Siphon artificial wetland system and method for synchronously removing antibiotics and nitrogen

Abstract

The invention belongs to the technical field of constructed wetlands, and discloses a siphon constructed wetland system and a method for synchronously removing antibiotics and nitrogen, a bed body of the siphon constructed wetland system is sequentially provided with a supporting bottom layer, an iron-sulfur layer and a surface layer from bottom to top, and a flow guide partition plate is vertically arranged in the middle of the bed body and divides the bed body into a water inlet side area and a water outlet side area; the flow guide partition plate penetrates through the bottom layer and the iron-sulfur layer and is located on the supporting bottom layer, and the flow guide partition plate is made of biochar; the water inlet pipe is connected with the top of the water inlet side area, the water outlet pipe is a siphon pipe, the siphon pipe is of an inverted U-shaped pipe structure, the communicating position of an inlet of the siphon pipe and the water outlet side area is located at the set height of the constructed wetland, and the height is 1 / 5-1 / 2 of the total height of the constructed wetland. The height of the bottom end of the water outlet pipe of the siphon wetland is increased, so that the problem that the actual retention time of sewage near the water inlet of the siphon wetland does not accord with the preset time is solved.

Description

Technical Field

[0001] This invention belongs to the field of constructed wetland technology and relates to a siphon constructed wetland system and a method for simultaneously removing antibiotics and nitrogen. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] In recent years, antibiotics have been widely used in the medical and aquaculture fields, resulting in a large amount of residual antibiotics entering the aquatic environment through urban wastewater treatment plants. Wastewater treatment plants have low antibiotic removal efficiency, and nitrogen pollution is often present in the effluent, leading to eutrophication and ecological risks. Therefore, there is an urgent need to develop technologies that can simultaneously remove nitrogen and antibiotics.

[0004] Constructed wetlands, as a low-cost and environmentally friendly treatment method, are used to treat wastewater treatment plant effluent. However, traditional constructed wetlands have the following problems: insufficient dissolved oxygen inhibits nitrification, and low extracellular electron transfer efficiency leads to poor antibiotic degradation.

[0005] Siphonic constructed wetlands create alternating anoxic / aerobic environments through periodic flooding and drainage, improving pollutant removal efficiency and avoiding the high energy consumption associated with aeration. However, the following issues still exist: Uneven water flow distribution can easily cause "short circuits", leading to overload and blockage in some substrate areas, while other areas have low utilization rates. To address the issues of uneven water flow and inefficient substrate utilization in siphonic constructed wetlands, PVC or concrete partitions are used to guide the water flow and prevent the formation of short-circuit paths. This ensures uniform water distribution, effectively preventing premature saturation of the influent substrate and inefficient utilization of the effluent substrate, thereby steadily improving effluent water quality. However, the smooth surface of PVC or concrete partitions is not conducive to microbial adhesion and may release harmful substances or alter the pH value near the partition, inhibiting the activity of denitrifying and antibiotic-degrading microorganisms. The outlet of existing siphon constructed wetlands is located at the bottom, which shortens the actual residence time of sewage near the inlet, resulting in insufficient degradation of antibiotics and unstable effluent quality.

[0006] To address the issue of insufficient electron donors in constructed wetlands, sulfur can be used as a filler to construct sulfur-based constructed wetlands. This system utilizes a sulfur-mediated autotrophic denitrification process, employing sulfur as an electron donor to reduce nitrates to nitrogen gas under anoxic / anaerobic conditions, significantly improving nitrogen removal efficiency.

[0007] However, sulfur-based wetlands are ineffective at antibiotic removal, primarily due to the low electron transfer efficiency of the sulfur cycle, which fails to meet the electron demands of antibiotic-degrading bacteria, resulting in slow antibiotic degradation. To improve electron transfer efficiency, iron ore can be introduced as an electron carrier to enhance extracellular electron transport and promote antibiotic degradation. However, current systems commonly suffer from insufficient iron ore addition and excessively high sulfur content (often exceeding 60%). Excess sulfur is converted into hydrogen sulfide (H2S) by sulfate-reducing bacteria under anaerobic conditions. H2S is not only highly toxic, inhibiting the activity of key functional microorganisms and disrupting community structure, but it also reduces denitrification and antibiotic removal efficiency, leading to a decline in system performance. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the purpose of this invention is to provide a siphon-based constructed wetland system and a method for simultaneously removing antibiotics and nitrogen.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a siphon-type constructed wetland system, wherein the bed body is provided with a supporting bottom layer, an iron-sulfur layer and a surface layer in sequence from bottom to top, and a flow guide baffle is vertically arranged in the middle of the bed body to divide the bed body into an inlet side area and an outlet side area. The flow guide baffle penetrates the bottom layer and the iron-sulfur layer and is located above the supporting bottom layer. The material of the flow guide baffle is biochar. The inlet pipe is connected to the top of the inlet side area, and the outlet pipe is a siphon pipe with an inverted U-shaped structure. The connection point between the inlet of the siphon pipe and the outlet side area is located at a set height of the constructed wetland, which is 1 / 5 to 1 / 2 of the total height of the constructed wetland.

[0010] Secondly, the present invention provides a method for simultaneously removing antibiotics and nitrogen using the aforementioned siphon-constructed wetland system, comprising the following steps: including an immersion stage and a reoxygenation stage, wherein, During the immersion stage, the wastewater is transported to the inlet area. Under the guidance of the baffle, the wastewater flows from top to bottom through the surface layer, the iron-sulfur layer and the support bottom layer, and then flows into the outlet area from the support bottom layer. It flows evenly from bottom to top through the support bottom layer, the iron-sulfur layer and the surface layer. During this stage, the wastewater is degraded. During the reoxygenation stage, when the wastewater rises to the siphon level, the siphon effect is triggered. The degraded wastewater flows out of the siphon pipe while simultaneously absorbing oxygen in the bed. When the wastewater level drops below the height of the siphon pipe inlet, the outflow stops. The process alternates between the submersion phase and the reoxygenation phase to achieve wastewater treatment.

[0011] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: This invention combines siphon-enclosed wetlands with an iron-sulfur matrix, eliminating the high cost limitations of energy-consuming equipment and external carbon sources, and achieving synergistic deep removal of nitrogen and antibiotics in a zero-energy manner.

[0012] This invention controls the iron-sulfur matrix mass ratio to approximately 1:1, effectively controlling the generation and release of hydrogen sulfide and reducing its toxic effects on microorganisms, water, and air.

[0013] A biochar baffle is installed in the middle of the wetland bed to effectively guide the uniform infiltration and flow of wastewater, ensuring balanced contact and reaction between wastewater and the wetland substrate and microorganisms. This solves the problems of uneven water flow distribution, premature saturation of the influent substrate, and inefficient utilization of the effluent substrate. Furthermore, the larger microbial attachment area of ​​the biochar baffle facilitates cooperation and communication between denitrification and antibiotic-degrading microorganisms, significantly increasing microbial species abundance. This addresses the issues of traditional materials increasing water toxicity and inhibiting functional microorganisms, thereby achieving the synergistic removal of nitrogen and antibiotics.

[0014] By raising the bottom of the siphon wetland's outlet pipe to 20cm, the problem of the actual wastewater retention time near the siphon wetland's inlet not matching the preset time was solved. This allows for a balanced and stable effluent quality from the siphon wetland without the need for subsequent treatment operations.

[0015] In an aerobic environment, S 0 It will be oxidized to sulfate (SO4) 2- Iron (Fe) in iron ore 2+ Iron ore can act as an electron donor, promoting electron transfer processes in sulfate-reducing and sulfur-oxidizing bacteria. Iron ore contributes to enhancing the reaction rate in sulfur oxidation by providing electrons and promoting the reaction. In anaerobic environments, iron ions in wetland systems help sulfate-reducing bacteria complete the sulfate reduction process. The reduction of sulfate by sulfate-reducing bacteria to H₂S can react with Fe... 2+ FeS is formed. At a mass ratio of iron to sulfur of 1:1, H₂S can react with iron (Fe²⁺). 2+ The reaction fully produces FeS, which helps reduce the accumulation of H2S. This promotes the sulfur redox cycle, increases electron transfer efficiency, and thus facilitates antibiotic removal.

[0016] The iron-sulfur redox cycle created in wetlands can effectively increase the diversity of microorganisms, especially denitrifying and antibiotic-degrading microorganisms. Furthermore, the iron-sulfur matrix, acting as an electron shuttle, can promote communication and cooperation among microorganisms, thereby achieving highly efficient synergistic removal of nitrogen and antibiotics. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is a schematic diagram of the structure of the siphon-constructed wetland system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the internal structure of the siphon-constructed wetland system according to an embodiment of the present invention.

[0019] Among them, 1-inlet pipe; 2-bed body; 3-outlet pipe; 4-guide baffle; 5-perforated pipe; 6-inlet side area; 7-outlet side area; 8-support bottom layer; 9-iron-sulfur layer; 10-surface layer; 11-yellow iris; 12-siphon water level. Detailed Implementation

[0020] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] Constructed wetlands are a low-energy and environmentally friendly wastewater treatment system widely used for treating effluent from wastewater treatment plants. However, traditional constructed wetlands suffer from several drawbacks. First, their submerged structure leads to insufficient dissolved oxygen, limiting nitrification. Second, the lack of electron donors hinders denitrification, thus limiting its effectiveness. Finally, the low extracellular electron transfer efficiency of wetland systems makes it difficult to meet the requirements for deep antibiotic degradation, resulting in poor antibiotic treatment outcomes.

[0022] To address the problem of insufficient dissolved oxygen, various wetland oxygenation technologies exist, such as aeration and siphon technologies. Aeration technology utilizes aeration pumps to increase the oxygen content in the wetland. These pumps can rapidly increase the oxygen content in constructed wetlands, thereby achieving efficient removal of pollutants such as organic matter and ammonia nitrogen. However, aeration technology requires power equipment such as aeration pumps, leading to drawbacks such as complex operation, high energy consumption, and high costs.

[0023] Siphon technology uses a siphon to periodically submerge and drain wetlands without requiring power, effectively overcoming the drawbacks of complex operation and high energy consumption. The wetland outlet is connected to a siphon pipe, and wastewater continuously flows in from the inlet, slowly submerging the wetland and creating an oxygen-deficient environment. When the wastewater level exceeds the top of the siphon pipe, siphoning occurs, and oxygen is introduced into the wetland under pressure during drainage, enhancing the oxygen supply. Siphon technology creates alternating oxygen-deficient and aerobic environments in the wetland, promoting oxidation-reduction reactions of pollutants and achieving highly efficient pollutant removal.

[0024] However, traditional siphonic constructed wetlands suffer from defects in water flow distribution, creating systemic treatment bottlenecks: the siphon-driven water flow tends to form "short-circuit" paths along wetland edges or areas with large matrix pores, resulting in wastewater not flowing sufficiently through the entire matrix layer and significantly shortening the contact time with microorganisms and plant roots; this uneven water flow causes the influent-side matrix to bear a high load of wastewater for a long time, leading to premature saturation of the influent-side matrix, rapid adsorption of pollutants (such as nitrogen and antibiotics) causing pore blockage, while the effluent-side matrix remains in an inefficient state due to insufficient contact with wastewater, resulting in wasted matrix resources and idle treatment capacity; ultimately, due to the uncontrollable water flow path, the pollutant removal effect varies drastically with fluctuations in influent water quality, making it difficult for effluent water quality to consistently meet standards, especially when facing the impact of recalcitrant pollutants (such as antibiotics), the system's shock resistance decreases significantly, and the overall treatment efficiency and reliability are greatly reduced.

[0025] To address the issues of uneven water flow and inefficient substrate utilization in siphonic wetlands, a combined technology involving the addition of baffles has emerged in recent years. By installing baffles within the wetland to guide water flow and prevent the formation of "short-circuit" paths, the water flow is ensured to be evenly distributed. This effectively prevents premature saturation of the influent substrate and inefficient utilization of the effluent substrate, thereby steadily improving effluent water quality. However, currently, the baffles used in siphonic wetlands are mostly made of polyvinyl chloride (PVC) and concrete, which negatively impact the denitrification and antibiotic removal efficiency of the wetland system. Specifically, the smooth surfaces of PVC and concrete lack sufficient adhesion space, resulting in insufficient adhesion capacity for microbial communities, thus reducing the removal efficiency of nitrogen and antibiotics. Furthermore, PVC itself may release harmful substances such as chlorides and plasticizers, which inhibit the activity of microbial communities and increase the toxicity of the effluent, further affecting water quality safety. On the other hand, the alkaline pH of concrete also inhibits the activity of denitrifying microorganisms and antibiotic-degrading bacteria, further reducing their removal efficiency. Therefore, the existing use of PVC and concrete materials in siphon wetland systems limits the efficient simultaneous removal of nitrogen and antibiotics.

[0026] Furthermore, the outlet of traditional siphon wetlands is installed at the bottom of the wetland. This results in all the wastewater in the wetland being discharged during rapid siphon drainage, while the actual residence time of wastewater near the inlet is shortened, reducing the effectiveness of antibiotic treatment and leading to unstable effluent quality that fails to meet consistent standards. In summary, traditional siphon wetlands suffer from drawbacks such as uneven water flow distribution, premature saturation of the substrate on the inlet side, inefficient use of the substrate on the outlet side, inhibition of nitrogen and antibiotic removal by the baffle material, and unstable effluent quality. Therefore, there is an urgent need for technological improvements to siphon constructed wetlands.

[0027] To address the problem of insufficient electron donors, constructed wetland systems using inorganic electron donors (such as sulfur) as fillers can effectively solve this issue. Constructed wetlands using sulfur as filler create a sulfur-mediated autotrophic denitrification system. Using elemental sulfur, sulfides, and thiosulfates as electron donors, and under anoxic or anaerobic conditions, nitrates act as electron acceptors, converting reduced sulfur into sulfates while simultaneously reducing nitrates to nitrogen gas. This achieves highly efficient removal of nitrate nitrogen and improves denitrification capacity.

[0028] However, sulfur-based constructed wetlands suffer from poor antibiotic removal efficiency. This is mainly because antibiotic removal depends not only on the availability of electron donors but also on the efficiency of electron transfer. Although sulfur-based wetlands can achieve autotrophic denitrification through electron transfer, the electron transfer efficiency of the sulfur redox cycle is very low, making it difficult to meet the electron utilization efficiency of antibiotic-degrading bacteria, resulting in slow antibiotic degradation and poor effectiveness. Therefore, sulfur-based constructed wetlands suffer from poor electron transfer efficiency, making it difficult to achieve synergistic and deep removal of nitrogen and antibiotics.

[0029] To address the low electron transport efficiency of sulfur-based constructed wetlands, introducing iron ore into the system has become a feasible optimization measure. The addition of iron ore can activate the sulfur redox cycle, which acts as an electron carrier to construct an extracellular electron transport network, thereby significantly improving the electron transport efficiency of microorganisms and promoting the efficient degradation of antibiotics. However, currently, the proportion of iron ore added (by mass or volume) in sulfur-based wetlands is far lower than that of sulfur, resulting in generally high sulfur content in the system.

[0030] Studies have shown that when the sulfur content exceeds 60%, sulfate-reducing bacteria in the anaerobic stage of siphon wetlands reduce the sulfate or elemental sulfur produced in the aerobic stage to hydrogen sulfide (H2S), resulting in the release of large amounts of H2S gas. Hydrogen sulfide is a highly toxic gas that can cause serious harm to microorganisms and higher organisms (including humans) even at low concentrations. It also significantly inhibits key microorganisms involved in denitrification and antibiotic degradation, disrupting the microbial community structure within the wetland system and thus reducing pollutant removal efficiency.

[0031] Therefore, sulfur-based constructed wetlands not only suffer from low electron transfer efficiency, but also easily lead to a series of negative effects such as H2S accumulation, microbial imbalance, and decreased nitrogen and antibiotic removal performance under conditions of insufficient iron ore addition and excessive sulfur ratio. It is urgent to use scientific methods to precisely control the sulfur filling ratio in order to achieve safe and efficient operation of the wetland system.

[0032] In a first aspect, the present invention provides a siphon-type constructed wetland system, wherein the bed body is provided with a supporting bottom layer, an iron-sulfur layer and a surface layer in sequence from bottom to top, and a flow guide baffle is vertically arranged in the middle of the bed body to divide the bed body into an inlet side area and an outlet side area. The flow guide baffle penetrates the bottom layer and the iron-sulfur layer and is located above the supporting bottom layer. The material of the flow guide baffle is biochar. The inlet pipe is connected to the top of the inlet side area, and the outlet pipe is a siphon pipe with an inverted U-shaped structure. The connection point between the inlet of the siphon pipe and the outlet side area is located at a set height of the constructed wetland, which is 1 / 5 to 1 / 2 of the total height of the constructed wetland.

[0033] The flow guide baffles are made of biochar, allowing wastewater to flow evenly through the substrate layers in the influent side area under the action of the baffles, and then flow evenly from the bottom up through the substrate layers in the effluent side area. Detailed analysis follows: Biochar possesses a rich porous structure (micropores and mesopores) and a rough surface. Compared to traditional smooth PVC or concrete partitions, the rough surface and porous structure can disrupt the preferential flow tendency of water, preventing wastewater from quickly forming a "short-circuit" path along the partition surface and forcing water to penetrate into the matrix. Biochar also has a high specific surface area (typically >500 m²). 2 / g) can adsorb some wastewater, and by slowly releasing it, it prolongs the residence time of the water flow in the matrix layer, promoting full contact between the wastewater and each matrix layer; The porous structure of biochar provides stable attachment sites for microorganisms (such as denitrifying bacteria and antibiotic-degrading bacteria) to form biofilms. The colonization of microorganisms on the surface of biochar and in the surrounding matrix can reduce water flow concentration caused by excessively large local pores in the matrix layer and homogenize the water flow path through the bioblocking effect. Extracellular polymers (EPS) produced by microbial metabolism can bind matrix particles, adjust pore distribution, and further regulate water flow distribution. Unlike concrete, which may release alkaline substances, and PVC, which releases plasticizers, biochar is chemically inert and will not change the pH value of the surrounding matrix or introduce toxic components. This avoids the decline in microbial activity and abnormal water flow paths caused by fluctuations in the chemical environment. Biochar baffles are also heat-resistant and corrosion-resistant, and are not easily deformed or degraded with long-term use, ensuring the durability of the flow guiding effect.

[0034] The connection point between the inlet and outlet areas of the siphon pipe is located at a set height within the constructed wetland to effectively prevent sewage near the inlet pipe from being discharged due to the siphon effect before reaching the expected retention time, thus ensuring the sewage treatment effect.

[0035] In some embodiments, the top of the siphon tube with the inverted U-shaped tube structure is flush with the inlet pipe.

[0036] The inlet pipe connects to the top of the inlet area. Wastewater must flow from top to bottom through the surface layer, the iron-sulfur layer, and the supporting bottom layer, and then flow from bottom to top from the outlet side. The top of the siphon pipe is flush with the inlet pipe, meaning that the siphon effect is only triggered when the wastewater level rises to the height of the inlet pipe. At this point, the wastewater has fully permeated all the matrix layers (including the iron-sulfur layer) on both the inlet and outlet sides, ensuring the preset hydraulic retention time and avoiding the problem of "wastewater on the top of the inlet side being discharged before flowing through the bottom layer" caused by bottom drainage in traditional siphon pipes.

[0037] In some embodiments, the flow guide baffle is located in the middle of the bed body, dividing the bed body evenly.

[0038] In some embodiments, the connection point between the inlet and outlet areas of the siphon pipe is located at 1 / 4 to 1 / 2, preferably 1 / 3, of the total height of the constructed wetland.

[0039] In some embodiments, the mass ratio of iron matrix to sulfur matrix in the iron-sulfur layer is 0.9-1.1:1, preferably 1:1. At this ratio, the iron ore can fully react with the hydrogen sulfide generated during sulfate reduction, reducing the release of toxic gases and facilitating the removal of nitrogen and antibiotics.

[0040] Preferably, the particle size of the filling matrix in the iron-sulfur layer is 4-8 mm.

[0041] In some embodiments, the support substrate and the surface layer are both gravel, quartz sand, zeolite and / or crushed stone.

[0042] Preferably, the matrix particle size of the supporting bottom layer is 1-2 cm, and the matrix particle size of the surface layer is 4-8 mm.

[0043] Preferably, the thickness ratio of the support base layer, the iron-sulfur layer and the surface layer is 1-5:35-55:1-5.

[0044] In some embodiments, wetland plants are grown on the surface of the bed.

[0045] In some embodiments, a perforated tube is also included, inserted into the bed from top to bottom and extending above the bed. The perforated tube is used for in-situ monitoring of the physicochemical properties of wastewater (such as dissolved oxygen and pH).

[0046] In some embodiments, the outlet end of the inlet pipe is wrapped with a mesh screen. This is used for preliminary filtration of wastewater to prevent clogging of the constructed wetland.

[0047] Secondly, the present invention provides a method for simultaneously removing antibiotics and nitrogen using the aforementioned siphon-constructed wetland system, comprising the following steps: including an immersion stage and a reoxygenation stage, wherein, During the immersion stage, the wastewater is transported to the inlet area. Under the guidance of the biochar material baffle, the wastewater flows from top to bottom through the surface layer, the iron-sulfur layer and the support bottom layer, and then flows into the outlet area from the support bottom layer. It flows evenly from bottom to top through the support bottom layer, the iron-sulfur layer and the surface layer. During this stage, the wastewater is degraded. During the reoxygenation stage, when the wastewater rises to the siphon level, the siphon effect is triggered. The degraded wastewater flows out of the siphon pipe while simultaneously absorbing oxygen in the bed. When the wastewater level drops below the height of the siphon pipe inlet, the outflow stops. The process alternates between the submersion phase and the reoxygenation phase to achieve wastewater treatment.

[0048] In some embodiments, the method for preparing the flow guide baffle is as follows: after drying, pulverizing, and pyrolyzing biomass, biochar powder is obtained; After grinding and sieving the biochar powder, it is mixed with starch adhesive, water is added to adjust it to a plastic state, and then it is pressed into a plate, dried and cured to obtain the final product.

[0049] The present invention will be further described below with reference to the embodiments.

[0050] Example like Figure 1 As shown, the siphonic constructed wetland is 65cm high, 15cm in diameter, and 60cm deep. The wetland mainly consists of three parts: an inlet pipe (1), a bed (2), and an outlet pipe (3). Both ends of the inlet pipe are wrapped with mesh to trap large particles of pollutants in the wastewater and prevent clogging. A biochar baffle (4) with a height of 55cm, a width of 15cm, and a thickness of 0.5cm, and a perforated pipe (5) with a height of 65cm and a diameter of 4cm are installed in the middle of the wetland bed.

[0051] The preparation method of the biochar-material flow guide plate 4 is as follows: wetland plants such as reeds and yellow irises are washed, dried (60℃), and pulverized. They are then placed in a tube furnace purged with nitrogen and pyrolyzed at 600℃ for 2 hours to obtain biochar powder. This powder is then ground and sieved through a 100-mesh screen to improve its uniformity. The sieved biochar powder is then uniformly mixed with 20% starch biomass binder, and deionized water is added to adjust it to a plastic state. The mixture is then placed in a mold and gravity-pressed into a plate shape, followed by drying and curing at 70℃ to finally obtain the biochar-material flow guide plate 4.

[0052] The biochar baffle 4 is used to guide the sewage to permeate evenly through each matrix layer and then discharge it. It also has high adsorption capacity and can enrich antibiotics, thereby prolonging the contact time between antibiotics and degrading microorganisms.

[0053] The flow guide baffle 4 divides the wetland into an inlet side area 6 and an outlet side area 7. Wastewater is discharged into the constructed wetland system from the inlet pipe 1. First, under the action of the flow guide baffle 4, it flows evenly through each substrate layer of the inlet side area 6, and then flows evenly from the bottom up through each substrate layer of the outlet side area 7.

[0054] The perforated tube 5 is used for in-situ monitoring of the physicochemical properties of wastewater (dissolved oxygen and pH, etc.).

[0055] The outlet pipe 3 is an inverted U-shaped siphon pipe with a height of 40cm and a diameter of 2cm. Its top height is flush with the inlet pipe, and its bottom height is 20cm. This effectively prevents sewage near the inlet pipe from being discharged due to the siphon effect before reaching the expected retention time, ensuring that all sewage in the wetland has a consistent retention time.

[0056] The wetland fill material consists of a support layer 8 (5cm high), an iron-sulfur layer 9 (55cm high), and a surface layer 10 (5cm high) from bottom to top. The support layer and surface layer can be made of matrices such as gravel, quartz sand, zeolite, and crushed stone. The particle size of the support layer matrix is ​​1-2cm, and the particle size of the surface layer matrix is ​​4-8mm.

[0057] The iron-sulfur layer 9 is filled with 50% iron matrix (pyrite or siderite) and 50% sulfur matrix (sulfur), both with a particle size of 4-8 mm. At this ratio, the iron ore can fully react with the hydrogen sulfide generated during sulfate reduction, reducing the release of toxic gases and facilitating the removal of nitrogen and antibiotics.

[0058] Yellow iris 11 can be planted in artificial wetlands at a density of 159 plants per square meter and a planting depth of 10 cm. Other wetland plants can also be selected.

[0059] The operation mode of this artificial wetland is as follows: the wetland is designed to operate in a siphon-based periodic manner, with a hydraulic retention time of 72 hours. Its operation process is divided into two stages: immersion and reoxygenation.

[0060] Submersion stage: Wastewater is transported to the wetland through the inlet pipe 1 wrapped with mesh. The wastewater first enters the inlet side area 6. Under the guidance of the biochar baffle, it flows through the surface layer 10, the iron-sulfur layer 9 and the supporting bottom layer 8 in sequence through uniform infiltration and flow. Then it flows into the outlet side area 7 from the supporting bottom layer 8, and flows from bottom to top through the supporting bottom layer 8, the iron-sulfur layer 9 and the surface layer 10, finally reaching the siphon water level 12.

[0061] Due to the infiltration of wastewater, wetlands typically exhibit an oxygen-deficient environment. In this environment, denitrifying bacteria can utilize electron donors provided by iron and sulfur, as well as organic matter adsorbed on the surface of biochar, for autotrophic denitrification. This mechanism effectively improves nitrate removal and promotes efficient denitrification.

[0062] In addition, the Fe released from iron ore 2+ An efficient electron transport system was constructed for sulfur-reducing bacteria, enabling these microorganisms to transport iron via Fe. 2+ As a terminal electron donor, it drives the metabolic reaction of sulfate reduction to sulfide, and the strong reducing microenvironment formed in this process has a synergistic effect with the iron-sulfur cycle.

[0063] It is noteworthy that this active electron transfer network not only optimizes the sulfur metabolism pathway but also significantly enhances the enzymatic activity of antibiotic-degrading bacteria through intermediate products (such as FeS) generated by the iron-sulfur coupling reaction. The specific oxidoreductases secreted by these bacteria can efficiently cleave recalcitrant groups such as benzene rings and heterocycles in the antibiotic molecule, improving antibiotic removal efficiency. Furthermore, the reaction of sulfides with iron ions effectively reduces the emission of H2S gas. In addition, during the immersion stage, the large microbial attachment area of ​​the biochar baffle 4 facilitates cooperation and communication among anaerobic microorganisms, effectively increasing microbial species abundance and thus achieving the synergistic removal of nitrogen and antibiotics.

[0064] Reoxygenation stage: When the sewage level reaches the top of the inverted U-shaped pipe, a siphon effect is triggered, and the wetland water level drops to the bottom of the outlet pipe. Because the water retention time of the upper part of the sewage in the inlet area 6 does not reach the preset time, it remains in the bottom layer of the wetland and is not discharged. In the next flooding stage, it will be discharged again by siphon effect along with the sewage flow. The drop in water level generates pore suction, drawing in oxygen from the atmosphere; simultaneously, the negative pressure suction principle of the siphon effect can also draw in oxygen from the atmosphere again.

[0065] Therefore, the dissolved oxygen concentration inside the wetland bed increases. In an aerobic environment, nitrifying bacteria (such as ammonia-oxidizing bacteria and nitrite-oxidizing bacteria) require oxygen to perform the nitrification of ammonia. The biochar-material flow guide plate 4 provides an attachment surface for these bacteria, enhancing their colonization and growth. By providing a stable microbial environment, it promotes ammonia oxidation, thereby enhancing the nitrification reaction and effectively improving the wetland's ammonia nitrogen treatment efficiency.

[0066] At the same time, sulfur-oxidizing bacteria can utilize the Fe produced by iron autotrophic denitrification during the submersion stage. 3+ Iron acts as an electron acceptor, promoting the oxidation of sulfur. The 1:1 mass ratio of iron to sulfur helps balance the interaction between sulfate-reducing bacteria and iron and sulfur in redox reactions. Under this configuration, sulfur and iron can form a relatively stable chemical reaction environment in the wetland system, promoting the oxidation of sulfur and the reduction of iron. Furthermore, the reoxygenation stage provides sufficient oxygen for the oxidative degradation of antibiotics, enhancing their degradation and mineralization. When the water level drops to the bottom of the outlet pipe, air enters, the siphon effect is disrupted, and the water level rises again.

[0067] The immersion stage and the reoxygenation stage alternately create anaerobic and aerobic environments without power, thereby promoting the redox reaction in the wetland system, accelerating the sulfur redox cycle, improving electron transfer efficiency, achieving synergistic deep removal of nitrogen and antibiotics, and effectively controlling the generation and release of H2S gas, ensuring the safety of wastewater reuse.

[0068] In actual operation, the influent parameters are shown in Table 1 below: Table 1

[0069] In the specific example, a blank control group was set up. The blank control group was a traditional constructed wetland with added gravel, and the operation method was the same as the embodiment.

[0070] The control group's specific structure: The constructed wetland was 65cm high, 15cm in diameter, and 60cm deep. The wetland consisted mainly of three parts: an inlet pipe, a bed, and an outlet pipe. Both ends of the inlet pipe were wrapped with mesh to trap large particles of pollutants in the wastewater and prevent clogging.

[0071] A perforated pipe, 65cm high and 4cm in diameter, is installed in the center of the wetland bed. This perforated pipe is used for in-situ monitoring of the physicochemical properties of the wastewater (dissolved oxygen and pH, etc.). No flow guide baffles are installed. A conventional effluent pipe is used (compared to an inverted U-shaped siphon effluent pipe). The wetland's filler material, from bottom to top, consists of a support layer (8, 5cm high), a conventional matrix layer (gravel, 55cm high; compared to pyrite), and a surface layer (10, 5cm high). The support layer and surface layer use gravel; the bottom matrix has a particle size of 1-2cm, and the surface matrix has a particle size of 4-8mm.

[0072] Yellow iris 11 was planted in the artificial wetland at a density of 159 roots / square meter and a planting depth of 10 cm.

[0073] The operation mode of this artificial wetland is as follows: the wetland is designed to operate in a continuous flow mode with a hydraulic retention time of 72 hours.

[0074] The specific treatment effects of the constructed wetlands in the examples and the blank control group are shown in Table 2 below: Table 2

[0075] Comparative Example 1 An artificial wetland coupled with enhanced denitrification of iron ore, its operation method, and its application: This siphonic constructed wetland for coupled iron ore is designed as a horizontal subsurface flow type according to the water flow direction. It employs a brick structure with a seepage-proof layer at the bottom to prevent sewage leakage. The designed inflow rate is 8m³ / h. 3The wetland is designed to be 6.00m × 2.00m × 1.10m in size, with an effective water depth of 1.00m. It consists of three main parts: an inlet zone, a substrate zone, and an outlet zone. The inlet zone has seven evenly distributed DN25 inlet holes at the bottom, with a spacing of 25cm between the inlet holes. The substrate layer consists of a 20cm thick layer of fine pebbles (approximately 0.6cm in diameter), a 60cm thick layer of coarse pebbles (approximately 2cm in diameter), and a 20cm thick bottom layer of pebbles (approximately 3cm in diameter). Simultaneously, iron ore (approximately 0.6cm thick) is evenly distributed throughout the wetland at a pebble:iron ore volume ratio of 2:1. A 0.2m × 0.2m sump is located at the lower right bottom of the substrate zone and connected to a DN50 drain pipe, allowing for periodic drainage of the wetland, preventing blockages, and extending its lifespan. A DN50 siphon pipe is installed at the end of the bed to discharge treated water to the outlet area. The wetland is designed to be planted with calamus as the wetland vegetation. Wastewater enters the bed evenly through the DN25 inlet, flowing horizontally within the bed and passing upwards through layers of pebbles with diameters of 3cm, 2cm, and 0.6cm. The water level rises continuously as water enters, submerging the substrate and creating an oxygen-deficient environment. When the water level rises to the top of the outlet bend, a siphon effect is triggered, and the water level drops rapidly. When the water level drops to the bottom of the outlet bend, air enters, the siphon effect is disrupted, water stops flowing from the outlet bend, and the water level rises again, repeating the cycle.

[0076] Comparative Example 2 A combined constructed wetland, its treatment process, and its application: This comparative example provides a combined constructed wetland, including a first constructed wetland and a second constructed wetland, with a length-to-width ratio of 1:3 and a height of 1m. The first constructed wetland, from bottom to top, comprises a first lower substrate (15mm diameter expanded clay aggregate), a space layer, a first transversely perforated water-passing baffle, a first upper substrate (5mm diameter gravel), and wetland plants (iris, calamus, and canna lily, planted at a density of 40 plants / m²). 2 The second constructed wetland, from bottom to top, includes a second lower substrate (8mm biochar), a middle substrate (15mm expanded clay pebbles), a second transverse perforated water-passing baffle, a second upper substrate (5mm gravel), and wetland plants (iris, calamus, and canna lily, planted at a density of 40 plants / m²). 2The first vertical partition (two sets) divides the first constructed wetland into three equal compartments, and the second vertical partition (three sets) divides the second constructed wetland into four equal compartments. The first and second vertical partitions include a bottom water-passing vertical partition and a top water-passing vertical partition, located 5-10 cm from the bottom of the wetland body and the top of the substrate; the bottom and top water-passing vertical partitions are arranged alternately. The first and second transversely perforated water-passing partitions have evenly spaced perforations with a perforation diameter of 4 mm. They are placed on eaves supports around the perimeter of the pool and can be easily removed. Both the first and second transversely perforated water-passing partitions have mesh side plates with pore diameters smaller than the particle size of the first and second upper substrates, and the height of the mesh side plates is greater than the height of the first and second upper substrates, facilitating the removal of the first and second upper substrates. The first inlet is higher than the first upper substrate; the second inlet is higher than the second upper substrate; the second outlet is lower than the second inlet but higher than the second transverse perforated water-passing baffle. The filling height of the first lower substrate is 60% of the height from the bottom of the first constructed wetland to the first transverse perforated water-passing baffle; the height of the space layer is 40% of the height from the bottom of the first constructed wetland to the first transverse perforated water-passing baffle; the filling height of the first upper substrate is 10cm. The filling height of the second lower substrate is 50% of the height from the bottom of the second constructed wetland to the second transverse perforated water-passing baffle; the filling height of the middle substrate is 50% of the height from the bottom of the second constructed wetland to the second transverse perforated water-passing baffle; the filling height of the second upper substrate is 10cm. The siphon drainage pipe connecting the first and second constructed wetlands includes two vertical pipes and an arc-shaped pipe connecting the two vertical pipes. Three equidistant joints are installed on the vertical pipe near the first constructed wetland. Valves are installed at the joints, and only the valve connected to the atmospheric vent is opened to control the siphon water level. The water level at the highest point of the siphon drain pipe is lower than the water level at the first transverse perforated baffle. The liquid level in the first artificial wetland gradually rises and automatically siphons when it exceeds the highest point of the siphon drain pipe; it stops siphoning when it falls below the water level at the atmospheric connection pipe.

[0077] Comparative Example 3 A constructed wetland system and method for treating wastewater using sulfur-iron autotrophic denitrification and a combination of various plants: This comparative example uses an artificial wetland system for wastewater treatment employing pyrometallurgical autotrophic denitrification and a combination of various plants. The system's structures are arranged as follows: Horizontal subsurface flow artificial wetland (first purification zone): A main filler A, consisting of ceramsite, zeolite, and gravel in a volume ratio of 1:2:1, is prepared by crushing, ball milling, sieving, and granulation to obtain a particle size of 10-30 mm, and is uniformly filled within the wetland. Plant combination a within the horizontal subsurface flow artificial wetland consists of water onion, loosestrife, reeds, and pickerelweed, with a planting ratio of 1:1:1:1 and a planting density of 20 plants / m². 2Vertical subsurface flow constructed wetland (second purification zone): A main filler material B with a particle size of 2-6 mm is obtained by crushing, ball milling, sieving, mixing, and granulating siderite (35% by volume), pyrrhotite (25% by volume), and sulfur (40% by volume). This filler material is then uniformly filled into the wetland. Plant combination b in the vertical subsurface flow constructed wetland consists of water chestnut, umbrella sedge, and canna lily, with a planting ratio of 1:1:1 and a planting density of 20 plants / m². 2 Shallow surface flow constructed wetland (third purification zone): Submerged plant assemblage c consists of dwarf Vallisneria natans, Ceratophyllum demersum, and Elodea nuttallii; among which, dwarf Vallisneria natans accounts for 70% of the planting quantity, Ceratophyllum demersum accounts for 15%, and Elodea nuttallii accounts for 15%; the planting density of plant assemblage c is 40 plants / m². 2 Deep-water surface flow constructed wetland (fourth purification zone): Submerged plant combination d consists of Vallisneria natans, Vallisneria natans var. spinosa, and Potamogeton pectinatus, with Vallisneria natans accounting for 45% of the planted area, Vallisneria natans var. spinosa ... 2 Zooplankton, snails, shellfish, shrimp, filter-feeding fish, and predatory fish were introduced into both the shallow and deep surface flow constructed wetlands. The stocking densities were: 30 zooplankton / m³. 3 2 snails / m 2 ; 0.3 shellfish / m 2 Shrimp 1 per m 2 Filter-feeding fish 3 per m 2 150-180g / tail; 25 ferocious fish / acre, 8-12cm / tail.

[0078] Operating steps: S1. Establish the above system; S2. Wastewater is introduced into the inlet of the above system, flows through a distribution channel into a horizontal subsurface flow constructed wetland, the effluent from the horizontal subsurface flow constructed wetland flows into a collection and distribution channel, the effluent from the collection and distribution channel flows into a vertical subsurface flow constructed wetland, the effluent from the vertical subsurface flow constructed wetland flows into a collection and distribution channel, the effluent from the collection and distribution channel flows into a shallow surface flow constructed wetland, the effluent from the shallow surface flow constructed wetland flows into a collection and distribution channel, the effluent from the collection and distribution channel flows into a deep surface flow constructed wetland, and the effluent from the deep surface flow constructed wetland flows into an outlet channel; wherein, the horizontal subsurface flow constructed wetland (first purification zone) has a water depth of 1.2m, a hydraulic retention time of 1 day, and a surface hydraulic load of 0.2m. 3 / (m 2 •d); Vertical subsurface flow constructed wetland (second purification zone): water depth 1.2m, hydraulic retention time 1 day, surface hydraulic loading 0.4m. 3 / (m 2•d); Shallow surface flow constructed wetland (third purification zone) with a water depth of 1.5m, hydraulic retention time of 3 days, and surface hydraulic loading of 0.02m. 3 / (m 2 •d); Deep-water surface flow constructed wetland (Purification Zone 4): water depth 3.5m, hydraulic retention time 2 days, surface hydraulic loading 0.04m. 3 / (m 2 ·d).

[0079] The processing effects of the examples are compared with those of Comparative Examples 1-3, as shown in Table 3.

[0080] Table 3

[0081] The improvement rate (%) of pollutant removal efficiency of the examples compared with Comparative Examples 1-3 is shown in Table 4.

[0082] Table 4

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A siphon-driven constructed wetland system, characterized in that: The bed is arranged from bottom to top as a support bottom layer, an iron-sulfur layer and a surface layer. A flow guide baffle is vertically arranged in the middle of the bed, which divides the bed into an inlet side area and an outlet side area. The flow guide baffle runs through the bottom layer and the iron-sulfur layer and is located above the support bottom layer. The material of the flow guide baffle is biochar. The inlet pipe is connected to the top of the inlet side area, and the outlet pipe is a siphon pipe with an inverted U-shaped structure. The connection point between the inlet of the siphon pipe and the outlet side area is located at a set height of the constructed wetland, which is 1 / 5 to 1 / 2 of the total height of the constructed wetland.

2. The siphon-type constructed wetland system according to claim 1, characterized in that: The top of the siphon pipe with its inverted U-shaped structure is flush with the inlet pipe.

3. The siphon-driven constructed wetland system according to claim 1, characterized in that: The flow guide baffle is located in the middle of the bed, dividing the bed evenly.

4. The siphon-type constructed wetland system according to claim 1, characterized in that: The connection point between the inlet and outlet areas of the siphon is located at 1 / 4 to 1 / 2 of the total height of the constructed wetland.

5. The siphon-type constructed wetland system according to claim 1, characterized in that: In the iron-sulfur layer, the mass ratio of iron matrix to sulfur matrix is ​​0.9-1.1:1; Preferably, the particle size of the filling matrix in the iron-sulfur layer is 4-8 mm.

6. The siphon-type constructed wetland system according to claim 1, characterized in that: The supporting bottom and top layers are composed of gravel, quartz sand, zeolite and / or crushed stone; Preferably, the particle size of the supporting substrate is 1-2 cm, and the particle size of the surface substrate is 4-8 mm. Preferably, the thickness ratio of the support base layer, the iron-sulfur layer and the surface layer is 1-5:35-55:1-5.

7. The siphon-driven constructed wetland system according to claim 1, characterized in that: It also includes perforated tubes, which are inserted into the bed body from top to bottom and extend out of the bed body from the top.

8. The siphon-driven constructed wetland system according to claim 1, characterized in that: The outlet end of the inlet pipe is wrapped with a mesh screen.

9. A method for simultaneously removing antibiotics and nitrogen using the siphon-constructed wetland system described in any one of claims 1-8, characterized in that: The process includes the following steps: a submersion stage and a reoxygenation stage, wherein... During the immersion stage, the wastewater is transported to the inlet area. Under the guidance of the flow-guiding baffles of the biochar material, the wastewater flows from top to bottom through the surface layer, the iron-sulfur layer and the support bottom layer, and then flows into the outlet area at the support bottom layer. It flows evenly from bottom to top through the support bottom layer, the iron-sulfur layer and the surface layer. During this stage, the wastewater is degraded. During the reoxygenation stage, when the wastewater rises to the siphon level, the siphon effect is triggered. The degraded wastewater flows out of the siphon pipe while simultaneously absorbing oxygen in the bed. When the wastewater level drops below the height of the siphon pipe inlet, the outflow stops. The process alternates between the submersion phase and the reoxygenation phase to achieve wastewater treatment.

10. The method for simultaneous removal of antibiotics and nitrogen according to claim 9, characterized in that: The method for preparing the flow guide baffle is as follows: biomass is dried, pulverized, and pyrolyzed to obtain biochar powder; After grinding and sieving the biochar powder, it is mixed with starch adhesive, water is added to adjust it to a plastic state, and then it is pressed into a plate, dried and cured to obtain the final product.

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