A system and method for enhanced nitrogen and phosphorus removal tail water artificial wetland treatment

Abstract

The present invention relates to a tailwater artificial wetland treatment system and method for enhanced denitrification and phosphorus removal, which comprises a pre-pond, a micron aerated vertical submerged flow wetland, a vertical submerged flow wetland, a horizontal submerged flow wetland and a stabilization pond arranged in sequence; an immersion bioreactor is arranged in the pre-pond, an integrated air / water distributor is arranged at the bottom of the micron aerated vertical submerged flow wetland, a calcareous centimeter stone and a slow-release carbon source composite functional filler are arranged in the vertical submerged flow wetland, and a slow-release carbon source composite functional filler and a sulfur iron functional filler are arranged in the horizontal direction in the horizontal submerged flow wetland. The system first performs preliminary purification, and then performs heteroaerobic denitrification and autoaerobic denitrification in deep purification, and simultaneously enhances phosphorus removal. It has the advantages of reasonable structural design, uniform water distribution and water collection, strong synchronous denitrification and phosphorus removal capabilities, and good winter operation effects, and significantly improves the denitrification and phosphorus removal capabilities and self-repair capabilities of the tailwater artificial wetland system, and has the advantages of ecological naturalness, high efficiency and stability, simple maintenance, and economical and practical.

Description

Technical Field

[0001] The invention relates to an artificial wetland treatment system and method for enhanced denitrification and phosphorus removal tail water, belonging to the technical field of ecological water treatment. Background Art

[0002] Constructed wetlands are artificially constructed and regulated wetland systems, generally composed of plants, substrates and microorganisms, and mainly purify pollutants through physical, chemical and biological synergistic effects. When sewage flows through artificial wetlands, the substrate and its microorganisms will undergo some physical or chemical reactions with the sewage, such as absorption, adsorption, filtration, ion exchange and other reactions to effectively remove pollutants in the water body. It has the advantages of low infrastructure and operating costs, convenient management, beautification of landscapes, and improvement of regional climate. It has been successfully applied to the treatment of domestic sewage, storm runoff, polluted river water, and landfill leachate. However, the current artificial wetland technology still has problems such as low pollutant (SS, COD, TN, TP) removal efficiency, easy clogging of fillers, large land area, and high investment per ton of water, which has brought difficulties to the continuous operation of artificial wetlands. The development of technologies that can significantly improve the water purification efficiency of artificial wetlands and maintain the long-term, sustainable and stable operation of artificial wetlands is a problem that needs to be solved urgently in the current application of artificial wetlands.

[0003] For example, the main defects of traditional subsurface flow wetlands are as follows: 1. Insufficient dissolved oxygen in artificial wetlands. Limited dissolved oxygen is used to degrade organic matter, resulting in obstruction of nitrogen cycle, weak nitrification, and difficulty in removing ammonia nitrogen; 2. The wetland treatment effect is good in the initial operation, but after the filler is saturated with adsorption, the pollutant removal rate will drop sharply, resulting in easy saturation of the filler and short effect time; c. Low treatment efficiency and large area. Traditional wetlands also hinder the denitrification process due to the lack of carbon source, resulting in a large amount of nitrate nitrogen accumulation, resulting in a low total nitrogen removal rate. That is to say, when the influent water quality of the tailwater artificial wetland is sewage plant tailwater, since the current sewage plant tailwater shows a trend of low carbon nitrogen ratio, low carbon nitrogen ratio means COD / TN<3~5, and the organic carbon content in low carbon nitrogen ratio sewage is low, and denitrifying bacteria lack carbon source for denitrification, so that denitrification cannot proceed smoothly. After biochemical treatment, the carbon-nitrogen ratio of the effluent from the sewage treatment plant has been reduced to the range of 2.5-3. The low carbon-nitrogen ratio affects the biological denitrification capacity, making denitrification difficult, and the phosphorus removal effect is unsatisfactory and unstable. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the problems of low carbon-nitrogen ratio of tail water discharged from the above-mentioned sewage treatment plant, low simultaneous denitrification and phosphorus removal capacity of wetlands, and easy clogging of fillers, the present invention provides an artificial wetland treatment system and method for enhanced denitrification and phosphorus removal of tail water.

[0006] (II) Technical solution

[0007] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0008] A system for treating tail water artificial wetlands for enhanced nitrogen and phosphorus removal comprises a pre-pond, a micron aerated vertical submerged flow wetland, a vertical submerged flow wetland, a horizontal submerged flow wetland and a stabilization pond which are arranged in sequence, wherein an immersed bioreactor is arranged in the pre-pond for purifying incoming water and removing organic pollutants and ammonia nitrogen; an integrated air / water distributor is arranged at the bottom of the micron aerated vertical submerged flow wetland for evenly distributing air and water so that water and air flow upward from the bottom of the wetland through the micron aerated vertical submerged flow wetland, and an air branch pipe for aeration is also arranged above the micron aerated vertical submerged flow wetland; the vertical submerged flow wetland is provided with calcareous centimeters and slow-release carbon source composite functional fillers for enhanced nitrogen and phosphorus removal; slow-release carbon source composite functional fillers and sulfide iron functional fillers are arranged in the horizontal direction in the horizontal submerged flow wetland, and an outlet channel is arranged at the end of the horizontal submerged flow wetland; the outlet channel is connected to the stabilization pond.

[0009] As described above, in the enhanced denitrification and phosphorus removal tail water artificial wetland treatment system, preferably, the front end of the pre-pond is provided with a water inlet pipe, and the end of the pre-pond is provided with a water distribution channel and a triangular weir; the submerged bioreactor is provided with an integrated facility of chain phosphorus removal medium, filler, aeration system, and alkalinity regulation, and the filler is a flexible filler, which is conducive to aerobic microorganisms to oxidize and decompose organic pollutants in polluted water bodies, promote ammonia nitrogen nitrification process and organic phosphorus mineralization; the aeration system is provided with an air flow meter and an air regulating valve for controlling the aeration of the reactor; when in winter or low temperature conditions, a low-temperature resistant functional bacterial agent is added to the filler.

[0010] In the above-mentioned enhanced nitrogen and phosphorus removal tail water artificial wetland treatment system, preferably, the submerged bioreactor is provided with a plurality of groups, and the aeration systems between the groups are connected in series through air pipes.

[0011] The enhanced denitrification and phosphorus removal tail water artificial wetland treatment system provided by the present invention is provided with a pre-pond, a micron aerated vertical submerged flow wetland, a vertical submerged flow wetland, a horizontal submerged flow wetland and a stabilization pond in sequence along the direction of water flow. By setting an immersion bioreactor in the pre-pond, an aeration device and a chain-type phosphorus removal medium and filler are provided in the immersion bioreactor. On the one hand, aeration allows the system to maintain oxygen-rich conditions to promote the ammonia nitrogen nitrification process and inhibit denitrification reaction. Aerobic microorganisms attached to and grown by the filler decompose organic matter in the sewage. On the other hand, the phosphorus removal capacity is enhanced by the chain-type phosphorus removal medium, and organic phosphorus is mineralized, so that COD and BOD in the sewage are reduced by 30-40%, and primary purification is achieved. An integrated air / water distributor is provided in the micron aerated vertical submerged flow wetland, wherein the air distribution is used to ensure that there is sufficient oxygen at the bottom and in the middle of the vertical submerged flow wetland. Sufficient oxygen can promote nitrification reaction and inhibit denitrification reaction. When nitrogen-containing wastewater passes through the vertical submerged flow artificial wetland, ammonia nitrogen can be quickly converted into nitrate and nitrite. Nitrates and nitrites enter the vertical subsurface flow wetland with the water flow and come into contact with the slow-release carbon source composite functional filler. The slow-release carbon source composite functional filler slowly releases carbon source to provide carbon source for denitrification, solving the problem of insufficient carbon source in the denitrification process. The slow-release carbon source composite functional filler is also coated with added coated denitrifying bacteria. The denitrifying bacteria can reduce nitrite in the water body to generate harmless nitrogen gas, eliminate the harm of nitrite, consume nitrogen nutrients, and purify the water body; achieve the purpose of strengthening deammonification and phosphorus removal, and secondly, effectively prevent or slow down the blockage of the wetland through the bubble cutting effect of air distribution, effectively extending the service life of the wetland. The vertical subsurface flow wetland is equipped with a slow-release carbon source composite functional filler and calcareous centimeter stone to further enhance the effect of denitrification and phosphorus removal. At the same time, in the horizontal subsurface flow wetland, the slow-release carbon source composite functional filler and the sulfur-iron functional filler are successively set up. The slow-release carbon source composite functional filler further enhances the carbon source supply, and the denitrifying bacteria reduce the remaining nitrite in the water body to generate harmless nitrogen gas, eliminate the harm of nitrite, consume nitrogen nutrition, effectively inhibit the excessive reproduction of algae, further purify the water body, and achieve efficient heterotrophic denitrification. The combination of the slow-release carbon source composite functional filler and the sulfur-iron functional filler makes the total N in the water mainly removed by heterotrophic denitrification, hydrogen auto-oxygen denitrification and sulfur autotrophic denitrification, and more than 94% of TP is removed in the form of iron phosphate precipitation, achieving deep removal of phosphorus. The system of the present invention effectively strengthens the deep denitrification and phosphorus removal process of the tail water of a low C / N ratio sewage treatment plant, and has the synergistic effect of pollution reduction and phosphorus removal. It has the advantages of high denitrification efficiency, low carbon emissions, simple management and low operating costs, so that the pollutants in the effluent, including TN, COD and TP, can meet the requirements of the "special emission limits" of the "Pollutant Emission Standards for Urban Wastewater Treatment Plants" (Draft for Comments).

[0012] In the enhanced denitrification and phosphorus removal tailwater artificial wetland treatment system as described above, preferably, a calcareous centimeter stone filler layer and a filter material layer are sequentially arranged at the bottom from bottom to top in the micron aerated vertical subsurface flow wetland; wherein the calcareous centimeter stone filler layer is filled with calcareous centimeter stone with a particle size of 30-50 mm, an integrated air / water distributor is placed in the calcareous centimeter stone filler layer, and the filter material layer is filled with calcareous centimeter stone with a particle size of 20-40 mm for effective phosphorus removal, and an air branch pipe for aeration is also provided above the filter material layer.

[0013] As described above, in the enhanced denitrification and phosphorus removal tailwater artificial wetland treatment system, preferably, the integrated air / water distributor includes a polymer air distribution pipe, a flexible micron gas diffusion surface, a gas volume magnetic control component and a water distribution pipe interconnected with aeration, and the water distribution pipes are evenly distributed in the calcareous centimeter stone filler layer.

[0014] Furthermore, the thickness of the calcareous stone filler layer is 50cm~60cm, and the thickness of the filter material layer is 100~110cm. Water flows through the integrated air / water distributor from bottom to top into the calcareous stone filler layer and the filter material layer to achieve uniform water distribution. The components of the calcareous stone filler layer and the filter material layer are both calcareous stone. Calcium stone is a carbonate rock with calcite as the main component, and is made of crushed stone with a certain particle size. Its main component is calcium carbonate, which removes phosphorus through adsorption, co-precipitation with calcium carbonate, and crystallization of calcium phosphide with calcite as the crystallization nucleus. Phosphorus is further removed through the adsorption of calcareous stone, effectively reducing the TP content in the water. The integrated air / water distributor increases the oxygen capacity to form a strong oxidizing environment through air distribution. Through the action of microorganisms, most of the difficult-to-degrade organic matter in the water can be converted into easily degradable organic matter, thereby improving the decomposition efficiency of organic matter. On the other hand, under low temperature conditions in winter, increasing aeration can improve the flow state of water, prevent freezing, increase the concentration of dissolved oxygen, and promote nitrification. The calcareous stone filler layer is filled with calcareous stone with a particle size of 30-50mm, which is beneficial to the upward movement of water vapor. The filter material layer is set with calcareous stone with a small particle size of 20-40mm, which is beneficial to increase the contact area with the water flow and enhance the effect of adsorbing phosphorus.

[0015] In the above-mentioned enhanced denitrification and phosphorus removal tailwater artificial wetland treatment system, preferably, the vertical subsurface flow wetland is provided with a water distribution layer, a slow-release carbon source composite functional filler, and a water collection layer from bottom to top; wherein the water distribution layer is a calcareous centimeter stone filler with a particle size of 30-50 mm wrapped with a water distribution main pipe, and the water distribution main pipe is also connected to a perforated water distribution branch pipe; the water collection layer is a calcareous centimeter stone filler with a particle size of 30-50 mm wrapped with a water collection main pipe, and the water collection main pipe is connected to a perforated water collection branch pipe, and ventilation pipes are respectively connected to the water main pipe and the water collection main pipe in a vertically upward direction. Air is introduced through the ventilation pipe to increase the oxygen content and enhance the denitrification and phosphorus removal effect.

[0016] In the enhanced artificial wetland treatment system for tail water from nitrogen and phosphorus removal as described above, preferably, the thickness of the water distribution layer and the water collection layer is 25~40cm, and the slow-release carbon source composite functional filler layer is filled with a slow-release carbon source composite functional filler and has a thickness of 70~90cm; a water collection channel is also provided in the middle of the vertical subsurface flow wetland in the horizontal direction, and the water collection channel connects the water distribution main pipe and the water collection main pipe on the left and right sides.

[0017] Among them, the preparation method of the slow-release carbon source composite functional filler is to mix polyvinyl alcohol and sodium alginate in a mass ratio of 2:1, add water and mix well, keep the temperature at 53°C for 10 minutes, add starch, heat to 105°C and boil after mixing, keep boiling for 30 minutes, inject into the mold, coat the denitrifying thiobacillus solution on the material after cooling, add a 4.5% calcium chloride aqueous solution to the mold for solidification, let it stand and freeze it at -20°C for 24 hours, and then dry the filler at 37°C to obtain the slow-release carbon source composite functional filler.

[0018] The present invention provides a slow-release carbon source composite functional filler in the vertical submerged flow wetland, and provides a stable carbon source for denitrification through the slowly released carbon source, thereby solving the problem of insufficient carbon source in the denitrification process. By coating with denitrifying bacteria, excessive nitrate is converted into nitrogen and nitrogen dioxide and emitted into the air, thereby eliminating harmful substances such as nitrite nitrogen in the breeding pond, maintaining water quality stability, adjusting pH value, and reducing the harm caused by excessive nitrate to the water body, thereby playing the role of water quality regulation and bottom quality improvement.

[0019] As described above, in the enhanced artificial wetland treatment system for tail water from nitrogen and phosphorus removal, preferably, the horizontal subsurface flow wetland is provided with a slow-release carbon source composite functional filler area, a sulfide iron functional filler area and a water collection area in sequence in the horizontal direction, wherein the slow-release carbon source composite functional filler area is filled with a slow-release carbon source composite functional filler, the sulfide iron functional filler area is filled with sulfide iron functional filler, and the water collection area is filled with calcareous centimeter stone with a particle size of 30 to 50 mm; a water inlet is provided at the upper end of the slow-release carbon source composite functional filler area, and a water outlet is provided at the lower end of the water collection area.

[0020] In the above-mentioned enhanced nitrogen removal and phosphorus removal tailwater artificial wetland treatment system, preferably, an impermeable layer is provided at the bottom of the stabilization pond, and an enhanced phosphorus removal functional filler is provided above the impermeable layer.

[0021] In a preferred embodiment, floating island aquatic plants are planted in the front pond, and the floating island aquatic plants include floating leaf plants and emergent plants. The micron aerated vertical submerged flow wetland, vertical submerged flow wetland or / and horizontal submerged flow wetland are planted with emergent plants, and the pond bottom of the stabilization pond is planted with submerged plants and emergent plants; wherein the emergent plants are one or more of Elaeagnus scabra, Phragmites australis, Lythrum salicina, and Achyranthes bidentata; and the submerged plants are one or more of Vallisneria vulgaris, Potamogeton combotanthus, and Potamogeton crispus.

[0022] The present invention also provides an artificial wetland treatment method for enhanced denitrification and phosphorus removal tail water, which is carried out using the artificial wetland treatment system as described above, and the method includes: the tail water of the sewage treatment plant enters the front pond, the incoming water is preliminarily purified using an immersed bioreactor to remove COD and BODs ammonia nitrogen, and the impact of the incoming water on the next level of wetland is weakened; the effluent enters the micron aerated vertical submerged flow wetland, the micron aerated vertical submerged flow wetland is provided with air distribution measures to ensure the COD and ammonia nitrogen removal effect of the wetland under low temperature conditions, the effluent of the micron aerated vertical submerged flow wetland enters the vertical submerged flow wetland through a lifting system, and the TN and TP removal rates are enhanced through the synergistic effect of calcareous centimeter stone and slow-release carbon source composite functional filler; the effluent enters the horizontal submerged flow wetland through the lifting system, and the removal of nitrogen and phosphorus is enhanced through the slow-release carbon source composite functional filler and the sulfur iron functional filler, and the TN removal rate is further guaranteed; and finally enters the stabilization pond to maintain the water quality of the wetland effluent while further reducing the TP in the water. content to ensure the water quality of the effluent; wherein, when the inlet water temperature of the wetland is ≥10°C, the designed hydraulic retention time of the pre-pond is less than 1d; the hydraulic retention time of the micron aerated vertical subsurface flow wetland is 0.8h~1.5d; the hydraulic retention time of the vertical subsurface flow wetland is less than 1d; the hydraulic retention time of the horizontal subsurface flow wetland is 3h~1.5d; when the inlet water temperature of the wetland is <10°C, the retention time of each part can be extended as needed.

[0023] The stable pond provided by the present invention is also a water quality stabilization area, which is used to further deeply purify water quality and display ecological landscape. Submerged and emergent plants are planted in the pond. Through the selective and directional cultivation of aquatic plants, the biodiversity of vegetation is restored and expanded, and a stable and self-repairing wetland ecosystem is established. The pond uses submerged plants and phosphorus removal enhanced fillers to carry out long-term phosphorus control, remove the last residual total phosphorus, achieve deep purification of the water body, and ensure water quality. The purpose of natural ecological benign cycle and water purification is achieved by utilizing the recycling and self-repair characteristics of the natural system.

[0024] Micron aeration vertical subsurface flow wetland can ensure sufficient oxygen in the middle and bottom of the vertical subsurface flow constructed wetland through air distribution. Sufficient oxygen can promote nitrification reaction and inhibit denitrification reaction. When nitrogen-containing wastewater passes through the vertical subsurface flow constructed wetland, ammonia nitrogen can be quickly converted into nitrate and nitrite. Nitrates and nitrites then enter the vertical subsurface flow wetlands, where emergent plants are planted. The stems of emergent plants grow upright in the water, and the roots grow in the bottom mud. First, emergent plants themselves have a certain ability to adsorb and enrich nitrates and nitrites, and can directly remove such pollutants. Secondly, emergent plants have well-developed root systems and a certain oxygen transport capacity. The oxygen concentration in the root zone is high, and the remaining ammonia nitrogen that has not reacted completely before can be converted into nitrates and nitrites through nitrification reactions. Finally, due to the particularity of emergent plants, the root zone is in an oxygen-rich state, while areas farther away from the root zone are in an oxygen-deficient state, and areas farther away are in a completely anaerobic state. This continuous aerobic-anoxic-anaerobic state can ensure the nitrification-denitrification reaction, thereby effectively reducing the total nitrogen content.

[0025] (III) Beneficial effects

[0026] The beneficial effects of the present invention are:

[0027] The artificial wetland treatment system for tail water enhanced denitrification and phosphorus removal under low temperature conditions provided by the present invention comprises a primary purification area, a deep purification area and a water quality stabilization area, wherein the primary purification area is provided with a pre-pond, the deep purification area is provided with a micron aerated vertical subsurface wetland, a vertical subsurface wetland, and a horizontal subsurface wetland in sequence, and the water quality stabilization area is provided with a stabilization pond. The system effectively optimizes the process structure combination, improves the system dissolved oxygen level, increases the carbon source utilization efficiency, and breaks through the artificial wetland sustainable operation function enhanced water quality purification technology, and significantly improves the pollutant removal efficiency and operation stability of the artificial wetland water quality purification technology. It has the advantages of reasonable structural design, uniform water distribution and water collection, strong synchronous denitrification and phosphorus removal capabilities, not easy to block and good winter operation effect, and can significantly improve the denitrification and phosphorus removal capabilities of the tail water artificial wetland system, thereby ensuring the sewage purification effect, and simple operation and maintenance.

[0028] The artificial wetland treatment system for enhanced nitrogen and phosphorus removal tail water provided by the present invention effectively enhances the deep denitrification process of low C / N ratio sewage treatment plant tail water by optimizing pretreatment measures, enhancing process layout of measures, and matching functional equipment, and has the characteristics of synergistic effect of pollution reduction and phosphorus reduction; it also increases the level of dissolved oxygen in the wetland to promote nitrification reaction, and effectively slows down the clogging of fillers, saves land, and improves the purification efficiency per unit area, and has the advantages of low investment cost, etc.

[0029] The enhanced denitrification and phosphorus removal tail water artificial wetland treatment system provided by the present invention adopts a slow-release carbon source composite functional filler, which is made by fusing natural materials such as polyvinyl alcohol, sodium alginate, starch, etc., has a high specific surface area, is convenient for microorganisms to attach and grow in large quantities, provides a carrier for the survival of denitrifying microorganisms, and provides sufficient carbon source for the denitrification biochemical reaction process.

[0030] The enhanced denitrification and phosphorus removal tail water artificial wetland treatment system provided by the present invention is particularly suitable for sewage treatment under low temperature conditions. It adopts an immersed bioreactor to enhance the nitrification function of the system, has a good removal effect on organic pollutants and ammonia nitrogen in the water, and reduces the impact load of pollutants on the next-level wetland; in winter or at low temperatures, microbial agents can be added to the immersed bioreactor to effectively remove ammonia nitrogen and COD; an integrated air / water distributor is set in the micron aerated vertical submerged flow wetland to evenly distribute water, and the comprehensive effects of the matrix, microorganisms and plants in the wetland are used for deep purification, thereby improving the decomposition efficiency of organic matter and the nitrification capacity of ammonia nitrogen. At the same time, under low temperature conditions in winter, increasing aeration can improve the flow state of water, prevent freezing, increase the concentration of dissolved oxygen, and promote nitrification, so that the system has a better enhanced denitrification and phosphorus removal effect.

[0031] The present invention also adopts sulfide-iron functional filler, which realizes efficient denitrification and denitrification by combining autotrophic denitrification on the basis of heterotrophic denitrification reaction, realizes efficient removal of nitrate in low carbon-nitrogen ratio wastewater, reduces the amount of carbon source added in the denitrification process; quickly decomposes biomass, efficiently degrades and absorbs ammonia nitrogen, consumes excess nitrite and nitrate, and improves nitrification and denitrification efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the transverse section of the front pond;

[0033] Figure 2 This is a schematic diagram of the structure of a micron-aerated vertical subsurface flow wetland;

[0034] Figure 3 This is a transverse cross-section of a micron-aerated vertical subsurface flow wetland;

[0035] Figure 4 This is a schematic diagram of the structure of a vertical subsurface flow wetland;

[0036] Figure 5 It is a transverse cross-section of a vertical subsurface flow wetland;

[0037] Figure 6 This is a schematic diagram of the structure of a horizontal subsurface flow wetland;

[0038] Figure 7 This is a transverse cross-section of a horizontal subsurface flow wetland;

[0039] Figure 8This is a transverse cross-section of the stabilization pond;

[0040] Fig. 9 The present invention is a schematic diagram of the process flow of a preferred enhanced denitrification and phosphorus removal tail water wetland treatment method.

[0041] [Description of Reference Numerals]

[0042] 1: Main water inlet pipe;

[0043] 2: Pre-pond;

[0044] 3: Submerged bioreactor;

[0045] 4: Air pipe;

[0046] 5: Inlet channel;

[0047] 6: Anti-seepage layer;

[0048] 7: Calcium centimeter stone filler layer;

[0049] 8: Integrated air / water distributor;

[0050] 9: filter material layer;

[0051] 10: First water collection channel;

[0052] 11: Drainage channel;

[0053] 12: water channel layout;

[0054] 13: water distribution layer;

[0055] 14: water pipes;

[0056] 15: Slow-release carbon source composite functional filler layer;

[0057] 16: water collection layer;

[0058] 17: Water pipe and ventilation pipe;

[0059] 18: water collection pipe;

[0060] 19: water collecting pipe vent pipe;

[0061] 20: Second water collection channel;

[0062] 21: Slow-release carbon source composite functional filler area;

[0063] 22: Sulfur iron functional filler area;

[0064] 23: Catchment area;

[0065] 24: water inlet;

[0066] 25: water outlet;

[0067] 26: Outlet channel;

[0068] 27: Stabilization pond. DETAILED DESCRIPTION

[0069] The process design principle of the wetland system provided by the present invention is comprehensively determined based on the characteristics of the influent water quality, the size of the site, the necessary water landscape and the water purification function. It includes multiple units such as the primary purification area (pre-pond), the deep purification area (micron aerated vertical subsurface wetland, vertical subsurface wetland, horizontal subsurface wetland) and the water quality stabilization (stabilization pond) area, which can complete the transformation and removal of organic matter, and at the same time create the functional areas of nitrification, denitrification biochemical reactions and phosphorus removal and precipitation, thereby improving the self-purification and self-repair capabilities of the water body. It has the characteristics of ecological nature, high efficiency and stability, simple maintenance and economic practicality.

[0070] In view of the technical difficulties such as low water temperature, low microbial activity, small footprint and high hydraulic load in winter, the present invention adopts the following intensified process treatment units: an immersed bioreactor and a micron aerated vertical submerged flow wetland are adopted in the front-end; a filler-enhanced treatment unit is provided in the vertical submerged flow wetland and the horizontal submerged flow wetland, and heterotrophic denitrification filler and autotrophic denitrification filler are adopted for deep nitrogen and phosphorus removal; a phosphorus removal-enhanced filler is adopted in the water quality stabilization unit; and under low temperature conditions in winter, high-efficiency biological agents are added in the primary purification area and the deep purification area to improve the treatment effect in winter.

[0071] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0072] Example 1

[0073] The present invention provides an artificial wetland treatment system for strengthening the denitrification and phosphorus removal of tail water, which includes a pre-pond, a micron aerated vertical submerged flow wetland, a vertical submerged flow wetland, a horizontal submerged flow wetland and a stabilization pond arranged in sequence, wherein a water inlet pipe is provided at the front end of the pre-pond, an immersion bioreactor is provided in the pre-pond, which is used to purify the incoming water and remove organic pollutants and ammonia nitrogen, and a water distribution channel and a triangular weir are provided at the end of the pre-pond. A water inlet channel is provided at the front end of the micron aerated vertical submerged flow wetland, and the water inlet channel is adjacent to the triangular weir at the front end. The micron aerated vertical submerged flow wetland is an upward flow vertical submerged flow wetland, and an integrated air / water distributor is provided at the bottom thereof, which is used to evenly distribute water and air, so that water and air flow upward from the bottom of the wetland through the micron aerated vertical submerged flow wetland in the same way, the water inlet channel is connected to the water distribution pipe in the integrated air / water distributor, and an outlet channel is provided at the end of the micron aerated vertical submerged flow wetland. A water distribution channel is set between the micron-aerated vertical subsurface flow wetland and the vertical subsurface flow wetland, and the outlet channel is set up next to the water distribution channel; a calcareous centimeter stone area and a slow-release carbon source composite functional filler are set up in the vertical subsurface flow wetland to enhance nitrogen and phosphorus removal, and the water distribution channel is connected to the calcareous centimeter stone area through a pump. The terminal drainage channel of the vertical subsurface flow wetland is set up next to the inlet channel of the horizontal subsurface flow wetland. The horizontal subsurface flow wetland is equipped with a slow-release carbon source composite functional filler and a sulfur iron functional filler in the horizontal direction. The front end of the horizontal subsurface flow wetland is equipped with an inlet channel and the end is equipped with an outlet channel; the outlet channel is connected to the stabilization pond, and the stabilization pond is paved with enhanced phosphorus removal functional fillers, and the bottom of each part is provided with an anti-seepage layer. The following is a detailed introduction to the settings of each part:

[0074] 1. Pre-pond

[0075] The tail water of the sewage treatment plant enters the front pond through the main inlet pipe (HDPE casing DN900), such as Figure 1 As shown, the main water inlet pipe 1 enters the front pond 2 from the bottom of the pond. An immersed bioreactor 3 is arranged in the front pond 2. The immersed bioreactor is equipped with phosphorus removal filter material, filler, aeration system and alkalinity adjustment integrated facilities. The filler is flexible filler. The aeration system controls the aeration of the reactor through an air flow meter (F02-1A~C, DN200, thermal gas mass flow meter, Q=0~1200m / h, 4~20mA signal output) and an air regulating valve; alkalinity adjustment is used to adjust the pH value in the immersed bioreactor.

[0076] The submerged bioreactor can be provided with multiple groups, and the air pipes 4 between the multiple groups of reactors are connected. There is also an air regulating valve on the air pipe 4. The size of a single reactor group is 9x9m, H=2.3m, and it can be fixed with a steel bracket, a floating ball and a counterweight. The diameter of the connecting hose between each set of reactors is 32 mm, the diameter of the aeration branch pipe is 125 mm, and the air regulating device is DV02-1A~C, DN200mm, and an electric diamond air regulating valve. Floating island aquatic plants are planted above the submerged bioreactor. The roots of floating island aquatic plants release oxygen, increase the dissolved oxygen in the water body, and absorb nitrogen and phosphorus in the sewage as nutrient elements, which plays a role in intercepting and removing pollution, and also has the function of beautifying the environment.

[0077] The front pond is used as the preliminary purification treatment process at the front end of the wetland. It uses floating leaf plants, emergent plants, submerged bioreactors and aeration systems to purify the incoming water. The microporous aeration device is provided to strengthen the oxidation function of the system, maintain the oxygen-rich conditions of the system, and use the built-in chain phosphorus removal medium to strengthen the phosphorus removal capacity. The aerobic microorganisms on the surface of the flexible filler suspended under the submerged bioreactor oxidize and decompose the organic pollutants in the polluted water, promote the ammonia nitrogen nitrification process and the organic phosphorus mineralization process. The root oxygen secretion capacity and absorption of nutrients by the aquatic plants growing on the reactor also play a purifying role. It can be seen that the submerged bioreactor has the function of enhancing the nitrification of the system, has a good removal effect on organic pollutants and ammonia nitrogen in the water, and reduces the impact load of pollutants on the next level of wetlands. In winter or at low temperatures, microbial agents can also be added to the submerged bioreactor.

[0078] Microbial agents can be commercially available products. Low-temperature resistant functional agents are composite microbial agents developed for low-temperature wastewater treatment. The agents are prepared by selecting functional strains that are resistant to low temperatures and can efficiently degrade ammonia nitrogen and COD from nature, and compounding them with specific carriers, enzymes and nutrients in appropriate proportions. They can rapidly reproduce and produce low-temperature functional biologically active substances under low-temperature conditions. They are composite microbial agents that can remove ammonia nitrogen and COD under aerobic conditions.

[0079] 2. Micron Aeration Vertical Subsurface Flow Wetland

[0080] In view of the shortcomings of traditional artificial wetlands, such as low nitrification load and easy clogging, an integrated air / water distributor is installed at the bottom of the micron aerated vertical submerged flow wetland to evenly distribute water and air, so that water vapor flows upward from the bottom of the wetland through the micron aerated vertical submerged flow wetland. This technology combines micro-aeration technology to improve the oxygen distribution in the wetland system, forming a strong oxidizing environment, and using the combined effects of the matrix, microorganisms, and plants in the wetland for deep purification, improving the decomposition efficiency of organic matter and the nitrification capacity of ammonia nitrogen, minimizing the organic matter residue inside the wetland filler and reducing the risk of filler clogging. The specific structure is as follows Figure 2 and Figure 3As shown, the water outflow from the front pond enters the water inlet channel 5 of the micron aerated vertical subsurface wetland through a triangular weir set in the water distribution channel. The micron aerated vertical subsurface wetland is an upward flow vertical subsurface wetland, and an anti-seepage layer 6, a calcium centimeter stone filler layer 7 (with an integrated air / water distributor 8) and a filter layer 9 are set from bottom to top at the bottom. The depth of the water inlet channel at the front end is submerged in the calcium centimeter stone filler layer to reach the anti-seepage layer. A first water collection channel 10 is set in the middle of the micron aerated vertical subsurface wetland. The water distribution pipe in the calcium centimeter stone filler layer 7 is connected to the first water collection channel 10. A drainage channel 11 is set at the end of the micron aerated vertical subsurface wetland. The water distribution pipe is connected to the drainage channel 11. The calcium centimeter stone filler layer wraps the water distribution pipe and the air distribution pipe. The filter layer 9 can also be used to mitigate the water flow speed.

[0081] Among them, the integrated air / water distributor includes interconnected axial polymer gas distribution pipes, flexible micron gas diffusion surfaces, gas volume magnetic control components and water distribution pipes for aeration. A one-way gas-water isolation membrane core is provided in the axial polymer gas distribution pipe. The flexible micron gas diffusion surface is made of imported new polymer materials, the aeration pressure is lower than 0.4Kpa, and the diameter of the gas diffusion surface is φ30um-60µm. The service area A of the integrated air / water distributor is 1300-1700㎡ / set, and the polymer gas distribution pipes need to be wrapped with red bricks for protection. The water distribution pipes are evenly arranged. It should be noted that the bottom water distribution pipes need to be wrapped with red bricks to prevent the pipes from being deformed and damaged due to the extrusion of the filler. The filter material layer is a calcareous centimeter stone filler with a particle size of 20~40mm. The upper part of the wetland is planted with emergent plants, which can be selected from lily, variegated reed, reed, loosestrife, water plantain, etc. An air branch pipe and an air down pipe that are interconnected are also provided above the filter material layer. The diameter of the air branch pipe is 150 mm, and the diameter of the air down pipe is 85 mm, which are used for aeration.

[0082] The integrated air / water distributor evenly distributes water, and the water vapor flows upward from the bottom of the wetland through the micron aerated vertical flow wetland, forming a strong oxidation environment. At the same time, the filler converts most of the difficult-to-degrade organic matter in the water into easily degradable organic matter. The comprehensive effects of the matrix, microorganisms, and plants in the wetland are used for deep purification, improving the decomposition efficiency of organic matter and the nitrification capacity of ammonia nitrogen. At the same time, under low temperature conditions in winter, increasing aeration can improve the flow state of water, prevent freezing, increase the concentration of dissolved oxygen, and promote nitrification.

[0083] 3. Vertical subsurface flow wetland

[0084] The vertical subsurface flow wetland in the present invention is mainly used to enhance the denitrification and phosphorus removal. The denitrification functional filler can achieve efficient denitrification and the dephosphorus removal effect can be enhanced by the calcium centimeter stone. Figure 4As shown, the front end of the vertical subsurface flow wetland is provided with a water distribution channel 12, calcareous centimeter stone filler, and the middle of the vertical subsurface flow wetland is provided with a water distribution layer, a slow-release carbon source composite functional filler, and a water collection layer from bottom to top; wherein, the slow-release carbon source composite functional filler layer is filled with a slow-release carbon source composite functional filler, and the thickness is 70-90cm; the thickness of the water distribution layer and the water collection layer is 25-40cm, the water distribution layer is a calcareous centimeter stone filler with a particle size of 30-50mm wrapped with a water distribution main pipe, and the water distribution main pipe is also connected with a perforated water distribution branch pipe; the water collection layer is a calcareous centimeter stone with a particle size of 30-50mm wrapped with a water collection main pipe, and the water collection main pipe is connected with a perforated water collection branch pipe, and ventilation pipes are connected vertically upward on the water main pipe and the water collection main pipe. Air is introduced through the ventilation pipe to increase the oxygen content and strengthen the denitrification and phosphorus removal effect.

[0085] The first main reaction area of ​​the vertical subsurface flow wetland is an upward flow vertical subsurface flow wetland, with a water distribution system at the bottom and a water collection system at the top, such as Figure 5 As shown, from bottom to top, they are: an anti-seepage layer 6, a water distribution layer 13 (a water distribution pipe 14 is arranged in the water distribution layer, and the water distribution pipe comprises a UPVC-wrapped water distribution main pipe with a thickness of 30-50 mm and interconnected water distribution branch pipes, the diameter of the water distribution main pipe is 200 mm (dn200), and the diameter of the water distribution branch pipe (perforated pipe) is 100 mm (dn100)), a slow-release carbon source composite functional filler layer 15 is filled with a slow-release carbon source composite functional filler, a water collection layer 16 (the UPVC water collection main pipe is wrapped with calcareous centimeter stone with a particle size of 30-50 mm, the water collection main pipe is dn200, and the water collection branch pipe (perforated pipe) is dn100), and the water collection main pipe is connected to the water collection branch pipe; the water level of the outlet water is adjusted by rotating the outlet pipe. Specifically, the water distribution layer is paved with calcium centimeter stone filler with a particle size of 30-50 mm and the water distribution pipe is wrapped. The water distribution pipe includes a water distribution main pipe connected to a perforated water distribution branch pipe; in the vertical direction, the water distribution main pipe is connected to a water distribution pipe vent pipe 17 leading to the outside air. The water collection layer 16 also uses calcium centimeter stone filler with a particle size of 30-50 mm to wrap the water collection main pipe 18, and the water collection main pipe 18 is connected to a perforated water collection branch pipe; in the vertical direction, the water collection main pipe is provided with a water collection pipe vent pipe 19 connected to the outside air. The structure of the reinforced filler area is the same as that of the main reaction area, except that the functional filler is a calcium functional filler, which can be a commercially available product. A second water collection channel 20 can be provided in the middle of the main reaction area, and the water collection main pipe 18 and the water distribution main pipe are both connected to the second water collection channel 20.

[0086] The preparation of the slow-release carbon source composite functional filler is to mix polyvinyl alcohol and sodium alginate in a mass ratio of 2:1, add 150ml of water and mix well, heat in a water bath at a constant temperature of 53°C for 10 minutes, add starch in a mass ratio of polyvinyl alcohol to starch of 1:3, heat to 105°C and keep boiling for 30 minutes after mixing, and then inject the material into the mold while it is hot; when the temperature of the material in the mold naturally drops to 45°C, apply the denitrifying thiobacillus solution on the material, and then add a 4.5% calcium chloride aqueous solution to the mold for solidification, and stand to obtain a preliminary formed filler; freeze the preliminary formed filler at -20°C for 24 hours, so that the calcium chloride solution effectively cooperates with the polyvinyl alcohol-sodium alginate solution for low-temperature cross-linking, and then dry the filler at 37°C to obtain the slow-release carbon source composite functional filler. The slow-release carbon source composite functional filler has a better effect of stabilizing the slow-release carbon source, and the added denitrifying thiobacillus increases the denitrification rate and improves the denitrification efficiency.

[0087] 4. Horizontal subsurface flow wetlands

[0088] Horizontal subsurface flow wetlands are used to further reduce the concentrations of various pollutants. The anoxic and anaerobic environmental conditions of horizontal subsurface flow wetlands and denitrifying fillers can achieve efficient denitrification and denitrification. Slow-release carbon source composite functional fillers are arranged in the front section of the horizontal subsurface flow wetlands to carry out anoxic denitrification and denitrification; sulfide-iron functional fillers are arranged in the back section of the horizontal subsurface flow wetlands to carry out autooxic denitrification and denitrification, and simultaneously achieve synchronous phosphorus removal to ensure the TN index of the effluent water quality.

[0089] The water distribution / collection of the horizontal subsurface flow wetland adopts the form of perforated pipes. The water distribution system is located at the upper part of the wetland water inlet end, and the water collection system is located at the lower part of the wetland water outlet end. The filler layer (slow-release carbon source composite functional filler and sulfur iron functional filler and other fillers are mixed. The slow-release carbon source composite functional filler can be prepared by the above method. The sulfur iron functional filler has a particle size of 5~15mm and a bulk density of 1.0~1.1g / cm 3 , porosity of 45-55%, high physical strength), and the upper part of the wetland is planted with emergent plants, which can be selected from spatholobi, variegated reed, loosestrife, water plantain, etc. The water level of the horizontal subsurface flow wetland is adjusted by rotating the outlet pipe.

[0090] Specifically, Figure 6 and Figure 7As shown, the bottom layer of the horizontal submerged flow wetland is provided with an impermeable layer 6, and a slow-release carbon source composite functional filler area 21, a sulfide iron functional filler area 22 and a water collection area 23 are provided in the horizontal direction. The slow-release carbon source composite functional filler area 21 is filled with a slow-release carbon source composite functional filler, the sulfide iron functional filler area 22 is filled with a sulfide iron functional filler, and the water collection area 23 is filled with calcareous centimetre stone with a particle size of 30-50 mm; a water inlet 24 is provided at the upper end of the slow-release carbon source composite functional filler area, a water outlet 25 is provided at the lower end of the water collection area, an inlet channel is provided at the front end of the horizontal submerged flow wetland, and an outlet channel 26 is provided at the end.

[0091] The water in the wetland is mainly the tail water of sewage treatment plants. There are few carbon sources in the water that can provide denitrification. Heterotrophic denitrifying bacteria need external carbon sources to achieve efficient denitrification and denitrification reactions. Therefore, the denitrification enhancement filler considers using a slow-release carbon source composite functional filler as the carbon source for the biochemical reaction of heterotrophic denitrifying bacteria and the source of denitrifying bacteria. It can economically and effectively solve the problem of carbon source supply for NO3-N denitrification in the tail water of urban sewage treatment plants; at the same time, combined with sulfur-iron functional fillers, on the basis of heterotrophic denitrification reaction, combined with autotrophic denitrification, efficient denitrification and denitrification are achieved to ensure that the total nitrogen in the effluent meets the standard.

[0092] Traditional wetlands have poor denitrification capacity (TN). The wetlands lack carbon sources, which leads to the obstruction of the denitrification process and the accumulation of large amounts of nitrate nitrogen, resulting in a low total nitrogen removal rate, easy saturation of the filler, and a short duration of action; they occupy a large area.

[0093] The denitrification and denitrification of the slow-release carbon source composite functional filler accounts for 60-86% of the total nitrogen removal, which is the main way to denitrify polluted water bodies. Denitrifying bacteria (denitrifying thiobacillus) use the rich organic carbon and inorganic carbon in the denitrification carbon source material as a carbon source, complete microbial metabolism when inorganic matter is used as an electron donor for nitrate nitrogen reduction, and reduce the nitrate nitrogen in the nitrate nitrogen polluted water body to nitrogen gas. The slow-release carbon source composite functional filler is made of natural materials such as polyvinyl alcohol, sodium alginate, and starch. It has a high specific surface area, which is convenient for microorganisms to attach and grow in large quantities, providing a carrier for the survival of denitrifying microorganisms and providing sufficient carbon source for the denitrification biochemical reaction process. The filler can be set as a porous sphere and placed on the bottom of the water or the wetland filler layer. Even if it is covered with rich microorganisms, it will not affect the slow release efficiency of the carbon source; at the same time, hydraulic scouring and friction between materials accelerate the renewal rate of the attached bacterial community, which is conducive to improving space utilization and denitrification rate.

[0094] The present invention also adopts sulfide-iron functional filler, and realizes efficient denitrification and denitrification by combining autotrophic denitrification on the basis of heterotrophic denitrification reaction, realizes efficient removal of nitrate in low carbon-nitrogen ratio wastewater, reduces the amount of carbon source added in the denitrification process; quickly decomposes biomass, efficiently degrades and absorbs ammonia nitrogen, consumes excess nitrite and nitrate, and improves nitrification and denitrification efficiency.

[0095] (V) Stabilization pond

[0096] like Figure 8 As shown, an impermeable layer 6 is provided at the bottom of the stabilization pond 27, on which a functional filler for enhanced phosphorus removal is laid, which may be calcareous centimetre stone; submerged plants and emergent plants are planted at the bottom of the pond, and the submerged plants mainly include Vallisneria, Potamogeton, and Water Chestnut.

[0097] As a water quality stabilization area, the main function of the stable pond is to deeply purify water quality and display ecological landscape. Submerged and emergent plants are planted in the pond. Through the selective and directional cultivation of aquatic plants, the biodiversity of vegetation is restored and expanded, and a stable and self-repairing wetland ecosystem is established. The submerged plants and phosphorus removal enhanced fillers in the pond carry out long-term phosphorus control, remove most of the total phosphorus, achieve deep purification of the water body, and ensure water quality. The recycling and self-repair characteristics of the natural system are used to achieve the purpose of natural ecological benign circulation and water purification.

[0098] The process flow of the system, such as Fig. 9 As shown in the figure, the tailwater effluent of the sewage treatment plant is led into the pre-pond. The pre-pond mainly uses an immersed bioreactor to preliminarily purify the incoming water, remove COD and BODs ammonia nitrogen, and weaken the impact of the incoming water on the next-level wetland; the effluent enters the micron-aerated vertical submerged flow wetland. The micron-aerated vertical submerged flow wetland is equipped with aeration measures to ensure the COD and ammonia nitrogen removal effect of the wetland under low temperature conditions. The effluent of the micron-aerated vertical submerged flow wetland enters the vertical submerged flow wetland through the lifting system, with the removal of nitrogen and phosphorus as the main goal. Through the synergistic effect of aquatic plants, attached microorganisms and characteristic fillers such as calcium centimeter stone and slow-release carbon source composite functional fillers, the TN and TP removal rates are enhanced; the effluent enters the horizontal submerged flow wetland through the lifting system, and the removal of nitrogen and phosphorus is enhanced through the slow-release carbon source composite functional filler and sulfur iron functional filler, further ensuring the removal rate of TN; and finally enters the stabilization pond, which mainly serves as a wetland water quality stabilization area and can build a complete water ecosystem with aquatic plants and animals to maintain the water quality of the wetland effluent while further reducing TP in the water. content to ensure the effluent quality; the last part of the effluent enters the reclaimed water reuse treatment unit, and the other part is lifted and discharged into the river for ecological water replenishment. Among them, when in North China, when the inlet water temperature of the wetland is ≥10°C, the hydraulic retention time of the pre-pond design is less than 1d; the hydraulic retention time of the micron aerated vertical subsurface wetland is 0.8h~1.5d; the hydraulic retention time of the vertical subsurface wetland is less than 1d; the hydraulic retention time of the horizontal subsurface wetland is 3h~1.5d, and the hydraulic retention time of the stabilization pond is less than 1d; when the inlet water temperature of the wetland is <10°C, the retention time of each part can be extended as needed.

[0099] Example 2

[0100] This example is based on Example 1. The site is located in the southwest of the intersection of Taihang Street and Dongpo Road in Luancheng District, southeast of Shijiazhuang City, Hebei Province, with a total area of ​​about 100 acres. It is located at the source of the ancient Yunliang River and is carried out according to Example 1. Due to the lack of water resources in the ancient Yunliang River, the upper reaches of the river are dry. Therefore, the water diversion project is used to divert water to the wetland project for purification to replenish the ecological water of the ancient Yunliang River. The total design scale of the water diversion project is 30,000 m 3 / d. The tail water of the sewage plant is used as the water source, the inlet water temperature of the wetland is ≥10°C, the inlet water quality complies with the Class A standard of the Municipal Wastewater Discharge Standard (GB18918-2002), the total residence time is about 1.3d, and the efficient treatment process of Example 1 is adopted to ensure that the effluent water quality meets the standard. The specific process of each part is shown in Table 1, and the treatment effect is shown in Table 2.

[0101] Table 1 Some process parameters of each processing unit

[0102]

[0103] Comparative Example

[0104] Compared with the same period last year, the Shangcai County sewage treatment plant tailwater artificial wetland deep treatment project adopts existing technology biological enhanced storage tanks, vertical flow artificial wetlands, clear water ecosystem three-level ponds, pump rooms, fan rooms, management rooms and related supporting pipelines.

[0105] The Laolong River artificial wetland project in Anci District, Langfang City adopts the existing technology of "sedimentation pond + artificial wetland (subsurface wetland + surface wetland) + water conservancy regulation" as the main process. The optimal parameters are designed according to the hydraulic load and pollutant concentration of the Laolong River, and the types and proportions of wetland plants and fillers are selected to achieve an efficient and economic combination of water quality essence.

[0106] The projects implemented in Example 2 of the present invention are compared with the above two, and the results are shown in Table 2.

[0107] Table 2 Comparison results

[0108]

[0109] It can be seen from the above that, compared with similar projects, the hydraulic load of the treatment system provided by the present invention is 1 to 2 times higher, which greatly saves floor space; at the same time, the investment per ton of water in the project is lower than that of similar projects.

[0110] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any person skilled in the art can use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. An artificial wetland treatment system for enhanced nitrogen and phosphorus removal tail water, characterized in that: It includes a pre-pond, a micron aerated vertical submerged flow wetland, a vertical submerged flow wetland, a horizontal submerged flow wetland and a stabilization pond, wherein the pre-pond is provided with an immersion bioreactor for purifying incoming water and removing organic pollutants and ammonia nitrogen; an integrated air / water distributor is provided at the bottom of the micron aerated vertical submerged flow wetland for evenly distributing water and air, so that water vapor flows upward from the bottom of the wetland through the micron aerated vertical submerged flow wetland, and an air branch pipe for aeration is also provided above the micron aerated vertical submerged flow wetland; the vertical submerged flow wetland is provided with a slow-release carbon source composite functional filler and calcareous centimeter stone for strengthening nitrogen and phosphorus removal; a slow-release carbon source composite functional filler and sulfide iron functional filler are provided in the horizontal direction of the horizontal submerged flow wetland, and an outlet channel is provided at the end of the horizontal submerged flow wetland; the outlet channel is connected to the stabilization pond; The vertical subsurface flow wetland is provided with a water distribution layer, a slow-release carbon source composite functional filler, and a water collection layer in order from bottom to top; the water distribution layer includes a water distribution main pipe wrapped with a calcareous centimeter stone filler with a particle size of 30-50 mm, and the water distribution main pipe is connected with a perforated water distribution branch pipe; the slow-release carbon source composite functional filler layer is filled with a slow-release carbon source composite functional filler with a thickness of 70-90 cm; the water collection layer includes a water collection main pipe wrapped with a calcareous centimeter stone filler with a particle size of 30-50 mm, and the water collection main pipe is connected with a perforated water collection branch pipe, and the water distribution main pipe and the water collection main pipe are respectively connected with ventilation pipes in the vertical upward direction; The horizontal subsurface flow wetland is provided with a slow-release carbon source composite functional filler area, a sulfide iron functional filler area and a water collection area in the horizontal direction, wherein the slow-release carbon source composite functional filler area is filled with a slow-release carbon source composite functional filler, the sulfide iron functional filler area is filled with a sulfide iron functional filler, and the water collection area is filled with calcareous centimeters with a particle size of 30-50 mm; a water inlet is provided at the upper end of the slow-release carbon source composite functional filler area, and a water outlet is provided at the lower end of the water collection area; an impermeable layer is provided at the bottom of the stabilization pond, and an enhanced phosphorus removal functional filler is provided above the impermeable layer; The preparation method of the slow-release carbon source composite functional filler is as follows: polyvinyl alcohol and sodium alginate are mixed in a mass ratio of 2:1, water is added and mixed, the mixture is kept at a constant temperature of 53°C for 10 minutes, starch is added, the mixture is heated to 105°C and boiled, and the boiling state is kept for 30 minutes, the mixture is injected into a mold, a denitrifying thiobacillus solution is coated on the material after cooling, and a calcium chloride aqueous solution with a mass concentration of 4.5% is added to the mold for solidification, the mixture is allowed to stand and then frozen at -20°C for 24 hours, and then the filler is dried at 37°C to obtain the slow-release carbon source composite functional filler; The front end of the pre-pond is provided with a water inlet pipe, and the end of the pre-pond is provided with a water distribution channel and a triangular weir; the submerged bioreactor is provided with an integrated facility of chain phosphorus removal medium, filler, aeration system, and alkalinity adjustment, and the filler is a flexible filler, which is conducive to aerobic microorganisms to oxidize and decompose organic pollutants in polluted water bodies, promote ammonia nitrogen nitrification process and organic phosphorus mineralization; the aeration system is provided with an air flow meter and an air regulating valve for controlling the aeration of the reactor; when it is winter or under low temperature conditions, a low-temperature resistant functional bacterial agent is added to the filler; The micron aerated vertical subsurface flow wetland is provided with a calcareous centimeter stone filler layer and a filter material layer from bottom to top; wherein the calcareous centimeter stone filler layer uses calcareous centimeter stone with a particle size of 30-50 mm, an integrated air / water distributor is placed in the calcareous centimeter stone filler layer, and the filter material layer uses calcareous centimeter stone with a particle size of 20-40 mm for effective phosphorus removal, and an air branch pipe for aeration is also provided above the filter material layer.

2. The artificial wetland treatment system according to claim 1, characterized in that: The submerged bioreactor is provided with a plurality of groups, and the aeration systems between the groups are connected through air pipes.

3. The artificial wetland treatment system according to claim 1, characterized in that: The integrated air / water distributor comprises a polymer air distribution pipe, a flexible micron gas diffusion surface, an air volume magnetic control component and a water distribution pipe for interconnecting with the aeration device, and the water distribution pipe is evenly distributed in the calcareous centimeter stone filler layer.

4. The artificial wetland treatment system according to claim 1, characterized in that: The thickness of the water distribution layer and water collection layer of the vertical subsurface flow wetland is 25~40cm; there is also a water collection channel in the middle of the vertical subsurface flow wetland in the horizontal direction, which connects the water distribution main pipe and water collection main pipe on the left and right sides.

5. The artificial wetland treatment system according to claim 1, characterized in that: Floating island aquatic plants are planted in the front pond, and the floating island aquatic plants include floating leaf plants and emergent plants; the micron aerated vertical submerged flow wetland, vertical submerged flow wetland or / and horizontal submerged flow wetland are planted with emergent plants, and the pond bottom of the stabilization pond is planted with submerged plants and emergent plants; wherein the emergent plants are one or more of the following: hydrangea, variegated reed, phragmites australis, loosestrife and water plantain; and the submerged plants are one or more of the following: Vallisneria vulgaris, Potamogeton combreta and Potamogeton crispus.

6. A method for enhanced nitrogen and phosphorus removal tail water artificial wetland treatment, characterized in that: The method is carried out by using the artificial wetland treatment system described in any one of claims 1 to 5, and the method includes: the tail water of the sewage treatment plant enters the front pond, and the incoming water is preliminarily purified by using an immersed bioreactor to remove COD, BOD and ammonia nitrogen, and weaken the impact of the incoming water on the next level of wetland; the effluent enters the micron aerated vertical submerged flow wetland, and the micron aerated vertical submerged flow wetland is provided with air distribution measures to ensure the COD and ammonia nitrogen removal effect of the wetland under low temperature conditions. The effluent of the micron aerated vertical submerged flow wetland enters the vertical submerged flow wetland through the lifting system, and the TN and TP removal rates are enhanced through the synergistic effect of calcareous centimeter stone and slow-release carbon source composite functional filler; the effluent enters the horizontal submerged flow wetland through the lifting system, and the removal of nitrogen and phosphorus is enhanced by the slow-release carbon source composite functional filler and the sulfur iron functional filler, and the TN removal rate is further guaranteed; and finally enters the stabilization pond to maintain the water quality of the wetland effluent while further reducing the TP in the water. content to ensure the water quality of the effluent; wherein, when the inlet water temperature of the wetland is ≥10°C, the designed hydraulic retention time of the pre-pond is less than 1d; the hydraulic retention time of the micron aerated vertical subsurface flow wetland is 0.8h~1.5d; the hydraulic retention time of the vertical subsurface flow wetland is less than 1d; the hydraulic retention time of the horizontal subsurface flow wetland is 3h~1.5d; when the inlet water temperature of the wetland is <10°C, the retention time of each part can be extended as needed.

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