An ecological wetland system for purifying composite pollution of an incoming river and a running process thereof

Abstract

The application discloses an ecological wetland system for purifying composite pollution of a river entering a reservoir and a running process thereof. The system is provided with a water inlet channel, a first down-flow vertical subsurface flow artificial wetland, an ecological stabilization pond and a second down-flow vertical subsurface flow artificial wetland in a ladder type along a water flow direction. The water outlet of the water inlet channel is provided with a drop weir in communication with the first down-flow vertical subsurface flow artificial wetland. The first down-flow vertical subsurface flow artificial wetland is in communication with the ecological stabilization pond through a first water collecting pipe. The water outlet of the ecological stabilization pond is provided with a rolling dam in communication with the second down-flow vertical subsurface flow artificial wetland. The second down-flow vertical subsurface flow artificial wetland is in communication with a lake reservoir through a second water collecting pipe. The system is combined by artificial wetlands and ecological stabilization pond units with different running modes, different micro-habitat conditions are created, nitrogen, phosphorus and emerging pollutants in the river entering the reservoir are purified in a targeted manner, and the water quality entering the lake reservoir is met.

Description

Technical Field

[0001] This invention belongs to the field of ecological restoration engineering technology, specifically relating to an ecological wetland system for purifying complex pollution in rivers flowing into reservoirs and its operating process. Background Technology

[0002] Many cities and rural areas have already adopted or are gradually adopting surface water bodies such as reservoirs and lakes as their primary water supply sources. The water quality of these bodies is closely related to my country's water supply security. Currently, eutrophication is a major environmental problem facing many reservoirs (lakes), and nitrogen and phosphorus input from rivers flowing into these reservoirs are the main sources of nutrients. Furthermore, with increasing human activities, many emerging pollutants, such as antibiotics and endocrine disruptors, are also entering reservoirs via these rivers, leading to compound pollution. Continued exposure to these pollutants can cause endocrine, developmental, and epigenetic disorders in aquatic organisms and have a direct impact on human health. Therefore, reducing nutrients and emerging pollutants in rivers flowing into reservoirs is a crucial way to control compound pollution in lakes and lakes.

[0003] As a crucial area for information exchange between the reservoir and the land area, the inlet of a lake or reservoir is a hot topic in aquatic ecological restoration. This involves setting up purification systems in unused areas before small and medium-sized rivers flow into the reservoir, treating the incoming river water according to the flow direction. Traditional water purification technologies primarily employ physical and chemical methods, such as sedimentation and artificial aeration. However, due to the unstable water volume and quality of inflowing rivers and the low concentration of pollutants, these measures cannot achieve sustained and stable purification effects. Improper application can even cause serious damage to the ecosystem. In recent years, ecological engineering technologies such as constructed wetlands and stabilization ponds have been widely used due to their low investment, operation, and maintenance costs, good treatment effects, and ability to improve or restore the aquatic ecological environment. However, the micro-habitat conditions of individual constructed wetlands or stabilization ponds are limited, hindering the simultaneous removal of complex pollutants. For example, while constructed wetland fillers have strong chemical adsorption for phosphorus, their degradation efficiency for emerging pollutants is low due to oxygen and light limitations. Stabilization ponds generally have high oxygen content and light transmittance, which is conducive to the biodegradation and photodecomposition of pollutants, but their denitrification effect is weak.

[0004] Selecting fillers with high adsorption capacity for complex pollutants is also an important means to improve the purification effect of ecological wetlands. Fillers can not only trap pollutants but also stimulate the growth of large plants, providing ecological niches for microbial growth and biofilm attachment. In recent years, many novel and highly active media such as zeolite, limestone, granular clay, oyster shells, pumice, ceramics, and maifanite have been widely used. Iron-aluminum sludge from water treatment plants is an unavoidable safety byproduct in drinking water production. Its main components are iron or aluminum oxides or hydroxides, calcium carbonate, clay, organic matter, and activated carbon residue. It not only has high adsorption potential for phosphorus and emerging pollutants but also has a loose structure, which has a positive effect on microbial degradation. For example, Chinese patent CN103880193A discloses a method for treating aquaculture wastewater using a vertical flow constructed wetland based on water treatment plant sludge as filler, achieving a removal rate of over 90% for ammonia nitrogen and total phosphorus. Therefore, using iron-aluminum sludge from water treatment plants in reservoir ecological wetland systems can enhance the purification of complex pollution while also achieving the goal of "treating waste with waste." Summary of the Invention

[0005] To address the difficulty in removing nitrogen, phosphorus, and emerging pollutants from rivers flowing into reservoirs (lakes), this invention provides an ecological wetland system and its operating process for purifying complex pollution in rivers flowing into reservoirs. This system, through targeted design, combines artificial wetlands and ecological stabilization ponds with different operating modes to create differentiated micro-habitat conditions in different units. Combined with highly adsorption-capable wetland fillers, it comprehensively utilizes sedimentation, filtration, adsorption, plant absorption, microbial degradation, and photodecomposition to effectively remove different pollutants in different units, ensuring that the water quality of the rivers flowing into the reservoir meets the requirements for lake entry.

[0006] This invention is achieved through the following technical solution:

[0007] An ecological wetland system for purifying complex pollution in rivers flowing into reservoirs comprises, in a stepped arrangement along the water flow direction, an inlet channel, a first downstream vertical subsurface flow constructed wetland, an ecological stabilization pond, and a second downstream vertical subsurface flow constructed wetland. The outlet of the inlet channel is equipped with a drop weir connected to the first downstream vertical subsurface flow constructed wetland. The first downstream vertical subsurface flow constructed wetland is connected to the ecological stabilization pond via a first collection pipe. The outlet of the ecological stabilization pond is equipped with a weir connected to the second downstream vertical subsurface flow constructed wetland. The second downstream vertical subsurface flow constructed wetland is connected to the reservoir via a second collection pipe.

[0008] The first downflow vertical subsurface flow constructed wetland has the same structural layout as the second downflow vertical subsurface flow constructed wetland, which includes emergent plants, wetland soil matrix, adsorption filler, gravel matrix and water collection pipe from top to bottom;

[0009] The bottom of the ecologically stable pond is a pond soil substrate, planted with submerged plants.

[0010] Preferably, the water level in the inlet channel is more than 10 cm higher than the water level in the first downstream vertical subsurface flow constructed wetland; the water level in the first downstream vertical subsurface flow constructed wetland is more than 10 cm higher than the water level in the ecological stabilization pond; the water level in the ecological stabilization pond is more than 10 cm higher than the water level in the second downstream vertical subsurface flow constructed wetland; and the water level in the second downstream vertical subsurface flow constructed wetland is more than 10 cm higher than the water level in the lake / reservoir.

[0011] Preferably, the hydraulic loading of both the first downflow vertical subsurface flow constructed wetland and the second downflow vertical subsurface flow constructed wetland is 0.20–0.75 m. 3 / (m 2 •d) The hydraulic retention time is 1–4 days; the hydraulic loading of the ecological stabilization pond is 0.10–0.35 m³ / s. 3 / (m 2 ·d), the hydraulic residence time is 2 to 6 days.

[0012] Preferably, a mechanical coarse screen is provided at the inlet of the water inlet channel.

[0013] Preferably, the emergent plants are 2 to 4 species selected from reeds, cattails, sweet flag, water celery, hardy irises, water onions, and canna lilies, with a planting density of 15 to 20 plants / m². 2 The wetland soil substrate is local topsoil; the adsorption filler is waste mud from the water supply plant that has been air-dried and crushed, with a particle size of 1-2 cm; the gravel substrate has a particle size of 3-5 cm; the water collection pipe is a porous PVC pipe with a diameter of DN100 or DN200, laid at a slope of 0.002-0.004; the pond soil substrate is local topsoil; the submerged plants are 2-4 species selected from Elodea nuttallii, Vallisneria natans, Ceratophyllum demersum, Potamogeton crispus, and Hydrilla verticillata, with a planting density of 5-10 plants / m². 2 .

[0014] Preferably, the matrix depth of both the first downflow vertical subsurface flow constructed wetland and the second downflow vertical subsurface flow constructed wetland is 0.8–1.2 m; wherein, the cover thickness of the wetland soil matrix is ​​20–40 cm; the cover thickness of the adsorption filler is 20–40 cm; and the cover thickness of the gravel matrix is ​​10–15 cm.

[0015] Preferably, the water depth of the ecological stabilization pond is 0.8 to 1.0 m, and the thickness of the pond soil matrix is ​​20 to 30 cm.

[0016] An operational process for an ecological wetland system used for the purification of complex pollution in rivers flowing into reservoirs includes the following steps:

[0017] Step 1) The river water flows into the inlet channel. Larger suspended solids in the river water are intercepted by mechanical coarse screens, while smaller particulate matter or pollutants adsorbed by particulate matter are settled through sedimentation. When the water level in the inlet channel rises to the drop weir, the river water overflows into the first downstream vertical subsurface flow constructed wetland because the water level in the inlet channel is higher than that in the first downstream vertical subsurface flow constructed wetland.

[0018] Step 2) After the river water flows into the first downstream vertical subsurface flow constructed wetland, the emergent plants planted on the wetland surface effectively absorb and purify organic matter, total nitrogen, and total phosphorus in the water. At the same time, the organic matter secreted by the plant roots provides a good living environment for the microbial metabolism in the wetland soil matrix, accelerating nitrification and promoting the complete conversion of ammonia nitrogen into nitrate nitrogen. Emergent plants need to be harvested regularly while ensuring the planting density. After the river water infiltrates into the filler layer, phosphorus and emerging pollutants in the water are quickly adsorbed by the adsorption filler, and the microorganisms attached to the adsorption filler also have a degradation effect on easily degradable emerging pollutants. Meanwhile, as oxygen is consumed, the bottom of the filler layer is in an oxygen-deficient state. The denitrifying microorganisms attached to the adsorption filler use themselves or the adsorbed organic matter as a carbon source to remove some nitrate nitrogen through denitrification. The gravel matrix at the bottom supports the wetland filler while also preventing fine silt from clogging the first collection pipe. Due to the water level difference and the slope of the first collection pipe, the river water flows into the ecological stabilization pond through the first collection pipe at the bottom of the first downstream vertical subsurface flow constructed wetland.

[0019] Step 3) After the river water flows into the ecological stabilization pond, the submerged plants in the pond absorb nutrients while performing photosynthesis and releasing oxygen into the water, increasing the dissolved oxygen content in the water, which is beneficial for subsequent microbial degradation. The ecological stabilization pond has high light transmittance, and organic matter and emerging pollutants in the river water that are difficult for microorganisms to degrade will undergo photodecomposition in the pond, transforming into active structures that are easily degraded by subsequent microorganisms. Due to the water level difference, the river water overflows into the second downstream vertical subsurface flow constructed wetland through the spillway of the ecological stabilization pond.

[0020] Step 4) After the river water flows into the second downstream vertical subsurface flow constructed wetland, pollutants that were not completely degraded or removed in the ecological stabilization pond are removed again in the second downstream vertical subsurface flow constructed wetland through a combination of chemical adsorption, biodegradation, and plant absorption, stabilizing the effluent water quality. Furthermore, when the hydraulic load increases and the first downstream vertical subsurface flow constructed wetland and the ecological stabilization pond are unable to meet the purification needs, the second downstream vertical subsurface flow constructed wetland can ensure the stability of the river water quality before it enters the lake or reservoir. Due to the water level difference and the slope of the second collection pipe, the purified river water finally flows into the lake or reservoir through the second collection pipe at the bottom of the second downstream vertical subsurface flow constructed wetland, completing the purification operation.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) The present invention adopts a combination of artificial wetlands and stabilization ponds to form a multi-unit ecological wetland system, which has a high efficiency in purifying composite pollution and the effluent water quality can meet the requirements of lake and reservoir water quality.

[0023] (2) This invention comprehensively utilizes the effects of sedimentation, filtration, adsorption, plant absorption, microbial degradation and photodecomposition, giving full play to the chemical adsorption and biological decomposition of artificial wetlands and the photodecomposition and plant absorption of ecological stabilization ponds, so as to achieve targeted removal of different pollutants such as nitrogen, phosphorus and emerging pollutants.

[0024] (3) By rationally setting the water flow direction and water level difference, the present invention ensures the natural flow of water in the ecological wetland system, with low operating costs and low energy consumption.

[0025] (4) The present invention has strong stability and impact resistance, and meets the needs of complex river environments flowing into reservoirs (lakes).

[0026] (5) This invention uses local soil and waste mud from water supply plants as ecological wetland substrates and fillers, which has low cost and environmental friendliness.

[0027] (6) This invention does not require the addition of chemicals to the river water and will not cause secondary pollution.

[0028] (7) This invention belongs to the ecological engineering restoration method, which effectively improves the ecological environment of the surrounding area by planting aquatic plants. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of an ecological wetland system used for the purification of complex pollution in rivers flowing into reservoirs.

[0030] Figure 2 Schematic diagram of the structure of the first / second downflow vertical subsurface flow constructed wetland;

[0031] Figure 1-2 The components are: 1. Intake channel; 2. First downstream vertical subsurface flow constructed wetland; 3. Ecological stabilization pond; 4. Second downstream vertical subsurface flow constructed wetland; 5. Weir; 6. First collection pipe; 7. Weir; 8. Second collection pipe; 9. Emergent plants; 10. Wetland soil matrix; 11. Adsorbent filler; 12. Gravel matrix; 13. Pond soil matrix; 14. Submerged plants; 15. Mechanical coarse bar screen;

[0032] Figure 3 This is a schematic diagram showing the nitrogen and phosphorus removal rates during the continuous and stable operation of the ecological wetland system in Example 2.

[0033] Figure 4This is a schematic diagram showing the removal rate of typical emerging pollutants during the continuous and stable operation of the ecological wetland system in Example 2. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams only, not actual physical images, and should not be construed as limiting the present invention. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product.

[0035] Example 1

[0036] An ecological wetland system for purifying complex pollution in rivers flowing into reservoirs, such as Figure 1 As shown, the water inlet channel 1, the first downstream vertical subsurface flow artificial wetland 2, the ecological stabilization pond 3, and the second downstream vertical subsurface flow artificial wetland 4 are arranged in a stepped manner along the water flow direction.

[0037] like Figure 1 As shown, the outlet of the inlet channel 1 is equipped with a drop weir 5, which is connected to the first downstream vertical subsurface flow artificial wetland 2; the first downstream vertical subsurface flow artificial wetland 2 is connected to the ecological stabilization pond 3 through the first water collection pipe 6; the outlet of the ecological stabilization pond 3 is equipped with a spillway 7, which is connected to the second downstream vertical subsurface flow artificial wetland 4; the second downstream vertical subsurface flow artificial wetland 4 is connected to the lake and reservoir through the second water collection pipe 8.

[0038] like Figure 2 As shown, the first downflow vertical subsurface flow constructed wetland 2 and the second downflow vertical subsurface flow constructed wetland 4 have the same structural layout, consisting of emergent plants 9, wetland soil substrate 10, adsorption filler 11, gravel substrate 12, and water collection pipe from top to bottom. The substrate depth of both the first downflow vertical subsurface flow constructed wetland 2 and the second downflow vertical subsurface flow constructed wetland 4 is 0.8 to 1.2 m.

[0039] The emergent plants mentioned are 2 to 4 species selected from reeds, cattails, sweet flag, water celery, hardy irises, water onions, and canna lilies, with a planting density of 15 to 20 plants / m². 2 And regularly harvest the emergent plants 9.

[0040] The wetland soil substrate 10 is the local topsoil for planting, with a covering thickness of 20-40cm, to ensure the growth of emergent plants.

[0041] The adsorption packing material 11 is waste mud from the water supply plant that has been air-dried and crushed, with a particle size of 1-2 cm and a coverage thickness of 20-40 cm. It can adsorb and remove phosphorus and emerging pollutants in the river water flowing into the reservoir, and is also conducive to microbial denitrification and degradation of emerging pollutants.

[0042] The gravel matrix 12 has a particle size of 3-5 cm and a covering thickness of 10-15 cm to ensure the permeability of the constructed wetland.

[0043] The water collection pipe is a porous PVC pipe with a diameter of DN100 or DN200, and the laying slope is 0.002 to 0.004 to ensure the natural flow of river water between different units.

[0044] like Figure 1 As shown, the bottom of the ecological stabilization pond 3 is a pond soil substrate 13, on which submerged plants 14 are planted. The water depth of the ecological stabilization pond 3 is 0.8-1.0m, which ensures water transparency and is conducive to the growth of submerged plants and the photodecomposition of emerging pollutants.

[0045] The submerged plants 14 are 2 to 4 species selected from Elodea, Vallisneria, Ceratophyllum demersum, Potamogeton crispus, and Hydrilla verticillata, with a planting density of 5 to 10 plants / m². 2 This can both increase the dissolved oxygen content in the water and absorb nitrogen and phosphorus nutrients in the water, ensuring the treatment effect of Pond 3 in maintaining ecological stability.

[0046] The pond soil substrate 13 is local topsoil with a thickness of 20-30cm, which stabilizes the growth of submerged plants 14 in the pond.

[0047] In a preferred embodiment, the water level of the inlet channel 1 is at least 10 cm higher than the water level of the first downstream vertical subsurface flow constructed wetland 2; the water level of the first downstream vertical subsurface flow constructed wetland 2 is at least 10 cm higher than the water level of the ecological stabilization pond 3; and the water level of the ecological stabilization pond 3 is at least 10 cm higher than the water level of the second downstream vertical subsurface flow constructed wetland 4. These water level differences ensure the natural flow of river water within the ecological wetland system. The water level of the second downstream vertical subsurface flow constructed wetland 4 is at least 10 cm higher than the water level of the lake / reservoir.

[0048] In a preferred embodiment, the hydraulic loading of both the first downflow vertical subsurface flow constructed wetland 2 and the second downflow vertical subsurface flow constructed wetland 4 is 0.20–0.75 m. 3 / (m 2 •d) The hydraulic retention time is 1–4 days; the hydraulic loading of the ecological stabilization pond 3 is 0.10–0.35 m³ / s. 3 / (m 2 •d) The hydraulic retention time is 2 to 6 days; thus, the ecological wetland system has strong stability and impact resistance.

[0049] In a preferred embodiment, a mechanical coarse screen 15 is provided at the inlet of the water inlet channel 1.

[0050] The above-mentioned operational processes of ecological wetland systems used for the purification of complex pollution in rivers flowing into reservoirs, such as... Figure 1As shown, the specific steps are as follows:

[0051] (1) When river water flows into the reservoir (lake), larger suspended solids in the river water are intercepted by the mechanical coarse screen 15, while smaller particulate matter or pollutants adsorbed by particulate matter will settle through sedimentation, preventing particulate pollutants from entering the constructed wetland and causing blockage. When the water level in the inlet channel 1 rises to the drop weir 5, since the water level in the inlet channel 1 is more than 10 cm higher than that in the first downstream vertical subsurface flow constructed wetland 2, the river water overflows into the first downstream vertical subsurface flow constructed wetland 2 through the drop weir 5. While ensuring uniform water distribution, the inlet channel 1 can also increase the dissolved oxygen content in the river water, which is beneficial to the microbial degradation in the first downstream vertical subsurface flow constructed wetland 2.

[0052] (2) After the river water flows into the first downstream vertical subsurface flow artificial wetland 2, the emergent plants 9 planted on the surface of the wetland not only play a good role in absorbing and purifying organic matter, total nitrogen, and total phosphorus in the water, but also provide a good living environment for the microbial metabolism in the wetland soil matrix through the organic matter secreted by the plant roots, accelerating nitrification and promoting the complete conversion of ammonia nitrogen into nitrate nitrogen. The emergent plants need to be harvested regularly while ensuring the planting density. After the river water infiltrates into the filler layer, phosphorus and emerging pollutants in the water are quickly adsorbed by the adsorption filler 11 (waste sludge from the water supply plant), and the microorganisms attached to the waste sludge from the water supply plant also have a degradation effect on easily degradable emerging pollutants. At the same time, as oxygen is consumed, the bottom of the filler layer is in an oxygen-deficient state. The denitrifying microorganisms attached to the waste sludge from the water supply plant use themselves or the adsorbed organic matter as a carbon source to remove part of the nitrate nitrogen through denitrification. The gravel matrix 12 at the bottom supports the wetland filler while also preventing fine silt from clogging the first water collection pipe 6. Due to the water level difference (more than 10cm) and the slope of the first collection pipe 6 (0.002~0.004), the river water flows into the ecological stabilization pond 3 through the first collection pipe 6 at the bottom of the first downstream vertical subsurface flow artificial wetland 2.

[0053] (3) After the river water flows into the ecological stabilization pond 3, the submerged plants 14 in the pond absorb nutrients while performing photosynthesis and releasing oxygen into the water, increasing the dissolved oxygen content in the water, which is beneficial to subsequent microbial degradation. The water in the ecological stabilization pond 3 has high light transmittance, and organic matter and emerging pollutants in the river water that are difficult for microorganisms to degrade will undergo photodecomposition in the pond, transforming into active structures that are easily degraded by subsequent microorganisms; due to the water level difference (more than 10cm), the river water overflows into the second downstream vertical subsurface flow artificial wetland 4 through the spillway 7 of the ecological stabilization pond 3.

[0054] (4) After the river water flows into the second downstream vertical subsurface flow constructed wetland 4, pollutants that were not completely degraded or removed in the ecological stabilization pond 3 are removed again in the second downstream vertical subsurface flow constructed wetland 4 through a combination of chemical adsorption, biodegradation, and plant absorption, thus stabilizing the effluent water quality. Furthermore, when the hydraulic load increases and the first downstream vertical subsurface flow constructed wetland 2 and the ecological stabilization pond 3 are insufficient to meet the purification requirements, the second downstream vertical subsurface flow constructed wetland 4 can ensure the stability of the river water quality before it enters the lake or reservoir. Due to the water level difference (above 10 cm) and the slope of the second collection pipe 8 (0.002–0.004), the purified river water eventually flows into the lake or reservoir through the second collection pipe 8 at the bottom of the second downstream vertical subsurface flow constructed wetland 4, completing the purification operation.

[0055] Example 2

[0056] This embodiment utilizes the ecological wetland system and operation process described in Embodiment 1 to achieve the purification of complex pollution in the river water flowing into a reservoir, as detailed below:

[0057] The inflow river to a certain reservoir has a flow rate of 24 m³ / h. 3 / d, the water quality indicators are: ammonia nitrogen concentration 0.5mg / L, total nitrogen concentration 3.89mg / L, total phosphorus concentration 0.19mg / L, sulfonamide antibiotic concentration 327ng / L, and endocrine disruptors (bisphenols and hormones) concentration 114ng / L.

[0058] (1) The river water enters the inlet channel. The inlet channel is 5m long, 0.9m deep, 2m wide at the bottom, and 4m wide at the opening. A mechanical coarse screen is installed at the inlet port of the inlet channel, and the top width of the drop weir is 10cm.

[0059] (2) The river water overflows from the intake channel into the first downstream vertical subsurface flow artificial wetland, with a wetland area of ​​150m². 2 The wetland water level is 10cm lower than the inlet channel water level, and the hydraulic load is 0.35m. 3 / (m 2 •d), hydraulic retention time 2.2 days. Reeds and canna lilies were planted on the wetland surface at a density of 15 plants / m². 2 The wetland substrate is 80cm deep, consisting of wetland soil substrate, absorbent filler, gravel substrate, and the first collection pipe from top to bottom. The wetland soil substrate is local topsoil, with a cover thickness of 30cm. The absorbent filler is waste sludge from a water supply plant, which, after being naturally air-dried for two months, is broken into particles with a diameter of approximately 1cm, with a cover thickness of 30cm. The gravel substrate contains gravel with a particle size of 3cm, with a cover thickness of 10cm. The first collection pipe is a DN100 porous PVC pipe with a pore size of 3cm, laid at a slope of 0.002.

[0060] (3) The river water flowing into the reservoir enters the ecological stabilization pond from the first collection pipe of the first downstream vertical subsurface flow constructed wetland. The stabilization pond has an area of ​​100m². 2 The water depth is 70cm, and the water level is 10cm lower than the water level of the first downstream vertical subsurface flow constructed wetland. The hydraulic load is 0.24m. 3 / (m 2 •d), hydraulic retention time 2.9 days. The bottom of the stabilization pond is composed of pond soil substrate with a thickness of 20cm. Vallisneria natans and Ceratophyllum demersum are planted in the pond at a planting density of 8 plants / m². 2 The outlet of the ecological stabilization pond is equipped with a weir composed of irregular large stones, 15cm high and with a slope of 25°.

[0061] (4) The river water flowing into the reservoir overflows from the weir of the ecological stabilization pond into the second downstream vertical subsurface flow artificial wetland, with a wetland area of ​​150m². 2 The wetland water level is 10cm lower than the ecological stabilization pond water level, with a hydraulic load of 0.35m. 3 / (m 2 •d), hydraulic retention time 2.2 days. Reeds and canna lilies were planted on the wetland surface at a density of 15 plants / m². 2 The wetland substrate is 80cm deep, consisting of wetland soil substrate, absorbent filler, gravel substrate, and a second collection pipe from top to bottom. The wetland soil substrate is local topsoil, with a cover thickness of 30cm. The absorbent filler is waste sludge from a water supply plant, naturally air-dried for two months, then crushed into particles with a diameter of approximately 1cm, with a cover thickness of 30cm. The gravel substrate contains gravel with a particle size of 3cm, with a cover thickness of 10cm. The second collection pipe is a DN100 porous PVC pipe with a pore size of 3cm and a laying slope of 0.002. The purified river water flows into the reservoir through the second collection pipe.

[0062] (5) Experimental Results

[0063] During the period of continuous and stable operation of this ecological wetland system, its purification effect on ammonia nitrogen, total nitrogen, and total phosphorus in the inflow river is as follows: Figure 3 As shown, the average concentration of ammonia nitrogen in the wetland effluent was 0.14 mg / L, with an average removal rate of 72%, meeting the Class III standard of the "Surface Water Environmental Quality Standard" (1.0 mg / L). The average concentration of total nitrogen in the effluent was 0.95 mg / L, with an average removal rate of 76%, meeting the Class III standard of the "Surface Water Environmental Quality Standard" (1.0 mg / L). The total phosphorus concentration in the effluent was relatively stable, with an average concentration below 0.02 mg / L and an average removal rate of 92%, meeting the Class III standard of the "Surface Water Environmental Quality Standard" for lakes and reservoirs (0.05 mg / L).

[0064] The ecological wetland system effectively purifies antibiotics (sulfonamides) and endocrine disruptors (bisphenols and hormones) from the inflowing river, as shown in the following figures. Figure 4As shown, the average concentration of antibiotics in the effluent was 88 ng / L, with a removal rate of 73%; the average concentration of endocrine disruptors in the effluent was 14 ng / L, with a removal rate of 86%.

[0065] Pollutant concentration calculations showed that the first downflow vertical subsurface flow constructed wetland contributed 95%, 43%, 87%, and 46% to ammonia nitrogen, total nitrogen, total phosphorus, and emerging pollutants, respectively; the ecological stabilization pond achieved removal rates of 5%, 26%, 5%, and 39% for ammonia nitrogen, total nitrogen, total phosphorus, and emerging pollutants, respectively; and the second downflow vertical subsurface flow constructed wetland contributed 0%, 31%, 8%, and 15% to ammonia nitrogen, total nitrogen, total phosphorus, and emerging pollutants, respectively. This indicates that the first downflow vertical subsurface flow constructed wetland dominated the purification of compound pollutants, the ecological stabilization pond enhanced the removal of total nitrogen and emerging pollutants, while the second downflow vertical subsurface flow constructed wetland further reduced total nitrogen and emerging pollutants.

[0066] In summary, this invention, through the combination of constructed wetlands and stabilization ponds and the design of its operation mode, achieves a rational allocation of oxygen, light, and carbon source environments. Relying on synergistic mechanisms such as chemical adsorption, photodegradation, biodegradation, and plant absorption, it achieves the goal of denitrification, phosphorus removal, and degradation of emerging pollutants in river water flowing into reservoirs (lakes). The ecological wetland system proposed in this invention can be used for the purification of complex pollution in rivers flowing into reservoirs (lakes), effectively removing nitrogen, phosphorus, and emerging pollutants from river water to meet the water quality requirements of reservoirs and lakes. Furthermore, this invention has advantages such as low cost, low energy consumption, high efficiency, and environmental friendliness.

Claims

1. An ecological wetland system for purifying complex pollution in rivers flowing into reservoirs, characterized in that, The system is arranged in a stepped manner along the water flow direction, comprising an inlet channel, a first downstream vertical subsurface flow constructed wetland, an ecological stabilization pond, and a second downstream vertical subsurface flow constructed wetland. The outlet of the inlet channel is equipped with a drop weir connected to the first downstream vertical subsurface flow constructed wetland. The first downstream vertical subsurface flow constructed wetland is connected to the ecological stabilization pond via a first collection pipe. The outlet of the ecological stabilization pond is equipped with a weir connected to the second downstream vertical subsurface flow constructed wetland. The second downstream vertical subsurface flow constructed wetland is connected to a lake / reservoir via a second collection pipe. The first downflow vertical subsurface flow constructed wetland has the same structural layout as the second downflow vertical subsurface flow constructed wetland, which includes emergent plants, wetland soil matrix, adsorption filler, gravel matrix and water collection pipe from top to bottom; the adsorption filler is waste mud from water supply plant after air drying and crushing, with a particle size of 1~2 cm. The bottom of the ecological stabilization pond is a pond soil matrix planted with submerged plants; the water depth of the ecological stabilization pond is 0.8~1.0 m; the ecological stabilization pond is used to cause emerging pollutants in the river water that are difficult to be degraded by microorganisms to undergo photodecomposition and be transformed into easily degradable structures, and the submerged plants release oxygen into the water through photosynthesis.

2. An ecological wetland system for purifying complex pollution in rivers flowing into reservoirs, as described in claim 1, is characterized in that... The water level in the inlet channel is more than 10 cm higher than the water level in the first downstream vertical subsurface flow constructed wetland; the water level in the first downstream vertical subsurface flow constructed wetland is more than 10 cm higher than the water level in the ecological stabilization pond; the water level in the ecological stabilization pond is more than 10 cm higher than the water level in the second downstream vertical subsurface flow constructed wetland; and the water level in the second downstream vertical subsurface flow constructed wetland is more than 10 cm higher than the water level in the lake / reservoir.

3. An ecological wetland system for purifying complex pollution in rivers flowing into reservoirs, as described in claim 1, is characterized in that... The hydraulic loading of both the first and second downflow vertical subsurface flow constructed wetlands is 0.20~0.75 m. 3 / (m 2 •d) The hydraulic retention time is 1-4 days; the hydraulic loading of the ecological stabilization pond is 0.10-0.35 m³. 3 / (m 2 ·d), the hydraulic residence time is 2 to 6 days.

4. An ecological wetland system for purifying complex pollution in rivers flowing into reservoirs, as described in claim 1, is characterized in that... A mechanical coarse screen is installed at the inlet of the water intake channel.

5. An ecological wetland system for purifying complex pollution in rivers flowing into reservoirs, as described in claim 1, characterized in that, The emergent plants are 2-4 species selected from reeds, cattails, sweet flag, water celery, hardy irises, water onions, and canna lilies, with a planting density of 15-20 plants / m². 2 The wetland soil substrate is the local topsoil from which crops are planted; the gravel substrate has a particle size of 3-5 cm; the water collection pipe is a porous PVC pipe with a diameter of DN100 or DN200, laid at a slope of 0.002-0.004; the pond soil substrate is the local topsoil from which crops are planted; the submerged plants are 2-4 species selected from Elodea nuttallii, Vallisneria natans, Ceratophyllum demersum, Potamogeton crispus, and Hydrilla verticillata, with a planting density of 5-10 plants / m². 2 .

6. An ecological wetland system for purifying complex pollution in rivers flowing into reservoirs, as described in claim 1, is characterized in that... The matrix depth of both the first downflow vertical subsurface flow constructed wetland and the second downflow vertical subsurface flow constructed wetland is 0.8~1.2 m; wherein, the cover thickness of the wetland soil matrix is ​​20~40 cm; the cover thickness of the adsorption filler is 20~40 cm; and the cover thickness of the gravel matrix is ​​10~15 cm.

7. An ecological wetland system for purifying complex pollution in rivers flowing into reservoirs, as described in claim 1, is characterized in that... The thickness of the soil matrix in the pond is 20-30 cm.

8. The operating process of an ecological wetland system for purifying complex pollution in rivers flowing into reservoirs, as described in any one of claims 1-7, is characterized in that... Includes the following steps: Step 1) The river water flows into the inlet channel. Larger suspended solids in the river water are intercepted by mechanical coarse screens, while smaller particulate matter or pollutants adsorbed by particulate matter are settled through sedimentation. When the water level in the inlet channel rises to the drop weir, the river water overflows into the first downstream vertical subsurface flow constructed wetland because the water level in the inlet channel is higher than that in the first downstream vertical subsurface flow constructed wetland. Step 2) After the river water flows into the first downstream vertical subsurface flow constructed wetland, the emergent plants planted on the wetland surface effectively absorb and purify organic matter, total nitrogen, and total phosphorus in the water. At the same time, the organic matter secreted by the plant roots provides a good living environment for the microbial metabolism in the wetland soil matrix, accelerating nitrification and promoting the complete conversion of ammonia nitrogen into nitrate nitrogen. Emergent plants need to be harvested regularly while ensuring the planting density. After the river water infiltrates into the filler layer, phosphorus and emerging pollutants in the water are quickly adsorbed by the adsorption filler, and the microorganisms attached to the adsorption filler also have a degradation effect on easily degradable emerging pollutants. Meanwhile, as oxygen is consumed, the bottom of the filler layer is in an oxygen-deficient state. The denitrifying microorganisms attached to the adsorption filler use themselves or the adsorbed organic matter as a carbon source to remove some nitrate nitrogen through denitrification. The gravel matrix at the bottom supports the wetland filler while also preventing fine silt from clogging the first collection pipe. Due to the water level difference and the slope of the first collection pipe, the river water flows into the ecological stabilization pond through the first collection pipe at the bottom of the first downstream vertical subsurface flow constructed wetland. Step 3) After the river water flows into the ecological stabilization pond, the submerged plants in the pond absorb nutrients while performing photosynthesis and releasing oxygen into the water, increasing the dissolved oxygen content in the water, which is beneficial for subsequent microbial degradation. The ecological stabilization pond has high light transmittance, and organic matter and emerging pollutants in the river water that are difficult for microorganisms to degrade will undergo photodecomposition in the pond, transforming into active structures that are easily degraded by subsequent microorganisms. Due to the water level difference, the river water overflows into the second downstream vertical subsurface flow artificial wetland through the spillway of the ecological stabilization pond. Step 4) After the river water flows into the second downstream vertical subsurface flow constructed wetland, pollutants that were not completely degraded or removed in the ecological stabilization pond are removed again in the second downstream vertical subsurface flow constructed wetland through a combination of chemical adsorption, biodegradation, and plant absorption, stabilizing the effluent water quality. Furthermore, when the hydraulic load increases and the first downstream vertical subsurface flow constructed wetland and the ecological stabilization pond are unable to meet the purification needs, the second downstream vertical subsurface flow constructed wetland can ensure the stability of the river water quality before it enters the lake or reservoir. Due to the water level difference and the slope of the second collection pipe, the purified river water finally flows into the lake or reservoir through the second collection pipe at the bottom of the second downstream vertical subsurface flow constructed wetland, completing the purification operation.

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