A purification device and a circulating water aquaculture water quality purification system

Abstract

The utility model belongs to water quality purification technical field provides a kind of purification device, circulating water aquaculture water quality purification system, the device includes by first filter bag, second filter bag and third filter bag that inner layer nest together outward, water flow gap is provided between adjacent filter bag;Water hole is opened on first filter bag, second filter bag and third filter bag, water source entering purification device forms axial-radial-axial flow path in water flow gap by water hole, finally reaches the water purification effect of denitrification and filtration.This purification device can filter organic particulate matter in water source and the whole process device stability is high;And have filtration function and adsorb particulate function;Based on the assembly of purification device, the water oxygen content gradient of the present purification system can be reduced to anaerobic state, thereby causing short-range nitrification reaction to remove nitrogen from water body;And the system has the characteristics of low energy consumption, good purification effect and compact system, thereby reducing the total investment cost.

Description

Technical Field

[0001] This application relates to the field of water purification technology, and in particular to a purification device and a recirculating aquaculture water purification system. Background Technology

[0002] The development of high-density recirculating aquaculture technology aims to improve land utilization and conserve water resources. One of the core requirements of recirculating aquaculture is to address the pollution caused by excrement and uneaten feed from various aquatic products. Unlike livestock farming, where excrement and urine can be mechanically cleaned and waste gases can be easily removed through ventilation, aquatic products release their own excrement and urine into the water they inhabit. Ammonia nitrogen and carbon dioxide are also excreted into the water through their gills. Aquatic products are constantly surrounded by their own excreted wastewater. In large bodies of water like rivers and lakes, where the density of aquatic products is low, this doesn't affect their survival. However, in high-density recirculating aquaculture, if the wastewater isn't properly treated, its concentration will increase, eventually leading to the death of the aquatic products.

[0003] There is currently a great deal of research on "manure water" treatment, which can be summarized into two methods. Method 1: First, the water flows out of the aquaculture pond and then physical filtration is used to separate particulate matter from the water. For example, microfiltration machines, sand filters, hollow fiber ultrafiltration machines, and air flotation reactors are used for separation. Then, the separated water is treated by a biological system (converting ammonia nitrogen and nitrite in the water into nitrate) to obtain water quality that meets the requirements for reuse, and then it is circulated back to the aquaculture pond. The other method is to use biofloc technology for in-situ treatment to ensure the sustainability of the aquaculture environment. Simply put, organic carbon sources (commonly brown sugar and molasses) are added to the aquaculture water, and the "manure water" is used as nutrients to cultivate heterotrophic bacteria and produce a large number of bioflocs. The bioflocs themselves become fish food. This technology has been successfully used in shrimp and tilapia farming. However, because the bioflocs can affect the respiration of the gills, this technology is not suitable for most fish. The first method is the mainstream approach.

[0004] However, while the first method is widely used, it still has some problems, mainly in three aspects: 1. It requires high precision in separating particulate matter (uneaten feed and feces) from the water, in other words, it places high demands on the filtration equipment. If separation is inadequate, many fine particles will flow into the biological treatment tank, providing an organic carbon source for the water and thus fostering a large number of heterotrophic bacteria. Due to the dominant position of heterotrophic bacteria, they will crowd out the living space of nitrifying bacteria, thereby affecting the efficiency of nitrification. 2. The entire process lacks denitrification. Since the dissolved oxygen in the circulating water flowing out of the aquaculture tank is usually not lower than 5 mg / L (fish require high dissolved oxygen), there is no anaerobic stage; only nitrification can occur, and denitrification cannot occur. The nitrification reaction that occurs is as follows:

[0005] 1.NH4 + +1.5O2→NO2 - +H₂O+2H + ①

[0006] 2.NO2 - +0.5O2→NO3 - ②

[0007] As shown in equation ②, nitrogen ultimately remains in the water as nitrate. Over a farming season, its concentration accumulates to a very high level, still posing a certain stress to the fish. 3. The biochemical reactions are mainly completed by nitrifying bacteria. However, nitrifying bacteria themselves are not very efficient; only 300g to 600g of ammonia nitrogen is nitrified per cubic meter of packing material per day. Therefore, the biological system requires a relatively large volume and a large amount of packing material, which is why this part of the investment cost accounts for the highest proportion of all aspects of recirculating aquaculture.

[0008] To address the aforementioned problems, those skilled in the art have made numerous attempts to achieve breakthroughs. For example, patent CN208641958U discloses a fish feces collection filter bag, belonging to the field of aquaponics systems. It includes a cloth bag, an inlet pipe, and a first filter layer. The inlet pipe is located at the bag opening, the first filter layer is located in the middle of the bag, and a second filter layer is located at the bottom of the bag. It also includes a water distribution structure connected to the outlet of the inlet pipe. This filter bag can utilize a simple structure to filter, collect, and ferment fish feces in the aquarium water, and it also has the advantages of low manufacturing cost and reduced user investment. However, because this filter bag cannot create an anaerobic environment, it cannot denitrify the water; it can only collect feces and filter. Furthermore, due to the design of its filter layers, even when using large-pore materials like cotton, it is easily clogged by uneaten food and feces in the water, requiring frequent cleaning and increasing operating costs. Conversely, since the filter layer is made of materials with large gaps, such as cotton, it is difficult to guarantee the water output effect, and a large amount of particulate matter will inevitably flow out of the filter bag.

[0009] For example, patent CN216038838U discloses an anaerobic fermentation filtration device and a small-scale integrated farming and aquaculture system. The anaerobic fermentation filtration device includes a filter bag and an inlet pipe. The filter bag is located at one end of the inlet pipe, covering and tightly binding the inlet pipe. The other end of the filter bag, away from the inlet pipe, is designated as the outlet, which is also tightly bound in a contracted shape. The outlet flow rate is 3%–5% of the inlet pipe flow rate. The filter bag is made of fabric with an equivalent pore size of 75μm–85μm. Anaerobic bacteria are loaded onto the inner wall of the filter bag. The small-scale integrated farming and aquaculture system includes an aquaculture pond, a dynamic anaerobic fermentation tank, and an aerobic fermentation tank; these three components are arranged in a three-dimensional configuration at different heights. Although the structure is simple, it has some insurmountable problems. First, the dissolved oxygen in the water coming out of the aquaculture pond is high (determined by the fish's survival needs, usually DO>5mg / L). When the water flows through the anaerobic fermentation filter, it is difficult to create an anaerobic environment. Without an anaerobic environment, the loaded anaerobic bacteria cannot function. Second, the outlet flow rate is 3% to 5% of the inlet flow rate, which means that 95% to 97% of the water exits through the micropores on the bag wall. The pore size is equivalent to 75μm to 85μm. If the water in the inlet pipe does not contain uneaten feed or feces, there will be no blockage. However, if the water in the inlet pipe comes directly from the aquaculture pond without pretreatment, it will inevitably be rich in uneaten feed, feces, and other particulate matter, making it extremely easy to cause blockage. This necessitates frequent cleaning, resulting in a huge workload, and the system is also difficult to stabilize. Utility Model Content

[0010] To address the shortcomings of existing technologies, this utility model provides a purification device and a recirculating aquaculture water quality purification system, which improves the purification effect by rapidly consuming oxygen in a gradient and triggering a short-range nitrification reaction, thereby achieving efficient recirculating aquaculture water quality purification at low cost.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] The first aspect of this utility model provides a purification device, including a first filter bag, a second filter bag, and a third filter bag nested together from the inside out, with water flow gaps between adjacent filter bags; the first filter bag, the second filter bag, and the third filter bag are provided with water outlet holes, and the water source entering the purification device forms an axial-radial-axial flow path in the water flow gaps between the filter bags through the water outlet holes, so as to create an anaerobic environment to induce short-range nitrification reaction to remove nitrogen and filter the water source.

[0013] Based on the aforementioned technical means, the purification device of this application utilizes a nested hierarchical structure of a first filter bag, a second filter bag, and a third filter bag, combined with an axial-radial-axial flow path, to collect organic particulate matter in the water source. Specifically, large particles in the water source (large particles in this application refer to particles with a larger particle size relative to the micropores on the filter bags) may accumulate in the first, second, and third filter bags. If too many large particles accumulate in one of the filter bags, the flow resistance will also increase. Under the action of the inlet water pressure, the device of this application can automatically push these large particles forward, thereby achieving a dynamic balance of particulate matter in each filter bag. During the water flow, dissolved oxygen in the water is rapidly consumed and decreases in a gradient, promoting the formation of an anaerobic environment.

[0014] Furthermore, the diameter and length of the first filter bag, the second filter bag, and the third filter bag increase sequentially, and the upper ends of the first filter bag, the second filter bag, and the third filter bag are coaxially sealed together.

[0015] Based on the aforementioned technical means, the increasing diameter of the first, second, and third filter bags, combined with the increasing length difference, can construct an axial-radial-axial flow path, thereby increasing the water flow efficiency and avoiding local blockages, achieving long-term maintenance-free operation. Furthermore, the coaxial sealing of the upper ends of the first, second, and third filter bags forms an axially fixed end, which, combined with the increasing diameter design, constitutes a natural support frame, effectively preventing the purification device from collapsing or deforming and improving the device's filtration stability. The increasing length design allows the impact force of the incoming water flow to gradually decrease along the axial direction, improving the sealing reliability of the upper part of the device.

[0016] Furthermore, the top of the first filter bag is provided with a water inlet, and the water outlet at the bottom is a flow-limiting hole. The diameter of the flow-limiting hole is preferably 10mm to 20mm, which is conducive to the collection of organic particles and will not cause blockage.

[0017] Furthermore, the water outlet holes opened on the upper periphery of the second filter bag near the water inlet are water distribution holes for radial diversion of the water source. Due to density (the density referred to in this application is that the density of organic particles is usually 1.05 to 1.2 times the density of water), organic particles will accumulate in the gap between the second filter bag and the first filter bag. Similarly, when the accumulation is too large, it will also flow into the third filter bag along with the water flow through the opened water outlet holes.

[0018] Furthermore, the outlet at the bottom of the third filter bag serves as a sludge discharge port, allowing excess organic particles to be discharged and preventing clogging. Under these conditions, the water passing through the micropores in the wall of the third filter bag becomes the treated water required for the final product.

[0019] Furthermore, at least one of the first filter bag, the second filter bag, and the third filter bag is made of plastic fiber felt.

[0020] Based on the aforementioned technical means, the filter bag made of plastic fiber felt in this application has a number of micropores, which are at the micrometer level. Under this structure, when water enters the first filter bag, due to the large number of micropores in the filter bag itself, some water will flow into the second filter bag through the micropores, then through the micropores on the second filter bag into the third filter bag, and then through the micropores on the third filter bag into the purification chamber connected to the outside of the purification device. The purification chamber can be various filter barrels, boxes, pools, etc. During the process of passing through the micropores, particles larger than the micropore diameter are intercepted. If the purification device is used for a sufficiently long time, a large number of microorganisms will be attached to the inside and outside of the first, second, and third filter bags, forming a biofilm layer, so that each filter bag not only has a filtration function, but also has a certain function of adsorbing particulate matter.

[0021] Furthermore, the purification device is equipped with packing material.

[0022] Based on the above technical means, the purpose of setting up the packing material in this application is to increase the surface area for biological attachment and improve the biological treatment capacity.

[0023] The second aspect of this utility model provides a recirculating aquaculture water purification system, which is equipped with at least one of the above-mentioned purification devices.

[0024] Furthermore, the purification system is equipped with at least one agitator.

[0025] Furthermore, the purification system is equipped with wastewater return circulation pipes and / or wastewater filtration and sludge discharge pipes. Wastewater exiting the sludge discharge port is wholly or partially returned, similar to "activated sludge return" in domestic wastewater treatment. The wastewater exiting the sludge discharge port has extremely low dissolved oxygen levels. After mixing with water from the aquaculture pond, it flows into the first filter bag, significantly reducing dissolved oxygen levels and greatly contributing to system stability. Excess organic particles are filtered out, reducing the system's treatment load. The specific method used in a project depends on the actual amount of organic particles.

[0026] Based on the above-mentioned technical means, the purification system of this application utilizes the sewage return circulation pipeline to accelerate the formation of anoxic and anaerobic environments within the purification system, thereby promoting the occurrence of short-cut nitrification and achieving the purpose of denitrification. Compared with existing purification systems, it has the advantages of reducing volume and the amount of packing material used, and reducing investment costs.

[0027] The beneficial technical effects of this utility model are as follows:

[0028] This utility model purification device utilizes a first filter bag, a second filter bag, and a third filter bag nested together from the inside out, combined with an axial-radial-axial flow path to filter particulate matter in the water source, and the device has high stability throughout the process; and by utilizing the microporous characteristics of the materials of the first filter bag, the second filter bag, and the third filter bag, the device has both filtration and particulate matter adsorption functions.

[0029] Based on the assembly of the purification device, this utility model purification system utilizes short-range nitrification reaction to reduce system energy consumption, reduce the organic carbon source requirement in the denitrification stage, thereby reducing operating costs, improving purification effect, reducing sludge production and system volume, and thus reducing total investment cost. Attached Figure Description

[0030] The accompanying drawings, incorporated in and forming part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without inventive effort. In the drawings:

[0031] Figure 1 This is a schematic diagram of the purification device structure shown in one embodiment of this application;

[0032] Figure 2 This is a schematic diagram of the purification device structure shown in another embodiment of this application;

[0033] Figure 3 This is a schematic diagram of the purification system structure shown in one embodiment of this application.

[0034] Figure Labels

[0035] 1: Purification device; 2: Purification chamber; 3: Agitator; 4: Filter; 5: Post-treatment system; 21: Water outlet pipe; 22: Sewage filter sludge discharge pipe; 23: Sludge discharge pipe tee; 24: Regulating valve; 25: Return pump; 26: Sewage return circulation pipe; 27: Sewage discharge pipe; 28: Water inlet pipe; 11: First water inlet; 12: Second water inlet; 13: First filter bag; 14: Second filter bag; 15: Third filter bag; 131: Flow limiting hole; 141: Water distribution hole; 151: Sludge discharge port; 16: Packing material. Detailed Implementation

[0036] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should be understood that certain features of this invention (described in the context of separate embodiments for clarity) may also be provided in combination in a single embodiment. Conversely, multiple features of this invention (described in the context of a single embodiment for brevity) may also be provided separately or in any suitable combination or, where appropriate, in any other described embodiment of this invention. Certain features described in the context of various embodiments will not be considered essential features of those embodiments unless the embodiment is inoperable without those elements. The present invention is further illustrated below by specific examples; however, it should be noted that the specific process conditions and results described in the embodiments of this invention are for illustrative purposes only and should not be construed as limiting the scope of protection of this invention. All equivalent changes or modifications made in accordance with the spirit and essence of this invention should be covered within the scope of protection of this invention.

[0037] First, it should be noted that the plastic fiber felt used in the first filter bag 13, the second filter bag 14, and the third filter bag 15 of this application is a commercially available material. Individual filter bags made of plastic fiber felt are widely used in industry for filtering liquids or removing dust from air; they are inexpensive and readily available. Therefore, this application does not involve improvements to the materials, and all contents meet the requirements for protection of a utility model.

[0038] like Figure 1 As shown, this utility model provides a purification device 1, including a first filter bag 13, a second filter bag 14, and a third filter bag 15 nested together from the inside out, with water flow gaps between adjacent filter bags; the first filter bag 13, the second filter bag 14, and the third filter bag 15 are provided with water outlet holes, and the water source entering the purification device 1 forms an axial-radial-axial flow path in the water flow gap through the water outlet holes, so as to form an anaerobic environment to induce short-range nitrification reaction to remove nitrogen and filter the water source.

[0039] Furthermore, the purification device 1 of this application can be used to purify aquaculture water and other wastewater, which usually contains a large amount of particulate matter in the water, such as uneaten feed, feces of aquatic products such as fish and shrimp, animal carcasses, mucus secretions and shed epidermal tissues and other biological metabolic products, organic debris such as decaying plant remains in aquaculture ponds, colloidal aggregates formed by microbial metabolic products, silt or clay particles, mineral sediments, bacteria, plankton (such as algae and protozoa) and bioflocs formed by their metabolic products, etc.

[0040] Furthermore, the first filter bag 13, the second filter bag 14, and the third filter bag 15, nested together from the inside out, constitute a nested hierarchical structure, enabling layered filtration to effectively disperse impurity load and avoid rapid clogging of a single filter bag, resulting in a longer service life. Moreover, large particles in the water source may accumulate in the first filter bag 13, the second filter bag 14, and the third filter bag 15. If too many large particles accumulate in one of the filter bags, the flow resistance will increase. Under the pressure of the incoming water, the device can automatically propel these large particles forward, thereby achieving a dynamic balance of particles in each filter bag. During water flow, dissolved oxygen in the water is rapidly consumed, decreasing in a gradient, promoting the formation of an anaerobic environment.

[0041] Furthermore, the axial-radial-axial flow path of this application can prolong the contact time between particulate matter in the water and the filter bag, thereby improving the purification effect and increasing the purification efficiency.

[0042] Furthermore, the diameters and lengths of the first filter bag 13, the second filter bag 14, and the third filter bag 15 increase sequentially, and the upper ends of the first filter bag 13, the second filter bag 14, and the third filter bag 15 are coaxially sealed together. Specifically, the diameter D1 of the first filter bag 13 < the diameter D2 of the second filter bag 14 < the diameter D3 of the third filter bag 15, and the length L1 of the first filter bag 13 < the length L2 of the second filter bag 14 < the length L3 of the third filter bag 15.

[0043] Furthermore, the increasing diameter of the first filter bag 13, the second filter bag 14, and the third filter bag 15, combined with the increasing length difference, can construct an axial-radial-axial flow path, making the water flow efficiency higher and avoiding local blockage. In addition, the coaxial sealing of the upper ends of the first filter bag 13, the second filter bag 14, and the third filter bag 15 can form an axial fixed end, which, combined with the increasing diameter design, can form a natural support frame, effectively preventing the purification device 1 from collapsing and deforming, and improving the filtration stability of the device. Combined with the increasing length design, the impact force of the incoming water flow can be gradually reduced along the axial direction, improving the sealing reliability of the upper end of the device.

[0044] Furthermore, the first filter bag 13 has an inlet at the top and an outlet at the bottom, which is a flow-limiting hole 131. The diameter of the flow-limiting hole 131 is preferably 10mm to 20mm, which is beneficial for the collection of organic particles and will not cause blockage. The presence of the flow-limiting hole 131 ensures that the water in the first filter bag has a certain head advantage, which is beneficial for improving the filtration efficiency of the micropores on the bag wall. Furthermore, the outlet of the second filter bag 14 near the upper periphery of the inlet is a water distribution hole 141 for radially diverting the water source. Due to density, organic particles will accumulate in the gap between the second filter bag 14 and the first filter bag 13. Similarly, when the accumulation is too large, it will also flow into the third filter bag 15 through the outlet. In this application, the water distribution hole 141 is symmetrically distributed on the second filter bag 14, which can improve the laminar flow characteristics and automatically adjust the flow distribution of the multiple small holes on the water distribution hole 141 to avoid local overload.

[0045] Furthermore, the water outlet at the bottom of the third filter bag 15 is a slag discharge port 151, through which excess organic particles can be discharged, thus preventing clogging. Under this premise, the water passing through the micropores in the wall of the third filter bag 15 is the water required after treatment. Moreover, this application does not limit the specific structure of the slag discharge port 151; it can be a slag discharge port 151 with a built-in spiral guide vane, a slag discharge port 151 with an adjustable throttle valve inside, or a conventional opening, etc., and the structure of the slag discharge port 151 can be set according to actual needs.

[0046] Furthermore, at least one of the first filter bag 13, the second filter bag 14, and the third filter bag 15 is made of plastic fiber felt. The filter bags made of plastic fiber felt in this application have a plurality of micropores, which are on the micrometer scale. With this structure, when water enters the first filter bag 13, due to the large number of micropores in the filter bag itself, some water will flow through the micropores into the second filter bag 14, then through the micropores on the second filter bag 14 into the third filter bag 15, and then through the micropores on the third filter bag 15 into various filter barrels, boxes, pools, and other equipment connected to the outside of the purification device 1. During the process of passing through the micropores, particles larger than the micropore diameter are intercepted. With sufficient use of the purification device 1, a large number of microorganisms will adhere to the inside and outside of the first filter bag 13, the second filter bag 14, and the third filter bag 15, forming a biofilm layer, so that each filter bag not only has a filtration function but also a certain function of adsorbing particulate matter.

[0047] like Figure 2As shown, the purification device 1 further includes packing material 16. The packing material 16 can be a biochemical rope, brush, bio-ball, etc., which can either be fixed within the first filter bag 13 or be large enough not to protrude from the bottom flow-limiting hole 131 of the first filter bag 13. Similarly, packing material 16 can also be inserted into the gaps between the first filter bag 13 and the second filter bag 14, and between the second filter bag 14 and the third filter bag 15. Here, the function of the packing material 16 is to increase the surface area for biological attachment and improve biological treatment capacity. Furthermore, based on the above description, in the axial-radial flow path, the bottom flow-limiting hole 131 forces the water flow to form laminar flow, and the water distribution holes 141 are symmetrically distributed on the second filter bag 14, which can improve laminar flow characteristics. Therefore, this application controls the flow rate of the water source and utilizes fluid dynamics characteristics to maintain the flow-limiting hole 131 in a laminar flow state, thereby preventing the packing material 16 from clogging the flow-limiting hole 131.

[0048] like Figure 3 As shown, this utility model provides a recirculating aquaculture water purification system, which is equipped with at least one of the aforementioned purification devices 1. Further, the purification system of this application also includes a purification chamber 2, which can be a barrel, pool, or box, etc. At least one purification device 1 is installed inside the purification chamber 2; when there are multiple purification devices 1, they are installed at intervals inside the purification chamber 2. Even further, this application suspends the purification device 1 in the purification chamber 2 by an appropriate method, including but not limited to suspension with a support perforated plate, hoisting by an inlet pipe, buoyancy-adaptive suspension, and snap-on quick-release suspension.

[0049] Furthermore, this application provides one embodiment of the purification system, which also includes an inlet pipe 28 connected to an external aquaculture pond outlet pipe 21. Each purification device 1 is connected to the inlet pipe 28 via the first inlet 11 of the first filter bag 13. The connection between the first inlet 11 and the inlet pipe 28 includes, but is not limited to, parallel connection of multiple manifolds, ring water distribution system, four-way pipe network connection, modular quick-connect interface (using standardized interfaces such as clamps, flanges, etc. for quick connection), and adaptive pressure regulation connection.

[0050] Furthermore, such as Figure 3 As shown, the water purification system also includes an outlet pipe 21. The outlet pipe 21 is used to lead out wastewater from the water purification tank. The connection method between the outlet pipe 21 and the water purification tank includes threaded connection, quick-release clamp connection, flange connection, and modular combination connection. Any other connection method that can achieve the connection between the purification tank 2 and the outlet pipe 21 is within the protection scope of this application. The connection method of this application can be replaced by conventional selections in the field or special connection methods with special requirements such as corrosion in specific scenarios.

[0051] Furthermore, such as Figure 3As shown, the water purification system also includes a post-treatment system 5. The inlet of the post-treatment system 5 is connected to the outlet pipe 21. The post-treatment system 5 is used to perform advanced treatment on the water discharged from the water purification tank to meet the circulating water standard. The post-treatment system 5 of this application includes, but is not limited to, biological systems such as MBBR biological aeration, MBR membrane modules, and aerated biological filters; ozone contact tanks; activated carbon adsorption towers; ultraviolet disinfection channels; sodium hypochlorite dosing devices; and disinfection systems such as electrolyzers. Furthermore, any post-treatment system 5 that can be used for wastewater treatment in aquaculture water purification systems can be considered a conventional choice in this application.

[0052] Furthermore, this application also provides one implementation of a water purification system, such as... Figure 3 As shown, the purification system includes at least one agitator 3. When multiple purification devices 1 are provided in the purification system, multiple agitators 3 are respectively arranged between adjacent purification devices 1, with sufficient mixing space. The agitator 3 of this application is used to drive the water movement, thereby causing each purification device 1 to shake. The shaking is beneficial for the shedding of biofilm on the first filter bag 13, the second filter bag 14, and the third filter bag 15, and can also prevent the deposition of particulate matter in each filter bag, increasing its dispersion. The purification device 1 and the agitator 3 of this application operate simultaneously, or the agitator 3 operates intermittently. Furthermore, the agitator 3 of this application can be externally connected to a three-phase asynchronous motor + frequency converter combination to drive its operation and control its speed, and can also be connected to permanent magnet synchronous motors, DC motors, servo motors, etc.

[0053] Furthermore, this application also provides another implementation of the water purification system, in which a sewage return circulation pipe 26 and / or a sewage filtration sludge discharge pipe 22 are provided. One end of the sewage filtration sludge discharge pipe 22 passes through the water purification tank and connects to the sludge discharge port 151 of the third filter bag 15 of each purification device 1. This connection method includes threaded connection, quick-release clamp connection, flange connection, and modular combination connection, etc. Any other connection method that can achieve the connection between the sewage filtration sludge discharge pipe 22 and the sludge discharge port 151 is within the protection scope of this application. The connection method of this application can be replaced by conventional selections in the art or special connection methods with special requirements in specific scenarios, such as corrosion, high pressure, etc. Furthermore, this application recirculates all or part of the sewage from the sludge discharge port 151, which is similar to "activated sludge recirculation" in domestic sewage treatment. The sewage from the sludge discharge port 151 has extremely low dissolved oxygen. After mixing with the water from the aquaculture pond, it flows into the first filter bag 13, which can greatly reduce the dissolved oxygen in the water and has a great effect on the stability of the system. Excessive organic particles are filtered out, which can reduce the system's processing load. The specific method used in engineering depends on the actual amount of organic particles. Furthermore, based on the above description, impurities accumulated in the slag discharge port 151 can be naturally shaken off from the slag discharge port 151 by the agitator 3 and the fluctuations of the purification device 1. Alternatively, a self-cleaning screen can be installed in the slag discharge port 151, and a pulse backwashing system can be installed in the sewage filtration slag discharge pipe 22 to prevent impurities from clogging the slag discharge port 151 or the sewage filtration slag discharge pipe 22. Furthermore, the other end of the sewage filtration slag discharge pipe 22 is connected to the inlet of the filter 4. The filter 4 in this application is a physical filter used to remove solid impurities from the water, protect downstream equipment, and ensure water quality. The types of filter 4 in this application include, but are not limited to, screen filters, self-cleaning filters, and candle filters. This application does not limit the type of physical filter; any filter 4 that can be used for filtering slag in aquaculture water purification systems can be used in the purification system of this application.

[0054] Furthermore, the filter 4 of this application is connected to a drain pipe 27 on its side for discharging and recycling the filtered impurities; the bottom outlet of the filter 4 is connected to the outlet pipe 21, and the water filtered by the filter 4 and the water discharged from the purification box 2 are collected in the outlet pipe 21 and then enter the post-treatment system 5 for biochemical treatment and other post-treatment.

[0055] Furthermore, such as Figure 3As shown, this application can also add a sludge discharge tee 23 to the sewage filtration sludge discharge pipe 22. One end of the sludge discharge tee 23 is connected to a regulating valve 24 and a return pump 25, and the other end is connected to a filter 4, thereby realizing the return of a portion of the sewage from the sludge discharge port 151 and the filtration and sludge discharge of a portion of the sewage. Furthermore, the regulating valve 24 is connected to the inlet pipe of the sewage return circulation pipe 26, and the return pump 25 is installed on the sewage return circulation pipe 26. The outlet of the sewage return circulation pipe 26 is connected to the second inlet 12 on the first filter bag 13 of the purification device 1. The return pump 25 is used to pump the sewage back to the second inlet 12 of the first filter bag 13 to form a return flow. The regulating valve 24 can adjust the water volume to control the return flow ratio.

[0056] Furthermore, the purification principle of the purification system in this application is as follows:

[0057] The purification device 1 of this application is enriched with a large amount of particulate matter, which includes uneaten feed and feces. Under the action of microorganisms, these particles will quickly consume the oxygen in the water entering the filter bag, forming an anaerobic environment, thereby carrying out denitrification. In addition, the wastewater recirculation factor will accelerate the formation of an anaerobic environment.

[0058] Furthermore, the conventional nitration reaction is as follows:

[0059] NH4 + +1.5O2→NO2 - +H₂O+2H + ①

[0060] NO2 - +0.5O2→NO3 - ②

[0061] The conventional denitrification reaction is as follows:

[0062] NO3 - +2H + +2e - →NO2 - +H2O ③

[0063] 2NO2 - +8H + +6e - →N2↑+4H2O ④

[0064] However, in this application, due to the high efficiency of ammonia-oxidizing bacteria, the reaction in ① can be completed in the aquaculture pond and the first filter bag 13, while the generated NO2 -Under the action of denitrifying bacteria, salt completes the denitrification reaction ④. Compared with the conventional denitrification reaction, this application only involves ①+④, reducing reactions ② and ③, and proceeding with a short-cut nitrification reaction. Under this premise, the wastewater discharged from the purification tank 2 of this application can be further biochemically treated, oxygenated, pH adjusted, and disinfected before being recycled back to the aquaculture pond, forming a closed-loop water system. Although the purification system of this application also includes a post-treatment system 5, the volume of the purification system and the amount of packing material 16 are significantly reduced, and the overall investment is also significantly lower.

[0065] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A purification device, characterized in that, The filter includes a first filter bag (13), a second filter bag (14), and a third filter bag (15) nested together from the inside out, with water flow gaps between adjacent filter bags. The first filter bag (13), the second filter bag (14), and the third filter bag (15) are provided with water outlet holes. The water source entering the purification device forms an axial-radial-axial flow path in the water flow gap through the water outlet holes, so as to form an anaerobic environment to trigger a short-range nitrification reaction to remove nitrogen and filter the water source.

2. The purification device according to claim 1, characterized in that, The diameter and length of the first filter bag (13), the second filter bag (14) and the third filter bag (15) increase sequentially, and the upper ends of the first filter bag (13), the second filter bag (14) and the third filter bag (15) are coaxially sealed together.

3. The purification device according to claim 1 or 2, characterized in that, The first filter bag (13) has an inlet at the top and an outlet at the bottom, which is a flow-limiting hole (131).

4. The purification device according to claim 3, characterized in that, The outlet holes (141) on the upper periphery of the second filter bag (14) near the inlet are water distribution holes (141) for radial diversion of water source.

5. The purification device according to claim 1, 2 or 4, characterized in that, The outlet hole at the bottom of the third filter bag (15) is the slag discharge port (151).

6. The purification device according to claim 1, 2 or 4, characterized in that, At least one of the first filter bag (13), the second filter bag (14), and the third filter bag (15) is made of plastic fiber felt.

7. The purification device according to claim 1, 2 or 4, characterized in that, The purification device is equipped with packing material (16).

8. A recirculating aquaculture water purification system, characterized in that, The purification system is equipped with at least one purification device according to any one of claims 1 to 7.

9. The purification system according to claim 8, characterized in that, The purification system is equipped with at least one agitator (3).

10. The purification system according to claim 8 or 9, characterized in that, The purification system is equipped with a sewage return circulation pipe (26) and / or a sewage filtration and sludge discharge pipe (22).

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