Submerged plant type microbial fuel cell ecological remediation system and method

Abstract

The present application relates to the technical field of ecological management, and discloses a submerged plant type microbial fuel cell ecological restoration system and method, which comprises a modular reactor, which is divided into a surface aeration adjustment layer, a submerged plant growth layer, a functional substrate layer, a sediment and anode layer and a bottom support layer from top to bottom. The root system of the submerged plant extends to the upper part of the sediment and anode layer, and the oxygen generated by the root system supplies oxygen for the cathode area through radial oxygen loss; the root exudates provide carbon sources for the electrochemically active microorganisms in the anode area. The functional substrate layer is composed of agricultural waste biochar and aerated concrete blocks, which can synergistically adsorb pollutants, assist in conduction and promote the degradation of nutrient salts. The present application realizes the synergy of plant absorption, microbial electrochemical degradation and substrate adsorption, simultaneously and efficiently removes COD, TN and TP, improves water transparency, recovers bioelectricity, has the advantages of low energy consumption, modularity, no secondary pollution, and is suitable for in-situ and side restoration of eutrophic and black and odorous water bodies.

Description

Technical Field

[0001] This invention relates to the field of ecological restoration technology, specifically to an ecological restoration system and method for submerged plant-based microbial fuel cells. Background Technology

[0002] In the current treatment of polluted rivers and lakes, three types of technologies—constructed wetlands (CW), sediment-microbial fuel cells (SMFC), and constructed wetlands coupled with microbial fuel cells (CW-SMFC)—have all achieved certain results in addressing the problems of eutrophication and excessive organic pollutants.

[0003] Constructed wetlands (CWs) rely on the synergistic effects of aquatic plants, substrates, and microorganisms to remove pollutants. They have the advantages of being eco-friendly and cost-effective, but they also have significant drawbacks: ① Low decontamination efficiency, with low removal rates of total nitrogen (TN) and total phosphorus (TP) in low-concentration river and lake waters. Insufficient dissolved oxygen (DO) at the cathode limits nitrification, and microbial activity is inhibited by low temperatures. ② High greenhouse gas emissions, with methanogens releasing CH4 under anaerobic conditions and N2O released due to nitrification-denitrification imbalance. ③ Limited improvement in water transparency, as emergent plant roots can only fix surface sediments and cannot inhibit the resuspension of deep bottom sediments. Furthermore, they have a weak ability to degrade dissolved organic pollutants (such as antibiotics and dyes).

[0004] Sediment microbial fuel cells (SMFCs) are a type of bioelectrochemical system that effectively converts chemical energy from sediments and organic matter from wastewater into bioelectricity through the oxidation function of electrochemically active bacteria (EABs). During the oxidation of organic matter at the anode, protons are released and propagate to the cathode via wastewater or a membrane, while electrons propagate to the cathode via an external circuit. However, their application in river and lake management faces several limitations: ① High energy consumption, requiring artificial aeration to supplement cathode dissolved oxygen (DO), resulting in high operating costs; ② Strong substrate dependence, with low COD in rivers and lakes leading to insufficient organic substrate at the anode, resulting in power densities often <10 mW / m²; ③ Poor ecological adaptability, lacking plant-mediated carbon source supplementation, and prone to decontamination performance due to EAB activity decay during long-term operation, and unable to stabilize sediment structure, easily leading to secondary pollution.

[0005] Constructed wetland coupled sediment-microbe fuel cell (CW-SMFC): The combination of CW and MFC enables synergistic and enhancing effects between the two systems, primarily due to increased electron transfer or flow that enhances the redox reaction rates and efficiency at both the cathode and anode. Limited soluble electron acceptors at the cathode can hinder reactions and reduce system efficiency, while the introduction of plants provides additional oxygen as electron acceptors through root exudation. The organic matter released from the roots also provides more readily biodegradable compounds, promoting power generation and nitrogen removal. Existing limitations of this technology include: ① Risk of electrode damage: Emergent plant roots are much more extensive than submerged plants, and excessive growth can physically puncture the anode, leading to short circuits and requiring regular pruning and maintenance; ② Microenvironmental disturbance: Radial oxygen loss from emergent plants can easily diffuse into the anaerobic zone of the anode, inhibiting EAB activity and reducing power generation performance; ③ Insufficient removal of organic pollutants: Emergent plant root exudates are mainly cellulose, which is difficult for EAB to utilize, resulting in reduced degradation rates of recalcitrant organic pollutants (such as polycyclic aromatic hydrocarbons and antibiotics).

[0006] The core deficiency of the aforementioned technologies can be attributed to insufficient synergistic purification efficiency of the eco-electrochemical approach, including:

[0007] 1. Imbalance between oxygen supply and anaerobic digestion: Neither CW nor CW-SMFC alone can accurately control DO distribution. Insufficient DO at the cathode limits nitrification, while excessive DO at the anode inhibits EAB. MFC alone relies on artificial aeration, which violates the low-energy consumption requirement of ecological governance.

[0008] 2. Lack of microbial community regulation: Existing technologies do not selectively enrich functional microorganisms. EAB competes with methanogens and denitrifying bacteria for substrates, resulting in low nitrogen and phosphorus removal and low power generation efficiency. Furthermore, the lack of plant growth-promoting bacteria makes it impossible to synergistically enhance the plant's ability to absorb nitrogen and phosphorus.

[0009] 3. Poor plant-electrode-matrix matching: The root system of emergent plants conflicts with the electrode layout, the matrix has limited adsorption capacity and no conductivity, and cannot assist in electron transfer; although submerged plants have advantages such as controllable ROL and short root system, existing studies have not combined them with MFC, and no suitable system configuration has been developed.

[0010] 4. Risk of secondary pollution: The CW matrix alone is prone to saturation and release of phosphorus, the decay of emergent plant remains releases organic matter, and the MFC electrode alone may leach heavy metals, all of which pose a risk of secondary pollution. Summary of the Invention

[0011] This invention provides an ecological restoration system and method for submerged plant-based microbial fuel cells to solve the above-mentioned problems.

[0012] In a first aspect, the present invention provides an ecological restoration system for a submerged plant-type microbial fuel cell, including a modular reactor. The modular reactor is a vertically arranged columnar structure, and its inner cavity is divided from top to bottom into a surface aeration and regulation layer, a submerged plant growth layer, a functional matrix layer, a sediment and anode layer, and a bottom support layer.

[0013] An anode assembly is provided in the sediment and anode layer, and a cathode is provided in the surface aeration regulating layer. The anode assembly and the cathode are connected by an external circuit.

[0014] The submerged plant growth layer contains submerged plants, whose roots penetrate the functional matrix layer and extend to the upper part of the sediment and anode layer.

[0015] The modular reactor has an inlet at the lower part of its sidewall and an outlet at the upper part of its sidewall.

[0016] The anode assembly, cathode, external circuit, and submerged plants constitute a microbial fuel cell.

[0017] This technical solution achieves synergistic enhancement of decontamination, power generation, and ecological restoration through the combined design of submerged plants, microbial batteries, and functional substrates, overcoming the limitations of insufficient synergy and limited functionality of individual CW or SMFC systems, or emergent plants coupled with CW-MFC systems.

[0018] Electrochemical synergy between submerged plants and SMFC: Submerged plants replenish dissolved oxygen at the cathode through photosynthesis, thereby increasing the overall DO level, replacing the artificial aeration of traditional SMFC, and reducing energy consumption; at the same time, root exudates provide easily degradable carbon sources for anodic electrochemically active bacteria, thus increasing EAB abundance.

[0019] Ecological synergy between submerged plants and substrates: functional substrates adsorb suspended solids in water, improving TSS removal rate, while the roots of submerged plants fix sediments. Together, they improve water transparency; moreover, plants can directly absorb nitrogen and phosphorus from the water, reducing nutrient load.

[0020] In one optional embodiment, the functional matrix layer is composed of biochar and aerated concrete blocks mixed at a volume ratio of 1:1 to 1:3. The raw material for the biochar is corn cob with a particle size of 2-5 mm and a specific surface area ≥800 m² / g. The particle size of the aerated concrete blocks is 3-5 mm. A quartz sand cushion layer with a thickness of 3-5 cm is laid at the bottom of the functional matrix layer.

[0021] In one alternative embodiment, the anode assembly includes at least one anode plate and a bracket for fixing the anode plate, the anode plate being horizontally disposed within the deposit and the anode layer;

[0022] The anode plate is made of biochar-modified graphite felt. The modified raw material is biochar prepared from agricultural waste. After being calcined at 500℃ for 2 hours, it is pulverized to a particle size of 1-2 mm and a specific surface area of ​​800 m² / g. The graphite felt is prepared by soaking in a 5% biochar suspension, then drying at 80℃ for 2 hours, and repeating the process twice to ensure that the biochar is evenly attached to the surface of the graphite felt.

[0023] In one optional embodiment, the anode plate is provided with a plurality of planting holes for the roots of submerged plants to pass through, the diameter of the planting holes being 0.8-1.2 cm.

[0024] In one alternative embodiment, the cathode is a floating cathode, comprising a graphite felt substrate, a buoyancy block fixed to the upper part of the graphite felt substrate, and a connecting rope for suspension.

[0025] The cathode is configured to be suspended in the surface aeration conditioning layer via the connecting rope.

[0026] In one optional embodiment, the surface of the cathode is coated with a composite catalyst layer of Fe3O4 and activated carbon;

[0027] Fe3O4 and activated carbon composite catalyst were mixed with polytetrafluoroethylene at a mass ratio of 9:1, and deionized water was added to form a paste. The paste was then evenly sprayed onto the cathode surface using a spray gun, with a coating thickness of 0.5 mm, and dried at 80°C for 1 hour.

[0028] In one optional embodiment, the submerged plant is selected from at least one of Potamogeton malaianus, Hydrilla verticillata, Vallisneria natans, Potamogeton pectinatus, Potamogeton crispus, or Myriophyllum spicatum; the planting density of the submerged plant is 20-40 plants / m².

[0029] In one optional embodiment, the inlet is connected to an annular perforated water distributor, which is located below the sediment and anode layer; the outlet is located below the surface aeration regulating layer, and its inner side is provided with a nylon intercepting mesh and a microporous filter membrane in sequence.

[0030] In one alternative implementation, the external circuitry includes an adjustable resistor and a data acquisition unit;

[0031] It also includes auxiliary components, which include at least one of the following: an aeration device disposed on the surface aeration regulating layer, a plant supplemental light disposed on the top of the modular reactor, and a heating rod disposed on the sediment and anode layer.

[0032] Secondly, the present invention also provides a method for ecological restoration of submerged plant-based microbial fuel cells, comprising the following steps:

[0033] The modular reactor is filled from bottom to top with a bottom support layer, sediment, and anode layer sediment; the anode assembly is installed; the functional matrix layer is filled; the cathode is installed and connected to the external circuit.

[0034] Select submerged plant seedlings, insert their roots through the planting holes of the anode plate, so that the ends of the roots contact the surface of the sediment, and fill some functional matrix around the roots for fixation;

[0035] Introduce the river or lake water to be treated and adjust the hydraulic retention time; close the external circuit, adjust the resistance to 800-1200Ω, and start the microbial fuel cell;

[0036] Regularly monitor the output voltage, current, and effluent water quality, and adjust the hydraulic retention time or circuit status according to the water quality; regularly harvest submerged plants and replenish or replace the substrate in the functional substrate layer.

[0037] In one optional implementation, during the steps of introducing the river or lake water to be treated, adjusting the hydraulic residence time, closing the external circuit, adjusting the resistance to 800-1200Ω, and starting the microbial fuel cell, the external circuit is kept closed when the system aims to enhance pollutant removal and power generation; the external circuit is disconnected when the system aims to enhance plant absorption of nitrogen and phosphorus. Attached Figure Description

[0038] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the structure of a submerged plant-based microbial fuel cell ecological restoration system according to an embodiment of the present invention.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1. Modular reactor;

[0042] 2. Surface aeration conditioning layer;

[0043] 3. Submerged plant growth layer;

[0044] 4. Functional matrix layer;

[0045] 5. Sediments and anode layer;

[0046] 6. Bottom support layer;

[0047] 7. Water inlet;

[0048] 8. Water outlet;

[0049] 9. Anode plate;

[0050] 10. Cathode;

[0051] 11. Submerged plants;

[0052] 12. Circular perforated water distributor;

[0053] 13. Adjustable resistor. Detailed Implementation

[0054] 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.

[0055] In the current treatment of polluted rivers and lakes, three types of technologies—constructed wetlands (CW), sediment-microbial fuel cells (SMFC), and constructed wetlands coupled with microbial fuel cells (CW-SMFC)—have all achieved certain results in addressing the problems of eutrophication and excessive organic pollutants.

[0056] Constructed wetlands (CWs) rely on the synergistic effects of aquatic plants, substrates, and microorganisms to remove pollutants. They have the advantages of being eco-friendly and cost-effective, but they also have significant drawbacks: ① Low decontamination efficiency, with low removal rates of total nitrogen (TN) and total phosphorus (TP) in low-concentration river and lake waters. Insufficient dissolved oxygen (DO) at the cathode limits nitrification, and microbial activity is inhibited by low temperatures. ② High greenhouse gas emissions, with methanogens releasing CH4 under anaerobic conditions and N2O released due to nitrification-denitrification imbalance. ③ Limited improvement in water transparency, as emergent plant roots can only fix surface sediments and cannot inhibit the resuspension of deep bottom sediments. Furthermore, they have a weak ability to degrade dissolved organic pollutants (such as antibiotics and dyes).

[0057] Sediment microbial fuel cells (SMFCs) are a type of bioelectrochemical system that effectively converts chemical energy from sediments and organic matter from wastewater into bioelectricity through the oxidation function of electrochemically active bacteria (EABs). During the oxidation of organic matter at the anode, protons are released and propagate to the cathode via wastewater or a membrane, while electrons propagate to the cathode via an external circuit. However, their application in river and lake management faces several limitations: ① High energy consumption, requiring artificial aeration to supplement cathode dissolved oxygen (DO), resulting in high operating costs; ② Strong substrate dependence, with low COD in rivers and lakes leading to insufficient organic substrate at the anode, resulting in power densities often <10 mW / m²; ③ Poor ecological adaptability, lacking plant-mediated carbon source supplementation, and prone to decontamination performance due to EAB activity decay during long-term operation, and unable to stabilize sediment structure, easily leading to secondary pollution.

[0058] Constructed wetland coupled sediment-microbe fuel cell (CW-SMFC): The combination of CW and MFC enables synergistic and enhancing effects between the two systems, primarily due to increased electron transfer or flow that enhances the redox reaction rates and efficiency at both the cathode and anode. Limited soluble electron acceptors at the cathode can hinder reactions and reduce system efficiency, while the introduction of plants provides additional oxygen as electron acceptors through root exudation. The organic matter released from the roots also provides more readily biodegradable compounds, promoting power generation and nitrogen removal. Current research limitations include: ① Risk of electrode damage: Emergent plant root systems are much more extensive than submerged plant root systems, and excessive growth can physically puncture the anode, leading to short circuits and requiring regular pruning and maintenance; ② Microenvironmental disturbance: Radial oxygen loss from emergent plants can easily diffuse into the anaerobic zone of the anode, inhibiting EAB activity and reducing power generation performance; ③ Insufficient removal of organic pollutants: Emergent plant root exudates are mainly cellulose, which is difficult for EAB to utilize, resulting in reduced degradation rates of recalcitrant organic pollutants (such as polycyclic aromatic hydrocarbons and antibiotics).

[0059] The core deficiency of the aforementioned technologies can be attributed to insufficient synergistic purification efficiency of the eco-electrochemical approach, including:

[0060] 1. Imbalance between oxygen supply and anaerobic digestion: Neither CW nor CW-SMFC alone can accurately control DO distribution. Insufficient DO at the cathode limits nitrification, while excessive DO at the anode inhibits EAB. MFC alone relies on artificial aeration, which violates the low-energy consumption requirement of ecological governance.

[0061] 2. Lack of microbial community regulation: Existing technologies do not selectively enrich functional microorganisms. EAB competes with methanogens and denitrifying bacteria for substrates, resulting in low nitrogen and phosphorus removal and low power generation efficiency. Furthermore, the lack of plant growth-promoting bacteria makes it impossible to synergistically enhance the plant's ability to absorb nitrogen and phosphorus.

[0062] 3. Poor plant-electrode-matrix matching: The root system of emergent plants conflicts with the electrode layout, the matrix has limited adsorption capacity and no conductivity, and cannot assist in electron transfer; although submerged plants have advantages such as controllable ROL and short root system, existing studies have not combined them with MFC, and no suitable system configuration has been developed.

[0063] 4. Risk of secondary pollution: The CW matrix alone is prone to saturation and release of phosphorus, the decay of emergent plant remains releases organic matter, and the MFC electrode alone may leach heavy metals, all of which pose a risk of secondary pollution.

[0064] The following is combined with Figure 1 The following describes embodiments of the present invention.

[0065] According to an embodiment of the present invention, a submerged plant-based microbial fuel cell ecological restoration system is provided, comprising a modular reactor 1, which is a vertically arranged columnar structure. Its inner cavity is divided from top to bottom into a surface aeration regulating layer 2, a submerged plant growth layer 3, a functional matrix layer 4, a sediment and anode layer 5, and a bottom support layer 6. An anode assembly is disposed within the sediment and anode layer 5, and a cathode 10 is disposed within the surface aeration regulating layer 2. The anode assembly and cathode 10 are connected via an external circuit. Submerged plants 11 are planted within the submerged plant growth layer 3, and the roots of the submerged plants 11 penetrate the functional matrix layer 4 and extend to the upper part of the sediment and anode layer 5. An inlet 7 is provided at the lower part of the side wall of the modular reactor 1, and an outlet 8 is provided at the upper part of the side wall of the modular reactor 1. The anode assembly, cathode 10, external circuit, and submerged plants 11 constitute a microbial fuel cell.

[0066] This system is a modular, connectable reactor, available in two types: in-situ remediation (directly introduced into polluted rivers and lakes) and shoreline-side placement (built on the shore, treating water via pipelines). Both types share the same core structure, differing only in their installation methods. The system consists of five layers from top to bottom: a surface aeration and conditioning layer 2 → a submerged plant growth layer 3 → a functional matrix layer 4 → a sediment and anode layer 5 → a bottom support layer 6. The total height is 120-150cm, and each module has a diameter of 80-100cm (volume 500-800L). Multiple modules can be connected in parallel via flanges (treatment capacity can be expanded as needed).

[0067] Preferably, the modular reactor 1 uses glass fiber reinforced plastic (FRP) instead of acrylic or stainless steel. FRP has strong weather resistance, is lightweight, low cost, and is resistant to water corrosion, withstanding pH values ​​of 5-9, making it suitable for most river and lake water bodies. The modular reactor 1 has a total height of 150cm, an outer diameter of 100cm, and a wall thickness of 8mm (to ensure pressure resistance and withstand pressure up to 3m underwater); the layered structure consists of: a bottom support layer 6 (10cm), a sediment and anode layer 5 (40cm), a functional matrix layer 4 (30cm), a submerged plant growth layer 3 (50cm), and a surface aeration conditioning layer 2 (20cm).

[0068] Inlet 7 is located on the lower side wall of modular reactor 1, 15cm from the bottom support layer, ensuring that wastewater first contacts the anaerobic zone of sediment before flowing through the anode reaction zone, avoiding short-circuiting. Outlet 8 is located on the upper side wall of modular reactor 1, and is a lateral horizontal pipe, 5cm from the bottom of the surface aeration regulating layer 2. Two protective layers are installed inside the pipe: the outer layer is a 30-mesh nylon mesh (0.5mm aperture) to intercept residual submerged plant leaves and larger suspended solids (such as algal aggregates) in the water, preventing subsequent filter membrane clogging; the inner layer is a 0.45μm PVDF (polyvinylidene fluoride) hydrophilic filter membrane to trap fine colloids and improve the transparency of the effluent; outlet 8 is connected to an overflow pipe (1% slope) to ensure that the effluent is evenly discharged into the river and lake, avoiding water level fluctuations from affecting system stability.

[0069] In this embodiment, the sediment and anode layer 5 is filled with sediment or similar components from the target water body to simulate a natural bottom sediment environment. More importantly, an anode assembly is installed inside this layer. The anode assembly is connected to the cathode 10 located in the surface aeration conditioning layer 2 via an external circuit, so that the anode assembly, cathode 10, external circuit, and submerged plants 11 (described below) together constitute a complete microbial fuel cell (MFC). When wastewater flows through this layer, the sediment and organic matter in the water are oxidized by electrochemically active bacteria at the anode, generating electrons and protons. The electrons are transferred to the cathode 10 through the external circuit, forming an electric current, thus realizing the conversion of biomass energy into electrical energy.

[0070] The roots of the submerged plant 11 grow downwards from the upper submerged plant growth layer 3, and must pass through the intermediate functional matrix layer 4, eventually extending to the upper region of the sediment and anode layer 5. This root arrangement allows the plant roots to have close physical and biochemical interactions with the anode region: root exudates can provide an additional carbon source for the electrochemically active bacteria in the anode region.

[0071] During operation, polluted water enters the bottom through inlet 7 and flows sequentially through sediment and anode layer 5 (where anaerobic degradation and electricity generation occur), functional matrix layer 4 (for filtration and adsorption), submerged plant growth layer 3 (for plant absorption and root action), and surface aeration and regulation layer 2 (for gas exchange and cathode reaction 10). In this process, pollutants are removed through multiple pathways, including microbial electrochemical degradation, plant absorption, and matrix adsorption, while the system outputs bioelectricity. The deep extension of the submerged plant root system 11 achieves a deep spatial and functional synergy between phytoremediation and microbial fuel cell technology.

[0072] This technical solution achieves synergistic enhancement of decontamination, power generation, and ecological restoration through the combined design of submerged plants, microbial batteries, and functional substrates, overcoming the limitations of insufficient synergy and limited functionality of individual CW or SMFC systems, or emergent plants coupled with CW-MFC systems.

[0073] 1. Electrochemical synergy between submerged plants and SMFC: Submerged plants 11 supplement dissolved oxygen for cathode 10 through photosynthetic oxygen release, improve the overall DO level, replace the artificial aeration of traditional SMFC, and reduce energy consumption; at the same time, root exudates provide easily degradable carbon sources for anodic electrochemically active bacteria, thereby increasing EAB abundance.

[0074] 2. Ecological synergy between submerged plants and substrate: The functional substrate adsorbs suspended solids in the water, improving the TSS (total suspended solids) removal rate, while the roots of submerged plants fix the sediment. The synergy between the two improves the water transparency; moreover, the plants can directly absorb nitrogen and phosphorus from the water, reducing the nutrient load.

[0075] In one embodiment, the functional matrix layer 4 is composed of biochar and aerated concrete blocks mixed in a volume ratio of 1:1 to 1:3. The raw material for the biochar is corn cob with a particle size of 2-5 mm and a specific surface area of ​​≥800 m² / g. The particle size of the aerated concrete blocks is 3-5 mm. A quartz sand cushion layer with a thickness of 3-5 cm is laid at the bottom of the functional matrix layer 4.

[0076] Preferably, the functional matrix layer 4 is composed of a mixture of biochar and aerated concrete blocks at a volume ratio of 1:2. It is filled in layers, with a 5cm thick layer of quartz sand at the bottom and a 45cm thick layer of the mixed matrix of biochar and aerated concrete blocks on top. Each layer is compacted in 10cm layers to prevent later settling. Specifically, the layered filling is done manually. Before filling, the matrix is ​​rinsed with river or lake water to remove dust and prevent initial turbidity increases. The matrix adsorption capacity is sampled every 12 months. If the TP (total phosphorus) adsorption rate drops below 20%, 10% new matrix is ​​added, slowly filling from the top to avoid disturbing the lower layers.

[0077] Specifically, biochar is made from corn cobs, with a specific surface area of ​​800 m² / g and a pH of 7.5, used to adsorb organic pollutants and improve conductivity. Aerated concrete blocks are made from recycled construction waste, with a particle size of 3-5 mm, a porosity of 70%, and a Ca²⁺ content. + The release rate is 50 mg / kg; used to release Ca²⁺. + It promotes TP (total phosphorus) precipitation and provides attachment sites for microorganisms. The raw material for the quartz sand is natural quartz sand with a particle size of 1-2 mm and a uniformity coefficient of <2. It is used as a subbase to prevent the loss of fine matrix.

[0078] In one embodiment, the anode assembly includes at least one anode plate 9 and a bracket for fixing the anode plate 9, the anode plate 9 being horizontally disposed within the deposit and the anode layer 5;

[0079] Among them, the anode plate 9 is made of biochar modified graphite felt. The modified raw material is biochar prepared from agricultural waste. After being calcined at 500℃ for 2 hours, it is crushed to a particle size of 1-2 mm and a specific surface area of ​​800 m² / g. The graphite felt is prepared by soaking in a 5% biochar suspension, taking it out and drying it at 80℃ for 2 hours. This process is repeated twice to ensure that the biochar is evenly attached to the surface of the graphite felt.

[0080] In this embodiment, the base material of the anode plate 9 is graphite felt with a size of 50cm×30cm×5mm, a porosity of 90%, a conductivity of 15S / m, good biocompatibility, and easy attachment of EAB (electrochemically active bacteria).

[0081] The biochar modification process involves preparing biochar from agricultural waste (corn cobs), calcining it at 500℃ for 2 hours, and then pulverizing it to a particle size of 1-2 mm, achieving a specific surface area of ​​800 m² / g to improve adsorption and conductivity. Graphite felt is then immersed in a 5% biochar suspension (biochar + deionized water, ultrasonically dispersed for 30 minutes), removed, and dried at 80℃ for 2 hours. This process is repeated twice to ensure uniform biochar adhesion to the graphite felt surface. This modification increases the amount of anode EAB adhesion while reducing internal resistance.

[0082] During installation, stainless steel brackets are used to fix the anode plate 9 in the middle of the sediment layer, 10cm from the functional matrix layer 4 and 20cm from the bottom support layer 6. The bracket spacing is 20cm to ensure that the anode plate 9 is in full contact with the sediment and to avoid being entangled by plant roots. Three sets of anode plates 9 are arranged in each module and connected in series by 1mm diameter titanium wires. The titanium wire joints are sealed with conductive silver glue to prevent corrosion and led out to the outside of the reactor to connect to the external circuit.

[0083] In one embodiment, the anode plate 9 has a plurality of planting holes for the roots of the submerged plant 11 to pass through, and the diameter of the planting holes is 0.8-1.2 cm.

[0084] The anode plate 9 is cut with circular planting holes, the diameter of which is slightly larger than the root diameter of the submerged plant seedling 11 (0.8-1.2cm) to ensure that the roots can pass through without being squeezed or damaged. The spacing between the holes matches a planting density of 30-40 plants / m² (each anode plate 9 contains 15-20 planting holes). The edges of the holes are sanded smooth with fine sandpaper to avoid sharp edges scratching the roots.

[0085] In one embodiment, the cathode 10 is a floating cathode 10, including a graphite felt substrate, a buoyancy block fixed to the upper part of the graphite felt substrate, and a connecting rope for suspension; the cathode 10 is configured to be suspended in the surface aeration conditioning layer 2 via the connecting rope.

[0086] In this embodiment, the cathode 10 is made of the same material as the anode plate 9 (graphite felt), and its dimensions are 50cm×20cm×5mm. It adopts a buoyancy-adjustable design. Three polyethylene buoyancy blocks (each with a buoyancy of 50g) are fixed on the top of the cathode 10 to adjust the depth of the cathode 10 immersed in the surface water. The default immersion depth is 50%, which can be adjusted by adding or removing buoyancy blocks to adapt to different DO (dissolved oxygen) requirements. The cathode 10 is suspended from the surface aeration adjustment layer 2 and fixed to the top flange of the modular reactor 1 by nylon ropes for easy disassembly and cleaning.

[0087] In one embodiment, the surface of the cathode 10 is coated with a composite catalyst layer of Fe3O4 and activated carbon;

[0088] Fe3O4 and activated carbon composite catalyst were mixed with polytetrafluoroethylene at a mass ratio of 9:1, and deionized water was added to form a paste. The paste was then evenly sprayed onto the surface of cathode 10 using a spray gun, with a coating thickness of 0.5 mm. The paste was then dried at 80°C for 1 hour.

[0089] This embodiment uses catalyst coating to improve electrochemical performance. The catalyst formulation is a composite catalyst of Fe3O4 and activated carbon.

[0090] Coating method: Mix the catalyst with polytetrafluoroethylene (PTFE, binder) at a mass ratio of 9:1, add a small amount of deionized water to make a paste, and spray it evenly on the surface of cathode 10 with a spray gun. The coating thickness is 0.5 mm. Dry at 80°C for 1 hour. This catalyst increases the oxygen reduction reaction rate of cathode 10 and does not require precious metals, which can reduce costs.

[0091] In one embodiment, the submerged plant 11 is selected from at least one of Potamogeton malaianus, Hydrilla verticillata, Vallisneria natans, Potamogeton pectinatus, Potamogeton crispus, or Myriophyllum spicatum; the planting density of the submerged plant 11 is 20-40 plants / m².

[0092] Alternatively, submerged plant 11 is *Potamogeton malaianus*, which has the following advantages: tolerance to heavy pollution: tolerant of NH4. +-N<15mg / L, COD (chemical oxygen demand)>80mg / L, survival rate in heavily polluted sediments of Taihu Lake is 103.7%-107.4%, significantly higher than other submerged plants; MFC (microbial fuel cell) synergy: short root system (8-10cm), non-woven fabric fixation does not interfere with anode plate 9, ROL (radial oxygen loss) is stable at 3.0-3.5μmolO2 / (h) compared to closely related species (Potamogeton). g); Purification capacity: The direct absorption of TN (total nitrogen) by the leaves is 2.1 g / (m²). d) TP is 0.8 g / (m²) d) It promotes a 2.3-fold increase in the abundance of EAB (electrochemically active bacteria) in the rhizosphere. It is suitable for heavily polluted rivers and lakes (COD 80-120 mg / L, TN 15-22 mg / L, TP 1.8-3 mg / L), such as black and odorous water bodies and rivers receiving dairy wastewater; it is also suitable for still water bodies or slightly flowing water bodies (flow velocity <0.3 m / s); the applicable climate is temperate to subtropical (10-30℃).

[0093] Optionally, submerged plant 11 is *Hydrilla verticillata*, which has a temperature tolerance range of 5-35℃, can germinate and grow in winter, and has a stable ROL of 2.37 μmol O2 / (h) in summer. g); Asexual propagation by cuttings or buds resulted in a survival rate >95%; In moderately polluted water bodies, the COD removal rate was 88%, TN was 72%, TP was 82%, TSS was 90%, and water transparency increased to 1.8m; and its root exudates (1.12mg / (d) g) Mainly composed of organic acids, it promotes the reduction of the internal resistance of anode plate 9 to below 300Ω. Suitable for lightly polluted rivers and lakes (COD 30-80mg / L, TN 9-15mg / L, TP 0.7-1.8mg / L); still water bodies or moderately flowing water bodies (flow velocity <0.5m / s); wide temperature range (5-35℃), suitable for both northern and southern regions.

[0094] Optionally, submerged plant 11 is *Potamogeton pectinatus*, widely distributed in the Yangtze and Yellow River basins. It is salt-tolerant (EC < 600 μS / cm) and tolerant of poor soil, requiring no introduction or domestication. The single-species COD removal rate is 85%, and ammonia nitrogen removal rate is 92%. When combined with *Potamogeton perforatum*, the TN removal rate reaches 90.3%. The clump-forming plants (20-30cm) only require harvesting the above-ground parts, without damaging the electrodes or substrate. It is suitable for moderately to heavily polluted rivers and lakes (COD 60-100 mg / L, TN 12-20 mg / L, TP 1.2-2.5 mg / L); still water bodies and slightly flowing water bodies; suitable for temperate to cold temperate zones (-5-30℃).

[0095] Optionally, submerged plant 11 is *Potamogeton crispus*, which grows vigorously in winter and spring (5-20℃) and has a radial oxygen loss (ROL) of 2.1 μmol O2 / (h). g) fills the gap in low-temperature microbial activity; winter bud sowing eliminates the need for seedling cultivation, reducing planting costs by 60% compared to seedling methods; tolerant of NH4 + -N <10mg / L, TP removal rate 87%, suitable for agricultural non-point source pollution. Applicable to moderately polluted water bodies (COD 50-80mg / L, TN 10-18mg / L, TP 1.0-2.0mg / L); still water bodies or slightly flowing water bodies (flow velocity <0.4m / s); suitable for winter and spring in the north or winter in the south.

[0096] Optionally, submerged plant 11 is *Myriophyllum spicatum*, which has the following effects on shock resistance and DO enhancement: ROL is 3.2 μmol O2 / (h). g), cathode DO increased to 4.5 mg / L, with a flow velocity <0.6 m / s; rhizosphere enrichment of Commonas, sulfamethoxazole removal rate 97.19%, Congo red decolorization rate 89.99%; combined with Potamogeton crispus, COD removal rate 95%, TN 90.3%. Suitable for heavily polluted flowing rivers (COD 80-150 mg / L, TN 15-25 mg / L, TP 2.0-3.0 mg / L); moderately flowing water bodies; suitable for tributaries of industrial wastewater containing antibiotics and dyes.

[0097] Planting and Fixing: Select healthy seedlings, 12-15cm tall, with well-developed root systems, and free from pests and diseases. Place the seedlings in river or lake water for hydroponics for 7 days, providing 300 lux of light and maintaining a temperature of 20-25℃. Change 1 / 3 of the water daily, discarding weak seedlings to ensure a survival rate >95% after transplanting. Use biochar-modified graphite felt, cutting circular planting holes slightly larger than the root diameter of the submerged plant seedlings (0.8-1.2cm) to ensure roots can pass through without being crushed or damaged. The hole spacing should match a planting density of 30-40 plants / m² (each anode plate contains 15-20 planting holes). Smooth the edges of the holes with fine sandpaper to avoid sharp edges scratching the roots. Fixed the anode plate 9 horizontally in the middle of the sediment layer, 20cm from the bottom support layer and 10cm from the functional matrix layer, ensuring the planting hole is vertically aligned with the sediment below. Holding the seedling, insert the roots vertically into the planting hole above the anode plate 9 until the root tips touch the sediment surface, with the roots protruding 5-6cm below the anode plate 9 to facilitate root establishment. Fill a small amount of functional matrix around the roots above the anode plate 9, compacting it to secure the seedling and prevent lodging. If the seedling is found to be tilting within 7 days after planting, it can be slightly adjusted and fixed by adding more matrix. As the roots grow naturally, they will penetrate the sediment (depth <5cm), but because the anode plate 9 is located in the middle of the sediment, the electrodes will not be pierced by the roots.

[0098] In one embodiment, the inlet 7 is connected to an annular perforated water distributor 12, which is located below the sediment and anode layer 5; the outlet 8 is located below the surface aeration regulating layer 2, and its inner side is provided with a nylon intercepting net and a microporous filter membrane in sequence.

[0099] The device employs a ring-shaped perforated water distributor 12, made of UPVC, with a hole diameter of 5mm and a hole spacing of 10cm. The holes face upwards to ensure that the incoming water is evenly distributed to the sediment layer, avoiding local water flow scouring that could cause anode displacement. It also prevents sediment particles from clogging the channels, allowing sewage to diffuse evenly upwards along the column wall. It is equipped with an adjustable-speed peristaltic pump, which can be adjusted according to the concentration of pollutants in the incoming water to adapt to fluctuations in river and lake water.

[0100] In one embodiment, the external circuit includes an adjustable resistor 13 and a data acquisition instrument;

[0101] The submerged plant type 11 microbial fuel cell ecological restoration system also includes auxiliary components, including at least one of the following: an aeration device installed on the surface aeration regulating layer 2, a plant supplemental lighting installed on the top of the modular reactor 1, and a heating rod installed on the sediment and anode layer 5.

[0102] The core components of the external circuit include an adjustable resistor 13, a data acquisition unit, and wires. The adjustable resistor 13 is a sliding rheostat (resistance range 0-2000Ω); the data acquisition unit automatically records voltage and current data every 10 minutes and can transmit it to a mobile APP via Bluetooth; the wires are waterproof copper core wires with an external PVC protective pipe to prevent water corrosion.

[0103] Closed circuit enriches EAB and iron-reducing bacteria: The closed circuit forms an electron flow, guiding EAB and iron-reducing bacteria to accumulate at the anode. Through Fe(III) reduction coupling, organic matter degradation is reduced, reducing competition from methanogens. Open circuit enriches growth-promoting bacteria. If only phytoremediation is needed (no need for electricity generation), the external circuit is disconnected, and the rhizosphere carbon source (plant secretions) is directionally enriched by microorganisms that produce growth-promoting substances and amino acids, promoting the absorption of nitrogen and phosphorus by plants. By adjusting the HRT (hydraulic retention time) and the substrate carbon-nitrogen ratio, the community balance is maintained, avoiding the overgrowth of a single microorganism and ensuring the synergistic effect of EAB-denitrifying bacteria-growth-promoting bacteria.

[0104] For cloudy weather scenarios, LED plant growth lights are installed on the top flange of modular reactor 1, providing 4 hours of supplemental lighting daily at a light intensity of 300 lux. Low-temperature temperature control: When winter temperatures drop below 10℃, an insulation film is wrapped around the outer wall of the reactor, and small heating rods are inserted into the sediment layer to ensure microbial activity and prevent inhibition of EAB metabolism. Electrode impedance is measured monthly using a digital multimeter. If the anode impedance is >500Ω, the electrode surface is rinsed with 0.1M HCl solution, soaked for 10 minutes, and then rinsed with clean water. Water quality testing: Influent and effluent COD, TN, and TP are sampled weekly using rapid test kits, and the HRT is adjusted based on the test results.

[0105] According to an embodiment of the present invention, another aspect provides a method for ecological restoration of submerged plant-based microbial fuel cells, comprising the following steps:

[0106] In the modular reactor 1, the bottom support layer 6, the sediment, and the sediment of the anode layer 5 are filled from bottom to top, and the anode assembly is installed; the functional matrix layer 4 is filled; the cathode 10 is installed and connected to the external circuit;

[0107] Select submerged plant seedlings 11, insert their roots through the planting holes of anode plate 9, so that the ends of the roots contact the surface of the sediment, and fill some functional matrix around the roots for fixation;

[0108] Introduce the river or lake water to be treated and adjust the hydraulic retention time; close the external circuit, adjust the resistance to 800-1200Ω, and start the microbial fuel cell;

[0109] Regularly monitor the output voltage, current, and effluent water quality, and adjust the hydraulic retention time or circuit status according to the water quality; regularly harvest the submerged plants 11 and replenish or replace the substrate of the functional substrate layer 4.

[0110] In one embodiment, during the steps of introducing river or lake water to be treated, adjusting the hydraulic residence time, closing the external circuit, adjusting the resistance to 800-1200Ω, and starting the microbial fuel cell, the external circuit is kept closed when the system aims to enhance pollutant removal and power generation; the external circuit is disconnected when the system aims to enhance plant absorption of nitrogen and phosphorus.

[0111] Specifically, the basic construction: prefabricate the modular reactor 1 according to the above dimensions, and pre-set sampling holes, electrode lead-out holes, and aeration pipe interfaces in the modular reactor 1; select the riverbank or the original area of ​​the polluted water body, level the ground and lay a 10cm thick concrete foundation to ensure that the modular reactor 1 is placed vertically.

[0112] Layered filling and component installation: Bottom support layer 6: First fill with 15cm of graded crushed stone, gently tap the column wall with a rubber mallet to compact it, then lay a PVC permeable partition, and seal the edges with waterproof glue; Sediment layer and anode: Fill with 30cm of in-situ river and lake sediment, compacting it while filling to avoid voids; Install 3 anode plates 9, ensuring that the anode plates 9 are horizontal, and the titanium wire leads out through the pre-set holes on the modular reactor 1; Functional matrix layer 4: First lay a 5cm quartz sand pad, then fill with biochar-ACB (aerated concrete block) mixed matrix in layers, and make the surface smooth after filling; Cathode 10 and aeration system: Suspend cathode 10 directly above each anode; Install aeration pipes and test the aeration uniformity; Inlet and outlet water system: Install the annular perforated water distributor 12 and the inlet pipe, the outlet 8 and the outlet pipe, and test the pipeline sealing with a pressure pump.

[0113] Planting of submerged plants: Select healthy seedlings, rinse the roots with deionized water to remove mud and sand, and preserve the integrity of the fibrous roots; insert the seedling roots vertically into the planting hole of anode plate 9, with the roots protruding 5-6cm below anode plate 9; fill the area around the roots above anode plate 9 with 50mL of biochar-ACB mixed substrate, and compact it to fix the roots.

[0114] System commissioning and operation: Commissioning phase: Slowly introduce raw river and lake water to avoid water flow impacting the seedlings, turn on the aeration system (intermittent aeration), and monitor the DO concentration in the cathode area; close the circuit, adjust the resistance to 1000Ω, and record the initial voltage; Stable operation phase: Adjust the hydraulic retention time according to the degree of pollution, replace the PVDF filter membrane at the outlet every 15 days; backwash the water distributor every 30 days; Abnormal handling: If the voltage drops suddenly (<0.2V), check whether the electrode connection is loose or whether the roots are tangled; if the effluent turbidity is >5NTU, replace the nylon mesh and filter membrane in time.

[0115] This technical solution controls costs across the entire chain, from material selection and structural design to operation and maintenance processes, thus meeting the practical needs of "low cost and wide coverage" in river and lake management.

[0116] 1. Low material cost and weather resistance: The main body of the modular reactor 1 is made of glass fiber reinforced plastic, and the electrodes are made of graphite felt modified with corn cob biochar to replace precious metal catalysts; the functional matrix is ​​mainly biochar from construction waste and agricultural waste, which reduces raw material costs.

[0117] 2. Low operating energy consumption: No artificial aeration is required (oxygen is supplemented by ROL of submerged plants) and no external carbon source is required (carbon is supplied by root exudates), resulting in low daily energy consumption per module.

[0118] 3. Simple maintenance and operation: Monthly maintenance requires testing electrode impedance and sampling to monitor water quality, annual replenishment of functional substrate and regular harvesting of submerged plants; the installation adopts modular flange splicing, which does not require large equipment.

[0119] This technical solution addresses the complex pollution characteristics of rivers and lakes, characterized by high nitrogen and phosphorus levels, high COD, low transparency, and the presence of recalcitrant organic matter, and solves the problems of existing technologies' single-method and fluctuating pollution levels.

[0120] 1. Simultaneous removal of multiple pollutants: COD is removed through EAB oxidation and matrix adsorption, TN is removed through nitrification-denitrification and plant absorption, and TP is removed through adsorption, precipitation and plant absorption. In addition, some recalcitrant organic pollutants can be removed through EAB co-metabolism and biochar adsorption.

[0121] 2. Strong performance stability: It adapts to environmental fluctuations through adjustable water intake speed, heat preservation and temperature control, and impedance monitoring. When the temperature is low, the heat preservation membrane and heating rod are activated to maintain the activity of microorganisms. When the COD of the influent fluctuates greatly, the flow rate is adjusted by the peristaltic pump to ensure that the decontamination efficiency fluctuates within the normal range.

[0122] This technical solution avoids the secondary pollution risks of traditional treatment technologies throughout the entire process, while reducing greenhouse gas emissions, and complies with current ecological and environmental protection policies.

[0123] 1. No risk of secondary pollution: The electrodes and substrate are made of materials free of heavy metals to avoid the problem of heavy metal leaching; the submerged plants are harvested regularly and then crushed and composted to prevent the decay of fallen materials from increasing the organic matter in the water.

[0124] 2. Significant greenhouse gas emission reduction: The anode EAB competes for organic substrates, inhibiting methanogenic bacteria activity and reducing CH4 emissions compared to CW alone; submerged plants 11 optimize the nitrification-denitrification balance, reducing N2O accumulation. Submerged plants 11 increase DO, promote the enrichment of carbon pumping microorganisms, synthesize recalcitrant organic carbon, and reduce CO2 regeneration.

[0125] This technical solution adopts a modular design, which can be expanded as needed according to the area of ​​river and lake pollution and the treatment capacity, thus solving the problem of fixed scale and difficulty in adjustment of traditional technologies.

[0126] 1. Flexible modular design: Each module has a processing capacity of 500-800L / d. Multiple modules can be combined by connecting them in parallel via flanges, making it suitable for different scenarios such as small landscape lakes and medium-sized river tributaries.

[0127] 2. Dual modes: In-situ or side-by-side: The module can be directly deployed to polluted river and lake areas for in-situ remediation, or it can be built on the shore and water can be drawn through pipelines for side-by-side remediation. It is suitable for areas with severe pollution that require centralized treatment. Neither mode requires large-scale modification of the existing water structure.

[0128] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A submerged plant-based microbial fuel cell ecological restoration system, characterized in that, It includes a modular reactor (1), which is a vertically arranged columnar structure. Its inner cavity is divided into a surface aeration and regulation layer (2), a submerged plant growth layer (3), a functional matrix layer (4), a sediment and anode layer (5), and a bottom support layer (6) from top to bottom. An anode assembly is provided in the sediment and anode layer (5), and a cathode (10) is provided in the surface aeration regulating layer (2). The anode assembly and the cathode (10) are connected by an external circuit. Submerged plants (11) are planted in the submerged plant growth layer (3). The roots of the submerged plants (11) penetrate the functional matrix layer (4) and extend to the upper part of the sediment and anode layer (5). The modular reactor (1) has an inlet (7) on the lower side wall and an outlet (8) on the upper side wall. The anode assembly, cathode (10), external circuit, and submerged plant (11) constitute a microbial fuel cell. The functional matrix layer (4) is made of biochar and aerated concrete blocks mixed in a volume ratio of 1:1 to 1:

3. The raw material of the biochar is corn cob with a particle size of 2-5 mm and a specific surface area of ​​≥800 m² / g. The particle size of the aerated concrete blocks is 3-5 mm. A quartz sand pad with a thickness of 3-5 cm is laid at the bottom of the functional matrix layer (4). The anode assembly includes at least one anode plate (9) and a bracket for fixing the anode plate (9), the anode plate (9) being horizontally disposed within the deposit and anode layer (5); The anode plate (9) is made of biochar modified graphite felt. The modified raw material is biochar prepared from agricultural waste. After being roasted at 500℃ for 2 hours, it is crushed to a particle size of 1-2 mm and a specific surface area of ​​800 m² / g. The graphite felt is prepared by soaking in 5% biochar suspension, taking it out and drying it at 80℃ for 2 hours. This process is repeated twice to ensure that the biochar is evenly attached to the surface of the graphite felt. The cathode (10) is a floating cathode, which includes a graphite felt substrate, a buoyancy block fixed to the upper part of the graphite felt substrate, and a connecting rope for suspension. The cathode (10) is configured to be suspended in the surface aeration conditioning layer (2) via the connecting rope; The surface of the cathode (10) is coated with a composite catalyst layer of Fe3O4 and activated carbon; In this process, Fe3O4 and activated carbon composite catalyst are mixed with polytetrafluoroethylene at a mass ratio of 9:1, deionized water is added to form a paste, and the paste is uniformly sprayed onto the cathode (10) surface with a spray gun. The coating thickness is 0.5 mm, and the paste is dried at 80°C for 1 h.

2. The submerged plant-based microbial fuel cell ecological restoration system according to claim 1, characterized in that, The anode plate (9) has multiple planting holes for the roots of submerged plants (11) to pass through, and the diameter of the planting holes is 0.8-1.2 cm.

3. The submerged plant-based microbial fuel cell ecological restoration system according to claim 1, characterized in that, The submerged plant (11) is selected from at least one of the following: Potamogeton malaianus, Hydrilla verticillata, Vallisneria natans, Potamogeton pectinatus, Potamogeton crispus, or Myriophyllum spicatum; the planting density of the submerged plant (11) is 20-40 plants / m².

4. The submerged plant-based microbial fuel cell ecological restoration system according to claim 1, characterized in that, The inlet (7) is connected to an annular perforated water distributor (12), which is located below the sediment and anode layer (5); the outlet (8) is located below the surface aeration regulating layer (2), and its inner side is provided with a nylon intercepting net and a microporous filter membrane in sequence.

5. The submerged plant-based microbial fuel cell ecological restoration system according to claim 1, characterized in that, The external circuit includes an adjustable resistor (13) and a data acquisition instrument; It also includes auxiliary components, which include at least one of the following: an aeration device disposed on the surface aeration conditioning layer (2), a plant supplement lamp disposed on the top of the modular reactor (1), and a heating rod disposed on the sediment and anode layer (5).

6. A method for ecological restoration of submerged plant-based microbial fuel cells, employing the submerged plant-based microbial fuel cell ecological restoration system according to any one of claims 1-5, characterized in that, Includes the following steps: In the modular reactor (1), the bottom support layer (6), sediment and the sediment of the anode layer (5) are filled from bottom to top, and the anode assembly is installed; the functional matrix layer (4) is filled; the cathode (10) is installed and connected to the external circuit; Select submerged plant (11) seedlings, insert their roots through the planting holes of the anode plate (9) of the anode assembly, so that the ends of the roots contact the surface of the sediment, and fill part of the functional matrix around the roots for fixation; Introduce the river or lake water to be treated and adjust the hydraulic retention time; close the external circuit, adjust the resistance to 800-1200Ω, and start the microbial fuel cell; Regularly monitor the output voltage, current and outflow water quality, and adjust the hydraulic retention time or circuit status according to the water quality; regularly harvest the submerged plants (11) and replenish or replace the substrate of the functional substrate layer (4).

7. The method for ecological restoration of submerged plant-based microbial fuel cells according to claim 6, characterized in that, In the steps of introducing river and lake water to be treated, adjusting the hydraulic residence time, closing the external circuit, adjusting the resistance to 800-1200Ω, and starting the microbial fuel cell, the external circuit is kept closed when the system aims to enhance pollutant removal and power generation; the external circuit is disconnected when the system aims to enhance plant absorption of nitrogen and phosphorus.

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