Embedded composite wetland system and method for intensively removing COD (Chemical Oxygen Demand), NH3-N and TN (Total Nitrogen)

Abstract

The invention discloses an embedded composite wetland system and a method for intensively removing COD (Chemical Oxygen Demand), NH3-N and TN (Total Nitrogen). Comprising a primary regulating tank and a secondary regulating tank, wherein a first-stage aerobic regulating region and a first-stage anoxic region integrally arranged below the first-stage aerobic regulating region are arranged in the first-stage regulating tank; a second-stage aerobic adjusting area and a second-stage anoxic area integrally arranged below the second-stage aerobic adjusting area are arranged in the second-stage adjusting tank; and the first-stage anoxic zone and the second-stage anoxic zone are communicated through a communicating pipe. An aerobic zone and an anoxic zone at the same stage are embedded up and down, and two stages of regulating tanks are communicated through a communicating pipe and are connected in series; and a reflux pump is positioned in the second-stage aerobic zone and respectively flows back to the first-stage anoxic zone and the second-stage anoxic zone. By adjusting the aeration rate, the reflux ratio and the reflux quantity, target pollutants are removed in a targeted manner, and COD, NH3-N and TN are removed in an enhanced manner.

Description

Technical Field

[0001] The present invention relates to an embedded composite wetland system and a method for enhancing the removal of COD, NH 3 -N and TN. Background Art

[0002] As an ecological sewage treatment process, constructed wetlands have remarkable effects on the removal of pollutants such as organic matter, nitrogen, and phosphorus. In recent years, constructed wetlands have been widely used in the upgrading of the effluent of sewage treatment plants, the bypass purification of river water bodies, etc. However, in practical applications, on the one hand, in the process combination design, generally, surface flow wetlands, horizontal subsurface flow wetlands or vertical subsurface flow wetlands are simply connected in series, and different treatment functional areas are not divided for different target pollutants. Moreover, many of the current combined wetland processes are in a fixed mode, that is, the functional areas cannot be flexibly adjusted during operation, resulting in poor removal effects of certain pollutants under different water quality conditions. Especially when the water quality changes, if it is still operated according to the initial design conditions, it will not only cause some pollutant indicators to exceed the standard, but also be "excessive waste" for other pollutants. On the other hand, in the plane and structure layout of the combined wetland, currently, the separated type is usually adopted, that is, each type of wetland is set separately. This layout form not only occupies a large area, but also has a high operation cost. Summary of the Invention

[0003] To overcome the above defects, the purpose of the present invention is to provide an embedded composite wetland system and a method for enhancing the removal of COD, NH 3 -N and TN.

[0004] To achieve the above purpose, the embedded composite wetland system of the present invention includes a primary regulation tank and a secondary regulation tank; wherein,

[0005] A primary aerobic regulation area is arranged in the primary regulation tank, and a primary anoxic area is integrally arranged below the primary aerobic regulation area;

[0006] A secondary aerobic regulation area is arranged in the secondary regulation tank, and a secondary anoxic area is integrally arranged below the secondary aerobic regulation area;

[0007] The primary anoxic area and the secondary anoxic area are connected through a connecting pipe.

[0008] Furthermore, a reflux system is further included, and the reflux system includes a reflux pump, a reflux inlet pipe and a reflux distribution pipe; wherein, the reflux inlet pipe is arranged in the secondary regulation tank; the reflux distribution pipe is arranged in the primary regulation tank.

[0009] Further, the first-stage aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h1 of the first-stage aerobic regulation zone is 0.5 - 3.0 m, and the hydraulic retention time t1 is 12 - 24 h;

[0010] Further, when the water depth of the first-stage aerobic regulation zone is 0.5 - 1.0 m, the aeration device is bottom aeration; when the water depth of the first-stage aerobic regulation zone is 1.0 - 3.0 m, the aeration device is bottom aeration or surface aeration or fountain aeration or a combination of several of the above aeration methods.

[0011] Further, packing materials and an effluent collection pipe are provided in the first-stage anoxic zone; the packing materials in the first-stage anoxic zone include: gravel, pebble, zeolite, ceramsite, granular activated carbon, activated coke, and / or biomass packing materials, the height of the packing materials is 0.5 - 3.5 m, the particle size of the packing materials is 5 - 150 mm, and the hydraulic conductivity of the packing materials is 0.01 - 0.5 m / s; the hydraulic retention time of the first-stage anoxic zone is 8 - 16 h; an effluent collection pipe communicating with a connecting pipe is provided at the bottom of the packing materials.

[0012] Further, packing materials and an influent distribution pipe are provided in the second-stage anoxic zone; the packing materials in the second-stage anoxic zone are gravel, pebble, zeolite, ceramsite, and / or crushed stone, the height of the packing materials is 1.0 - 3.0 m, the particle size of the packing materials is 15 - 150 mm, and the hydraulic conductivity of the packing materials is 0.02 - 0.5 m / s; the hydraulic retention time of the second-stage anoxic zone is 8 - 12 h; an influent distribution pipe communicating with a connecting pipe is provided at the bottom of the packing materials.

[0013] Further, the second-stage aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h2 of the second-stage aerobic regulation zone is 0.5 - 2.0 m, and the hydraulic retention time t2 is 12 - 18 h.

[0014] Further, when the water depth h2 of the second-stage aerobic regulation zone is 0.5 - 1.0 m, the aeration device is bottom aeration; when the water depth h2 of the second-stage aerobic regulation zone is 1.0 - 2.0 m, the aeration device is bottom aeration or surface aeration or fountain aeration or a combination of several of the above aeration methods.

[0015] Further, the reflux distribution pipe is communicatively connected with the connecting pipe.

[0016] To achieve the above object, the method for enhancing the removal of COD, NH 3 -N and TN by the embedded composite wetland system of the present invention includes the following steps:

[0017] (A) When the influent COD or NH3-N or both of them are high and TN is low, increase the aeration volume of the first-stage aerobic regulation zone and the second-stage aerobic regulation zone, reduce the reflux ratio, and decrease the reflux volume;

[0018] (B) When the influent COD, NH3 When both -N and TN are relatively high, increase the aeration volume in the first - stage aerobic regulation zone and the second - stage aerobic regulation zone, increase the reflux ratio, and increase the reflux flow rate;

[0019] (C)When the influent COD or NH 3 -N or both of them are relatively low and TN is relatively high, decrease the aeration volume in the first - stage aerobic regulation zone and the second - stage aerobic regulation zone, increase the reflux ratio, and increase the reflux flow rate;

[0020] (D)When the influent COD, NH 3 -N and TN are both relatively low, decrease the aeration volume in the first - stage aerobic regulation zone and the second - stage aerobic regulation zone, decrease the reflux ratio, and decrease the reflux flow rate;

[0021] (E)When the influent COD is relatively high, NH 3 -N and TN are both relatively low, increase the aeration volume in the first - stage aerobic regulation zone and the second - stage aerobic regulation zone, decrease the reflux ratio, and decrease the reflux flow rate;

[0022] (F)When the influent COD is relatively low, NH 3 -N and TN are both relatively high, decrease the aeration volume in the first - stage aerobic regulation zone, increase the aeration volume in the second - stage aerobic regulation zone, increase the reflux ratio, and increase the reflux flow rate.

[0023] In the present invention, the aerobic zones and anoxic zones of the same level are in an up - and - down embedded form, and the two - stage aerobic zones and anoxic zones are connected by a connecting pipe in a series manner; the reflux pump is located in the second - stage aerobic zone and returns to the first - stage anoxic zone and the second - stage anoxic zone respectively. By adjusting the aeration volume, reflux ratio, and reflux flow rate, target pollutants are removed specifically, and the removal of COD, NH 3 -N and TN is strengthened. It can not only adjust the operating conditions and flexibly regulate the treatment functional areas, but also has a compact planar structure layout, small floor area, and low operating cost. Brief Description of the Drawings

[0024] Figure 1 It is a schematic structural diagram of the present invention.

[0025] Description of the drawing numbers: 1. First - stage aerobic zone; 2. First - stage anoxic zone; 3. Effluent collection pipe of the first - stage anoxic zone; 4. Intermediate connecting pipe; 5. Water distribution pipe for the inlet of the second - stage anoxic zone; 6. Second - stage anoxic zone; 7. Second - stage aerobic zone; 8. Partition board or partition wall or earth embankment; 9. Reflux pump; 10. Reflux pipe Detailed Embodiment

[0026] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0027] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0028] The terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0029] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] Embodiment 1

[0031] In this Embodiment 1, the first aerobic regulation zone includes aquatic plants, aquatic animals, and an aeration device; the water depth h of the first aerobic regulation zone 1 is 0.5 m, and the hydraulic retention time t 1 is 12 h; the aeration device in the first aerobic regulation zone is bottom aeration; the first anoxic zone is located directly below the first aerobic regulation zone, and the packing in the first anoxic zone is gravel, pebble, and zeolite, and the packing height H 1 is 0.5 m, the packing particle size is 5 mm, and the hydraulic conductivity of the packing is 0.01 m / s; the hydraulic retention time T of the first anoxic zone 1 is 8 h; the effluent collection pipe uses a perforated pipe; the second anoxic zone is located directly below the second aerobic regulation zone, a partition is provided between the first aerobic regulation zone and the first anoxic zone and the second aerobic regulation zone and the second anoxic zone, and the first anoxic zone and the second anoxic zone are connected through a connecting pipe; the packing in the second anoxic zone is zeolite, ceramsite, and gravel, and the packing height H 2 is 1.0 m, the packing particle size is 15 mm, and the hydraulic conductivity of the packing is 0.02 m / s; the hydraulic retention time T of the second anoxic zone 2 is 8 h; the influent distribution pipe is located at the bottom of the packing and uses a filter head; the second aerobic regulation zone includes aquatic plants, aquatic animals, and an aeration device; the water depth h of the second aerobic regulation zone2 is 0.5 m, and the hydraulic retention time t 2 is 12 h; the aeration device in the secondary aerobic regulation zone is bottom aeration; the reflux system includes a reflux pump, a reflux main pipe, and a reflux water distribution pipe. Among them, the reflux pump is located in the secondary aerobic regulation zone, and the reflux ratio is 100%; the reflux main pipe is respectively connected to the reflux water distribution pipe and the connecting pipes of the first and second anoxic zones; the reflux water distribution pipe is located in the middle of the first anoxic zone and is a perforated pipe.

[0032] By adjusting the aeration volume, reflux ratio, and reflux flow rate, specifically strengthen the removal of COD, NH 3 -N or TN.

[0033] Example 2

[0034] In this Example 2, the first aerobic regulation zone includes aquatic plants, aquatic animals, and an aeration device; the water depth h of the first aerobic regulation zone 1 is 3.0 m, and the hydraulic retention time t 1 is 24 h; the aeration device in the first aerobic regulation zone is surface aeration; the first anoxic zone is located directly below the first aerobic regulation zone, and the packing in the first anoxic zone is ceramsite, granular activated carbon, activated coke, and biomass packing, and the packing height H 1 is 3.5 m, the packing particle size is 150 mm, and the hydraulic conductivity of the packing is 0.5 m / s; the hydraulic retention time T of the first anoxic zone 1 is 16 h; the effluent collection pipe uses filter heads; the second anoxic zone is located directly below the second aerobic regulation zone, a partition wall is provided between the first aerobic regulation zone and the first anoxic zone and the second aerobic regulation zone and the second anoxic zone, and the first anoxic zone is connected to the second anoxic zone through a connecting pipe; the packing in the second anoxic zone is gravel, pebble, zeolite, and ceramsite, and the packing height H 2 is 3.0 m, the packing particle size is 150 mm, and the hydraulic conductivity of the packing is 0.5 m / s; the hydraulic retention time T of the second anoxic zone 2 is 12 h; the influent water distribution pipe is located at the bottom of the packing and is a perforated pipe; the second aerobic regulation zone includes aquatic plants, aquatic animals, and an aeration device; the water depth h of the second aerobic regulation zone 2 is 2.0 m, and the hydraulic retention time t 2 is 18 h; the aeration device in the second aerobic regulation zone is fountain aeration; the reflux system includes a reflux pump, a reflux main pipe, and a reflux water distribution pipe. Among them, the reflux pump is located in the second aerobic regulation zone, and the reflux ratio is 500%; the reflux main pipe is respectively connected to the reflux water distribution pipe and the connecting pipes of the first and second anoxic zones; the reflux water distribution pipe is located in the middle of the first anoxic zone and uses filter heads.

[0035] By adjusting the aeration volume, reflux ratio, and reflux flow rate, specifically strengthen the removal of COD, NH 3 -N or TN.

[0036] Example 3

[0037] In Example 3, the first-stage aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h of the first-stage aerobic regulation zone 1 is 2.5 m, and the hydraulic retention time t 1 is 20 h; the aeration device in the first-stage aerobic regulation zone is a combination of surface aeration and bottom aeration; the first-stage anoxic zone is located directly below the first-stage aerobic regulation zone, and the packing in the first-stage anoxic zone is gravel, activated coke, and biomass packing, and the packing height H 1 is 2.0 m, the packing particle size is 100 mm, and the hydraulic conductivity of the packing is 0.35 m / s; the hydraulic retention time T of the first-stage anoxic zone 1 is 12 h; the effluent collection pipe uses a perforated pipe; the second-stage anoxic zone is located directly below the second-stage aerobic regulation zone, and an earth embankment is set between the first-stage aerobic regulation zone and the first-stage anoxic zone and the second-stage aerobic regulation zone and the second-stage anoxic zone. The first-stage anoxic zone and the second-stage anoxic zone are connected by a connecting pipe; the packing in the second-stage anoxic zone is crushed stone, and the packing height H 2 is 1.8 m, the packing particle size is 120 mm, and the hydraulic conductivity of the packing is 0.4 m / s; the hydraulic retention time T of the second-stage anoxic zone 2 is 10 h; the influent distribution pipe is located at the bottom of the packing and uses a filter head; the second-stage aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h of the second-stage aerobic regulation zone 2 is 1.5 m, and the hydraulic retention time t 2 is 12 h; the aeration device in the second-stage aerobic regulation zone is a combination of fountain aeration and bottom aeration; the reflux system includes a reflux pump, a reflux main pipe, and a reflux distribution pipe. Among them, the reflux pump is located in the second-stage aerobic regulation zone, and the reflux ratio is 300%; the reflux main pipe is respectively connected to the reflux distribution pipe and the connecting pipes of the first- and second-stage anoxic zones; the reflux distribution pipe is located in the middle of the first-stage anoxic zone and uses a perforated pipe.

[0038] Example 4

[0039] In Example 4, the first-stage aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h of the first-stage aerobic regulation zone 1 is 0.8 m, and the hydraulic retention time t 1 is 14 h; the aeration device in the first-stage aerobic regulation zone is bottom aeration; the first-stage anoxic zone is located directly below the first-stage aerobic regulation zone, and the packing in the first-stage anoxic zone is gravel, pebble, activated coke, and biomass packing, and the packing height H 1 is 1.0 m, the packing particle size is 30 mm, and the hydraulic conductivity of the packing is 0.1 m / s; the hydraulic retention time T of the first-stage anoxic zone 1is 10 h; the effluent collection pipe is a perforated pipe; the secondary anoxic zone is located directly below the secondary aerobic regulation zone, and an earth embankment is arranged between the primary aerobic regulation zone and the primary anoxic zone and the secondary aerobic regulation zone and the secondary anoxic zone. The primary anoxic zone and the secondary anoxic zone are connected by a connecting pipe; the packing in the secondary anoxic zone is zeolite, ceramsite, and gravel, and the packing height H 2 is 1.2 m, the packing particle size is 25 mm, and the hydraulic conductivity of the packing is 0.08 m / s; the hydraulic retention time T 2 in the secondary anoxic zone is 9 h; the influent distribution pipe is located at the bottom of the packing and uses filter heads; the secondary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h 2 in the secondary aerobic regulation zone is 1.0 m, and the hydraulic retention time t 2 is 15 h; the aeration device in the secondary aerobic regulation zone is bottom aeration; the reflux system includes a reflux pump, a reflux main pipe, and a reflux distribution pipe. Among them, the reflux pump is located in the secondary aerobic regulation zone, and the reflux ratio is 200%; the reflux main pipe is connected to the reflux distribution pipe and the connecting pipes of the primary and secondary anoxic zones respectively; the reflux distribution pipe is located in the middle of the primary anoxic zone and uses a perforated pipe.

[0040] By adjusting the aeration volume, reflux ratio, and return flow rate, targeted strengthening is carried out to remove COD, NH 3 -N or TN.

[0041] Example 5

[0042] In this Example 5, the primary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h 1 in the primary aerobic regulation zone is 2.2 m, and the hydraulic retention time t 1 is 17 h; the aeration device in the primary aerobic regulation zone is a combination of bottom aeration and fountain aeration; the primary anoxic zone is located directly below the primary aerobic regulation zone, and the packing in the primary anoxic zone is gravel and biomass packing, and the packing height H 1 is 1.6 m, the packing particle size is 80 mm, and the hydraulic conductivity of the packing is 0.28 m / s; the hydraulic retention time T 1 in the primary anoxic zone is 13 h; the effluent collection pipe uses filter heads; the secondary anoxic zone is located directly below the secondary aerobic regulation zone, and a partition is arranged between the primary aerobic regulation zone and the primary anoxic zone and the secondary aerobic regulation zone and the secondary anoxic zone. The primary anoxic zone and the secondary anoxic zone are connected by a connecting pipe; the packing in the secondary anoxic zone is zeolite and ceramsite, and the packing height H 2 is 1.8 m, the packing particle size is 50 mm, and the hydraulic conductivity of the packing is 0.14 m / s; the hydraulic retention time T 2 in the secondary anoxic zone is 12 h; the influent distribution pipe is located at the bottom of the packing and uses a perforated pipe; the secondary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h 2 in the secondary aerobic regulation zone is 1.7 m, and the hydraulic retention time t2 is 16.5 h; the aeration device in the secondary aerobic regulation zone is bottom aeration; the reflux system includes a reflux pump, a reflux main pipe, and a reflux water distribution pipe. Among them, the reflux pump is located in the secondary aerobic regulation zone, and the reflux ratio is 350%; the reflux main pipe is respectively connected to the reflux water distribution pipe and the connecting pipes of the first and second anoxic zones; the reflux water distribution pipe is located in the middle of the first anoxic zone and uses filter heads.

[0043] By adjusting the aeration volume, reflux ratio, and reflux flow rate, targeted strengthening is carried out to remove COD, NH 3 -N or TN.

[0044] Example 6

[0045] Based on the above embodiments, this embodiment provides a control method for strengthening the removal of COD, NH 3 -N and TN as follows:

[0046] (A) When the influent COD or NH 3 -N or both of them are high and TN is low, increase the aeration volume in the first aerobic regulation zone and the secondary aerobic regulation zone, reduce the reflux ratio, and decrease the reflux flow rate;

[0047] (B) When the influent COD, NH 3 -N, and TN are all high, increase the aeration volume in the first aerobic regulation zone and the secondary aerobic regulation zone, increase the reflux ratio, and increase the reflux flow rate;

[0048] (C) When the influent COD or NH 3 -N or both of them are low and TN is high, decrease the aeration volume in the first aerobic regulation zone and the secondary aerobic regulation zone, increase the reflux ratio, and increase the reflux flow rate;

[0049] (D) When the influent COD, NH 3 -N, and TN are all low, decrease the aeration volume in the first aerobic regulation zone and the secondary aerobic regulation zone, reduce the reflux ratio, and decrease the reflux flow rate;

[0050] (E) When the influent COD is high and NH 3 -N and TN are both low, increase the aeration volume in the first aerobic regulation zone and the secondary aerobic regulation zone, reduce the reflux ratio, and decrease the reflux flow rate;

[0051] (F) When the influent COD is low and NH 3 -N and TN are both high, decrease the aeration volume in the first aerobic regulation zone, increase the aeration volume in the secondary aerobic regulation zone, increase the reflux ratio, and increase the reflux flow rate.

[0052] The present invention has been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art. Many other changes and modifications made without departing from the concept and scope of the present invention should be regarded as falling within the protection scope of the present invention.

[0053] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any one or more embodiments or examples in a suitable manner.

[0054] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims described.

Claims

1. An embedded composite wetland system, characterized in that: It includes the primary regulating pool and the secondary regulating pool; among which, A primary aerobic regulating zone and a primary anoxic zone integrally arranged below the primary aerobic regulating zone are arranged in the primary regulating pool; A secondary aerobic regulating zone and a secondary anoxic zone integrally arranged below the secondary aerobic regulating zone are arranged in the secondary regulating pool; The primary anoxic zone and the secondary anoxic zone are connected via a connecting pipe.

2. The embedded composite wetland system according to claim 1, characterized in that: It also includes a reflux system, which includes a reflux pump, a reflux water inlet pipe and a reflux water distribution pipe; wherein the reflux water inlet pipe is arranged in the secondary regulating tank; and the reflux water distribution pipe is arranged in the primary regulating tank.

3. The embedded composite wetland system according to claim 1, characterized in that: The primary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h1 of the primary aerobic regulation zone is 0.5~3.0m, and the hydraulic retention time t1 is 12~24h.

4. The embedded composite wetland system according to claim 1, characterized in that: When the water depth in the primary aerobic regulation zone is 0.5~1.0m, the aeration device is bottom aeration; when the water depth in the primary aerobic regulation zone is 1.0~3.0m, the aeration device is bottom aeration or surface aeration or fountain aeration or a combination of the above aeration methods.

5. The embedded composite wetland system according to claim 1, characterized in that: The first-level anoxic zone is provided with fillers and an effluent collecting pipe; the fillers in the first-level anoxic zone include: gravel, pebbles, zeolite, expanded clay, granular activated carbon, activated coke and / or biomass fillers, the filler height is 0.5~3.5m, the filler particle size is 5~150mm, and the filler hydraulic conductivity is 0.01~0.5m / s; the hydraulic retention time of the first-level anoxic zone is 8~16h; an effluent collecting pipe connected to the connecting pipe is provided at the bottom of the filler.

6. The embedded composite wetland system according to claim 1, characterized in that: Fillers and water inlet and water distribution pipes are arranged in the secondary anoxic zone; the fillers in the secondary anoxic zone are gravel, pebbles, zeolite, ceramsite and / or crushed stone, the filler height is 1.0~3.0m, the filler particle size is 15~150mm, and the filler hydraulic conductivity is 0.02~0.5m / s; the hydraulic retention time of the secondary anoxic zone is 8~12h; a water inlet and water distribution pipe connected with the connecting pipe is arranged at the bottom of the filler.

7. The embedded composite wetland system according to claim 1, characterized in that: The secondary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h2 of the secondary aerobic regulation zone is 0.5~2.0m, and the hydraulic retention time t2 is 12~18h.

8. The embedded composite wetland system according to claim 1, characterized in that: When the water depth h2 in the secondary aerobic regulation zone is 0.5~1.0m, the aeration device is bottom aeration; when the water depth h2 in the secondary aerobic regulation zone is 1.0~2.0m, the aeration device is bottom aeration or surface aeration or fountain aeration or a combination of the above aeration methods.

9. The embedded composite wetland system according to claim 2, characterized in that: The reflux water distribution pipe is connected to the connecting pipe.

10. A method for enhanced removal of COD, NH3-N and TN by an embedded composite wetland system, characterized in that: The method comprises the following steps: (A) When the influent COD or NH3-N or both are high and TN is low, increase the aeration volume of the primary aerobic regulating zone and the secondary aerobic regulating zone, reduce the reflow ratio, and reduce the reflow volume; (B) When the influent COD, NH3-N and TN are all high, increase the aeration volume of the primary aerobic adjustment zone and the secondary aerobic adjustment zone, increase the reflow ratio, and increase the reflow volume; (C) When the influent COD or NH3-N or both are low and TN is high, reduce the aeration volume of the primary aerobic regulating zone and the secondary aerobic regulating zone, increase the reflow ratio, and increase the reflow volume; (D) When the influent COD, NH3-N and TN are all low, reduce the aeration volume in the primary aerobic regulating zone and the secondary aerobic regulating zone, reduce the reflow ratio and reduce the reflow volume; (E) When the influent COD is high and the NH3-N and TN are low, increase the aeration volume in the primary aerobic regulating zone and the secondary aerobic regulating zone, reduce the reflow ratio, and reduce the reflow volume; (F) When the influent COD is low and the NH3-N and TN are both high, reduce the aeration volume in the primary aerobic regulating zone, increase the aeration volume in the secondary aerobic regulating zone, increase the reflow ratio, and increase the reflow volume.

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