Rotating tower type multistage tidal flow artificial wetland system and sewage treatment method

Abstract

The invention discloses a rotating tower type multi-stage tidal flow constructed wetland system and a sewage treatment method, the rotating tower type multi-stage tidal flow constructed wetland system comprises a central purification wetland, a plurality of layers of annular wetlands are sequentially installed outside the central purification wetland from high to low in a surrounding mode, each layer of annular wetland is composed of a plurality of fan-shaped purification units, a water inlet is formed in the upper end of the central purification wetland, a first rotary drainer is mounted at the top of the first water collection channel, a second rotary drainer is mounted at the top of the second water collection channel, and the first rotary drainer is used for draining water to the tops of the adjacent annular wetlands in a rotary falling manner; the second rotary drainer is used for rotatably draining water to the top of the annular wetland on the outer layer in a waterfall manner. The central purification wetland surrounds the multiple layers of coaxial annular wetlands outside the central purification wetland, and the first rotary drainer and the second rotary drainer are used for draining water in a rotary falling manner, so that a tidal flow effect is formed, and efficient denitrification of sewage is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a rotating tower type multi-stage tidal flow artificial wetland system and a sewage treatment method. Background Art

[0002] Nitrogen pollution is the main cause of eutrophication of water bodies, and the removal of ammonia nitrogen, nitrate nitrogen and nitrite nitrogen in sewage treatment has become an important issue of environmental protection. Traditional sewage treatment processes mostly rely on the alternation of aerobic and anaerobic processes in physical, chemical and biological processes to achieve denitrification, especially nitrification and denitrification. However, traditional processes have problems such as high operating costs, complex structures, large space occupation, and uneven distribution of dissolved oxygen, which limit the denitrification efficiency. Artificial wetlands have become an emerging technology in the field of sewage treatment due to their advantages such as low energy consumption, environmental protection, and simple operation and maintenance. Tidal flow artificial wetlands simulate natural tidal phenomena, provide alternating aerobic and anoxic environments, and enhance the efficiency of nitrification-denitrification, but there is still room for improvement in the deep denitrification of sewage. Therefore, the present invention proposes a rotating tower multi-stage tidal flow artificial wetland system and a sewage treatment method. Summary of the invention

[0003] In order to solve the current technical problems, the main purpose of the present invention is to provide a rotating tower multi-stage tidal flow artificial wetland system and a sewage treatment method, which can achieve efficient denitrification of sewage through coaxial nested design and tidal flow effect.

[0004] In order to overcome the problems existing in the prior art, the technical solution adopted by the present invention is: a rotating tower multi-stage tidal flow artificial wetland system, including a central purification wetland, the outside of the central purification wetland is surrounded by multiple layers of annular wetlands from high to low in sequence, and the annular wetlands of each layer are respectively composed of multiple fan-shaped purification units, a first water collection channel is arranged between the central purification wetland and the adjacent annular wetland, the bottom of the first water collection channel is connected with the bottom of the central purification wetland, each of the fan-shaped purification units corresponding to the inner side between adjacent annular wetlands is respectively provided with a second water collection channel, the bottom of the second water collection channel is connected with the bottom of the corresponding fan-shaped purification unit on the inner side, a drainage channel is arranged on the outer side of the outermost annular wetland, and a drainage port is arranged on the outer side of the upper end of the drainage channel; A water inlet is provided at the upper end of the central purification wetland, a first rotary drainer is installed at the top of the first water collection channel, and a second rotary drainer is installed at the top of the second water collection channel. The first rotary drainer is used for rotary cascading drainage to the top of the adjacent annular wetland, and the second rotary drainer is used for rotary cascading drainage to the top of the outer annular wetland.

[0005] The central purification wetland comprises a central container, a water inlet is arranged at the top of the central container, a first water collection channel is arranged on the outer wall of the central container, and the central container is filled with a first nitrification treatment matrix.

[0006] The first nitrification treatment matrix is ​​provided with three layers, which are a porous light matrix, an aggregate matrix and a denitrification matrix from top to bottom.

[0007] The first rotary drainer includes a rotating groove ring, a first gear ring and a first motor. A support ring is fixedly installed at the upper inner hole of the rotating groove ring. A limit ring is fixedly installed on the top of the central purification wetland. The support ring is movably mounted on the outside of the limit ring. The inner hole of the support ring is installed with a first gear ring. The first motor is installed on the top of the central purification wetland. The output shaft of the first motor is installed with a first gear, and the first gear ring is meshed with the first gear for transmission. A first water outlet is arranged on the outside of the first water collecting channel, and the first water outlet extends into the rotating groove ring. At least one first water outlet pipe is installed on the lower side of the rotating groove ring.

[0008] The fan-shaped purification unit located in the inner layer includes a first fan-shaped container, the top of the first fan-shaped container is open, the outer wall of the first fan-shaped container is provided with a second water collection channel, and the first fan-shaped container is filled with a second nitrification treatment matrix.

[0009] The second nitrification treatment matrix is ​​provided with two layers, which are a porous matrix and a denitrification enhancement matrix from top to bottom.

[0010] The second rotary drainer includes a first rotating ring, a second gear ring and a second motor. A second water outlet is arranged on the second water collecting channel. A bearing ring is fixedly installed on the outer wall of the annular wetland below the second water outlet. A movable set on the bearing ring supports a rotating ring. The first rotating ring is installed on the rotating ring. A second gear ring is also installed on the rotating ring. The second motor is installed on the outer wall of the annular wetland. A second gear is installed on the output shaft of the second motor. The second gear ring is meshed with the second gear for transmission. At least one second water outlet pipe is installed on the lower side of the first rotating ring.

[0011] The second rotating drainer also includes a second rotating ring, which is located above the first rotating ring. A drain pipe is connected to the bottom of the second rotating ring, which passes through the first rotating ring and is fixedly connected to the first rotating ring. A third water outlet is also provided on the second water collecting channel above the second water outlet. The third water outlet is used to divert water into the second rotating ring. A first control valve and a second control valve are respectively installed on the second water outlet and the third water outlet.

[0012] The fan-shaped purification unit located at the outermost layer includes a second fan-shaped container, the top of the second fan-shaped container is open, the drainage channel is arranged on the outer wall of the second fan-shaped container, and the second fan-shaped container is filled with a functional matrix for supplying organic or inorganic electrons.

[0013] A sewage treatment method adopts the rotating tower multi-stage tidal flow artificial wetland system, and the treatment method comprises the following steps: S1, sewage enters from the water inlet of the central purification wetland; S2, after the sewage undergoes nitrification reaction in an aerobic environment from top to bottom, it enters the first water collection channel from the bottom; S3, the water in the first water collection channel flows from bottom to top into the first rotary drainer, and then is discharged to the outer adjacent annular wetland surface in the form of a rotary waterfall; S4: In this layer of circular wetland, water goes from top to bottom through nitrification in anoxic environment and then enters the second water collection channel from the bottom; S5. After the water in the second water collection channel flows from bottom to top into the second rotary drainer, it is discharged to the outer adjacent annular wetland surface in the form of a rotary waterfall; S6. Finally, the water is discharged to the outermost annular wetland surface in the form of a rotating waterfall. After nitrification treatment in an anaerobic environment from top to bottom, the water enters the drainage channel from the bottom and is finally discharged from the drain outlet.

[0014] The present invention has the following beneficial effects: 1. The present invention realizes efficient denitrification of sewage by forming a tidal flow effect through a multi-layer coaxial annular wetland surrounding the central purification wetland and draining water in the form of a rotating waterfall through a first rotary drainer and a second rotary drainer. The nitrification and denitrification process of sewage in the multi-layer wetland can be cyclically carried out, and deep denitrification is finally achieved.

[0015] 2. The present invention controls the water level of the inner annular wetland by controlling the opening and closing of the first control valve and the second control valve, thereby achieving the purpose of breathing of the inner annular wetland, forming intermittent drainage, and strengthening the tidal flow effect.

[0016] 3. The present invention realizes a tidal flow effect through a rotating overflow weir, and the sewage in each layer of the wetland can undergo multiple nitrification and denitrification processes, effectively removing ammonia nitrogen and total nitrogen.

[0017] 4. The cylinder nesting design of the present invention improves space utilization and is suitable for sewage treatment scenarios in cities and places with limited space.

[0018] 5. In the present invention, when sewage falls from the upper layer to the lower layer through the first rotary drainer and the second rotary drainer, dissolved oxygen is restored to provide oxygen support for the next stage of nitrification process.

[0019] 6. The first rotary drainer and the second rotary drainer in the present invention can be adjusted by an automatic control system to ensure uniform distribution of water flow and periodic tidal flow, thereby enhancing the stability and efficiency of sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a schematic diagram of the cross-sectional structure of the present invention.

[0022] Figure 2 It is a schematic diagram of the top structure of the present invention.

[0023] Figure 3 It is a schematic cross-sectional structural diagram of the first rotary drainer of the present invention.

[0024] Figure 4 It is a schematic cross-sectional structural diagram of the second rotary drainer of the present invention.

[0025] Figure 5 It is a schematic diagram of the three-dimensional structure of the second rotary drainer of the invention.

[0026] Reference numerals: Central purification wetland 100, light matrix 101, aggregate matrix 102, denitrification matrix 103; Central container 110, water inlet 111, limiting ring 112; A first water collecting channel 120, a first water outlet 121; A first rotary drainer 130, a rotary groove ring 131, a first water outlet 132, a support ring 133, a first gear ring 134, a first motor 135, and a first gear 136; The second annular wetland 200, porous matrix 201, denitrification enhancement matrix 202, first fan-shaped container 210, second water collection channel 220, second water outlet 221, third water outlet 222, first control valve 223, second control valve 224, and bearing ring 225; A second rotary drainer 230, a first rotary ring 231, a second rotary ring 232, a drain pipe 233, a second water outlet 234, a rotating ring 235, a second gear ring 236, a second motor 237, a second gear 238, and a partition 239; The third layer of the annular wetland 300 , the functional matrix 301 , the second fan-shaped container 310 , the drainage channel 320 , and the drainage outlet 321 .

[0027] Wetland plants 400. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Embodiment 1: See also Figure 1-2 The present invention provides a rotating tower multi-stage tidal flow artificial wetland system, including a central purification wetland 100, wherein multiple layers of annular wetlands are sequentially installed around the outside of the central purification wetland 100 from high to low, wherein the annular wetlands of each layer are respectively composed of multiple fan-shaped purification units, wherein a first water collection channel 120 is arranged between the central purification wetland 100 and adjacent annular wetlands, wherein the bottom of the first water collection channel 120 is connected to the bottom of the central purification wetland 100, wherein each of the fan-shaped purification units corresponding to the inner side between adjacent annular wetlands is respectively provided with a second water collection channel 220, wherein the bottom of the second water collection channel 220 is connected to the bottom of the corresponding fan-shaped purification unit on the inner side, wherein a drainage channel 320 is arranged on the outer side of the outermost annular wetland, wherein a drainage port 321 is arranged on the outer side of the upper end of the drainage channel 320; A water inlet 111 is provided at the upper end of the central purification wetland 100, a first rotary drainer 130 is installed at the top of the first water collecting channel 120, and a second rotary drainer 230 is installed at the top of the second water collecting channel 220. The first rotary drainer 130 is used to drain water by rotary cascading to the top of the adjacent annular wetland, and the second rotary drainer 230 is used to drain water by rotary cascading to the top of the outer annular wetland.

[0030] The central purification wetland 100 is surrounded by multiple layers of coaxial annular wetlands outside the central purification wetland 100, and the first rotary drainer 130 and the second rotary drainer 230 drain water in the form of a rotary waterfall to form a tidal flow effect, thereby achieving efficient denitrification of sewage. The nitrification and denitrification process of sewage in the multiple layers of wetlands can be cyclically carried out, and deep denitrification is finally achieved.

[0031] See also Figure 1 , 2 The central purification wetland 100 includes a central container 110 , a water inlet 111 is arranged at the top of the central container 110 , a first water collection channel 120 is arranged on the outer wall of the central container 110 , and the central container 110 is filled with a first nitrification treatment matrix.

[0032] Specifically, the first nitrification treatment substrate is provided with three layers, which are a porous light substrate 101, an aggregate substrate 102 and a denitrification substrate 103 from top to bottom.

[0033] In this embodiment, the lightweight substrate 101 is made of expanded perlite or lightweight ceramsite to promote nitrification reaction in an aerobic environment, ensuring sufficient dissolved oxygen in the water body, which is suitable for the growth and activity of nitrifying bacteria.

[0034] Aggregate-based matrix 102 is composed of crushed stone or volcanic rock, which provides moderate water flow resistance and supports alternating aerobic and anoxic microenvironments.

[0035] The denitrifying substrate 103 is selected from organic matter containing organic carbon or capable of enhancing denitrification, such as sawdust, straw or wood chips, to promote denitrification reaction and convert nitrate into nitrogen gas.

[0036] In this embodiment, see Figure 3 The first rotary drainer 130 includes a rotary groove ring 131, a first gear ring 134 and a first motor 135. A support ring 133 is fixedly installed at the inner hole of the upper side of the rotary groove ring 131. A limit ring 112 is fixedly installed on the top of the central purification wetland 100. The support ring 133 is movably mounted on the outer side of the limit ring 112. The inner hole of the support ring 133 is installed with a first gear ring 134. The first motor 135 is installed on the top of the central purification wetland 100. The output shaft of the first motor 135 is installed with a first gear 136. The first gear ring 134 is meshed with the first gear 136 for transmission. The first water outlet 121 is arranged on the outer side of the first water collecting channel 120. The first water outlet 121 extends into the rotary groove ring 131. At least one first water outlet pipe 132 is installed on the lower side of the rotary groove ring 131. Through the above structure, the rotary drainage of the first rotary drainer 130 is realized.

[0037] When the first motor 135 rotates, the first gear 136 is driven to rotate, and the first gear 136 drives the first gear ring 134 to rotate. Since the first gear ring 134 is fixedly connected to the rotating groove ring 131, the rotating groove ring 131 will rotate accordingly. When the water in the first water collecting channel 120 enters the rotating groove ring 131, it is discharged through the first water outlet 132.

[0038] See also Figure 1 , 2 The fan-shaped purification unit located in the inner layer includes a first fan-shaped container 210, the top of the first fan-shaped container 210 is open, the outer wall of the first fan-shaped container 210 is provided with a second water collection channel 220, and the first fan-shaped container 210 is filled with a second nitrification treatment matrix.

[0039] In this embodiment, the second nitrification treatment matrix is ​​provided with two layers, which are a porous matrix 201 and a denitrification enhancement matrix 202 from top to bottom.

[0040] Specifically, the porous matrix 201 is made of ceramsite or coarse sand to enhance the nitrification reaction and provide a stable matrix for plant planting. The porous structure is conducive to root growth and air entry.

[0041] The denitrification enhancement substrate 202 is made of wood chips, straw or rice husks, which can provide electron donors in an anaerobic environment to promote the denitrification process.

[0042] In this embodiment, see Figure 4 The second rotary drainer 230 includes a first rotating ring 231, a second gear ring 236 and a second motor 237. The second water collection channel 220 is provided with a second water outlet 221. A bearing ring 225 is fixedly installed on the outer wall of the annular wetland below the second water outlet 221. A rotating ring 235 is movably supported on the bearing ring 225. The first rotating ring 231 is installed on the rotating ring 235. The rotating ring 235 is also provided with a second gear ring 236. The second motor 237 is installed on the outer wall of the annular wetland. A second gear 238 is installed on the output shaft of the second motor 237. The second gear ring 236 is meshed with the second gear 238 for transmission. At least one second water outlet pipe 234 is installed on the lower side of the first rotating ring 231. Through the above structure, when the second motor 237 drives the second gear 238 to rotate, the first rotating ring 231 is driven to rotate, thereby realizing rotary drainage.

[0043] The supporting ring 225 supports the first rotating ring 231, and the rotating ring 235 serves as a positioning. Figure 4 In the embodiment, the rotating ring 235 is L-shaped, so that the rotating ring 235 can rotate around the supporting ring 225.

[0044] Further, see Figure 4 The second rotary drainer 230 also includes a second rotary ring 232, which is located above the first rotary ring 231. A drain pipe 233 is connected to the bottom of the second rotary ring 232, and the drain pipe 233 passes through the first rotary ring 231 and is fixedly connected to the first rotary ring 231. The second water collection channel 220 is also provided with a third water outlet 222 above the second water outlet 221, and the third water outlet 222 is used to guide water into the second rotary ring 232. The first control valve 223 and the second control valve 224 are respectively installed on the second water outlet 221 and the third water outlet 222. By controlling the opening and closing of the first control valve 223 and the second control valve 224, the water level of the inner annular wetland is controlled, the purpose of the inner annular wetland breathing is achieved, and intermittent drainage is formed to enhance the tidal flow effect.

[0045] In this embodiment, the first control valve 223 and the second control valve 224 are electromagnetic valves. When the first control valve 223 is opened, water is discharged from the second water outlet 221, and the water level of the inner annular wetland decreases. When the first control valve 223 is closed and the second control valve 224 is opened, the water level of the inner annular wetland rises. During the rising period of the water level, drainage to the next layer is suspended.

[0046] Furthermore, a plurality of partitions 239 are respectively installed in the first rotating ring 231 and the second rotating ring 232 to facilitate intermittent drainage in different areas.

[0047] See also Figure 1 , 2 The fan-shaped purification unit located at the outermost layer includes a second fan-shaped container 310, the top of the second fan-shaped container 310 is open, the drainage channel 320 is arranged on the outer wall of the second fan-shaped container 310, and the second fan-shaped container 310 is filled with a functional matrix 301 that supplies organic electronics or inorganic electronics.

[0048] In this embodiment, the functional matrix 301 uses biochar, pyrite, and artificial matrix materials with enhanced electron donors to ensure the continuous denitrification. The functional matrix 301 needs to have long-term water immersion stability and high denitrification efficiency.

[0049] Embodiment 2: Based on Example 1, see Figure 1 , 2 In the rotating tower type multi-stage tidal flow artificial wetland system, the rotating tower type multi-stage tidal flow artificial wetland system includes a central purification wetland 100 and an annular wetland, and the annular wetland includes a second-layer annular wetland 200 and a third-layer annular wetland 300.

[0050] The central purification wetland 100, the second annular wetland 200 and the third annular wetland 300 are stepped structures from high to low. The second annular wetland 200 is the middle annular wetland, and the third annular wetland 300 is the outermost annular wetland.

[0051] The central purification wetland 100 is set as a downward vertical subsurface artificial wetland. It plays a nitrification-denitrification role in function, and also plays a role in filtering suspended matter. The water enters from the surface layer and is discharged from the bottom layer. In the vertical direction, the dissolved oxygen gradually changes from an aerobic state to an anoxic state, first undergoing a nitrification process and then gradually turning to a denitrification process. Since the central purification wetland 100 is the deepest, the matrix needs to be layered and stepped in the vertical direction. The surface layer is mainly porous and light matrix, the middle layer is mainly aggregate matrix, and the bottom layer is mainly denitrification matrix. The sewage in the central purification wetland 100 is discharged from the bottom to the first water collection channel 120, and then the sewage is discharged from the top of the first water collection channel 120, and falls to the second layer of the annular wetland 200 through the first rotary drainer 130. The dissolved oxygen is restored again during the fall.

[0052] The second layer of annular wetland 200 functions to play a nitrification-denitrification role. The tidal drainage of the second layer of annular wetland 200 is mainly controlled by two methods: one is to control the opening and closing of the first control valve 223 and the second control valve 224 to control the water level of the upper porous matrix 201 to achieve the tidal flow effect of the artificial wetland; the other is to switch the submerged state of the four fan-shaped purification unit wetlands in the second layer of annular wetland 200 through the periodic rotation drainage of the first rotary drainer 130 to achieve tidal flow.

[0053] The upper layer of the second circular wetland 200 is set as a breathing layer, with alternating aerobic-anoxic-anaerobic states. Its main function is to play a nitrification role, and it also needs to ensure the colonization of wetland plants. Therefore, porous substrates are mainly selected in the wetland matrix. The lower layer of the second artificial wetland is set as a long-term immersion layer. Its main function is to play a denitrification role. Therefore, the wetland matrix selection is mainly based on substrates that can enhance denitrification performance.

[0054] The third-layer annular wetland 300 is set as a deep-bed denitrification wetland, which mainly plays a denitrification role in function to achieve deep denitrification. Therefore, the third-layer annular wetland 300 is in an immersed state for a long time to ensure the anaerobic effect of the wetland system. The low dissolved oxygen effluent from the second-layer annular wetland 200 enters the third-layer annular wetland 300 in a slow flow state. Since the organic carbon content in the influent is limited after being treated by the previous two layers of artificial wetlands, the heterotrophic denitrification capacity of the system is limited. In order to ensure the denitrification and denitrification effect of the third-layer annular wetland 300, the matrix of the third-layer annular wetland 300 needs to be set as a functional matrix material that can supply organic or inorganic electrons.

[0055] The material selection of the rotating tower multi-stage tidal flow artificial wetland system of the present invention must meet the requirements of treatment effect, structural stability and long-term use. According to the different functions of each layer of wetland, the matrix and construction materials should be scientifically selected: Central Purification Wetland 100: The surface matrix should be made of lightweight materials with high porosity, such as expanded perlite or lightweight ceramsite, to promote nitrification in an aerobic environment and ensure sufficient dissolved oxygen in the water body, which is suitable for the growth and activity of nitrifying bacteria. The middle matrix should be made of aggregate-type matrix with good permeability, such as crushed stone or volcanic rock. This type of matrix provides moderate water flow resistance and provides support for the alternation of aerobic and anoxic microenvironments. The bottom matrix should be made of organic matter such as sawdust, straw or wood chips, which can promote denitrification and convert nitrates into nitrogen gas.

[0056] The second layer of circular wetland 200, that is, the middle layer of circular wetland: the upper breathing layer selects porous substrates, such as ceramsite or coarse sand, to enhance nitrification reaction and provide a stable substrate for plant colonization. The porous structure is conducive to root growth and air entry. The lower soaking layer uses substrates that can enhance denitrification reaction, such as wood chips, straw or rice husks. Such materials can provide electron donors in anaerobic environments and promote the denitrification process.

[0057] The third layer of annular wetland 300, i.e. the outermost annular wetland: select functional matrix that can supply organic or inorganic electrons, such as biochar, pyrite, and artificial matrix materials with enhanced electron donors, to ensure the continuous denitrification. The matrix of the third layer of annular wetland 300 needs to have long-term water immersion stability and high denitrification efficiency.

[0058] Embodiment 3: On the basis of Example 1 or 2, the wetland plants 400 on the central purification wetland 100, the second layer annular wetland 200 (intermediate layer annular wetland) and the third layer annular wetland 300 (outermost layer annular wetland) play an important ecological and treatment function in the artificial wetland system. They not only provide an attachment matrix for microorganisms, but also absorb pollutants in the water and promote nitrification and denitrification reactions through root oxidation-reduction. In the rotating tower multi-stage tidal flow artificial wetland device of the present invention, different levels of wetlands have different requirements for plant selection to adapt to their specific physical and chemical environments.

[0059] Plant selection for the Central Purification Wetland 100: In terms of function, the plants in the Central Purification Wetland 100 are mainly used to help maintain the surface aerobic environment and provide a stable root attachment surface to promote the growth of nitrifying bacteria. At the same time, plants can also absorb some nitrogen and reduce the ammonia nitrogen load. In terms of plant types, emergent plants with developed root systems, such as cattails and reeds, are selected. These plants can grow well in oxygen-rich and oxygen-deficient environments and are suitable for the conditions of vertical subsurface flow wetlands.

[0060] Plant selection for the second-layer circular wetland 200: In terms of function, the second-layer circular wetland 200 is designed as a tidal flow wetland, and plants need to adapt to the conditions of periodic flooding and drainage. Plants promote nitrification under aerobic conditions, provide a stable attachment matrix during tidal flow, and can effectively absorb nutrients such as nitrogen and phosphorus. In terms of plant types, it is recommended to select plants that can adapt to tidal flow, such as water plantain and water candle. This type of plant has a strong ability to resist flooding and can maintain good ecological functions under tidal changes.

[0061] Selection of plants for the third-layer circular wetland 300: In terms of function, the third-layer circular wetland 300 is a deep-bed denitrification wetland, which is in a long-term flooded and anaerobic state. Plants need to be able to withstand flooding and survive in a low dissolved oxygen environment. Its main function is to provide a root microenvironment, enhance denitrification, and absorb pollutants through plant metabolism. In terms of plant types, aquatic plants that are resistant to long-term flooding and low oxygen are selected, such as yellow iris and canna. These plants have strong stress resistance and adapt to anaerobic wetland conditions. At the same time, they promote denitrification through root secretions.

[0062] Embodiment 4: Based on Example 1, 2 or 3, a sewage treatment method adopts the rotating tower multi-stage tidal flow artificial wetland system, and the treatment method comprises the following steps: S1, sewage enters from the water inlet 111 of the central purification wetland 100; S2, after the sewage undergoes nitrification reaction in an aerobic environment from top to bottom, it enters the first water collection channel 120 from the bottom; S3, the water in the first water collecting channel 120 flows from bottom to top into the first rotary drainer 130, and then is discharged to the outer adjacent annular wetland surface in the form of a rotary waterfall; S4. In this layer of the annular wetland, water undergoes nitrification reaction in an anoxic environment from top to bottom and then enters the second water collection channel 220 from the bottom; S5, the water in the second water collecting channel 220 flows from bottom to top into the second rotary drainer 230, and then is discharged to the outer adjacent annular wetland surface in the form of a rotary waterfall; S6. Finally, the water is discharged to the outermost annular wetland surface in the form of a rotating waterfall. After nitrification treatment in an anaerobic environment from top to bottom, the water enters the drainage channel 320 from the bottom and is finally discharged from the drainage port 321.

[0063] Specifically, according to the design structure and function of the system, the operating parameters of each layer of wetlands determine the efficiency of sewage treatment and the denitrification effect.

[0064] Central Purification Wetland 100 operating parameters: The hydraulic retention time (HRT) is set at 4-6 hours to ensure that the water has enough residence time in the wetland matrix to complete the nitrification reaction. In the downward vertical underflow mode, the water flow rate is controlled at 0.1-0.3 m3 per hour to ensure uniform vertical penetration of the water flow. The surface dissolved oxygen concentration should be maintained at 4-6 mg / L to promote the nitrification process; the bottom dissolved oxygen should be controlled below 0.5 mg / L to start the denitrification process.

[0065] The second layer of circular wetland 200 operating parameters: The tidal cycle is set to every 6 to 12 hours, and the periodic switching of the rotating overflow weir ensures that each fan-shaped module can go through a complete cycle of water intake-drainage-reoxygenation-drainage. The hydraulic retention time (HRT) is set to 3 to 5 hours, and the tidal flow periodically controls the up and down changes in the water level to promote nitrification in the breathing layer and denitrification in the immersion layer. For water level regulation, the water level of the upper breathing layer should be controlled 10 to 20 cm below the wetland surface to avoid excessive immersion; the lower immersion layer should remain fully submerged. The dissolved oxygen concentration in the breathing layer should be maintained at 2 to 4 mg / L to accommodate nitrification; the dissolved oxygen in the immersion layer should be close to 0 mg / L to optimize denitrification.

[0066] The third layer of circular wetland 300 operating parameters: The hydraulic retention time (HRT) is set at 5-8 hours. The third layer of the circular wetland 300 is mainly a deep bed denitrification wetland. Long retention time helps improve denitrification efficiency. The flow rate should be controlled at 0.05~0.2 m³ / h to ensure that the water flows through the substrate at a slow speed to maximize denitrification.

Claims

1. A rotating tower multi-stage tidal flow artificial wetland system, characterized by: The invention comprises a central purification wetland (100), wherein the central purification wetland (100) is surrounded by multiple layers of annular wetlands in descending order, wherein the annular wetlands of each layer are respectively composed of multiple fan-shaped purification units, a first water collection channel (120) is provided between the central purification wetland (100) and the adjacent annular wetlands, the bottom of the first water collection channel (120) is connected to the bottom of the central purification wetland (100), a second water collection channel (220) is provided for each of the fan-shaped purification units corresponding to the inner side between adjacent annular wetlands, the bottom of the second water collection channel (220) is connected to the bottom of the corresponding fan-shaped purification unit on the inner side, a drainage channel (320) is provided on the outer side of the outermost annular wetland, and a drainage outlet (321) is provided on the outer side of the upper end of the drainage channel (320); The upper end of the central purification wetland (100) is provided with a water inlet (111), the top of the first water collection channel (120) is provided with a first rotary drainer (130), and the top of the second water collection channel (220) is provided with a second rotary drainer (230), the first rotary drainer (130) is used for rotary cascading drainage to the top of the adjacent annular wetland, and the second rotary drainer (230) is used for rotary cascading drainage to the top of the outer annular wetland.

2. The rotating tower multi-stage tidal flow artificial wetland system according to claim 1 is characterized in that: The central purification wetland (100) comprises a central container (110), a water inlet (111) is arranged at the top of the central container (110), a first water collection channel (120) is arranged on the outer wall of the central container (110), and the central container (110) is filled with a first nitrification treatment matrix.

3. The rotating tower multi-stage tidal flow artificial wetland system according to claim 2 is characterized in that: The first nitrification treatment matrix is ​​provided with three layers, which are, from top to bottom, a porous light matrix (101), an aggregate matrix (102), and a denitrification matrix (103).

4. The rotating tower multi-stage tidal flow artificial wetland system according to claim 1, characterized in that: The first rotary drainer (130) comprises a rotary groove ring (131), a first gear ring (134) and a first motor (135), wherein a support ring (133) is fixedly mounted at the inner hole of the upper side of the rotary groove ring (131), a limit ring (112) is fixedly mounted at the top of the central purification wetland (100), the support ring (133) is movably sleeved on the outer side of the limit ring (112), the inner hole of the support ring (133) is mounted with the first gear ring (134), and the first motor ( 135) is installed on the top of the central purification wetland (100), the output shaft of the first motor (135) is installed with a first gear (136), and the first ring gear (134) is meshed with the first gear (136) for transmission; the outer side of the first water collection channel (120) is provided with a first water outlet (121), the first water outlet (121) extends into the rotating groove ring (131), and the lower side of the rotating groove ring (131) is installed with at least one first water outlet pipe (132).

5. The rotating tower multi-stage tidal flow artificial wetland system according to claim 1 is characterized in that: The fan-shaped purification unit located in the inner layer includes a first fan-shaped container (210), the top of the first fan-shaped container (210) is open, the outer wall of the first fan-shaped container (210) is provided with a second water collection channel (220), and the first fan-shaped container (210) is filled with a second nitrification treatment matrix.

6. The rotating tower multi-stage tidal flow artificial wetland system according to claim 5, characterized in that: The second nitrification treatment matrix is ​​provided with two layers, which are, from top to bottom, a porous matrix (201) and a denitrification enhancement matrix (202).

7. The rotating tower multi-stage tidal flow artificial wetland system according to claim 1, characterized in that: The second rotary drainer (230) comprises a first rotating ring (231), a second gear ring (236) and a second motor (237); a second water outlet (221) is provided on the second water collecting channel (220); a supporting ring (225) is fixedly mounted on the outer wall of the annular wetland below the second water outlet (221); a rotating ring (235) is movably supported on the supporting ring (225); the first rotating ring (231) is mounted on the rotating ring (235); a second gear ring (236) is also mounted on the rotating ring (235); a second motor (237) is mounted on the outer wall of the annular wetland; a second gear (238) is mounted on the output shaft of the second motor (237); the second gear ring (236) and the second gear (238) are meshed and driven; at least one second water outlet pipe (234) is mounted on the lower side of the first rotating ring (231).

8. The rotating tower multi-stage tidal flow artificial wetland system according to claim 7, characterized in that: The second rotary drainer (230) further comprises a second rotary ring (232), the second rotary ring (232) being located above the first rotary ring (231), the bottom of the second rotary ring (232) being connected to a drain pipe (233), the drain pipe (233) passing through the first rotary ring (231) and being fixedly connected to the first rotary ring (231); A third water outlet (222) is further provided on the second water collecting channel (220) above the second water outlet (221). The third water outlet (222) is used to guide water into the second rotating ring (232). A first control valve (223) and a second control valve (224) are respectively installed on the second water outlet (221) and the third water outlet (222).

9. The rotating tower multi-stage tidal flow artificial wetland system according to claim 1, characterized in that: The fan-shaped purification unit located at the outermost layer includes a second fan-shaped container (310), the top of the second fan-shaped container (310) is open, the drainage channel (320) is arranged on the outer wall of the second fan-shaped container (310), and the second fan-shaped container (310) is filled with a functional matrix (301) that supplies organic electrons or inorganic electrons.

10. A sewage treatment method, characterized in that: A rotating tower multi-stage tidal flow artificial wetland system according to any one of claims 1 to 9 is used, and the treatment method comprises the following steps: S1, sewage enters from the water inlet (111) of the central purification wetland (100); S2, the sewage undergoes nitrification reaction in an aerobic environment from top to bottom and then enters the first water collection channel (120) from the bottom; S3, the water in the first water collection channel (120) flows from bottom to top into the first rotary drainer (130), and is then discharged to the outer adjacent annular wetland surface in the form of a rotary waterfall; S4. In the annular wetland, water undergoes nitrification from top to bottom in an anoxic environment and then enters the second water collection channel (220) from the bottom; S5, the water in the second water collection channel (220) flows from bottom to top into the second rotary drainer (230), and is then discharged to the outer adjacent annular wetland surface in the form of a rotary waterfall; S6. Finally, the water is discharged to the outermost annular wetland surface in the form of a rotating waterfall. After nitrification treatment in an anaerobic environment from top to bottom, the water enters the drainage channel (320) from the bottom and is finally discharged from the drain outlet (321).

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