Multi-stage constructed wetland-ecological pond system for synchronously and intensively removing nitrogen and phosphorus

Abstract

The invention relates to the technical field of sewage treatment, in particular to a multi-stage constructed wetland-ecological pond system for synchronously and intensively removing nitrogen and phosphorus. A first-stage constructed wetland, a second-stage ecological pond and a third-stage constructed wetland which are sequentially connected in a falling manner are arranged in the system, and the first-stage constructed wetland and the third-stage constructed wetland are both horizontal subsurface flow type constructed wetlands; wetland plants are planted in the first-stage constructed wetland and the third-stage constructed wetland; ecological pond plants are planted in the second-stage ecological pond through floating rafts, non-woven fabric is arranged below the floating rafts, and microalgae are enriched on the non-woven fabric; according to the invention, an alternating anaerobic / anoxic-aerobic-anaerobic / anoxic environment formed by each stage of system is utilized to enhance the removal of oxidation-state and reduction-state nitrogen and the absorption and removal of phosphorus, the removal rate of ammonia nitrogen can reach 98%, the removal rate of nitrate nitrogen can reach 98.8%, the removal rate of total nitrogen can reach 98.07%, the removal rate of COD (Chemical Oxygen Demand) can reach 85.02%, and the removal rate of total phosphorus can reach 78%; wide application prospects are realized.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a multi-stage artificial wetland-ecological pond system for synchronously enhancing the removal of nitrogen and phosphorus. Background Art

[0002] The traditional artificial wetland-ecological pond combination technology uses the anaerobic / anoxic-aerobic process of the artificial wetland itself to achieve the removal of ammonia nitrogen in the nitrification process and nitric nitrogen in the denitrification process. At the same time, it uses the adsorption effect of the matrix to fix phosphorus in the matrix, and then uses the absorption effect of plants in the ecological pond to further remove nitrogen and phosphorus pollutants in the sewage.

[0003] However, because artificial wetlands have been flooded with sewage for a long time, the dissolved oxygen in them is seriously insufficient, which often leads to excessive ammonia nitrogen in the effluent. Eco-ponds are mostly used as ecological landscapes, and the nitrogen and phosphorus removed by plants are less than 10%, making the nitrogen and phosphorus removal efficiency of the artificial wetland-ecological pond combination technology low. The problem of low dissolved oxygen can be improved to a certain extent by installing aeration devices or fountains in the ecological ponds. However, this method requires a lot of investment and brings complexity to process maintenance.

[0004] Therefore, the present invention proposes a multi-stage artificial wetland-ecological pond system to construct an "anaerobic / anoxic-aerobic-anaerobic / anoxic" environment, achieve simultaneous enhanced removal of nitrogen and phosphorus, and greatly reduce investment and maintenance costs, which has broad application prospects. Summary of the invention

[0005] The purpose of the present invention is to provide a multi-stage artificial wetland-ecological pond system for synchronously enhancing the removal of nitrogen and phosphorus, so as to solve the problem of low ammonia nitrogen removal efficiency in existing artificial wetlands due to insufficient dissolved oxygen.

[0006] To achieve the above object, the present invention adopts the following technical scheme: a multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus, comprising a first-stage artificial wetland, a second-stage ecological pond and a third-stage artificial wetland connected in sequence; constructing an "anaerobic / anoxic-aerobic-anaerobic / anoxic" environment;

[0007] The first-level artificial wetland and the third-level artificial wetland are both horizontal subsurface flow artificial wetlands; wetland plants are planted in the first-level artificial wetland and the third-level artificial wetland;

[0008] Ecological pond plants are planted in the second-level ecological pond in the form of floating rafts, non-woven fabrics are arranged below the floating rafts, and microalgae are enriched on the non-woven fabrics.

[0009] Furthermore, a first gravel support layer is arranged at the bottom of the first-level artificial wetland and the third-level artificial wetland, and a mixed matrix of zeolite and volcanic stone is arranged on the first gravel support layer; a second gravel support layer is arranged at the bottom of the secondary ecological pond.

[0010] Furthermore, the area ratio of the first-level artificial wetland, the second-level ecological pond and the third-level artificial wetland is 1:0.5~1:0.5~1.

[0011] Furthermore, the particle size of gravel in the first gravel supporting layer is 2-3 cm; the particle sizes of zeolite and volcanic rock in the mixed matrix of zeolite and volcanic rock are both 1-2 cm, and the volume ratio of zeolite to volcanic rock is 1:1; the particle size of gravel in the second gravel supporting layer is 2-3 cm.

[0012] Furthermore, the first-level artificial wetland is respectively provided with a first baffle on the water inlet side and the water outlet side, the first gravel supporting layer and the mixed matrix of zeolite and volcanic stone are located between the first baffles on both sides, the total water inlet is located in the middle of the water inlet side of the first-level artificial wetland, and the water outlet of the first-level artificial wetland falls into the second-level ecological pond; a second baffle is provided on the water outlet side of the second-level ecological pond, and the second-level ecological pond falls into the third-level artificial wetland; the third-level artificial wetland is provided with a first baffle on the water inlet side and a third baffle on the water outlet side, the first gravel supporting layer and the mixed matrix of zeolite and volcanic stone are located between the first baffle and the third baffle, and the total water outlet is located above the water outlet side of the third-level artificial wetland.

[0013] Furthermore, the first baffle is a baffle with holes; the second baffle is a baffle without holes with a hollow bottom, and the height of the hollowing is consistent with the height of the second gravel supporting layer; the third baffle is a baffle with holes at the bottom and no holes at the top, and the height of the holes in the third baffle is consistent with the height of the first gravel supporting layer in the third-level artificial wetland.

[0014] Furthermore, in the first-level artificial wetland and the third-level artificial wetland, the water level is controlled at 0 to 10 cm below the substrate layer.

[0015] Furthermore, the wetland plants are rooted in a mixed matrix of zeolite and volcanic rock, and the wetland plants include yellow iris, iris, reed and canna, with a planting density of 90 to 110 plants / m 2 .

[0016] Furthermore, the roots of the ecological plants are rooted in the water through the non-woven fabric. The ecological plants include cattail, iris and calamus, and the planting density is 40 plants / m 2 .

[0017] Furthermore, in the multi-stage artificial wetland-ecological pond system, the removal rate of ammonia nitrogen can reach 98%, the removal rate of nitrate nitrogen can reach 98.8%, the removal rate of total nitrogen can reach 98.07%, the removal rate of COD can reach 85.02%, and the removal rate of total phosphorus can reach 78%.

[0018] Beneficial effects of the present invention:

[0019] 1. The system of the present invention constructs "anaerobic / anoxic-aerobic-anaerobic / anoxic", which solves the problem of low ammonia nitrogen removal efficiency in traditional artificial wetlands due to insufficient internal dissolved oxygen;

[0020] 2. The system of the present invention achieves enhanced removal of nitrogen and phosphorus during the reoxygenation process by planting eco-pond plants and enriching microalgae in the eco-pond, and greatly reduces investment and maintenance costs, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a configuration diagram of the multi-stage artificial wetland-ecological pond system of the present invention;

[0022] Figure 2 It is a schematic diagram of the structure of the nonwoven fabric of the present invention;

[0023] Figure 3 It is the adsorption curve of ammonia nitrogen by the combination of volcanic rock + zeolite of the present invention;

[0024] Figure 4 It is the adsorption curve of nitrate nitrogen by the combination of volcanic rock + zeolite of the present invention.

[0025] The names corresponding to the marks in the figure are:

[0026] 1. First-level artificial wetland; 2. First baffle; 3. First gravel support layer; 4. Mixed matrix of zeolite and volcanic rock; 5. Total water inlet; 6. Wetland plants; 7. Second-level ecological pond; 8. Second gravel support layer; 9. Second baffle; 10. Eco-pond plants; 11. Third-level artificial wetland; 12. Third baffle; 13. Total water outlet; 14. Non-woven fabric; 15. Floating raft ball; 16. Fixed rope. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0028] Process implementation:

[0029] The present invention is mainly composed of a first-level artificial wetland 1, a second-level ecological pond 7 and a third-level artificial wetland 11, wherein the artificial wetland is a horizontal submerged flow type; the effective area ratio of the three-level treatment unit is 1: (0.5-1): (0.5-1), and the water level is controlled at 0-10 cm below the first and third-level artificial wetland matrix layers.

[0030] In the first-level artificial wetland 1 and the third-level artificial wetland 11, a first gravel supporting layer 3 is provided, and a mixed matrix 4 of zeolite and volcanic rock is provided above the first gravel supporting layer 3; through the adsorption kinetics experiment of multiple types of matrices, it is determined that gravel with a particle size of 2 to 3 cm is used as the supporting layer, and volcanic rock and zeolite with a particle size of 1 to 2 cm are uniformly mixed as the main reaction layer matrix filling, wherein gravel has strong adsorption performance for nitrate nitrogen and phosphorus, but its biocompatibility is poor, and it is suitable as a supporting layer, while zeolite has better performance only in ammonia nitrogen adsorption, and volcanic rock is the best in nitrate nitrogen and phosphorus adsorption. The present invention combines the selective adsorption characteristics of the two and uses them in combination as the main reaction layer matrix of the artificial wetland, thereby achieving the purpose of synchronously enhancing the adsorption and removal of ammonia nitrogen, nitrate nitrogen and phosphorus; gravel with a particle size of 2 to 3 cm is laid at the bottom of the second-level ecological pond 7 as the second gravel supporting layer 8, and during the laying process, slightly larger gravel is selected to be laid at the bottom, and smaller gravel is laid at the top to prevent gravel from being lost from the drain outlet at the bottom of the second-level ecological pond 7.

[0031] Wetland plants 6 are planted in the first-level artificial wetland 1 and the third-level artificial wetland 11, including yellow iris, iris, reed, canna, etc., with a density of 90 to 110 plants / m 2 The second-level ecological pond 7 is planted with ecological pond plants 10 in a floating raft style, including plants with narrow leaves such as cattails, irises, and calamus, with a density of 40 to 50 plants / m 2 A layer of 1mm thick non-woven fabric 14 is laid flat under the raft. Plants are fixed in the plastic raft balls 15, and their roots pass through the non-woven fabric 14 and are immersed in the water. The raft balls 15 and the non-woven fabric 14 are fixed to the water surface by fixing ropes 16 to prevent the raft balls 15 from floating irregularly.

[0032] The non-woven fabric 14 provides a large number of attachment sites for the microalgae, which are used to intercept the microalgae grown in the sewage and enrich them on the surface of the water body, thereby ensuring the sunlight exposure required for photosynthesis and facilitating the subsequent disposal of the microalgae.

[0033] The first artificial wetland 1 is provided with a first baffle 2 on the water inlet side and the water outlet side, respectively. The first gravel support layer 3 and the zeolite and volcanic stone mixed matrix 4 are located between the first baffles 2 on both sides. The total water inlet 5 is located in the middle of the water inlet side of the first artificial wetland 1. The water outlet of the first artificial wetland 1 falls into the second ecological pond 7. A second baffle 9 is provided on the water outlet side of the second ecological pond 7. The second ecological pond 7 falls into the third artificial wetland 11. The third artificial wetland 11 is provided with a first baffle 2 on the water inlet side and a The third baffle 12, the first gravel supporting layer 3 and the zeolite and volcanic stone mixed matrix 4 are located between the first baffle 2 and the third baffle 12, and the total water outlet 13 is located above the outlet side of the third artificial wetland 11; the first baffle 2 is a baffle with holes; the second baffle 9 is a baffle without holes with a hollow bottom, and the height of the hollowing is consistent with the height of the second gravel supporting layer 8; the third baffle 12 is a baffle with holes at the bottom and no holes at the top, and the height of the holes in the third baffle 12 is consistent with the height of the first gravel supporting layer 3 in the third artificial wetland 11.

[0034] How to run:

[0035] Start-up: Mix the sludge from the anoxic tank of the sewage treatment plant with the influent water and let it enter the cascade combination system with the influent water for microbial inoculation.

[0036] The system was initially started up using artificially simulated sewage with a carbon: nitrogen: phosphorus ratio of 100:20:1 as the influent. The hydraulic retention time was set to 24-48 hours and the system was run continuously for 15-20 days. The system effluent was stable and the microalgae biofilm was clearly enriched on the eco-pond non-woven fabric 14, which was visible to the naked eye. The system was considered to have been started up.

[0037] Operation: Sewage with a low carbon-nitrogen ratio (10:3) enters the system from the middle water inlet of the first artificial wetland 1, and flows into the matrix through the holes on the first baffle 2 after the total water inlet 5. In the first artificial wetland 1, volcanic rocks, zeolites and gravel are used to adsorb and remove nitrate nitrogen, ammonia nitrogen and phosphorus in the sewage, and nitrogen and phosphorus are assimilated and removed through the absorption of plants, and various forms of nitrogen, phosphorus and organic matter are removed at the first level through the aerobic nitrification, anoxic denitrification and phosphorus removal of microorganisms on the matrix; after the sewage passes through the holes on the first baffle 2 on the outlet side, it falls into the second ecological pond 7 (water level difference 10cm).

[0038] After passing through the first artificial wetland 1, the dissolved oxygen in the sewage has been greatly reduced. After entering the second ecological pond 7 from the upper waterfall, the waterfall process reoxygenates the sewage for the first time. At the same time, the ecological pond forms a more obvious dissolved oxygen gradient in the vertical direction due to the photosynthesis of the upper microalgae. The photosynthesis of the upper microalgae and the oxygen secretion of plants reoxygenate the sewage for the second time, and the performance of aerobic treatment processes such as ammonia oxidation, nitrification and organic matter oxidation in the second ecological pond 7 and the third artificial wetland 11 is enhanced by utilizing the characteristics of the bacterial-algae symbiotic system; the lower layer of the second ecological pond 7 is in a flooded state for a long time, and nitrate nitrogen is removed in its anaerobic / anoxic environment. After being treated in the second ecological pond 7, the sewage enters the water outlet of the ecological pond from the bottom to the top through the pores at the bottom of the second baffle 9, flows out from the water outlet, and enters the third artificial wetland 11 from the upper waterfall (water level difference 10cm). The waterfall process further re-oxygenates the sewage for the third time, and after the third-level artificial wetland 11 further strengthens the removal of various forms of nitrogen and phosphorus, it is discharged from the system to the natural water body through its outlet.

[0039] Principle of the invention:

[0040] The present invention optimizes the artificial wetland-ecological pond combination technology through the following three ideas. First, through substrate optimization, a substrate combination with better nitrogen and phosphorus adsorption performance is selected to improve the removal contribution of the physical process of the artificial wetland; second, by spontaneously growing microalgae in the ecological pond, the biological aeration of the microalgae is utilized to continuously reoxygenate the system, provide sufficient electron acceptors for the ammonia oxidation process, and provide a favorable aerobic environment for aerobic phosphorus phagocytosis of microorganisms. At the same time, the absorption and assimilation of nitrogen and phosphorus by microalgae is much stronger than that of large plants; third, utilizing the characteristics of the cascade combination technology, a multi-level artificial wetland-ecological pond combination system is constructed, and the alternating "anaerobic / anoxic-aerobic-anaerobic / anoxic" environment formed by each level of the system is utilized to strengthen the removal of oxidized and reduced nitrogen and the absorption and removal of phosphorus.

[0041] Example 1

[0042] A multi-level artificial wetland-ecological pond combined pilot system was constructed, which mainly consisted of a first-level artificial wetland 1, a second-level ecological pond 7 and a third-level artificial wetland 11; among them, the first and third-level horizontal subsurface flow artificial wetlands were 110 cm long, 40 cm wide and 60 cm deep, and the second-level ecological pond 7 was 110 cm long, 40 cm wide and 60 cm deep; the area ratio of the three-level treatment units was 1:1:1.

[0043] The first and third level horizontal subsurface flow wetlands have a first gravel support layer 3 with a depth of 20 cm and a diameter of 2 to 3 cm at the bottom, and a 40 cm deep mixed matrix of volcanic rocks (particle size 1 to 2 cm) and zeolite (particle size 1 to 2 cm) (mixed in a volume ratio of 1:1) is laid on the first gravel support layer 3; perforated baffles are arranged behind the water inlet and before the water outlet of the first and third level artificial wetlands to evenly distribute water; a non-porous baffle with a hollow bottom is arranged in front of the water outlet of the second level ecological pond 7 to divert sewage so that it flows into the ecological pond from top to bottom and then flows out of the ecological pond outlet from bottom to top, thereby avoiding the formation of a dead water area, and a second gravel support layer 8 with a particle size of 2 to 3 cm is laid at the bottom of the ecological pond.

[0044] Iris pumila was planted in the first and third level artificial wetlands, with a planting density of 100 plants / m 2 In the second-level ecological pond 7, cattails are planted in floating rafts with a planting density of 40 plants / m 2 A layer of 1 mm thick non-woven fabric 14 is laid flat under the raft, and the plant roots pass through the non-woven fabric 14 and are immersed in the water.

[0045] Startup: The sludge from the anoxic tank of the sewage treatment plant is mixed with the influent and enters the cascade combination system with the influent for microbial inoculation. The artificially configured simulated sewage with carbon: nitrogen: phosphorus = 100:20:1 is used as the influent for initial startup. The water quality is COD = 100mg / L, TN = 20mg / L, TP = 1mg / L, the water level is controlled 10cm below the first and third artificial wetland matrix layers, and the hydraulic retention time is set to 24h. After 15 days of continuous operation, the system effluent is stable, and the microalgae biofilm that is obviously enriched can be seen on the non-woven fabric 14 of the ecological pond with the naked eye, and the system startup is considered complete.

[0046] Operation: With simulated sewage inflow of chemical oxygen demand = 50 mg / L, ammonia nitrogen = 5 mg / L, nitrate nitrogen = 10 mg / L and total phosphorus = 0.5 mg / L, the sewage enters the system from the total water inlet 5 in the middle of the first-level artificial wetland 1, and flows into the matrix through the perforated baffle behind the water inlet. After a series of treatment processes, the sewage passes through the perforated baffle in front of the outlet, flows out from the outlet and falls into the second-level ecological pond 7 (water level difference 10 cm). After the sewage is reoxygenated and treated in the second-level ecological pond 7, it flows from the pores at the bottom of the non-porous baffle to the outlet of the ecological pond from bottom to top, and flows out from the outlet, and enters the third-level artificial wetland 11 from the upper waterfall (water level difference 10 cm). After the third-level artificial wetland 11 further strengthens the removal of various forms of nitrogen and phosphorus, it is discharged from the system through its outlet.

[0047] Embodiment effect:

[0048] During the operation of the system, the dissolved oxygen in the effluent of the first-level artificial wetland 1 was maintained at only 0.05 mg / L, which was an anaerobic state, while the dissolved oxygen in the effluent of the second-level ecological pond 7 was maintained at 1.64 mg / L, and the dissolved oxygen in the effluent of the third-level artificial wetland 11 dropped to 0.07 mg / L. The above results show that the horizontal subsurface flow artificial wetland has serious oxygen consumption, and the dissolved oxygen has been significantly improved through the reoxygenation process of the microalgae in the second-level ecological pond 7, which is conducive to the oxygen consumption process of the second-level ecological pond 7 and its subsequent treatment processes.

[0049] In the final effluent of the third-level artificial wetland 11, the removal rates of ammonia nitrogen, nitrate nitrogen, total nitrogen, COD and total phosphorus reached 97.8%, 98.8%, 98.07%, 85.02% and 78% respectively, and the effluent concentrations were 0.11 mg / L, 0.12 mg / L, 0.29 mg / L, 7.49 mg / L and 0.11 mg / L respectively, realizing the simultaneous enhanced removal of various forms of nitrogen, phosphorus and organic matter.

[0050] Example 2

[0051] In order to reduce land occupation, Example 2 provides an implementation method for less land occupation, which greatly reduces the pool area of ​​the second-level ecological pond 7 and the third-level artificial wetland 11, while the area of ​​the first-level artificial wetland 1 remains unchanged, and the area ratio of the three treatment units is 1:0.5:0.5, and its configuration and operation mode are consistent with Example 1. In this embodiment, its treatment performance will decrease, but under the premise of reducing the occupied area, the performance reaches a higher effect than the traditional artificial wetland-ecological pond combination system.

[0052] Implementation effect:

[0053] During the operation of the system, the dissolved oxygen in the effluent of the first-level artificial wetland 1 was maintained at only 0.05 mg / L, while the second-level ecological pond 7 achieved reoxygenation and its dissolved oxygen was maintained at 1.2 mg / L, and the dissolved oxygen in the effluent of the third-level artificial wetland 11 dropped back to 0.06 mg / L.

[0054] In the final effluent of the third-level artificial wetland 11, the removal rates of ammonia nitrogen, nitrate nitrogen, total nitrogen, COD and total phosphorus reached 98%, 63.9%, 75.2%, 85.02% and 70.00% respectively, and the effluent concentrations were 0.10mg / L, 3.61mg / L, 3.72mg / L, 7.49mg / L and 0.15mg / L respectively, achieving the simultaneous enhanced removal of various forms of nitrogen, phosphorus and organic matter.

[0055] The removal rate was lower than that of Example 1 in terms of nitrate nitrogen and total nitrogen removal, but it still achieved the ideal enhanced removal effect in terms of ammonia nitrogen removal, which is attributed to the enhancement of the aerobic treatment process by using microalgae reoxygenation in the present invention.

[0056] Comparative Example 1

[0057] A multi-stage artificial wetland-ecological pond combination pilot control system was constructed. The system was a traditional artificial wetland-ecological pond combination, in which the ecological pond did not use non-woven fabric 14 to intercept and utilize microalgae, and its first and third stage artificial wetland substrates used pure gravel. Other configurations and operating methods were consistent with Example 2.

[0058] Implementation effect:

[0059] During the operation of the system, the dissolved oxygen in the effluent of the first-level artificial wetland 1 was maintained at only 0.05 mg / L, while no reoxygenation effect was found in the second-level ecological pond 7, and its dissolved oxygen was maintained at 0.04 mg / L. The dissolved oxygen in the effluent of the third-level artificial wetland 11 was maintained at 0.05 mg / L.

[0060] In the final effluent of the third-level artificial wetland 11, the removal rates of ammonia nitrogen, nitrate nitrogen, total nitrogen, COD and total phosphorus reached 66.4%, 53.3%, 60.2%, 70% and 58% respectively, and the effluent concentrations were 1.68mg / L, 4.67mg / L, 5.97mg / L, 15.00mg / L and 0.21mg / L respectively.

[0061] The comparative example is lower than the example in terms of various pollutant removal performances, especially in terms of ammonia nitrogen removal, which shows that the process can achieve reoxygenation in the system and simultaneously improve the nitrogen and phosphorus pollutant removal performances through the technical optimization method of the present invention.

[0062] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus, characterized in that: It includes a first-level artificial wetland (1), a second-level ecological pond (7) and a third-level artificial wetland (11) which are connected in sequence; an "anaerobic / anoxic-aerobic-anaerobic / anoxic" environment is constructed; The first-level artificial wetland (1) and the third-level artificial wetland (11) are both horizontal subsurface flow artificial wetlands; wetland plants (6) are planted in the first-level artificial wetland (1) and the third-level artificial wetland (11); The second-level ecological pond (7) is planted with ecological pond plants (10) in the form of floating rafts, a non-woven fabric (14) is arranged below the floating raft, and microalgae are enriched on the non-woven fabric (14).

2. The multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus according to claim 1, characterized in that: A first gravel support layer (3) is arranged at the bottom of the first-level artificial wetland (1) and the third-level artificial wetland (11), and a zeolite and volcanic rock mixed matrix (4) is arranged on the first gravel support layer (3); a second gravel support layer (8) is arranged at the bottom of the secondary ecological pond.

3. The multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus according to claim 2, characterized in that: The area ratio of the first-level artificial wetland (1), the second-level ecological pond (7) and the third-level artificial wetland (11) is 1:0.5-1:0.5-1.

4. The multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus according to claim 2, characterized in that: The particle size of the gravel in the first gravel support layer (3) is 2 to 3 cm; the particle sizes of the zeolite and volcanic rock in the zeolite and volcanic rock mixed matrix (4) are both 1 to 2 cm, and the volume ratio of zeolite to volcanic rock is 1:1; the particle size of the gravel in the second gravel support layer (8) is 2 to 3 cm.

5. The multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus according to claim 2, characterized in that: The first-level artificial wetland (1) is provided with a first baffle (2) on the water inlet side and the water outlet side respectively, the first gravel support layer (3) and the zeolite and volcanic stone mixed matrix (4) are located between the first baffles (2) on both sides, the total water inlet (5) is located in the middle of the water inlet side of the first-level artificial wetland (1), and the water outlet of the first-level artificial wetland (1) falls into the second-level ecological pond (7); a second baffle (9) is provided on the water outlet side of the second-level ecological pond (7), and the second-level ecological pond (7) falls into the third-level artificial wetland (11); the third-level artificial wetland (11) is provided with a first baffle (2) on the water inlet side and a third baffle (12) on the water outlet side, the first gravel support layer (3) and the zeolite and volcanic stone mixed matrix (4) are located between the first baffle (2) and the third baffle (12), and the total water outlet (13) is located above the water outlet side of the third-level artificial wetland (11).

6. The multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus according to claim 5, characterized in that: The first baffle (2) is a baffle with holes; the second baffle (9) is a baffle without holes with a hollow bottom, and the height of the hollow is consistent with the height of the second gravel support layer (8); the third baffle (12) is a baffle with holes at the bottom and no holes at the top, and the height of the holes in the third baffle (12) is consistent with the height of the first gravel support layer (3) in the third-level artificial wetland (11).

7. The multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus according to claim 2, characterized in that: In the first-stage artificial wetland (1) and the third-stage artificial wetland (11), the water level is controlled at 0 to 10 cm below the substrate layer.

8. The multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus according to claim 2, characterized in that: The wetland plants (6) are rooted in the mixed matrix (4) of zeolite and volcanic rock. The wetland plants (6) include yellow calamus, iris, reed and canna, and the planting density is 90 to 110 plants / m 2 .

9. The multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus according to claim 2, characterized in that: The roots of the ecological plants are rooted in the water through the non-woven fabric (14). The ecological plants include cattail, iris and calamus, and the planting density is 40 plants / m 2 .

10. A multi-stage artificial wetland-ecological pond system for simultaneous enhanced removal of nitrogen and phosphorus according to any one of claims 1 to 9, characterized in that: In the multi-stage artificial wetland-ecological pond system, the removal rate of ammonia nitrogen can reach 98%, the removal rate of nitrate nitrogen can reach 98.8%, the removal rate of total nitrogen can reach 98.07%, the removal rate of COD can reach 85.02%, and the removal rate of total phosphorus can reach 78%.

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