Turn-back type subsurface wetland

Abstract

The utility model provides a turn-back type subsurface flow wetland. The turn-back type subsurface flow wetland comprises a water distribution channel, a wetland reaction bed and a water outlet channel which are sequentially communicated along the water flow direction, the wetland reaction bed comprises a wetland wall body, a plurality of first flow guide walls and a plurality of second flow guide walls are arranged in the wetland wall body, the first flow guide walls and the second flow guide walls extend in the direction perpendicular to the water flow direction, and the first flow guide walls and the second flow guide walls are alternately arranged at intervals in the water flow direction; the wetland reaction bed is divided into a plurality of purification chambers which are communicated in sequence; the first flow guide wall is provided with a first baffling opening communicated with the two adjacent purification cavities, the second flow guide wall is provided with a second baffling opening communicated with the two adjacent purification cavities, and the elevation of the bottom surface of the first baffling opening is higher than that of the top surface of the second baffling opening; a filler layer is arranged in the purification chamber, and a plant layer is arranged at the top of the filler layer. The sewage treatment device has the advantages of high hydraulic load, good treatment effect and difficulty in blockage.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of artificial wetland, and relates to a turn-back type subsurface flow wetland. BACKGROUND

[0002] At present, along with the improvement of resident living standard, the quality requirement of resident to river and lake basin water ecological environment is also increasingly promoted. Artificial wetland technology has the advantages of investment saving, operation and maintenance simplicity and natural ecology, and has broad application prospect, especially the subsurface flow artificial wetland technology is widely applied in water bypass treatment and tail water treatment of sewage treatment plant.

[0003] CN204848448U discloses a vertical flow artificial wetland sewage treatment device suitable for cold regions, which comprises a sewage pool, an artificial wetland pool and a liquid level control pool, a water pump and an electromagnetic valve connected by a pipeline are arranged in the sewage pool, a working layer is arranged in the artificial wetland pool, a water distribution pipe layer connected with the water pump through a water pipe is arranged at the top of the working layer, a heat preservation layer is arranged at the top of the water distribution pipe layer, a drainage layer is arranged at the bottom of the working layer, and a water collecting pipe layer is arranged at the bottom end of the drainage layer; a seepage-proof membrane is arranged at the bottom end of the artificial wetland pool, and a liquid level control pool is arranged on one side of the artificial wetland pool.

[0004] CN212024915U discloses a composite artificial wetland treatment system for industrial sewage, which comprises a vertical flow artificial wetland, a water storage pool, a drop pool and a horizontal subsurface flow artificial wetland, the vertical flow artificial wetland, the water storage pool, the drop pool and the horizontal subsurface flow artificial wetland are sequentially arranged in flow communication, and a vertical flow + horizontal subsurface flow composite artificial wetland process is adopted to deeply purify tail water of a sewage treatment plant.

[0005] As described above, the conventional subsurface flow wetland is mainly divided into horizontal flow and vertical flow types according to the structure type, but in practice, the subsurface flow wetland also encounters many engineering challenges, the water distribution of the horizontal flow subsurface flow wetland is uneven, and the treatment load is low; although the water distribution of the vertical flow subsurface flow wetland is uniform, it is easy to be blocked. During the long-term operation of the wetland, problems such as blockage, reduced operation efficiency and difficult cleaning are encountered, which limits the application and development of the subsurface flow wetland.

[0006] Therefore, it is necessary to provide a novel subsurface flow wetland to solve the problems existing in the prior art. UTILITY MODEL CONTENT

[0007] In view of the deficiencies in the prior art, the utility model aims to provide a turn-back type subsurface flow wetland with the advantages of high hydraulic load, good treatment effect and difficulty in blocking.

[0008] To achieve this purpose, the utility model adopts the following technical solutions:

[0009] The utility model provides a kind of turn-back type subsurface flow wetland, the turn-back type subsurface flow wetland includes water distribution ditch, wetland reaction bed and outlet channel sequentially communicated along water flow direction;The wetland reaction bed includes wetland wall body, the inside of wetland wall body is provided with a plurality of first flow guide wall and a plurality of second flow guide wall, the first flow guide wall and the second flow guide wall extend along perpendicular to water flow direction, and the plurality of first flow guide wall and the plurality of second flow guide wall are alternately spaced along water flow direction, the wetland reaction bed is separated into a plurality of purification chambers sequentially communicated;First baffle opening for connecting adjacent two purification chambers is provided on the first flow guide wall, second baffle opening for connecting adjacent two purification chambers is provided on the second flow guide wall, and the bottom surface elevation of the first baffle opening is higher than the top surface elevation of the second baffle opening;Filler layer is provided in the purification chamber, and plant layer is provided on the top of filler layer.

[0010] The utility model discloses water flow in wetland reaction bed from water distribution ditch is under the flow guiding effect of alternately arranged first flow guide wall and second flow guide wall, and the route of up-down turn-back type flows through wetland reaction bed, and then flows into outlet channel, solve the problem that water flow is easy to jam, prolong the flow path of water flow in reaction bed, make water flow and filler contact fully, improve processing effect.

[0011] The utility model discloses turn-back type subsurface flow wetland's application range is wide, can be applied to the purification treatment of various sewage, including but not limited to domestic sewage, slightly polluted sewage, tail water of sewage treatment plant and the like.

[0012] It should be noted that the bottom surface elevation of the first baffle opening in the utility model refers to the maximum straight-line distance from the bottom of the first baffle opening to the surface of the bottom of the wetland wall body, and the top surface elevation of the second baffle opening refers to the maximum straight-line distance from the top of the second baffle opening to the surface of the bottom of the wetland wall body.

[0013] As a preferred technical solution of the utility model, the first flow guide wall is inserted into the wetland reaction bed from the bottom of the wetland wall body, and a gap is left between the top surface of the filler layer to form the first baffle opening; the second flow guide wall is inserted into the wetland reaction bed from above the wetland wall body, and a gap is left between the bottom surface of the filler layer to form the second baffle opening; the maximum linear length of the first baffle opening in the direction perpendicular to the water flow is less than the maximum linear length of the second baffle opening in the direction perpendicular to the water flow.

[0014] As a preferred technical solution of the utility model, the maximum linear length of the first baffle opening in the direction perpendicular to the water flow is 20-40 cm, for example, it can be 20 cm, 22 cm, 25 cm, 28 cm, 30 cm, 32 cm, 35 cm, 38 cm or 40 cm, but it is not limited to the listed values, and other unlisted values within this range are also applicable.

[0015] The maximum linear length of the second baffle in the direction perpendicular to the water flow direction is 30-50 cm, for example, it can be 30 cm, 32 cm, 35 cm, 38 cm, 40 cm, 42 cm, 45 cm, 48 cm or 50 cm, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0016] As a preferred technical scheme of the present application, the bottom of the wetland wall is further provided with an anti-seepage layer, and the filler layer is detachably connected to the anti-seepage layer.

[0017] As a preferred technical scheme of the present application, the anti-seepage layer comprises a native soil structure layer, a fine sand protection layer, an anti-seepage membrane layer and a clay structure layer arranged in sequence, and the clay structure layer is arranged close to the filler layer.

[0018] As a preferred technical scheme of the present application, the slope of the native soil structure layer is 3‰-5‰, for example, it can be 3‰, 3.2‰, 3.4‰, 3.5‰, 3.6‰, 3.8‰, 4‰, 4.2‰, 4.4‰, 4.5‰, 4.6‰, 4.8‰ or 5‰, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0019] As a preferred technical scheme of the present application, the thickness of the fine sand protection layer is 10-20 cm, for example, it can be 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, 15 cm, 16 cm, 17 cm, 18 cm, 19 cm or 20 cm, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0020] The thickness of the clay structure layer is 10-30 cm, for example, it can be 10 cm, 12 cm, 14 cm, 15 cm, 16 cm, 18 cm, 20 cm, 24 cm, 25 cm, 26 cm, 28 cm or 30 cm, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0021] As a preferred technical scheme of the present application, the first flow guide wall is T-shaped, and the bottom of the first flow guide wall is inserted into the native soil structure layer.

[0022] As a preferred technical scheme of the present application, the inlet end and the outlet end of the wetland reaction bed are respectively provided with a water inlet pipe network and a water outlet pipe network, the water inlet pipe network communicates with the water distribution channel, and the water outlet pipe network communicates with the water outlet channel.

[0023] As an optimal technical scheme of the utility model, a plurality of intermediate partition walls are arranged in the wetland reaction bed, the plurality of intermediate partition walls are arranged in parallel and at intervals along the width direction of the wetland wall body, and the intermediate partition walls are sealingly connected to the wetland wall body.

[0024] Compared with the prior art, the utility model has the beneficial effects that:

[0025] The utility model provides a kind of wetland of folding back type undercurrent in the first flow guide wall and second flow guide wall are arranged alternately, so that water flow is up and down folding back type route and flows through wetland reaction bed, solve the problem that water flow is easily blocked, prolong the flow path of water flow in reaction bed, increase water flow and filler contact time, so that water flow is sufficiently purified. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is the structure schematic diagram of folding back type undercurrent for the utility model embodiment 1.

[0027] Figure 2 It is the top view of wetland reaction bed for the utility model embodiment 1.

[0028] Wherein, 11-water distribution ditch;21-wetland reaction bed;211-wetland wall body;212-intermediate partition wall;213-first flow guide wall;214-second flow guide wall;215-second baffle;216-first baffle;221-inlet pipe network;222-outlet pipe network;23-filler layer;24-anti-seepage layer;241-clay structure layer;242-anti-seepage membrane layer;243-fine sand protection layer;244-soil structure layer;25-plant layer;31-outlet channel. DETAILED DESCRIPTION

[0029] It needs to be understood that, in the description of the utility model, the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the utility model and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the utility model.In addition, the terms "first", "second" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features.Therefore, the features limited by "first", "second" and the like can be explicitly or implicitly included one or more features.In the description of the utility model, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0030] It should be noted that in the description of the utility model, unless there are clear provisions and limitations, the terms "arrangement", "connection", "connection" should be broadly understood, for example, it can be fixed connection, or it can be detachable connection, or integral connection, it can be mechanical connection, or electrical connection, it can be directly connected, or indirectly connected through intermediate media, it can be the communication inside two elements. For ordinary skilled persons in the art, the specific meaning of the above terms in the utility model can be understood through specific circumstances.

[0031] The technical scheme of the utility model is further illustrated below by specific embodiments in combination with the drawings.

[0032] The utility model provides a kind of folding return type subsurface wetland, including water distribution canal, wetland reaction bed and outlet channel sequentially communicated along water flow direction.The water distribution canal is used to evenly distribute water to wetland reaction bed, the wetland reaction bed is used to purify water flow, and clean water after purification is discharged to outlet channel for subsequent disposal.The wetland reaction bed includes wetland wall body, the inside of wetland wall body is provided with a plurality of first flow guide walls and a plurality of second flow guide walls, the first flow guide wall and the second flow guide wall extend along the direction perpendicular to water flow, and the plurality of first flow guide walls and the plurality of second flow guide walls are alternately and spaced apart along the direction of water flow, and the wetland reaction bed is divided into a plurality of purification chambers sequentially communicated;First baffle opening for communicating adjacent two purification chambers is provided on the first flow guide wall, second baffle opening for communicating adjacent two purification chambers is provided on the second flow guide wall, and the bottom surface elevation of the first baffle opening is higher than the top surface elevation of the second baffle opening, so that water flow in previous purification chamber flows upwards, enters current purification chamber through first baffle opening, and then flows downwards, enters next purification chamber through second baffle opening, to present up-down baffle type curve flow path.The purification chamber is provided with filler layer, and water flow purification is realized based on biological, physical or chemical effects such as adsorption, absorption or oxidation.The top of the filler layer is provided with plant layer, realizes the full contact of pollutants and microorganisms, plant root system, and completes water quality purification under the action of microbial purification and plant root absorption.

[0033] The wetland wall body, first flow guide wall and second flow guide wall are formed by pouring and installing materials such as concrete, reinforcing steel and support, which have the characteristics of sealing, waterproofing, anti-drying cracking and strong structural stability.

[0034] The filler layer includes but is not limited to gravel, red brick pieces, steel slag, ceramsite, limestone, activated carbon, bamboo charcoal and zeolite commonly used in the art, and the type of filler can be adjusted by skilled persons according to actual water treatment conditions, which is not limited in the utility model.

[0035] The plant layer is planted with emergent plants, including but not limited to any one or a combination of at least two of reed, cattail, acorus, iris, lythrum, pickerelweed or canna, and a person skilled in the art can adjust the plant species according to an actual water treatment working condition, and the utility model does not make a specific limitation in this regard.

[0036] Specifically, the first flow guide wall is inserted into the wetland reaction bed from the bottom of the wetland wall body and leaves a gap with the top surface of the filler layer to form the first baffle opening; and the second flow guide wall is inserted into the wetland reaction bed from above the wetland wall body and leaves a gap with the bottom surface of the filler layer to form the second baffle opening, that is, the water flow in the previous purification chamber flows upwards into the current purification chamber from the top of the first flow guide wall, and the water flow in the current purification chamber flows downwards through the bottom of the second flow guide wall into the next purification chamber, so as to present an up-down baffle type curved flow path.

[0037] Specifically, the maximum linear length of the first baffle opening in the direction perpendicular to the water flow is 20-40 cm, and the maximum linear length of the second baffle opening in the direction perpendicular to the water flow is 30-50 cm, which can effectively avoid the problems of short flow or dead zone of the outlet water.

[0038] In some embodiments, the bottom of the wetland wall body is further provided with an anti-seepage layer, and the filler layer is detachably connected to the anti-seepage layer. Specifically, the anti-seepage layer comprises a native soil structure layer, a fine sand protection layer, an anti-seepage membrane layer and a clay structure layer which are sequentially stacked, and the clay structure layer is arranged close to the filler layer. The utility model firstly compacts the native soil at the bottom of the wetland wall body to form a base layer, and leaves a slope of 3‰-5‰ for draining accumulated water in the rainy season; a 10-20 cm fine sand protection layer is laid on the compacted native soil structure layer, and fine sand with a particle size of 2-10 mm is selected to play a protection and transition role; an anti-seepage membrane layer is laid on the fine sand protection layer, and geotextile and / or waterproof membrane commonly used by those skilled in the art can be used, which has good waterproof, anti-seepage and air permeability; and finally, a clay structure layer with a thickness of 10-30 cm is laid on the anti-seepage membrane layer to improve the anti-seepage effect.

[0039] Further, the first flow guide wall is T-shaped, and the bottom of the first flow guide wall is inserted into the native soil structure layer to be sealed with the bottom of the wetland reaction bed, further avoiding leakage.

[0040] In some embodiments, a plurality of intermediate partition walls are arranged in the wetland reaction bed, the intermediate partition walls are arranged in parallel along the width direction of the wetland wall, and the intermediate partition walls are sealingly connected to the wetland wall to divide the wetland reaction bed into a plurality of modules, which is beneficial to uniform water distribution and alleviates the problem of clogging or flow dead zone of the reaction bed.

[0041] In some embodiments, the inlet end and the outlet end of the wetland reaction bed are respectively provided with an inlet pipe network and an outlet pipe network, the inlet pipe network is communicated with the water distribution channel, and the outlet pipe network is communicated with the outlet channel. The inlet pipe network and the outlet pipe network in the utility model must include necessary pipelines, conventional valves and general pump equipment for realizing the process integrity, but the above content does not belong to the main utility model point of the utility model, and a person skilled in the art can add layout by himself based on the process flow and equipment structure selection, and the utility model does not specially require and specifically limit this.

[0042] Embodiment 1

[0043] The embodiment provides a meander type subsurface flow wetland, which comprises a water distribution channel 11, a wetland reaction bed 21 and an outlet channel 31 arranged in sequence along the water flow direction. As shown in the figure, the water distribution channel 11 is connected to the inlet end of the wetland reaction bed 21, and the outlet channel 31 is connected to the outlet end of the wetland reaction bed 21. Figure 1 And Figure 2As shown, the wetland reaction bed 21 comprises a wetland wall 211, and the interior of the wetland wall 211 is provided with a plurality of first flow guide walls 213 and a plurality of second flow guide walls 214. The first flow guide walls 213 and the second flow guide walls 214 extend in a direction perpendicular to the water flow direction, and the plurality of first flow guide walls 213 and the plurality of second flow guide walls 214 are alternately and spacedly arranged along the water flow direction, so as to divide the wetland reaction bed 21 into a plurality of purification chambers which are sequentially communicated. A plurality of intermediate partition walls are further arranged in the wetland reaction bed 21, and are arranged side by side and spacedly along the width direction of the wetland wall 211. The intermediate partition walls are sealingly connected to the wetland wall 211, so as to divide the wetland reaction bed 21 into a plurality of modules, which is beneficial to uniform distribution of the water flow. The purification chamber is provided with a filler layer 23, and the interior of the filler layer 23 is filled with porous ceramic particles. The top of the filler layer 23 is provided with a plant layer 25, and the plant layer 25 is selected from strong water purification ability emergent plants such as reed, acorus, and water onion. The first flow guide wall 213 is inserted into the wetland reaction bed 21 from the bottom of the wetland wall 211, and a gap of 20-40 cm is left between the top surface of the filler layer 23 and the first flow guide wall 213 to form a first baffle opening 216, which is used for communication between adjacent two purification chambers. The second flow guide wall 214 is inserted into the wetland reaction bed 21 from the top of the wetland wall 211, and a gap of 30-50 cm is left between the bottom surface of the filler layer 23 and the second flow guide wall 214 to form a second baffle opening 215, so that the water flow is in an up-down baffle flow path. The bottom of the wetland wall 211 is further provided with an anti-seepage layer 24, and the filler layer 23 is detachably connected to the anti-seepage layer 24. The anti-seepage layer 24 comprises a native soil structure layer 244, a fine sand protection layer 243, an anti-seepage membrane layer 242, and a clay structure layer 241 which are sequentially stacked, and the clay structure layer 241 is arranged close to the filler layer 23. The slope of the native soil structure layer 244 is 3‰-5‰, the thickness of the fine sand protection layer 243 is 20 cm, the anti-seepage membrane layer 242 is made of geotextile and high-density polyethylene film, and the thickness of the clay structure layer 241 is 20 cm. The first flow guide wall 213 is in a T shape, and the bottom of the first flow guide wall 213 is inserted into the native soil structure layer 244, so as to improve the stability and sealing performance. The inlet end of the wetland reaction bed 21 is connected to the water distribution channel 11 through a water inlet pipe network 221, and the water inlet pipe network 221 is composed of a plurality of water inlet pipes. The surface of the water inlet pipe is provided with water distribution holes and air exhaust holes. The outlet end of the wetland reaction bed 21 is connected to the water outlet channel 31 through a water outlet pipe network 222, and the water outlet pipe network 222 is composed of a plurality of water collection pipes. The surface of the water collection pipe is provided with water distribution holes and air exhaust holes. The top of the water distribution channel 11 and the water outlet channel 31 is provided with an inspection hole, and a grating cover plate is arranged on the inspection hole.

[0044] Example 2

[0045] The difference between the wetland reaction bed of the present embodiment and the wetland reaction bed of the example 1 is that the plant layer of the wetland reaction bed is selected from emergent plants with ornamental properties such as iris and reed primrose in addition to reed, acorus, and other emergent plants with strong water purification ability. The rest of the structure is the same as that of the example 1.

[0046] Comparative Example 1

[0047] The comparative example provides a subsurface flow wetland, which is different from the example 1 in that the first flow guide wall and the second flow guide wall are not arranged in the wetland reaction bed, and the rest of the structure is completely same as the example 1.

[0048] Application example 1

[0049] The application example adopts the subsurface flow wetland provided by the example 1 to test the micro-polluted river water, and the water quality of the inlet and outlet is shown in Table 1. Among them, the inlet is sampled by the water distribution channel, and the outlet is sampled by the outlet channel.

[0050] Table 1

[0051] Sample CODcr(mg / L) [NH3-N (mg / L)] TP(mg / L) Influent 35～70 0.80～2.60 0.15～0.60 Effluent 15～35 0.20～0.50 0.08～0.30

[0052] As can be seen from Table 1, the subsurface flow wetland of the utility model is used to purify the micro-polluted river water through the up-down turn-back flow direction, and has good water quality of the outlet.

[0053] Application example 2

[0054] The application example adopts the subsurface flow wetland provided by the example 2 to test the tail water of the urban sewage treatment plant, and the water quality of the inlet and outlet is shown in Table 2. Among them, the inlet is sampled by the water distribution channel, and the outlet is sampled by the outlet channel.

[0055] Table 2

[0056] Sample CODcr(mg / L) [NH3-N (mg / L)] TP(mg / L) Influent 25～40 0.60～1.80 0.20～0.35 Effluent 15～35 0.20～0.80 0.08～0.21

[0057] As can be seen from Table 2, the subsurface flow wetland of the utility model is used to purify the tail water of the sewage treatment plant through the up-down turn-back flow direction, and has good water quality of the outlet.

[0058] Comparative application example 1

[0059] The comparative application example adopts the subsurface flow wetland provided by the comparative example 1 to test the micro-polluted river water, and the water quality of the inlet and outlet is shown in Table 3. Among them, the inlet is sampled by the water distribution channel, and the outlet is sampled by the outlet channel.

[0060] Table 3

[0061] Sample CODcr(mg / L) [NH3-N (mg / L)] TP(mg / L) Influent 35～70 0.80～2.60 0.15～0.60 Effluent 15～40 0.30～0.70 0.08～0.40

[0062] As can be seen from Table 3, the outlet effect of the comparative application example 1 is lower than that of the application example 1, which is mainly due to the fact that the sewage in the example 1 flows through the wetland reaction bed in the up-down turn-back mode, prolongs the residence time, so that the sewage can be fully contacted and purified with the porous ceramic, and the purification effect is effectively improved.

[0063] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by any person skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

Claims

1. A folded return subsurface flow wetland characterized in that, The return type subsurface flow wetland comprises a water distribution channel, a wetland reaction bed and a water outlet channel which are sequentially connected along the water flow direction; the wetland reaction bed comprises a wetland wall body, a plurality of first flow guide walls and a plurality of second flow guide walls are arranged in the wetland wall body, the first flow guide walls and the second flow guide walls extend along the direction perpendicular to the water flow direction, and the plurality of first flow guide walls and the plurality of second flow guide walls are alternately and spacedly arranged along the water flow direction, so as to divide the wetland reaction bed into a plurality of purification chambers which are sequentially connected; a first baffle opening for connecting two adjacent purification chambers is arranged on the first flow guide wall, a second baffle opening for connecting two adjacent purification chambers is arranged on the second flow guide wall, and the bottom surface elevation of the first baffle opening is higher than the top surface elevation of the second baffle opening; a filler layer is arranged in the purification chamber, and a plant layer is arranged on the top of the filler layer.

2. The raceway type subsurface flow wetland according to claim 1, characterized in that, The first flow guide wall is inserted into the wetland reaction bed from the bottom of the wetland wall body, and a gap is left between the top surface of the filler layer and the first flow guide wall to form the first baffle opening; The second flow guide wall is inserted into the wetland reaction bed from above the wetland wall body, and a gap is left between the bottom surface of the filler layer and the second flow guide wall to form the second baffle opening; The maximum linear length of the first baffle opening in the direction perpendicular to the water flow direction is less than the maximum linear length of the second baffle opening in the direction perpendicular to the water flow direction.

3. The raceway type subsurface flow wetland according to claim 2, characterized in that, The maximum linear length of the first baffle opening in the direction perpendicular to the water flow direction is 20-40 cm; The maximum linear length of the second baffle opening in the direction perpendicular to the water flow direction is 30-50 cm.

4. The raceway type subsurface flow wetland according to claim 2, characterized in that, The bottom of the wetland wall body is further provided with an anti-seepage layer, and the filler layer is detachably connected to the anti-seepage layer.

5. The raceway constructed wetland of claim 4, wherein, The anti-seepage layer comprises a native soil structure layer, a fine sand protection layer, an anti-seepage membrane layer and a clay structure layer which are sequentially stacked, and the clay structure layer is arranged close to the filler layer.

6. The raceway constructed wetland of claim 5, wherein, The slope of the native soil structure layer is 3-5 ‰.

7. The folded return flow constructed wetland according to claim 5 or 6, characterized in that The thickness of the fine sand protection layer is 10-20 cm; The thickness of the clay structure layer is 10-30 cm.

8. The raceway type subsurface flow wetland according to claim 5, characterized in that, The first flow guide wall is T-shaped, and the bottom of the first flow guide wall is inserted into the native soil structure layer.

9. The raceway constructed wetland of claim 1, wherein, The inlet end and the outlet end of the wetland reaction bed are respectively provided with a water inlet pipe network and a water outlet pipe network, the water inlet pipe network is connected to the water distribution channel, and the water outlet pipe network is connected to the water outlet channel.

10. The raceway constructed wetland of claim 1, wherein, A plurality of intermediate partition walls are further arranged in the wetland reaction bed, the plurality of intermediate partition walls are arranged side by side and spacedly along the width direction of the wetland wall body, and the intermediate partition walls are sealingly connected to the wetland wall body.

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