An embedded composite wetland system and a method for intensively removing COD, NH3-N and TN

Abstract

The application discloses an embedded composite wetland system and a method for intensively removing COD, NH3-N and TN. The system comprises a first adjusting pool and a second adjusting pool. A first aerobic adjusting area is arranged in the first adjusting pool, and a first anoxic area is integrally arranged below the first aerobic adjusting area. A second aerobic adjusting area is arranged in the second adjusting pool, and a second anoxic area is integrally arranged below the second aerobic adjusting area. The first anoxic area and the second anoxic area are communicated through a communicating pipe. In the application, the aerobic area and the anoxic area of the same stage are embedded in an up-down mode, the two adjusting pools are communicated through the communicating pipe in a series mode, and a reflux pump is arranged in the second aerobic adjusting area and is used for refluxing to the first anoxic area and the second anoxic area. Through adjustment of aeration quantity, reflux ratio and reflux amount, target pollutants can be removed in a targeted mode, and COD, NH3-N and TN can be intensively removed.

Description

Technical Field

[0001] This invention relates to an embedded composite wetland system and a method for enhanced removal of COD, NH3-N and TN. Background Technology

[0002] Constructed wetlands, as an ecological wastewater treatment technology, are highly effective in removing pollutants such as organic matter, nitrogen, and phosphorus. In recent years, constructed wetlands have been widely used for upgrading wastewater treatment plant effluent and bypass purification of river water bodies. However, in practical applications, on the one hand, the process combination design generally involves simply connecting surface flow wetlands, horizontal subsurface flow wetlands, or vertical subsurface flow wetlands in series, without defining different treatment functional zones for different target pollutants. Moreover, many currently used combined wetland processes operate on a fixed model, meaning that functional zones cannot be flexibly adjusted during operation, resulting in poor removal efficiency for certain pollutants under different water quality conditions. Especially when water quality changes, operating according to the initial design conditions will not only cause some pollutant indicators to exceed standards but also result in "excessive waste" for other pollutants. On the other hand, the current layout and structure of combined wetlands typically adopt a separate approach, with each type of wetland set up independently. This layout not only requires a large land area but also incurs high operating costs. Summary of the Invention

[0003] To overcome the above-mentioned defects, the present invention aims to provide an embedded composite wetland system and a method for enhanced removal of COD, NH3-N and TN.

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

[0005] The primary equalization tank is equipped with a primary aerobic equalization zone and a primary anoxic zone integrated below the primary aerobic equalization zone.

[0006] The secondary equalization tank is equipped with a secondary aerobic equalization zone and a secondary anoxic zone integrated below the secondary aerobic equalization zone;

[0007] The primary hypoxic zone and the secondary hypoxic zone are connected by a connecting pipe.

[0008] Furthermore, it also includes a reflux system, which includes a reflux pump, a reflux inlet pipe, and a reflux distribution pipe; wherein the reflux inlet pipe is installed in the secondary regulating tank; and the reflux distribution pipe is installed in the primary regulating tank.

[0009] Furthermore, the primary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h1 in the primary aerobic regulation zone is 0.5~3.0m, and the hydraulic retention time t1 is 12~24h.

[0010] Furthermore, 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, surface aeration, fountain aeration, or a combination of the above aeration methods.

[0011] Furthermore, the primary anoxic zone is equipped with packing material and an effluent collection pipe; the packing material in the primary anoxic zone includes: gravel, pebbles, zeolite, ceramsite, granular activated carbon, activated coke and / or biomass packing material, with a packing height of 0.5~3.5m, a packing particle size of 5~150mm, and a packing hydraulic conductivity of 0.01~0.5m / s; the hydraulic retention time in the primary anoxic zone is 8~16h; and an effluent collection pipe connected to a connecting pipe is provided at the bottom of the packing material.

[0012] Furthermore, a packing material and an inlet water distribution pipe are installed in the secondary anoxic zone; the packing material in the secondary anoxic zone is gravel, pebbles, zeolite, ceramsite and / or crushed stone, with a packing height of 1.0~3.0m, a packing particle size of 15~150mm, and a packing hydraulic conductivity of 0.02~0.5m / s; the hydraulic retention time in the secondary anoxic zone is 8~12h; and an inlet water distribution pipe connected to a connecting pipe is installed at the bottom of the packing material.

[0013] Furthermore, the secondary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h2 in the secondary aerobic regulation zone is 0.5~2.0m, and the hydraulic retention time t2 is 12~18h.

[0014] Furthermore, 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, surface aeration, fountain aeration, or a combination of the above aeration methods.

[0015] Furthermore, the return water distribution pipe is connected to the connecting pipe.

[0016] To achieve the above objectives, the embedded composite wetland system of the present invention provides a method for enhanced removal of COD, NH3-N, and TN, comprising the following steps:

[0017] (A) When the influent COD or NH3-N or both of the above are high and TN is low, increase the aeration rate of the primary aerobic regulation zone and the secondary aerobic regulation zone, reduce the reflux ratio, and decrease the reflux flow rate;

[0018] (B) When the influent COD, NH3-N and TN are all high, increase the aeration rate of the primary aerobic regulation zone and the secondary aerobic regulation zone, increase the reflux ratio and increase the reflux flow rate;

[0019] (C) When the influent COD or NH3-N or both of the above are low and TN is high, reduce the aeration rate of the primary aerobic regulation zone and the secondary aerobic regulation zone, increase the reflux ratio, and increase the reflux flow rate;

[0020] (D) When the influent COD, NH3-N and TN are all low, reduce the aeration rate in the primary aerobic regulation zone and the secondary aerobic regulation zone, reduce the reflux ratio and reduce the reflux flow rate;

[0021] (E) When the influent COD is high and both NH3-N and TN are low, increase the aeration rate in the primary and secondary aerobic regulation zones, reduce the reflux ratio, and decrease the reflux flow rate;

[0022] (F) When the influent COD is low and both NH3-N and TN are high, reduce the aeration rate of the primary aerobic regulation zone, increase the aeration rate of the secondary aerobic regulation zone, increase the reflux ratio, and increase the reflux flow rate.

[0023] In this invention, the aerobic and anoxic zones are vertically embedded, connected in series via a connecting pipe. A return pump is located in the secondary aerobic zone, returning air to both the primary and secondary anoxic zones. By adjusting the aeration rate, return ratio, and return flow rate, target pollutants are specifically removed, with enhanced removal of COD, NH3-N, and TN. This design not only allows for adjustment of operating conditions and flexible regulation of treatment zones, but also features a compact planar layout, small footprint, and low operating costs. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention.

[0025] Drawing number explanations: 1. Primary aerobic zone; 2. Primary anoxic zone; 3. Primary anoxic zone effluent collection pipe; 4. Intermediate connecting pipe; 5. Secondary anoxic zone inlet distribution pipe; 6. Secondary anoxic zone; 7. Secondary aerobic zone; 8. Baffle, partition wall, or earthen embankment; 9. Return pump; 10. Return pipe. Detailed Implementation

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

[0027] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0028] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] Example 1

[0031] In this embodiment 1, the primary aerobic regulation zone includes aquatic plants, aquatic animals, and an aeration device; the water depth h1 in the primary aerobic regulation zone is 0.5m, and the hydraulic retention time t1 is 12h; the aeration device in the primary aerobic regulation zone is bottom aeration; the primary anoxic zone is located directly below the primary aerobic regulation zone, and the packing material in the primary anoxic zone is gravel, pebbles, and zeolite, with a packing height H1 of 0.5m, a packing particle size of 5mm, and a packing hydraulic conductivity of 0.01m / s; the hydraulic retention time T1 in the primary anoxic zone is 8h; the effluent collection pipe is a perforated pipe; the secondary anoxic zone is located directly below the secondary aerobic regulation zone, and the primary aerobic regulation zone and the primary anoxic zone are connected to the secondary aerobic regulation zone. A partition is installed between the primary and secondary anoxic zones. The primary and secondary anoxic zones are connected by a connecting pipe. The packing material in the secondary anoxic zone is zeolite, ceramsite, and crushed stone, with a packing height H2 of 1.0m, a packing particle size of 15mm, and a hydraulic conductivity of 0.02m / s. The hydraulic retention time T2 in the secondary anoxic zone is 8h. The inlet water distribution pipe is located at the bottom of the packing material and uses a filter head. The secondary aerobic regulating zone includes aquatic plants, aquatic animals, and aeration devices. The water depth h2 in the secondary aerobic regulating zone is 0.5m, and the hydraulic retention time t2 is 12h. The aeration device in the secondary aerobic regulating zone is bottom aeration. The recirculation system includes a recirculation pump, a recirculation main pipe, and a recirculation distribution pipe. The recirculation pump is located in the secondary aerobic regulating zone, with a recirculation ratio of 100%. The recirculation main pipe is connected to the recirculation distribution pipe and the connecting pipe between the primary and secondary anoxic zones. The recirculation distribution pipe is located in the middle of the primary anoxic zone and uses a perforated pipe.

[0032] By adjusting the aeration rate, reflux ratio, and reflux flow rate, the removal of COD, NH3-N, or TN can be specifically enhanced.

[0033] Example 2

[0034] In this embodiment 2, the primary aerobic regulation zone includes aquatic plants, aquatic animals, and an aeration device; the water depth h1 in the primary aerobic regulation zone is 3.0m, and the hydraulic retention time t1 is 24h; the aeration device in the primary aerobic regulation zone is surface aeration; the primary anoxic zone is located directly below the primary aerobic regulation zone, and the packing material in the primary anoxic zone is ceramsite, granular activated carbon, activated coke, and biomass packing material, with a packing height H1 of 3.5m, a packing particle size of 150mm, and a packing hydraulic conductivity of 0.5m / s; the hydraulic retention time T1 in the primary anoxic zone is 16h; the effluent collection pipe uses a filter head; the secondary anoxic zone is located directly below the secondary aerobic regulation zone, and the primary aerobic regulation zone and the primary anoxic zone are connected to the secondary... A partition wall separates the aerobic regulation zone and the secondary anoxic zone. The primary and secondary anoxic zones are connected by a connecting pipe. The packing material in the secondary anoxic zone consists of gravel, pebbles, zeolite, and ceramsite, with a packing height (H2) of 3.0m, a particle size of 150mm, and a hydraulic conductivity of 0.5m / s. The hydraulic retention time (T2) in the secondary anoxic zone is 12h. The inlet water distribution pipe is located at the bottom of the packing material and uses a perforated pipe. The secondary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices. The water depth (h2) in the secondary aerobic regulation zone is 2.0m, and the hydraulic retention time (t2) is 18h. The aeration device in the secondary aerobic regulation zone is a fountain-type aeration system. The recirculation system includes a recirculation pump, a recirculation main pipe, and a recirculation distribution pipe. The recirculation pump is located in the secondary aerobic regulation zone with a recirculation ratio of 500%. The recirculation main pipe is connected to the recirculation distribution pipe and the connecting pipe between the primary and secondary anoxic zones. The recirculation distribution pipe is located in the middle of the primary anoxic zone and uses a filter head.

[0035] By adjusting the aeration rate, reflux ratio, and reflux flow rate, the removal of COD, NH3-N, or TN can be specifically enhanced.

[0036] Example 3

[0037] In this embodiment 3, the primary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h1 in the primary aerobic regulation zone is 2.5m, and the hydraulic retention time t1 is 20h; the aeration device in the primary aerobic regulation zone is a combination of surface aeration and bottom aeration; the primary anoxic zone is located directly below the primary aerobic regulation zone, and the packing material in the primary anoxic zone is gravel, activated carbon, and biomass packing material, with a packing height H1 of 2.0m, a packing particle size of 100mm, and a packing hydraulic conductivity of 0.35m / s; the hydraulic retention time T1 in the primary anoxic zone is 12h; the effluent collection pipe is a perforated pipe; the secondary anoxic zone is located directly below the secondary aerobic regulation zone, and the primary aerobic regulation zone and the primary anoxic zone are connected... A soil embankment is set between the secondary aerobic regulation zone and the secondary anoxic zone. The primary and secondary anoxic zones are connected by a connecting pipe. The secondary anoxic zone uses crushed stone as filler, with a filler height H2 of 1.8m, a filler particle size of 120mm, and a filler hydraulic conductivity of 0.4m / s. The hydraulic retention time T2 in the secondary anoxic zone is 10h. The inlet water distribution pipe is located at the bottom of the filler and uses a filter head. The secondary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices. The water depth h2 in the secondary aerobic regulation zone is 1.5m, and the hydraulic retention time t2 is 12h. The aeration devices in the secondary aerobic regulation zone are a combination of fountain-type aeration and bottom aeration. The recirculation system includes a recirculation pump, a recirculation main pipe, and a recirculation distribution pipe. The recirculation pump is located in the secondary aerobic regulation zone, with a recirculation ratio of 300%. The recirculation main pipe is connected to the recirculation distribution pipe and the connecting pipe between the primary and secondary anoxic zones. The recirculation distribution pipe is located in the middle of the primary anoxic zone and uses a perforated pipe.

[0038] Example 4

[0039] In this embodiment 4, the primary aerobic regulation zone includes aquatic plants, aquatic animals, and an aeration device; the water depth h1 in the primary aerobic regulation zone is 0.8m, and the hydraulic retention time t1 is 14h; the aeration device in the primary aerobic regulation zone is bottom aeration; the primary anoxic zone is located directly below the primary aerobic regulation zone, and the packing material in the primary anoxic zone is gravel, pebbles, activated carbon, and biomass packing material, with a packing height H1 of 1.0m, a packing particle size of 30mm, and a packing hydraulic conductivity of 0.1m / s; the hydraulic retention time T1 in the primary anoxic zone is 10h; the effluent collection pipe is a perforated pipe; the secondary anoxic zone is located directly below the secondary aerobic regulation zone, and the primary aerobic regulation zone and the primary anoxic zone are connected to the secondary... An earthen embankment is set between the aerobic regulation zone and the secondary anoxic zone. The primary and secondary anoxic zones are connected by a connecting pipe. The packing material in the secondary anoxic zone is zeolite, ceramsite, and crushed stone, with a packing height H2 of 1.2m, a packing particle size of 25mm, and a hydraulic conductivity of 0.08m / s. The hydraulic retention time T2 in the secondary anoxic zone is 9h. The inlet water distribution pipe is located at the bottom of the packing material and uses a filter head. The secondary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices. The water depth h2 in the secondary aerobic regulation zone is 1.0m, and the hydraulic retention time t2 is 15h. The aeration device in the secondary aerobic regulation zone is bottom aeration. The recirculation system includes a recirculation pump, a recirculation main pipe, and a recirculation distribution pipe. The recirculation pump is located in the secondary aerobic regulation zone, with a recirculation ratio of 200%. The recirculation main pipe is connected to the recirculation distribution pipe and the connecting pipe between the primary and secondary anoxic zones. The recirculation distribution pipe is located in the middle of the primary anoxic zone and uses a perforated pipe.

[0040] By adjusting the aeration rate, reflux ratio, and reflux flow rate, the removal of COD, NH3-N, or TN can be specifically enhanced.

[0041] Example 5

[0042] In this embodiment 5, the primary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices; the water depth h1 in the primary aerobic regulation zone is 2.2m, and the hydraulic retention time t1 is 17h; 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 material in the primary anoxic zone is gravel and biomass packing material, with a packing height H1 of 1.6m, a packing particle size of 80mm, and a packing hydraulic conductivity of 0.28m / s; the hydraulic retention time T1 in the primary anoxic zone is 13h; the effluent collection pipe uses a filter head; the secondary anoxic zone is located directly below the secondary aerobic regulation zone, and the primary aerobic regulation zone and the primary anoxic zone are connected to the secondary aerobic regulation zone. A partition is installed between the primary aerobic regulation zone and the secondary anoxic zone. The primary and secondary anoxic zones are connected by a connecting pipe. The packing material in the secondary anoxic zone is zeolite and ceramsite, with a packing height H2 of 1.8m, a packing particle size of 50mm, and a hydraulic conductivity of 0.14m / s. The hydraulic retention time T2 in the secondary anoxic zone is 12h. The inlet water distribution pipe is located at the bottom of the packing material and uses a perforated pipe. The secondary aerobic regulation zone includes aquatic plants, aquatic animals, and aeration devices. The water depth h2 in the secondary aerobic regulation zone is 1.7m, and the hydraulic retention time t2 is 16.5h. The aeration device in the secondary aerobic regulation zone is bottom aeration. The recirculation system includes a recirculation pump, a recirculation main pipe, and a recirculation distribution pipe. The recirculation pump is located in the secondary aerobic regulation zone with a recirculation ratio of 350%. The recirculation main pipe is connected to the recirculation distribution pipe and the connecting pipe between the primary and secondary anoxic zones. The recirculation distribution pipe is located in the middle of the primary anoxic zone and uses a filter head.

[0043] By adjusting the aeration rate, reflux ratio, and reflux flow rate, the removal of COD, NH3-N, or TN can be specifically enhanced.

[0044] Example 6

[0045] Based on the above embodiments, this embodiment provides a method for enhanced removal of COD, NH3-N, and TN:

[0046] (A) When the influent COD or NH3-N or both of the above are high and TN is low, increase the aeration rate of the primary 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, NH3-N and TN are all high, increase the aeration rate of the primary 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 NH3-N or both of the above are low and TN is high, reduce the aeration rate of the primary 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, NH3-N and TN are all low, reduce the aeration rate of the primary aerobic regulation zone and the secondary aerobic regulation zone, reduce the reflux ratio and reduce the reflux flow rate;

[0050] (E) When the influent COD is high and both NH3-N and TN are low, increase the aeration rate in the primary and secondary aerobic regulation zones, reduce the reflux ratio, and decrease the reflux flow rate;

[0051] (F) When the influent COD is low and both NH3-N and TN are high, reduce the aeration rate of the primary aerobic regulation zone, increase the aeration rate of 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 with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described above. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Many other changes and modifications made without departing from the concept and scope of the present invention should be considered within the scope of protection of the present invention.

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

[0054] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for enhanced removal of COD, NH3-N, and TN using an embedded composite wetland system, wherein the method is based on an embedded composite wetland system, characterized in that: The embedded composite wetland system includes a primary regulating tank and a secondary regulating tank; wherein, The primary equalization tank is equipped with a primary aerobic equalization zone and a primary anoxic zone integrated below the primary aerobic equalization zone. The secondary equalization tank is equipped with a secondary aerobic equalization zone and a secondary anoxic zone integrated below the secondary aerobic equalization zone; The primary and secondary hypoxic zones are connected by a connecting pipe. The method includes the following steps: (A) When the influent COD and NH3-N are both high and TN is low, increase the aeration rate of the primary and secondary aerobic regulation zones, reduce the reflux ratio, and decrease the reflux flow rate; (B) When the influent COD, NH3-N and TN are all high, increase the aeration rate of the primary aerobic regulation zone and the secondary aerobic regulation zone, increase the reflux ratio and increase the reflux flow rate; (C) When the influent COD and NH3-N are both low and TN is high, reduce the aeration rate of the primary and secondary aerobic regulation zones, increase the reflux ratio, and increase the reflux flow rate; (D) When the influent COD, NH3-N and TN are all low, reduce the aeration rate in the primary aerobic regulation zone and the secondary aerobic regulation zone, reduce the reflux ratio and reduce the reflux flow rate; (E) When the influent COD is high and both NH3-N and TN are low, increase the aeration rate in the primary and secondary aerobic regulation zones, reduce the reflux ratio, and decrease the reflux flow rate; (F) When the influent COD is low and both NH3-N and TN are high, reduce the aeration rate of the primary aerobic regulation zone, increase the aeration rate of the secondary aerobic regulation zone, increase the reflux ratio, and increase the reflux flow rate.

2. The method for enhanced removal of COD, NH3-N, and TN using an embedded composite wetland system according to claim 1, characterized in that: It also includes a reflux system, which includes a reflux pump, a reflux inlet pipe, and a reflux distribution pipe; wherein the reflux inlet pipe is installed in the secondary regulating tank; and the reflux distribution pipe is installed in the primary regulating tank.

3. The method for enhanced removal of COD, NH3-N, and TN using an 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 in the primary aerobic regulation zone is 0.5~3.0m, and the hydraulic retention time t1 is 12~24h.

4. The method for enhanced removal of COD, NH3-N, and TN using an embedded composite wetland system according to claim 1, characterized in that: The primary anoxic zone is equipped with packing material and an effluent collection pipe. The packing material in the primary anoxic zone includes gravel, pebbles, zeolite, ceramsite, granular activated carbon, activated coke, and / or biomass packing material. The packing material height is 0.5~3.5m, the packing material particle size is 5~150mm, and the packing material hydraulic conductivity is 0.01~0.5m / s. The hydraulic retention time in the primary anoxic zone is 8~16h. An effluent collection pipe connected to a connecting pipe is installed at the bottom of the packing material.

5. The method for enhanced removal of COD, NH3-N, and TN using an embedded composite wetland system according to claim 1, characterized in that: The secondary anoxic zone is equipped with packing material and an inlet water distribution pipe. The packing material in the secondary anoxic zone is gravel, pebbles, zeolite, ceramsite and / or crushed stone. The packing material height is 1.0~3.0m, the packing material particle size is 15~150mm, and the packing material hydraulic conductivity is 0.02~0.5m / s. The hydraulic retention time in the secondary anoxic zone is 8~12h. An inlet water distribution pipe connected to a connecting pipe is installed at the bottom of the packing material.

6. The method for enhanced removal of COD, NH3-N and TN using an 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 in the secondary aerobic regulation zone is 0.5~2.0m, and the hydraulic retention time t2 is 12~18h.

7. The method for enhanced removal of COD, NH3-N and TN using an embedded composite wetland system according to claim 2, characterized in that: The return water distribution pipe is connected to the connecting pipe.

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