A wastewater denitrification device for a recirculating aquaculture system

Abstract

The utility model discloses a kind of wastewater denitrification devices for recirculating aquaculture system, it is related to aquaculture wastewater treatment technical field, device includes: aquaculture solid waste collection pipeline is connected wet underground layer anaerobic hydrolysis zone through feed pipe, first water distribution pipe is laid in wet underground layer anaerobic hydrolysis zone and is communicated with feed pipe, wet underground layer anaerobic hydrolysis zone is also provided with sludge discharge pipe, the upper part of wet underground layer anaerobic hydrolysis zone is laid combination filler, water inlet pipe is connected the middle part of wet underground layer anaerobic hydrolysis zone and is connected with second water distribution pipe, the upper part of wet underground layer anaerobic hydrolysis zone is provided with wetland upper layer filler area, the upper part of wet underground layer anaerobic hydrolysis zone is provided with wetland upper layer filler area, wetland upper layer filler area fills wetland upper layer filler, the surface of wetland upper layer filler is planted wetland plant and lays water collection pipe, water collection pipe is connected outlet pipe. The device realizes the utilization of aquaculture solid waste and wastewater denitrification treatment, improves the water resource recycling rate of recirculating aquaculture system.

Description

Technical Field

[0001] This utility model relates to the field of aquaculture wastewater treatment technology, and in particular to a wastewater denitrification device for a recirculating aquaculture system. Background Technology

[0002] Recirculating aquaculture systems integrate mechanical and biological treatment technologies to treat and recycle aquaculture wastewater. Compared to traditional aquaculture methods, this system has seen rapid development in my country since the 1990s due to its advantages such as high controllability, high efficiency, water conservation, land conservation, and environmental friendliness. During operation, the system removes solid particles, organic matter, ammonia nitrogen, and nitrite nitrogen—substances detrimental to the survival and growth of aquatic products—through a series of solid-liquid separation (sedimentation tanks, microfilters, protein bubble separators), biofilters, aeration, and disinfection facilities. This ensures both the quality and yield of aquaculture products while reducing water consumption.

[0003] Excessive nitrate discharge is one of the factors causing eutrophication in aquaculture systems. Nitrates in recirculating aquaculture systems (RAS) are mainly converted from ammonia nitrogen and nitrite nitrogen. Ammonia nitrogen and nitrite nitrogen in aquaculture water are toxic to aquatic organisms, and are mostly produced by the decomposition of uneaten feed and feces. Ammonia nitrogen is highly toxic to aquatic animals, causing convulsions, coma, and death. When fish and other aquatic organisms are exposed to water containing a certain concentration of nitrite, the content of hemoglobin, which carries oxygen in its blood, decreases, leading to suffocation and death in severe cases. During the circulation process, the RAS utilizes the nitrification process of microorganisms to convert ammonia nitrogen and nitrite nitrogen into nitrate nitrogen. Long-term circulation leads to a large accumulation of nitrate in the aquaculture water. Although nitrate nitrogen is less toxic, a high concentration is still detrimental to fish growth. During the aquaculture period, RAS regularly replaces and replenishes fresh water to reduce the nitrate concentration, generating a certain amount of wastewater containing high concentrations of nitrate. Furthermore, a large amount of wastewater containing high concentrations of nitrates is generated at the end of the aquaculture cycle. Therefore, effectively reducing the nitrate load in the circulating water system can increase the number of water recycling cycles, reduce water resource consumption, and also reduce the discharge of water pollutants.

[0004] Solid waste from aquaculture mainly comes from uneaten feed and excrement from fish. Particulate matter in aquaculture systems can clog fish gills, release harmful substances, and hinder fish growth, potentially leading to death. It is a major problem in all forms of intensive aquaculture. The decomposition of particulate matter consumes dissolved oxygen in the water, releases nitrogen, phosphorus, and pathogens, causing water quality deterioration. Recirculating aquaculture systems commonly use physical methods to remove particulate matter from the water, including common wastewater treatment techniques such as mechanical filtration, gravity separation, membrane filtration, and foam separation. Physical methods are generally easy to construct, maintain, require little space, and are highly adaptable. Microfiltration and other particulate matter separation facilities generate wastewater containing high concentrations of aquaculture solid waste during backwashing; that is, aquaculture solid waste typically has a high water content. Excrement and uneaten feed usually contain large amounts of organic matter and nitrogen and phosphorus nutrients. To utilize aquaculture solid waste as a resource, composting, fertilization, and bioflocculation are commonly used to treat aquaculture solid particles; however, all of these technologies have their limitations. The filtered uneaten feed and fish feces, among other solid wastes, can be fermented or hydrolyzed to produce products that can be used as carbon sources for denitrification in the system. However, in addition to organic carbon sources, these fermented or hydrolyzed solid wastes also contain large amounts of nitrogen and phosphorus pollutants, increasing the difficulty of treatment and necessitating the design of their utilization methods.

[0005] Constructed wetlands are wastewater treatment systems designed and built to mimic natural wetland systems. They aim to remove pollutants from wastewater through the combined action of plants, substrates, and microorganisms. Constructed wetlands offer advantages such as lower energy consumption and lower infrastructure and maintenance costs. The nitrogen removal pathways in constructed wetlands mainly include substrate adsorption, plant uptake, and microbial activity. Nitrification and denitrification by microorganisms contribute the most to nitrogen removal, with denitrification being the primary microbial mechanism. Constructed wetlands possess a complex microenvironment where nitrification, denitrification, and anaerobic ammonium oxidation processes can all occur, enabling the removal of various forms of nitrogen. However, for low-carbon, high-nitrogen wastewater, the overall nitrogen removal efficiency of constructed wetlands is limited due to insufficient carbon sources during the denitrification stage. Furthermore, constructed wetland systems can remove phosphorus through substrate adsorption, microbial activity, and plant uptake, with substrate adsorption being the most important method for phosphorus removal.

[0006] Therefore, solid waste can be directly used as a carbon source for denitrification in recirculating aquaculture systems, achieving nitrogen removal. However, while solid waste ferments to produce soluble organic matter, it also releases large amounts of ammonia nitrogen and phosphate. Even though constructed wetlands are widely used for treating aquaculture wastewater and can simultaneously remove nitrogen and phosphorus, wastewater containing high concentrations of particulate matter can still directly enter the constructed wetlands and cause blockages, making the recirculating aquaculture system less effective than required. Utility Model Content

[0007] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a wastewater denitrification device for recirculating aquaculture systems, which enables the anaerobic hydrolysis products of aquaculture solid waste to become a carbon source, which is then mixed with the high-nitrate nitrogen wastewater from the recirculating aquaculture system and introduced into an artificial wetland for comprehensive purification. This prevents wastewater from clogging the artificial wetland and enhances the effectiveness of the recirculating aquaculture system.

[0008] According to an embodiment of the present invention, a wastewater denitrification device for a recirculating aquaculture system includes:

[0009] Solid waste collection pipeline for aquaculture, feed pipe, water inlet pipe, upflow wetland, anaerobic hydrolysis zone of the lower layer of wetland, first water distribution pipe, sludge discharge pipe, combined packing material, second water distribution pipe, perforated support baffle, upper layer packing area of ​​wetland, upper layer packing material of wetland, wetland plants, water collection pipe, and water outlet pipe;

[0010] The solid waste collection pipeline is connected to the bottom of the anaerobic hydrolysis zone in the wetland underground layer via the feed pipe. The first water distribution pipe is laid at the bottom of the anaerobic hydrolysis zone in the wetland underground layer and connected to the feed pipe. The sludge discharge pipe is also installed at the bottom of the anaerobic hydrolysis zone in the wetland underground layer. The combined packing material is arranged in the upper middle part of the anaerobic hydrolysis zone in the wetland underground layer. The water inlet pipe is connected to the middle of the anaerobic hydrolysis zone in the wetland underground layer and connected to the second water distribution pipe. The wetland upper layer packing material area is set in the upper part of the anaerobic hydrolysis zone in the wetland underground layer. The wetland upper layer packing material area is filled with wetland upper layer packing material. Wetland plants are planted on the surface of the wetland upper layer packing material. The water collection pipe is laid on the surface of the wetland upper layer packing material and connected to the water outlet pipe.

[0011] The wastewater denitrification device for recirculating aquaculture systems according to embodiments of this utility model has at least the following beneficial effects: Addressing the characteristics of high nitrate content, low C (carbon), and low N (nitrogen) in recirculating aquaculture wastewater, this invention proposes an anaerobic hydrolysis process combined with an upflow constructed wetland, achieving resource utilization of aquaculture solid waste and reducing the nitrogen load of the recirculating aquaculture system. After treatment, the removal rate of major pollutants in the effluent is over 90%, and total nitrogen, nitrate nitrogen, ammonia nitrogen, and other major water quality indicators all meet water quality standards. This utility model can efficiently remove nitrate nitrogen from aquaculture wastewater, increasing the number of times aquaculture wastewater can be recycled, reducing water resource consumption, and is suitable for the needs of aquaculture development in areas with scarce fishery resources. It also reduces the discharge of aquaculture pollutants and prevents the indiscriminate discharge of untreated wastewater that could lead to water environment deterioration. Furthermore, this utility model adopts an integrated device, saving land use. By intermittently feeding and stirring the anaerobic hydrolysis zone, the equipment investment and operating costs are reduced compared to conventional biological treatment processes.

[0012] According to some embodiments of the present invention, the upper part of the anaerobic hydrolysis zone of the wetland lower layer and the filler zone of the wetland upper layer are separated by a supporting baffle, and the supporting baffle is provided with through holes.

[0013] According to some embodiments of this utility model, the supporting baffle is made of steel.

[0014] According to some embodiments of this utility model, the diameter of the through hole is ten millimeters.

[0015] According to some embodiments of this utility model, a booster pump is provided between the solid waste collection pipe and the feed pipe, and on the water inlet pipe.

[0016] According to some embodiments of this utility model, the depth range of the anaerobic hydrolysis zone in the wetland underground layer is fifty centimeters to eighty centimeters.

[0017] According to some embodiments of this utility model, the combined filler is an elastic filler made of low-density polyurethane foam and polyethylene.

[0018] According to some embodiments of the present invention, the combined packing material is filled in the upper middle part of the anaerobic hydrolysis zone of the wetland underground layer, and the filling amount of the combined packing material is 60% to 80% of the volume of the anaerobic hydrolysis zone of the wetland underground layer.

[0019] According to some embodiments of this utility model, the wetland top layer filler consists of gravel with a particle size of 10 mm to 25 mm, zeolite with a particle size of 5 mm to 10 mm, ceramsite with a particle size of 2 mm to 5 mm, and quartz sand with a particle size of 2 mm to 5 mm, from bottom to top.

[0020] According to some embodiments of this utility model, the wetland plant is a red-flowered canna.

[0021] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0023] Figure 1 This is a schematic diagram of the wastewater denitrification device for a recirculating aquaculture system according to an embodiment of the present invention;

[0024] Reference numerals: 1. Livestock solid waste collection pipeline; 2. Lifting pump; 3. Feed pipe; 5. Water inlet pipe; 6. Upward flow wetland; 7. Underground anaerobic hydrolysis zone of wetland; 8. First water distribution pipe; 9. Sludge discharge pipe; 10. Combined packing material; 11. Second water distribution pipe; 12. Support baffle; 13. Upper layer packing area of ​​wetland; 14. Upper layer packing material of wetland; 15. Wetland plants; 16. Water collection pipe; 17. Water outlet pipe. Detailed Implementation

[0025] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0026] In the description of this utility model, the use of "first" and "second" is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features or the order of the technical features.

[0027] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0028] Reference Figure 1 This utility model discloses a wastewater denitrification device for a recirculating aquaculture system. The device includes an aquaculture solid waste collection pipe 1, a booster pump 2, a feed pipe 3, a water inlet pipe 5, an upward flow wetland 6, a wetland lower anaerobic hydrolysis zone 7, a first water distribution pipe 8, a sludge discharge pipe 9, a combined packing material 10, a second water distribution pipe 11, a support baffle 12, a wetland upper packing material zone 14, wetland upper packing material 14, wetland plants 15, a water collection pipe 16, and a water outlet pipe 17.

[0029] A lift pump 2 is installed in the middle section of the solid waste collection pipeline 1. The lift pump 2 is connected to the feed pipe 3. A lift pump 2 is also installed in the middle section of the water inlet pipe 5. The feed pipe 3 enters the bottom of the anaerobic hydrolysis zone 7 in the wetland and connects to the first water distribution pipe 8. The first water distribution pipe 8 is laid at the bottom of the anaerobic hydrolysis zone 7 in the wetland. A sludge discharge pipe 9 is installed at the bottom of the anaerobic hydrolysis zone 7 in the wetland. A combined packing material 10 is laid in the upper middle part of the anaerobic hydrolysis zone 7 in the wetland. The water inlet pipe 5 enters the middle of the anaerobic hydrolysis zone 7 in the wetland and connects with a set of packing materials laid in the wetland. The second water distribution pipe 11 in the middle of the underground anaerobic hydrolysis zone 7 is connected. The upper part of the wetland underground anaerobic hydrolysis zone 7 is equipped with wetland top layer filler 14 zone 13. The upper part of the wetland underground anaerobic hydrolysis zone 7 is equipped with wetland top layer filler 14 zone 13, which is separated by a support baffle 12 with through holes. The wetland top layer filler 14 zone 13 is filled with wetland top layer filler 14. Wetland plants 15 are planted on the surface of the wetland top layer filler 14. A water collection pipe 16 is laid on the surface of the wetland top layer filler 14, and the water collection pipe 16 is connected to the water outlet pipe 17.

[0030] Specifically, the wastewater denitrification device in this recirculating aquaculture system has several significant beneficial effects. First, by connecting the aquaculture solid waste collection pipe 1 to the anaerobic hydrolysis zone 7 in the wetland's lower layer, the aquaculture solid waste can directly enter the anaerobic hydrolysis zone for decomposition. Under anaerobic conditions, the organic matter in the solid waste is decomposed by microorganisms to produce small-molecule organic matter, volatile fatty acids, and other substances. These substances not only provide a carbon source for the subsequent denitrification process, which helps the growth and metabolism of denitrifying bacteria and promotes the reduction of nitrates to nitrogen gas, thus achieving efficient wastewater denitrification, but also realize the resource utilization of aquaculture solid waste, reduce waste pollution to the environment, and improve the overall resource utilization rate of the aquaculture system.

[0031] Secondly, the anaerobic hydrolysis zone 7 in the lower layer of the wetland is equipped with a first water distribution pipe 8 connected to the feed pipe 3, and an inlet pipe 5 connected to a second water distribution pipe 11. This water distribution method ensures that the water entering the wetland is evenly distributed, avoiding localized water flow obstruction or excessively rapid flow, guaranteeing sufficient contact between microorganisms and water throughout the entire wetland system, and improving treatment efficiency. Simultaneously, uniform water distribution also helps maintain a healthy ecological environment within the wetland, promoting the growth and reproduction of microorganisms, further enhancing the denitrification effect of the device.

[0032] Furthermore, a combined packing material 10 is arranged in the upper part of the anaerobic hydrolysis zone 7 in the wetland lower layer. The combined packing material 10 has a large specific surface area, which can provide abundant attachment and growth sites for microorganisms, increase the amount of microorganisms attached, and improve their activity. Microorganisms form a biofilm on the surface of the combined packing material 10, which can more effectively adsorb, degrade, and transform pollutants in wastewater, thereby improving the device's wastewater treatment capacity and ensuring the stability and reliability of denitrification effect.

[0033] In addition, the wetland top layer filler 14 in zone 13 is filled with wetland top layer filler 14 and planted with wetland plants 15. These wetland plants 15 not only absorb nutrients such as nitrogen and phosphorus from the wastewater, further purifying the water quality, but also transport oxygen into the wetland through their roots, creating aerobic, anoxic, and anaerobic microenvironments. This is conducive to the growth and synergistic effect of nitrifying and denitrifying bacteria, thus enhancing the denitrification process. At the same time, the presence of the wetland plants 15 also beautifies the environment and increases the ecological landscape value of the device.

[0034] Finally, by connecting the water inlet pipe 16 to the water outlet pipe 17, the treated water that meets the standards can be discharged in a timely manner, ensuring the continuous and stable operation of the device, improving the water resource recycling rate of the recirculating aquaculture system, and reducing aquaculture costs.

[0035] The following detailed description, in conjunction with the accompanying drawings, illustrates the specific implementation method of the wastewater denitrification device for this recirculating aquaculture system.

[0036] The wastewater denitrification device for this recirculating aquaculture system mainly consists of the following components: aquaculture solid waste collection pipe 1, feed pipe 3, water inlet pipe 5, upward flow wetland 6, wetland lower anaerobic hydrolysis zone 7, first water distribution pipe 8, sludge discharge pipe 9, combined packing material 10, second water distribution pipe 11, support baffle 12, wetland upper layer packing material zone 14 13, wetland upper layer packing material 14, wetland plants 15, water collection pipe 16, and water outlet pipe 17.

[0037] First, the main structure of the upflow wetland 6 is constructed using materials such as concrete or plastic to create the wetland pool body (not shown in the diagram), ensuring good sealing and stability. The wetland pool is divided into a lower anaerobic hydrolysis zone 7 and an upper packing material zone 14 (13). The lower anaerobic hydrolysis zone 7 is located at the bottom of the wetland pool, and the upper packing material zone 14 (13) is located above it. These two zones are separated by a supporting baffle 12, which is made of a material with sufficient strength and permeability, such as porous steel plate, to ensure smooth water flow. An aquaculture solid waste collection pipe 1 is installed, connecting one end to the solid waste discharge port of the recirculating aquaculture system, and the other end to the bottom of the lower anaerobic hydrolysis zone 7 via an inlet pipe 3. The inlet pipe 3 is made of corrosion-resistant plastic to ensure it will not corrode during solid waste transport.

[0038] A first distribution pipe 8 is laid at the bottom of the anaerobic hydrolysis zone 7 in the wetland lower layer. The first distribution pipe 8 is a perforated pipe with an aperture designed according to actual needs. The first distribution pipe 8 is connected to the feed pipe 3, so that the incoming solid waste can be evenly distributed at the bottom of the anaerobic hydrolysis zone 7 in the wetland lower layer. A water inlet pipe 5 is installed, with one end connected to the wastewater discharge port of the recirculating aquaculture system and the other end connected to the middle of the anaerobic hydrolysis zone 7 in the wetland lower layer, and connected to the second distribution pipe 11. The second distribution pipe 11 is also a perforated pipe, with an aperture and aperture spacing similar to the first distribution pipe 8, to ensure that wastewater can enter the anaerobic hydrolysis zone 7 in the wetland lower layer evenly. A sludge discharge pipe 9 is also installed at the bottom of the anaerobic hydrolysis zone 7 in the wetland lower layer. The sludge discharge pipe 9 is a plastic pipe, which periodically discharges the sludge accumulated in the anaerobic hydrolysis zone 7 in the wetland lower layer, preventing excessive sludge from affecting the treatment effect of the device.

[0039] A combined packing material 10 is installed in the upper and middle parts of the anaerobic hydrolysis zone 7 in the wetland underground layer. The combined packing material 10 is made of materials such as polyethylene, polypropylene, or a combination of low-density polyurethane foam and polyethylene elastic packing. Among the low-density polyurethane foam packing and polyethylene elastic packing, the low-density polyurethane foam packing is in block form and is filled in layers in the upper part of the anaerobic hydrolysis zone 7 in the wetland underground layer; the polyethylene elastic packing is in string form and is suspended and filled in the lower layer of low-density polyurethane foam packing. The low-density polyurethane foam has a density of 10 to 20 kg per cubic meter and a pore size of 200 to 2000 micrometers, which allows microorganisms to attach while filtering and retaining particulate matter; it also has a large specific surface area and good bio-adhesion. The combined packing material 10 is evenly arranged in the anaerobic hydrolysis zone 7 of the wetland underground layer. The filling height of the packing material is determined according to actual needs. Specifically, the combined packing material 10 is filled in the middle and upper part of the anaerobic hydrolysis zone 7 of the wetland underground layer. The filling amount of the combined packing material 10 is 60% to 80% of the volume of the anaerobic hydrolysis zone 7 of the wetland underground layer, and the depth of the anaerobic hydrolysis zone 7 of the wetland underground layer is 50 cm to 80 cm.

[0040] If the filling volume is too low, less than 60%, there will be insufficient attachment sites for microorganisms in the anaerobic hydrolysis zone 7 of the wetland's lower layer. The limited number of microorganisms will prevent them from fully degrading and transforming pollutants in the wastewater, resulting in poor wastewater treatment and low denitrification efficiency. Conversely, if the filling volume is too high, exceeding 80%, it will increase the water flow resistance in the anaerobic hydrolysis zone 7 of the wetland's lower layer, slow down the water flow velocity, and may even lead to obstructed water flow. This will affect the sufficient contact between wastewater and microorganisms, reduce treatment efficiency, and may also increase the construction cost and operating energy consumption of the device.

[0041] Wetland top layer filler 14 is filled in zone 13 of wetland top layer filler 14. The wetland top layer filler 14 can be made of materials such as gravel or expanded clay, and the particle size is selected according to actual needs. Wetland plants 15, such as reeds, calamus, and canna lilies, are planted on the surface of the wetland top layer filler 14. These plants have strong pollution tolerance and adaptability, and can effectively absorb nutrients from wastewater. During planting, the plant seedlings are evenly planted on the surface of the wetland top layer filler 14. The planting density is determined according to the growth characteristics of the plants and treatment requirements, generally ten to twenty plants per square meter.

[0042] A water collection pipe 16 is laid on the surface of the wetland top layer filler 14. The water collection pipe 16 is a perforated pipe, and the hole diameter and hole spacing are designed according to actual needs. The water collection pipe 16 is connected to the water outlet pipe 17. The water outlet pipe 17 discharges the treated water that meets the standards from the device and enters the reclaimed water tank of the recirculating aquaculture system for biological filtration to realize the recycling of water resources; or it can be directly discharged after filtration.

[0043] During operation, aquaculture solid waste enters the anaerobic hydrolysis zone 7 in the lower layer of the wetland through the aquaculture solid waste collection pipe 1 and the feed pipe 3, where it decomposes under anaerobic conditions, providing a carbon source for the subsequent denitrification process. Wastewater from the recirculating aquaculture system enters the anaerobic hydrolysis zone 7 in the lower layer of the wetland evenly through the inlet pipe 5 and the second distribution pipe 11. After mixing with the anaerobic hydrolysis products, nitrification and denitrification reactions occur under the action of microorganisms, achieving denitrification. The treated water is further purified by the upper layer packing material 14 and wetland plants 15 before being discharged through the collection pipe 16 and the outlet pipe 17.

[0044] Regular maintenance of the equipment is required, including cleaning the sludge discharged from the sludge discharge pipe 9, checking the unobstructed flow of the pipeline system, observing the growth of wetland plants 15 and replanting or pruning them in a timely manner, in order to ensure the normal operation and treatment effect of the equipment.

[0045] Through the above specific implementation methods, the wastewater denitrification device for this recirculating aquaculture system can effectively realize the resource utilization of aquaculture solid waste and the denitrification treatment of wastewater, improve the water resource recycling rate of the recirculating aquaculture system, and has good application prospects.

[0046] Specifically, in some embodiments, the depth of the anaerobic hydrolysis zone 7 in the wetland is fifty centimeters, and the combined filler 10 is an elastic filler made of low-density polyurethane foam and polyethylene, which is filled in the upper part of the anaerobic hydrolysis zone 7 in the wetland, and the filling amount is 80% of the volume of the anaerobic hydrolysis zone 7 in the wetland.

[0047] In some embodiments, the wetland top layer filler 14 is composed of gravel with a particle size of 10 mm to 25 mm, zeolite with a particle size of 5 mm to 10 mm, ceramsite with a particle size of 2 mm to 5 mm, and quartz sand with a particle size of 2 mm to 5 mm from bottom to top; the depth of the wetland top layer filler 14 is one meter.

[0048] Specifically, during the device construction phase, after the structural construction of the wetland top-layer filler zone 13 is completed, the filler work begins. First, the wetland top-layer filler zone 13 is cleaned to ensure its interior is clean, flat, and free of debris and sharp protrusions, so as not to affect the filling effect and subsequent plant growth. Gravel with a particle size of 10 to 25 millimeters is filled first. The gravel is evenly poured into the bottom of the wetland top-layer filler zone using conveying equipment or manual handling. During the filling process, long-handled tools such as rakes are used to properly level and compact the gravel, making its surface smooth. The filling height is determined according to design requirements. This layer of gravel has a relatively large particle size, providing good permeability and support, ensuring a stable support foundation for the upper filler layer while ensuring smooth water flow and preventing blockages. Next, zeolite with a particle size of 5 to 10 millimeters is filled. Zeolite has a unique porous structure and ion exchange capacity, effectively adsorbing pollutants such as ammonia nitrogen in wastewater. Zeolite is slowly poured into the wetland top-layer packing area, covering the gravel layer. It is then spread and leveled using tools to ensure even filling. The zeolite layer further enhances the device's ability to remove pollutants from wastewater, particularly the adsorption and conversion of ammonia nitrogen. Next, ceramsite with a particle size of two to five millimeters is added. Ceramsite has advantages such as a large specific surface area, good adsorption performance, and light weight, providing abundant attachment and growth sites for microorganisms. The ceramsite is evenly spread on the zeolite layer. During filling, care is taken to avoid uneven accumulation of ceramsite, which would affect the uniform distribution of water flow. The presence of the ceramsite layer is conducive to the growth and reproduction of microorganisms, promoting biofilm formation and thus enhancing the degradation of organic matter and nitrogen in the wastewater. Finally, quartz sand with a particle size of two to five millimeters is added. Quartz sand has excellent filtration performance, further removing suspended solids and fine particles from the wastewater. The quartz sand is carefully poured into the wetland top-layer packing area, covering the ceramsite layer and filling to the top of the wetland top-layer packing area. After filling is completed, the surface of the top layer of filler in the wetland is leveled to ensure that the surface is flat and free of obvious unevenness.

[0049] In some embodiments, the lower anaerobic hydrolysis zone 7 and the upper packing material 14 of the wetland can be separated by a perforated steel support baffle 12, which is covered with round holes of 10 mm in diameter. In other embodiments, in the wastewater denitrification device of this recirculating aquaculture system, the upper part of the lower anaerobic hydrolysis zone 7 and the upper packing material zone 13 of the wetland are effectively separated by the support baffle 12, which is provided with through holes to ensure smooth water flow and material exchange. During the device construction process, after the main structure of the wetland pool is completed and the lower anaerobic hydrolysis zone 7 and the upper packing material zone 13 are divided, the support baffle 12 is installed. The support baffle 12 can be made of a material with certain strength and corrosion resistance, such as high-density polyethylene plastic sheet. This material can not only withstand the pressure from the upper packing material and wetland plants, but also maintain stable performance in a humid environment for a long time and is not easily damaged.

[0050] Specifically, in some embodiments, the pipes are all made of PVC material and connected with adhesive. The first water distribution pipe 8, the second water distribution pipe 11 and the water receiving pipe 16 are divided into main pipes and branch pipes. The nominal diameter of the main pipe is 100 mm and the nominal diameter of the branch pipe is 75 mm. The branch pipes of the first water distribution pipe 8 are staggered at 45° upward along the vertical pipe axis, and the branch pipes of the second water distribution pipe 11 are staggered at 45° downward along the vertical pipe axis with a hole diameter of 3 mm. The branch pipes of the water receiving pipe 16 are evenly perforated.

[0051] Specifically, in some embodiments, the wastewater denitrification device for the recirculating aquaculture system operates intermittently, with each hydraulic retention period lasting approximately 4 to 6 days.

[0052] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] Of course, this utility model is not limited to the above-described embodiments. Those skilled in the art can make equivalent modifications or substitutions without departing from the spirit of this utility model. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A wastewater denitrification device for a recirculating aquaculture system, characterized in that, include: The system includes a solid waste collection pipeline for livestock farming, a feed pipe, a water inlet pipe, an upflow wetland, a lower anaerobic hydrolysis zone in the wetland, a first water distribution pipe, a sludge discharge pipe, combined packing material, a second water distribution pipe, a support baffle, a higher layer packing material zone in the wetland, higher layer packing material in the wetland, wetland plants, a water collection pipe, and a water outlet pipe. The aquaculture solid waste collection pipeline is connected to the bottom of the wetland underground anaerobic hydrolysis zone through the feed pipe. The first water distribution pipe is laid at the bottom of the wetland underground anaerobic hydrolysis zone and connected to the feed pipe. The sludge discharge pipe is also installed at the bottom of the wetland underground anaerobic hydrolysis zone. The combined packing material is laid in the middle and upper part of the wetland underground anaerobic hydrolysis zone. The water inlet pipe is connected to the middle part of the wetland underground anaerobic hydrolysis zone and connected to the second water distribution pipe. The wetland underground anaerobic hydrolysis zone is set in the upper part of the wetland underground anaerobic hydrolysis zone. The wetland underground packing material zone is filled with the wetland underground packing material. Wetland plants are planted on the surface of the wetland underground packing material. The water collection pipe is laid on the surface of the wetland underground packing material and connected to the water outlet pipe.

2. The wastewater denitrification device for a recirculating aquaculture system according to claim 1, characterized in that, The upper part of the anaerobic hydrolysis zone in the wetland's lower layer and the upper layer of the filler zone in the wetland are separated by a supporting baffle, which is provided with through holes.

3. The wastewater denitrification device for a recirculating aquaculture system according to claim 2, characterized in that, The supporting baffle is made of steel.

4. The wastewater denitrification device for a recirculating aquaculture system according to claim 2, characterized in that, The diameter of the through hole is 10 mm.

5. The wastewater denitrification device for a recirculating aquaculture system according to claim 1, characterized in that, A booster pump is installed between the solid waste collection pipe and the feed pipe, and on the water inlet pipe.

6. The wastewater denitrification device for a recirculating aquaculture system according to claim 1, characterized in that, The depth of the anaerobic hydrolysis zone in the wetland underground layer ranges from 50 cm to 80 cm.

7. The wastewater denitrification device for a recirculating aquaculture system according to claim 1, characterized in that, The combined filler is an elastic filler made of low-density polyurethane foam and polyethylene.

8. The wastewater denitrification device for a recirculating aquaculture system according to claim 1, characterized in that, The combined packing material is filled in the upper middle part of the anaerobic hydrolysis zone of the wetland underground layer, and the filling amount of the combined packing material is 60% to 80% of the volume of the anaerobic hydrolysis zone of the wetland underground layer.

9. The wastewater denitrification device for a recirculating aquaculture system according to claim 1, characterized in that, The wetland top layer filler consists of gravel with a particle size of 10 mm to 25 mm, zeolite with a particle size of 5 mm to 10 mm, ceramsite with a particle size of 2 mm to 5 mm, and quartz sand with a particle size of 2 mm to 5 mm, from bottom to top.

10. The wastewater denitrification device for a recirculating aquaculture system according to claim 1, characterized in that, The wetland plant is the red-flowered canna.

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