A method and device for in-situ remediation of black and odorous water bodies using microbial fuel cells-aquatic plants

Abstract

The present invention discloses a method and device for in-situ remediation of black and odorous water bodies by using a microbial fuel cell-aquatic plant. The steps are as follows: A. Bury an anode plate at a position below the sediment-water interface of the black and odorous water body; B. Pass the roots of the aquatic plants through the circular holes on the anode plate and root them in the sediment; C. Set a cathode plate at the water-air interface so that the cathode plate floats in the water surface and the cathode plate is exposed to the air; D. Connect the anode plate and the cathode plate with an external wire and an external resistor to form a current loop. The anode plate is located below the sediment-water interface. There are circular openings arranged in an equidistant array on the anode plate. The roots of the aquatic plants pass through the openings of the anode plate and penetrate into the sediment. The cathode plate floats at the overlying water-air interface. The anode plate and the cathode are connected in sequence through an external wire and an external resistor to form a current path. The method is simple, the operation is convenient, the structure is simple, which promotes the absorption of nutrients by aquatic plants, converts them into plant biomass, and improves the black and odorous and eutrophic state of the water body.

Description

Technical Field

[0001] The present invention belongs to the technical field of ecological restoration of water bodies such as lakes, rivers, and ditches, and more specifically relates to a method for synergistically treating and in-situ repairing black and odorous water bodies by using sediment fuel cells-aquatic plants, and also relates to a device for in-situ repairing black and odorous water bodies by combining aquatic plants and microbial fuel cells. Background Art

[0002] The black and odorous state of water bodies is an extreme phenomenon of water body organic pollution and a description of the extremely polluted state of water bodies. The so-called "black and odorous" means that, visually, the water body presents an unpleasant color (black or dark black) and / or emits an unpleasant odor (such as irritating gases like H2S and NH3); in terms of the formation mechanism, the blackening and stinking of water bodies are mainly the result of a series of physical, chemical, and biological actions of organic pollutants in the water body under anaerobic or anoxic conditions. The judgment of the black and odorous degree can be based on four indicators: transparency, dissolved oxygen, oxidation-reduction potential, and ammonia nitrogen (Guidelines for the Remediation of Urban Black and Odorous Water Bodies). Generally speaking, when the DO in the water body ≤ 2 mg·L －1 、ORP < -100 mg·L －1 、NH4 + -N ≥ 8 mg·L －1 ,the water body begins to turn black and odorous; when ORP < -200 mg·L －1 ,it is in a severely black and odorous state (Cheng Jiang et al., Research on Key Indicators for Predicting and Evaluating the Black and Odorous State of Water Bodies in Plain River Network Areas, China Water & Wastewater, 2006, 22(9): 18-22; Lv Jiajia et al., Research on Water Quality and Environmental Conditions for the Formation of Black and Odorous Water, Journal of East China Normal University: Natural Science Edition, 2014, 48(5): 711-716).

[0003] The inflow of exogenous organic pollutants (mainly including organic carbon pollution sources, organic nitrogen pollutants, and phosphorus-containing compounds) is one of the main reasons for the black and odorous phenomenon of water bodies. These pollutants mainly come from the decomposition of organic substances such as sugars, proteins, amino acids, and oils in wastewater and sewage. During the decomposition process, a large amount of dissolved oxygen is consumed, making the oxygen consumption rate in the water body > the reoxygenation rate, resulting in anoxic water bodies. In anoxic water bodies, the odor-producing process will be synchronized with blackening. Anaerobic decomposition of organic matter produces small molecular compounds with peculiar smells and easy volatility such as methane (CH4), hydrogen sulfide (H2S), and ammonia (NH3), which overflow into the atmosphere above the water surface, thus emitting a stench. Part of the unoxidized and unassimilated H2S forms black sediment FeS with Fe 2+ etc. in the water body. Tiny suspended substances in the water body will adsorb part of the FeS, and some of the FeS sediments deposited at the bottom of the water will re-enter the water body under the buoyancy of gases or bubbles produced by anaerobic decomposition. Coupled with the synergistic effect of other factors, the water body presents a black color.

[0004] On the premise of controlling the input of exogenous pollution, the release of endogenous pollutants caused by sediment resuspension has become the most important factor leading to the blackening and odorization of water bodies. Under the influence of hydraulic scouring, human disturbance, and biological activities, the sediment undergoes resuspension. Humic acid and fulvic acid in the suspended particles become the main blackening compounds due to the adsorption and complexation of Fe, Mn, and S compounds. At the same time, the pollutants adsorbed on the sediment particles exchange with the pore water, releasing pollutants into the water body, resulting in the blackening and odorization of the water body.

[0005] The commonly used in-situ treatment technologies in engineering mainly include three categories: physical remediation, chemical remediation, and biological remediation. Physical remediation measures use means such as sediment dredging, in-situ covering, and aeration to change the physical properties of the sediment; chemical remediation is to add chemical agents (such as ferric chloride, calcium salts, CaO, CaO2, Ca(NO3)2, and NaNO3, etc.) to the polluted sediment, enabling them to undergo oxidation-reduction, precipitation, polymerization, and other reactions with the pollutants, separating the pollutants from the sediment, or degrading and transforming them into low-toxic or non-toxic chemical forms. The main chemical methods include oxidation-reduction method, wet oxidation method, chemical dechlorination method, chemical leaching method, polymerization, complexation, hydrolysis, and pH adjustment (Annet al., 1999; Chen et al., 2016). Although physical and chemical methods are effective quickly, either they have a large amount of work and high costs, or it is difficult to maintain stably in the long term, and they are not the most ideal methods (Zhong et al., 2008; Palermo, 1998; Lin Jianwei et al., 2005).

[0006] Compared with other remediation technologies, biological remediation has the advantages of low cost, high decontamination rate, and long-lasting effect, mainly including phytoremediation, microbial remediation, etc. Microbial remediation mainly refers to the application of microbial inoculants. The dominant populations in the microbial inoculants inhibit harmful bacteria and harmful algae in the water body through benign competition, nutrient competition, living environment competition, etc., as well as proteases and bioenzymes secreted by specific bacterial communities. At the same time, they decompose organic compounds in the water body to maintain a good microecological balance. Although single microbial remediation has good effects, it requires multiple repeated additions, a large dosage, and correspondingly high costs.

[0007] Aquatic plant remediation utilizes the ability of submerged plants to act on the dynamic balance of nitrogen and phosphorus at the "sediment-water" interface during their growth process in the following ways: 1) Absorbing inorganic nitrogen and inorganic phosphorus in the overlying water, interstitial water, and sediment; 2) Directly and indirectly influencing the activity of alkaline phosphatase (APA); 3) Altering water dynamics, as well as the dissolved oxygen, pH, oxidation-reduction potential, etc. in the overlying water body and sediment, thereby affecting the content and existing forms of various forms of nitrogen and phosphorus in the water body and sediment. Using aquatic plants to remediate water body and sediment pollution is one of the important sustainable methods to eliminate black odor and inhibit the outbreak of water blooms. It once served as a magic weapon and became a synonym for water body ecological restoration. However, some unsuitable habitats such as too deep water level, too strong wind and waves, anaerobic bottom sediment, too hard bottom sediment, too high nitrogen and phosphorus concentration, too low water transparency, etc. often become obstacles to the initial restoration of submerged plants in practice. Therefore, it is necessary to use other technical methods to improve or create habitats suitable for the initial restoration of submerged plants, so that aquatic plants can quickly colonize and form a certain amount of biomass.

[0008] Sediment Microbial Fuel Cell (SMFC) is an in-situ remediation technology that can degrade organic pollutants in sediment, remove nitrogen and phosphorus. It repairs by electrogenic microorganisms attaching to the anode surface to form a conductive biofilm and using the organic matter in the sediment as a metabolic substrate. SMFC can significantly increase the oxidation-reduction potential of the sediment and improve the anaerobic condition of the sediment.

[0009] Coupling SMFC and aquatic plants, the coupling system can overcome the defects of single SMFC being affected by the acidification of the electrogenic anode and the alkalization of the cathode area, as well as the difficulty for submerged plants to form a certain amount of biomass in the initial stage and the secondary pollution caused by the residues after decay in the later stage. This makes it possible to achieve sustainable, low-cost, in-situ remediation of black-odorous rivers. Summary of the Invention

[0010] The purpose of the present invention is to provide a method for jointly in-situ remediating black-odorous water bodies by submerged plants and microbial fuel cells. The method is simple and easy to implement, convenient to operate, and in-situ utilizes the electrons generated by the anode and the oxygen released by the roots to improve the oxidation-reduction environment of the sediment, so that the substances causing black odor in the sediment are oxidized. Through the power generation process, it promotes the absorption of nutrients by aquatic plants, which are transformed into plant biomass, improving the black odor and eutrophication of the water body.

[0011] Another purpose of the present invention is to provide a device for jointly in-situ remediating black-odorous water bodies by aquatic plants and microbial fuel cells. The structure is simple, easy to assemble, and has good use effects, which can significantly eliminate the black odor of the water body.

[0012] In order to achieve the above purposes, the present invention adopts the following technical measures:

[0013] Through the effective synergy of microbial fuel cells and aquatic plants, the redox potential of the sediment is increased, and the black (FeS) and odor (CH4, H2S, NH3) substances in the sediment are oxidized to eliminate the black and odorous water. During the power generation process, the electrogenic bacteria enriched in the anode area and the bacteria enriched in the root area of ​​the aquatic plants form a more powerful and more stable microbial community, which promotes the growth and reproduction of submerged plants and sustainably repairs black and odorous water bodies.

[0014] Technical solution: Anode plates are buried in the bottom mud of black and smelly water bodies, and the roots of aquatic plants are rooted in the bottom mud through the holes on the anode plates. A cathode plate is set on the water-air surface, and anodes, external resistors and cathodes are connected in sequence with wires to form a microbial fuel cell aquatic plant coupling system configuration. Further, the redox environment of the bottom mud is changed to avoid the anaerobic decomposition of organic matter in the bottom mud to release odorous substances, and FeS that causes the water to turn black is also reduced by Fe 2+ Oxidized to Fe 3+ The functional bacteria enriched in the corresponding anode area and the rhizosphere of aquatic plants no longer exist, which promotes the growth of plants and is beneficial to the recovery of aquatic vegetation.

[0015] A method for in-situ restoration of black and smelly water bodies using microbial fuel cells-aquatic plants, the steps of which are as follows:

[0016] A. Bury the anode plate 3-10cm below the mud-water interface in the black and smelly water body;

[0017] B. Let the roots of aquatic plants pass through the round holes on the anode plate and take root in the bottom mud;

[0018] C. Set the cathode plate at the water-air interface so that the cathode plate is suspended in the water surface and 30%-70% of the cathode plate area is exposed to the air;

[0019] D. Connect the anode plate and cathode plate with external wires and external resistors to form a current loop. A large number of electrogenic bacteria and iron redox bacteria gradually accumulate near the anode (any distance within 10 cm), which can promote the redox cycle of iron, facilitate the degradation of macromolecular organic matter in black and smelly sludge into small molecular organic acids, and the complete oxidation of small molecular organic acids.

[0020] The aquatic plants include submerged plants and emergent plants.

[0021] The submerged plants are one of Vallisneria, Dermatophyte, Foxtail Algae, Hydrilla, Water Chestnut, Sea Lettuce, Potamogeton crenata, etc., or any combination of one to seven of the above.

[0022] The emergent plants are one of iris, wild rice stem, calamus, cattail, lily of the valley, windmill grass, etc., or any combination of one to six of them.

[0023] The anode plate materials described above include any one of graphite felt, graphite plate, carbon felt, stainless steel plate, stainless steel mesh, etc.

[0024] The cathode plate materials described above include any one of graphite felt sheets, carbon felt sheets, etc.

[0025] The wire is a copper wire or a titanium wire.

[0026] The external resistance is an adjustable resistor or a fixed resistance resistor or an electrical appliance with a resistance value of 50 - 2000 ohms.

[0027] Among the technical measures of the above four steps, the key ones are steps A and B. In step A, the anode plate is set at 3 - 10 cm below the sediment - water interface. This is because the black and odorous substances in the sediment generally accumulate in the middle and upper layers, and the redox potential in this part is relatively low. Setting the anode plate within this depth range is conducive to improving the redox conditions in this area. At the same time, this depth range is also the depth range where the root zones of aquatic plants are located, which is conducive to the synergy between the electricity - generating effect and the root zone effect of plants. In step B, the roots of aquatic plants need to pass through the round holes on the anode plate and take root in the sediment because when the anode is close to the root system, it can better enrich electrogenic bacteria with stable structures, iron - redox functional bacteria, etc. In step C, 30% - 70% of the cathode plate area is exposed to the air to form a bio - cathode where both oxygen (O2) and nitrate nitrogen (NO3 - ) act as electron acceptors. A higher electricity - generating efficiency is conducive to the enrichment of electrogenic bacteria. At the same time, when nitrate is used as an electron acceptor, it is conducive to being transformed into N2 and removed from the water body.

[0028] After the above - mentioned method steps, the redox potential in the sediment will increase due to the oxygen release from plant roots, the electricity generation by electrogenic bacteria, and electron transfer, causing the black and odorous sediment to change from the reduced state to the oxidized state. The concentration of NH4 in the black and odorous water body + -N is controlled below 1 mg·L －1 and the transparency increases by 30 - 50 cm, which is conducive to the initial recovery of submerged plants.

[0029] A device for in - situ remediation of black and odorous water bodies using a microbial fuel cell - aquatic plants. The device consists of a sediment layer, an anode plate, aquatic plants, an overlying water layer, a cathode plate, an external wire, and an external resistance from bottom to top. It is characterized in that: the anode plate is located 3 - 10 cm below the sediment - water interface, and there are circular openings with a diameter of 8 - 15 cm arranged in an equidistant array on the anode plate. The roots of the aquatic plants pass through the openings of the anode plate and penetrate into the sediment. The cathode plate is suspended at the overlying water - air interface, and 30% - 70% of its area is exposed to the air. The anode plate and the cathode are connected in sequence through an external wire and an external resistance (or an electrical appliance) to form an electric current path.

[0030] The thickness of the sediment layer is 10 - 35 cm.

[0031] The aquatic plants described above can be submerged plants. The submerged plants include one or any combination of one to seven of Vallisneria natans, Ceratophyllum demersum, Myriophyllum verticillatum, Hydrilla verticillata, Potamogeton crispus, Ottelia acuminata, Potamogeton pectinatus, etc.

[0032] The emergent plants described above include one or any combination of one to six of Iris tectorum, Zizania latifolia, Acorus calamus, Typha orientalis, Thalia dealbata, Cyperus alternifolius, etc.

[0033] The anode plate is a square electrode plate with circular openings with a diameter of 5 - 10 cm arranged in an equidistant array, facilitating the perforation and insertion of bundled aquatic plants into the sediment layer.

[0034] The materials of the anode plate include any one of graphite felt, graphite plate, carbon felt, stainless steel plate, stainless steel mesh, etc.

[0035] The cathode plate is composed of 6 - 12 small pieces of electrode materials connected by cathode plate connecting wires. In order to ensure a certain area is exposed to the air, and at the same time, the connection of several small pieces will not block sunlight and affect the photosynthesis of plants.

[0036] The materials of the cathode plate include any one of graphite felt sheets, carbon felt sheets, etc.

[0037] The wire is a copper wire or a titanium wire.

[0038] The external resistance is an adjustable resistor or a fixed - value resistor with a resistance of 50 - 2000 ohms.

[0039] The height of the overlying water layer is 50 - 100 cm.

[0040] The most crucial part of the above - mentioned device is the burial position of the anode plate and the rooting of aquatic plants through the round holes on the cathode plate into the sediment. The anode plate needs to be at 3 - 10 cm below the sediment - water interface and near the roots of submerged plants to better utilize the synergistic effect of anode - producing bacteria and the roots of submerged plants, promote the enrichment of more abundant and more stable electrogenic and iron - redox functional microbial communities in the root zone and anode, increase the sediment redox potential, improve the water transparency, and promote the initial growth recovery of aquatic plants.

[0041] After using this device, NH4 in the overlying water layer +The content decreased by more than 85%, the biomass of aquatic plants increased by more than 50%, and there were iron bacteria such as Gallionella (abundance 0.2%) and iron-reducing bacteria such as Geobacter (abundance 10.4%) and Bacillus (abundance 4.4%) on the anode, which significantly promoted the iron redox cycle process, facilitated the degradation of macromolecular organic matter in the black and odorous sediment into small molecule organic acids, and the complete oxidation of small molecule organic acids without consuming dissolved oxygen in the water body.

[0042] Compared with the existing technology, the present invention has the following advantages and effects:

[0043] 1. By simply planting aquatic plants, burying electrodes and connecting wires in the black and odorous water body, the present invention uses the electricity generation at the anode, the migration of electrons in the external circuit, and the oxygen release from the roots of aquatic plants to increase the redox potential of the sediment, in-situ improving the redox environment of the bottom of the black and odorous water body, which can be transformed from the reduced state to the oxidized state, facilitating the mineralization of sediment organic matter and the oxidation of reducing substances such as blackening and odor-causing substances in the sediment and water body, thus eliminating the blackening and odor.

[0044] 2. In the present invention, the microbial fuel cell-aquatic plant coupling system repairs the black and odorous water body in-situ. Compared with a single sediment microbial fuel cell system or a single aquatic plant planting, the electricity generation process of microorganisms and aquatic plants promote each other synergistically, enabling a higher abundance of functional bacteria such as electricity generation, phosphorus removal and nitrogen removal to be enriched in the anode and plant root zones. At the same time, it promotes the absorption of nutrients in the water body and sediment by plants, promotes the growth of plants, and accelerates the repair of the black and odorous water body. Description of the Drawings

[0045] Figure 1 It is a schematic diagram of a method and device for in-situ repairing a black and odorous water body using a sediment microbial fuel cell-aquatic plant.

[0046] Figure 2 It is a schematic diagram of the anode plate with holes.

[0047] Figure 3 It is a schematic diagram of the cathode plate connection.

[0048] In the figure: 1 - sediment layer; 2 - anode plate; 3 - aquatic plant; 4 - overlying water layer; 5 - cathode plate; 6 - external wire; 7 - external resistance (ordinary, purchased on the market); 8 - hole; 9 - cathode plate connection wire. Detailed Embodiments

[0049] The following combines the attached Figures 1-3 The specific embodiments of the invention are explained and described, which do not constitute a limitation to the present invention.

[0050] Example 1:

[0051] A method for in-situ remediation of black and odorous water bodies using a microbial fuel cell-aquatic plant, comprising the following steps:

[0052] A. Install an anode plate at a depth of 3 or 5 or 8 or 10 cm below the sediment-water interface of the black and odorous water body; this setting is because the black and odorous substances in the sediment generally accumulate in the middle and upper layers, and the redox potential in this part is relatively low. Installing the anode plate within this depth range is conducive to improving the redox conditions in this area. At the same time, this depth range is also the depth range where the root zone of aquatic plants is located, which is conducive to the synergy of electricity generation and the root zone of plants.

[0053] B. Pass the roots of the aquatic plants through the round holes on the anode plate and root them in the sediment, and utilize the synergistic effect of the plant roots and the anode electricity-producing bacterial community to promote the better enrichment of structurally stable electricity-producing bacterial communities, iron redox functional bacterial communities, etc.

[0054] C. Install a cathode plate at the water-air interface so that the cathode plate floats in the water surface, and 30%-70% of its area must be exposed to the air to form an air-biological cathode. Using oxygen (chemical formula: O2) as an electron acceptor can maintain a high electricity generation efficiency and promote the enrichment of electricity-producing bacterial communities. At the same time, nitrate (NO3 - ) in the water body can also be used as an electron acceptor, so that NO3 - is converted into N2 and removed from the water body, and it also promotes the ammonia oxidation reaction of more ammonia nitrogen (NH4 + ) in the water body and is removed from the overlying water.

[0055] D. Connect the anode plate and the cathode plate with an external wire and an external resistor to form an electric current loop. A large number of electricity-producing bacterial communities and iron redox bacterial communities, etc. gradually accumulate near the anode (any distance within 10 cm is acceptable), which can promote the iron redox cycle process, degrade macromolecular organic matter in the black and odorous sediment into small molecule organic acids, and completely oxidize the small molecule organic acids.

[0056] The aquatic plants described above include submerged plants. The submerged plants are one or any combination of one to seven of Vallisneria natans, Ceratophyllum demersum, Myriophyllum verticillatum, Hydrilla verticillata, Potamogeton crispus, Ottelia acuminata, Potamogeton pectinatus, etc.

[0057] The emergent plants are one or any combination of one to six of Iris tectorum, Zizania latifolia, Acorus calamus, Typha orientalis, Thalia dealbata, Cyperus alternifolius, etc.

[0058] The anode plate materials include any one of graphite felt, graphite plate, carbon felt, stainless steel plate, stainless steel mesh, etc.

[0059] The cathode plate materials include any one of graphite felt sheets, carbon felt sheets, etc.

[0060] The wire described above is a copper wire or a titanium wire.

[0061] The external resistor described above is a variable resistor with a resistance value of 50 - 2000 ohms, a fixed - value resistor, or an electrical appliance.

[0062] The experimental results show that: after adopting this method, the average redox potential of the sediment layer increases by more than 500 mV, changing from the reduced state to the oxidized state. The concentration of NH4 + -N in the black - smelly water body is below 1 mg·L －1 and the transparency increases.

[0063] Example 2:

[0064] A device for in - situ remediation of black - smelly water bodies by combining a microbial fuel cell and aquatic plants. The device is laid from bottom to top with a sediment layer 1, an anode plate 2, aquatic plants 3, an overlying water layer 4, a cathode plate 5, an external wire 6, and an external resistor 7. It is characterized in that: the anode plate 2 is located under the surface layer of the sediment layer 1, with a depth of 3 or 5 or 8 or 10 cm. The roots of the aquatic plants 3 pass through the openings 8 of the anode plate 2 and penetrate into the sediment layer 1. The cathode plate 5 is suspended in the overlying water layer 4 and is partially exposed (any area within the range of 30% - 70% is acceptable) in the air. One end of the external wire 6 is connected to the anode plate 2, the other end of the external wire 6 is connected to the external resistor 7, and the external resistor 7 is respectively connected to the external wire 6 and the cathode plate 5 to form an electric current path. A large number of electricity - generating bacterial communities and iron redox bacterial communities gradually accumulate near the anode, which can promote the iron redox cycle process, enabling the degradation of macromolecular organic matter in the black - smelly sediment into small - molecule organic acids, and the complete oxidation of small - molecule organic acids.

[0065] The thickness of the sediment layer 1 is 10 or 18 or 22 or 30 or 35 cm, and it is the sediment in water bodies such as black - smelly lakes, rivers, and ditches.

[0066] The aquatic plants 3 described above can be submerged plants and emergent plants. The submerged plants include one or any combination of one to seven of Vallisneria natans, Ceratophyllum demersum, Myriophyllum verticillatum, Hydrilla verticillata, Potamogeton crispus, Ottelia acuminata, Potamogeton pectinatus, etc.

[0067] The emergent plants include one or any combination of one to six of Iris tectorum, Zizania latifolia, Acorus calamus, Typha orientalis, Thalia dealbata, Cyperus alternifolius, etc.

[0068] The anode plate 1 is a square electrode plate with circular openings 8 arranged in an equidistant array, with a diameter of 5 or 7 or 8.5 or 10 cm, facilitating the insertion of bundled aquatic plants through the holes into the sediment layer 1.

[0069] The materials of the anode plate 1 include any one of graphite felt, graphite plate, carbon felt, stainless - steel plate, stainless - steel mesh, etc.

[0070] The cathode plate 5 described above is formed by connecting 6 or 7 or 8 or 9 or 10 or 11 or 12 (or more) small pieces of electrode material with a cathode plate connecting wire 9. In order to ensure a certain area is exposed to the air, and at the same time, the connection of several small pieces will not block sunlight and affect the photosynthesis of plants.

[0071] The material of the cathode plate 5 described above includes any one of graphite felt sheets, carbon felt sheets, etc.

[0072] The external wire 6 is a copper wire or a titanium wire.

[0073] The external resistor 7 is an adjustable resistor with a resistance value of 50 - 2000 ohms, a fixed-resistance resistor, or an electrical appliance.

[0074] The height of the overlying water layer is 50 - 100 cm.

[0075] Experimental results show that: after the device in the present invention operates for a period of time, the concentration of NH4 + -N in the original black and odorous water body drops from 5 mg / L to 0.8 mg·L －1 , Eh rises from -411 mV to 140 mV, and the transparency rises from 30 cm to 50 cm.

[0076] Example 3:

[0077] The experiment compared the remediation effects of the MFC - Vallisneria system and the single - planted Vallisneria system on black and odorous water bodies under the same environmental conditions. The results showed that: the biomass of Vallisneria in the MFC - coupled system increased by 30 - 50%; there were iron bacteria such as Gallionella (abundance 0.2%) and iron - reducing bacteria such as Geobacter (abundance 10.4%) and Bacillus (abundance 4.4%) in the anode, which could promote the iron oxidation - reduction cycle process, facilitate the degradation of macromolecular organic matter in black and odorous sediment into small - molecule organic acids, and the complete oxidation of small - molecule organic acids, without consuming more dissolved oxygen in the water body.

[0078] Its implementation steps and structure are the same as those of Example 1 and Example 2.

Claims

1. A method for in-situ remediation of black and odorous water bodies using a microbial fuel cell-aquatic plant, the steps of which are as follows: A. Bury the anode plate (2) 3-10 cm below the water interface of the black and odorous water body sediment layer (1); B. Pass the roots of the aquatic plant (3) through the round holes on the anode plate (2) and take root in the sediment, and utilize the synergistic effect of the plant roots and the anode electricity-producing bacterial community to promote the enrichment of the structurally stable electricity-producing bacterial community and the iron redox functional bacterial community; C. Set the cathode plate (5) at the water-air interface so that the cathode plate (5) floats in the water surface, and 30-70% of the area of the cathode plate (5) is exposed to the air; D. Connect the anode plate (2) and the cathode plate (5) with an external wire (6) and an external resistor (7) to form an electric current loop. A large number of electricity-producing bacterial communities and iron redox bacterial communities gradually enrich within 10 cm near the anode. The iron-reducing bacterial communities include: Gallionella iron bacteria, as well as Geobacter and Bacillus; promote the iron oxidation-reduction cycle process, so that the macromolecular organic matter in the black and odorous sediment degrades into small molecular organic acids, and the small molecular organic acids are completely oxidized; The aquatic plant (3) includes submerged plants and emergent plants: The submerged plants are one or any combination of Vallisneria natans, Ceratophyllum demersum, Myriophyllum verticillatum, Hydrilla verticillata, Potamogeton crispus, Ottelia acuminata, Potamogeton pectinatus; The emergent plants are one or any combination of Iris tectorum, Zizania latifolia, Acorus calamus, Typha orientalis, Thalia dealbata, Cyperus alternifolius; The anode plate (2) is a square electrode plate with circular openings (8) with a diameter of 5-10 cm arranged in an equidistant array. The materials of the anode plate (2) include any one of graphite felt, graphite plate, carbon felt, stainless steel plate, and stainless steel mesh; The materials of the cathode plate (5) include any one of graphite felt sheets and carbon felt sheets; The wire is a copper wire or a titanium wire; The external resistor (7) is an adjustable resistor or a fixed resistance resistor or an electrical appliance with a resistance value of 50-2000 ohms; The thickness of the sediment layer (1) is 10-35 cm, which is the sediment in black and odorous lakes, rivers, and ditches. The device includes: sediment layer (1), anode plate (2), aquatic plant (3), overlying water layer (4), cathode plate (5), external wire (6), external resistor (7); among them, the anode plate (2) is located below the surface of the sediment layer (1) with a depth of 3-10 cm. The roots of the aquatic plant (3) pass through the openings (8) of the anode plate (2) and penetrate into the sediment layer (1). The cathode plate (5) floats in the overlying water layer (4) and 30%-70% of its area is exposed to the air. One end of the external wire (6) is connected to the anode plate (2), the other end of the external wire (6) is connected to the external resistor (7), and the external resistor (7) is respectively connected to the external wire (6) and the cathode plate (5); the cathode plate (5) is composed of 6-12 electrode materials with an area connected by a cathode plate connection wire (9).

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