Electrochemically reinforced constructed wetland system for removing nitrogen and phosphorus under low-temperature condition

Abstract

The utility model relates to an electrochemical enhanced nitrogen and phosphorus removal constructed wetland system under a low-temperature condition, which comprises a descending type subsurface flow constructed wetland, a composite anode and a cathode are sequentially arranged in a substrate layer of the descending type subsurface flow constructed wetland from top to bottom, the composite anode is electrically connected with a positive electrode of a power supply, and the cathode is electrically connected with a negative electrode of the power supply. The composite anode comprises a graphite felt and foam iron which is arranged above the graphite felt and is fixed with the graphite felt, and the cathode adopts the graphite felt. The electrochemical enhanced constructed wetland system has the beneficial effects that the problem of poor nitrogen and phosphorus removal effect under a low-temperature condition can be solved, the influence of weather conditions on the nitrogen and phosphorus removal effect of the system can be weakened, the wetland area is saved, meanwhile, electrons can be provided by electrochemistry, an external carbon source is not needed, secondary pollution is avoided, and the cost is reduced. A new thought is opened for strengthening the artificial wetland technology, and the composite anode solves the problem that an electrode in a current electrochemical strengthening artificial wetland system is difficult to replace.

Description

Technical Field

[0001] The utility model relates to the technical field of artificial wetlands, in particular to an artificial wetland system for electrochemically enhancing nitrogen and phosphorus removal under low-temperature conditions. Background Art

[0002] Constructed wetlands are complex ecological treatment systems composed of a matrix, water, plants, animals, and microorganisms. They primarily remove nitrogen and phosphorus through plant absorption, matrix adsorption and filtration, various chemical reactions within the wetland, and the action of microorganisms. Compared with traditional treatment methods, they not only have the advantages of low construction and operating costs and low energy consumption, but also maintain microbial diversity and provide good ecological and environmental benefits. Therefore, constructed wetland systems have long been regarded as a promising ecological technology. However, because plants and microorganisms are sensitive to temperature, the efficiency of contaminated wetlands in removing pollutants (nitrogen and phosphorus) is significantly reduced in cold or winter regions. Therefore, it is particularly important to improve constructed wetlands to make them more efficient and unaffected by low temperatures. Utility Model Content

[0003] The technical problem to be solved by the present invention is to provide an artificial wetland system for electrochemically enhancing nitrogen and phosphorus removal under low temperature conditions, so as to overcome the deficiencies in the above-mentioned prior art.

[0004] The utility model provides a technical solution for solving the above-mentioned technical problems as follows: an electrochemically enhanced artificial wetland system for denitrification and dephosphorization under low-temperature conditions, comprising: a downward subsurface flow artificial wetland, wherein a composite anode and a cathode are arranged in sequence from top to bottom in the matrix layer of the downward subsurface flow artificial wetland, the composite anode is electrically connected to the positive electrode of the power supply, and the cathode is electrically connected to the negative electrode of the power supply, the composite anode comprises: graphite felt and foam iron arranged above the graphite felt and fixed to the graphite felt, and the cathode is made of graphite felt.

[0005] On the basis of the above technical solution, the present invention can also be improved as follows.

[0006] Furthermore, there are two cathodes, and the two cathodes are distributed up and down, and the cathodes are located in the bottom area of the matrix layer.

[0007] Furthermore, the distance between the two cathodes is 5 cm to 10 cm.

[0008] Furthermore, the thickness of the cathode is 3 mm to 5 mm.

[0009] Furthermore, the diameter of the cathode is 10 cm to 15 cm, and the size of the composite anode is consistent with the size of the cathode.

[0010] Furthermore, the pore diameter of the foamed iron is 1 mm to 2 mm, and the thickness is 1 mm to 2 mm.

[0011] Furthermore, the power source is electrically connected to the solar panel.

[0012] Furthermore, the downward subsurface flow artificial wetland includes: a pool body, in which a substrate layer and a covering soil layer are laid in sequence from bottom to top, emergent plants are planted on the covering soil layer, an outlet is provided on the side of the bottom of the pool body, the thickness of the substrate layer is 40cm to 60cm, and the thickness of the covering soil layer is 3cm to 5cm.

[0013] Furthermore, a water inlet distributor is buried in the covering soil layer.

[0014] Furthermore, crushed stone is used as the matrix layer.

[0015] The beneficial effects of the utility model are:

[0016] 1) When the electrochemically enhanced constructed wetland is in operation, NH4 + -N can be removed not only by direct oxidation at the composite anode or by oxidation of hydroxyl radicals on the surface of the composite anode 2, but also the oxygen generated in the composite anode area can provide an aerobic environment for microorganisms enriched on the graphite felt of the composite anode, which is conducive to the growth and reproduction of nitrifying bacteria, further increasing NH4 + -N removal efficiency, in addition, Fe released from the foam iron in the composite anode 2+ Or the hydration products formed by hydrolysis can react with PO4 in water 3- -P forms a stable precipitate, which can effectively remove phosphorus from water. The graphite felt under the foam iron can intercept the precipitate to avoid clogging when flowing into the medium below;

[0017] The cathode area is located at the bottom. When water flows through the cathode surface, NO3 in the water is directly removed through the reduction reaction. - -N, in addition, the graphite felt cathode 3 has a rich porous structure, which is conducive to the enrichment of microorganisms. The released H2 provides an anaerobic environment and is fully utilized by hydrogen autotrophic denitrifying bacteria, further increasing NO3 - -N removal efficiency. Therefore, the electrochemical enhanced artificial wetland system in this scheme can solve the problem of poor nitrogen and phosphorus removal effects under low temperature conditions, that is, it can reduce the impact of climate conditions on the system's nitrogen and phosphorus removal effects, saving wetland area. At the same time, electrochemistry can also provide electrons, eliminating the need for an external carbon source, avoiding secondary pollution, and opening up new ideas for strengthening artificial wetland technology.

[0018] 2) The composite anode is placed on top, solving the problem of difficult electrode replacement in current electrochemically enhanced constructed wetland systems;

[0019] 3) The dual cathode mode can produce more H2 on the one hand, and the cathode area will form an anaerobic environment and provide electrons for hydrogen autotrophic denitrifying bacteria, which is beneficial to the removal of nitrate nitrogen in the water body. On the other hand, increasing the area of the cathode is more conducive to the direct reduction and removal of nitrate nitrogen in the water body. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of the artificial wetland system for electrochemically enhanced nitrogen and phosphorus removal under low-temperature conditions in the utility model.

[0021] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0022] 1. Downward subsurface flow artificial wetland, 110. Pool body, 111. Water outlet, 120. Matrix layer, 130. Covering soil layer, 140. Emergent plants, 150. Water inlet distributor, 2. Composite anode, 3. Cathode, 4. Power supply, 5. Solar panel. DETAILED DESCRIPTION

[0023] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0024] Example 1

[0025] like Figure 1 As shown, an electrochemically enhanced artificial wetland system for denitrification and phosphorus removal under low-temperature conditions comprises: a downward subsurface flow artificial wetland 1, wherein a composite anode 2 and a cathode 3 are sequentially arranged from top to bottom in a matrix layer 120 of the downward subsurface flow artificial wetland 1, wherein the composite anode 2 is located at the upper part of the downward subsurface flow artificial wetland 1 for easy replacement. The reason why the composite anode 2 is at the upper part and the cathode 3 is at the lower part is that the upper part of the downward subsurface flow artificial wetland 1 is a nitrification reaction requiring oxygen, wherein the composite anode 2 can provide oxygen during operation, and the lower part of the downward subsurface flow artificial wetland 1 is a denitrification reaction requiring an anaerobic environment, wherein the hydrogen generated by the composite anode 2 during operation can create an anaerobic environment, the composite anode 2 is electrically connected to the positive electrode of a power supply 4, and the cathode 3 is electrically connected to the negative electrode of the power supply 4, and the composite anode 2 comprises: graphite felt and foamed iron, wherein the foamed iron is arranged above the graphite felt and fixed to the graphite felt;

[0026] Under low temperature conditions, when the composite anode 2 and cathode 3 are in a powered state and water flows through the surface of the composite anode 2, NH4 + -N can be directly oxidized and removed by the composite anode 2 or by oxidizing and removing the hydroxyl radicals on the surface of the composite anode 2. The reaction that occurs is:

[0027]

[0028] 2NH3+6·OH→N2↑+6H2O 2)

[0029] The composite anode 2 provides an oxygen environment. Oxygen can provide an aerobic environment for microorganisms enriched on the graphite felt of the composite anode 2, which is conducive to the growth and reproduction of nitrifying bacteria. The reactions that occur are:

[0030] 2H2O-4e - →O2↑+4H + 3)

[0031] To further remove NH4 + -N, while the foam iron in the composite anode 2 undergoes oxidation reaction at the anode to form Fe 2+ or hydration products, which react with PO4 in water 3 --P forms a stable precipitate, and the reaction that occurs is:

[0032]

[0033] 4Fe 2+ +10H2O+O2→FeOH3+8H + 5)

[0034]

[0035] Thus, the purpose of phosphorus removal is achieved. The graphite felt on the composite anode 2 is located below the foamed iron and can intercept the iron phosphate precipitation to avoid blockage below the device.

[0036] When water flows through the surface of cathode 3, NO3 is directly removed from the water through reduction reaction. - -N, the reaction that occurs is:

[0037]

[0038] In addition, the graphite felt cathode 3 has a rich and porous structure, which is conducive to the enrichment of microorganisms. The released H2 provides an anaerobic environment and is fully utilized by hydrogen autotrophic denitrifying bacteria. The reaction that occurs is:

[0039] 2H2O+2e - →H2↑+2OH - 9)

[0040] Further increase NO3 - -N removal efficiency, the electrochemical enhanced artificial wetland system in this scheme can solve the problem of poor denitrification and phosphorus removal under low temperature conditions, that is, it can reduce the impact of climatic conditions on the denitrification and phosphorus removal effects of the system and save wetland area. At the same time, electrochemistry can also provide electrons, without the need for an external carbon source, avoiding secondary pollution, and opening up new ideas for strengthening artificial wetland technology.

[0041] Example 2

[0042] like Figure 1 As shown, this embodiment is a further improvement on the basis of embodiment 1, specifically as follows:

[0043] There are two cathodes 3, and the two cathodes 3 are distributed up and down. The dual cathode 3 mode is adopted. On the one hand, more H2 can be produced. The cathode area will form an anaerobic environment and provide electrons for hydrogen autotrophic denitrifying bacteria, which is beneficial to the removal of nitrate nitrogen in the water body. On the other hand, increasing the area of the cathode 3 is more conducive to the direct reduction and removal of nitrate nitrogen in the water body. In addition, due to the dual cathode 3 operation mode, the foam iron in the composite anode 2 will release more Fe 2+ (The current of composite anode 2 is larger, and iron ions are more easily precipitated), which is beneficial to PO4 3- -P removal, the cathode 3 is located in the bottom area of the substrate layer 120 to ensure that the hydrogen released by the cathode 3 is fully utilized by the hydrogen autotrophic denitrifying bacteria and provide an anaerobic environment.

[0044] Furthermore, the distance between the two cathodes 3 is 5 cm to 10 cm, the two cathodes 3 are distributed in parallel, the thickness of the cathode 3 is 3 mm to 5 mm, and the diameter of the cathode 3 is 10 cm to 15 cm.

[0045] The size of the composite anode 2 is consistent with that of the cathode 3 .

[0046] Example 3

[0047] like Figure 1 As shown, this embodiment is a further improvement on the basis of embodiment 1 or 2, specifically as follows:

[0048] The pore size of the foam iron is 1mm to 2mm, and the thickness is 1mm to 2mm. When the system starts running, the foam iron on the composite anode 2 releases Fe 2+ With PO4 in water 3- The -P reaction produces a stable precipitate, and the graphite felt on the composite anode 2 can intercept the precipitate to avoid clogging below.

[0049] Example 4

[0050] like Figure 1 As shown, this embodiment is a further improvement on the basis of any one of the embodiments 1 to 3, and the details are as follows:

[0051] The power supply 4 is electrically connected to the solar panel 5 , which utilizes solar energy to generate electricity and charge the power supply 4 , thereby increasing its battery life and allowing the power supply 4 to operate without the use of mains electricity.

[0052] Example 5

[0053] like Figure 1As shown, this embodiment is a further improvement on the basis of any one of the embodiments 1 to 4, specifically as follows:

[0054] The downward subsurface flow artificial wetland 1 includes: a pool body 110, which can be made of acrylic material. A matrix layer 120 and a covering layer 130 are laid in the pool body 110 from bottom to top. Emergent plants 140 are planted on the covering layer 130. A water outlet 111 is provided on the side of the bottom of the pool body 110. The thickness of the matrix layer 120 is 40cm to 60cm, and the thickness of the covering layer 130 is 3cm to 5cm. A water inlet distributor 150 is buried in the covering layer 130. The water enters the water inlet distributor 150 and is then evenly distributed into the covering layer 130 by the water inlet distributor 150. The matrix layer 120 uses low-cost gravel.

[0055] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are illustrative and cannot be understood as limitations on the present invention. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. An electrochemically enhanced artificial wetland system for nitrogen and phosphorus removal under low temperature conditions, characterized in that: include: A downward subsurface flow artificial wetland (1) is provided. A composite anode (2) and a cathode (3) are sequentially arranged from top to bottom in a matrix layer (120) of the downward subsurface flow artificial wetland (1). The composite anode (2) is electrically connected to the positive electrode of a power supply (4), and the cathode (3) is electrically connected to the negative electrode of the power supply (4). The composite anode (2) comprises: graphite felt and foamed iron arranged above the graphite felt and fixed to the graphite felt. The cathode (3) is made of graphite felt.

2. The electrochemically enhanced artificial wetland system for nitrogen and phosphorus removal under low temperature conditions according to claim 1 is characterized in that: The number of the cathodes (3) is two, and the two cathodes (3) are distributed up and down, and the cathodes (3) are located in the bottom area of the matrix layer (120).

3. The electrochemically enhanced artificial wetland system for nitrogen and phosphorus removal under low temperature conditions according to claim 2 is characterized in that: The distance between the two cathodes (3) is 5 cm to 10 cm.

4. The electrochemically enhanced artificial wetland system for nitrogen and phosphorus removal under low temperature conditions according to claim 1 is characterized in that: The thickness of the cathode (3) is 3 mm to 5 mm.

5. The electrochemically enhanced artificial wetland system for nitrogen and phosphorus removal under low temperature conditions according to claim 4 is characterized in that: The diameter of the cathode (3) is 10 cm to 15 cm, and the size of the composite anode (2) is consistent with the size of the cathode (3).

6. The electrochemically enhanced artificial wetland system for nitrogen and phosphorus removal under low temperature conditions according to claim 1, characterized in that: The pore diameter of the foam iron is 1 mm to 2 mm, and the thickness is 1 mm to 2 mm.

7. The electrochemically enhanced artificial wetland system for nitrogen and phosphorus removal under low temperature conditions according to claim 1, characterized in that: The power source (4) is electrically connected to the solar cell panel (5).

8. The electrochemically enhanced artificial wetland system for nitrogen and phosphorus removal under low temperature conditions according to any one of claims 1 to 7, characterized in that: The downward subsurface flow artificial wetland (1) comprises: a pool body (110), a matrix layer (120) and a covering layer (130) are sequentially laid in the pool body (110) from bottom to top, emergent plants (140) are planted on the covering layer (130), a water outlet (111) is provided on the side of the bottom of the pool body (110), the thickness of the matrix layer (120) is 40 cm to 60 cm, and the thickness of the covering layer (130) is 3 cm to 5 cm.

9. The electrochemically enhanced artificial wetland system for nitrogen and phosphorus removal under low temperature conditions according to claim 8, characterized in that: A water inlet distributor (150) is embedded in the covering soil layer (130).

10. The electrochemically enhanced artificial wetland system for nitrogen and phosphorus removal under low temperature conditions according to claim 8, characterized in that: The matrix layer (120) is made of crushed stone.

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