Composite artificial wetland system

Abstract

The invention discloses a composite artificial wetland system, and relates to the technical field of artificial wetlands. The composite artificial wetland system comprises an ecological pool, and a surface flow wetland unit, a horizontal subsurface flow wetland unit, an internal circulation system unit and plant ecological buffer zone units around the wetland are arranged in the ecological pool; the surface flow wetland unit comprises a wetland water inlet pipe and a wetland water outlet pipe which are arranged on the two sides of the ecological pool respectively, a gravel layer and a medium-coarse sand planting layer are sequentially stacked and laid at the bottom of the ecological pool, and a submerged plant vallisneria natans community is planted on the medium-coarse sand planting layer; the invention solves the problems of single function, low treatment efficiency and the like of the traditional constructed wetland, has the advantages of prominent denitrification effect, good phosphorus removal and suspended matter interception effect, strong impact load resistance, low cost, easiness in maintenance, ecological friendliness, landscape fusion and the like, also has the advantages of initial rainwater interception and the like, and is wider in application range.

Description

Technical Field

[0001] This invention belongs to the field of constructed wetland technology, and more specifically, relates to a composite constructed wetland system. Background Technology

[0002] Constructed wetland technology first appeared in Germany, and my country officially introduced the technology and began related research in 1988. Its principle is to remove pollutants from wastewater through the combined action of plants, microorganisms, and soil or filler materials within the wetland ecosystem.

[0003] Constructed wetland substrate fillers are the core component of the system, and their functions go far beyond simply supporting plants and filtering water flow. They also retain suspended solids, regulate hydraulic properties, adsorb pollutants, regulate pH and redox potential, act as biological carriers, and facilitate synergistic effects with plant roots.

[0004] For small-scale wastewater treatment in locations such as small gathering places, schools, and villages, traditional constructed wetlands suffer from drawbacks such as large land occupation, low resistance to shock loads, and limited purification efficiency. Therefore, this application provides a composite constructed wetland system to meet these needs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a composite artificial wetland system that can overcome or at least partially solve the above problems.

[0006] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0007] A composite constructed wetland system includes an ecological pond, within which are arranged a surface flow wetland unit, a horizontal subsurface flow wetland unit, an internal circulation system unit, and a plant ecological buffer zone unit surrounding the wetland. The surface flow wetland unit includes a wetland inlet pipe and a wetland outlet pipe respectively located on both sides of the ecological pond. The bottom of the ecological pond is successively laid with a gravel layer and a medium-coarse sand planting layer, and a submerged plant community of Vallisneria natans is planted on the medium-coarse sand planting layer. The horizontal subsurface flow wetland unit includes gravel filler laid in the middle of the ecological pond, with gabion cages installed on both sides of the gravel filler. The upper layer of the gravel filler is covered with a permeable geotextile, and a planting soil is laid on top of the permeable geotextile, with aquatic irises planted on the planting soil.

[0008] Preferably, the internal circulation system unit includes a circulating water pump placed in the ecological pond, the output end of the circulating water pump is connected to a circulating water pipe, the output end of the circulating water pipe is provided with a circulating water outlet, and the circulating water pump and the circulating water outlet are respectively located on both sides of the ecological pond.

[0009] Preferably, the plant ecological buffer zone unit around the wetland includes a ring-shaped brick retaining wall surrounding the inside of the ecological pond. A slope is provided between the inner wall of the ecological pond and the brick retaining wall, and planting soil is laid on the slope. The brick retaining wall is placed on top of the gravel layer, and the bottom of the brick retaining wall meets the planting soil. Canna indica, yellow iris and aquatic canna are planted on the planting soil.

[0010] Preferably, the inlet end of the horizontal subsurface flow wetland unit is provided with a strip-shaped sedimentation tank, the upper end of the strip-shaped sedimentation tank is provided with a U-shaped hollow bracket, the gravel layer and the medium-coarse sand planting layer at the top of the strip-shaped sedimentation tank are located inside the U-shaped hollow bracket, and L-shaped hollow plates that are closely attached to the U-shaped hollow bracket are provided on both sides of the upper end of the strip-shaped sedimentation tank.

[0011] Furthermore, a horizontally arranged perforated plate is fixedly installed inside the strip-shaped sedimentation tank, and an adsorption element is installed on the perforated plate. The bottom of the U-shaped perforated bracket is connected to a support leg that presses against the adsorption element.

[0012] Furthermore, the outer wall of the brick retaining wall is provided with equally spaced buffer protrusions, and the cross-sectional shape of the buffer protrusions is semi-circular or triangular.

[0013] Preferably, the wetland inlet pipe and wetland outlet pipe are both made of UPVC, the planting density of the submerged plant Vallisneria natans community is 50 plants / m2, the planting water depth of the submerged plant Vallisneria natans community is 1m, the particle size of the medium-coarse sand planting layer is 0.5mm-2mm, the laying thickness of the medium-coarse sand planting layer is 20cm, the particle size of the gravel layer is 2cm-3cm, and the laying thickness of the gravel layer is 10cm.

[0014] Furthermore, the circulating water outlet mainly consists of a first outlet, a second outlet, and a third outlet arranged at equal intervals, and the input ends of the first outlet, the second outlet, and the third outlet are all connected to the output end of the circulating water pipe, and the diameter of the first outlet, the second outlet, and the third outlet is DN20.

[0015] Preferably, the permeable geotextile is made of short-fiber needle-punched material, and the permeable geotextile has a unit mass area of ​​150 g / m². 2 -200g / m 2 The permeable geotextile has a tensile strength of 20kN / m-30kN / m and a permeability coefficient of 0.05cm / s-0.1cm / s.

[0016] Furthermore, the brick retaining wall is 1.5m high, and the planting density of Thalia dealbata, Iris tectorum, and Canna indica is 25 plants / m². 2 .

[0017] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0018] 1. This invention slows down the water flow through the porous channels formed between gravels, causing suspended solids in the water to settle onto the gravel surface due to gravity. The biofilm attached to the gravel filler surface can adsorb organic matter in the water and decompose it into inorganic matter through the metabolism of microorganisms. These microorganisms mainly use organic matter for growth and reproduction, thereby achieving the degradation of pollutants.

[0019] 2. This invention, through the installation of permeable geotextile, can prevent planting soil from seeping into the gaps of gravel filler. At the same time, sewage permeates through the permeable geotextile to moisten the planting soil, providing the necessary moisture for the growth of aquatic iris plants planted on top of the permeable geotextile. Over time, the well-developed root system of the aquatic iris plants on top of the planting soil will adhere to the permeable geotextile, and the roots and permeable geotextile will form a biofilm, further purifying the water quality. This stacked purification structure can give it good resistance to shock loads while reducing the footprint.

[0020] 3. The present invention achieves the following three effects through the setting of the internal circulation system unit: First, this circulation treatment can effectively increase the residence time of sewage in the system and improve the efficiency of sewage purification; Second, compared with traditional surface flow wetlands, horizontal subsurface flow wetlands, or combined wetlands, it reduces the land area of ​​the wetland system; Third, it increases the ecological base flow, and the flowing water increases dissolved oxygen, reduces pollutants in the water, promotes energy flow and material circulation, so as to maintain the stability of the ecosystem composed of aquatic plants, animals and microorganisms.

[0021] 4. By setting up a plant ecological buffer zone unit around the wetland, the present invention allows the initial rainwater or surface runoff around the wetland to carry a large amount of mud and sand through the filtering and adsorption of the roots of emergent plants such as Thalia dealbata, Iris tectorum, and Canna indica in the plant ecological buffer zone unit and the planting soil, thereby reducing the direct entry of nitrogen, phosphorus and suspended solids from non-point source pollution into the wetland water body and indirectly improving the water quality of the wetland.

[0022] In summary, the composite constructed wetland system proposed in this invention combines surface flow wetlands, horizontal subsurface flow wetlands, "gravel interbed" technology, and plant ecological buffer zone technology to solve the problems of single function and low treatment efficiency of traditional constructed wetlands. This invention has the advantages of outstanding nitrogen removal effect, good phosphorus removal and suspended solids interception effect, strong resistance to shock load, low cost, easy maintenance, ecological friendliness and landscape integration, and also has the advantages of initial rainwater interception, making its application range wider.

[0023] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0024] In the attached diagram:

[0025] Figure 1 This is a schematic diagram of the structure of a composite artificial wetland system proposed in this invention;

[0026] Figure 2 This invention proposes a composite constructed wetland system. Figure 1 Schematic diagram of local structure Figure 1 ;

[0027] Figure 3 This invention proposes a composite constructed wetland system. Figure 1 Schematic diagram of local structure Figure 2 ;

[0028] Figure 4 This is a top view schematic diagram of a composite constructed wetland system proposed in this invention;

[0029] Figure 5 This invention proposes a composite constructed wetland system. Figure 3 Schematic diagram of part A in the middle;

[0030] Figure 6 This invention proposes a composite constructed wetland system. Figure 1 Schematic diagram of the cross-sectional structure at point AA;

[0031] Figure 7 This invention proposes a composite constructed wetland system. Figure 1 Schematic diagram of the cross-sectional structure at point BB;

[0032] Figure 8 This invention proposes a composite constructed wetland system. Figure 1 Schematic diagram of the cross-sectional structure at point CC.

[0033] In the diagram: 1. Wetland inlet pipe; 2. Submerged plant Vallisneria natans community; 3. Medium-coarse sand planting layer; 4. Gravel layer; 5. Gravel filler; 6. Gabion cage; 7. Permeable geotextile; 8. Aquatic iris; 9. Circulating water pump; 10. Circulating water pipe; 11. Circulating water outlet; 12. Wetland outlet pipe; 13. Brick retaining wall; 14. Planting soil; 15. Thalia dealbata; 16. Yellow iris; 17. Aquatic canna; 18. Strip sedimentation tank; 19. U-shaped perforated bracket; 20. L-shaped perforated plate; 21. Perforated flat plate; 22. Adsorption component; 23. Support leg; 24. Buffer protrusion. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0035] Example 1: Refer to Figures 1-8 A composite constructed wetland system includes an ecological pond with a roughly elongated shape. Within the ecological pond are surface flow wetland units, horizontal subsurface flow wetland units, an internal circulation system unit, and a surrounding plant-based ecological buffer zone unit. The surface flow wetland units are actually two parts on either side of the ecological pond, which can be respectively named the primary surface flow wetland unit and the secondary surface flow wetland units. The horizontal subsurface flow wetland unit is located between the two surface flow wetland units. Each surface flow wetland unit includes a wetland inlet pipe 1 and a wetland outlet pipe 12, respectively located on both sides of the ecological pond. The wetland inlet pipe 1 is used to transport wastewater into the ecological pond, while the wetland outlet pipe 12 is used to overflow purified water. The bottom of the pool is successively laid with a gravel layer 4 and a medium-coarse sand planting layer 3. The medium-coarse sand planting layer 3 is planted with a submerged plant community 2 of Vallisneria natans. The horizontal subsurface flow wetland unit has an inlet end. The horizontal subsurface flow wetland unit includes gravel filler 5 laid in the middle of the ecological pool. The gravel filler 5 divides the ecological pool into two parts, left and right. The sewage output from the wetland inlet pipe 1 will enter the left part of the ecological pool, while the wetland outlet pipe 12 is mainly used to discharge the purified water in the ecological pool. Gabion cages 6 are installed on both sides of the gravel filler 5. The upper layer of the gravel filler 5 is covered with a permeable geotextile 7. The permeable geotextile 7 is covered with planting soil 14 for planting plants. Aquatic irises 8 are planted on the planting soil 14.

[0036] The gabion cage 6 is made of stainless steel, specifically SUS304, with a wire diameter of 3.5mm (±0.05), a mesh size of 3cm×3cm, and a height of 1m. It supports the gravel packing material 5. The gaps between the gravel inside the cage create tortuous flow channels, extending the hydraulic residence time. Simultaneously, the gaps between the cages induce local turbulence, promoting oxygen transport. The gravel packing material 5 has a particle size of 5cm–10cm and a packing thickness of 1m. It effectively removes suspended solids from the water, acts as a biofilm carrier, and forms an alternating anaerobic-aerobic microenvironment, which is beneficial for the degradation of pollutants in the water.

[0037] Specifically, firstly, the pretreated wastewater enters the primary surface flow wetland unit through the wetland inlet pipe 1. The suspended solids and particulate matter in the wastewater are filtered, intercepted and adsorbed by the roots of the submerged plant Vallisneria natans community 2, the medium and coarse sand planting layer 3 and the gravel layer 4. At the same time, the roots of the submerged plant Vallisneria natans community 2 absorb nitrogen and phosphorus nutrients in the water. Microorganisms in the wetland form a biofilm on the surface of the medium and coarse sand planting layer 3 and the gravel layer 4 and around the roots of the submerged plant Vallisneria natans community 2, which decomposes the organic matter in the wastewater into carbon dioxide and inorganic salts, etc.

[0038] Secondly, the wastewater treated by the primary surface flow wetland unit enters the horizontal subsurface flow wetland unit. The two rows of gabion cages 6 are filled with gravel filler 5, which mainly serves to support the gravel filler 5, equivalent to a permeable gravel wall. The pore channels formed between the gravel can slow down the water flow speed, causing suspended solids in the water to settle to the gravel surface due to gravity. The biofilm attached to the surface of the gravel filler 5 can adsorb organic matter in the water and decompose it into inorganic matter through the metabolism of microorganisms. These microorganisms mainly use organic matter for growth and reproduction, thereby achieving the degradation of pollutants. A layer of permeable geotextile 7 is laid on top of the gravel filler 5. Its main function is to prevent the planting soil 14 on the permeable geotextile 7 from seeping into the gaps of the gravel filler 5. At the same time, sewage permeates through the permeable geotextile 7 to moisten the planting soil 14, providing the necessary water for the growth of the aquatic iris 8 planted on the permeable geotextile 7. Over time, the well-developed root system of the aquatic iris 8 on the planting soil 14 will attach to the permeable geotextile 7. The roots and the permeable geotextile 7 form a biofilm, further purifying the water quality. This sequentially stacked purification structure can give it good resistance to shock loads and reduce the footprint.

[0039] Wastewater purified by the horizontal subsurface flow wetland unit enters the secondary surface flow wetland unit. The wastewater purification mechanism of the secondary surface flow wetland unit is the same as that of the primary surface flow wetland unit, where the wastewater undergoes further purification. At the end of the secondary surface flow wetland unit, an internal circulation system unit is installed. This internal circulation system unit transports the treated wastewater back to the primary surface flow wetland unit. This serves three purposes: First, this circulation treatment effectively increases the residence time of wastewater in the system, improving the efficiency of wastewater purification. Second, compared to traditional surface flow wetlands, horizontal subsurface flow wetlands, or combined wetlands, it reduces the land area required for the wetland system. Third, it increases the ecological base flow, with the flowing water increasing dissolved oxygen, reducing pollutants in the water, and promoting energy flow and material cycling to maintain the stability of the ecosystem composed of aquatic plants, animals, and microorganisms.

[0040] During the rainy season, the plant ecological buffer zone units around the wetland can filter and absorb initial rainwater or surface runoff, reducing the direct entry of nitrogen, phosphorus and suspended solids from non-point source pollution into the wetland water body, and indirectly improving the water quality of the wetland.

[0041] Finally, the wastewater passes through the primary surface flow wetland unit, the horizontal subsurface flow wetland unit, and the secondary surface flow wetland unit in sequence. Some of the wastewater is then recycled through the internal circulation system unit. The plant ecological buffer zone unit around the wetland filters and adsorbs the initial rainwater or surface runoff. Finally, after purification at the end of the secondary surface flow wetland unit, the water overflows into the natural water body through the wetland outlet pipe 12.

[0042] Both the wetland inlet pipe 1 and the wetland outlet pipe 12 are made of UPVC. The inlet size of the wetland inlet pipe 1 is DN100, while the inlet size of the wetland outlet pipe 12 is DN150. The planting density of the submerged plant Vallisneria natans community 2 is 50 plants / m². 2 The submerged plant community 2 was planted in water at a depth of 1m. The medium-coarse sand planting layer 3 had a particle size of 0.5mm-2mm and a thickness of 20cm. The gravel layer 4 had a particle size of 2cm-3cm and a thickness of 10cm.

[0043] The permeable geotextile 7 mentioned above is made of short-fiber needle-punched material, and its unit mass area is 150g / m². 2 -200g / m 2 The permeable geotextile 7 has a tensile strength of 20kN / m-30kN / m, a permeability coefficient of 0.05cm / s-0.1cm / s, and an equivalent pore size of 0.1mm-0.2mm. The planting soil 14 on top of the permeable geotextile 7 is 10cm thick, mainly providing planting conditions for the aquatic iris 8 planted on the planting soil 14. The planting density of the aquatic iris 8 planted on the planting soil 14 is 25 plants / m². 2 The roots can attach to the permeable geotextile 7, which can absorb nutrients in the water and also act as a biofilm carrier.

[0044] The instruction manual indicates that, in practice, the ecological pond includes, in order of water flow direction, a primary surface flow wetland unit, a horizontal subsurface flow wetland unit, a secondary surface flow wetland unit, an internal circulation system unit, and a plant ecological buffer zone unit surrounding the wetland. Depending on the wastewater quality, a flocculation sedimentation tank can be installed in front of the inlet of the horizontal subsurface flow wetland to ensure good wetland operation.

[0045] Example 2: Refer to Figures 1-4 A composite constructed wetland system, basically the same as in Example 1, but further:

[0046] The aforementioned internal circulation system unit includes a circulating water pump 9 placed in the ecological pond. The output end of the circulating water pump 9 is connected to a circulating water pipe 10, and the output end of the circulating water pipe 10 is provided with a circulating water outlet 11. The circulating water pump 9 and the circulating water outlet 11 are respectively located on both sides of the ecological pond.

[0047] Specifically, during use, the circulating water pump 9 is placed at the end of the secondary surface flow wetland unit, so that the purified water can be transported back to the primary surface flow wetland unit through the circulating outlet 11. This has three functions: First, this circulating treatment can effectively increase the residence time of sewage in the system and improve the efficiency of sewage purification; second, compared with traditional surface flow wetlands, horizontal subsurface flow wetlands, or combined wetlands, it reduces the land area of ​​the wetland system; third, it increases the ecological base flow, and the flowing water increases dissolved oxygen, reduces pollutants in the water, promotes energy flow and material cycling, so as to maintain the stability of the ecosystem composed of aquatic plants, animals and microorganisms.

[0048] The aforementioned circulating water outlet 11 mainly consists of a first outlet 1101, a second outlet 1102, and a third outlet 1103 arranged at equal intervals. The input ends of the first outlet 1101, the second outlet 1102, and the third outlet 1103 are all connected to the output end of the circulating water pipe 10, and the diameters of the first outlet 1101, the second outlet 1102, and the third outlet 1103 are all DN20. The circulating water pump 9 is a submersible pump with a flow rate of 5 m³ / h. 3 / h; The size of the circulating water pipe 10 is DN50, and the material is UPVC pipe. The circulating water pipe 10 is placed in the planting soil 14 below 16 irises; The diameter of the first outlet 1101, the second outlet 1102 and the third outlet 1103 are all DN20. The three sets of pipes can make the water flow into the ecological pond more evenly.

[0049] Example 3: Reference Figures 1-4 as well as Figures 6-8 A composite constructed wetland system, basically the same as in Example 2, but further:

[0050] The plant ecological buffer zone unit surrounding the aforementioned wetland includes a ring-shaped brick retaining wall 13 encircling the interior of the ecological pond. A slope protection is provided between the inner wall of the ecological pond and the brick retaining wall 13, and planting soil 14 is laid on the slope protection. The brick retaining wall 13 is placed above the gravel layer 4, and the bottom of the brick retaining wall 13 meets the planting soil 14. Canna indica 15, yellow iris 16 and aquatic canna lily 17 are planted on the planting soil 14.

[0051] Specifically, during the rainy season, the initial rainwater or surface runoff around the wetland carries a large amount of mud and sand. Through the filtration and adsorption of the roots of emergent plants such as Thalia dealbata 15, Iris tectorum 16, and Canna indica 17 in the plant ecological buffer zone unit and the planting soil 14, the nitrogen, phosphorus and suspended solids in non-point source pollution directly enter the wetland water body, thus indirectly improving the water quality of the wetland.

[0052] The outer wall of the aforementioned brick retaining wall 13 is provided with buffer protrusions 24 arranged at equal intervals. The cross-sectional shape of the buffer protrusions 24 is semi-circular or triangular. Since the circulating water pump 9 will make the water in the ecological pond flow continuously, the continuously flowing water will impact the brick retaining wall 13. The buffer protrusions 24 arranged at equal intervals can buffer the flowing water and reduce the erosion of the outer wall of the brick retaining wall 13 by the water.

[0053] The brick retaining wall 13 is 1.5m high and its main function is to support the backfill planting soil 14 between the bank slope and the brick retaining wall 13. The planting density of emergent plants Thalia dealbata 15, Iris tectorum 16 and Canna indica 17 is 25 plants / m². 2 .

[0054] Example 4: Reference Figure 3 as well as Figure 5 A composite constructed wetland system, basically the same as in Example 3, but with a further improvement:

[0055] The inlet end of the aforementioned horizontal subsurface flow wetland unit is equipped with a strip sedimentation tank 18. The upper end of the strip sedimentation tank 18 is equipped with a U-shaped hollow bracket 19. The gravel layer 4 and the medium-coarse sand planting layer 3 at the top of the strip sedimentation tank 18 are located inside the U-shaped hollow bracket 19. Both sides of the upper end of the strip sedimentation tank 18 are equipped with L-shaped hollow plates 20 that are closely attached to the U-shaped hollow bracket 19. Both the U-shaped hollow bracket 19 and the L-shaped hollow plate 20 are equipped with permeable mesh for water and mud. The U-shaped hollow bracket 19 and the L-shaped hollow plate 20 are mainly used to limit the gravel layer 4 and the medium-coarse sand planting layer 3 above the strip sedimentation tank 18, preventing the gravel layer 4 and the medium-coarse sand planting layer 3 from entering the strip sedimentation tank 18.

[0056] Specifically, after the primary surface flow wetland unit for wastewater purification and before entering the gravel filler 5 in the middle of the ecological pond, some fine impurities will pass through the medium-coarse sand planting layer 3 and the gravel layer 4, and will remain in the strip sedimentation tank 18 under the action of the flowing water. This can significantly reduce the entry of fine impurities into the gravel gaps of the gravel filler 5, ensuring the sustainability of the ecology on the gravel filler 5.

[0057] The strip sedimentation tank 18 is fixedly equipped with a horizontally arranged perforated plate 21. An adsorption element 22 is provided on the perforated plate 21. The adsorption element 22 can be non-woven fabric and is filled with nitrogen-eating bacteria. The bottom of the U-shaped perforated bracket 19 is connected to a support leg 23 that presses on the adsorption element 22. Thus, the adsorption element 22 can effectively adsorb impurities and sludge. The nitrogen-eating bacteria can convert nitrogen compounds such as ammonia, nitrite, and nitrate in the environment into nitrogen gas or other forms, reducing the pollution of the ecosystem by excessive nitrogen and playing a good protective role for the ecology in the gravel filler 5.

[0058] In practical application, the present invention firstly, the pretreated wastewater enters the primary surface flow wetland unit through the wetland inlet pipe 1. The suspended solids and particulate matter in the wastewater are filtered, intercepted and adsorbed by the roots of the submerged plant Vallisneria natans community 2, the medium and coarse sand planting layer 3 and the gravel layer 4. At the same time, the roots of the submerged plant Vallisneria natans community 2 absorb nitrogen and phosphorus nutrients in the water. Microorganisms in the wetland form a biofilm on the surface of the medium and coarse sand planting layer 3 and the gravel layer 4 and around the roots of the submerged plant Vallisneria natans community 2, which decomposes the organic matter in the wastewater into carbon dioxide and inorganic salts, etc.

[0059] Secondly, the wastewater treated by the primary surface flow wetland unit enters the horizontal subsurface flow wetland unit. The pore channels formed between the gravel slow down the water flow, causing suspended solids in the water to settle to the gravel surface due to gravity. The biofilm attached to the surface of the gravel filler 5 can adsorb organic matter in the water and decompose it into inorganic matter through the metabolism of microorganisms. These microorganisms mainly use organic matter for growth and reproduction, thereby achieving the degradation of pollutants. A layer of permeable geotextile 7 is laid on top of the gravel filler 5. Its main function is to prevent the planting soil 14 on the permeable geotextile 7 from seeping into the gaps of the gravel filler 5. At the same time, the wastewater permeates through the permeable geotextile 7 to moisten the planting soil 14, providing the necessary water for the growth of the aquatic iris 8 planted on the permeable geotextile 7. Over time, the well-developed root system of the aquatic iris 8 on the planting soil 14 will attach to the permeable geotextile 7, and the roots and permeable geotextile 7 will form a biofilm, further purifying the water quality.

[0060] Wastewater purified by the horizontal subsurface flow wetland unit enters the secondary surface flow wetland unit. The wastewater purification mechanism of the secondary surface flow wetland unit is the same as that of the primary surface flow wetland unit, where the wastewater undergoes further purification. An internal circulation system unit is installed at the end of the secondary surface flow wetland unit. Wastewater from the secondary surface flow wetland unit is pumped by the circulation pump 9 through the circulation pipe 10 into the circulation water outlet 11 near the inlet pipe 1 of the primary surface flow wetland. The wastewater is then evenly discharged into the primary surface flow wetland unit through the first water outlet 1101, the second water outlet 1102, and the third water outlet 1103. This process has three functions: First, this circulation treatment can effectively increase the residence time of wastewater in the system and improve the efficiency of wastewater purification. Second, compared with traditional surface flow wetlands, horizontal subsurface flow wetlands, or combined wetlands, it reduces the land area of ​​the wetland system. Third, it increases the ecological base flow, and the flowing water increases dissolved oxygen, reduces pollutants in the water, promotes energy flow and material circulation, and maintains the stability of the ecosystem composed of aquatic plants, animals, and microorganisms.

[0061] During the rainy season, the initial rainwater or surface runoff around the wetland carries a large amount of mud and sand. Through the filtration and adsorption of the roots of emergent plants such as Thalia dealbata 15, Iris tectorum 16, and Canna indica 17 in the plant ecological buffer zone unit and the planting soil 14, the nitrogen, phosphorus and suspended solids in non-point source pollution directly enter the wetland water body, indirectly improving the water quality of the wetland.

[0062] Finally, the wastewater passes through the primary surface flow wetland unit, the horizontal subsurface flow wetland unit, and the secondary surface flow wetland unit in sequence. Some of the wastewater is then recycled through the internal circulation system unit. The plant ecological buffer zone unit around the wetland filters and adsorbs the initial rainwater or surface runoff. Finally, after purification at the end of the secondary surface flow wetland unit, the water overflows into the natural water body through the wetland outlet pipe 12.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A composite constructed wetland system, comprising an ecological pond, characterized in that, The ecological pond is equipped with surface flow wetland units, horizontal subsurface flow wetland units, internal circulation system units, and plant ecological buffer zones around the wetlands. The surface flow wetland unit includes a wetland inlet pipe (1) and a wetland outlet pipe (12) respectively set on both sides of the ecological pond. The bottom of the ecological pond is successively laid with a gravel layer (4) and a medium-coarse sand planting layer (3). The medium-coarse sand planting layer (3) is planted with a submerged plant community (2) of Vallisneria natans. The horizontal subsurface flow wetland unit includes gravel filler (5) laid in the middle of the ecological pond, gabion cages (6) installed on both sides of the gravel filler (5), the upper layer of the gravel filler (5) is covered with permeable geotextile (7), the upper part of the permeable geotextile (7) is covered with planting soil (14), and aquatic irises (8) are planted on the planting soil (14).

2. The composite constructed wetland system according to claim 1, characterized in that, The internal circulation system unit includes a circulating water pump (9) placed in the ecological pond. The output end of the circulating water pump (9) is connected to a circulating water pipe (10). The output end of the circulating water pipe (10) is provided with a circulating water outlet (11). The circulating water pump (9) and the circulating water outlet (11) are respectively located on both sides of the ecological pond.

3. The composite constructed wetland system according to claim 1, characterized in that, The plant ecological buffer zone unit around the wetland includes a ring-shaped brick retaining wall (13) surrounding the inside of the ecological pond. A slope protection is provided between the inner wall of the ecological pond and the brick retaining wall (13), and planting soil (14) is laid on the slope protection. The brick retaining wall (13) is placed above the gravel layer (4), and the bottom of the brick retaining wall (13) meets the planting soil (14). Canna indica (15), yellow iris (16) and aquatic canna (17) are planted on the planting soil (14).

4. The composite constructed wetland system according to claim 1, characterized in that, The horizontal subsurface flow wetland unit is provided with a strip sedimentation tank (18) at the water inlet end. The upper end of the strip sedimentation tank (18) is provided with a U-shaped hollow bracket (19). The gravel layer (4) and the medium-coarse sand planting layer (3) at the top of the strip sedimentation tank (18) are located inside the U-shaped hollow bracket (19). Both sides of the upper end of the strip sedimentation tank (18) are provided with L-shaped hollow plates (20) that are closely attached to the U-shaped hollow bracket (19).

5. The composite constructed wetland system according to claim 4, characterized in that, A horizontally arranged perforated plate (21) is fixedly installed inside the strip sedimentation tank (18). An adsorption element (22) is provided on the perforated plate (21). The bottom of the U-shaped perforated bracket (19) is connected to a support leg (23) that presses on the adsorption element (22).

6. The composite constructed wetland system according to claim 3, characterized in that, The outer wall of the brick retaining wall (13) is provided with buffer protrusions (24) arranged at equal intervals, and the cross-sectional shape of the buffer protrusions (24) is semi-circular or triangular.

7. The composite constructed wetland system according to claim 1, characterized in that, Both the wetland inlet pipe (1) and the wetland outlet pipe (12) are made of UPVC, and the planting density of the submerged plant Vallisneria natans community (2) is 50 plants / m². 2 The planting water depth of the submerged plant Vallisneria natans community (2) is 1m, the particle size of the medium-coarse sand planting layer (3) is 0.5mm-2mm, the laying thickness of the medium-coarse sand planting layer (3) is 20cm, the particle size of the gravel layer (4) is 2cm-3cm, and the laying thickness of the gravel layer (4) is 10cm.

8. The composite constructed wetland system according to claim 2, characterized in that, The circulating water outlet (11) is mainly composed of a first outlet (1101), a second outlet (1102), and a third outlet (1103) arranged at equal intervals. The input ends of the first outlet (1101), the second outlet (1102), and the third outlet (1103) are all connected to the output end of the circulating water pipe (10). The diameter of the first outlet (1101), the second outlet (1102), and the third outlet (1103) is DN20.

9. The composite constructed wetland system according to claim 1, characterized in that, The permeable geotextile (7) is made of short-fiber needle-punched material, and the permeable geotextile (7) has a unit mass area of ​​150g / m². 2 -200g / m 2 The permeable geotextile (7) has a tensile strength of 20kN / m-30kN / m and a permeability coefficient of 0.05cm / s-0.1cm / s.

10. The composite constructed wetland system according to claim 3, characterized in that, The brick retaining wall (13) is 1.5m high, and the planting density of Thalia dealbata (15), Iris tectorum (16), and Canna indica (17) is 25 plants / m². 2 .

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