One-way seepage artificial wetland system of anti-reflux boundary

Abstract

The invention belongs to the technical field of sewage treatment systems, and particularly relates to a one-way seepage artificial wetland system with an anti-reflux boundary, which comprises an artificial wetland unit and a soil unit coupled with the artificial wetland unit through an anti-reflux boundary unit, the anti-backflow boundary unit is of a net structure and comprises a wedge-shaped grid and a boundary defining the wedge-shaped grid. The wedge-shaped grids are filled with a high-permeability material; the boundary is made of a low-permeability material; the boundary of the water outlet end of the constructed wetland unit is an open end of the wedge-shaped grid; and the bottom boundary of the water inlet end of the constructed wetland unit is higher than that of the water outlet end of the constructed wetland. According to the system, the effluent of the constructed wetland can unidirectionally flow into the soil through the anti-reflux boundary, the hydraulic communication between the constructed wetland and the soil is maintained, the purification potential of the soil is utilized, and the system stability risk caused by the reverse fluctuation of the external water level is avoided; fusion of an artificial wetland ecological restoration system and a natural system and synchronous enhanced reduction of pollutants are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment systems, and particularly relates to a one-way seepage constructed wetland system with an anti-backflow boundary. Background Art

[0002] With the rapid development of industry and agriculture and the acceleration of urbanization, the eutrophication of water bodies caused by the superposition of point source and non-point source pollution has become increasingly severe, seriously weakening the ecological functions of natural water bodies. Against this background, the constructed wetland technology with both ecological benefits and purification functions has become an important means for the restoration of urban landscape water bodies, the treatment of rural sewage, and the interception of non-point source pollution. However, currently, the constructed wetland system generally adopts a rigid anti-seepage boundary design (permeability coefficient < 10 -6 m / s), which, although able to effectively control the hydraulic path, leads to two major key ecological contradictions:

[0003] First, physical isolation causes the fragmentation of the hydrological cycle. The traditional anti-seepage wall blocks the hydraulic connection between the constructed wetland and the surrounding soil vadose zone, creating an "ecological island". This "ecological island" effect not only violates the concepts of natural accumulation, infiltration, and purification in the construction of sponge cities, but also causes the wetland system to lose its co-purification ability with the soil. Research shows that the soil vadose zone, as a multi-medium system with coexistence of gas phase - liquid phase - solid phase, its rich microbial community and adsorption interface can achieve efficient nitrogen removal through nitrification / denitrification (up to 20 - 35 mg-N / kg·d), but the rigid anti-seepage design makes this natural purification layer unable to be effectively utilized.

[0004] Second, the dynamic water level causes risks to the system stability. In the previously developed constructed wetland system that can be flexibly integrated with the soil vadose zone, although the hydraulic connection between the wetland and the vadose zone is achieved through a permeable boundary, the reverse fluctuation effect of the external water level is not considered. When the groundwater level rises sharply during the flood season, the eutrophicated return liquid generated by the denitrification in the vadose zone will flow back into the wetland interior along the hydraulic gradient. Experimental data shows that such backflow can cause the ammonia nitrogen concentration in the wetland effluent to rebound by 6.8 - 9.2 mg / L, seriously damaging the activity of aerobic bacteria in the system (the ATP content decreases by 42%), resulting in a cliff-like decline in the treatment efficiency.

[0005] In the existing technology, attempts are made to relieve the backflow by setting a gravel transition layer, but its homogeneous structure is difficult to form a directional hydraulic gradient, and although the electric cut-off valve scheme proposed abroad can block the backflow, it loses ecological sustainability due to excessive energy consumption (> 3.2 kWh / m 3 ). How to construct a boundary structure that can not only maintain hydraulic connection to utilize the purification potential of the vadose zone but also adaptively regulate the flow direction has become the key bottleneck for improving the robustness and ecological compatibility of the constructed wetland system. Summary of the Invention

[0006] The object of the present invention is to provide a one-way seepage constructed wetland system with an anti-backflow boundary. The system provided by the present invention can make the effluent of the constructed wetland flow into the soil unidirectionally through the anti-backflow boundary, maintain the hydraulic connection between the constructed wetland and the soil to utilize the purification potential of the soil, avoid the system stability risk caused by the reverse fluctuation of the external water level, and realize the integration of the constructed wetland ecological restoration system and the natural system and the enhanced reduction of pollutants synchronously.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a one-way seepage constructed wetland system with an anti-backflow boundary, including a constructed wetland unit 1 and a soil unit 3 coupled to the constructed wetland unit 1 through an anti-backflow boundary unit 2;

[0009] The anti-backflow boundary unit 2 is a mesh structure, including a wedge-shaped grid 2-1 and a boundary surrounding the wedge-shaped grid 2-1; the wedge-shaped grid is filled with a high-permeability material; the material of the boundary is a low-permeability material;

[0010] The outlet end boundary of the constructed wetland unit 1 is the open end of the wedge-shaped grid 2-1;

[0011] The bottom boundary of the inlet end of the constructed wetland unit 1 is higher than the bottom boundary of the outlet end of the constructed wetland unit 1.

[0012] Preferably, a drainage pipe 1-11 is also laid at the bottom of the anti-backflow boundary unit 2.

[0013] Preferably, the width of the anti-backflow boundary unit 2 is 20-50 cm.

[0014] Preferably, the wedge angle 2-4 of the wedge-shaped grid 2-1 is 15-30°, and the wedge length is the width of the anti-backflow boundary unit 2; the vertical heights of the open end 2-2 and the closed end 2-3 of the wedge-shaped grid 2-1 are equal, being 10-30 cm; the horizontal width of the open end 2-2 of the wedge-shaped grid 2-1 is 10.3-31.8 cm; the horizontal width of the closed end 2-3 of the wedge-shaped grid 2-1 is 2-5 cm.

[0015] Preferably, the boundary includes a horizontal boundary 2-6 and a longitudinal boundary 2-5; the vertical height of the horizontal boundary 2-6 is 5-10 cm; the shape of the longitudinal boundary 2-5 is an isosceles triangular prism; the bottom vertex angle of the isosceles triangular prism is 15-30°, which is equal to the wedge angle 2-4 of the wedge-shaped grid 2-1.

[0016] Preferably, the permeability coefficient of the low-permeability material is 0.1-1.0 m / d; the permeability coefficient of the high-permeability material is 10-20 m / d.

[0017] Preferably, the constructed wetland unit 1 includes a water distribution area 1-2; a water inlet pipe 1-1 is arranged in the water distribution area 1-2;

[0018] a main filler area 1-3 connected to the water distribution area 1-2; wetland plants 1-4 are planted in the main filler area 1-3;

[0019] an outlet area 1-5 connected to the main filler area 1-3.

[0020] Preferably, the filling height range of the main filler area 1-3 is 0.8 to 1.5 m, and the permeability coefficient is 50.0 to 100.0 m / d.

[0021] Preferably, the angle 1-10 between the bottom boundary of the constructed wetland unit 1 and the horizontal plane is 1 to 3°.

[0022] Preferably, the soil unit 3 is provided with a sump 1-12 connected to the drain pipe; an overflow hole 1-13 is arranged in the sump 1-12.

[0023] The present invention provides a unidirectional seepage constructed wetland system with an anti-backflow boundary, which includes a constructed wetland unit 1 and a soil unit 3 coupled to the constructed wetland unit 1 through an anti-backflow boundary unit 2; the anti-backflow boundary unit 2 is a mesh structure, including wedge-shaped meshes 2-1 and a boundary surrounding the wedge-shaped meshes 2-1; the wedge-shaped meshes 2-1 are filled with a highly permeable material; the material of the boundary is a low-permeable material; the outlet end boundary of the constructed wetland unit 1 is the open end of the wedge-shaped meshes 2-1; the bottom boundary of the inlet end of the constructed wetland unit 1 is higher than the bottom boundary of the outlet end of the constructed wetland. In the system of the present invention, the bottom boundary of the inlet end of the constructed wetland is higher than the bottom boundary of the outlet end, so a natural hydraulic gradient will be formed to drive the unidirectional flow of water. The outlet end boundary of the constructed wetland is an anti-backflow boundary, and the anti-backflow boundary includes a mesh and a boundary. The mesh is filled with a highly permeable seepage material, and the boundary is a low-permeable material. The effluent after being treated by the constructed wetland unit, a part of it enters each wedge-shaped mesh filled with a highly permeable material through the open end of the wedge-shaped mesh for enhanced treatment, and then flows out from the closed end of the wedge-shaped mesh and enters the soil unit. Based on the denitrification ability of the soil, the denitrification effect is further enhanced. Finally, the effluent further purified by the soil unit is discharged into the natural system to realize the integration of the constructed wetland and the natural system. Another part of the effluent that cannot enter the soil unit through the anti-backflow boundary structure enters the sump through the drain pipe, and then is discharged through the overflow hole on the sump. Therefore, the unidirectional seepage constructed wetland system with the anti-backflow boundary structure disclosed in the present invention changes the anti-seepage boundary at the outlet end of the conventional constructed wetland into an anti-backflow unidirectional permeable boundary, so that the effluent of the constructed wetland flows unidirectionally into the soil through the anti-backflow boundary, maintains the hydraulic connection between the constructed wetland and the soil to utilize the purification potential of the soil, and avoids the system stability risk caused by the reverse fluctuation of the external water level, realizing the integration of the constructed wetland ecological restoration system and the natural system and the synchronous enhanced reduction of pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a plan view of a unidirectional seepage system with an anti-backflow boundary;

[0026] Figure 2 It is a sectional view taken along line A-A' of a unidirectional seepage system with an anti-backflow boundary;

[0027] Figure 3 It is a left view of a sectional view taken along line B-B' of the anti-backflow boundary unit;

[0028] Figure 4 Left view of the C-C' section of the anti-backflow boundary unit;

[0029] Explanation of reference numerals: constructed wetland unit 1; water inlet pipe 1-1; water distribution area 1-2; main filler area 1-3; wetland plants 1-4; water outlet area 1-5; inlet end boundary of the constructed wetland unit 1-6; first side boundary of the constructed wetland unit 1-7; second side boundary of the constructed wetland unit 1-8; bottom boundary of the constructed wetland unit 1-9; inclination angle of the bottom boundary of the constructed wetland 1-10; drainage pipe 1-11; sump 1-12; overflow hole 1-13; anti-backflow boundary 2; wedge-shaped grid 2-1; open end of the wedge-shaped grid 2-2; closed end of the wedge-shaped grid 2-3; wedge angle of the wedge-shaped grid 2-4; longitudinal boundary 2-5; horizontal boundary 2-6; end boundary 2-7; soil unit 3. Detailed implementation manners

[0030] The present invention provides a unidirectional seepage constructed wetland system with an anti-backflow boundary, including a constructed wetland unit 1 and a soil unit 3 coupled to the constructed wetland unit 1 through an anti-backflow boundary unit 2;

[0031] The anti-backflow boundary unit 2 is a mesh structure, including a wedge-shaped grid 2-1 and a boundary surrounding the wedge-shaped grid 2-1; the wedge-shaped grid 2-1 is filled with a high-permeability material; the material of the boundary is a low-permeability material;

[0032] The outlet end boundary of the constructed wetland unit 1 is the open end of the wedge-shaped grid;

[0033] The bottom boundary of the inlet end of the constructed wetland unit 1 is higher than the bottom boundary of the outlet end of the constructed wetland unit 1.

[0034] As an implementation manner of the present invention, the unidirectional seepage constructed wetland system includes a constructed wetland unit 1; the bottom boundary of the inlet end of the constructed wetland unit 1 is higher than the bottom boundary of the outlet end of the constructed wetland unit 1. As an implementation manner of the present invention, the angle 1-10 between the bottom boundary of the constructed wetland unit 1 and the horizontal plane can be 1-3°, specifically 2°.

[0035] As an implementation manner of the present invention, the constructed wetland unit 1 includes a water distribution area 1-2; the water distribution area 1-2 is provided with a water inlet pipe 1-1.

[0036] As an implementation mode of the present invention, the constructed wetland 1 includes a main filler area 1-3 connected to the water distribution area 1-2; the filling height range of the main filler area 1-3 can be 0.8-1.5 m, specifically 1-1.2 m. In the embodiment of the present invention, the filling height transitions from 1.0 m (next to the water distribution area) to 1.1 m (next to the anti-backflow boundary). From bottom to top, the fillers filled in the main filler area can be quartz sand, activated carbon, and gravel in sequence; the permeability coefficient of the fillers can independently be 50.0-100.0 m / d, specifically 60.0-90.0 m / d. Wetland plants 1-4 are planted in the main filler area 1-3; the wetland plants 1-4 can include one or several of reed, cattail, and canna indica.

[0037] As an implementation mode of the present invention, the constructed wetland unit 1 includes an effluent area 1-5 connected to the main filler area 1-3.

[0038] As an implementation mode of the present invention, the effluent end boundary of the constructed wetland unit 1 is the open end of the wedge-shaped grid 2-1, and the remaining boundaries (the inlet end boundary 1-6 of the constructed wetland, the first side boundary 1-7 of the constructed wetland, the second side boundary 1-8 of the constructed wetland, and the bottom boundary 1-9 of the constructed wetland) are anti-seepage boundaries; the material of the anti-seepage boundary is concrete; in the embodiment of the present invention, the anti-seepage boundary is specifically illustrated by taking a concrete wall as an example.

[0039] As an implementation mode of the present invention, the anti-backflow boundary unit 2 is a unidirectional permeable boundary; the width of the anti-backflow boundary unit 2 can be 20-50 cm, specifically 20 cm, 30 cm, 40 cm, or 50 cm.

[0040] As an implementation mode of the present invention, the anti-backflow boundary unit 2 is a mesh structure, including a wedge-shaped grid 2-1; the wedge angle 2-4 of the wedge-shaped grid 2-1 can be 15-30°, specifically 15°, 20°, 25°, or 30°. The wedge length of the wedge-shaped grid 2-1 is the width of the anti-backflow boundary unit 2; the horizontal width of the open end 2-2 of the wedge-shaped grid 2-1 can be 10.3-31.8 cm, specifically 18.2 cm; the horizontal width of the closed end 2-3 of the wedge-shaped grid 2-1 can be 2-5 cm, specifically 2 cm, 3 cm, 4 cm, or 5 cm; the vertical heights of the open end 2-2 and the closed end 2-3 of the wedge-shaped grid 2-1 are equal and can be 10-30 cm, specifically 15 cm. As an implementation mode of the present invention, the wedge-shaped grid 2-1 is filled with a high-permeability material; the permeability coefficient of the high-permeability material can be 10-20 m / d, specifically 15 m / d, and the high-permeability material can include one or several of biochar, zeolite, slag, oyster shell, volcanic rock, or quartz sand.

[0041] As an embodiment of the present invention, the anti-backflow boundary unit 2 includes a boundary enclosing the wedge-shaped grid 2-1, and the boundary includes a horizontal boundary 2-6 and a longitudinal boundary 2-5; the vertical height of the horizontal boundary 2-6 can be 5-10 cm, specifically 5 cm, 6 cm, 7 cm, 8 cm, 9 cm or 10 cm; the shape of the longitudinal boundary 2-5 can be an isosceles triangular prism; the bottom vertex angle of the isosceles triangular prism can be 15-30°, specifically 15°, 20°, 25° or 30°, which is equal to the wedge angle 2-4 of the wedge-shaped grid 2-1; the height of the bottom surface of the isosceles triangular prism is the width of the anti-backflow boundary unit 2; the height of the longitudinal boundary 2-5 (isosceles triangular prism) is equal to the vertical height of the open end 2-2 of the wedge-shaped grid 2-1. As an embodiment of the present invention, in order to ensure the regularity of the entire system, the end boundaries 2-7 (bottom boundary and top boundary) of the anti-backflow boundary unit 2 can adaptively adjust the shape of the boundary; the material of the boundary is a low-permeability material, and the permeability coefficient of the low-permeability material can be 0.1-1.0 m / d, specifically 0.4 m / d; the low-permeability material can include a mixture of river sand and clay or a mixture of slag and clay.

[0042] As an embodiment of the present invention, a drainage pipe 1-11 is laid at the bottom of the anti-backflow boundary unit 2.

[0043] As an embodiment of the present invention, the one-way seepage constructed wetland system includes a soil unit 3 coupled through the anti-backflow boundary unit 2 and the constructed wetland unit 1. The soil unit 3 is provided with a sump 1-12 connected to the drainage pipe 1-11, and the sump 1-12 is provided with an overflow hole 1-13. As an embodiment of the present invention, the permeability coefficient of the soil unit 3 can be 1 m / d.

[0044] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all embodiments. Other embodiments can be obtained according to these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

[0045] Example 1

[0046] For small rural settlements of 2-3 households, the COD in domestic sewage is about 100 mg / L, ammonia nitrogen is about 30 mg / L, and total phosphorus is about 4 mg / L; the designed treatment water volume is 1.8 m 3 / d. Specifically, the one-way seepage constructed wetland system with an anti-backflow boundary includes a constructed wetland unit 1, a soil unit 3 coupled to the constructed wetland unit 1 through an anti-backflow boundary unit 2. The hydraulic retention time of the sewage in the constructed wetland unit 1 is 1.0 d, and the hydraulic load is 0.4 m 3 / (m 2 ·d).

[0047] As Figures 1-4 shown, the constructed wetland unit 1 is a horizontal subsurface flow constructed wetland with a length of 3 m and a width of 1.5 m. It is provided with a water distribution area 1-2, and an inlet pipe 1-1 is arranged at the water inlet end of the water distribution area 1-2; connected to the water distribution area 1-2 is the main filler area 1-3. The main filler area 1-3 is filled with quartz sand, activated carbon, and gravel from top to bottom, and the permeability coefficients are 60 m / d, 70 m / d, and 90 m / d respectively. The filler depth is 1.0 - 1.1 m from the water distribution area 1-2 to the anti-backflow boundary unit 2 (the bottom surface of the constructed wetland is inclined, so the filler depth beside the water distribution area is 1 m, and the filler depth beside the anti-backflow boundary is 1.1 m, so the filler depth transitions from 1.0 m to 1.1 m). Wetland plants (Phragmites australis, Typha orientalis, Canna indica) 1-4 are planted above the main filler area 1-3; an outlet area 1-5 connected to the main filler area 1-3; the included angle 1-10 between the bottom boundary 1-9 of the constructed wetland unit 1 and the horizontal plane is 2°; the inlet end boundary 1-6, the first side boundary 1-7, the second side boundary 1-8, and the bottom boundary 1-9 of the constructed wetland unit 1 are made of concrete walls for anti-seepage, with a permeability coefficient of 0, and the outlet end boundary is the anti-backflow boundary unit 2.

[0048] The anti-backflow boundary unit 2 is a one-way seepage anti-backflow structure, which is an extension of the constructed wetland unit 1, and its width is 50 cm. The anti-backflow boundary unit 2 includes a wedge-shaped grid 2-1 and the boundary enclosing the wedge-shaped grid 2-1. The wedge angle 2-4 of its wedge-shaped grid 2-1 is 15°, the wedge length is the width of the anti-backflow boundary, the vertical height of the open end 2-2 of the wedge-shaped grid is 15 cm, the horizontal width is 18.2 cm, the vertical height of the closed end 2-3 of the wedge-shaped grid is also 15 cm, and the horizontal width is 5 cm. The wedge-shaped grid is filled with zeolite, and the permeability coefficient is 15 m / d; the longitudinal boundary 2-5 of the anti-backflow boundary unit 2 is made of a mixture of river sand and clay, with a permeability coefficient of 0.4 m / d. The longitudinal boundary is an isosceles triangular prism, the bottom surface apex angle is 15°, and the bottom surface height is the width of the anti-backflow boundary; the vertical height of the longitudinal boundary 2-5 is equal to the vertical height of the closed end 2-3 of the wedge-shaped grid. To ensure the regularity of the whole system, the top boundary and the bottom boundary of the boundary adaptively adjust the shape of the boundary, that is, 2-7; the horizontal boundary 2-6 of the anti-backflow boundary unit 2 has a permeability coefficient of 0.4 m / d, a vertical height of 5 cm, and is made of a mixture of river sand and clay. A drainage pipe 1-11 is laid at the bottom of the boundary of the anti-backflow boundary unit 2.

[0049] The unidirectional seepage constructed wetland system further includes a soil unit 3 coupled to the constructed wetland unit 1 through an anti-backflow boundary unit 2, with a permeability coefficient of 1 m / d. A sump 1-12 connected to the drainage pipe 1-11 is provided in the soil unit 3, and an overflow hole 1-13 is provided in the sump 1-12.

[0050] Specifically, sewage enters the constructed wetland water distribution area 1-2 from the water inlet pipe 1-1, and then the effluent purified by passing through the main filler area 1-3 of the constructed wetland and the constructed wetland plants 1-4 planted thereon passes through the constructed wetland effluent area 1-5. A part of the effluent enters each grid 2-1 filled with a highly permeable material through the open end 2-2 of the wedge-shaped grid of the anti-backflow boundary unit 2, and the highly permeable material is used to further strengthen the treatment of the incoming constructed wetland effluent; then it flows out from the wedge-shaped grid 2-1 through the closed end 2-3 and enters the soil unit 3. Based on the denitrification ability of the soil 3, the denitrification effect is further strengthened; finally, the effluent (COD is about 20 mg / L, ammonia nitrogen is about 5 mg / L, and total phosphorus is about 1 mg / L) further purified by the soil system 3 is discharged into the natural system to realize the integration of the constructed wetland and the natural system. The effluent that cannot enter the soil system 3 through the anti-backflow boundary 2 enters the sump 1-12 through the drainage pipe 1-11, and then is discharged through the overflow hole 1-13 on the sump 1-12.

[0051] Therefore, for the unidirectional seepage constructed wetland system with such an anti-backflow boundary structure, by changing the impermeable boundary of the conventional constructed wetland into an anti-backflow unidirectional permeable boundary, the effluent of the constructed wetland flows unidirectionally into the soil through the anti-backflow boundary, maintaining the hydraulic connection between the constructed wetland and the soil to utilize the purification potential of the soil, and avoiding the system stability risk caused by the reverse fluctuation of the external water level, realizing the integration of the constructed wetland ecological restoration system and the natural system and the synchronous enhanced reduction of pollutants.

[0052] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments can also be obtained according to this embodiment without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A one-way seepage constructed wetland system with an anti-backflow boundary, characterized in that, It includes a constructed wetland unit (1) and a soil unit (3) coupled to the constructed wetland unit (1) through a backflow prevention boundary unit (2). The backflow prevention boundary unit (2) is a mesh structure, including wedge-shaped grids (2-1) and a boundary enclosing the wedge-shaped grids (2-1); the wedge-shaped grids (2-1) are filled with highly permeable materials. The material of the boundary is a low-permeability material. The outlet end boundary of the constructed wetland unit (1) is the open end of the wedge-shaped grid. The bottom boundary of the inlet end of the constructed wetland unit (1) is higher than the bottom boundary of the outlet end of the constructed wetland unit (1).

2. The unidirectional seepage constructed wetland system according to claim 1, wherein A drainage pipe (1-11) is also laid at the bottom of the backflow prevention boundary unit (2).

3. The unidirectional seepage constructed wetland system according to claim 1, characterized in that, The width of the backflow prevention boundary unit (2) is 20-50 cm.

4. The unidirectional seepage constructed wetland system according to claim 1, characterized in that The wedge angle (2-4) of the wedge-shaped grid (2-1) is 15-30°, and the wedge length is the width of the backflow prevention boundary unit (2); the vertical heights of the open end (2-2) and the closed end (2-3) of the wedge-shaped grid (2-1) are equal, being 10-30 cm; the horizontal width of the open end (2-2) of the wedge-shaped grid (2-1) is 10.3-31.8 cm; the horizontal width of the closed end (2-3) of the wedge-shaped grid (2-1) is 2-5 cm.

5. The unidirectional seepage system according to claim 1, characterized in that, The boundary includes a horizontal boundary (2-6) and a longitudinal boundary (2-5); the vertical height of the horizontal boundary (2-6) is 5-10 cm; the shape of the longitudinal boundary (2-5) is an isosceles triangular prism; the bottom vertex angle of the isosceles triangular prism is 15-30°, which is equal to the wedge angle (2-4) of the wedge-shaped grid (2-1).

6. The unidirectional seepage constructed wetland system according to claim 1, wherein The permeability coefficient of the low-permeability material is 0.1-1.0 m / d; the permeability coefficient of the highly permeable material is 10-20 m / d.

7. The unidirectional seepage constructed wetland system according to claim 1, wherein The constructed wetland unit (1) includes a water distribution area (1-2); a water inlet pipe (1-1) is provided in the water distribution area (1-2). A main filler area (1-3) connected to the water distribution area (1-2); wetland plants (1-4) are planted in the main filler area (1-3). An outlet area (1-5) connected to the main filler area (1-3).

8. The unidirectional seepage constructed wetland system according to claim 7, wherein The filling height range of the main filler area (1-3) is 0.8-1.5 m, and the permeability coefficient is 50.0-100.0 m / d.

9. The one-way seepage constructed wetland system according to claim 1, characterized in that, The included angle (1-10) between the bottom boundary of the constructed wetland unit (1) and the horizontal plane is 1-3°.

10. The unidirectional seepage constructed wetland system according to claim 1, characterized in that, The soil unit (3) is provided with a sump (1-12) connected to a drain pipe; the sump (1-12) is provided with an overflow hole (1-13).

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