Layered function enhanced artificial wetland system for sewage treatment

Abstract

The invention discloses a layered function enhanced artificial wetland system for sewage treatment. The layered function enhanced artificial wetland system comprises an ecological surface layer area, an enhanced biological reaction area, a composite separation layer and a deep filtration area which are sequentially arranged from top to bottom, emergent aquatic plants are planted in the ecological surface layer area, the enhanced biological reaction area is filled with light suspended filler with the particle size of 2-4 mm, nitrifying bacteria and denitrifying bacteria are mixed in the light suspended filler, and the deep filtration area is filled with heavy filler with the particle size of 1.0-2.0 mm and the bulk density of 2.3-2.5 g / cm < 3 >; the composite separation layer is arranged between the enhanced biological reaction area and the deep filtration area, and the wetland system further comprises a water inlet device, an aeration device and a backwashing device. Compared with the prior art, the problems that a traditional constructed wetland is single in function, low in pollutant removal efficiency, prone to blockage and poor in denitrification effect are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, in particular to a layered function enhanced constructed wetland system for sewage treatment. BACKGROUND

[0002] In the current black and odorous water treatment field, constructed wetlands are widely used in the end treatment of urban rivers, rural ditches and tail water of sewage plants due to their ecological friendliness and low operation cost, but traditional constructed wetlands still have significant technical bottlenecks in long-term practice. On the one hand, traditional constructed wetlands mostly rely on single ecological interception and natural microbial degradation, and have relatively single function, low removal efficiency of high-concentration COD, ammonia nitrogen and total phosphorus in black and odorous water, and especially for V-class and inferior V-class water bodies, it is difficult to achieve the goal of stable water quality reaching IV-class or above. At the same time, the internal traditional wetlands are prone to blockage due to plant root entanglement and suspended sediment accumulation, resulting in decreased hydraulic conductivity, poor long-term operation stability, frequent maintenance and high maintenance cost. On the other hand, the dissolved oxygen environment regulation and control ability of traditional constructed wetlands is weak, mostly relying on natural oxygen transfer of plant roots, easy to form local anoxic area, limited denitrification efficiency, and unable to effectively solve the problem of nitrogen exceeding standard in black and odorous water. In addition, the selection and layering design of traditional wetlands lack pertinence, mostly using single type of filler, difficult to realize the synergistic effect of "biodegradation - physical filtration - chemical adsorption", and the filler is prone to mixed layer phenomenon, further weakening the purification effect. At the same time, the existing constructed wetlands often only focus on water purification function, and fail to fully integrate ecological restoration and landscape effect, making it difficult to meet the integrated demand of "purification + ecological restoration" in the current black and odorous water treatment, limiting its application expansion in complex pollution scenarios. Therefore, a layered function enhanced constructed wetland system for sewage treatment is proposed. SUMMARY

[0003] The purpose of the present application is to provide a layered function enhanced constructed wetland system for sewage treatment, which solves the problems of single function, low pollutant removal efficiency, easy blockage and poor denitrification effect of traditional constructed wetlands.

[0004] The above technical purpose of the present application is realized by the following technical scheme: The application discloses a layered functional enhanced constructed wetland system for sewage treatment, which comprises an ecological surface layer area, an enhanced biological reaction area, a composite separation layer and a deep filtration area arranged in sequence from top to bottom; the ecological surface layer area is planted with emergent plants; the enhanced biological reaction area is filled with light suspended fillers with a particle size of 2-4 mm, and nitrifying bacteria and denitrifying bacteria agents are mixed in the light suspended fillers; the deep filtration area is filled with heavy fillers with a particle size of 1.0-2.0 mm and a bulk density of 2.3-2.5 g / cm3; the composite separation layer is arranged between the enhanced biological reaction area and the deep filtration area; and the wetland system further comprises a water inlet device, an aeration device and a backwashing device.

[0005] In a preferred embodiment, the ecological surface layer area further comprises a planting soil with a thickness of 0.1-0.2 m, the emergent plants are selected from reeds or calamus, and the root systems of the emergent plants extend downwards into the enhanced biological reaction area.

[0006] In a preferred embodiment, the light suspended fillers are polyethylene porous suspended balls, the specific surface area of the polyethylene porous suspended balls is 500-800 m² / m³; and the heavy fillers are modified ceramic granules.

[0007] In a preferred embodiment, the composite separation layer comprises nylon nets and water-permeable concrete boards arranged in sequence from top to bottom, the pore size of the nylon nets is 1.5 mm, the porosity of the water-permeable concrete boards is 20%-25%, and the edges of the nylon nets and the water-permeable concrete boards are connected and fixed to the wall of the wetland pool through corrosion-resistant fixing pieces.

[0008] In a preferred embodiment, a plurality of openings are arranged on the water-permeable concrete board, a protrusion is arranged on the opening, a liquid flow channel is arranged on the protrusion, the liquid flow channel is connected to the opening, and the protrusion supports the nylon net.

[0009] In a preferred embodiment, the water-permeable concrete board is arranged in an arc shape, the protrusion comprises a supporting column and an umbrella-shaped cap, the supporting column is arranged on the opening, the bottom of the umbrella-shaped cap is provided with a liquid inlet, and the liquid flow channel passes through the umbrella-shaped cap and the supporting column and is connected to the liquid inlet and the opening at two ends respectively.

[0010] In a preferred embodiment, the water inlet device is a horizontal water distribution pipe arranged at the top of the ecological surface layer area, the pipe wall of the water distribution pipe is provided with uniformly distributed water inlets, and the water inlet flow rate of the water inlet device is controlled to be 0.5-1.0 m³ / (m²·d).

[0011] In a preferred embodiment, the aeration device is arranged at the bottom of the enhanced biological reaction zone, the aeration device is a cross-shaped perforated aeration pipe, and the aeration intensity of the aeration device satisfies that the dissolved oxygen concentration in the enhanced biological reaction zone is maintained at 1.5-2.5 mg / L, and the hydraulic retention time of the wetland system is 4-6 h.

[0012] In a preferred embodiment, the backwashing device comprises a flooding pipe arranged in the ecological surface layer zone and a backwashing gas pipe arranged at the bottom of the deep filtration zone, the backwashing device is started when the water head loss of the deep filtration zone reaches 0.4-0.6 m, and the gas washing intensity of the backwashing gas pipe is 12-18 L / (m²·s).

[0013] In a preferred embodiment, the wetland system further comprises a water outlet device arranged at the bottom of the deep filtration zone, the water outlet device is a main pipe with a filter screen, and the water outlet end of the water outlet device is in communication with the water body receiving unit.

[0014] Compared with the prior art, the ecological surface layer area of the present application plants emergent plants, and the root system of the emergent plants can penetrate into the reinforced biological reaction area. On the one hand, the root system can block the larger suspended solids in the black and odorous water body through physical interception, thereby reducing the pollution load of the subsequent functional areas. On the other hand, the oxygen generated by the photosynthesis of the plants can be supplemented to the reinforced biological reaction area through the root system oxygen transfer, thereby providing part of the dissolved oxygen for the microbial activity. At the same time, the transpiration of the plants can regulate the water level inside the wetland system and maintain a stable hydraulic environment, so that the preliminary pollution interception and auxiliary oxygen supply can be achieved at the same time, the ecological restoration and landscape effect of the system are endowed, and the ecological value of the wetland is improved. The reinforced biological reaction area is filled with lightweight suspended filler with a particle size of 2-4 mm and mixed with nitrifying bacteria and denitrifying bacteria agents. The lightweight suspended filler has a large specific surface area and can be used as an attachment carrier for microorganisms, thereby providing sufficient growth space for the nitrifying bacteria and denitrifying bacteria. Moreover, the lightweight characteristic of the filler enables it to maintain a certain fluidity under the action of water flow, thereby avoiding local blockage caused by the entanglement of the plant roots and ensuring smooth water flow. The mixed nitrifying bacteria can convert the ammonia nitrogen in the water body into nitrate, and the denitrifying bacteria can convert the nitrate into nitrogen gas under suitable conditions, thereby realizing the denitrification reaction. At the same time, the microbial community can also degrade the organic matter in the water body, which can significantly improve the removal efficiency of COD and ammonia nitrogen in the black and odorous water body, solve the problem of insufficient biological degradation capacity of traditional wetlands, and ensure the hydraulic smoothness of the system during long-term operation. The deep filtration area is filled with heavy filler with a particle size of 1.0-2.0 mm and a bulk density of 2.3-2.5 g / cm³. The gaps between the particles of the heavy filler are uniform and have a certain mechanical strength, which can trap the micro-fine suspended solids in the water body through physical filtration, and at the same time, the active groups such as hydroxyl groups on the surface of the heavy filler (such as modified ceramic) can capture the phosphate ions in the water body through chemical adsorption, thereby achieving the effect of phosphorus removal. The large bulk density of the heavy filler can prevent the filler from being displaced under the action of water flow or backwashing, thereby maintaining the stability of the filter layer structure and further purifying the water quality, reducing the suspended solids and total phosphorus content of the effluent, and ensuring that the effluent water quality meets the standards, while ensuring the structural stability of the filtration area during long-term operation. The composite separation layer is arranged between the reinforced biological reaction area and the deep filtration area. The principle is to use the physical barrier effect of the separation layer to prevent the lightweight suspended filler in the upper layer from sinking into the deep filtration area due to water flow impact or backwashing disturbance, and at the same time, to prevent the heavy filler in the lower layer from floating up to the reinforced biological reaction area, thereby maintaining the functional independence of the two layers of filler. This can ensure that the fillers in each functional area do not mix, thereby ensuring the synergistic effect of biological degradation and deep filtration, and avoiding the problem of reduced purification efficiency caused by filler mixing. The setting principle of the water inlet device is to evenly distribute the black and odorous water body to the ecological surface layer area through a reasonable water distribution structure (such as a horizontal water distribution pipe), thereby avoiding uneven distribution of pollutants caused by local water flow concentration, ensuring that the water body and the fillers and microorganisms in each functional area are in full contact, improving the uniformity of pollutant removal of the system as a whole, and avoiding the problem of incomplete local treatment.The setting principle of the aeration device is to adjust the dissolved oxygen concentration in the region to a suitable range (1.5-2.5 mg / L) by introducing air into the bottom of the enhanced biological reaction zone, so as to form an aerobic-hypoxic microenvironment. The aerobic environment promotes the activity of nitrifying bacteria, and the hypoxic environment is beneficial to the action of denitrifying bacteria, so as to enhance the simultaneous nitrification and denitrification reaction, improve the denitrification efficiency, and make up for the problem of insufficient dissolved oxygen caused by the traditional wetland relying on oxygen transmission of plant roots only. The setting principle of the backwashing device is that when the water head loss of the deep filtration zone caused by the interception of suspended solids reaches the set value, the accumulated substances in the gap between the fillers are washed out by using the disturbance effect of water flow and air flow through the way of surface flooding and bottom air flushing, so as to solve the problem of easy clogging of the traditional wetland in long-term operation, restore the hydraulic conductivity and purification capacity of the filtration zone, prolong the operation cycle of the system, and reduce the maintenance cost. BRIEF DESCRIPTION OF DRAWINGS

[0015] Fig. 1 is a structural schematic diagram of a layered function enhanced artificial wetland system for sewage treatment.

[0016] Fig. 2 is a structural schematic diagram of a composite separation layer applied to the layered function enhanced artificial wetland system for sewage treatment (first perspective view).

[0017] Fig. 3 is a structural schematic diagram of a composite separation layer applied to the layered function enhanced artificial wetland system for sewage treatment (second perspective view).

[0018] Fig. 4 is a structural schematic diagram of a protrusion of a composite separation layer applied to the layered function enhanced artificial wetland system for sewage treatment.

[0019] Nylon net 1; pervious concrete plate 2; opening 3; protrusion 4; umbrella-shaped cap 5; liquid inlet 6; support column 7. DETAILED DESCRIPTION

[0020] The application will be further described in detail below with reference to the drawings.

[0021] The specific embodiments are only an explanation of the application, and are not a limitation of the application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, as long as the modifications are within the scope of the claims of the application.

[0022] As Figs. 1 to 4As shown, a layered function enhanced constructed wetland system for sewage treatment comprises, from top to bottom, an ecological surface layer area, an enhanced biological reaction area, a composite separation layer and a deep filtration area; the ecological surface layer area is planted with emergent plants, the enhanced biological reaction area is filled with lightweight suspended filler with a particle size of 2-4 mm, and the lightweight suspended filler is mixed with nitrifying bacteria and denitrifying bacteria agents, the deep filtration area is filled with heavy filler with a particle size of 1.0-2.0 mm and a bulk density of 2.3-2.5 g / cm³; the composite separation layer is arranged between the enhanced biological reaction area and the deep filtration area, and the wetland system further comprises a water inlet device, an aeration device and a backwashing device.

[0023] The ecological surface layer area of the layered function enhanced constructed wetland system for sewage treatment is planted with emergent plants, and the root system of the emergent plants can penetrate into the enhanced biological reaction area. On the one hand, the root system can block the larger particles of suspended solids in the black and odorous water body through physical interception, thereby reducing the pollution load of the subsequent functional area. On the other hand, the oxygen generated by the photosynthesis of plants can be supplemented to the enhanced biological reaction area through the root system oxygen transfer, thereby providing part of the dissolved oxygen for the microbial activity. At the same time, the plant transpiration can regulate the water level in the wetland system, thereby maintaining a stable hydraulic environment. The emergent plants can realize the preliminary pollution interception and auxiliary oxygen supply, and can also give the system ecological restoration and landscape effect, thereby improving the ecological value of the wetland. The enhanced biological reaction area is filled with lightweight suspended fillers with a particle size of 2-4 mm and mixed with nitrifying bacteria and denitrifying bacteria agents. The lightweight suspended fillers have a large specific surface area and can be used as an attachment carrier for microorganisms, thereby providing sufficient growth space for the nitrifying bacteria and denitrifying bacteria. The lightweight characteristic of the fillers can keep the fillers flowing under the action of water flow, thereby avoiding local blockage caused by the entanglement of the plant roots and ensuring the smooth flow of the water flow. The mixed nitrifying bacteria can convert the ammonia nitrogen in the water body into nitrate, and the denitrifying bacteria can convert the nitrate into nitrogen gas under suitable conditions, thereby realizing the denitrification reaction. At the same time, the microbial community can also degrade the organic matter in the water body, which can significantly improve the removal efficiency of COD and ammonia nitrogen in the black and odorous water body, solve the problem of insufficient biodegradation capacity of the traditional wetland, and ensure the hydraulic smoothness of the long-term operation of the system. The depth filtration area is filled with heavy fillers with a particle size of 1.0-2.0 mm and a bulk density of 2.3-2.5 g / cm³. The gaps between the particles of the heavy fillers are uniform and have a certain mechanical strength, which can intercept the micro-fine suspended solids in the water body through physical filtration, and at the same time, the active groups such as hydroxyl groups on the surface of the heavy fillers (such as modified ceramic) can capture the phosphate ions in the water body through chemical adsorption, thereby realizing the phosphorus removal effect. The large bulk density of the fillers can prevent the fillers from being displaced under the action of water flow or backwashing, thereby maintaining the stability of the filter layer structure, further purifying the water quality, reducing the suspended solids and total phosphorus content of the effluent, ensuring that the effluent water quality meets the standards, and ensuring the structural stability of the long-term operation of the filtration area. The composite separation layer is arranged between the enhanced biological reaction area and the depth filtration area. The principle is to use the physical blocking effect of the separation layer to prevent the lightweight suspended fillers in the upper layer from sinking to the depth filtration area due to water flow impact or backwashing disturbance, and to prevent the heavy fillers in the lower layer from floating to the enhanced biological reaction area, thereby maintaining the functional partition independence of the two layers of fillers. The composite separation layer can ensure that the fillers in each functional area do not mix, thereby ensuring the synergistic effect of the biological degradation and depth filtration functions, avoiding the problem of reduced purification efficiency caused by the mixing of the fillers. The setting principle of the water inlet device is to uniformly distribute the black and odorous water body to the ecological surface layer area through a reasonable water distribution structure (such as a horizontal water distribution pipe), thereby avoiding uneven distribution of pollutants caused by local water flow concentration, ensuring that the water body and the fillers and microorganisms in each functional area are in full contact, improving the uniformity of the pollutant removal of the system as a whole, and avoiding the problem of incomplete local treatment.The setting principle of the aeration device is to adjust the dissolved oxygen concentration in the region to a suitable range (1.5-2.5 mg / L) by introducing air into the bottom of the enhanced biological reaction zone, to form an aerobic-anoxic microenvironment. The aerobic environment promotes the activity of nitrifying bacteria, and the anoxic environment is conducive to the action of denitrifying bacteria, thereby enhancing the simultaneous nitrification and denitrification reaction, improving the denitrification efficiency, and making up for the problem of insufficient dissolved oxygen caused by the traditional wetland relying only on plant root oxygen transport. The setting principle of the backwashing device is that when the water head loss of the deep filtration zone reaches the set value due to the interception of suspended solids, the accumulated material in the gap between the fillers is washed out by using the disturbance effect of water flow and air flow through surface flooding and bottom air flushing, thereby solving the problem of easy clogging of the traditional wetland during long-term operation, restoring the hydraulic conductivity and purification capacity of the filtration zone, prolonging the system operation cycle, and reducing the maintenance cost.

[0024] Further, the ecological surface layer zone further comprises a planting soil with a thickness of 0.1-0.2 m, the emergent plant is selected from reed or alocasia, and the root system of the emergent plant extends into the interior of the enhanced biological reaction zone. The ecological surface layer zone is provided with a planting soil with a thickness of 0.1-0.2 m, on the one hand, because this thickness interval can provide sufficient root space and nutrient reserves for reed or alocasia, meet the physical support and nutrient supply required for the growth of the root system of the emergent plant, avoid the problem of unstable root fixation and insufficient nutrients affecting plant survival caused by too thin planting soil, or the problem of poor surface permeability and anaerobic water accumulation caused by too thick planting soil; on the other hand, the particle gap of the planting soil can preliminarily filter and intercept large particles of suspended solids (such as silt and plant residues) in the inflow water, reduce the pollutant load of the subsequent enhanced biological reaction zone, and the organic matter and microorganisms in the planting soil can assist in degrading part of the easily decomposed organic matter, thereby reducing the burden of the subsequent treatment link. The emergent plant is selected from reed or alocasia, because it has developed aeration tissue and pollution resistance, can grow normally in the low-oxygen environment of black and odorous water bodies, and can transmit oxygen in the air to the root system through the aeration tissue to provide an aerobic environment for the microorganisms around the root system; and the root system of reed or alocasia is strong and grows vigorously, can penetrate into the interior of the enhanced biological reaction zone, the root system not only can further intercept suspended solids in the water body, but also can provide additional attachment carriers for microorganisms such as nitrifying bacteria and denitrifying bacteria in the enhanced biological reaction zone, expand the living space of the microorganisms, improve the biological degradation efficiency, and the mechanical disturbance of the root system can promote the circulation of water flow and the exchange of substances in the enhanced biological reaction zone, avoid local pollution accumulation, in addition, the aboveground part of reed or alocasia can also form a landscape effect, and the ecological restoration and environmental beautification functions are taken into account, and the characteristic that the root system penetrates into the enhanced biological reaction zone also enables the plant oxygen transport to directly act on the biological reaction core area, supplement the dissolved oxygen, reduce the oxygen transmission loss, more efficiently support the metabolic activity of the microorganisms, and improve the removal effect of COD and ammonia nitrogen.

[0025] Further, the light-weight suspended filler is a polyethylene porous suspended ball, and the specific surface area of the polyethylene porous suspended ball is 500-800 m2 / m3; and the heavy filler is modified ceramsite. The light-weight suspended filler is selected as the polyethylene porous suspended ball, because the polyethylene material has the characteristics of sewage corrosion resistance and strong chemical stability, and can be used in the black and odorous water environment for a long time without being easily degraded and damaged, thereby avoiding secondary pollution caused by filler shedding; the porous structure and the large specific surface area of 500-800 m2 / m3 of the polyethylene porous suspended ball can provide a large number of attachment sites for nitrifying bacteria and denitrifying bacteria in the enhanced biological reaction zone, greatly increase the total amount of microorganisms and the contact area of the sewage, and make the microorganisms more fully decompose the pollutants such as COD and ammonia nitrogen in the water body, while the internal porous structure can form a local anoxic microenvironment to assist the denitrification reaction and improve the denitrification efficiency; and the polyethylene material has a small density, so that the suspended ball can maintain a suspended state under the action of water flow and aeration, thereby avoiding water flow blockage caused by filler accumulation, and can be slightly disturbed with the water flow to strengthen the mass transfer process of pollutants and microorganisms and further improve the biodegradation rate. The heavy filler is selected as the modified ceramsite, because the ceramsite itself has a rich pore structure and high mechanical strength, and after modification treatment (such as loading of hydroxyl groups and rare earth elements), the number of active sites on the surface of the ceramsite is significantly increased, so that the ceramsite can efficiently capture phosphate ions in the water body through chemical adsorption, thereby solving the problem of poor phosphorus removal effect of traditional fillers; at the same time, the particle size of 1.0-2.0 mm and the bulk density of 2.3-2.5 g / cm3 of the modified ceramsite enable the ceramsite to form a stable filtration layer in the depth filtration zone, so that the ceramsite neither displaces due to water flow impact, nor can the ceramsite intercept fine suspended solids in the water body through the gap between the particles to improve the water transparency; in addition, the pore structure of the ceramsite can also provide a small amount of attachment space for denitrifying bacteria in the depth filtration zone to assist the degradation of residual nitrate and further strengthen the denitrification effect, thereby realizing the synergistic purification of physical filtration and chemical adsorption and biological degradation.

[0026] Further, the composite separation layer comprises nylon mesh 1 and pervious concrete plate 2 arranged in sequence from top to bottom, the pore size of the nylon mesh 1 is 1.5 mm, the porosity of the pervious concrete plate 2 is 20%-25%, and the edges of the nylon mesh 1 and the pervious concrete plate 2 are connected and fixed with the wetland pool wall through corrosion-resistant fixing parts. The composite separation layer adopts nylon mesh 1 and pervious concrete plate 2 arranged in sequence from top to bottom, wherein the nylon mesh 1 selects 1.5 mm pore size, which is smaller than the 2-4 mm particle size of the lightweight suspended filler in the reinforced biological reaction zone, can accurately physically intercept the upper lightweight suspended filler, prevent it from sinking to the deep filtration zone under the impact of water flow or backwashing disturbance, and at the same time, the 1.5 mm pore size is larger than the diameter of the pollutant particles and water molecules in the sewage, which will not hinder the normal migration of water flow and pollutants; and the pervious concrete plate 2 is designed to have a porosity of 20%-25%, which not only ensures that the sewage can smoothly penetrate into the deep filtration zone, avoids the increase of water resistance and poor water flow caused by too low porosity, but also provides stable support for the upper nylon mesh 1 by the rigid structure of the concrete material, prevents the nylon mesh 1 from deforming or being damaged due to water flow pressure, and at the same time, the porosity of 20%-25% can also consider the structural strength of the concrete plate, avoid the decrease of mechanical properties and easy cracking of the plate body caused by too high porosity. In addition, the edges of the nylon mesh 1 and the pervious concrete plate 2 are connected and fixed with the wetland pool wall through corrosion-resistant fixing parts, which is considering that the wetland is in the sewage environment for a long time, the corrosion-resistant fixing parts can resist the corrosion of corrosive substances in the sewage, avoid the loosening of the edges of the separation layer caused by the corrosion failure of the fixing parts, and further prevent the mixing of the upper and lower fillers from the edge gap, finally realize the strict separation of the fillers in the upper and lower functional zones through the accurate interception of the nylon mesh 1, the support and water permeation of the pervious concrete plate 2, and the structural stability of the edge corrosion-resistant fixation, while ensuring the smooth flow of water and the structural stability of long-term operation of the system.

[0027] The corrosion-resistant fixing parts can be 304 / 316L stainless steel expansion bolts, FRP (glass fiber reinforced plastic) bolts, glass fiber reinforced PA66 buckles, or polytetrafluoroethylene coated carbon steel anchors.

[0028] In some embodiments, the water-permeable concrete plate 2 is provided with a plurality of openings 3, the openings 3 are provided with protrusions 4, the protrusions 4 are provided with liquid flow channels, the liquid flow channels are connected to the openings 3, and the protrusions 4 support the nylon net 1. The water-permeable concrete plate 2 is provided with a plurality of openings 3 and the openings 3 are provided with protrusions 4, the height of the protrusions 4 is 0.5-2 cm, the protrusions 4 support the nylon net 1, a gap is formed between the nylon net 1 and the water-permeable concrete plate 2 to separate them, and the problem of liquid flow blockage caused by the misalignment of the hole positions when the two are too tightly attached is avoided; the liquid flow channels on the protrusions 4 are connected to the openings 3, and when water leaks through the nylon net 1, it can smoothly flow into the openings 3 through the liquid flow channels, ensuring that the water flow will not be locally retained due to structural attachment problems when passing through the composite separation layer, which not only ensures the smoothness of the water force conduction, but also maintains the interception form of the nylon net 1 with the support of the protrusions 4, avoiding the blockage of the mesh holes or the interception failure caused by the deformation of the nylon net 1 under pressure.

[0029] Further, the water-permeable concrete plate 2 is arranged in an arch shape, the protrusions 4 include support columns 7 and umbrella-shaped caps 5, the support columns 7 are arranged on the openings 3, the bottom of the umbrella-shaped cap 5 is provided with a liquid inlet 6, the liquid flow channel passes through the umbrella-shaped cap 5 and the support column 7, and the two ends are connected to the liquid inlet 6 and the opening 3, respectively. The water-permeable concrete plate 2 is arranged in an arch shape, which utilizes the mechanical properties of the arch structure, the arc surface can disperse external loads (such as the pressure of the upper filler and the impact force of backwashing), and compared with the flat structure, it can resist deformation better, significantly improving the overall structural stability of the plate body and avoiding cracks caused by uneven stress during long-term use; at the same time, the curved surface shape of the arch makes the liquid flowing on the upper surface of the plate body tend to flow to both sides due to gravity, and the water flow formed during the flow process can automatically flush the surface of the support columns 7 distributed on the plate body, flushing away the suspended solids, microbial flocs and other substances attached to the periphery of the support columns 7, preventing these impurities from accumulating around the support columns 7, thereby ensuring the smoothness of the support columns 7 and the surrounding area and avoiding local blockage affecting water force conduction. The support columns 7 are arranged on the openings 3, the bottom of the umbrella-shaped cap 5 is provided with a liquid inlet 6, and the liquid flow channel penetrates the umbrella-shaped cap 5 and the support column 7, connecting the liquid inlet 6 and the opening 3, this structure makes the water first enter the liquid flow channel through the liquid inlet 6 at the bottom of the umbrella-shaped cap 5, and then flow downward through the opening 3 and pass through the concrete plate, the cap structure of the umbrella-shaped cap 5 can block larger particles of impurities from falling directly on the liquid inlet 6, reducing the probability of impurities entering the liquid flow channel.

[0030] Further, the water inlet device is a horizontal water distribution pipe arranged at the top of the ecological surface layer area, the pipe wall of the water distribution pipe is provided with uniformly distributed water inlet holes, and the water inlet flow of the water inlet device is controlled to be 0.5-1.0m³ / (m²・d). The water inlet device adopts a horizontal water distribution pipe arranged at the top of the ecological surface layer area, and the pipe wall of the water distribution pipe is provided with uniformly distributed water inlet holes. A multi-point water outlet structure is formed by the horizontally arranged pipe body and the uniformly distributed water inlet holes, so that the black and odorous water body can flow into from multiple points at the top of the ecological surface layer area simultaneously, avoiding the local flow concentration caused by a single water inlet point. At the same time, the water inlet flow is controlled to be 0.5-1.0m³ / (m²・d). This flow range matches the permeability of the planted soil in the ecological surface layer area and the growth tolerance of the emergent plants, and will not cause the loss of the planted soil due to excessive flow, damage to the plant root system due to water flow impact, or too long hydraulic retention time, anaerobic odor of the water body due to too small flow. Under this design, the uniformly distributed water inlet holes can form a uniform water flow on the top of the ecological surface layer area, ensuring that the water body is in full contact with the planted soil and the emergent plant root system, improving the preliminary suspended solids retention efficiency of the planted soil and the physical interception and auxiliary oxygen supply effect of the root system. Precise control of the water inlet flow can maintain a stable hydraulic environment in the wetland system, so that the microorganisms in the subsequent enhanced biological reaction zone can efficiently degrade pollutants under suitable water flow conditions, avoid changes in biological community activity caused by flow fluctuations, and at the same time ensure that the deep filtration area can continuously play a filtering role, ultimately realizing the stable operation of each functional area and improving the overall wastewater treatment effect.

[0031] Further, the aeration device is arranged at the bottom of the enhanced biological reaction zone, the aeration device is a cross-shaped perforated aeration pipe, and the aeration intensity of the aeration device satisfies that the dissolved oxygen concentration in the enhanced biological reaction zone is maintained at 1.5-2.5 mg / L, and the hydraulic retention time of the wetland system is 4-6 h. The aeration device arranged at the bottom of the enhanced biological reaction zone and the cross-shaped perforated aeration pipe are used to diffuse air from the lower part of the reaction zone to the upper part, and the cross-shaped pipe layout is combined to make the aeration air flow uniformly cover the entire enhanced biological reaction zone, avoiding insufficient aeration in local areas; the perforation design on the aeration pipe can divide the air into small bubbles, increase the contact area between air and water, improve the oxygen dissolution efficiency, and then make the aeration intensity accurately satisfy that the dissolved oxygen concentration in the enhanced biological reaction zone is maintained at 1.5-2.5 mg / L - the dissolved oxygen concentration interval can provide sufficient oxygen for nitrifying bacteria to promote the conversion of ammonia nitrogen to nitrate, and can form a local anoxic environment during the bubble rising interval to create suitable conditions for denitrifying bacteria to convert nitrate to nitrogen, realizing simultaneous nitrification and denitrification. The hydraulic retention time of the wetland system is controlled to be 4-6 h, which is based on the rate of microorganism degradation of pollutants in the enhanced biological reaction zone. This time length can ensure that the pollutants such as COD and ammonia nitrogen in the water have enough time to fully contact and be degraded by microorganisms and light suspended fillers, avoid incomplete treatment of pollutants due to too short retention time, and prevent too long retention time from causing water anaerobic and microbial activity to decline. At the same time, it is matched with the cross-shaped perforated aeration at the bottom to maintain the dissolved oxygen at an appropriate concentration for a sufficient time, ensuring that the nitrification and denitrification reactions are fully carried out, finally significantly improving the pollutant removal efficiency of the enhanced biological reaction zone and ensuring that the effluent water quality is stable and up to standard.

[0032] Further, the backwashing device includes a flooding pipe arranged in the ecological surface layer area and a backwashing air pipe arranged at the bottom of the deep filtration area. When the water head loss of the deep filtration area reaches 0.4-0.6 m, the backwashing device is started, and the air washing intensity of the backwashing air pipe is 12-18 L / (m2·s). The backwashing device includes a flooding pipe arranged in the ecological surface layer area and a backwashing air pipe arranged at the bottom of the deep filtration area. When the water head loss of the deep filtration area reaches 0.4-0.6 m due to the interception of suspended solids, the device is started, and the air washing intensity of the backwashing air pipe is controlled to be 12-18 L / (m2·s). In principle, when the water head loss of the deep filtration area reaches 0.4-0.6 m, the gap between the fillers is blocked by suspended solids to the key node that affects the normal hydraulic conductivity, and at this time, the start of backwashing can timely remove the blockage; the flooding pipe of the ecological surface layer area can inject water from top to bottom to flush the planting soil and emergent plant root system of the ecological surface layer area, avoid the further blockage of the deep filtration area by the surface impurities flowing down with the water flow, and form the water flow pressure from top to bottom; the backwashing air pipe at the bottom of the deep filtration area sprays air upward at an air washing intensity of 12-18 L / (m2·s), which can not only produce enough air flow disturbance to slightly fluidize the heavy filler in the deep filtration area and make the accumulated suspended solids in the filler gap separate from the filler surface, but also not cause displacement or structural damage of the heavy filler due to excessive air washing intensity. In terms of effect, the upper and lower coordinated backwashing mode forms a countercurrent flow with the upper flooding water flow and the lower backwashing air flow, which can efficiently flush out the blockage of the deep filtration area and restore the porosity and hydraulic conductivity of the filler, avoiding the problem of incomplete cleaning of the traditional single backwashing mode; the precise control of the water head loss starting threshold can avoid the waste of water resources and energy caused by early backwashing, or the decrease of system operation efficiency caused by late backwashing; and the air washing intensity of 12-18 L / (m2·s) ensures the balance between the backwashing effect and the stability of the filler.

[0033] Further, the wetland system further comprises a water outlet device arranged at the bottom of the deep filtration zone, the water outlet device is a total pipe with a filter screen, and a water outlet end of the water outlet device is communicated with the water body storage unit. The wetland system is provided with the water outlet device at the bottom of the deep filtration zone, and the water outlet device is a total pipe with a filter screen. The water treated by the deep filtration zone needs to be discharged through the water outlet device. The total pipe structure can realize the centralized collection of the filtered water, avoid the water flow disorder caused by the dispersed water outlet, and the filter screen can block the small heavy filler particles possibly falling off with the water flow in the deep filtration zone or the micro-fine suspended solids not completely intercepted, to prevent these impurities from entering the subsequent link with the water outlet. Meanwhile, the water outlet end of the water outlet device is communicated with the water body storage unit. With the help of the gravity of the water body or the slight hydraulic pressure difference, the standard water filtered through the filter screen can stably flow into the storage unit, forming a complete water treatment process. The design of the total pipe with a filter screen not only guarantees the uniformity and collection efficiency of the water outlet, but also further improves the water quality of the water outlet through the secondary filtration effect of the filter screen, to avoid the influence of impurity leakage on the water quality in the storage unit. The communication between the water outlet end and the storage unit realizes the timely storage of the treated water, prevents the increase of the water resistance or the formation of the anaerobic environment caused by the water accumulation at the bottom of the deep filtration zone, and ensures the controllable water flow direction of the wetland system, facilitating the reuse or standard discharge of the treated water.

[0034] It should be noted that, in the present document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional elements of the process, method, article, or apparatus that comprises the element. Additionally, the terms "first", "second", "third", etc. are used herein only to distinguish one element from another, and do not imply a required or actual temporal or chronological order. The terms "top", "bottom", "front", "back", "side", "under", "over", "above", "below", and the like, are used only to denote relative positions according to the drawings, and do not indicate actual relative positions of the elements.

[0035] The above description of the embodiments is for the purpose of enabling one of ordinary skill in the art to make and use the application, and the modifications and improvements obvious to those skilled in the art are to be included within the scope of the present application. Therefore, the present application is not limited to the embodiments described above, and the modifications and improvements made by those skilled in the art based on the disclosure of the present application without departing from the scope of the present application should be included within the scope of the present application.

Claims

1. A layered functional enhanced constructed wetland system for wastewater treatment, characterized in that, The ecological surface layer area, the reinforced biological reaction area, the composite separation layer and the deep filtration area are sequentially arranged from top to bottom; the ecological surface layer area is planted with emergent plants, the reinforced biological reaction area is filled with light suspended filler with a particle size of 2-4 mm, and the light suspended filler is mixed with nitrifying bacteria and denitrifying bacteria agents, the deep filtration area is filled with heavy filler with a particle size of 1.0-2.0 mm and a bulk density of 2.3-2.5 g / cm³, the composite separation layer is arranged between the reinforced biological reaction area and the deep filtration area, and the wetland system further comprises a water inlet device, an aeration device and a backwashing device.

2. The layered function enhanced constructed wetland system for wastewater treatment according to claim 1, wherein, The ecological surface layer area further comprises a planting soil with a thickness of 0.1-0.2 m, the emergent plants are selected from reeds or calamus, and the root system of the emergent plants extends into the reinforced biological reaction area.

3. The layered functionally enhanced constructed wetland system for wastewater treatment according to claim 1, wherein, The light suspended filler is a polyethylene porous suspended ball, the specific surface area of the polyethylene porous suspended ball is 500-800 m² / m³, and the heavy filler is modified ceramsite.

4. The layered functionally enhanced constructed wetland system for wastewater treatment according to claim 1, wherein, The composite separation layer comprises a nylon net and a water permeable concrete slab which are sequentially arranged from top to bottom, the pore size of the nylon net is 1.5 mm, the porosity of the water permeable concrete slab is 20%-25%, and the edges of the nylon net and the water permeable concrete slab are connected and fixed to the wall of the wetland pool by corrosion-resistant fixing pieces.

5. The layered functionally enhanced constructed wetland system for wastewater treatment according to claim 4, wherein, A plurality of openings are arranged on the water permeable concrete slab, a protrusion is arranged on the opening, a liquid flow channel is arranged on the protrusion, the liquid flow channel is connected to the opening, and the protrusion supports the nylon net.

6. The layered functionally enhanced constructed wetland system for wastewater treatment according to claim 5, wherein, The water permeable concrete slab is arranged in an arc shape, the protrusion comprises a support column and an umbrella-shaped cap, the support column is arranged on the opening, the bottom of the umbrella-shaped cap is provided with a liquid inlet, and the liquid flow channel passes through the umbrella-shaped cap and the support column, and the two ends are connected to the liquid inlet and the opening, respectively.

7. The layered functionally enhanced constructed wetland system for wastewater treatment according to claim 1, wherein, The water inlet device is a horizontal water distribution pipe arranged at the top of the ecological surface layer area, the pipe wall of the water distribution pipe is provided with uniformly distributed water inlet holes, and the water inlet flow rate of the water inlet device is controlled to be 0.5-1.0 m³ / (m²·d).

8. The layered functionally enhanced constructed wetland system for wastewater treatment according to claim 1, wherein, The aeration device is arranged at the bottom of the reinforced biological reaction area, the aeration device is a cross-shaped perforated aeration pipe, the aeration intensity of the aeration device satisfies that the dissolved oxygen concentration in the reinforced biological reaction area is maintained at 1.5-2.5 mg / L, and the hydraulic retention time of the wetland system is 4-6 h.

9. The layered functionally- enhanced constructed wetland system for wastewater treatment according to claim 1, wherein, The backwashing device comprises a flooding pipe arranged in the ecological surface layer area and a backwashing gas pipe arranged at the bottom of the deep filtration area, the backwashing device is started when the water head loss of the deep filtration area reaches 0.4-0.6 m, and the gas washing intensity of the backwashing gas pipe is 12-18 L / (m²·s).

10. The layered functionally enhanced constructed wetland system for wastewater treatment as claimed in claim 1 wherein, The wetland system further comprises a water outlet device arranged at the bottom of the deep filtration area, the water outlet device is a main pipe with a filter screen, and the water outlet end of the water outlet device is communicated with a water body receiving unit.

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