A high-efficiency and environment-friendly subsurface flow constructed wetland water source denitrification purification system

Abstract

This utility model relates to a highly efficient and environmentally friendly subsurface flow constructed wetland water source denitrification and purification system, comprising an constructed wetland. The bottom of the constructed wetland has a water-impermeable layer. Above the water-impermeable layer, from bottom to top, are arranged a fine sand protective layer, a gravel layer, a zeolite layer, and a denitrification layer. The denitrification layer has a multi-layer structure, including multiple layers of sulfur autotrophic filter media. Supporting filter media layers are arranged between adjacent sulfur autotrophic filter media layers. A water distribution pipe is installed within the constructed wetland, with several water inlets distributed on the pipe. The water distribution pipe is located within the gravel layer or between the gravel and zeolite layers. The constructed wetland is divided into several unit pools by unit partition walls. A water collection channel is provided around the perimeter of the constructed wetland, and the inner wall of the water collection channel serves as an overflow wall. Emergent and submerged plants are planted alternately in sections on the constructed wetland. This utility model can achieve sulfur autotrophic denitrification in the constructed wetland and helps maintain the pH within a suitable range, thus facilitating the long-term stable operation of the constructed wetland.

Description

Technical Field

[0001] This utility model relates to a highly efficient and environmentally friendly subsurface flow constructed wetland water denitrification and purification system. Background Technology

[0002] Constructed wetlands are artificially built and controlled wetland-like surfaces. Wastewater and sludge are systematically introduced onto these artificially constructed wetlands. During the flow of wastewater and sludge in a specific direction, the technology utilizes the synergistic physical, chemical, and biological processes of soil, artificial media, plants, and microorganisms to treat the wastewater and sludge. Its mechanisms include adsorption, retention, filtration, oxidation-reduction, sedimentation, microbial decomposition, transformation, plant shading, residue accumulation, transpiration of water and nutrients, and the action of various animals. Microorganisms in the wetland system are the main force in degrading pollutants in the water. Aerobic microorganisms decompose most of the organic matter in wastewater into carbon dioxide and water through respiration; anaerobic bacteria decompose organic matter into carbon dioxide and methane; nitrifying bacteria nitrify ammonium salts; and denitrifying bacteria reduce nitrate nitrogen to nitrogen gas, etc. Through this series of processes, the main organic pollutants in the wastewater are degraded and assimilated, becoming part of the microbial cells, while the remainder is transformed into harmless inorganic substances that return to nature. However, existing constructed wetlands rely on heterotrophic denitrification for nitrogen removal, which requires continuous addition of carbon sources. This results in high operating costs, and excessive carbon sources can easily cause secondary pollution. Insufficient or excessive carbon sources can also lead to nitrogen removal failure, and carbon source leakage may cause eutrophication of water bodies, affecting the practical application effect.

[0003] On the other hand, in the field of advanced nitrogen removal from municipal sewage and industrial wastewater, sulfur autotrophic denitrification technology has been applied. Compared with traditional heterotrophic denitrification technology, sulfur autotrophic denitrification has advantages such as high denitrification efficiency and high-efficiency nitrogen removal. However, during sulfur autotrophic denitrification, sulfur is oxidized to sulfate, leading to an increase in sulfate concentration in the effluent, which may cause secondary pollution to the receiving water body and affect the aquatic ecosystem. Furthermore, sulfate and low pH environments may inhibit the growth of wetland plants. These factors contradict the current general understanding of constructed wetlands, limiting the effective application of sulfur autotrophic denitrification technology in constructed wetlands. Utility Model Content

[0004] The purpose of this invention is to achieve sulfur autotrophic denitrification in constructed wetlands.

[0005] The technical solution of this utility model is: a highly efficient and environmentally friendly subsurface flow constructed wetland water source denitrification and purification system, including an constructed wetland (or wetland body), with a water-proof layer (or seepage-proof layer) at the bottom of the constructed wetland, and a fine sand protection layer, a gravel layer, a zeolite layer and a denitrification layer arranged sequentially from bottom to top above the water-proof layer, and the denitrification layer is provided with a sulfur self-trophic filter material layer.

[0006] The crushed stone that makes up the crushed stone layer can be graded crushed stone.

[0007] A non-woven fabric (or non-woven fabric layer) is placed between the fine sand protective layer and the gravel layer.

[0008] Artificial wetlands may or may not have a cinder layer located between the fine sand protective layer and the gravel layer. When a cinder layer is present, non-woven fabric is preferably provided between the fine sand protective layer and the cinder layer, as well as between the cinder layer and the gravel layer.

[0009] The waterproof layer can be made of bentonite waterproofing blanket.

[0010] Preferably, the constructed wetland is provided with a water distribution pipe, and the water distribution pipe has a number of water distribution outlets (e.g., water distribution through holes opened on the wall).

[0011] Preferably, the water distribution pipe is located within the gravel layer or between the gravel layer and the zeolite layer.

[0012] A wetland water distribution pipeline system consisting of a main water distribution pipe and branch water distribution pipes can be set up. The main water distribution pipe is used to connect wastewater (water to be treated) to the branch water distribution pipes. The main water distribution pipe is used as a water distribution pipe, and its inlet end is connected to the main water distribution pipe.

[0013] Typically, multiple branch pipes are connected to the same water distribution pipe.

[0014] Preferably, the water inlet channel is located in the middle of the transverse direction of the constructed wetland, and the main water distribution pipes are distributed on both sides of the water inlet channel.

[0015] Preferably, the water inlet channel consists of an inlet channel and a distribution channel. There are two distribution channels located on both sides of the inlet channel. The longitudinal partition wall between the inlet channel and the distribution channel is used as an overflow wall. The water in the inlet channel overflows into the corresponding distribution channel through the longitudinal partition wall. The inlet of the main water distribution pipe is connected to the distribution channel and is supplied with water by the distribution channel. The raw water (water to be treated) is connected to the inlet channel of the inlet channel.

[0016] Preferably, a water collection channel is provided around the artificial wetland, and the inner wall of the water collection channel is used as an overflow wall. Water from the upper part of the wetland (water treated by the artificial wetland, or clean water) overflows into the water collection channel through the inner wall of the water collection channel.

[0017] A water outlet channel (e.g., an outlet pipe) can be installed on the water collection channel to draw out the treated water.

[0018] Preferably, the constructed wetland is divided into several unit pools by unit partition walls.

[0019] The main water distribution pipe corresponding to the unit pool is located in the longitudinal middle of the unit pool. The branch water distribution pipes within the unit pool are located on both sides of the main water distribution pipe. Within the same unit pool, the branch water distribution pipes on either side of the main water distribution pipe are roughly evenly distributed. The distribution of the branch water distribution pipes can be reasonably set or appropriately adjusted according to the specific shape of the unit pool to achieve basically uniform water distribution. If necessary, branch water distribution pipes with different inlet densities and / or inlet flow areas can be used for appropriate resistance compensation and flow rate adjustment.

[0020] The same water distribution main pipe can supply water to only one unit pool, or it can extend to multiple unit pools to supply water to multiple unit pools.

[0021] The upper part or all of the water intake channel may be paved with a road surface structure to serve as a road and / or work platform.

[0022] The top of the water collection channel (partial or all of the area) may be paved with a road structure to serve as a road and / or work platform.

[0023] A dock can be set up next to the water intake channel used as a road, and a large working platform can also be set up.

[0024] The denitrification layer adopts a multi-layer structure, with multiple layers of sulfur autotrophic filter media and a supporting filter media layer between adjacent sulfur autotrophic filter media layers.

[0025] The sulfur autotrophic filter media that makes up the sulfur autotrophic filter media layer is in granular form, for example, slow-release high-efficiency sulfur autotrophic filter media granules.

[0026] The supporting filter media that makes up the supporting filter media layer is granular with the same (or substantially the same, i.e., particle sizes that are allowed to be substituted for each other in practice) particle size as the sulfur autotrophic filter media. Therefore, the sulfur autotrophic filter media and the supporting filter media are granular with the same or similar particle size.

[0027] The top layer of the denitrification layer can be either a sulfur autotrophic filter media layer or a supporting filter media layer; the bottom layer of the denitrification layer can also be either a sulfur autotrophic filter media layer or a supporting filter media layer.

[0028] Preferably, each sulfur-autotrophic filter media layer has the same thickness.

[0029] Preferably, each supporting filter layer has the same thickness (when the supporting filter layer has multiple layers).

[0030] Preferably, emergent plants are planted on the artificial wetland.

[0031] Preferably, submerged plants are also planted in the artificial wetland, with emergent and submerged plants planted alternately in different areas.

[0032] The beneficial effects of this invention are as follows: Due to the inclusion of a denitrification layer, low-valence sulfur provided by the sulfur autotrophic filter media serves as an electron donor. Under the action of sulfur autotrophic denitrifying microorganisms, the denitrification process is completed through sulfur oxidation and nitrogen reduction reactions, without the need for external organic carbon sources. This avoids the costs and risks associated with adding organic carbon sources and maintaining reasonable carbon source levels, and also helps reduce sludge production and maintain the long-term stable operation of constructed wetlands. Furthermore, because the denitrification layer is divided into sulfur autotrophic filter media and supporting filter media, and slow-release sulfur autotrophic filter media can be used, the amount of sulfur autotrophic filter media can be effectively controlled while meeting the requirements for the total thickness (vertical dimension) of the denitrification layer, thereby controlling the pH in the wetland and preventing excessive pH drop due to excessive sulfur autotrophic filter media. Additionally, when replenishing or replacing the sulfur autotrophic filter media, the entire denitrification layer's filter media can be... The filter media is screened and reused (reuse rate ≥85%), with new sulfur-autotrophic denitrification filter media added as needed. The presence of a zeolite layer helps maintain the wetland's acid-base balance and ensures stable operation and effluent quality through the adsorption and release mechanism of calcium and magnesium. The planting of aquatic plants helps maintain the constructed wetland's ecosystem and improves its purification capacity. The alternating planting of submerged and emergent plants helps avoid mutual interference. The photosynthesis of submerged plants such as *Vallisneria natans*, *Elodea nuttallii*, and *Hydrilla verticillata* helps increase wetland alkalinity and maintain a reasonable pH level. Furthermore, the synergy between emergent and submerged plants maintains a healthy aquatic ecosystem and enhances the wetland's purification capacity. The presence of a cinder layer further improves the wetland's pH and increases phosphorus removal capacity.

[0033] This invention, through the synergy of multiple technical means, achieves sulfur autotrophic denitrification while maintaining pH within a suitable range (e.g., 6-8), thus facilitating the long-term stable operation of constructed wetlands. Attached Figure Description

[0034] Figure 1 This is a top view of one embodiment of the present invention;

[0035] Figure 2 Is with Figure 1 Corresponding AA cross-sectional view;

[0036] Figure 3 Is with Figure 1 Corresponding BB cross-section;

[0037] Figure 4 This is a schematic diagram of the structure of the main body of the artificial wetland involved in this utility model.

[0038] The markings in the diagram are: 11. Bentonite waterproof blanket; 12. Fine sand protective layer; 13. Non-woven fabric; 14. Graded crushed stone layer; 15. Zeolite layer; 16. Denitrification layer; 17. Purification layer; 20. Channel; 21. Inlet channel; 22. Distribution channel; 23. Main water distribution pipe; 24. Branch water distribution pipe; 27. Valve well; 28. Collection channel; 29. ​​Outlet pipe; 31. Emergent plants; 32. Submerged plants; 41. Longitudinal partition wall; 42. Unit partition wall; 43. Road surface; 45. Dock; 46. Road. Detailed Implementation

[0039] This invention applies slow-release autotrophic sulfur denitrification filter media to constructed wetlands, supplemented with traditional typical filter media to slow down the reaction rate of the filter media. By rationally arranging the filter bed structure and designing a multi-compartment filter bed, it allows for the screening and reuse of crushed stone, zeolite, and unconsumed autotrophic sulfur denitrification filter media. After replenishing with new filter media, it backfills in situ, thereby ensuring the denitrification and purification effect and stability, and reducing operating costs.

[0040] 1. Wetland Structure and Technical Principles

[0041] See Figures 1 to 3 A large-scale submerged biological filter bed composed of multi-stage filter media is constructed to form a highly efficient and environmentally friendly water denitrification and purification system. Commercially available sulfur autotrophic denitrification filter media (slow-release sulfur autotrophic denitrification filter media) is used to achieve sulfur autotrophic denitrification, supplemented by ordinary granular filter media (which can be called support filter media) with a similar particle size. Depending on the required amount of sulfur autotrophic denitrification filter media, sulfur autotrophic filter media layers and support filter media layers are alternately arranged in the denitrification layer (for example, three layers of sulfur autotrophic filter media of equal thickness and two layers of support filter media of equal thickness). The constructed wetland area is divided into several unit ponds, and corresponding hydraulic distribution devices are installed. Sulfur- and acid-tolerant emergent plants 31, such as cattails and reeds, are selected for planting according to climatic conditions. Emergent and submerged plants 32, such as Vallisneria natans, Elodea nuttallii, and Hydrilla verticillata, can be planted alternately in different areas to form a healthy aquatic ecosystem.

[0042] In the case of large-scale constructed wetlands, the water distribution system includes an inlet channel 21, a distribution channel 22, a main distribution pipe 23, and branch distribution pipes 24. Water is introduced into the inlet channel, which runs through / basically through the constructed wetland. The distribution channels are located on both sides of the inlet channel. A longitudinal partition wall 41 can be installed within the channel (water channel) 20 to divide the channel into an inlet channel located in the transverse (horizontal direction perpendicular to the longitudinal direction) middle and two distribution channels located on either side of the inlet channel. The longitudinal partition wall within the channel serves as an overflow wall, allowing water in the inlet channel to overflow into the distribution channels through the top of the partition wall. Based on the water distribution needs of each unit pool, several transverse main distribution pipes are led out from the distribution channel. These main distribution pipes extend longitudinally from the middle of the corresponding unit pool, with several branch distribution pipes leading out from both sides. Water distribution holes are provided on the water distribution branch pipes for distributing water under the wetland. The valve wells 27 of each water distribution main pipe are located on the outside of the corresponding water distribution channel. Valves and instruments (such as pressure gauges and flow meters) on the inlet side of the main water distribution pipe can be installed in the valve wells according to actual needs to facilitate maintenance and management.

[0043] The main body of the constructed wetland, from bottom to top, consists of a fine sand protective layer 12, a graded crushed stone layer 14, a zeolite layer 15, and a multi-layered denitrification layer 16, topped with a water purification layer 17. Bentonite waterproofing blanket 11 is laid under the fine sand protective layer, and non-woven fabric 13 is laid on top (between the fine sand protective layer and the graded crushed stone layer). The main water distribution pipe 23 and branch water distribution pipes 24 are located within the graded crushed stone layer or between the graded crushed stone layer and the zeolite layer (see [reference]). Figure 4 The main water distribution pipes are set according to the distribution of the unit pools, so that each unit pool has a main water distribution pipe in the longitudinal center. The distribution density of the branch water distribution pipes (the distance between adjacent branch pipes) is set according to the water distribution needs.

[0044] A vent pipe 25 extending vertically upwards above the water surface is installed on the water distribution main pipe. A vent cap is installed on the top of the vent pipe. The location and distribution of the vent pipe can be determined based on existing technology.

[0045] Adjacent unit pools are separated by unit partition walls 42, the height of which can be higher than the wetland water level. If necessary, permeable holes can be installed in the partition walls between unit pools.

[0046] The longitudinal partition walls, unit partition walls, and the inner walls of the water collection channel are made of reinforced concrete.

[0047] A collection channel 28 is constructed around the constructed wetland. The collection channel can be circular (a complete ring) and is made of reinforced concrete. The inner wall serves as an overflow wall, and the outer wall serves as a retaining wall, higher than the inner wall and the water level of the collection channel. The clean water from the upper layer of the wetland flows into the collection channel via overflow. Outlet pipes 29 are installed on the collection channel. The number of outlet pipes can be one or more, depending on actual needs.

[0048] Since these artificial wetlands typically occupy a large area, roads 46 can be built across the artificial wetlands as needed, and work docks 45 can be set up within the wetlands.

[0049] A road surface 43 can be laid over channel 20 to form a road. In this case, the channel foundation, the walls supporting the road surface, and the structures comprising the road surface should meet the requirements of the corresponding road. The work dock can be set up according to the channel that can be used as a road, realizing the connection between land and water transportation.

[0050] 2. Construction steps and key points

[0051] 1) Construction process flow

[0052] Submerged biological filter bed structure → laying of impermeable blanket → laying of water distribution pipes → laying of various conventional filter media and autotrophic denitrification filter media → planting of plants

[0053] 2) Laying of impermeable blankets

[0054] The filter bed is protected against seepage using a sodium-based bentonite waterproof blanket with a specification of 4500g / ㎡. To prevent the waterproof blanket from being punctured by the filler, a 400mm thick fine sand protective layer and a 300g / ㎡ non-woven fabric layer are laid on top of the waterproof blanket. The non-woven fabric, fine sand protective layer and waterproof blanket are installed in sequence from bottom to top.

[0055] 3) Laying of water distribution pipelines

[0056] The water distribution pipeline includes main pipes, branch pipes, and vent pipes. The main pipes are DN300 UPVC pipes, 1.0 MPa. The branch pipes are DN65 UPVC perforated pipes, 1.0 MPa, with 8mm diameter, perfectly round perforations spaced 100mm apart, arranged in two rows at a 45° downward angle. The vent pipes are DN110 UPVC pipes, 1.0 MPa, connected perpendicularly to the main pipes. Two vent pipes are installed in each unit, with vent caps installed on top of each vent pipe, extending 300mm above the filter bed. The main pipes are connected to the branch pipes using four-way connectors, and to the vent pipes using three-way connectors. Filler cores are installed as needed.

[0057] 4) Wetland main body laying

[0058] The packing material consists of three layers: a 460mm denitrification layer with a particle size of 8-12mm, a 200mm zeolite layer with a particle size of 8-16mm, and a 200mm graded crushed stone layer with a particle size of 16-32mm. Above the packing material is a 440mm water purification layer controlled by overflow.

[0059] i) Denitrification layer

[0060] Sulfur autotrophic filter media (high-efficiency autotrophic denitrification filter media) are artificially synthesized, high-porosity, slow-release, and regularly spherical solid particles with a comprehensive specific surface area ≥0.5㎡ / g. The filter media used in the denitrification layer includes two types of particles: one is sulfur autotrophic (denitrification) filter media, granular with a sulfur content ≥40%, primarily providing the reduced electrons and biofilm space needed by autotrophic denitrifying microorganisms during the denitrification process; the other is conventional granular filter media (or packing material) used for water treatment, which can be called support filter media. Its particle size is similar to that of the sulfur autotrophic filter media, and it can be selected to contain trace mineral elements to facilitate the rapid proliferation of autotrophic denitrifying bacteria. Because these two types of filter media have similar appearances, they can be distinguished by different colors according to their functions. The two types of filter media can be layered, with the support filter media layer placed between the two sulfur autotrophic filter media layers to provide sufficient biofilm space, playing a role in alkalinity balance during denitrification and supporting the filter bed framework. The number of layers (the thickness of each layer) can be set appropriately according to actual needs, reducing workload while meeting treatment requirements. The ratio of the two types of filter media is determined based on the volume of the denitrification layer (total filter media requirement) and the amount of sulfur-autotrophic filter media required according to water treatment needs. The layer thickness of the same type of filter media can be equal. When appropriate, the two types of filter media can also be purchased directly from the market and mixed in an appropriate ratio to fill the entire denitrification layer.

[0061] In practice, the amount of sulfur autotrophic filter media can be determined or adjusted according to the daily water purification volume. The supporting filter media can be prepared using the same substrate as the sulfur autotrophic filter media, or volcanic rock filter media, biological ceramic particles, etc.

[0062] Due to the consumption of sulfur autotrophic filter media, it is necessary to replenish or replace it after long-term use, usually every 3 years. When replenishing, unused (usable) sulfur autotrophic filter media can be screened and reused.

[0063] ii) Zeolite layer

[0064] Material selection requirements: The raw material should be zeolite with a particle size of 8-16mm. The filler must be clean, dry, and free of organic matter, lumps or clumps of soil, debris, and other harmful substances.

[0065] Chemical requirements: It has strong stability, does not dissolve in water, and does not contain toxic substances (the water quality indicators meet the national Class III surface water standard after soaking in pure water for 72 hours).

[0066] Other characteristics: Zeolite is light-colored, with a vitreous luster, a hardness of 3-3.5, and a specific gravity of 2.0-2.4.

[0067] iii) Graded crushed stone

[0068] Material selection requirements: The raw material is 16-32mm graded crushed stone. The calcium content of the material shall not be less than 2.5kg / 100kg. The aggregate must be clean, dry, well graded, and free of organic matter, lumps or clumps of soil, debris, and other harmful substances.

[0069] Chemical properties: It has strong stability, does not dissolve in water, and does not contain toxic substances (after soaking in pure water for 72 hours, the water quality indicators meet the national Class III surface water standard).

[0070] Other: The content of powdery substances in the crushed stone should be less than 1%.

[0071] A cinder layer, for example, 200mm-500mm thick with a particle size of 2-5mm, can be placed between the graded crushed stone layer and the nonwoven fabric above the fine sand protective layer. In this case, the thickness of the graded crushed stone layer and / or the fine sand protective layer can be appropriately reduced (e.g., halved), or the thickness of the graded crushed stone layer and / or the fine sand protective layer can be kept constant. If necessary, nonwoven fabric can be placed between the graded crushed stone layer and the cinder layer.

[0072] Since large-scale constructed wetlands are usually set up according to the actual terrain, the terms "longitudinal" and "lateral" can both refer to curved directions to indicate the relative orientation between various structures. The longitudinal direction is the extension direction of the inlet channel / channel. Structures that are parallel or roughly parallel to the inlet channel / channel (e.g., water distribution branch pipes) are also described as longitudinal, while structures that are perpendicular or roughly perpendicular to the inlet channel / channel (e.g., water distribution main pipes) are described as lateral. For non-circular structures that have a large curvature due to changes in terrain, the direction of the part that connects to or is adjacent to the inlet channel / channel is used as the reference.

[0073] Valves and instruments / sensors can be installed according to actual needs. For example, an outlet control valve can be installed on the outlet pipe, and an inlet control gate can be installed at the inlet of the inlet channel. Based on the flow meter data of the main and branch water distribution pipes, the flow of each main and branch water distribution pipe can be controlled by relevant valves to achieve reasonable distribution of water inlet to each unit pool and water outlet from each branch water distribution pipe. The water level of each part can be detected in real time by a water level gauge.

[0074] Unless otherwise specified, the preferred and optional technical means disclosed in this utility model can be arbitrarily combined to form several different specific embodiments when one preferred or optional technical means is a further limitation of another technical means.

Claims

1. A highly efficient and environmentally friendly subsurface flow constructed wetland water denitrification and purification system, comprising an constructed wetland, wherein the bottom of the constructed wetland is provided with a water-impermeable layer, characterized in that... Above the waterproof layer, from bottom to top, there are a fine sand protective layer, a gravel layer, a zeolite layer and a denitrification layer. The denitrification layer is equipped with a sulfur self-nourishing filter media layer.

2. The subsurface flow constructed wetland water denitrification and purification system as described in claim 1, characterized in that... The constructed wetland is equipped with a water distribution pipe with several water outlets. The water distribution pipe is located within the gravel layer or between the gravel layer and the zeolite layer.

3. The subsurface flow constructed wetland water denitrification and purification system as described in claim 2, characterized in that... The water inlet channel is located in the middle of the transverse direction of the constructed wetland, and the main water distribution pipes are distributed on both sides of the water inlet channel.

4. The subsurface flow constructed wetland water denitrification and purification system as described in claim 3, characterized in that... The water intake channel consists of an intake canal and a distribution canal. There are two distribution canals located on both sides of the intake canal. The longitudinal partition wall between the intake canal and the distribution canal serves as an overflow wall. The inlet of the main water distribution pipe is connected to the distribution canal.

5. The subsurface flow constructed wetland water denitrification and purification system as described in any one of claims 1-4, characterized in that... The artificial wetland is surrounded by a water collection channel, and the inner wall of the water collection channel is used as an overflow wall.

6. The subsurface flow constructed wetland water denitrification and purification system as described in any one of claims 1-4, characterized in that... Artificial wetlands are divided into several unit pools by unit partitions.

7. The subsurface flow constructed wetland water denitrification and purification system as described in any one of claims 1-4, characterized in that... The denitrification layer adopts a multi-layer structure, with multiple layers of sulfur autotrophic filter media and a supporting filter media layer between adjacent sulfur autotrophic filter media layers.

8. The subsurface flow constructed wetland water denitrification and purification system as described in claim 7, characterized in that... Each sulfur-autotrophic filter media layer has the same thickness, and each supporting filter media layer has the same thickness.

9. The subsurface flow constructed wetland water denitrification and purification system as described in claim 1, characterized in that... Emergent plants are planted in artificial wetlands.

10. The subsurface flow constructed wetland water denitrification and purification system as described in claim 9, characterized in that... The artificial wetland is also planted with submerged plants, and emergent and submerged plants are planted in alternating zones.

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