprising the following steps:

[0021] Step S1: Construct a dual-region discharge electric field

[0022] Connect the intermediate electrode (2) to the high voltage power supply output terminal and ground the center electrode (1) and the peripheral electrode (3); thereby forming a first discharge region, i.e., a gas phase discharge region, between the center electrode (1) and the intermediate electrode (2), and forming a second discharge region, i.e., a gas-liquid mixed phase discharge region, between the intermediate electrode (2) and the peripheral electrode (3).

[0023] Step S2: Pre-ionization and cascaded discharge

[0024] Algae-containing water is introduced into the discharge reaction zone between the intermediate electrode (2) and the peripheral electrode (3) of the reactor. At the same time, working gas is introduced into the annular cavity (i.e., the first discharge zone) between the central electrode (1) and the intermediate electrode (2) through the air inlet (4). Under the action of the high voltage electric field in the first discharge zone, gas phase discharge occurs, generating an activated gas containing ozone and plasma active particles. The activated gas is ejected through the micropores on the surface of the intermediate electrode (2) and enters the algae-containing water between the intermediate electrode (2) and the peripheral electrode (3), where it is sheared and dispersed into a group of microbubbles carrying active particles. Under the action of the electric field in the second discharge zone, the microbubbles induce secondary discharge inside the bubbles and at the gas-liquid interface.

[0025] Step S3: Algal cell disruption and lethality

[0026] By utilizing the physical and chemical effects generated by the cascade discharge process, the cell walls, cell membranes, and air sac structures of algal cells in the water are synergistically destroyed, causing algal cells to become inactive or lyse. The physical effects include ultraviolet radiation and shock waves, and the chemical effects include the generation of hydroxyl radicals, ozone, and hydrogen peroxide reactive oxygen species.

[0027] Step S4: Air flotation separation and slag removal

[0028] The remaining microbubbles in the fluid adhere to inactivated algal cells or algal flocs, causing them to float to the water surface and form an algal residue layer for solid-liquid separation, thereby achieving the discharge or reuse of clean water.

[0029] In practical applications of this invention, the algae-containing water enters the reactor in any of the following ways:

[0030] Method 1: Control the water to enter the discharge reaction zone between the middle electrode (2) and the outer electrode (3) along the tangential direction to form a spiral flow, and use centrifugal force to enhance gas-liquid separation and mixing;

[0031] Method 2: Control the water to flow directly through the discharge reaction zone between the intermediate electrode (2) and the outer electrode (3) along the axial direction, and use the air lift effect generated by the rise of microbubbles to drive the water flow;

[0032] Method 3: The reactor is directly immersed in an open water body, and the momentum of the gas ejected from the intermediate electrode (2) is used to drive the surrounding water body to automatically flow through the discharge reaction zone between the intermediate electrode (2) and the outer electrode (3).

[0033] The algae and algal-derived harmful aquatic organisms mentioned include cyanobacteria, green algae, diatoms, or red tide organisms;

[0034] This invention inactivates or lyses algal cells by disrupting their cell walls, cell membranes, and air sac structures.

[0035] The physical effects include ultraviolet radiation and shock waves, and the chemical effects include the generation of substances such as hydroxyl radicals, ozone, and reactive oxygen species such as hydrogen peroxide.

[0036] This invention is specifically designed for cyanobacteria with gas bladder structures. It utilizes the shock waves generated by cascaded discharge to crush or shatter their gas bladders, causing them to lose buoyancy and float to the surface by adhering to microbubbles.

[0037] In this invention, the high-voltage power supply is a pulse power supply, an AC power supply, a DC power supply, or a radio frequency power supply;

[0038] When using a pulse power supply, the peak voltage of the pulse is 10kV to 60kV, the repetition frequency is 10Hz to 50kHz, and the rise time is 50ns to 500μs.

[0039] When using AC power, the voltage amplitude is 5kV~50kV and the frequency is 50Hz~100kHz;

[0040] When using a DC power supply, the voltage amplitude is 10kV to 60kV. In actual operation, a current-limiting resistor is also provided to prevent arc discharge.

[0041] The method provided by this invention adopts an intermittent operation mode, and adjusts the duty cycle or power density of the discharge in real time according to the concentration of algae in the influent, so as to control the water temperature rise to not exceed 5°C.

[0042] In this invention, the working gas includes one or more gases selected from air, oxygen, nitrogen, inert gas, or carbon dioxide.

[0043] In this invention, the method further includes online cleaning: when the discharge current of the reactor is detected to decrease or algae and algae-derived harmful aquatic organisms are attached to the surface of the intermediate electrode (2) and the peripheral electrode (3), the output of the high voltage power supply is suspended or reduced, and the pressure and flow rate of the introduced working gas are temporarily increased, and the algae and algae-derived harmful aquatic organisms are removed by the high-pressure pulse airflow formed.

[0044] In this invention, the method also includes a power supply adaptive adjustment function: real-time monitoring of the current waveform or plasma light intensity during the discharge process; when the discharge is unstable or the arc is extinguished due to fluctuations in the water conductivity, the voltage amplitude or pulse frequency of the high-voltage power supply is automatically adjusted according to the fluctuations in the water conductivity.

[0045] In this invention, the method further includes a post-processing step: the algal residue separated in step S4 is collected and dehydrated by a skimming device or an overflow weir, and the treated clean water is returned to the water body or discharged in compliance with standards.

[0046] The present invention provides the application of any of the above-described reactors or methods in the removal of algae and algal-derived harmful aquatic organisms from water bodies.

[0047] This invention provides the application of any of the above-described reactors or methods in in-situ remediation of open water bodies, including lakes, rivers, or landscape water bodies;

[0048] The method of in-situ remediation in open water is as follows: The above-mentioned reactor is immersed in open water. The working gas is sprayed out through the micropores of the intermediate electrode (2) to generate a gas lift pump effect, which drives the external algae-containing water to automatically enter from the bottom of the reactor and flow through the discharge reaction zone between the intermediate electrode (2) and the outer electrode (3). The treated water and bubbles are discharged from the bottom of the fixed plate (5) of the reactor, thereby forming a local circulation convection in the open water.

[0049] The beneficial effects of this invention are:

[0050] This invention provides a method for removing algae from water using microbubble-enhanced cascaded discharge plasma. Compared with existing technologies, its advantages are mainly reflected in the following aspects:

[0051] 1. High efficiency and low energy consumption

[0052] (1) Significantly reduced breakdown voltage and energy consumption: Synergistic effect of gas phase pre-ionization and low breakdown voltage: The cascaded discharge mode of "inner gas phase - outer gas-liquid" is adopted. The inner gas phase region does not need to overcome the dielectric resistance of water and can pre-generate high concentrations of ozone and long-lived active particles with extremely low energy consumption; the outer discharge region injects high-density micron-sized bubbles (average diameter 10~500 μm) into the discharge region, and uses the dielectric strength of the bubble interior and gas-liquid interface, which is much lower than that of pure water, as the "weak point" and "trigger" of the discharge, which greatly reduces the voltage and energy required for plasma breakdown, so that the energy is used more efficiently to generate active materials rather than heating water. This cascaded mode significantly improves energy utilization and active material yield.

[0053] (2) Enhanced mass transfer and synergistic algae removal: Microbubbles provide a huge gas-liquid contact surface area and a longer residence time, which greatly enhances the mass transfer efficiency of ozone generated in the inner layer and reactive oxygen species (such as hydroxyl radicals and ozone) generated by in-situ plasma in the outer layer to the aqueous phase. At the same time, the shock wave generated by the discharge has a specific mechanical destructive effect on cyanobacteria with gas sac structure, realizing the synergistic effect of physical effect and chemical oxidation, and significantly improving the inactivation efficiency of algal cells.

[0054] 2. Environmentally friendly and without secondary pollution

[0055] (1) No chemical additives throughout the process: This method relies entirely on physical discharge and electrochemical reaction, without the need to add any chemical algaecides or flocculants, thus fundamentally avoiding the risk of secondary pollution caused by chemical residues or by-products.

[0056] (2) Clean process: The main products are harmless carbon dioxide, water and a small amount of inorganic salts. The process does not produce toxic and harmful byproducts, and it is a green advanced oxidation technology.

[0057] 3. Strong environmental adaptability and operational stability

[0058] (1) Intelligent power supply adaptive adjustment: By monitoring the discharge current or light intensity in real time, the system can automatically adjust the power supply parameters (voltage, frequency) to cope with the drastic fluctuations in water quality conditions such as conductivity and temperature in the field, maintain a stable glow or streamer discharge state, effectively avoid electrode erosion and efficiency reduction, and ensure reliable operation under different water quality conditions.

[0059] (2) Flexible and adaptable multi-mode operation: Supports multiple operating modes such as vortex flow, direct flow, and submerged in-situ remediation. In particular, the submerged mode can be directly deployed in open water bodies (such as lakes and rivers), using the "airlift pump effect" generated by the rise of microbubbles to drive water circulation, without the need for an external water pump, which greatly simplifies the system and expands the application scenarios.

[0060] 4. Easy to maintain and long-term operation

[0061] (1) Online pulse air washing self-cleaning function: When the efficiency of the electrode is reduced due to algae adhesion, the online cleaning program can be automatically triggered. By instantly increasing the ventilation pressure to form a high-pressure pulse airflow, the strong turbulence and shear force generated by the airflow automatically peel off and wash away the biofilm and dirt on the electrode surface, effectively solving the technical problem of electrode clogging, significantly reducing the maintenance frequency and cost, and ensuring the long-term stable operation of the equipment.

[0062] 5. Integrated processing and rapid separation

[0063] (1) Inactivation and separation integration: In the same reactor, microbubbles successively undertake the dual functions of "enhancing discharge medium" and "air flotation separation carrier". The remaining microbubbles after treatment can effectively adhere to the deactivated algae, realize the rapid floating of algal residue and solid-liquid separation, simplify the process flow and improve the overall treatment efficiency.

[0064] In summary, this invention, through the innovative integration of core technologies such as microbubble-enhanced cascaded discharge, intelligent adaptive control, and online self-cleaning, systematically solves the key bottlenecks of existing plasma water treatment technologies, including high energy consumption, poor mass transfer, weak adaptability, and susceptibility to fouling. It provides an advanced algae removal technology solution that is efficient, energy-saving, environmentally friendly, highly adaptable, and easy to maintain. It is particularly suitable for emergency treatment and deep purification of eutrophic water bodies such as lakes and reservoirs, and has significant technological advancements and broad prospects for industrial application. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of a three-electrode coaxial cascaded discharge reactor.

[0066] In the figure, 1 is the center electrode, 2 is the intermediate electrode, 3 is the outer electrode, 4 is the air inlet, 5 is the fixing plate, 6 is the fixing rod, and 7 is the fixture (as shown in this invention). Figure 1 7 (specifically, the fixing nut).

[0067] Figure 2 This is a schematic diagram of the system's connection principle;

[0068] Figure 3 This is a flowchart of a method for removing algae from water using microbubble-enhanced cascaded discharge plasma. Detailed Implementation

[0069] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0070] Example 1

[0071] Microbubble-enhanced cascaded discharge algae removal technology based on nanosecond pulse power supply

[0072] 1. Experimental Apparatus and Materials

[0073] Reactor: using, for example Figure 1 The diagram shows a three-electrode coaxial cascaded discharge reactor. The central electrode is a solid 304 stainless steel rod with a diameter of 8 mm, polished and grounded. The intermediate electrode is a sintered titanium powder tube with an outer diameter of 20 mm and a wall thickness of 2 mm (average pore size of approximately 30 μm), serving as both a high-voltage discharge electrode and a microbubble generator. The outer electrode is a 40-mesh (approximately 0.42 mm pore size) 316L stainless steel wire mesh, grounded. A first discharge gap of approximately 4 mm is formed between the central and intermediate electrodes; a second discharge gap of approximately 10 mm is formed between the intermediate and outer electrodes. The reactor inlet is designed as a tangential inlet to create swirling flow within the second discharge gap.

[0074] Power supply: A nanosecond pulse high-voltage power supply is used, with adjustable parameters ranging from peak voltage of 10~60 kV, repetition frequency of 10Hz~50 kHz, and pulse rise time of 50 ns~500 μs.

[0075] Gas supply system: An oil-free air compressor is used, and the gas flow rate is precisely controlled by a mass flow controller.

[0076] Water to be treated: A simulated eutrophic water body containing Microcystis aeruginosa was prepared in the laboratory, with an initial chlorophyll a concentration of approximately 150 μg / L and a water temperature of 25±1℃.

[0077] Separation unit: It is subsequently connected to a static air flotation separation tank.

[0078] 2. Methods and Steps

[0079] Step S1: Gas-phase pre-ionization and microbubble generation:

[0080] First, the air compressor is turned on, introducing air into the annular cavity between the central and intermediate electrodes. Then, a nanosecond pulse power supply is activated (parameter settings: peak voltage 25kV, repetition frequency 5 kHz, pulse rise time 200 ns), inducing strong ionization discharge in the inner gas phase region to generate activated gas containing a high concentration of ozone. Next, a water pump is turned on, pumping algae-containing water tangentially into the region between the intermediate and outer electrodes. The activated gas is sheared and dispersed through the micropores of the titanium sintered tube into a cluster of microbubbles with an average diameter of approximately 50–100 μm, constructing a gas-liquid mixed-phase fluid.

[0081] Step S2: Gas-liquid cascade discharge treatment:

[0082] At this point, the high-voltage electric field acts simultaneously on both the inner gas phase region and the outer gas-liquid mixed phase region. Uniform discharge can be observed in the gas phase region, and uniform, dense blue-violet glow discharge can be observed inside and on the surface of the microbubbles, realizing a cascaded discharge mode of "inner gas phase gas generation - outer gas-liquid reaction."

[0083] Step S3: Algal cell disruption and death:

[0084] As algae-containing water flows through the discharge zone, it experiences a synergistic effect from multiple plasma-generated processes during its approximately 2-second dwell time:

[0085] 1) Chemical effects: The high concentration of hydroxyl radicals (·OH), ozone (O3 liquid phase concentration range of 2.0 mg / L ~ 8.0 mg / L) and hydrogen peroxide (H2O2, concentration range of 5.0 mg / L ~ 15.0 mg / L) generated by the discharge directly attack and oxidize the cell wall and cell membrane of algal cells.

[0086] 2) Physical effects: The discharge is accompanied by ultraviolet radiation (wavelength range 200 nm ~ 400 nm) and strong shock waves (peak pressure range 1.0 MPa ~ 20.0 MPa). In particular, the shock waves can effectively crush the gas bladder structure of cyanobacteria, causing them to lose their buoyancy regulation ability and causing physical damage.

[0087] Step S4: Air Flotation Separation and Sludge Removal: The treated gas-liquid mixture enters a static air flotation separation tank. Residual microbubbles that did not participate in the discharge reaction quickly adhere to the surface of the deactivated and broken algal cells, forming "bubble-algae" flocs. Under buoyancy, the flocs rapidly float to the water surface, forming a thick layer of algal residue. The algal residue is periodically removed using a skimming device, and the clear water at the bottom is discharged or reused after meeting standards.

[0088] The flowchart of the method for removing algae from water using the microbubble-enhanced cascaded discharge plasma provided by this invention is as follows: Figure 3 As shown.

[0089] Combination Figure 2 The system connection diagram shown below illustrates the overall operating logic of this embodiment:

[0090] The entire algae removal system integrates air, water, and electrical control units. In the air circuit, an air pump is connected to the air inlet at the top of the reactor via a pipeline, pressurizing gas into the inner gas phase cavity formed by the central and intermediate electrodes, where gas pre-ionization is completed. In the electrical circuit, the output of the high-voltage power supply is directly connected to the central porous electrode, utilizing the dual potential difference formed by it, the central ground electrode, and the outer ground electrode to simultaneously drive the inner gas phase discharge and the outer gas-liquid mixed phase discharge. In the water circulation, algae-containing raw water enters the outer reaction zone through a side inlet. After being fully treated by microbubble clusters carrying highly active particles, the gas-liquid mixture is discharged from the top outlet and directly enters the subsequent air flotation separation unit, where the buoyancy of the residual microbubbles achieves automatic separation and collection of algae residue.

[0091] 3. Effect Analysis

[0092] Algae removal efficiency: After a single treatment, the chlorophyll a concentration in the effluent dropped to below 10 μg / L, and the removal rate of Microcystis aeruginosa exceeded 93%.

[0093] Energy consumption and temperature rise: During the treatment process, the water temperature rise is less than 2°C, which is much lower than the temperature rise of traditional liquid phase discharge (usually >10°C), proving that microbubbles significantly reduce discharge energy consumption, and the energy is efficiently used to generate active substances rather than heating the water.

[0094] Microscopic observation: Under a microscope, the treated algal cells showed that more than 90% of the cell air sacs ruptured and the cell structure lost its integrity, confirming the synergistic algae-killing effect of physical and chemical effects.

[0095] Example 2

[0096] Power adaptive adjustment function demonstration

[0097] This embodiment is used to demonstrate the adaptive and stable operation capability of the method of the present invention in the face of drastic fluctuations in water quality (especially conductivity).

[0098] 1. The experimental setup was based on the apparatus of Example 1, but the power supply was replaced with an adjustable AC high-voltage power supply with an intelligent control unit (output range: voltage amplitude 5~50 kV, frequency 50 Hz~100 kHz). The control unit collected the discharge current waveform in real time for feedback control.

[0099] 2. Adaptive process simulation

[0100] Operating Condition A: Low Conductivity Water Inlet Simulation (e.g., Rainy Season): The inlet water conductivity is adjusted to an extremely low level (approximately 50 μS / cm). After system startup, the control unit detects that the effective value of the discharge current is far below the set threshold for stable discharge, indicating "difficulty in ignition." The system then automatically executes a boost program, gradually increasing the output voltage from the initial setting of 15 kV. When the voltage rises to approximately 22 kV, a stable and continuous flowing discharge current waveform is detected. The system locks this voltage parameter, successfully maintaining the discharge.

[0101] Operating Condition B: High Conductivity Inlet Water Simulation (e.g., during a dry season or pollution event): The inlet water conductivity is suddenly switched to a high value of 800 μS / cm. At this time, the control unit immediately detects abnormal spike pulses in the current waveform (indicating a possible development of arc discharge). The system triggers protection and regulation procedures within 10 milliseconds.

[0102] 1) Quickly reduce the voltage amplitude from 22 kV to 12 kV;

[0103] 2) At the same time, adjust the power supply frequency from 50 Hz to 20 kHz to match the changed load impedance.

[0104] Results: Throughout the entire simulated process of drastic fluctuations in water quality, the reactor maintained a stable glow / streamer discharge state without any electrode erosion, power overload tripping, or discharge extinguishing.

[0105] No chemical agents (such as NaCl) were added to the water to adjust conductivity throughout the process, thus avoiding secondary pollution.

[0106] Example 3

[0107] In-situ remediation of open water bodies and online pulse air washing maintenance

[0108] This embodiment simulates the in-situ application and long-term operation and maintenance of the method of the present invention in a real open water body (such as a landscape pond).

[0109] 1. Device Deployment and Operation Mode: The water inlet pump and closed pipeline in Example 1 are removed. The entire reactor (with waterproof treatment of the power connection cable and air supply pipe) is directly submerged to a depth of about 0.5 meters below the surface of the pond to be repaired, and kept vertical.

[0110] In-situ remediation mechanism: After the air pump and power are turned on, gas is ejected from the micropores of the central electrode, forming a cluster of microbubbles. These bubbles rise rapidly within the annular gap, generating a significant "air-pump effect." This rising water flow creates a negative pressure zone at the bottom of the reactor, automatically drawing in surrounding algae-containing water. After treatment in the discharge reaction zone, the water is discharged from the top. This process creates a continuous local water circulation within the pond, achieving in-situ remediation without the need for an external water pump.

[0111] 2. Online pulse air washing function demonstration

[0112] Contamination Simulation and Detection: After 24 hours of continuous operation, a biofilm gradually formed on the electrode surface due to algae adhesion. The system control unit monitored that, under the same power parameters, the effective value of the discharge current decreased by approximately 18% compared to the initial value.

[0113] Cleaning Triggering and Execution: When the current decay exceeds a preset threshold (e.g., 15%), the system automatically enters "online cleaning mode". The specific operation is as follows:

[0114] 1) The high-voltage power supply is suspended from output or switched to a low maintenance voltage;

[0115] 2) The air circuit control valve opens fully instantaneously, raising the air pressure from the normal operating pressure of 0.1 MPa to 0.4 MPa within 0.5 seconds, forming a high-pressure pulse airflow that lasts for several seconds.

[0116] Cleaning effect: The high-pressure pulsed airflow generates intense turbulence, shearing, and even cavitation effects on the electrode surface and within the micropores, effectively stripping away and washing away algae biofilms and inorganic scale adhering to the titanium electrodes and stainless steel mesh surfaces. After the cleaning process lasts approximately 30 seconds, the system automatically returns to normal ventilation pressure and discharge parameters.

[0117] Verification of effectiveness: After the cleaning was completed, the discharge current monitored by the system recovered to more than 95% of the initial level, proving that the online pulse air washing function can effectively remove electrode clogging, restore processing efficiency, and ensure long-term stable operation.

[0118] Although specific embodiments of the present invention have been described in detail, those skilled in the art can make further modifications and substitutions to the details of the technical solutions of the present invention based on all the teachings disclosed, and all such modifications and substitutions are within the scope of protection of the present invention. The full scope of the present invention is given by the appended claims and any equivalents.

Claims

1. A microbubble-enhanced cascaded discharge plasma reactor, characterized in that, The reactor includes a central electrode (1), an intermediate electrode (2), an outer electrode (3), an air inlet (4), a fixing plate (5), a fixing rod (6), and a fixture (7). The first discharge region is formed between the inner walls of the central electrode (1) and the intermediate electrode (2), with a gap of 1.0 mm to 5.0 mm. The outer wall of the intermediate electrode (2) and the outer electrode (3) form a second discharge region with a gap of 5.0 mm to 20.0 mm. The effective discharge length of the reactor is 50mm to 500mm; The reactor has a three-electrode coaxial structure consisting of a central electrode (1), an intermediate electrode (2), and an outer electrode (3). The intermediate electrode (2) is connected to a high-voltage power supply, while the central electrode (1) and the outer electrode (3) are grounded. The central electrode (1) is a solid metal rod; The intermediate electrode (2) is a metal cylinder with a microporous structure; The peripheral electrode (3) is a metal wire mesh or a perforated metal plate; The air inlet (4) is on the fixed plate (5) and located between the center electrode (1) and the intermediate electrode (2); The number of fixing plates (5) is ≥2, and they are arranged in parallel. The central electrode (1), intermediate electrode (2) and peripheral electrode (3) are located in the middle of the fixed plate (5) and are connected to the fixed plate (5); The fixing rod (6) and the fixing device (7) are used to fix the fixing plate (5).

2. The reactor according to claim 1, characterized in that, The diameter of the central electrode (1) is 2mm to 10mm; The porosity of the microporous structure of the intermediate electrode (2) is 10% to 65%, and the micropore diameter is 10 μm to 500 μm; When the peripheral electrode (3) uses a metal wire mesh, the mesh size of the metal wire mesh is 20 to 100 mesh and the wire diameter is 0.1 mm to 1.0 mm.

3. A method for removing algae and algae-borne harmful aquatic organisms from water using the microbubble-enhanced cascaded discharge plasma reactor according to any one of claims 1-2, characterized in that, The method includes the following steps: S1: Connect the intermediate electrode (2) to the high voltage power supply, and ground the center electrode (1) and the peripheral electrode (3); S2: Water containing algae and algae-derived harmful aquatic organisms is introduced into the second discharge zone through the peripheral electrode (3), and working gas is introduced into the first discharge zone between the central electrode (1) and the intermediate electrode (2) through the air inlet (4). Gas phase discharge occurs in the first discharge zone, generating activation gas. S3: The activated gas is sheared and dispersed into a group of microbubbles carrying active particles by the microporous structure on the surface of the intermediate electrode (2). The microbubbles induce secondary discharge under the electric field of the second discharge zone, and the physical and chemical effects generated by the discharge destroy the cell structure and air sac structure of algae and algae-derived harmful aquatic organisms. S4: Utilizing the flotation effect of microbubbles to float inactive algae and algal-derived harmful aquatic organisms, thereby achieving solid-liquid separation between the water body and the inactive algae and algal-derived harmful aquatic organisms.

4. The method according to claim 3, characterized in that, The high-voltage power supply is a pulse power supply, AC power supply, DC power supply or radio frequency power supply; When using a pulse power supply, the peak voltage of the pulse is 10kV to 60kV, the repetition frequency is 10Hz to 50kHz, and the rise time is 50ns to 500μs. When using AC power, the voltage amplitude is 5kV~50kV and the frequency is 50Hz~100kHz; When using a DC power supply, the voltage amplitude is 10kV to 60kV.

5. The method according to claim 3, characterized in that, The working gas includes one or more gases selected from air, oxygen, nitrogen, inert gases, or carbon dioxide.

6. The method according to claim 3, characterized in that, The method also includes online cleaning: when the reactor discharge current decreases or algae and algae-derived harmful aquatic organisms are attached to the surface of the intermediate electrode (2) and the peripheral electrode (3), the high-voltage power output is suspended or reduced, and the pressure and flow rate of the introduced working gas are temporarily increased to remove algae and algae-derived harmful aquatic organisms by utilizing the high-pressure pulse airflow formed.

7. The method according to claim 3, characterized in that, The method also includes a power supply adaptive adjustment function: real-time monitoring of the current waveform or plasma light intensity during the discharge process; when the discharge is unstable or the arc is extinguished due to fluctuations in the water conductivity, the voltage amplitude or pulse frequency of the high-voltage power supply is automatically adjusted according to the fluctuations in the water conductivity.

8. The application of the reactor according to any one of claims 1-2 or the method according to any one of claims 3-7 in in-situ remediation of open water bodies, characterized in that, The open water bodies include lakes, rivers, or landscape water bodies; The method for in-situ remediation in open water is as follows: the reactor described in any one of claims 1 to 2 is immersed in open water. The working gas is sprayed out through the micropores of the intermediate electrode (2) to generate a gas lift pump effect, which drives the external algae-containing water to automatically enter from the bottom of the reactor and flow through the discharge reaction zone between the intermediate electrode (2) and the peripheral electrode (3). The treated water and bubbles are discharged from the top of the reactor, thereby forming a local circulation convection in the open water.

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