An in-situ purification device and method for denitrification and carbon reduction in water bodies

Abstract

This invention discloses an in-situ purification device and method for denitrification and carbon reduction in water bodies. The device includes an overlying water zone and a sediment zone, with the overlying water zone positioned above the sediment zone. The overlying water zone includes: (1) multiple aerobic cathode plates arranged vertically in parallel and (2) multiple anaerobic cathode plates arranged vertically in parallel. The multiple aerobic cathode plates and the multiple anaerobic cathode plates are arranged adjacently and alternately to form an S-shaped channel. An aeration pipe is provided at the lower edge of the aerobic cathode plate. Wetland sediment is laid in the sediment zone, and an anode is buried in the wetland sediment. The anode forms a circuit with the multiple aerobic cathode plates and the multiple anaerobic cathode plates through a circuit. Water flows in sequence to contact the aerobic cathode and the anaerobic cathode, and the water quality is purified through repeated aerobic-anaerobic processes. This device can purify pollutants such as ammonium nitrogen, nitrate nitrogen, and COD in wetland water bodies in situ. The removal process does not generate secondary pollution. The device has a simple structure and low construction and operating costs.

Description

Technical Field

[0001] This invention belongs to the field of ecological and environmental protection technology, specifically relating to an in-situ purification device and method for denitrification and carbon reduction of water bodies. Background Technology

[0002] Wetlands, including rivers, ditches, ponds, lakes, marshes, and shallow seas, are susceptible to agricultural non-point source pollution and often contain high levels of pollutants such as ammonium nitrogen, nitrate nitrogen, and COD. These pollutants can lead to eutrophication, resulting in large-scale cyanobacterial blooms. Currently, relatively mature treatment technologies for these pollutants include phytoremediation (plant-based constructed wetland purification), biosorbents (activated carbon and biochar), and biofilm reactors. However, these technologies face certain obstacles in application. Phytoremediation requires consideration of environmental factors, such as whether pH, temperature, and light conditions are suitable for plant growth; additionally, introducing exotic plants may disrupt the local ecosystem. Biosorbents may suffer from particle loss during use, and their regeneration process involves high energy consumption and costs. As for biofilm reactors, their operation requires regular management of the biofilm to prevent secondary pollution from biofilm shedding. Due to the high cost and complex management of these technologies, large-scale application faces challenges.

[0003] Microbial fuel cells (MFCs) are widely used in environmental monitoring and remediation due to their sustainability. Current research on ammonium nitrogen removal using MFCs mostly employs a dual-chamber structure (Chemosphere, 2023, 138388), requiring microorganisms to be inoculated at the cathode or anode. The oxidation by nitrifying bacteria converts ammonium nitrogen into nitrite, which is then converted into nitrogen gas at the cathode, thus achieving ammonium nitrogen removal. However, dual-chamber MFCs require inoculation and cultivation of microorganisms, making operation difficult and costly, suitable only for laboratory research and not applicable to in-situ wetland water purification. Deng Huan et al. (Catena, 2019, 172:572-580) found that aquatic sediments generally contain a large number of electrogenic bacteria, with up to 100 million cells per gram of sediment, mainly belonging to the genus *Geobacterium* (Geobacterium). Geobacter Clostridium ( Clostridium ), Pseudomonas spp. Pseudomonas ) and Trichomonas vaginalis ( Comamonas By embedding anodes in sediments, indigenous electrogenic bacteria can collect electrons generated from the decomposition of organic matter and transmit them via wires to a cathode located in the overlying water, thus forming a sediment microbial fuel cell. Therefore, this invention designs a single-chamber in-situ water denitrification and carbon reduction device utilizing indigenous electrogenic bacteria in wetland sediments. Summary of the Invention

[0004] To address the drawbacks of existing technologies for removing pollutants from wetland water bodies, such as high costs and complex management, this invention provides an in-situ purification device and method for denitrification and carbon reduction in water bodies.

[0005] The technical solution adopted in this invention is as follows:

[0006] An in-situ purification device for denitrification and carbon reduction in water includes an overlying water zone and a sediment zone, wherein the overlying water zone is located above the sediment zone.

[0007] The water-covered area includes: (1) a plurality of aerobic cathode plates arranged vertically in parallel, with the ends of adjacent aerobic cathode plates on the same side fixedly connected by a first connecting plate arranged vertically; and (2) a plurality of anaerobic cathode plates arranged vertically in parallel, with the ends of adjacent anaerobic cathode plates on the same side fixedly connected by a second connecting plate arranged vertically; the plurality of aerobic cathode plates and the plurality of anaerobic cathode plates are arranged adjacently and alternately to form an S-shaped channel;

[0008] Wetland sediment is laid in the sediment area, and an anode is buried in the wetland sediment. The anode forms a circuit with the plurality of aerobic cathode plates and the plurality of anaerobic cathode plates through a circuit.

[0009] A resistor and a multimeter are connected in parallel between the anode and the plurality of aerobic cathode plates, and between the anode and the plurality of anaerobic cathode plates;

[0010] An aeration pipe is provided at the lower edge of the aerobic cathode plate.

[0011] Furthermore, the aerobic cathode plate and the first connecting plate are at the same height.

[0012] Furthermore, the anaerobic cathode plate and the second connecting plate are at the same height.

[0013] Furthermore, the aerobic cathode plate and / or the anaerobic cathode plate are made of one of the following materials: carbon felt, graphite felt, carbon cloth, stainless steel mesh, or titanium mesh.

[0014] Furthermore, the anode is made of one of the following materials: carbon felt, graphite felt, carbon cloth, stainless steel mesh, or titanium mesh.

[0015] Furthermore, the first connecting plate and / or the second connecting plate are made of one of the following materials: carbon felt, stainless steel, or graphite felt.

[0016] Furthermore, the aeration pipe is made of one of the following materials: polypropylene, rubber, polyvinyl chloride, or polyurethane.

[0017] Furthermore, the wetland sediment originates from rivers, ditches, ponds, lakes, swamps, and shallow seas.

[0018] The method for treating polluted water using the above-mentioned in-situ purification device includes the following steps:

[0019] Step 1: Lay wetland sediment in the sediment area, and then bury the anode in the wetland sediment;

[0020] Step 2: Fix several aerobic cathode plates to the first connecting plate and arrange them in parallel with the direction of water flow in the overlying water area. Lay aeration pipes at the lower edge of the aerobic cathode plates. Fix several anaerobic cathode plates to the second connecting plate and arrange them in parallel with the direction of water flow in the overlying water area. They are arranged adjacent to and staggered with the aerobic cathode plates to form an S-shaped channel.

[0021] Step 3: Connect the anode to the aerobic cathode plate and the anaerobic cathode plate respectively through wires and an external resistor; connect a multimeter in parallel with the external resistor, and the displayed voltage data indicates that the system is operating normally;

[0022] Step 4: Add the wastewater to be treated to the overlying water area, and the water flows into contact with the aerobic cathode plate and the anaerobic cathode plate in sequence. Air is introduced into the water near the aerobic cathode plate through the aeration pipe to create an aerobic environment, thereby forming hydrogen peroxide on the surface of the aerobic cathode plate. The strong oxidizing property of hydrogen peroxide promotes the formation of ammonium nitrogen (NH4+) in the overlying water. + ) is converted into nitrate nitrogen (NO3) - ) and the oxidation and decomposition of organic matter; while the anaerobic cathode plate is in an anaerobic environment, which is conducive to NO3 - Nitrogen removal is achieved by gaining electrons on the cathode surface and anaerobic denitrifying into nitrogen gas (N2). The water body is purified through repeated aerobic-anaerobic processes.

[0023] The in-situ purification device provided by this invention utilizes indigenous electrogenic bacteria in wetland sediments to decompose organic matter and generate electrons. These electrons flow through a wire to the cathode, where they react with dissolved oxygen in the water under aerobic conditions to produce water (H2O) and hydrogen peroxide (H2O2). The strong oxidizing properties of H2O2 promote the conversion of ammonium nitrogen in the water into nitrate nitrogen and COD. Under anaerobic conditions, nitrate nitrogen in the water gains electrons on the cathode surface and is reduced to nitrogen gas, thus achieving denitrification. By alternately setting aerobic and anaerobic cathodes, comprehensive removal of ammonium nitrogen, nitrate nitrogen, and COD from wetland water is achieved.

[0024] This invention requires no inoculation with microorganisms, is simple to operate, and can achieve in-situ purification; at the same time, the purification process does not add any chemical reagents and does not produce secondary pollution; it can effectively solve the pollution problems of ammonium nitrogen, nitrate nitrogen and COD that are common in wetland water bodies with low cost and energy consumption, and achieve water quality purification. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the in-situ purification device for denitrification and carbon reduction in water according to the present invention. Wherein: 1 is the anode, 2 is the aerobic cathode plate, 3 is the aeration pipe, 41 is the first connecting plate, 42 is the second connecting plate, 5 is the anaerobic cathode plate, 6 is a resistor, and 7 is a multimeter. Detailed Implementation

[0026] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0028] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. Example 1

[0029] Seawater samples from Yancheng were placed in a small water tank (2 m × 0.8 m × 0.5 m). A carbon felt anode (1 m × 0.5 m) was completely buried in the bottom sediment, with a titanium wire lead-out. Five carbon felt anodes (0.4 m × 0.4 m each) were selected for both aerobic and anaerobic cathodes, and were fixed parallel to each other on two stainless steel connecting plates 1.5 m long and 0.5 m wide. The aerobic and anaerobic cathode plates were arranged adjacently and alternately to form an S-shaped channel and were vertically fixed in the water. An aeration pipe was laid below the aerobic cathode. A titanium wire was then led out from each of the aerobic and anaerobic cathodes. The anode was connected to the aerobic and anaerobic cathodes respectively through the titanium wire and a 1 kΩ external resistor, and the voltage data across the resistor was recorded using a multimeter. A multichannel electrochemical workstation was used to apply a voltage of 0.5 V to the aerobic cathode, and a peristaltic pump circulated the water covering the tank at a flow rate of 0.35 mL / min to simulate the water flow conditions of a river. After the multimeter voltage reading stabilized, the overlying water was replaced with artificial wastewater containing 50 mg / L ammonium nitrogen and 10 mg / L nitrate nitrogen. The purification device ran continuously for 5 days, with aeration for 1 hour at a rate of 0.2 L / min through the aeration pipe at 9:00 AM each day. After the operation, the removal rates were measured to be 57.8% for ammonium nitrogen, 45.7% for nitrate nitrogen, and 71.3% for COD. Example 2

[0030] A miniature pond measuring 2m long, 2m wide, and 1.2m deep within Nanjing Normal University was selected as the experimental site. The pond had an inlet and an outlet. Graphite felt anodes (0.8m × 0.8m) were completely buried in the pond bottom mud, with titanium wires leading out. Five graphite felts (0.6m × 0.6m) were used as electrode materials for both aerobic and anaerobic cathodes, fixed to two stainless steel connecting plates 1m long and 0.6m wide. The aerobic and anaerobic cathode plates were arranged alternately and adjacently, with aeration pipes installed at the lower edge of the aerobic cathode. The anodes were then connected to both the aerobic and anaerobic cathodes via titanium wires and a 1kΩ external resistor, and the voltage across the resistor was recorded using a multimeter. Water flowing from the pond outlet was then pumped back to the inlet using a peristaltic pump. Before the experiment, the concentrations of ammonium nitrogen, nitrate nitrogen, and COD in the water were measured to be 6.48 mg / L, 4.89 mg / L, and 45 mg / L, respectively. A peristaltic pump was then used to circulate the pond water through the purification device. The purification device operated continuously for 7 days. After the experiment, the removal rates of ammonium nitrogen, nitrate nitrogen, and COD in the water were measured to be 68%, 51.6%, and 75.8%, respectively.

Claims

1. A method for treating polluted water bodies using an in-situ purification device for denitrification and carbon reduction, characterized in that, Includes the following steps: Step 1: Lay wetland sediment in the sediment area, and then bury the anode in the wetland sediment; Step 2: Fix multiple aerobic cathode plates to the first connecting plate and arrange them in parallel in the direction perpendicular to the water flow in the overlying water area. Lay aeration pipes at the lower edge of the aerobic cathode plates. Fix multiple anaerobic cathode plates to the second connecting plate and arrange them in parallel in the direction perpendicular to the water flow in the overlying water area. They are arranged adjacent to and staggered with the aerobic cathode plates to form an S-shaped channel. Step 3: Connect the anode to the aerobic cathode plate and the anaerobic cathode plate respectively through wires and an external resistor. Connect the multimeter in parallel with the external resistor. If the voltage data is displayed, it indicates that the device is operating normally. Step 4: The wastewater to be treated is added to the overlying water area, and the water flows into contact with the aerobic cathode plate and the anaerobic cathode plate in sequence. Air is introduced into the water near the aerobic cathode plate through the aeration pipe to create an aerobic environment, thereby forming hydrogen peroxide on the surface of the aerobic cathode plate. The strong oxidizing property of hydrogen peroxide promotes the conversion of ammonium nitrogen in the overlying water into nitrate nitrogen and the oxidative decomposition of organic matter. Meanwhile, the anaerobic cathode plate is in an anaerobic environment, which is conducive to the formation of NO3. - Nitrogen is removed by gaining electrons on the cathode surface and undergoing anaerobic denitrification into nitrogen gas. The water is purified through repeated aerobic-anaerobic processes. The in-situ purification device for denitrification and carbon reduction of water includes an overlying water zone and a sediment zone, with the overlying water zone located above the sediment zone. The overlying water area includes: Multiple aerobic cathode plates (2) are arranged in parallel vertically, and adjacent aerobic cathode plates (2) are fixedly connected at the ends on the same side by a first connecting plate (41) arranged vertically. Multiple anaerobic cathode plates (5) are arranged vertically in parallel, and adjacent anaerobic cathode plates (5) are fixedly connected at the ends on the same side by a vertically arranged second connecting plate (42); The multiple aerobic cathode plates (2) and the multiple anaerobic cathode plates (5) are arranged adjacently and alternately to form an S-shaped channel; Wetland sediment is laid in the sediment area, and an anode (1) is buried in the wetland sediment. The anode forms a circuit with the plurality of aerobic cathode plates (2) and the plurality of anaerobic cathode plates (5) through a line. A resistor (6) and a multimeter (7) are arranged in parallel between the anode (1) and the plurality of aerobic cathode plates (2) and between the anode (1) and the plurality of anaerobic cathode plates (5). An aeration pipe (3) is provided at the lower edge of the aerobic cathode plate (2).

2. The method according to claim 1, characterized in that, The aerobic cathode plate (2) and the first connecting plate (41) are at the same height.

3. The method according to claim 1, characterized in that, The anaerobic cathode plate (5) and the second connecting plate (42) are at the same height.

4. The method according to claim 1, characterized in that, The aerobic cathode plate (2) and / or the anaerobic cathode plate (5) are made of one of the following materials: carbon felt, graphite felt, carbon cloth, stainless steel mesh, or titanium mesh.

5. The method according to claim 1, characterized in that, The anode (1) is made of one of the following materials: carbon felt, graphite felt, carbon cloth, stainless steel mesh or titanium mesh.

6. The method according to claim 1, characterized in that, The first connecting plate (41) and / or the second connecting plate (42) are made of carbon felt, stainless steel or graphite felt.

7. The method according to claim 1, characterized in that, The aeration pipe (3) is made of one of polypropylene, rubber, polyvinyl chloride or polyurethane.

8. The method according to claim 1, characterized in that, The wetland sediments originate from rivers, ditches, ponds, lakes, swamps, and shallow seas.

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