Constructed wetland deep denitrification system and application thereof

Abstract

The invention belongs to the technical field of sewage treatment systems, and particularly relates to a constructed wetland deep denitrification system and application thereof. The constructed wetland deep denitrification system provided by the invention comprises a vertical flow constructed wetland bed body, the vertical flow constructed wetland bed body is divided into a nitrification area above the water line and a denitrification area below the water line by the water line; a plurality of shunting micro units are arranged in the nitrification area; each shunting micro-unit comprises a mixed clay layer and biological carbon positioned on the mixed clay layer; a plurality of water inlet pipes are laid on the upper surface of the nitrification area; a plurality of water inlet holes are formed in each water inlet pipe; a plurality of water outlet pipes are laid at the bottom of the denitrification area, and each water outlet pipe is provided with a plurality of water outlet holes; wetland plants are planted on the vertical flow artificial wetland bed body; the nitration area is filled with an inorganic filler; the denitrification area is filled with an inorganic filler and biological carbon; the system provided by the invention can effectively improve the deep denitrification capacity of the constructed wetland.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment systems, and particularly relates to an artificial wetland deep denitrification system and its application. Background Art

[0002] Pig farm wastewater is usually treated by biochemical methods due to its large water volume and high concentrations of organic matter, ammonia nitrogen, total nitrogen, phosphorus, etc. During actual operation, by reasonably controlling operating conditions such as aeration and reflux ratio in the biochemical system, good nitrification effects can be achieved, and the ammonia nitrogen concentration in the effluent can usually be controlled below 10 mg / L, meeting the corresponding national and local discharge standards (15 - 80 mg / L). However, during aerobic nitrification, a large amount of aeration accelerates the consumption of organic matter by aerobic microorganisms, resulting in insufficient carbon sources in the subsequent denitrification process and difficulty in further reducing the nitrate concentration, causing the total nitrogen concentration in the system effluent to remain high. The total nitrogen concentration in the tail water of conventional pig farm wastewater biochemical treatment systems is generally 50 - 150 mg / L, and even for the effluent of highly efficient denitrification processes, the total nitrogen concentration mostly ranges between 50 - 80 mg / L. However, in key river basins and ecologically sensitive areas in China, the total nitrogen discharge standard is 15 - 50 mg / L, making it difficult to meet the total nitrogen standard for the biochemical treatment tail water.

[0003] To further reduce the total nitrogen concentration in the biochemical treatment tail water, common methods mainly include adjusting the biochemical treatment operation process (such as adding carbon sources to the biochemical system), chemical precipitation of the tail water, adding subsequent denitrification filters and artificial wetlands, etc. Among them, the first three methods require continuous dosing of chemicals, regular replacement of functional fillers, and thus generate power consumption during use, with high operating costs and prone to instability of the microbial system; while artificial wetlands mainly create aerobic and anoxic environments through the combined action of plants, fillers, and microorganisms, and can spontaneously complete the nitrification and denitrification processes with low operating costs, which is an effective solution for the deep denitrification of pig farm wastewater biochemical treatment tail water.

[0004] However, current artificial wetlands are mostly used to treat rural domestic sewage, the tail water of urban sewage treatment plants, non-point source pollution, and slightly polluted river water bodies, etc. How to enhance the high-efficiency denitrification ability of artificial wetlands is a difficult problem in the industry for solving the deep denitrification and quality improvement of pig farm wastewater. Summary of the Invention

[0005] The purpose of the invention is to provide an artificial wetland deep denitrification system and its application, and the artificial wetland deep denitrification system provided by the invention can effectively improve the deep denitrification ability of artificial wetlands.

[0006] To achieve the above purpose, the invention provides the following technical solutions:

[0007] The present invention provides an artificial wetland deep denitrification system, including a vertical flow artificial wetland bed body; the vertical flow artificial wetland bed body includes a nitrification zone 1 above the water level line 8 and a denitrification zone 2 below the water level line 8;

[0008] The nitrification zone 1 is filled with inorganic fillers 9 and is provided with a plurality of shunt micro-units 10; each shunt micro-unit 10 includes a mixed clay layer 11 and biochar 12 located on the mixed clay layer 11;

[0009] The upper surface of the nitrification zone 1 is paved with a plurality of inlet pipes 3; each inlet pipe 3 is provided with a plurality of inlet holes 5;

[0010] The bottom of the denitrification zone 2 is paved with a plurality of outlet pipes 4, and each outlet pipe 4 is provided with a plurality of outlet holes 6; the denitrification zone 2 is filled with inorganic fillers 9 and biochar 12;

[0011] Wetland plants 7 are planted on the vertical flow artificial wetland bed body.

[0012] Preferably, the volume ratio of the inorganic filler 9 to the biochar 12 in the denitrification zone 2 is 3:2; the particle sizes of the inorganic filler 9 and the biochar 12 are independently 3-8 mm.

[0013] Preferably, the mixed clay layer 11 is a cylindrical clay-based material with a diameter of 10-15 cm and a thickness of 3-5 cm.

[0014] Preferably, the clay-based material includes clay and inorganic filler; in the clay-based material, the volume ratio of clay to inorganic filler is 7:3-5:5.

[0015] Preferably, in the shunt micro-unit 10, the biochar 12 is presented in the form of a biochar layer; the thickness of the biochar layer is 5-10 cm.

[0016] Preferably, in the depth direction of the nitrification zone 1, a layer of shunt micro-unit 10 is arranged every 20-30 cm; in the horizontal direction of the nitrification zone 1, the shunt micro-units 10 are arranged in a plum blossom shape.

[0017] Preferably, in the horizontal direction, the interval distance between every two inlet pipes 3 is 30-60 cm; the pipe diameter of each inlet pipe is 2-10 cm; in the horizontal direction, the interval distance between every two outlet pipes 4 is 30-60 cm; the pipe diameter of each outlet pipe is 5-15 cm.

[0018] The present invention also provides the application of the artificial wetland deep denitrification system described in the above technical solution in treating the biochemical treatment tail water of pig breeding wastewater.

[0019] The present invention also provides a method for treating the biochemical treatment tail water of pig breeding wastewater by using the constructed wetland deep denitrification system described in the above technical solution, including the following steps:

[0020] The biochemical treatment tail water of pig breeding wastewater enters the nitrification zone 1 of the constructed wetland through the water inlet holes 5 distributed on the water inlet pipe 3. In the nitrification zone 1, the water flow flows downward along the pores of the inorganic filler 9. After being shunted by the shunt micro-unit 10, the flow path of the water flow in the nitrification zone 1 is increased, and an anoxic environment containing water is formed around the biological carbon 12 on the shunt micro-unit 10, so that nitrification reaction and denitrification reaction occur alternately in the nitrification zone 1; the denitrification reaction is carried out in the denitrification zone 2, and the effluent is discharged from the outlet pipe 4; the oxygen required for the nitrification reaction is provided by atmospheric reoxygenation and wetland plants.

[0021] Preferably, the mass concentration ratio of ammonia nitrogen to nitrate nitrogen in the biochemical treatment tail water of pig breeding wastewater ≤ 1:3;

[0022] When the mass concentration ratio of ammonia nitrogen to nitrate nitrogen in the biochemical treatment tail water of pig breeding wastewater is 1:3 - 1:4, the water level is controlled by adjusting the height of the end of the outlet pipe 4, so that the height ratio of the nitrification zone 1 to the denitrification zone 2 is 1:1;

[0023] When the mass concentration ratio of ammonia nitrogen to nitrate nitrogen in the biochemical treatment tail water of pig breeding wastewater is less than 1:4, the water level is controlled by adjusting the height of the end of the outlet pipe 4, so that the height ratio of the nitrification zone 1 to the denitrification zone 2 is 1:2.

[0024] The present invention provides an artificial wetland deep nitrogen removal system, comprising a vertical flow artificial wetland bed body; the vertical flow artificial wetland bed body includes a nitrification zone 1 above the water level line 8 and a denitrification zone 2 below the water level line 8; the nitrification zone 1 is filled with inorganic fillers 9 and is provided with a plurality of shunt micro-units 10; each shunt micro-unit 10 includes a mixed clay layer 11 and biochar 12 located on the mixed clay layer 11; the upper surface of the nitrification zone 1 is paved with a plurality of inlet pipes 3; each inlet pipe 3 is provided with a plurality of water inlet holes 5; the bottom of the denitrification zone 2 is paved with a plurality of outlet pipes 4, and each outlet pipe 4 is provided with a plurality of water outlet holes 6; the denitrification zone 2 is filled with inorganic fillers 9 and biochar 12; wetland plants 7 are planted on the vertical flow artificial wetland bed body. In the present invention, the shunt micro-units distributed in the nitrification zone can effectively increase the flow path of water flow in the nitrification zone. On the one hand, it effectively extends the hydraulic retention time, enhances the nitrification effect, and promotes the conversion of ammonia nitrogen to nitrate nitrogen; on the other hand, the high water retention performance of the biochar on the shunt micro-units increases the denitrification effect, shortens the mass transfer path, is conducive to reducing the time required to achieve nitrification-denitrification, and maintains the stability of the pH value in the system (the nitrification process consumes alkalinity and causes the pH value to decrease, but the organic matter in the biochar can promote the denitrification process, and the denitrification process generates alkalinity, causing the pH value to rise, thereby playing a role in stabilizing the pH value), improving the treatment efficiency, and thus strengthening the deep nitrogen removal ability of the artificial wetland. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is a sectional view of the artificial wetland deep nitrogen removal system, wherein, 1 - nitrification zone; 2 - denitrification zone; 3 - inlet pipe; 4 - outlet pipe; 5 - water inlet hole; 6 - water outlet hole; 7 - wetland plant; 8 - water level line; 9 - inorganic filler; 10 - shunt micro-unit; 11 - mixed clay layer; 12 - biochar;

[0027] Figure 2 It is a plan view of the artificial wetland deep nitrogen removal system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The present invention provides an artificial wetland deep nitrogen removal system, comprising a vertical flow artificial wetland bed body; the vertical flow artificial wetland bed body includes a nitrification zone 1 above the water level line 8 and a denitrification zone 2 below the water level line 8;

[0029] The nitrification zone 1 is filled with inorganic fillers 9 and is provided with a plurality of shunt micro-units 10; each shunt micro-unit 10 includes a mixed clay layer 11 and biochar 12 located on the mixed clay layer 11;

[0030] On the upper surface of the nitrification zone 1, a plurality of water inlet pipes 3 are laid; each water inlet pipe 3 is provided with a plurality of water inlet holes 5;

[0031] At the bottom of the denitrification zone 2, a plurality of water outlet pipes 4 are laid, and each water outlet pipe 4 is provided with a plurality of water outlet holes 6; the denitrification zone 2 is filled with inorganic fillers 9 and biochar 12;

[0032] Wetland plants 7 are planted on the vertical-flow constructed wetland bed body.

[0033] As an embodiment of the present invention, the constructed wetland deep nitrogen removal system includes a vertical-flow constructed wetland bed body. As an embodiment of the present invention, wetland plants 7 are planted on the vertical-flow constructed wetland bed body; the wetland plants 7 include at least one of reed, cattail and canna.

[0034] As an embodiment of the present invention, the vertical-flow constructed wetland bed body includes a nitrification zone 1 above the water level line 8 and a denitrification zone 2 below the water level line 8.

[0035] As an embodiment of the present invention, a plurality of water inlet pipes 3 are laid on the upper surface of the nitrification zone 1; the diameter of each water inlet pipe is 2-10 cm; each water inlet pipe 3 is provided with a plurality of water inlet holes 5. As an embodiment of the present invention, in the horizontal direction, the interval distance between every two water inlet pipes can be 30-60 cm, specifically 50 cm; the distance between every two water inlet holes in each water inlet pipe can be 15-30 cm, specifically 20 cm.

[0036] As an embodiment of the present invention, the nitrification zone 1 is filled with inorganic fillers 9; the inorganic fillers 9 may include one or several of quartz sand, zeolite and limestone.

[0037] As an embodiment of the present invention, the nitrification zone 1 is provided with a plurality of shunt micro-units 10; the layout mode of the shunt micro-units 10 can be: in the depth direction of the nitrification zone 1, a layer of shunt micro-units 10 is arranged every 20-30 cm; in the horizontal direction of the nitrification zone 1, the shunt micro-units 10 are arranged in a plum blossom shape, and the center distance between adjacent shunt micro-units 10 can be 30-50 cm, specifically 40 cm. In the embodiment of the present invention, specifically, two layers of shunt micro-units are taken as an example for illustration, wherein the first layer of shunt micro-units 10 is located directly below the water inlet holes 5, and the second layer of shunt micro-units is arranged staggeredly with the first layer of shunt micro-units.

[0038] As an embodiment of the present invention, each flow splitting micro-unit 10 includes a mixed clay layer 11. As an embodiment of the present invention, the mixed clay layer 11 is a cylindrical mixed clay layer with a diameter of 10 - 15 cm and a thickness of 3 - 5 cm. Specifically, the diameter of the mixed clay layer 11 can be 10 cm and the thickness can be 4 cm. As an embodiment of the present invention, the mixed clay layer 11 includes clay and inorganic filler; the volume ratio of the clay to the inorganic filler can be 7:3 - 5:5, specifically 7:3, 7:4, 7:5 or 5:5. In the present invention, the clay has water-proof property, and has weak water-permeable property after being mixed with inorganic filler. Thus, after the water flow reaches the flow splitting micro-unit, a part of the water flow can turn, changing the water flow direction, and another part of the water flow slowly penetrates through the mixed clay layer, thereby forming a complex flow path in the nitrification zone and avoiding the occurrence of short circuit. When treating sewage, the setting of the mixed clay layer can effectively increase the flow path of the water flow in the nitrification zone, thereby prolonging the hydraulic retention time, ensuring sufficient contact with nitrifying bacteria, and promoting the conversion of ammonia nitrogen to nitrate nitrogen.

[0039] As an embodiment of the present invention, each flow splitting micro-unit 10 includes biochar 12 located on the mixed clay layer 11; the particle size of the biochar 12 can be 3 - 8 mm; the biochar 12 is presented in the form of a biochar layer in the flow splitting micro-unit 10, and the thickness of the biochar layer can be 5 - 10 cm, specifically 6 cm. In the present invention, in addition to providing a carbon source for the denitrification process, the biochar also has good water-holding capacity, forming an anoxic environment with high water content above the mixed clay layer, which is beneficial to the occurrence of denitrification, and thus can denitrify the generated nitrate into nitrogen in time.

[0040] In summary, on the one hand, the flow splitting micro-unit can make the water flow turn, change the water flow direction, form a complex flow path in the nitrification zone, achieve the purpose of flow splitting, and realize sufficient nitrification; on the other hand, the flow splitting micro-unit can form an anoxic microenvironment, provide a carbon source, and promote the denitrification function in the nitrification zone.

[0041] As an embodiment of the present invention, the denitrification zone 2 is filled with inorganic filler 9 and biochar; the inorganic filler in the denitrification zone 2 is dispersed in the biochar; the volume ratio of the inorganic filler 9 to the biochar 12 in the denitrification zone 2 can be 3:2; the particle sizes of the inorganic filler 9 and the biochar 12 are independently 3 - 8 mm. As an embodiment of the present invention, microorganisms are attached to the inorganic filler 9.

[0042] As an embodiment of the present invention, a plurality of outlet pipes 4 are laid at the bottom of the denitrification zone 2, and the pipe diameter of each outlet pipe is 5-15 cm; each outlet pipe is provided with a plurality of water outlet holes 6. As an embodiment of the present invention, in the horizontal direction, the interval distance between every two outlet pipes can be 30-60 cm; the distance between every two water outlet holes in each outlet pipe can be 15-30 cm.

[0043] The present invention provides a method for treating the biochemical treatment tail water of pig breeding wastewater by using the artificial wetland deep denitrification system described in the above technical solution, including the following steps:

[0044] The biochemical treatment tail water of pig breeding wastewater enters the artificial wetland nitrification zone 1 from the water inlet holes 5 distributed on the inlet pipe 3. In the nitrification zone 1, the water flow flows downward along the pores of the inorganic filler 9, and is shunted by the shunt micro-unit 10 to increase the flow path of the water flow in the nitrification zone 1, and an anoxic environment containing water is formed around the biological carbon 12 on the shunt micro-unit 10, so that nitrification reaction and denitrification reaction occur alternately in the nitrification zone 1; the denitrification reaction is carried out in the denitrification zone 2, and the effluent is discharged by the outlet pipe 4; the oxygen required for the nitrification reaction is provided by atmospheric reoxygenation and wetland plants.

[0045] As an embodiment of the present invention, the mass concentration ratio of ammonia nitrogen to nitrate nitrogen in the biochemical treatment tail water of pig breeding wastewater is ≤1:3; when the mass concentration ratio of ammonia nitrogen to nitrate nitrogen in the biochemical treatment tail water of pig breeding wastewater is 1:3-1:4, the water level is controlled by adjusting the height of the end of the outlet pipe 4, so that the height ratio of the nitrification zone 1 to the denitrification zone 2 is 1:1; when the mass concentration ratio of ammonia nitrogen to nitrate nitrogen in the biochemical treatment tail water of pig breeding wastewater is <1:4, the water level is controlled by adjusting the height of the end of the outlet pipe 4, so that the height ratio of the nitrification zone 1 to the denitrification zone 2 is 1:2.

[0046] Specifically, the process of alternately occurring nitrification and denitrification reactions in the present invention is as follows: after the biochemical treatment tail water of pig breeding wastewater enters the artificial wetland nitrification zone 1 from the water inlet holes 5 distributed on the inlet pipe 3, the water flow flows downward along the pores of the inorganic filler 9 to the shunt micro-unit 10. This process is an aerobic process, and nitrification reaction occurs under the action of nitrifying bacteria, converting ammonia nitrogen into nitrate nitrogen.

[0047] Subsequently, after the water flow contacts the biological carbon 12, the pores of the biological carbon 12 particles are filled with water under the action of capillary water, thereby forming an anoxic environment, which is conducive to the enrichment of denitrifying bacteria, and denitrification occurs here, converting a part of nitrate nitrogen into nitrogen gas. At the same time, the water flow direction is turned under the barrier of the mixed clay layer 11 and enters the nitrification zone again for nitrification reaction, so that a complex flow path is formed in the nitrification zone, and nitrification and denitrification reactions occur alternately.

[0048] The water flow reaches the denitrification zone 2, where denitrification reaction occurs, and the effluent is discharged through the outlet pipe 4.

[0049] Specifically, the denitrification process is as follows:

[0050] After the biochemical treatment tail water of pig breeding wastewater completes the nitrification process in the nitrification zone 1, the ammonia nitrogen in the tail water is converted into nitrate nitrogen. At the same time, a part of the nitrate nitrogen is denitrified into nitrogen gas, and the remaining nitrate nitrogen continues to flow downward into the denitrification zone 2. The denitrification zone 2 is located below the water level line 8 and is in a submerged anoxic state, which is conducive to the enrichment of denitrifying bacteria. At the same time, the biochar mixed in the filler of the denitrification zone can provide a carbon source for the denitrification process, realizing the efficient conversion of nitrate nitrogen into nitrogen gas. After the denitrification process is completed, the effluent enters the outlet pipe 4 through the outlet hole 6 and is discharged from the constructed wetland system.

[0051] The constructed wetland deep denitrification system provided by the present invention can remove ammonia nitrogen and nitrate nitrogen in water simultaneously, thereby reducing the total nitrogen concentration.

[0052] To further illustrate the present invention, the solutions of the present invention will be described in detail below in conjunction with the drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0053] Embodiment 1

[0054] Using Figure 1 The constructed wetland deep denitrification system shown in the figure to treat the biochemical treatment tail water of pig breeding wastewater. The ammonia nitrogen concentration in the biochemical treatment tail water of pig breeding wastewater is 20 mg / L, and the nitrate nitrogen concentration is 60 mg / L. At this time, the concentration ratio of ammonia nitrogen to nitrate nitrogen is 1:3.

[0055] The effective depth of the vertical flow constructed wetland bed is 1 m, of which the depth of the nitrification zone is 0.5 m and the depth of the denitrification zone is 0.5 m; wetland plants such as reed, cattail, and canna are planted on the vertical flow constructed wetland; the granular inorganic filler filled in the constructed wetland bed is quartz sand, and the average particle size of the quartz sand is 5 mm;

[0056] In the horizontal direction of the nitrification zone, the interval distance between every two inlet pipes is 50 cm; the distance between every two inlet holes distributed on each inlet pipe is 20 cm, and the diameter of the inlet hole is 5 cm. In the horizontal direction of the denitrification zone, the interval distance between every two outlet pipes is 50 cm, and the diameter of the outlet pipe is 10 cm; the distance between every two outlet holes distributed on each outlet pipe is 20 cm.

[0057] In the depth direction of the nitrification zone, a total of two layers of shunt micro-units are arranged, located 20 cm and 40 cm below the bed surface respectively, and the vertical distance between the two layers of shunt micro-units is 20 cm; the first layer of shunt micro-units is located below the water inlet holes, and the second layer of shunt micro-units is arranged staggeredly with the first layer of shunt micro-units; in the horizontal direction, the center distance between adjacent shunt micro-units is 40 cm;

[0058] The mixed clay layer (formed by uniformly mixing clay and quartz sand with an average particle size of 5 mm in a volume ratio of 7:3) in each shunt micro-unit is cylindrical, with a diameter of 10 cm, a thickness of the mixed clay layer of 4 cm, and a thickness of the biochar layer (the average particle size of the biochar constituting the biochar layer is 5 mm) of 6 cm.

[0059] The biochemical treatment tail water of pig breeding wastewater enters the nitrification zone of the constructed wetland from the water inlet holes uniformly distributed on the water inlet pipe, and flows downward along the pores of the quartz sand filled in the digestion zone to the shunt micro-units. During this process, nitrification reactions occur, converting ammonia nitrogen into nitrate nitrogen; subsequently, the water flow contacts the biochar, and denitrification reactions occur here. At the same time, the direction of the water flow is deflected under the barrier of the mixed clay layer and enters the nitrification zone again for nitrification reactions, and nitrification and denitrification reactions occur alternately;

[0060] After the nitrification process is completed, the water flow continues to flow downward into the denitrification zone (the inorganic filler quartz sand in the denitrification zone 2 is dispersed in the biochar, and the volume ratio of quartz sand (average particle size of 5 mm) and biochar (average particle size of 5 mm) is 3:2). The denitrification process is carried out under the condition of denitrifying bacteria with biochar as the carbon source. After the nitrogen removal process is completed, the effluent (the ammonia nitrogen concentration in the effluent is 5 mg / L, and the nitrate nitrogen concentration is 20 mg / L) enters the outlet pipe from the outlet holes and is discharged from the constructed wetland system.

[0061] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments can also be obtained according to this embodiment without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An artificial wetland deep denitrification system, characterized in that, It includes a vertical-flow constructed wetland bed body; the vertical-flow constructed wetland bed body includes a nitrification zone (1) above the water level line (8) and a denitrification zone (2) below the water level line (8); The nitrification zone (1) is filled with inorganic fillers (9) and is provided with a plurality of diversion micro-units (10); each diversion micro-unit (10) includes a mixed clay layer (11) and biochar (12) located on the mixed clay layer (11); The upper surface of the nitrification zone (1) is paved with a plurality of inlet pipes (3); each inlet pipe (3) is provided with a plurality of inlet holes (5); The bottom of the denitrification zone (2) is paved with a plurality of outlet pipes (4), and each outlet pipe (4) is provided with a plurality of outlet holes (6); the denitrification zone (2) is filled with inorganic fillers (9) and biochar (12); Wetland plants (7) are planted on the vertical-flow constructed wetland bed body.

2. The constructed wetland deep denitrification system according to claim 1, wherein In the denitrification zone (2), the volume ratio of the inorganic filler (9) to the biochar (12) is 3:2; the particle sizes of the inorganic filler (9) and the biochar (12) are independently 3-8 mm.

3. The constructed wetland deep denitrification system according to claim 1, wherein The mixed clay layer (11) is a cylindrical clay-based material with a diameter of 10-15 cm and a thickness of 3-5 cm.

4. The constructed wetland deep denitrification system according to claim 1 or 3, characterized in that The clay-based material includes clay and inorganic fillers; in the clay-based material, the volume ratio of clay to inorganic fillers is 7:3-5:

5.

5. The constructed wetland deep denitrification system according to claim 1, wherein In the diversion micro-unit (10), the biochar (12) is presented in the form of a biochar layer; the thickness of the biochar layer is 5-10 cm.

6. The constructed wetland deep denitrification system according to claim 1, wherein In the depth direction of the nitrification zone (1), a layer of diversion micro-unit (10) is arranged every 20-30 cm; in the horizontal direction of the nitrification zone (1), the diversion micro-units (10) are arranged in a plum blossom shape.

7. The constructed wetland deep denitrification system according to claim 1, characterized in that In the horizontal direction, the interval distance between every two inlet pipes (3) is 30-60 cm; the pipe diameter of each inlet pipe is 2-10 cm; in the horizontal direction, the interval distance between every two outlet pipes (4) is 30-60 cm; the pipe diameter of each outlet pipe is 5-15 cm.

8. Application of the artificial wetland deep nitrogen removal system according to any one of claims 1 to 7 in treating the biochemical treatment tail water of pig breeding wastewater.

9. A method for treating the biochemical treatment tail water of pig farm wastewater by using the constructed wetland deep denitrification system according to any one of claims 1 to 7, characterized in that, It includes the following steps: The biochemical treatment tail water of pig breeding wastewater enters the nitrification zone (1) of the artificial wetland from the inlet holes (5) distributed on the inlet pipe (3). In the nitrification zone (1), the water flow flows downward along the pores of the inorganic filler (9), and after being diverted by the diversion micro-unit (10), the flow path of the water flow in the nitrification zone (1) is increased, and an anoxic environment containing water is formed around the biochar (12) on the diversion micro-unit (10), so that nitrification reaction and denitrification reaction occur alternately in the nitrification zone (1); denitrification reaction is carried out in the denitrification zone (2), and the effluent is discharged from the outlet pipe (4); the oxygen required for the nitrification reaction is provided by atmospheric reoxygenation and wetland plants.

10. The method according to claim 9, wherein In the biochemical treatment tail water of pig breeding wastewater, the mass concentration ratio of ammonia nitrogen to nitrate nitrogen ≤ 1:3; When the mass concentration ratio of ammonia nitrogen to nitrate nitrogen in the biochemical treatment tail water of pig breeding wastewater is 1:3 - 1:4, control the water level by adjusting the height of the end of the outlet pipe (4) so that the height ratio of the nitrification zone (1) to the denitrification zone (2) is 1:1; When the mass concentration ratio of ammonia nitrogen to nitrate nitrogen in the biochemical treatment tail water of pig breeding wastewater is less than 1:4, control the water level by adjusting the height of the end of the outlet pipe (4) so that the height ratio of the nitrification zone (1) to the denitrification zone (2) is 1:2.

Images