Method for simultaneously repairing water body by using emergent macrophyte-sediment microbial fuel cell

Abstract

The present application relates to the field of environmental management technology, and discloses a kind of emergent aquatic plant-sediment microbial fuel cell synchronous remediation water body method, comprising the following steps: S1, constructs emergent aquatic plant-SMFC coupling system, emergent aquatic plant-SMFC coupling system includes emergent aquatic plant and SMFC, SMFC includes anode electrode, modified cathode electrode and external resistance;Emergent aquatic plant is planted around anode electrode, so that anode electrode is contacted with bottom mud;S2, preparation modified cathode electrode, and the catalytic activity of cathode electrode is enhanced by electrochemical oxidation modification;S3, domestication electric active microorganism, emergent aquatic plant-SMFC coupling system is placed in room temperature domestication, and the electricity generation capacity of anode electrode is improved by introducing bottom mud rich in organic matter or exogenous inoculation microorganism;S4, start and run system, and the concentration change of chlorophyll a, ammonia nitrogen, total nitrogen and total phosphorus in water body is monitored in real time.The present application provides a kind of green, economic and efficient algal bloom water remediation technology, and is suitable for the ecological management of algal bloom water.

Description

Technical Field

[0001] This invention relates to the field of environmental remediation technology, specifically to a method for the simultaneous remediation of water bodies using emergent plants-sediment microbial fuel cells. Background Technology

[0002] Large amounts of nitrogen and phosphorus nutrients are discharged into water bodies through agricultural runoff, industrial emissions, and domestic sewage, leading to increased nutrient concentrations and frequent algal blooms in slow-moving water bodies such as lakes, estuaries, and bays. Algal blooms not only damage aquatic ecosystems but also pose a threat to human health. Therefore, there is an urgent need to develop efficient and sustainable remediation technologies to mitigate the pollution and negative impacts of algal blooms on water bodies and ecosystems.

[0003] Domestic and international research has developed various treatment methods based on physical, chemical, and biological approaches for treating algal blooms. Among them, hydrogen peroxide in chemical methods can not only effectively remove algae, but also decompose into water and oxygen, making it a green algaecide with great application potential. However, in practical applications, directly adding hydrogen peroxide for algae removal faces the following problems: (1) Because hydrogen peroxide decomposes rapidly in water, it needs to be added multiple times to maintain the algae removal effect, resulting in high treatment costs; (2) Because hydrogen peroxide is a strong oxidant, improper operation during storage, transportation, and use may cause damage to personnel and equipment, posing significant safety hazards. To overcome the above problems, in-situ generation of hydrogen peroxide for algae removal has become an option. For example, patent CN202111426956.4 discloses a fully automatic algae control device and method for producing hydrogen peroxide by solar photocatalysis, used to control excessive algal growth during algal blooms. Unlike photocatalysis, patent CN202011420278.6 discloses a method for in-situ driven electro-Fenton degradation of red tide / algal bloom algae based on SMFC.

[0004] Although hydrogen peroxide generated in situ based on photocatalysis and SMFC can continuously and cost-effectively remove algae from algal bloom waters, the following drawbacks still exist: (1) Low hydrogen peroxide generation efficiency: Photocatalysis relies on sunlight and can only operate during the day, and is limited by light intensity and reactor efficiency; Although SMFC can operate around the clock, its hydrogen peroxide generation efficiency is limited by insufficient organic matter concentration in the sediment and low catalytic activity of the cathode electrode, resulting in limited algae removal efficiency. (2) Insufficient removal effect on nitrogen and phosphorus pollution: After algae removal, the dead algae decompose and release large amounts of nitrogen and phosphorus. Existing photocatalysis and SMFC technologies have failed to effectively remove these nutrients, which may lead to secondary pollution of the water body and even trigger a new round of algal blooms. (3) Risk of nitrogen and phosphorus release from sediment: The sediment of algal bloom waters usually stores high concentrations of nitrogen and phosphorus substances. Under environmental conditions such as reduced dissolved oxygen, these nutrients may be released into the water body, exacerbating water pollution problems and increasing the difficulty of treatment. Summary of the Invention

[0005] To address the aforementioned shortcomings in existing technologies, this invention provides a method for simultaneous water body remediation using emergent plants and sediment microbial fuel cells. This method fully utilizes the ecological role of emergent plants and the catalytic properties of electrochemically modified cathodes to achieve efficient water body remediation through multiple mechanisms.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: a method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells, comprising the following steps:

[0007] S1. Construct an emergent plant-SMFC coupling system. The emergent plant-SMFC coupling system includes emergent plants and SMFC. The SMFC includes an anode electrode, a modified cathode electrode, and an external resistor. Plant the emergent plants around the anode electrode so that the anode electrode is in contact with the bottom sediment.

[0008] S2, Prepare a modified cathode electrode, and perform electrochemical oxidation modification on the cathode electrode to enhance its catalytic activity;

[0009] S3, acclimatizing electroactive microorganisms, acclimatizing the emergent plant-SMFC coupling system at room temperature, and improving the power generation capacity of the anode electrode by introducing bottom sediment rich in organic matter or exogenous inoculated microorganisms;

[0010] S4: Start and run the system to monitor the changes in chlorophyll a, ammonia nitrogen, total nitrogen and total phosphorus concentrations in the water in real time until the target treatment effect is achieved.

[0011] Furthermore, in the above-mentioned method for simultaneous water remediation using emergent plant-sediment microbial fuel cells, the anode electrode is a carbon felt, carbon rod, carbon cloth, or carbon particle electrode, which is arranged in the bottom sediment to promote electron transfer by electroactive microorganisms.

[0012] Furthermore, in the above-mentioned method for simultaneous water body remediation using emergent plants and sediment microbial fuel cells, the emergent plants include windmill grass, canna lily, reed, cattail, water bamboo, water onion, calamus, or arrowhead.

[0013] Furthermore, in the above-mentioned method for simultaneous water remediation using emergent plant-sediment microbial fuel cells, the cathode electrode is made of carbon felt, carbon rod, or carbon cloth. The specific method for preparing the modified cathode electrode in S2 is as follows: using an electrochemical workstation in constant current mode, the cathode electrode is set as the working electrode; a carbon rod is used as the counter electrode, and the electrolyte is ammonium fluoride solution; oxidation treatment is performed under constant current conditions, followed by rinsing the cathode electrode with deionized water until neutral, and drying it at 55°C for 10 hours to obtain the modified cathode electrode.

[0014] Furthermore, in the above-mentioned method for simultaneous water remediation using emergent plants-sediment microbial fuel cells, the oxidation treatment parameters include: a constant current range of 1~1000mA, an oxidation time of 1~60 minutes, and an ammonium fluoride solution concentration of 1~500mM.

[0015] Furthermore, in the above-mentioned method for simultaneous water remediation using emergent plant-sediment microbial fuel cells, the modified cathode electrode is placed at the interface between the algal bloom water and the air to enhance oxygen utilization efficiency and promote hydrogen peroxide generation.

[0016] Furthermore, in the above-mentioned method for simultaneous water remediation using emergent plant-sediment microbial fuel cells, the external resistor is connected in series with the anode electrode and the modified cathode electrode via a metal wire, with the external resistor located between the anode electrode and the cathode electrode; the metal wire is platinum wire, titanium wire, or stainless steel wire; and the resistance value of the external resistor ranges from 0 to 100,000 Ω.

[0017] Furthermore, in the above-mentioned method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells, the acclimation of electroactive microorganisms in S3 specifically involves: slowly injecting the effluent from the anode of a mature microbial fuel cell into the sediment where the anode electrode is located to promote enhanced microbial activity, and considering the acclimation complete when the anode output voltage increment is less than 5% for two consecutive cycles.

[0018] Furthermore, in the above-mentioned method for simultaneous water remediation using emergent plant-sediment microbial fuel cells, during system operation in S4, the modified cathode electrode is periodically rinsed with deionized water to remove deposits on the electrode surface, thereby improving electrode performance and system operating efficiency.

[0019] Furthermore, in the above-mentioned method for simultaneous water remediation using emergent plants-sediment microbial fuel cells, during system operation in S4, the electrochemical parameters of the cathode electrode and the planting density of emergent plants are dynamically adjusted based on the real-time monitoring of changes in the concentrations of chlorophyll a, ammonia nitrogen, total nitrogen, and total phosphorus in the water.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) Highly efficient removal and degradation of algal blooms. Electroactive microorganisms on the anode electrode of the SMFC simultaneously catalyze the decomposition of organic matter in the sediment of algal bloom water bodies and organic matter secreted by the rhizosphere of emergent plants, generating a large number of electrons. These electrons travel through the metal wire and external resistor to the cathode, where they are used to generate hydrogen peroxide in situ, thereby efficiently removing algae. At the same time, dead algal blooms sink into the sediment, and the electroactive microorganisms can utilize the organic matter produced by the decomposition of algal blooms to further promote the generation of hydrogen peroxide, achieving continuous and efficient removal and degradation of algal blooms.

[0022] (2) Efficiently remove nitrogen and phosphorus nutrients released during the degradation of algal blooms, thus avoiding water quality deterioration and the recurrence of algal blooms. On the one hand, emergent plants directly absorb nitrogen and phosphorus from eutrophic waters through their growth; on the other hand, emergent plants form a microenvironment containing aerobic, facultative, and anaerobic elements in the root zone through rhizosphere oxygen secretion. This microenvironment can promote the nitrification-denitrification of nitrogen and aerobic phosphorus storage by microorganisms in the sediment, thereby enhancing the removal efficiency of nitrogen and phosphorus nutrients in eutrophic waters.

[0023] (3) Reduce the release of nitrogen and phosphorus nutrients from sediment in water bodies. This invention reduces the release of nitrogen from sediment in water bodies by the absorption of nitrogen by emergent plants and the enhancement of denitrification by sediment microorganisms through rhizosphere oxygen secretion; and reduces the release of phosphorus from sediment in water bodies through the iron-sulfur-phosphorus cycle by increasing the redox potential of sediment through rhizosphere oxygen secretion by emergent plants and the SMFC anode electrode.

[0024] (4) This invention combines microbial electrochemical technology and plant ecology to improve the efficiency and sustainability of algal bloom remediation through the self-regulating ability of natural ecosystems. This method can not only effectively control the growth of algae in algal blooms, but also solve the problem of nitrogen and phosphorus pollution in the water body at the same time, providing a new environmentally friendly solution for the treatment of algal bloom water bodies. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the high-efficiency algae removal, nitrogen removal, and phosphorus removal device of the present invention;

[0026] Figure 2 The change in the amount of hydrogen peroxide generated in situ in Example 1 over time;

[0027] Figure 3 The change of chlorophyll a in the water body of the algal bloom over time in Example 1;

[0028] Figure 4 The change in ammonia nitrogen concentration over time in Example 1;

[0029] Figure 5 This refers to the change in total nitrogen concentration over time in Example 1;

[0030] Figure 6 The change in total phosphorus concentration over time in Example 1;

[0031] The components are: 1. bottom sediment; 2. anode electrode; 3. algal bloom water body; 4. cathode electrode; 5. emergent plants; 6. light source; 7. metal wire; 8. external resistor. Detailed Implementation

[0032] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0033] Example 1

[0034] Step 1: As Figure 1 As shown, an emergent plant-SMFC coupled system was constructed. The sediment layer 1 was 15cm high, sourced from Yaohu Lake in Nanchang City and filtered through a 2mm screen. Optionally, the anode electrode 2 was made of carbon felt, with apparent dimensions of 30.0cm × 10.0cm × 1.0cm. A 2.0cm diameter circular hole was cut in the center of the anode electrode, which was then rolled into a cylinder and sewn together with titanium wire. Emergent plants 5 (5 *Gnaphalium affine* plants, 46.2–54.4cm tall, with roots penetrating the circular hole on the anode electrode) were then planted on the anode electrode. Finally, the anode electrode was placed in the sediment, with the circular hole facing upwards and positioned at the top of the sediment. The algal bloom water body 3 was 20cm high.

[0035] Step 2: Modifying the cathode electrode. Optionally, the cathode electrode 4 is made of carbon felt with apparent dimensions of Φ10.0cm × 1.0cm. Using an electrochemical workstation (French Biological VSP-300) in constant current mode, the cathode electrode is set as the working electrode, the carbon rod (ø0.8cm × 15cm) as the counter electrode, the constant current is set to 200mA, the oxidation time to 30min, and the ammonium fluoride concentration to 50mM. After oxidation, the cathode electrode is rinsed with deionized water until neutral and dried at 55℃ for 10h. Then, a 2.0cm diameter circular hole is cut in the center of the modified cathode electrode, allowing the emergent plant to pass through the hole, and the cathode electrode is placed 0.5cm below the water surface.

[0036] Step 3: Set up simulated sunlight. Optionally, use two sets of 18W LED lights as light source 6, with the light source 50.0cm above the surface of the algal bloom, and set the light-dark ratio to 12h / 12h.

[0037] Step 4: Connect the current loop. Optionally, the metal wire 7 is a titanium wire, connecting the anode electrode and the modified cathode electrode. Optionally, the external resistor 8 is set to 1000Ω and connected in series between the anode electrode and the cathode electrode.

[0038] Step 5: Start the system. Inject 100 mL of microbial fuel cell anode effluent containing sodium acetate as the organic substrate into the anode carbon felt electrode using a syringe. Slowly inject the algal bloom water onto the bottom sediment using a siphon method until the water reaches a height of 20 cm. The algae in the bloom water is Microcystis aeruginosa, with an algal density of 2.5 × 10⁸ cells / L, chlorophyll a of 108 μg / L, total phosphorus of 2.0 mg / L, total nitrogen of 8.0 mg / L (ammonia nitrogen 2.0 mg / L, nitrate nitrogen 6.0 mg / L), transparency of 24 cm, permanganate index of 42 mg / L, sodium chloride concentration of 0.07 mg / L, resulting in a solution conductivity of 167 μS / cm.

[0039] Step Six: Acclimation of Electroactive Microorganisms. Place the emergent plant-SMFC coupling system at room temperature (25±2℃) for acclimation, changing the algal bloom water every 2 days, i.e., one cycle. When the output voltage stabilizes and the increment is less than 5% for two consecutive cycles, it indicates that the coupling system has been successfully started.

[0040] Step 7: Analyze hydrogen peroxide content. Replace the external resistor with a 50Ω resistor, replace the algal bloom water from Step 5, remove Microcystis aeruginosa, and maintain other water quality conditions consistently. Run continuously for 10 days, taking samples periodically to analyze changes in hydrogen peroxide concentration in the liquid phase.

[0041] Step 8: Run the system. Replace the water in the algal bloom body, maintaining the water quality conditions consistent with those in Step 5. Run the system for 45 days, taking samples periodically to analyze the concentrations of chlorophyll a, ammonia nitrogen, total nitrogen, and total phosphorus in the liquid phase.

[0042] Compare with Example 1:

[0043] The control group, consisting only of SMFC (without emergent plants), was run, while all other operating conditions remained the same as in Example 1.

[0044] Compare with Example 2:

[0045] The emergent plant-SMFC control group was run, meaning the SMFC cathode electrode was not modified, and all other operating conditions were the same as in Example 1.

[0046] Results: During the operation phase, the concentration of hydrogen peroxide in the water of the emergent plant-SMFC coupled system with modified cathode gradually increased and stabilized at 3.17±0.15 mg / L, significantly higher than that of the emergent plant-SMFC coupled system without modified cathode (1.81±0.08 mg / L). Figure 2 ) and SMFC system (1.36±0.14mg / L, Figure 2This indicates that electrochemical oxidation modification significantly improved the catalytic activity and selectivity of the cathode electrode, thereby enhancing the hydrogen peroxide generation capacity. Simultaneously, the coupling of emergent plants with SMFCs promoted electricity generation through rhizosphere secretion of organic matter, improving the system's current efficiency and further increasing hydrogen peroxide production.

[0047] Regarding the removal of algal blooms, the modified cathode emergent plant-SMFC coupled system reduced the chlorophyll a concentration in the water from an initial 108.2±6.1 μg / L to 0 μg / L in just 12 days, while the unmodified cathode emergent plant-SMFC coupled system and the SMFC system required 24 days and 30 days, respectively. Figure 3 This result indicates that the modified cathode significantly improves algae removal efficiency, and the synergistic effect of emergent plants and SMFC further enhances the overall algae removal capacity of the system.

[0048] In terms of nitrogen pollution control, the modified cathode emergent plant-SMFC coupling system showed a brief increase in ammonia nitrogen concentration in the water during the initial operation phase, followed by a rapid decrease, reaching 0 mg / L within 28 days. Figure 4 The unmodified cathode system required 32 days to completely remove ammonia nitrogen. In contrast, although the ammonia nitrogen concentration in the SMFC system gradually decreased in the later stages of operation, it only dropped to 2.68±0.14 mg / L after 45 days, still higher than the initial concentration of 2.13±0.09 mg / L, showing significant insufficient removal. Figure 4 Regarding total nitrogen removal, the modified cathode emergent plant-SMFC coupled system reduced the total nitrogen concentration in the water to 1.13±0.26 mg / L after 45 days, significantly lower than the 6.56±0.67 mg / L of the unmodified cathode system and the 16.46±0.54 mg / L of the SMFC system. Figure 5 Furthermore, the total nitrogen concentration of the SMFC system increased significantly in the initial stage of operation and remained higher than the initial concentration (8.06±0.43 mg / L). These results indicate that electrochemical modification significantly improved the nitrogen removal capacity of the cathode, while emergent plants further enhanced the denitrification effect of the system through the regulation of the rhizosphere microenvironment.

[0049] In phosphorus pollution control, the modified cathode emergent plant-SMFC coupled system demonstrated excellent total phosphorus removal efficiency. After 45 days of operation, the total phosphorus concentration in the water decreased to 0.24±0.06 mg / L, significantly lower than the 0.85±0.07 mg / L of the unmodified cathode system and the 3.35±0.14 mg / L of the SMFC system. Figure 6In contrast, the total phosphorus concentration in the SMFC system increased significantly during operation, ultimately remaining above the initial concentration of 2.01 ± 0.08 mg / L, demonstrating a significant inadequacy in controlling phosphorus pollution. The modified cathode emergent plant-SMFC coupling system not only effectively avoided secondary release of total phosphorus but also significantly enhanced phosphorus removal efficiency. This was attributed to the improvement in cathode catalytic performance due to electrochemical modification, as well as the synergistic enhancement of active phosphorus nutrient absorption by emergent plants and the activity of rhizosphere microorganisms.

[0050] In summary, this invention, based on an emergent plant-SMFC coupling system with a modified cathode, successfully and significantly improves hydrogen peroxide generation efficiency through multiple mechanisms, thereby enhancing the removal rate and efficiency of algal blooms. Furthermore, through the regulation of the rhizosphere microenvironment of emergent plants and the catalytic enhancement effect of the electrochemically modified cathode, this system significantly improves the removal efficiency of ammonia nitrogen, total nitrogen, and total phosphorus in the water, while effectively inhibiting the release of nitrogen and phosphorus nutrients from the sediment. This achieves simultaneous and efficient treatment of algal blooms and pollution control, providing an efficient, green, and sustainable technical solution for aquatic ecological restoration.

Claims

1. A method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells, characterized in that, Includes the following steps: S1, Construct an emergent plant-SMFC coupling system, the emergent plant-SMFC coupling system includes emergent plants and SMFC, the SMFC includes an anode electrode, a modified cathode electrode and an external resistor; plant the emergent plants around the anode electrode so that the anode electrode is in contact with the bottom sediment; S2, Preparation of modified cathode electrode: The cathode electrode is electrochemically oxidized to enhance its catalytic activity. The cathode electrode is made of carbon felt, carbon rod, or carbon cloth. The specific method for preparing the modified cathode electrode is as follows: Using an electrochemical workstation in constant current mode, the cathode electrode is set as the working electrode; a carbon rod is used as the counter electrode, and ammonium fluoride solution is used as the electrolyte; oxidation treatment is performed under constant current conditions, followed by rinsing the cathode electrode with deionized water until neutral, and drying at 55°C for 10 hours to obtain the modified cathode electrode. S3, acclimatizing electroactive microorganisms, acclimatizing the emergent plant-SMFC coupling system at room temperature, and improving the power generation capacity of the anode electrode by introducing bottom sediment rich in organic matter or exogenous inoculated microorganisms; S4: Start and run the system to monitor the changes in chlorophyll a, ammonia nitrogen, total nitrogen and total phosphorus concentrations in the water in real time until the target treatment effect is achieved.

2. The method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells according to claim 1, characterized in that, The anode electrode is a carbon felt, carbon rod, carbon cloth, or carbon particle electrode, which is arranged in the sediment to promote electron transfer by electroactive microorganisms.

3. The method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells according to claim 1, characterized in that, The emergent plants include windmill grass, canna lily, reed, cattail, water bamboo, water onion, calamus, or arrowhead.

4. The method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells according to claim 1, characterized in that, The parameters of the oxidation treatment include: a constant current range of 1~1000mA, an oxidation time of 1~60 minutes, and an ammonium fluoride solution concentration of 1~500mM.

5. The method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells according to claim 1, characterized in that, The modified cathode electrode is positioned at the interface between the algal bloom water and the air to enhance oxygen utilization efficiency and promote hydrogen peroxide generation.

6. The method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells according to claim 1, characterized in that, The external resistor is connected in series with the anode electrode and the modified cathode electrode via a metal wire, and the external resistor is located between the anode electrode and the cathode electrode; the metal wire is platinum wire, titanium wire or stainless steel wire; the resistance value of the external resistor is 0~100000Ω.

7. The method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells according to claim 1, characterized in that, The process of acclimating electroactive microorganisms in S3 specifically involves: slowly injecting the effluent from the anode of a mature microbial fuel cell into the sediment where the anode electrode is located to promote the enhancement of microbial activity, and considering the acclimation to be complete when the anode output voltage increases by less than 5% for two consecutive cycles.

8. The method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells according to claim 1, characterized in that, During system operation in S4, the modified cathode electrode is periodically rinsed with deionized water to remove deposits on the electrode surface, thereby improving electrode performance and system operating efficiency.

9. The method for simultaneous water body remediation using emergent plant-sediment microbial fuel cells according to claim 1, characterized in that, When the system in S4 is running, it monitors the changes in the concentrations of chlorophyll a, ammonia nitrogen, total nitrogen, and total phosphorus in the water in real time, and dynamically adjusts the electrochemical parameters of the cathode electrode and the planting density of emergent plants based on the monitoring results.

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