Low-carbon local circumfluence contact wetland system and method for purifying water quality thereof

Abstract

The present application relates to a kind of low-carbon local partial circumfluent flow contact wetland system and its water quality purification method, belong to water treatment technical field.The low-carbon local partial circumfluent flow contact wetland system of the present application, including ecological activity recovery unit, nitrogen cycle intensification unit, circumfluent flow contact phosphorus cycle intensification unit and ecological stable unit in series, by the use of plant growth limit ring, frame filler and large leaf floating plant joint construction denitrification habitat, circumfluent flow contact array type filler column distribution, establish filler column adsorption and hold phosphorus cycle path of plant absorption and utilization, inverted horn support steel wire bundle support gramineae method etc.The combination use of technical scheme reaches no power low-carbon, prevent plant succession invasion, circumfluent flow contact anti-clogging, nutrient salt enrichment plant root system convenient recovery, with the beneficial effects such as enhanced denitrification and phosphorus removal, realize a kind of low-carbon local partial circumfluent flow contact wetland system applied to ecological safety buffer zone.

Description

TECHNICAL FIELD

[0001] The present application relates to a low-carbon local circumfluent flow contact wetland system and a method for purifying water quality, and belongs to the technical field of water treatment. BACKGROUND

[0002] The effluent of sewage treatment plants generally still contains nitrogen and phosphorus nutrients and other pollutants with concentrations higher than the limit values of the surface water environmental quality standard when it is discharged to meet the discharge standard. Direct discharge of the effluent into natural water bodies will have a great impact on the water environmental quality of the natural water bodies. Therefore, an ecological safety buffer wetland system is generally constructed to transitionally treat the effluent before it enters the natural receiving water bodies. The main role of the ecological safety buffer wetland system is to improve the ecological toxicity of the effluent of the sewage plant through intensified artificial ecological treatment, and further reduce the organic pollutants and nitrogen and phosphorus nutrients in the effluent, so as to achieve the purpose of ecological safety buffering and protecting the natural receiving water bodies. In recent years, various ecological safety buffer wetland projects have been built, but due to unreasonable system construction, there are many problems in operation. For example, the use of high-energy consumption aeration measures will lead to high energy consumption of the system operation, and the use of chemical agents to remove nutrients will lead to chemical sludge by-products. Such technical solutions that industrialize the ecological safety buffer wetland treatment do not have low-carbon potential. Although the method of using substrate fillers to remove nutrients in sewage is more ecological, most of them use submerged wetlands, filter beds, filter dams and other technical solutions that cut off the free water surface of the wetland, which leads to the biggest problem of clogging after a period of operation. In addition, most of the surface flow wetlands using emergent plants will have dominant succession after a period of operation, which will invade the growth space of other plants, eventually leading to the crazy growth of local plants, affecting the uniformity of the overwater of the surface flow wetland, and further leading to large area dead water area and wetland failure. The wetland using floating bed or floating island technical solution, when the plants grow, the plant roots are embedded in the floating bed net bag or the bottom of the porous planting pot, and the harvesting and recycling of the plant root residues are difficult, and incomplete recycling will cause the rotten plant root residues to release pollutants into the water body.

[0003] In the prior art, there are sewage treatment plant tail water wetlands, such as CN116444066A, which constructs a sewage plant tail water wetland at the bank of a river, but the wetland does not consider the specific technical solutions to solve the gravel bed blockage problem, plant succession invasion problem, and tail water denitrification and phosphorus removal problem. Document CN107720973B provides a sewage treatment plant tail water artificial wetland treatment system, which introduces floating plants, but does not consider the planting technology of floating plants. The use of subsurface wetlands that cut off the water surface cannot avoid the problem of blockage. The use of high molecular polymer iron salt or aluminum salt for phosphorus removal and the use of an aeration device for nitrification increase the consumption of materials and energy, which is not economical and not ecological, and also has the problem of chemical phosphorus removal byproducts. Comparative document CN219507759U provides a wetland system for efficient purification of sewage plant tail water, which includes an aeration channel that consumes energy, and also includes a large amount of vertical and horizontal subsurface wetlands, which are wetland systems that cut off the water surface and are difficult to avoid the problem of wetland blockage during long-term operation. Comparative document CN110143721A provides a free water surface cascade ecological wetland and its water quality purification method, wherein the first nitrification and denitrification denitrification function area is provided with a large area of ecological floating island, and the plant planting method of the ecological floating island has the problem of difficult harvesting and recycling of plant roots. The second aquatic plant pollution reduction function area plants a large number of emergent plants, which causes the problem of uneven water flow caused by plant succession invasion. The third porous medium filter bed has the problem of blockage of cut-off water flow.

[0004] The existing ecological safety buffer zone wetland system technical solutions mentioned in the above comparative documents all have some problems to be optimized, and there is an urgent need for new technical solutions to realize a low-carbon, non-blocking, plant succession invasion prevention, nutrient salt enrichment plant root convenient recycling, and strong denitrification and phosphorus removal function ecological safety buffer zone wetland system. SUMMARY

[0005] In order to solve the above problems, the application provides a low-carbon local partial circular flow contact wetland system and a water quality purification method thereof. The low-carbon local partial circular flow contact wetland system comprises an ecological activity recovery unit, a nitrogen cycle strengthening unit, a circular flow contact phosphorus cycle strengthening unit and an ecological stability unit connected in sequence. The system adopts continuous free water surface and does not contain power consumption device, so that the whole process is energy-free, low-carbon and ecological activity recovery. The ecological activity recovery unit is arranged in front of the nitrogen cycle strengthening unit, which can recover the ecological property of tail water. The nitrogen cycle strengthening unit is arranged in front of the circular flow contact phosphorus cycle strengthening unit, which can strengthen denitrification and nitrogen removal. The circular flow contact phosphorus cycle strengthening unit is arranged in front of the ecological stability unit, which can remove phosphorus in water and reduce the phosphorus removal load of the circular flow contact phosphorus cycle strengthening unit, prolong the service life of the unit, and improve the ecological stability of tail water. The ecological stability unit is arranged at the last position, which can ensure the water quality of the final effluent.

[0006] To achieve the above technical purposes, the technical scheme adopted by the embodiments of the application is:

[0007] In a first aspect, the embodiments of the application provide a low-carbon local partial circular flow contact wetland system, which comprises an ecological activity recovery unit, a nitrogen cycle strengthening unit, a circular flow contact phosphorus cycle strengthening unit and an ecological stability unit connected in sequence.

[0008] The ecological activity recovery unit comprises a water inlet pipe, a water distribution weir and a plant planting area. The inlet of the water inlet pipe is connected with the outlet of the tail water pipe of the sewage treatment plant. The outlet of the water inlet pipe is connected with the inlet of the water distribution weir. Tail water overflows from the water distribution weir to the plant planting area. The plant planting area is used for planting emergent plants. The emergent plants are planted in the inside of the plant growth limiting ring. The plant growth limiting rings are arranged in an array in the plant planting area.

[0009] The nitrogen cycle strengthening unit comprises a framework filler and a large-leaf floating aquatic plant. The framework filler is loosely stacked in the nitrogen cycle strengthening unit. The distance between the highest stacking position and the water surface is greater than 500 mm. The large-leaf floating aquatic plant is planted at the bottom of the nitrogen cycle strengthening unit. The large-leaf blades of the large-leaf floating aquatic plant float and grow on the water surface and shield the water surface.

[0010] The circular flow contact phosphorus cycle strengthening unit comprises a filler column and a water culture plant. The filler columns are arranged in an array. There is a free water surface between adjacent filler columns. The water culture plant is planted in the filler column.

[0011] The ecological stabilization unit comprises submerged plants, an outflow water collecting tank and an outflow pipe, the submerged plants are planted on the bottom surface of the ecological stabilization unit, the outflow water collecting tank is located downstream of the ecological stabilization unit, the outflow water collecting tank adopts overflow water inlet, and water collection is discharged through the outflow pipe.

[0012] Further, the plant growth limiting ring has an inner diameter of 300-500 mm and a height of 300-500 mm, the plant growth limiting ring is axially cut into the soil at the bottom of the ecological activity recovery unit, and the super height is not less than 100 mm.

[0013] Further, the frame filler comprises a frame and a carbon felt belt, two ends of the carbon felt belt are fixed on the frame, and the water flow direction is perpendicular to the length direction of the carbon felt belt.

[0014] Further, the filler column comprises a mesh cage, a phosphorus buffering material and an inverted-horn supporting steel wire bundle, the phosphorus buffering material is filled in the mesh cage;

[0015] The mesh cage is a hollow cylindrical steel wire cage with a wall thickness of 200-500 mm, an inner diameter of the mesh cage is less than 500 mm, and a hole diameter of the mesh cage is less than 50 mm;

[0016] The phosphorus buffering material is a material having weak combination with phosphate, such as volcanic rock or medical stone, and the material has a particle size of 50-100 mm;

[0017] Each steel wire in the inverted-horn supporting steel wire bundle is fixedly connected to the inner circumference of the bottom of the mesh cage, and the upper end is gathered into a bundle upward, the upper end of each steel wire is lower than the upper edge of the filler column, and the distance between the upper end of the steel wire and the upper edge of the filler column is 200-400 mm;

[0018] The roots of the water planting plants are clamped at the upper end of the inverted-horn supporting steel wire bundle.

[0019] In a second aspect, the embodiment of the present application provides a method for purifying water quality by using the low-carbon local circular flow contact wetland system in the first aspect, and the method comprises the following steps:

[0020] In step S1, tail water of a sewage treatment plant enters an ecological activity recovery unit: tail water of a sewage treatment plant enters a water distribution weir through a water inlet pipe, and is evenly distributed to a plant planting area by crossing the water distribution weir, and the tail water is intercepted and filtered by emergent plants planted in a plant growth limiting ring;

[0021] Step S2, the effluent of step S1 enters the nitrogen cycle enhancement unit, the sewage is supplemented with organic carbon source in the water body through the preposed ecological activity recovery unit, the microorganism habitat with carbon source and anoxic is formed in the nitrogen cycle enhancement unit, the nitrogen in the water body can be strengthened to carry out denitrification, and the nitrate nitrogen in the water body is removed to a certain extent.

[0022] Step S3, the effluent of step S2 enters the phosphorus cycle enhancement unit of surrounding flow contact, the tail water is contacted with the phosphorus buffer material in the array type evenly distributed filler column, the phosphate in the tail water is effectively adsorbed and held, and the function of phosphorus removal of the wetland system is realized.

[0023] Step S4, the tail water enters the ecological stability unit, and the tail water after staying in the ecological stability unit overflows into the effluent collecting tank and is finally discharged by the effluent pipe.

[0024] Further, the water inflow of the ecological activity recovery unit is Q m 3 / h, the water depth H1 is 0.3-1.0 m, the apparent hydraulic retention time T1 is greater than 6 h, the area S1 is greater than Q*T1 / H1, the generalization length-width ratio R1 is greater than 10, and the checking water section flow velocity V1 is 0.02-0.1 m / s.

[0025] Further, the water inflow of the nitrogen cycle enhancement unit is the water outflow of the ecological activity recovery unit Q m 3 / h, the water depth H2 is 1-3 m, the apparent hydraulic retention time T2 is greater than 12 h, the area S2 is greater than Q*T2 / H2, the generalization length-width ratio R2 is greater than 10, and the checking water section flow velocity V2 is 0.02-0.5 m / s.

[0026] Further, the water inflow of the phosphorus cycle enhancement unit of surrounding flow contact is the water outflow of the nitrogen cycle enhancement unit Q m3 / h, the water depth H3 is 0.8-1.0 m, the apparent hydraulic retention time T3 is greater than 0.5 h, the area S3 is greater than Q*T3 / H3, the generalization length-width ratio R3 is greater than 10, and the checking water section flow velocity V3 is 0.02-0.2 m / s.

[0027] Further, the water inflow of the ecological stability unit is the water outflow of the phosphorus cycle enhancement unit of surrounding flow contact Q m 3 / h, the water depth H4 is greater than 3 m, the apparent hydraulic retention time T4 is greater than 24 h, and the area S4 is greater than Q*T4 / H4.

[0028] The technical scheme provided by the embodiment of the application has the following beneficial effects:

[0029] 1. The ecological safety buffer zone wetland system of the sewage treatment plant is composed of the ecological activity recovery unit, the nitrogen cycle strengthening unit, the phosphorus cycle strengthening unit of the surrounding flow contact and the ecological stability unit, through the use of the plant growth limiting ring, the combination of the frame filler and the large leaf floating plant to build the denitrification habitat, the arrayed filler column distribution of the surrounding flow contact, the establishment of the phosphorus cycle path of the filler column adsorption and holding and the plant absorption and utilization, the method of supporting the gramineae plants by the inverted horn supporting steel wire bundle and other technical schemes, the no-power low-carbon, the prevention of plant succession invasion, the surrounding flow contact anti-clogging, the nutrient salt enrichment plant root system convenient recovery, the denitrification and phosphorus removal effect and other beneficial effects can be realized at the same time.

[0030] 2. The ecological activity recovery unit is the first unit for the tail water of the sewage treatment plant, the plant growth limiting ring is laid in the ecological activity recovery unit, the emergent plants are planted in the plant growth limiting ring, the growth range of the tillering emergent plants is limited in the ring, therefore, the plant distribution of the whole functional unit is uniformly distributed according to the distribution of the arrayed plant growth limiting ring, the local plant overgrowth is prevented, the other plant growth space is prevented from being invaded by the succession, the water unevenness of the whole functional unit caused by the succession is prevented, the dead water area and the short flow of the functional unit are effectively avoided, and the long-acting stable operation of the functional unit is ensured.

[0031] 3. The nitrogen cycle strengthening unit is arranged after the ecological activity recovery unit, the ecological activity of the tail water of the sewage treatment plant is recovered after the tail water is contacted with a large number of plants in the ecological activity recovery unit, the plant root exudates can supplement the denitrification carbon source, the tail water enters the nitrogen cycle strengthening unit immediately, the frame filler made of the carbon felt with microbial affinity can attach the denitrification microorganisms participating in the nitrogen cycle, the large leaf floating plants on the water surface can effectively block the atmospheric reoxygenation to the water body of the nitrogen cycle strengthening unit, the microbial habitat with the carbon source and the anoxic environment is formed, and the nitrogen in the water body can be strengthened to carry out the denitrification.

[0032] 4. The phosphorus cycle strengthening unit of the surrounding flow contact adopts the arrayed filler column form filler which is uniformly distributed to contact with the tail water, so as to adsorb and hold the phosphorus in the water, compared with the traditional forms such as the subsurface wetland, the filter dam and the filter wall, the arrayed filler column which is uniformly distributed will not cut off the water surface, the water passing performance is better, and the water passing channel will not be blocked with the growth of the biological membrane on the filler, the phosphorus cycle strengthening unit composed of the filler column does not block the free water surface of the whole system, and the system can be ensured not to be blocked.

[0033] 5. The phosphorus buffer material in the packing column of this invention is selected from materials such as volcanic rock and maifanite, which are weakly bound to phosphate. It can effectively adsorb and retain phosphate in the flowing tailwater, realizing the function of phosphorus removal in wetland systems. The phosphate adsorbed and retained by the phosphate-weakly bound material has the reversibility of plant reuse. After planting plants in the packing column, they can absorb and utilize the phosphate adsorbed and retained by the packing, establishing a phosphorus cycle path of adsorption and retention by the packing column plus absorption and utilization by hydroponic plants. By continuously harvesting the plants in the packing column, the adsorption saturation time of the packing can be extended, thereby extending the service life of the packing.

[0034] 6. The inverted trumpet-shaped support wire bundle in the filler column of this invention supports plant growth. The structural design of the inverted trumpet-shaped support wire bundle can effectively support and fix plant growth, preventing lodging. The hydroponic plants are only fibrous grasses. Combined with the planting effect of the inverted trumpet-shaped support wire bundle, the plant roots can be easily pulled out in the opposite direction when the hydroponic plants are harvested, and the harvesting of plants is more thorough. This solves the traditional wetland technology problem of difficult root harvesting caused by the difficulty in separating plants from the planting device.

[0035] 7. The use of the surrounding flow contact phosphorus circulation enhancement unit in this invention can ensure the continuity of the free water surface of the entire system and will not trap floating debris from upstream. In addition, the overflow outlet at the end allows the floating debris on the free water surface of the entire system to flow to the outlet position. Even if plant harvesting debris falls onto the water surface occasionally, there will be no scum or foam remaining on the water surface. The continuous free water surface of the entire system will be cleaner, and the operation and management of the wetland system will be easier. Attached Figure Description

[0036] Figure 1 This is a plan view of the low-carbon localized surrounding flow contact wetland system in Embodiment 1 of the present invention.

[0037] Figure 2 This is a longitudinal cross-sectional schematic diagram of the low-carbon localized surrounding flow contact wetland system in Embodiment 1 of the present invention.

[0038] Figure 3 For the present invention Figure 1 A schematic diagram of the frame packing structure in a low-carbon localized surrounding flow contact wetland system.

[0039] Figure 4 For the present invention Figure 1 A schematic diagram of the packing column in a low-carbon localized surrounding flow contact wetland system.

[0040] Figure 5 For the present invention Figure 1 A cross-sectional view of the packing column in a low-carbon localized surrounding flow contact wetland system.

[0041] Figure 6 For the present invention Figure 4 Schematic diagram of the inverted trumpet-shaped support wire bundle in the packing column.

[0042] Explanation of reference numerals in the attached diagram: 1-Ecological activity restoration unit; 2-Nitrogen cycle enhancement unit; 3-Circulating flow contact phosphorus cycle enhancement unit; 4-Ecological stabilization unit; 11-Inlet pipe; 12-Water distribution weir; 13-Plant growth limiting ring; 14-Emerging plants; 21-Frame packing material; 22-Large-leaved floating plants; 211-Frame; 212-Carbon felt belt; 31-Packing column; 32-Hydroponic plants; 311-Net cage; 312-Phosphorus buffer material; 313-Inverted trumpet support wire bundle; 41-Submerged plants; 42-Outlet water collection trough; 43-Outlet pipe. Detailed Implementation

[0043] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "inner" and "outer", "upper" and "lower", "left" and "right" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention.

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] Example 1

[0046] like Figure 1 and 2 As shown, a low-carbon localized surrounding flow contact wetland system includes an ecological activity restoration unit 1, a nitrogen cycle enhancement unit 2, a surrounding flow contact phosphorus cycle enhancement unit 3, and an ecological stabilization unit 4 connected in series.

[0047] The ecological restoration unit 1 includes an inlet pipe 11, a weir 12, and a planting area. The inlet flow rate of the ecological restoration unit 1 is Q m³. 3 / h, water depth H1 is 0.3-1.0m, apparent hydraulic residence time T1>6h, area S1>Q*T1 / H1, shape can be irregular, generalized length-to-width ratio R1>10, check flow velocity V1 of cross section is 0.02~0.1m / s;

[0048] The inlet of the inlet pipe 11 is connected to the outlet of the wastewater treatment plant tailwater pipe, and the outlet of the inlet pipe 11 is connected to the inlet of the distribution weir 12. The tailwater overflows from the distribution weir 12 to the plant planting area. The plant planting area is used to plant emergent plants 14. The emergent plants 14 are only planted inside the plant growth limiting ring 13. The plant growth limiting ring 13 is arranged in an array to fill the plant planting area.

[0049] The plant growth limiting ring 13 has an inner diameter of 300-500 mm and a height of 300-500 mm, and is axially cut into the soil at the bottom of the ecological activity recovery unit 1, and the super height is not less than 100 mm.

[0050] The nitrogen cycle strengthening unit 2 comprises a frame filler 21 and a large leaf floating aquatic plant 22. The water inflow of the nitrogen cycle strengthening unit 2 is Q m 3 / h, the water depth H2 is 1-3 m, the apparent hydraulic retention time T2 is >12 h, the area S2 is >Q*T2 / H2, the shape can be irregular, the generalization aspect ratio R2 is >10, and the checked water section flow velocity V2 is 0.02-0.5 m / s.

[0051] The frame filler 21 is stacked in the nitrogen cycle strengthening unit 2, and the distance between the highest stacking position and the water surface is greater than 500 mm. The large leaf floating aquatic plant 22 is planted at the bottom of the nitrogen cycle strengthening unit 2, and the large leaf blades of the large leaf floating aquatic plant 22 float and grow on the water surface and shield the water surface. The leaf blades shielding the water surface can effectively block the reoxygenation of the atmosphere to the water body, creating an anoxic environment in the water body. The microorganisms attached to the frame filler 21 in the water body can perform denitrification under the anoxic environment, removing nitrate in the water body to achieve the effect of denitrification. The frame filler 21 and the large leaf floating aquatic plant 22 cooperate to realize the denitrification function.

[0052] As shown in Figure 3 , the frame filler 21 comprises a frame 211 and a carbon felt belt 212, and the two ends of the carbon felt belt 212 are fixed on the frame 211. The water flow direction is perpendicular to the length direction of the carbon felt belt 212.

[0053] Specifically, the frame 211 is a composite resin material with a density greater than water and a corrosion prevention function. The two ends of each carbon felt belt 211 are tied to the corresponding horizontal rods on the frame 211, and the resulting frame filler 21 can provide a large specific surface area for denitrifying microorganisms to attach to, and also has good water passing performance.

[0054] The surrounding flow contact phosphorus cycle strengthening unit 3 comprises a filler column 31 and a water culture plant 32. The filler columns 31 are arranged in an array, and there is a free water surface between adjacent filler columns 31. The water culture plant 32 is planted in the filler column 31. The water inflow of the surrounding flow contact phosphorus cycle strengthening unit 3 is Q m 3 / h, the water depth H3 is 0.8-1.0 m, the apparent hydraulic retention time T3 is >0.5 h, the area S3 is >Q*T3 / H3, the shape can be irregular, the generalization aspect ratio R3 is >10, and the checked water section flow velocity V3 is 0.02-0.2 m / s.

[0055] As shown in Figure 4 and 5As shown, the filler column 31 comprises a net cage 311, a phosphorus buffering material 312 and an inverted-horn supporting steel wire bundle 313, and the phosphorus buffering material 312 is filled in the net cage 311.

[0056] The net cage 311 is a hollow cylindrical steel wire cage with a wall thickness of 200-500 mm, an inner diameter of less than 500 mm and a hole diameter of less than 50 mm.

[0057] The phosphorus buffering material 312 is a material with weak binding effect on phosphate, including volcanic rock or geyserite, and has a particle size of 50-100 mm.

[0058] Each steel wire of the inverted-horn supporting steel wire bundle 313 is fixedly connected to the inner circumference of the bottom of the net cage 311 and is gathered into a bundle at the upper end, and the upper end of each steel wire is lower than the upper edge of the filler column 31, and the distance between the upper end of the steel wire and the upper edge of the filler column 31 is 200-400 mm.

[0059] As shown in Figure 6 The roots of the hydroponic plants 32 are clamped at the upper end of the inverted-horn supporting steel wire bundle 313.

[0060] The ecological stability unit 4 comprises submerged plants 41, a water outlet collection tank 42 and a water outlet pipe 43, the submerged plants 41 are planted on all the bottom surfaces of the ecological stability unit 4, the water outlet collection tank 42 is located downstream of the ecological stability unit 4, the water outlet collection tank 42 uses overflow water inlet, and the water collection is discharged through the water outlet pipe 43.

[0061] The water inlet flow of the ecological stability unit 4 is Q m 3 / h, the water depth H4 is greater than 3 m, the apparent hydraulic retention time T4 is greater than 24 h, and the area S4 is greater than Q*T4 / H4.

[0062] Example 2

[0063] This embodiment shows the application of the ecological safety buffer low-carbon local circular flow contact wetland system in the ecological safety buffer and further purification of the tail water of a sewage treatment plant.

[0064] The ecological activity recovery unit 1, the nitrogen cycle strengthening unit 2, the circular flow contact phosphorus cycle strengthening unit 3 and the ecological stability unit 4 applied to the ecological safety buffer low-carbon local circular flow contact wetland system are sequentially constructed.

[0065] The method for purifying water quality by using the above low-carbon local circular flow contact wetland system comprises the following steps:

[0066] Step S1, the tail water of the sewage treatment plant enters the ecological activity recovery unit 1: the tail water of the sewage treatment plant enters the water distribution weir 12 through the water inlet pipe 11, and is evenly distributed to the plant planting area by crossing the water distribution weir 12, and the tail water is intercepted and filtered by the emergent plants 14 planted in the plant growth limiting ring 13;

[0067] The water inlet flow of the ecological activity recovery unit 1 is 850 m 3 / h, the water depth H1 is 0.5 m, the apparent hydraulic retention time T1 is 12 h, the area S1 is 20000 m 2 , the shape is irregular, the generalization aspect ratio R1 is 50, and the checking water section flow rate V1 is 0.02 m / s.

[0068] Since the plant growth limiting ring 13 is arranged in an array at a certain interval in the ecological activity recovery unit 1, the growth range of the emergent plants 14 is limited in the ring after tillering, so that the distribution of the emergent plants 14 is uniformly distributed according to the distribution of the plant growth limiting ring 13, which can effectively prevent the occurrence of local plant overgrowth, which can lead to the succession of other plant growth spaces, resulting in uneven water flow in the entire functional unit, and can effectively avoid the occurrence of dead water area and short flow in the unit, thereby ensuring the long-term stable operation of the functional unit.

[0069] Since a large number of emergent plants 14 are planted in the ecological activity recovery unit 1, the growth and metabolism of the emergent plants 14 can release a certain amount of ecological organic matter which can be further utilized by natural microorganisms in the wetland, and the ecological activity of the tail water can be greatly recovered after passing through the ecological activity recovery unit 1.

[0070] Step S2, the effluent of step S1 enters the nitrogen cycle strengthening unit 2, and the sewage is supplemented with organic carbon source in the water body after passing through the preposed ecological activity recovery unit 1, and a microorganism habitat with carbon source and anoxic is formed in the nitrogen cycle strengthening unit 2, which can strengthen the nitrogen in the water body for denitrification and denitrification, and the nitrate nitrogen in the water body is removed to a certain extent;

[0071] The water inlet flow of the nitrogen cycle strengthening unit 2 is 850 m 3 / h, the water depth H2 is 1.5 m, the apparent hydraulic retention time T2 is 12 h, the area S2 is 7500 m 2 , the shape is irregular, the generalization aspect ratio R2 is 50, and the checking water section flow rate V2 is 0.03 m / s.

[0072] The frame filler 21 made of carbon felt with microbial affinity can attach denitrifying microorganisms involved in nitrogen cycle, and the large leaf floating aquatic plants 22 on the surface of the water body can effectively block atmospheric reoxygenation to the water body of the nitrogen cycle strengthening unit 2. Due to the large amount of plant supplement of organic carbon source in the water body in the front ecological activity recovery unit 1, a microorganism habitat with carbon source and anoxic is formed in the nitrogen cycle strengthening unit 2, which can strengthen the denitrification of nitrogen in the water body, and the nitrate nitrogen in the water body can be removed to a certain extent after the tail water passes through the nitrogen cycle strengthening unit 2.

[0073] In step S3, the effluent of step S2 enters the surrounding flow contact phosphorus cycle strengthening unit 3, and the tail water contacts the phosphorus buffer material 312 in the arrayed and uniformly distributed filler column 31, effectively adsorbing and holding the phosphate in the tail water, realizing the function of phosphorus removal in the wetland system.

[0074] The inflow of the surrounding flow contact phosphorus cycle strengthening unit 3 is 850 m 3 / h, the water depth H3 is 41 m, the apparent hydraulic retention time T3 is 1.2 h, the area S3 is 1000 m 2 , the shape is irregular, the aspect ratio R3 is 10, and the cross-sectional flow velocity V3 is 0.02 m / s.

[0075] The surrounding flow contact phosphorus cycle strengthening unit 3 uses the arrayed and uniformly distributed filler column to contact the tail water, thereby adsorbing and holding the phosphorus in the water. Compared with the traditional forms such as subsurface wetland, filter dam and filter wall, the arrayed and uniformly distributed filler column 31 truncates the water surface, has better water passing performance, and will not block the water passing channel with the growth of the biological membrane on the filler. Since the phosphorus cycle strengthening unit 3 formed by the filler column 31 does not block the free water surface of the whole system, it can ensure that the system will not be blocked.

[0076] The phosphorus buffer material 312 in the filler column 31 is selected from weakly combined materials such as volcanic rock and medical stone, which can effectively adsorb and hold the phosphate in the flowing tail water, realizing the function of phosphorus removal in the wetland system. The phosphate adsorbed and held by the weakly combined material has the reversibility of plant reuse, and the plants planted in the filler column 31 can absorb and utilize the phosphate adsorbed and held by the filler, establishing a phosphorus cycle path of adsorption and holding by the filler and absorption and utilization by the water culture plants 32 in the filler column 31. By continuously harvesting the plants in the filler column 31, the time of filler adsorption saturation is prolonged, thereby prolonging the service life of the filler.

[0077] The inverted horn supporting steel wire bundle 313 is used in the filler column 31 to support plant growth, and the structure design of the inverted horn supporting steel wire bundle 313 can effectively support and fix plant growth to prevent lodging.

[0078] The water-cultivated plant 32 is a gramineous plant using only fibrous roots, and is combined with the planting function of the inverted trumpet-shaped supporting steel wire bundle 313, so that the plant roots can be easily pulled out upward when the water-cultivated plant 32 is harvested, the plant is more completely harvested, and the traditional wetland technology problem that the plant roots are difficult to harvest due to the difficulty in separating the plant from the planting device is solved.

[0079] The phosphate in the tail water after the phosphate cycle strengthening unit 3 is effectively removed, and then the tail water enters the next unit.

[0080] In step S4, the tail water enters the ecological stabilization unit 4, and the tail water after staying in the ecological stabilization unit 4 flows into the effluent water collecting tank 42, and is finally discharged by the effluent pipe 43.

[0081] The inflow of the ecological stabilization unit 4 is 850 m 3 / h, the water depth H4 is 3.5 m, the apparent hydraulic retention time T4 is 24 h, and the area S4 is 6000 m 2 .

[0082] After the targeted treatment of the previous three units, nitrogen and phosphorus in the tail water can be further removed, but the total retention time of the previous three units is still short, and the ecology of the tail water still needs a certain recovery time, so a certain time of stay is needed in the ecological stabilization unit 4 for ecological stabilization of the tail water. Due to the denitrification and phosphorus removal effect of the preposition unit, the nutrient level of the water body has been reduced, and the outbreak of algae in the water body can be inhibited, so submerged plants are planted in the ecological stabilization unit 4 for ecological stabilization. The tail water after staying in the ecological stabilization unit 4 for a long time flows into the effluent water collecting tank 42 and is finally discharged by the effluent pipe 43.

[0083] The results of multiple monitoring of the inflow and outflow water quality after the ecological safety buffer low-carbon local circumfluent contact wetland system embodiment has been built and stably operated for half a year are shown in Table 1 below:

[0084] Table 1 Comparison of main indicators of inflow and outflow water quality after water quality purification in Example 2

[0085] Indicator COD (mg / L) TN (mg / L) TP (mg / L) Influent 28-36 2.7-9.1 0.18-0.47 Effluent 15-29 0.8-2.3 0.01-0.12

[0086] As can be seen from Table 1 above, after the sewage passes through the ecological safety buffer low-carbon local circumfluent contact wetland system, the COD, TN and TP in the outflow are reduced to a certain extent compared with the inflow.

[0087] The influent of the embodiment is derived from tail water of a municipal sewage treatment plant, and the water quality only meets the first A standard value in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant. After the effluent of the embodiment is treated by the system, the water quality indexes of COD, total nitrogen and total phosphorus meet the limit value of the fourth water quality standard in the Environmental Quality Standards for Surface Water. The embodiment effectively improves the water quality of tail water of the sewage treatment plant, and after five years of operation, the system does not appear water blockage in the local circular flow contact phosphorus removal unit. It is proved that the technical scheme adopted by the embodiment can effectively prevent blockage, and has the functions of denitrification and phosphorus removal to improve water quality.

[0088] Through the combination of the above technical schemes, such as the use of the plant growth limiting ring in the embodiment, the construction of the denitrification habitat by the combination of the frame filler and the large-leaved floating plant, the arrayed filler column distribution of the circular flow contact, the establishment of the phosphorus circulation path of adsorption and fixation of the filler column and plant absorption and utilization, and the support of the steel wire bundle by the inverted horn to support the growth of the gramineae plants, the beneficial effects of the ecological safety buffer and further purification of the tail water are achieved, such as unpowered low carbon, prevention of plant succession invasion, circular flow contact anti-clogging, convenient recovery of nutrient salt enrichment plant roots, and simultaneous strengthening of denitrification and phosphorus removal.

[0089] Finally, it should be explained that the above specific embodiments are only used to illustrate the technical scheme of the present application and not to limit it. Although the present application is described in detail with reference to the examples, those skilled in the art should understand that the technical scheme of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A low-carbon, partially circumfluent flow contact wetland system, characterized by, The ecological activity recovery unit (1), the nitrogen cycle strengthening unit (2), the phosphorus cycle strengthening unit (3) and the ecological stability unit (4) are connected in series. The ecological activity recovery unit (1) comprises a water inlet pipe (11), a water distribution weir (12) and a plant planting area, the inlet of the water inlet pipe (11) is connected with the outlet of the tail water pipe of the sewage treatment plant, the outlet of the water inlet pipe (11) is connected with the inlet of the water distribution weir (12), the tail water overflows from the water distribution weir (12) to the plant planting area, the plant planting area is used for planting emergent plants (14), the emergent plants (14) are planted in the inside of the plant growth limiting ring (13), and the plant growth limiting ring (13) is arranged in an array in the plant planting area. The inner diameter of the plant growth limiting ring (13) is 300-500 mm, the height is 300-500 mm, the plant growth limiting ring (13) is axially cut into the soil at the bottom of the ecological activity recovery unit (1), and the super height is not less than 100 mm. The nitrogen cycle strengthening unit (2) comprises frame fillers (21) and large-leaf floating aquatic plants (22), the frame fillers (21) are loosely stacked in the nitrogen cycle strengthening unit (2), the distance between the highest stacking position and the water surface is greater than 500 mm, and the large-leaf floating aquatic plants (22) are planted at the bottom of the nitrogen cycle strengthening unit (2), large leaf blades of the large-leaf floating aquatic plants (22) grow on the water surface and shield the water surface. The phosphorus cycle strengthening unit (3) comprises filler columns (31) and water planting plants (32), the filler columns (31) are arranged in an array, and there is a free water surface between adjacent filler columns (31), and the water planting plants (32) are planted in the filler columns (31). The filler column (31) comprises a mesh cage (311), a phosphorus buffer material (312) and an inverted-horn supporting steel wire bundle (313), the phosphorus buffer material (312) is filled in the mesh cage (311), and the roots of the water planting plants (32) are clamped at the upper end of the inverted-horn supporting steel wire bundle (313). The ecological stability unit (4) comprises submerged plants (41), a water outlet water collecting tank (42) and a water outlet pipe (43), the submerged plants (41) are planted at the bottom surface of the ecological stability unit (4), the water outlet water collecting tank (42) is located downstream of the ecological stability unit (4), the water outlet water collecting tank (42) adopts overflow water inlet, and water collection is discharged through the water outlet pipe (43).

2. The low-carbon, partial-encircled flow contact wetland system of claim 1, wherein, The frame filler (21) comprises a frame (211) and a carbon felt belt (212), both ends of the carbon felt belt (212) are fixed on the frame (211), and the water flow direction is perpendicular to the length direction of the carbon felt belt (212).

3. The low-carbon, partial-encircled flow contact wetland system of claim 1, wherein, The mesh cage (311) is a hollow cylindrical steel wire cage, the wall thickness is 200-500 mm, the inner diameter of the mesh cage (311) is less than 500 mm, and the mesh diameter of the mesh cage (311) is less than 50 mm. The phosphorus buffering material (312) is a material having weak binding effect on phosphate, including volcanic rock or medical stone, and the particle size of the phosphorus buffering material (312) is 50-100 mm; Each steel wire in the inverted-horn supporting steel wire bundle (313) is fixedly connected to the inner circumferences of the bottom of the net cage (311), and the upper ends thereof are gathered into a bundle upward, and the upper ends of each steel wire are lower than the upper edge of the filler column (31), and the distance between the upper ends of the steel wires and the upper edge of the filler column (31) is 200-400 mm.

4. A method for purifying water quality using the low-carbon local circumfluence contact wetland system according to any one of claims 1-3, characterized in that, The method comprises the following steps: Step S1, tail water of a sewage treatment plant enters an ecological activity recovery unit (1): tail water of a sewage treatment plant enters a water distribution weir (12) through a water inlet pipe (11), and is evenly distributed to a plant planting area by crossing the water distribution weir (12), and the tail water is intercepted and filtered by emergent plants (14) planted in a plant growth limiting ring (13); Step S2, effluent of step S1 enters a nitrogen cycle strengthening unit (2), the sewage is supplemented with organic carbon source in the water body through the preposed ecological activity recovery unit (1), a microbial habitat with carbon source and anoxic is formed in the nitrogen cycle strengthening unit (2), nitrogen in the water body is strengthened to carry out denitrification and denitrification, and nitrate nitrogen in the water body is removed to a certain extent; Step S3, effluent of step S2 enters a circumfluent flow contact phosphorus cycle strengthening unit (3), tail water is in contact with phosphorus buffering material (312) in arrayed and evenly distributed filler columns (31), and the phosphorus buffering material (312) effectively adsorbs and holds phosphate in the tail water, so that the function of phosphorus removal of the wetland system is realized; Step S4, tail water enters an ecological stability unit (4), and after the tail water stays in the ecological stability unit (4), the tail water overflows into an effluent collecting tank (42), and is finally discharged by an effluent pipe (43).

5. The method of purifying water quality according to claim 4, characterized by, The water inflow of the ecological activity recovery unit (1) is Q m 3 / h, the water depth H1 is 0.3-1.0 m, the apparent hydraulic retention time T1 is >6 h, the area S1 is >Q*T1 / H1, the generalized length-width ratio R1 is >10, and the checking water section flow velocity V1 is 0.02~0.1 m / s.

6. The method of purifying water quality according to claim 4, characterized by, The water inflow of the nitrogen cycle strengthening unit (2) is the water outflow Q m of the ecological activity recovery unit (1) 3 Water depth H2 is 1-3 m, apparent hydraulic retention time T2 is >12 h, area S2 is >Q*T2 / H2, general length-width ratio R2 is >10, and the checking water section flow velocity V2 is 0.02-0.5 m / s.

7. The method of purifying water quality according to claim 4, characterized by, The water inflow of the circumfluent flow contact phosphorus cycle strengthening unit (3) is the water outflow of the nitrogen cycle strengthening unit (2) Q m3 / h, the water depth H3 is 0.8-1.0 m, the apparent hydraulic retention time T3 is greater than 0.5 h, the area S3 is greater than Q*T3 / H3, the generalized length-width ratio R3 is greater than 10, and the checking water section flow velocity V3 is 0.02-0.2 m / s.

8. The method of purifying water quality according to claim 4, characterized by, The water inflow of the ecological stability unit (4) is the water outflow Q m of the circular flow contact phosphorus cycle strengthening unit (3) 3 / h, water depth H4>3m, apparent hydraulic retention time T4>24h, area S4>Q*T4 / H4.

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