A synchronous remediation method for slightly polluted water bodies and riverbed sediments based on submerged plants - sediment microbial fuel cells

Abstract

A method for synchronous remediation of slightly polluted water bodies and river sediments based on submerged plant-deposited microbial fuel cells, which belongs to the field of ecological remediation technologies for urban slightly polluted rivers, lakes and other water bodies. The present invention aims to solve the problems in the existing microbial fuel cell technology, such as the difficulty in ensuring an anoxic environment at the anode, the long structure, and the inability to contain the release of hydrated ammonia in the sediment. Method: First, prepare the primary battery unit; second, arrange multiple primary battery units staggered in the river sediment of the slightly polluted water area to form an underwater forest system. The present invention is used for synchronous remediation of slightly polluted water bodies and river sediments based on submerged plant-deposited microbial fuel cells.

Description

Technical Field

[0001] The present invention belongs to the technical field of ecological restoration of urban slightly polluted river channels, lakes and other water bodies. Background Art

[0002] Nowadays, in order to balance the common goals of urban development and water resource protection, it is necessary to further improve the prevention and control of urban and suburban river water pollution and soil and water conservation, and continuously enhance the ecological environment protection level and ecology of water source areas. The control of endogenous pollution has gradually become the focus of river water quality guarantee. As the main pollution storage unit in the river ecosystem, river sediment will resuspend and release high-COD, N and other compounds under the conditions of hydraulic scouring and disturbance, and continuously diffuse with the temporal and spatial migration of water flow, causing secondary pollution of water bodies and seriously affecting the water quality of the overlying water in the river.

[0003] The existing control of endogenous pollution mainly relies on the green and environmental-friendly constructed wetland technology. This technology utilizes the synergistic effects of physical, chemical and biological aspects of the natural ecological system to purify sewage, and at the same time has the function of beautifying the environment, bringing certain environmental benefits. It should be noted that the effective implementation of this technology requires a large floor area, and it is prone to clogging after medium- and long-term operation. In severe cases, it will lead to the growth of water body bacteria, which is not conducive to the treatment and prevention of endogenous pollution in urban river channels with narrow water surfaces or shallow water bodies.

[0004] In recent years, the emerging microbial fuel cell technology utilizes the principle of primary battery. The anode is placed in the anaerobic sediment, and the cathode floats on the overlying water surface. The split-type two-stage is connected by a wire. Under the metabolic action of microorganisms on the anode surface, the organic matter in the shallow sediment undergoes anaerobic degradation, generating electrons and protons. The electrons are transmitted to the cathode through an external wire and reduce the oxygen in the air to form a circuit. This technology is often combined with the existing constructed wetland technology to reduce the floor area of the wetland and improve the pollutant treatment efficiency per unit area of this technology. However, in the actual outdoor environment, it is difficult to ensure a strict anaerobic environment around the anode due to the growth of wetland plants, equipment installation and the disturbance of water flow turbulence on the sludge. In addition, under the sunlight, the algae existing on the surface layer of the sediment carry out photosynthesis to produce oxygen, making it difficult to enrich anaerobic electricity-producing bacteria in the shallow sediment and causing the failure of the fuel cell anode. Moreover, with the continuous improvement of the water quality of the country's river channels in recent years, the material concentration difference between the water and soil interfaces has become larger, resulting in an accelerated release rate of pollutants that have not been effectively treated in the sediment, such as hydrated ammonia, etc., which hinders the steady improvement of water quality.

[0005] During the dynamic migration of river water, the variability of the spatial environment causes a series of facility structural problems in the split water purification system, such as the distance between the positive and negative electrodes is too long, the cathode is buried, and the anode is exposed and failed, which further leads to changes in the living environment of anode microorganisms and even technical failure. In addition, the uncontrollable position of suspended or floating plants and cathodes in the coupling technology also has certain obstacles to the navigation of small ships in the river. Summary of the invention

[0006] The present invention aims to solve the problems in the existing microbial fuel cell technology that the anode is difficult to ensure an oxygen-deficient environment, the structure is lengthy, and the release of hydrated ammonia in the sediment cannot be contained, and further provide a method for synchronously repairing micro-polluted water bodies and river sediments based on submerged plants and sedimentary microbial fuel cells.

[0007] A method for synchronously repairing micro-polluted water bodies and riverbed mud based on submerged plants-sedimentary microbial fuel cells is carried out in the following steps:

[0008] 1. Take the bottom mud within 4 cm of the bottom surface of the river channel in the slightly polluted water area, sinter and dry it to obtain dry mud, mix the dry mud with the microbial activation agent and apply it to the lower surface of the anode, then press and dry it to form a microbial activation agent film, and finally connect the upper surface of the anode with the submerged plant breeding area, plant submerged plants at the upper end of the submerged plant breeding area, set a cathode and a wire inside the submerged plant breeding area, the cathode wraps the root system of the submerged plant, and the wire connects the cathode to the anode to form a primary battery unit;

[0009] The height of the submerged plant cultivation area is 3 cm to 6 cm;

[0010] 2. Multiple primary battery units are staggered in the riverbed mud of slightly polluted waters to form an underwater forest system, and the entire anode and part of the submerged plant breeding area in the primary battery unit are buried in the riverbed mud of slightly polluted waters, and the distance between the upper surface of the anode and the surface of the riverbed mud of slightly polluted waters is 2cm to 5cm, thus completing the simultaneous restoration method of slightly polluted water bodies and riverbed mud based on submerged plant-sedimentary microbial fuel cells.

[0011] The beneficial effects of the present invention are:

[0012] 1. The present invention takes the root system of submerged plants as the main body, utilizes photosynthesis to supply oxygen to the cathode, and at the same time, enriches the common facultative anaerobic or nutrient-rich nitrifying bacteria such as Pseudomonas and Bacillus on the cathode surface, and the two together serve as electron transfer carriers to increase the cathode potential. In addition, under the electron transfer between the cathode and the above-mentioned facultative or nutrient-rich bacteria, nutrient-rich and heterotrophic nitrification are carried out simultaneously, and the hydrated ammonia in the surface water of the sediment can be oxidized to nitrite or nitrate, and then the anaerobic denitrifying bacteria in the rhizosphere can reduce the nitrate released from the surface of the sediment as an electron acceptor to nitrogen gas, thereby reducing the deposition of pollutants in the sediment.

[0013] 2. The anode surface is coated with a biological activator, which can maintain an anaerobic environment around the anode after the anode enters the sediment, accelerating the growth, aggregation and iteration of anaerobic electricity-producing microorganisms.

[0014] 3. Aerobic and facultative anaerobic bacteria growing on the cathode surface can oxidize, decompose and transform organic pollutants in the water body, producing small molecule nutrients to maintain the growth and reproduction of plants.

[0015] 4. The organic acids produced by plant roots can continuously infiltrate during root activities, generating a physical slow-release effect, continuously providing an organic carbon source for anode bacteria, so as to achieve the closed-loop continuous operation of the composite system for reducing pollutants in the sediment.

[0016] 5. The device formed by the method proposed in the present invention ensures the stability of the living environment of the biological communities at the anode and cathode inside the system, avoiding the impact on the system structure caused by the variability of the water flow environment. Under the dual mechanisms of "strengthening" and "protecting" the composite technology, it promotes the absorption and transformation of pollutants by "plants - microorganisms", ultimately achieving the purpose of treating sediment pollutants, accompanied by the gradual reduction of the volume and weight of the sediment, and achieving the effect of in-situ biological dredging.

[0017] Description of the Drawings

[0018] Figure 1 It is a three-dimensional structure diagram of the primary battery unit in Step 1 of Example 1. 1.1 is the anode, 1.2 is the microbial activation preparation film, 2.1 is the aluminum alloy steel cylinder, 2.4 is the food-grade PVC mesh plate arranged on the upper surface, and 2.6 is the submerged plant;

[0019] Figure 2 It is a layout diagram of the substrate in the submerged plant cultivation area in Step 1 of Example 1. 2.2 is the porous ceramsite, and 2.3 is the gravel;

[0020] Figure 3 It is a schematic connection structure diagram of the cathode and anode in the primary battery unit in Step 1 of Example 1. 2.7 is the cathode, 2.8 is the wire, and 2.9 is the resistor;

[0021] Figure 4 It is a schematic connection diagram of the anode and the submerged plant cultivation area in Step 1 of Example 1. 1.3 is the buckle, and 2.5 is the food-grade PVC mesh plate arranged on the lower surface;

[0022] Figure 5 It is a three-dimensional structure diagram of the small-scale test experimental device in Example 2. Detailed Implementation Modes

[0023] Embodiment 1: This embodiment is a method for synchronously repairing slightly polluted water bodies and riverbed sediments based on submerged plants - sediment microbial fuel cells, which is carried out according to the following steps:

[0024] 1. Take the sediment within a depth of 4 cm from the surface layer at the bottom of the slightly polluted water area river channel, sinter and dry it to obtain dry mud, mix the dry mud with a microbial activation preparation and apply it to the lower surface of the anode, then press and dry to form a microbial activation preparation film. Finally, connect the upper surface of the anode to the submerged plant cultivation area. Submerged plants are planted at the upper end of the submerged plant cultivation area, and a cathode and a wire are arranged inside the submerged plant cultivation area. The cathode wraps the roots of the submerged plants, and the wire connects the cathode to the anode to form a primary battery unit;

[0025] The height of the submerged plant cultivation area is 3 cm to 6 cm;

[0026] 2. Arrange multiple primary battery units staggered in the riverbed sediment of the slightly polluted water area to form an underwater forest system. The entire anode and part of the submerged plant cultivation area in the primary battery unit are buried in the riverbed sediment of the slightly polluted water area. The distance between the upper surface of the anode and the surface of the riverbed sediment of the slightly polluted water area is 2 cm to 5 cm, and thus the method for synchronously repairing slightly polluted water bodies and riverbed sediments based on submerged plants - sediment microbial fuel cells is completed.

[0027] In this specific embodiment, a microbial activation preparation is evenly covered on the lower surface of the anode. After the anode enters the sediment, it can accelerate the electron transfer process dominated by "facultative anaerobic microbial medium (such as Serratia)", quickly promote the growth of facultative anaerobic bacteria into dominant strains, rapidly consume the oxygen around the anode, form and continuously maintain an anaerobic environment around the anode, create a survival condition conducive to the growth, aggregation and iteration of anaerobic electricity-producing microorganisms, and use the electron transfer carrier to quickly form an anaerobic biofilm on the anode surface, achieving the expected denitrification and electricity-producing effects in a short time. That is, by applying a biological activation preparation on the anode, the facultative anaerobic microorganisms in the sludge can be "over-strengthened" to ensure a good anaerobic environment and preset extracellular electron transfer carriers, providing favorable conditions for improving the electricity-producing efficiency and sustainability of anaerobic electricity-producing bacterial groups.

[0028] In addition, among the plant components of the constructed wetland technology, the oxygen secretion of the roots of submerged plants and the spatial horizontal distribution characteristics of microorganisms in the rhizosphere are the key factors affecting the nitrogen (N) cycle in water environment sediments. Compared with other traditional floating and emergent plants, submerged plants have no stomata on their leaves. Instead, they have a complete intercellular ventilation tissue, which transports the oxygen produced by photosynthetic respiration to the roots. Part of it ensures the roots' absorption of NH4 + and PO4 2-Absorption, and the remaining part is released by the root system. Under the characteristics of oxygen production by plant roots and the decreasing distribution of rhizosphere oxygen content, aerobic and facultative anaerobic colonies are attracted to enrich. Therefore, in the present invention, the cathode is designed as an annular structure with a radius of 0.5 cm to 1 cm and wrapped around the root system of submerged plants. The continuous oxygen secretion characteristic of the root system is used to maintain and increase the electrode potential, and at the same time provide an attachment point for the enrichment of aerobic and facultative anaerobic bacteria; aerobic and facultative anaerobic bacteria can be used as electron transfer carriers to oxidize the hydrated ammonia released from the surface layer of the sediment into nitrate, and then be reduced to nitrogen gas under the action of denitrifying bacteria in the rhizosphere area, achieving the purpose of in-situ control of endogenous pollution. That is, in this specific embodiment, the root system of submerged plants is the main body, and the characteristics of oxygen secretion by the root system of submerged plants, electron transfer by the cathode, and the decreasing level of oxygen content in the root system area are utilized to enrich aerobic, facultative anaerobic, and anaerobic nitrogen metabolism functional bacteria from the inside out on the surface of the cathode of the microbial fuel cell, endowing the cathode with the function of removing hydrated ammonia pollutants, improving the removal of combined nitrogen (N) in the water environment and released from the sediment, and reducing the deposition of pollutants in the sediment.

[0029] In this specific embodiment, the cathode and the anode quickly form a circuit, promoting the stable purification of the sediment by the system; in addition, the wires and the cathode used are completely placed in a restrictive container, which plays a protective role for the electron transfer part, and at the same time effectively shortens the electron transfer distance between the anode and the cathode of the SMFC system, enhancing the stability of the system and realizing the synchronous in-situ repair of the overlying water and the sediment.

[0030] The device formed by the method proposed in this specific embodiment avoids the overly long vertical distribution space required by the existing coupling technology and the uncontrollability of plant growth, improving the operation efficiency and operation stability of the system. In addition, the organic acids produced by the plant roots can continuously infiltrate under the action of the root system activities, generating a physical slow-release effect, continuously providing organic carbon sources for the anode bacteria, so as to realize the closed-loop continuous operation of the composite system for reducing pollutants in the sediment. Under the coupled operation of the above improved technologies, a solution can be provided for the green and sustainable treatment of urban slightly polluted rivers, lakes and other water bodies and concealed biological dredging.

[0031] The beneficial effects of this embodiment are:

[0032] 1. In this embodiment, the root system of submerged plants is the main body, using photosynthesis to supply oxygen to the cathode. At the same time, facultative anaerobic or aerobic nitrifying bacteria such as Pseudomonas and Bacillus commonly found in the sediment are enriched on the surface of the cathode. The two together serve as electron transfer carriers to increase the cathode potential. In addition, under the electron transfer between the cathode and the above-mentioned facultative or aerobic bacteria, aerobic and heterotrophic nitrification proceed simultaneously, and the hydrated ammonia in the water body on the surface layer of the sediment can be oxidized to nitrite or nitrate. Subsequently, anaerobic denitrifying bacteria in the rhizosphere area can use the nitrate released from the surface layer of the sediment as an electron acceptor to be reduced to nitrogen gas, reducing the deposition of pollutants in the sediment.

[0033] 2. The anode surface is coated with a biological activator, which can maintain an anaerobic environment around the anode after the anode enters the sediment, accelerating the growth, aggregation, and iteration of anaerobic electricity-producing microorganisms.

[0034] 3. Aerobic and facultative anaerobic bacteria growing on the cathode surface can oxidize, decompose, and transform organic pollutants in the water body, producing small-molecule nutrients to maintain the growth and reproduction of plants.

[0035] 4. The organic acids produced by plant roots can continuously infiltrate during root activities, generating a physical slow-release effect, continuously providing organic carbon sources for anode bacteria, so as to achieve the closed-loop continuous operation of the composite system for reducing pollutants in the sediment.

[0036] 5. The device formed by the method proposed in this embodiment ensures the stability of the living environment of the biological communities at the anode and cathode inside the system, avoiding the impact on the system structure caused by the variability of the water flow environment. Under the dual mechanisms of "strengthening" and "protecting" the composite technology, it promotes the absorption and transformation of pollutants by "plants - microorganisms", ultimately achieving the purpose of treating sediment pollutants, accompanied by the gradual reduction of the volume and weight of the sediment, and achieving the effect of in-situ biological dredging.

[0037] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the slightly polluted water area described in Step 1 is a Class-IV water quality area. Others are the same as Specific Embodiment 1.

[0038] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that the microbial activation preparation described in Step 1 is composed of a preparation stabilizing component, a carbon source, and an electron transfer carrier; the preparation stabilizing component is composed of polyvinyl alcohol, sodium alginate, and water, and the concentration of polyvinyl alcohol in the preparation stabilizing component is 200 mg / L - 400 mg / L, and the concentration of sodium alginate is 50 mg / L - 100 mg / L; the carbon source is composed of glucose and water, and the concentration of glucose in the carbon source is 15 mg / L - 30 mg / L; the electron transfer carrier is composed of riboflavin, vitamin B12, and water, and the concentration of riboflavin in the electron transfer carrier is 10 mg / L - 20 mg / L, and the concentration of vitamin B12 is 2 mg / L - 4 mg / L; the volume ratio of the preparation stabilizing component to the carbon source is 1:(2 - 4); the volume ratio of the preparation stabilizing component to the electron transfer carrier is 1:(1 - 2). Others are the same as Specific Embodiment 1 or 2.

[0039] In this specific embodiment, riboflavin has biological electron transfer properties, and riboflavin and vitamin B12 have the function of acting as exogenous redox mediators, playing the role of an electron transfer bridge.

[0040] Embodiment 4: The difference between this embodiment and any one of Embodiments 1 to 3 is that the microbial activation preparation is prepared according to the following steps: Mix the preparation stabilizing components, carbon source and electron transfer carrier, freeze at a temperature of -20°C to -30°C for 4h to 8h, then thaw at room temperature, repeat the freeze-thaw cycle 3 to 5 times, and stir after the last thaw to obtain the microbial activation preparation. Others are the same as those in Embodiments 1 to 3.

[0041] Embodiment 5: The difference between this embodiment and any one of Embodiments 1 to 4 is that the mass ratio of the dry mud to the microbial activation preparation in Step 1 is 1:(4 to 6); the thickness of the microbial activation preparation film in Step 1 is 0.1 cm to 0.5 cm. Others are the same as those in Embodiments 1 to 4.

[0042] Embodiment 6: The difference between this embodiment and any one of Embodiments 1 to 5 is that the anode material in Step 1 is one or a combination of carbon felt, graphite felt and stainless steel plate; the anode shape in Step 1 is circular ring-shaped, with a thickness of 1 mm to 3 mm, a width of 4 cm to 6 cm, and a radius of 4 cm to 6 cm. Others are the same as those in Embodiments 1 to 5.

[0043] Embodiment 7: The difference between this embodiment and any one of Embodiments 1 to 6 is that the cathode material in Step 1 is one or a combination of titanium alloy wire, titanium mesh, graphite felt and modified graphite felt; the cathode in Step 1 is composed of multiple layers of rings arranged side by side from top to bottom, and the ring thickness is 1 mm to 2 mm, the width is 1 cm to 2 cm, the radius is 0.5 cm to 1 cm, and the distance between adjacent rings is 0.3 cm to 1 cm. Others are the same as those in Embodiments 1 to 6.

[0044] Embodiment 8: The difference between this embodiment and any one of Embodiments 1 to 7 is that the submerged plant cultivation area in Step 1 is formed by being wrapped by a container, and porous ceramsite, gravel and the surface layer bottom mud of the slightly polluted water area river channel are arranged in the container as substrates. Others are the same as those in Embodiments 1 to 7.

[0045] The described submerged plant cultivation area is composed of a food-grade PVC net, a lightweight aluminum alloy cylinder, porous ceramsite, gravel, the surface layer bottom mud of the slightly polluted water area river channel and submerged plants to form a semi-closed cultivation space.

[0046] Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is that the submerged plants in Step 1 are one or a combination of Hydrilla verticillata, Potamogeton crispus, Vallisneria natans and Ceratophyllum demersum. Others are the same as those in Embodiments 1 to 8.

[0047] Specific Embodiment Ten: The difference between this embodiment and any one of Embodiments One to Nine is that: the wire described in Step One is a copper wire or a titanium wire; a resistor of 300Ω - 600Ω is provided on the wire described in Step One. Others are the same as those in Embodiments One to Nine.

[0048] The following examples are used to verify the beneficial effects of the present invention:

[0049] Example One, combined with Figures 1 to 4 Specific description:

[0050] A method for synchronous remediation of slightly polluted water bodies and river bottom mud based on a submerged plant - sediment microbial fuel cell, which is carried out according to the following steps:

[0051] One, take the bottom mud within a depth of 4 cm from the surface layer at the bottom of the slightly polluted water area river for sintering and drying to obtain dry mud, mix the dry mud with a microbial activation preparation and apply it to the lower surface of the anode, then press and dry to form a microbial activation preparation film, and finally connect the upper surface of the anode to the submerged plant cultivation area. Submerged plants are planted at the upper end of the submerged plant cultivation area, a cathode and a wire are arranged inside the submerged plant cultivation area, the cathode wraps the roots of the submerged plants, and the wire connects the cathode to the anode to form a primary battery unit;

[0052] The height of the submerged plant cultivation area is 5 cm;

[0053] The mass ratio of the dry mud to the microbial activation preparation is 1:5; the thickness of the microbial activation preparation film is 0.15 cm;

[0054] Two, stagger multiple primary battery units in the river bottom mud of the slightly polluted water area to form an underwater forest system, and the entire anode and part of the submerged plant cultivation area in the primary battery unit are buried in the river bottom mud of the slightly polluted water area. The distance between the upper surface of the anode and the surface of the river bottom mud of the slightly polluted water area is 3 cm, that is, the method for synchronous remediation of slightly polluted water bodies and river bottom mud based on a submerged plant - sediment microbial fuel cell is completed;

[0055] The slightly polluted water area described in Step One is a water body with Class IV water quality in the Songhua River Basin.

[0056] The microbial activation preparation described in Step 1 consists of a preparation stabilizing component, a carbon source, and an electron transfer carrier; the preparation stabilizing component is composed of polyvinyl alcohol, sodium alginate, and water, and the concentration of polyvinyl alcohol in the preparation stabilizing component is 300 mg / L, and the concentration of sodium alginate is 75 mg / L; the carbon source is composed of glucose and water, and the concentration of glucose in the carbon source is 20 mg / L; the electron transfer carrier is composed of riboflavin, vitamin B12, and water, and the concentration of riboflavin in the electron transfer carrier is 15 mg / L, and the concentration of vitamin B12 is 3 mg / L; the volume ratio of the preparation stabilizing component to the carbon source is 1:3; the volume ratio of the preparation stabilizing component to the electron transfer carrier is 1:2;

[0057] The microbial activation preparation is prepared according to the following steps: Mix the preparation stabilizing component, the carbon source, and the electron transfer carrier, freeze at a temperature of -25 °C for 6 h, then thaw at room temperature, repeat the freezing and thawing 3 times, and stir after the last thawing to obtain the microbial activation preparation.

[0058] The anode material described in Step 1 is a stainless steel plate, with an annular plate shape, a thickness of 1 mm, a width of 4 cm, and a radius of 4 cm. The surface is sanded with 80-mesh sandpaper to provide attachment points for the growth and enrichment of microorganisms.

[0059] The cathode described in Step 1 is a combination of titanium alloy wire and graphite felt; the cathode described in Step 1 is composed of 3 layers of rings arranged side by side from top to bottom. Specifically, with the graphite felt as the ring, 3 graphite felt rings are connected by titanium alloy wire, and the ring thickness is 1 mm, the width is 1 cm, the distance between adjacent rings is 3 mm, and the radii from top to bottom are 1 cm, 0.75 cm, and 0.5 cm in sequence.

[0060] The submerged plant cultivation area described in Step 1 is formed by being wrapped in a container. The container is a semi-closed area surrounded by an aluminum alloy steel cylinder and food-grade PVC mesh plates arranged on the upper and lower surfaces through buckles. The aperture of the food-grade PVC mesh plate arranged on the upper surface is 5 mm, and the aperture of the food-grade PVC mesh plate arranged on the lower surface is 1 mm; and porous ceramsite (Gongyi Youlan Environmental Protection Technology Co., Ltd.) with a particle size of 6 - 8 mm, gravel with a particle size of 1 - 4 cm, and the surface sediment of a slightly polluted water area river channel are set as substrates in the container, and the substrates in the container are evenly arranged from bottom to top in ascending order of particle size;

[0061] The submerged plant described in Step 1 is Vallisneria natans, and 2 to 3 plants of Vallisneria natans are planted in each primary battery unit;

[0062] The wire described in Step 1 is a copper wire; a 500 Ω resistor is provided on the wire described in Step 1;

[0063] In Step 1, the anode is connected to the aluminum alloy steel cylinder in the submerged plant cultivation area through a buckle.

[0064] In Step 1, the wire passes through the food-grade PVC mesh plate provided on the lower surface to connect the cathode and the anode.

[0065] In this embodiment, the river bottom mud is used as the dividing line, and it is divided into an anaerobic decomposition area and an aerobic purification area from bottom to top. Anaerobic decomposition area - the anode covered with a microbial activation preparation film is completely buried inside the bottom mud. Aerobic purification area - part of the submerged plant cultivation area is buried in the river bottom mud of the slightly polluted water area, and part of the submerged plant cultivation area is exposed.

[0066] This coupling unit can be directly placed in the river of slightly polluted water body, and the annular anode plate is pressed into the river bottom mud by its own gravity. Through the rapid enrichment of facultative anaerobes, the dissolved oxygen around the anode plate is consumed, maintaining a continuous anaerobic environment around the anode plate, providing material and living environment guarantees for the growth, aggregation and iteration of anaerobic electricity-producing microorganisms such as Proteobacteria and Firmicutes, and decomposing and oxidizing the organic matter and NH3 - N in the bottom mud into CO2, N2, electrons, etc. The electrons can use riboflavin and vitamin B12 contained in the biological preparation as electron transport carriers, transfer them to the electrode anode, and transport them to the battery cathode through the circuit to reduce NH3-N and NO3 released from the water body and the bottom mud - N, etc. The current formed by the transfer of electrons between the anode and cathode can accelerate the nitrification process in the plant root zone and the denitrification process in the rhizosphere zone connected to the cathode. In this embodiment, by adding the reduction reaction on the cathode surface, the operation efficiency of the coupling system is effectively improved and the pollution control of the water body is strengthened.

[0067] Compared with the traditional coupling system, the device in Embodiment 1 can synchronously repair the slightly polluted water body and the bottom mud, and effectively control the NO3-N released from the water body and the bottom mud.

[0068] Embodiment 2, combined with Figure 5Specific description: The difference between this embodiment and Embodiment 1 is as follows: In Step 1, the simulated slightly polluted river sediment is taken for sintering and drying to obtain dry sediment. In Step 1, porous ceramsite with a particle size of 6 - 8 mm (Gongyi Youlan Environmental Protection Technology Co., Ltd.), gravel with a particle size of 1 - 4 cm, and simulated slightly polluted river sediment are set in the container as substrates. In Step 1, 3 Vallisneria natans plants are planted in each primary battery unit. In Step 2, 5 primary battery units are arranged staggered in the sediment of the small-scale experimental device. The small-scale experimental device is an acrylic water tank with an effective volume of 70 L. The bottom of the water tank is filled with 15 cm of simulated slightly polluted river sediment, and the water depth of the overlying water is 30 cm. The simulated slightly polluted river sediment is specifically prepared by using the sediment of the Songhua River channel. The TOC content in the simulated slightly polluted river sediment is 2.78%, the TN concentration is 13.47 mg / g, and the TP concentration is 2.73 mg / g. Others are the same as Embodiment 1. In this embodiment, a small-scale experimental device is established to compare with the treatment effect of the traditional coupling system.

[0069] Comparative experiment, using the traditional separated anode microbial fuel cell as the control group: The difference between this embodiment and Embodiment 2 is as follows: Step 1 is cancelled. In Step 2, the carbon felt is used as the anode and buried in the sediment of the small-scale experimental device. The anode is 4 cm long and 3 cm wide, and the distance between the upper surface of the anode and the sediment surface is 3 cm. The graphite plate is used as the cathode and floats on the water surface, and the distance from the sediment surface is 30 cm. The cathode and the anode are connected by wires, and Vallisneria natans is planted on the anode carbon felt. Others are the same as Embodiment 2.

[0070] In Embodiment 2 and the comparative experiment, the hydraulic retention time (HRT) of the small-scale experimental device is 12 h, and simulated light is carried out from 6 am to 6 pm every day. The room temperature is maintained at 25 ± 2 °C. The water quality of the influent of the overlying water is prepared according to the standard of surface water class Ⅳ: the COD concentration is 25 ± 0.2 mg / L, the TN (NH3-N) concentration is 1.5 ± 0.4 mg / L, and the TP (HPO4 2- ) concentration is 0.2 ± 0.1 mg / L. The sludge sampling position is 4 cm - 6 cm below the surface sediment, and the horizontal distance from the anode is 2 cm - 4 cm. The water sample sampling position is 5 cm - 8 cm above the overlying water surface.

[0071] After the system operates stably, the sediment and overlying water of Embodiment 2 and the comparative experiment are measured, and the results are as follows:

[0072] Table 1 Control values of various pollutants in the sediment

[0073]

[0074] Table 2 Control values of various pollutants in the overlying water after 30 days of stable operation

[0075]

[0076] Compared with the traditional coupling system, the device in the embodiment can synchronously repair slightly polluted water bodies and sediment, and effectively control the NH3-N and NO3-N released from the water bodies and sediment, meeting the Class II surface water quality standard.

[0077] Example 3: The difference between this example and Example 2 is that in Step 2, 2 primary battery units are staggered in the sediment of the bench-scale experimental device, one group is coated with a microbial activation preparation, and the other group is not coated with a microbial activation preparation. Others are the same as in Example 2.

[0078] The HRTs are 2, 4, and 6 h respectively, and simulated light is carried out from 6 am to 6 pm every day; the room temperature is maintained at 25 ± 2 °C; the quality of the overlying water inlet is prepared based on Class IV surface water: the COD concentration is 25 ± 0.2 mg / L, the TN (NH3-N) concentration is 1.5 ± 0.4 mg / L, and the TP (HPO4 2- ) concentration is 0.2 ± 0.1 mg / L. After the effluent concentration is stable, an ORP meter is used to measure the oxidation-reduction potential (ORP value) near the anode of the purification device. Each set of data is measured 3 times and the average value is taken. The water sample sampling position is 5 cm to 8 cm above the overlying water surface.

[0079] When HRT is 2 h: the ORP of the purification device part coated with the microbial activation preparation is 19 ± 4 mV, the ORP of the purification device part not coated with the microbial activation preparation is 34 ± 5 mV, and the ORP of the anode of the traditional separate microbial fuel cell in the comparative experiment is 49 ± 5 mV.

[0080] When HRT is 4 h: the ORP of the purification device part coated with the microbial activation preparation is 16 ± 3 mV, the ORP of the purification device part not coated with the microbial activation preparation is 30 ± 3 mV, and the ORP of the anode of the traditional separate microbial fuel cell in the comparative experiment is 37 ± 3 mV.

[0081] When HRT is 6 h: the ORP of the purification device part coated with the microbial activation preparation is 12 ± 4 mV, the ORP of the purification device part not coated with the microbial activation preparation is 28 ± 4 mV, and the ORP of the anode of the traditional separate microbial fuel cell in the comparative experiment is 31 ± 2 mV.

[0082] The above test data show that compared with the traditional separate device, the integrated device can promote the occurrence of anodic denitrification reaction; at the same time, the anode coated with the microbial activation preparation is less affected by water flow disturbance, can create a good anaerobic environment, further strengthen the anodic denitrification reaction, and ensure the effective removal of nitrate nitrogen / nitrite nitrogen in the sediment.

Claims

1. A method for synchronous remediation of slightly polluted water bodies and riverbed sediments based on submerged plants - sediment microbial fuel cells, characterized in that It is carried out according to the following steps: First, take the sediment within a depth of 4 cm from the bottom surface of the river channel in the slightly polluted water area, sinter and dry it to obtain dry mud. Mix the dry mud with the microbial activation preparation and apply it to the lower surface of the anode. Then press and dry it to form a microbial activation preparation film. Finally, connect the upper surface of the anode to the submerged plant cultivation area. Submerged plants are planted at the upper end of the submerged plant cultivation area. A cathode and a wire are arranged inside the submerged plant cultivation area. The cathode wraps the roots of the submerged plants, and the wire connects the cathode to the anode to form a primary battery unit; The height of the submerged plant cultivation area is 3 cm to 6 cm; The microbial activation preparation is composed of a preparation stabilizing component, a carbon source, and an electron transfer carrier; the preparation stabilizing component is composed of polyvinyl alcohol, sodium alginate, and water, and the concentration of polyvinyl alcohol in the preparation stabilizing component is 200 mg / L to 400 mg / L, and the concentration of sodium alginate is 50 mg / L to 100 mg / L; the carbon source is composed of glucose and water, and the concentration of glucose in the carbon source is 15 mg / L to 30 mg / L; the electron transfer carrier is composed of riboflavin, vitamin B12, and water, and the concentration of riboflavin in the electron transfer carrier is 10 mg / L to 20 mg / L, and the concentration of vitamin B12 is 2 mg / L to 4 mg / L; the volume ratio of the preparation stabilizing component to the carbon source is 1:(2 - 4); the volume ratio of the preparation stabilizing component to the electron transfer carrier is 1:(1 - 2); The submerged plant cultivation area is wrapped by a container, and porous ceramsite, gravel, and the surface sediment of the slightly polluted water area river channel are arranged in the container as substrates; The anode is connected to the aluminum alloy steel cylinder of the submerged plant cultivation area through a buckle; Second, stagger multiple primary battery units in the sediment of the slightly polluted water area river channel to form an underwater forest system. The whole anode and part of the submerged plant cultivation area in the primary battery unit are buried in the sediment of the slightly polluted water area river channel. The distance between the upper surface of the anode and the surface of the sediment of the slightly polluted water area river channel is 2 cm to 5 cm, and thus the synchronous repair method for slightly polluted water bodies and river channel sediment based on submerged plant - sediment type microbial fuel cells is completed.

2. The synchronous remediation method for slightly polluted water body and river sediment based on submerged plant-deposited microbial fuel cell according to claim 1, characterized in that The slightly polluted water area described in step one is a Class IV water quality area.

3. A method for simultaneously repairing slightly polluted water bodies and riverbed sediments based on submerged plants - sediment microbial fuel cells according to claim 1, characterized in that The microbial activation preparation described in step one is prepared according to the following steps: Mix the preparation stabilizing component, the carbon source, and the electron transfer carrier, and freeze it for 4 h to 8 h under the condition of a temperature of -20°C to -30°C, then thaw it at room temperature, repeat the freezing and thawing 3 to 5 times, and stir it after the last thawing to obtain the microbial activation preparation.

4. A method for synchronous remediation of slightly polluted water bodies and riverbed sediments based on submerged plants - sediment microbial fuel cells according to claim 1, characterized in that The mass ratio of the dry mud to the microbial activation preparation in step one is 1:(4 - 6); the thickness of the microbial activation preparation film in step one is 0.1 cm to 0.5 cm.

5. A method for synchronous remediation of slightly polluted water bodies and riverbed sediments based on submerged plants - sediment microbial fuel cells according to claim 1, characterized in that The anode material in step one is one or a combination of several of carbon felt, graphite carbon felt, and stainless steel plate; the anode shape in step one is circular ring-shaped, with a thickness of 1 mm to 3 mm, a width of 4 cm to 6 cm, and a radius of 4 cm to 6 cm.

6. The synchronous remediation method for slightly polluted water body and river sediment based on submersed plant - sediment microbial fuel cell according to claim 1, characterized in that The cathode material described in Step 1 is one or a combination of titanium alloy wire, titanium mesh, graphite felt, and modified graphite felt; the cathode in Step 1 is composed of multiple layers of rings arranged side by side from top to bottom, and the thickness of the ring is 1 mm to 2 mm, the width is 1 cm to 2 cm, the radius is 0.5 cm to 1 cm, and the distance between adjacent rings is 0.3 cm to 1 cm.

7. A method for synchronously repairing slightly polluted water bodies and riverbed sediments based on submerged plants - sediment microbial fuel cells according to claim 1, characterized in that The submerged plants described in Step 1 are one or a combination of Hydrilla verticillata, Potamogeton crispus, Vallisneria natans, and Ceratophyllum demersum.

8. A method for synchronously repairing slightly polluted water bodies and riverbed sediments based on submerged plants - sediment microbial fuel cells according to claim 1, characterized in that The wire described in Step 1 is a copper wire or a titanium wire; a resistor of 300 Ω to 600 Ω is provided on the wire in Step 1.

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