Prawn marking method and in-situ biological barrel for in-situ treatment of early-stage clear water marked seedlings

Abstract

The present application relates to the field of aquaculture technology, and discloses a method for marking prawn seedlings in early-stage clear water and in-situ treatment in later stage and an in-situ biological barrel, the method comprising water body preparation of a marking pond and ex-situ biofilm maturation of the in-situ biological barrel; prawn larvae are put into the pond in early stage, and granular feed is used for feeding, water is changed and sewage is discharged to mark seedlings in clear water; after reaching a set time, the matured in-situ biological barrel is fixed in the marking pond, a nanometer microporous aeration disc at the bottom of the barrel is opened to establish gas stripping negative pressure microcirculation, and pond water is sucked into the barrel and purified by hydrophilic modified porous polyurethane biological filler; at the same time, an auxiliary microporous backwashing air pipe outside the water inlet window is opened to establish a bubble screen sweeping barrier, prevent the anti-escape net frame from being blocked, and reduce the water change rate for in-situ treatment in later stage. In the present application, water quality is maintained by water change and sewage discharge in early stage, ammonia nitrogen is rapidly degraded by introducing a matured biological barrel in later stage, the net hole is kept unobstructed by using bubble flushing, the water environment in the seedling marking period is stabilized, the stress of larvae is reduced, and then the seedling emergence rate is improved.

Description

Technical Field

[0001] This invention relates to the field of aquaculture technology, specifically to a method for early-stage clear water seedling raising and later-stage in-situ treatment of shrimp seedlings, and an in-situ biological tank. Background Technology

[0002] The shrimp larvae rearing stage is a crucial step in aquaculture. As the rearing stage progresses, the shrimp larvae gradually increase in size, leading to an increase in the amount of microparticle feed and larval excrement. This change causes a rapid accumulation of harmful substances such as ammonia nitrogen and nitrite in the rearing pond water, significantly increasing the risk of water quality deterioration.

[0003] To control the concentration of harmful substances in water, traditional production methods typically involve frequent and large-scale water exchanges. However, frequent water exchanges not only increase water consumption and water management costs, but the environmental fluctuations caused by the replacement of old and new water bodies can easily lead to stress responses in shrimp larvae, thus affecting hatching rates. To overcome the drawbacks of large-scale water exchanges, introducing in-situ biological filtration systems within the nursery ponds has become a technological direction. However, the nursery period for shrimp is relatively short. If blank biological packing material is placed directly in the nursery pond for natural biofilm formation, the cultivation period for nitrifying bacteria is long, often unable to respond promptly to sudden water quality deterioration in the later stages. Furthermore, cultivating biofilm in the early stages of pond construction leads to a large proliferation of microorganisms that compete with the vulnerable shrimp larvae for dissolved oxygen, increasing the difficulty of early management.

[0004] When setting up in-situ water treatment equipment in the nursery pond, escape-proof isolation nets are usually installed around the equipment to prevent shrimp larvae from being sucked in. Because the water in the mid-to-late stages of aquaculture is rich in fine suspended organic matter, uneaten feed and fecal debris, as well as a large proliferation of sticky bacteria, these substances easily adhere to and gradually clog the isolation net holes under the suction of the water flow. Once the net holes are clogged, water exchange between the inside and outside of the equipment is interrupted, and the internal biological treatment system will fail due to lack of oxygen and substrate. This necessitates frequent manual cleaning of the nets by aquaculture workers, increasing the workload of daily maintenance.

[0005] Furthermore, conventional polyurethane biofillers, a core component of biological treatment systems, possess hydrophobic molecular structures. This hydrophobicity results in a large water contact angle on the filler surface, increasing resistance to water flow penetrating the internal pores and severely hindering microbial attachment and colonization on the filler surface. Conventional fillers exhibit slow biofilm formation and low biofilm adhesion, making it difficult to generate sufficient water treatment load within limited seedling space, thus limiting the practical application effectiveness of in-situ purification systems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for early-stage clear water seedling cultivation and later-stage in-situ treatment of shrimp seedlings, as well as an in-situ biological tank. This solves the problems of rapid water quality deterioration in the middle and later stages of shrimp seedling cultivation, which requires frequent water changes and causes stress to larvae. Traditional in-situ biological filtration systems suffer from slow biofilm formation in the early stage, competition for dissolved oxygen with larvae, easy clogging of the isolation net by organic matter and bacteria in the later stage leading to interruption of purified water flow, and poor hydrophilicity of conventional biological packing materials, which makes it difficult for microorganisms to attach.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for shrimp seedlings undergoing initial water purification and subsequent in-situ treatment, comprising the following steps:

[0008] Prepare the water body for the seedling tank to obtain the prepared seedling tank. At the same time, perform off-site biofilm maturation of the hydrophilic modified porous polyurethane biological packing material in the in-situ biological tank in a separate pretreatment tank to obtain the matured in-situ biological tank.

[0009] Based on the prepared seedling pond, a compound probiotic preparation and live Brachiopoda foldis were inoculated into the seedling pond, and Litopenaeus vannamei nauplius were released.

[0010] The nauplius vannamei larvae were fed with microparticle pellet feed, and the water was changed and sewage was drained daily to carry out the initial water clearing and seedling raising process.

[0011] After the initial clear water seedlings have reached the set time, the matured in-situ biological tank is semi-submerged and fixed in the seedling pond, and isolated using an escape-proof net frame. The nano-microporous aeration disc at the bottom of the in-situ biological tank is opened to establish an air-lift negative pressure microcirculation. At the same time, the auxiliary microporous backwashing air pipe outside the water inlet window is opened to establish an air bubble sweeping barrier. Meanwhile, the daily water exchange rate is reduced for subsequent in-situ treatment.

[0012] Based on the nursery pond where the post-treatment is carried out, when the Litopenaeus vannamei nauplius grows to the set size, the escape-proof net frame of the in-situ biological tank is replaced, and the nursery continues until the larvae are hatched and the transfer to another pond is completed.

[0013] By adopting the above technical solution, the initial clear water seedling stage and the subsequent in-situ treatment form a phased coordination. At the beginning of the seedling stage, the overall discharge load of the system is not large. At this time, simply changing the water and discharging wastewater is sufficient to maintain the aquatic environment. This is not only convenient and easy to manage, but also avoids the problem of competition for dissolved oxygen between the new biological treatment system and the larvae in the early stages. As the aquaculture progresses into the later stages, the risk of water quality deterioration increases. At this point, the in-situ biological tank, which has already been pre-treated and fully matured in the adjacent pretreatment tank, can be moved in. Because the packing material is already covered with mature nitrifying bacteria, the in-situ biological tank can quickly exert its biochemical degradation effect after being placed in the water, degrading ammonia nitrogen and nitrite in the water, overcoming the shortcomings of traditional in-situ biofilm cultivation, such as long start-up cycles and delayed response. Simultaneously, by opening the aeration disc at the bottom of the tank, the upward airflow will pull the surrounding water upwards. Utilizing the principle of airlift, an upward water flow is generated inside the tank, creating negative pressure at the inlet window, continuously drawing water from the outside pond into the tank to pass through the biological packing material, achieving continuous water purification. Meanwhile, the auxiliary microporous backwashing air pipes on the outer side also play a crucial role. They continuously release air bubbles, which, following the surface of the escape-proof net, flush upwards, effectively removing organic debris and bacteria that can clog the mesh, ensuring a consistently unobstructed water inlet. Therefore, this achieves stable water quality during the shrimp larval stage, reduces the workload of later water changes, and thus alleviates stress on the larvae, thereby improving the overall hatching rate.

[0014] Preferably, the specific operation process for preparing the seedling pond water is as follows: inject sand-filtered seawater into the seedling pond, sprinkle potassium persulfate compound salt for disinfection, then sprinkle sodium thiosulfate to eliminate oxidizing residues, and add sodium bicarbonate to adjust the total alkalinity of the water to 120-150 mg / L.

[0015] By adopting the above technical solutions, disinfection and residue removal are carried out alternately, providing a safe initial aquatic environment for the seedlings. Supplementing with sodium bicarbonate is mainly to increase the total alkalinity, enhance the water's own acid-base buffering capacity, and incidentally, provide sufficient inorganic carbon source for the nitrifying bacteria that will be active later.

[0016] Preferably, the specific process for ex-situ biofilm maturation is as follows: the in-situ biological tank is placed in an independent pretreatment tank, ammonium chloride is added to the pretreatment tank to make the ammonia nitrogen concentration reach 3.0-5.0 mg / L, and nitrifying bacteria in the form of pure freeze-dried live bacterial powder is added at 1.0-2.0 g / m³. 3 Turn on the nanoporous aeration disc at the bottom of the in-situ biological tank and control the aeration intensity to 8-10 m³ / h. 3 / h·m 2 It runs continuously for 10 to 15 days to complete the ectopic biofilm maturation.

[0017] By adopting the above technical solution, an appropriate amount of ammonium chloride is artificially added as food, and with the aeration disc providing ample oxygen, nitrifying bacteria can quickly take root and reproduce on the surface of the packing material without being disturbed by shrimp, thus shortening the originally long film attachment period.

[0018] Preferably, the specific procedure for daily water exchange and wastewater discharge is as follows: Starting from the 3rd day after stocking, open the bottom drain pipe daily to remove bottom waste and replace it with fresh water of equal salinity. The daily water exchange volume should account for 20% to 30% of the total pond water volume. Every 3 to 5 days, supplement the water with a compound probiotic preparation at a rate of 0.5 to 1.0 g / m³. 3 .

[0019] By adopting the above technical solutions, in the early stages of breeding, while the seedlings are still small, the feces and residue can be removed by changing the water appropriately, and probiotics can be added regularly to suppress the growth of miscellaneous bacteria. This is very practical for stabilizing the basic water quality in the early stages.

[0020] Preferably, the preparation method of hydrophilic modified porous polyurethane biofiller includes the following steps:

[0021] Polypropylene glycol was dehydrated at 100–110 °C and under a vacuum of -0.09 MPa. After cooling, 4,4'-diphenylmethane diisocyanate was added, and the mixture was stirred and reacted under nitrogen protection to obtain an isocyanate-terminated polyurethane prepolymer.

[0022] The foaming raw materials are mixed evenly to prepare an aqueous foaming liquid; the foaming raw materials include N-methyldiethanolamine, 1,1,1-trimethylolpropane, deionized water, stannous octoate, triethylenediamine and polysiloxane-polyether copolymer.

[0023] At room temperature, the aqueous foaming liquid is added to the polyurethane prepolymer and mixed at high speed. Then, it is poured into a mold to obtain a foaming system. After the foaming system has finished expanding and lost its fluidity, it is placed in an oven to mature. Finally, it is cut into pieces to obtain the hydrophilic modified porous polyurethane biofiller.

[0024] By employing the above technical solution, hydrophilic modified porous polyurethane biofiller is prepared under specific chemical reactions. Specifically, the construction of the polyurethane skeleton relies heavily on the terminal hydroxyl groups provided by polypropylene glycol. Under nitrogen protection and heating, these terminal hydroxyl groups undergo an addition reaction with the isocyanate groups in 4,4'-diphenylmethane diisocyanate. By allowing a slight excess of isocyanate, an isocyanate-terminated polyurethane prepolymer can be obtained. Once the prepolymer is synthesized, foaming and crosslinking follow. When deionized water in the aqueous solution encounters the isocyanate groups at the ends of the prepolymer, it immediately generates an unstable carbamic acid, which quickly decomposes to release carbon dioxide gas, creating numerous pores within the material. During this process, the newly generated free amino groups continue to react with the remaining isocyanate groups to form urea bonds, elongating and intertwining the molecular chains. So where does the crucial hydrophilicity come from? This is thanks to N-methyldiethanolamine, a chain extender. During the chain extension reaction, it incidentally inserts polar tertiary amine groups into the main chain, directly altering the hydrophobic nature of the polyurethane. Furthermore, the addition of 1,1,1-trimethylolpropane provides crosslinking points to make the network structure more robust, and the polysiloxane-polyether copolymer nearby regulates the surface tension of the bubbles. The final product becomes a three-dimensional sponge-like structure with fully open pores. The material itself is hydrophilic, with numerous and permeable pores, allowing water to flow in without obstruction, effectively improving the rate of microbial penetration and colonization into the pores of the filler.

[0025] Preferably, the set time is 7 to 10 days after stocking; when the auxiliary microporous backwashing air pipe outside the water inlet window is opened, the air supply pressure is controlled at 0.02 to 0.05 MPa; the daily water exchange rate is controlled at 5% to 10%; and the Litopenaeus vannamei nauplius grows to a set size of PL15 or higher.

[0026] By adopting the above technical solutions and by clearly defining key parameters such as process switching nodes, gas supply pressure, and water exchange rate, it is ensured that the operation rhythm of the entire system can match the growth rhythm of shrimp larvae.

[0027] The second aspect of this invention provides an in-situ biological tank for early-stage clear water seedling cultivation and later-stage in-situ treatment, comprising a tank body, an inlet window on the side wall of the tank body, a support plate inside the tank body, and a hydrophilic modified porous polyurethane biological filler filling inside the tank body, the hydrophilic modified porous polyurethane biological filler being located on top of the support plate. Rails are fixedly connected to both the inner and outer sides of the tank body, and an escape-prevention net frame is engaged in the middle of the rails. A nanoporous aeration disc is provided inside the tank body to establish a negative pressure microcirculation within the tank body. An auxiliary microporous backwashing air pipe is provided at the air inlet end of the nanoporous aeration disc, and the other end of the auxiliary microporous backwashing air pipe is located outside the inlet window to establish an air bubble sweeping barrier outside the escape-prevention net frame.

[0028] By adopting the above technical solution, a water inlet window is opened on the tank body, and a support plate is placed inside filled with modified packing material. When the microporous aeration disc at the bottom pumps air upwards, water and air mix and surge upwards. This air-lift effect creates a stable negative pressure suction zone at the water inlet window, drawing external pool water into the tank and forcing it through the packing layer, thus completing water contact purification. Meanwhile, the auxiliary backwashing air pipe located outside the window emits air bubbles that form a sweeping barrier, continuously rinsing the outer edge of the escape-prevention net. Therefore, the effect of continuously purifying water while simultaneously intercepting and flushing away debris is achieved in the seedling tank.

[0029] Preferably, the anti-escape mesh frames that are engaged in the locking rails on the inner and outer sides of the barrel have different mesh counts, which are used to seamlessly replace the anti-escape mesh frames with mesh frames of different counts.

[0030] By adopting the above technical solution, the size of the mesh frame can be determined based on the size of the seedlings. A suitable mesh size prevents seedlings from accidentally entering the container while minimizing obstruction of water flow. The easy-to-replace mesh also makes replacement more convenient.

[0031] Preferably, the volume of the hydrophilic modified porous polyurethane biofiller accounts for 30% to 70% of the total internal volume of the barrel.

[0032] By adopting the above technical solution, overfilling the packing material will clog the water flow, while underfilling it will not provide much water purification. By controlling the volume ratio within this range, there are sufficient water flow channels in the tank, ensuring that the air-lift circulation system will not stagnate or fail due to excessive water flow resistance.

[0033] This invention provides a method for early-stage clear water seedling cultivation and later-stage in-situ treatment of shrimp seedlings, as well as an in-situ biological tank. It has the following beneficial effects:

[0034] 1. This invention employs a process combining early-stage water exchange and wastewater discharge with later-stage in-situ biological treatment. During the early stages of seedling cultivation, when the system's discharge load is low, conventional water exchange maintains the aquatic environment, avoiding competition for dissolved oxygen between the newly constructed biological treatment system and the shrimp larvae. Later, when the risk of water quality deterioration increases, in-situ biological tanks, pre-treated in a separate pond for anaerobic biofilm maturation, are transferred into the seedling pond. Because the packing material contains mature nitrifying bacteria communities, it can immediately degrade ammonia nitrogen and nitrite in the seedling pond water after transfer, avoiding the time-consuming drawbacks of conventional in-situ biofilm formation. This also reduces the need for large-scale water exchanges later on, minimizing stress on the larvae caused by water quality fluctuations.

[0035] 2. The in-situ biological tank designed in this invention generates upward airflow through the nanoporous aeration disc at the bottom. Utilizing the principle of air lift, a negative pressure is formed at the water inlet window, continuously drawing external pool water into the tank and through the biological packing layer to achieve in-situ water purification. To solve the problem of easy clogging of the isolation net, an auxiliary microporous backwashing air pipe is added to the outside of the water inlet window. The rising air bubbles released by the pipe continuously physically flush the outer side of the escape-proof net frame, preventing organic suspended matter and proliferating microorganisms from adhering to and clogging the mesh. This ensures the long-term unobstructed flow of the water inlet channel without frequent manual intervention.

[0036] 3. This invention prepares hydrophilic modified porous polyurethane biological packing material through a specific chemical reaction. During the foaming and crosslinking stage of the polyurethane prepolymer, N-methyldiethanolamine is introduced as a functional chain extender, embedding the polar tertiary amine groups in its structure into the main chain of the polyurethane macromolecule. This changes the basic hydrophobic properties of the polyurethane material. Combined with the high porosity three-dimensional network structure formed by the foaming process, external water flow can easily penetrate the interior of the packing material, increasing the effective specific surface area of ​​the packing material and improving the attachment rate and colonization of microorganisms in the pores inside the packing material, thereby increasing the upper limit of water treatment load of the in-situ biological tank. Attached Figure Description

[0037] Figure 1 This is a comparison chart of the natural settling time and saturated water absorption ratio of each group of biological packing materials in this invention;

[0038] Figure 2 This is a comparison chart of the biochemical denitrification kinetic parameters of various groups of biological packing materials in this invention;

[0039] Figure 3 The following are test diagrams of the hydraulic characteristics and filter anti-clogging performance of the in-situ biological tank of the present invention. Among them, (a) is a comparison diagram of the inlet water suction flow rate of each group of in-situ biological tanks, and (b) is a dynamic evolution curve of the running time of each group of in-situ biological tanks and the difference in water head level inside and outside the filter screen.

[0040] Figure 4 The following are the test results of the core physicochemical indicators and transparency of the water quality of each seedling system of the present invention. Among them, (a) is a comparison of the average turbidity of each seedling system before and after the period, and (b) is a comparison of the maximum ammonia nitrogen peak and the maximum nitrite peak of each seedling system.

[0041] Figure 5 The following are statistical test charts of production efficiency and equipment operation and maintenance of each seedling system of the present invention, wherein (a) is a comparison chart of the final seedling survival rate of each seedling system, and (b) is a comparison chart of the average fault-free operation cycle and the total number of passive cleanings of the water treatment equipment of each seedling system.

[0042] Figure 6 This is a three-dimensional view of the in-situ biological tank of the present invention;

[0043] Figure 7 This is a schematic diagram of the cross-sectional structure of the barrel body of the present invention;

[0044] Figure 8 This is a top view of the barrel structure of the present invention.

[0045] Figure 9 This is a structural diagram of the nanoporous aeration disc of the present invention.

[0046] The components include: 1. Tank body; 2. Rail; 3. Escape-proof mesh frame; 4. Auxiliary microporous backwashing air pipe; 5. Hydrophilic modified porous polyurethane biological packing; 6. Nanoporous aeration disc; 7. Support plate; 8. Water inlet window. Detailed Implementation

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, examples, comparative examples, and test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Preparation Examples 1-3:

[0049] Preparation Example 1:

[0050] This preparation example provides a method for preparing hydrophilic modified porous polyurethane biofiller 5, including the following steps:

[0051] 100 parts by weight of polypropylene glycol were dehydrated at 105°C and under a vacuum of -0.09 MPa for 1.5 hours, then cooled to 75°C, and 90 parts by weight of 4,4'-diphenylmethane diisocyanate were added. The mixture was stirred at 250 rpm for 2.5 hours under nitrogen protection to obtain an isocyanate-terminated polyurethane prepolymer.

[0052] 10 parts by weight of N-methyldiethanolamine, 2 parts by weight of 1,1,1-trimethylolpropane, 3.5 parts by weight of deionized water, 0.15 parts by weight of stannous octoate, 0.15 parts by weight of triethylenediamine and 1.5 parts by weight of polysiloxane-polyether copolymer are mixed evenly to prepare an aqueous foaming liquid.

[0053] At room temperature, the aqueous foaming liquid is added to the above polyurethane prepolymer and mixed at high speed at 2500 rpm for 8 seconds. Then it is quickly poured into a mold to obtain the foaming system.

[0054] After the foaming system has finished expanding and lost its fluidity, it is placed in a 70℃ oven for 18 hours to mature. Finally, it is cut into cubic pieces with a side length of 2.0 cm to obtain hydrophilic modified porous polyurethane biofiller 5.

[0055] Preparation Example 2:

[0056] This preparation example provides a method for preparing hydrophilic modified porous polyurethane biofiller 5, including the following steps:

[0057] 100 parts by weight of polypropylene glycol were dehydrated at 100°C and under vacuum of -0.09 MPa for 1 hour, then cooled to 70°C, and 60 parts by weight of 4,4'-diphenylmethane diisocyanate were added. The mixture was stirred at 200 rpm for 2 hours under nitrogen protection to obtain isocyanate-terminated polyurethane prepolymer.

[0058] Five parts by weight of N-methyldiethanolamine, one part by weight of 1,1,1-trimethylolpropane, two parts by weight of deionized water, 0.05 parts by weight of stannous octoate, 0.05 parts by weight of triethylenediamine and one part by weight of polysiloxane-polyether copolymer were mixed evenly to prepare an aqueous foaming liquid.

[0059] At room temperature, the aqueous foaming liquid is added to the above polyurethane prepolymer and mixed at high speed at 2000 rpm for 5 seconds. Then it is quickly poured into a mold to obtain the foaming system.

[0060] After the foaming system has finished expanding and lost its fluidity, it is placed in a 60℃ oven for 12 hours to mature. Finally, it is cut into cubic pieces with a side length of 1.0 cm to obtain hydrophilic modified porous polyurethane biofiller 5.

[0061] Preparation Example 3:

[0062] This preparation example provides a method for preparing hydrophilic modified porous polyurethane biofiller 5, including the following steps:

[0063] 100 parts by weight of polypropylene glycol were dehydrated at 110°C and under vacuum of -0.09 MPa for 2 hours, then cooled to 80°C, and 120 parts by weight of 4,4'-diphenylmethane diisocyanate were added. The mixture was stirred at 300 rpm for 3 hours under nitrogen protection to obtain isocyanate-terminated polyurethane prepolymer.

[0064] 15 parts by weight of N-methyldiethanolamine, 3 parts by weight of 1,1,1-trimethylolpropane, 5.0 parts by weight of deionized water, 0.25 parts by weight of stannous octoate, 0.25 parts by weight of triethylenediamine and 2.0 parts by weight of polysiloxane-polyether copolymer were mixed evenly to prepare an aqueous foaming liquid.

[0065] At room temperature, the aqueous foaming liquid is added to the above polyurethane prepolymer and mixed at high speed of 3000 rpm for 10 seconds. Then it is quickly poured into a mold to obtain the foaming system.

[0066] After the foaming system has finished expanding and lost its fluidity, it is placed in an 80℃ oven for 24 hours to mature. Finally, it is cut into cubic pieces with a side length of 3.0 cm to obtain hydrophilic modified porous polyurethane biofiller 5.

[0067] Examples 1-3

[0068] Example 1:

[0069] This embodiment provides a method for shrimp seedlings undergoing initial clear water frying followed by in-situ treatment, including the following steps:

[0070] Eight days before stocking, sand-filtered seawater with a salinity of 20 ppt was injected into the seedling pond, and potassium persulfate compound salt with a concentration of 2.0 mg / L was sprayed for disinfection for 36 hours. Then, sodium thiosulfate with a concentration of 2.5 mg / L was sprayed to eliminate oxidative residues, and sodium bicarbonate was added to adjust the total alkalinity of the water to 135 mg / L.

[0071] The in-situ biological tank was placed in a separate pretreatment tank. The tank was filled with the hydrophilic modified porous polyurethane biological packing material 5 obtained in Preparation Example 1, supported by a support plate inside the tank body 1. The packing material volume occupied 50% of the total internal volume of the tank body 1. The water temperature in the pretreatment tank was controlled at 30℃. Ammonium chloride was added to the tank to achieve an ammonia nitrogen concentration of 4.0 mg / L, and 1.5 g / m³ of pure freeze-dried live bacterial powder nitrifying bacteria was added simultaneously. 3 Turn on the nanoporous aeration disc 6 at the bottom of the in-situ biological tank and control the aeration intensity to 9m. 3 / h·m 2 The ex-situ biofilm maturation is completed after 12 days of continuous operation. The ex-situ biofilm maturation step is started in advance in an independent pretreatment tank. The start time is based on ensuring that the in-situ biological tank has completed 12 days of maturation before being introduced into the seedling pond on the 8th day after the seedlings are released.

[0072] The seedlings were inoculated with a compound probiotic preparation and live Brachiopoda foldis at a density of 8 filaments / mL.

[0073] After confirming the lack of toxicity through trial stocking, Litopenaeus vannamei nauplius were released at a stocking density of 1600 shrimp / m². 3 Do not place the original bio-bucket during this stage;

[0074] Microparticle pellet feed was used for feeding. On the first day, the feeding amount was 1.5g per 100,000 fry, divided into 8 meals per day. The feeding amount was then increased by 25% every 2 days thereafter.

[0075] Starting from the third day after stocking, the bottom drain pipe is opened daily to remove waste and replace it with fresh water of the same salinity. The daily water replacement volume is 25% of the total pond volume. Every four days, 0.8g / m³ of compound probiotic preparation is added to the water. 3 ;

[0076] On the 8th day after stocking, the in-situ biological tank, which has completed its ex-situ maturation, is semi-submersible and fixed in the seedling pond. The escape-proof net frame 3 uses a 200μm mesh frame. The nano-microporous aeration disc 6 at the bottom of the tank is turned on, and the aeration intensity is adjusted to 9m. 3 / h·m 2 At the same time, the auxiliary microporous backwashing air pipe 4 on the outside of the water inlet window 8 is opened, and the air supply pressure is controlled at 0.035MPa to establish air lifting negative pressure microcirculation and bubble sweeping barrier.

[0077] After the in-situ biological tank is introduced, the large-scale water exchange in the early stage is stopped, and the daily water exchange rate is controlled at 8% for subsequent in-situ treatment.

[0078] When the shrimp grow to PL15 or above, the escape-proof net frame 3 is seamlessly replaced from a 200μm mesh frame to a low-mesh 400μm mesh frame by using the rails 2 on both the inner and outer sides of the barrel 1.

[0079] Continue seedling raising until 30 days after stocking, when seedlings emerge and are transferred to ponds.

[0080] Example 2:

[0081] This embodiment provides a method for shrimp seedlings undergoing initial clear water frying followed by in-situ treatment, including the following steps:

[0082] Seven days before stocking, sand-filtered seawater with a salinity of 15 ppt was injected into the seedling pond, and potassium persulfate compound salt with a concentration of 1.5 mg / L was sprayed for disinfection for 24 hours. Then, sodium thiosulfate with a concentration of 2.0 mg / L was sprayed to eliminate oxidative residues, and sodium bicarbonate was added to adjust the total alkalinity of the water to 120 mg / L.

[0083] The in-situ biological tank was placed in a separate pretreatment tank. The tank was filled with the hydrophilic modified porous polyurethane biological packing material 5 obtained in Preparation Example 2, supported by a support plate inside the tank body 1. The packing material volume occupied 30% of the total internal volume of the tank body 1. The water temperature in the pretreatment tank was controlled at 28℃. Ammonium chloride was added to the tank to achieve an ammonia nitrogen concentration of 3.0 mg / L, and 1.0 g / m³ of pure freeze-dried live bacterial powder nitrifying bacteria was added simultaneously. 3 Turn on the nanoporous aeration disc 6 at the bottom of the in-situ biological tank and control the aeration intensity to 8m. 3 / h·m 2 The in-situ biofilm maturation is completed after 10 days of continuous operation. The in-situ biofilm maturation step is started in advance in an independent pretreatment tank. The start time is to ensure that the in-situ biological tank has completed 10 days of maturation before being introduced into the seedling pond on the 7th day after the seedlings are released.

[0084] The seedlings were inoculated with a compound probiotic preparation and live Brachiopoda foldis at a density of 5 filaments / mL.

[0085] After confirming the lack of toxicity through trial stocking, Litopenaeus vannamei nauplius were released at a stocking density of 1600 shrimp / m². 3 Do not place the original bio-bucket during this stage;

[0086] Microparticle pellet feed was used for feeding. On the first day, the feeding amount was 1.0g per 100,000 fry, divided into 6 meals per day. The feeding amount was then increased by 20% every 2 days thereafter.

[0087] Starting from the third day after stocking, open the drain pipe at the bottom of the pond daily to remove waste and replace it with fresh water of the same salinity. The daily water replacement volume should be 20% of the total pond volume. Also, supplement the water with a compound probiotic preparation at a rate of 0.5g / m³ every three days. 3 ;

[0088] On the 7th day after stocking, the in-situ biological tank, which has completed its ex-situ maturation, is semi-submersible and fixed in the seedling pond. The escape-proof net frame 3 uses a 180μm mesh frame. The nano-microporous aeration disc 6 at the bottom of the tank is turned on, and the aeration intensity is adjusted to 3m. 3 / h·m 2 At the same time, the auxiliary microporous backwashing air pipe 4 on the outside of the water inlet window 8 is opened, and the air supply pressure is controlled at 0.02MPa to establish air lifting negative pressure microcirculation and bubble sweeping barrier.

[0089] After the in-situ biological tank is introduced, the large-scale water exchange in the early stage is stopped, and the daily water exchange rate is controlled at 5% for subsequent in-situ treatment.

[0090] When the shrimp grow to PL15 or above, the escape-proof net frame 3 is seamlessly replaced from a 180μm mesh frame to a low-mesh 380μm mesh frame by using the rails 2 on both the inner and outer sides of the barrel 1.

[0091] Continue seedling raising until 30 days after stocking, when seedlings emerge and are transferred to ponds.

[0092] Example 3:

[0093] This embodiment provides a method for shrimp seedlings undergoing initial clear water frying followed by in-situ treatment, including the following steps:

[0094] Ten days before stocking, sand-filtered seawater with a salinity of 30 ppt was injected into the seedling pond, and potassium persulfate compound salt with a concentration of 2.5 mg / L was sprayed for disinfection for 48 hours. Then, sodium thiosulfate with a concentration of 3.0 mg / L was sprayed to eliminate oxidative residues, and sodium bicarbonate was added to adjust the total alkalinity of the water to 150 mg / L.

[0095] The in-situ biological tank was placed in a separate pretreatment tank. The tank was filled with the hydrophilic modified porous polyurethane biological packing material 5 obtained in Preparation Example 3, supported by a support plate inside the tank body 1. The packing material volume occupied 70% of the total internal volume of the tank body 1. The water temperature in the pretreatment tank was controlled at 32℃. Ammonium chloride was added to the tank to achieve an ammonia nitrogen concentration of 5.0 mg / L, and 2.0 g / m³ of pure freeze-dried live bacterial powder nitrifying bacteria was added simultaneously. 3 Turn on the nanoporous aeration disc 6 at the bottom of the in-situ biological tank and control the aeration intensity to 10m. 3 / h·m 2 The process involves continuous operation for 15 days to complete the ex-situ biofilm maturation. The ex-situ biofilm maturation step is started in advance in an independent pretreatment tank. The start time is based on ensuring that the in-situ biological tank has completed 15 days of maturation before being introduced into the seedling pond on the 10th day after the seedlings are released.

[0096] The seedlings were inoculated with a compound probiotic preparation and live Brachiopoda foldis at a density of 10 cells / mL.

[0097] After confirming the lack of toxicity through trial stocking, Litopenaeus vannamei nauplius were released at a stocking density of 1600 shrimp / m². 3 Do not place the original bio-bucket during this stage;

[0098] Microparticle pellet feed was used for feeding. On the first day, the feeding amount was 2.0g per 100,000 fry, divided into 8 meals per day. The feeding amount was then increased by 30% every 2 days thereafter.

[0099] Starting from the third day after stocking, the bottom drain pipe is opened daily to remove waste and replace it with fresh water of the same salinity. The daily water replacement volume is 30% of the total pond volume. A compound probiotic preparation of 1.0g / m³ is added to the water every 5 days. 3 ;

[0100] On the 10th day after stocking, the in-situ biological tank, which has completed its ex-situ maturation, is semi-submersible and fixed in the seedling pond. The escape-proof net frame 3 uses a 250μm mesh frame. The nanoporous aeration disc 6 at the bottom of the tank is turned on, and the aeration intensity is adjusted to 15m. 3 / h·m 2 At the same time, the auxiliary microporous backwashing air pipe 4 on the outside of the water inlet window 8 is opened, and the air supply pressure is controlled at 0.05MPa to establish air lifting negative pressure microcirculation and bubble sweeping barrier.

[0101] After the in-situ biological tank is introduced, the large-scale water exchange in the early stage is stopped, and the daily water exchange rate is controlled at 10% for subsequent in-situ treatment.

[0102] When the shrimp grow to PL15 or above, the escape-proof net frame 3 is seamlessly replaced from a 250μm mesh frame to a low-mesh 450μm mesh frame by using the rails 2 on both the inner and outer sides of the barrel 1.

[0103] Continue seedling raising until 30 days after stocking, when seedlings emerge and are transferred to ponds.

[0104] Comparative Examples 1-5:

[0105] Comparative Example 1:

[0106] Compared with Example 1, the difference is that instead of using a large water change and in-situ biological tank treatment in the early stage, no water change is used throughout the process, and carbon source (molasses) is continuously added to the pond for traditional biofloc seedling cultivation. All other aspects are the same.

[0107] Comparative Example 2:

[0108] Compared with Example 1, the difference is that the in-situ biological tank does not use the air lift negative pressure microcirculation formed by the bottom nanoporous aeration disc 6 as the water circulation power, but instead uses an external high-power mechanical centrifugal water pump to force water circulation; in order to avoid the oxygen supply difference from interfering with the test results, the aeration and oxygen supply conditions inside the tank are maintained at the same level as in Example 1, and everything else is the same.

[0109] Comparative Example 3:

[0110] Compared with Example 1, the difference is that the auxiliary microporous backwashing air pipe 4 on the outside of the escape prevention net frame 3 is removed (i.e., there is no auxiliary microporous backwashing air pipe 4), and the rest are the same.

[0111] Comparative Example 4:

[0112] Compared with Example 1, the difference is that the in-situ biological tank did not undergo the previous ex-situ pre-film maturation, but the biological tank filled with new filler was directly placed into the seedling pond on the 8th day after the seedlings were released. All other aspects are the same.

[0113] Comparative Example 5:

[0114] Compared with Example 1, the difference is that the in-situ biological tank is filled with commercially available unmodified polyethylene (PE) biological packing material instead of the hydrophilic modified porous polyurethane biological packing material 5 obtained in Preparation Example 1. All other aspects are the same.

[0115] Test Examples 1-4:

[0116] Test Example 1:

[0117] This test example mainly verifies the macroscopic physicochemical properties and biochemical denitrification mechanism of the hydrophilic modified porous polyurethane biological packing material 5. The experimental objects are the modified porous polyurethane biological packing materials prepared in Preparation Example 1, Preparation Example 2, and Preparation Example 3, as well as the commercially available unmodified polyethylene (PE) biological packing material used in Comparative Example 5.

[0118] Each group of filler samples was cut into standard cubic test blocks with a side length of 1.0 cm and placed in a 60℃ forced-air drying oven for constant weight treatment. The test blocks were released from a standard beaker containing 500 ml of deionized water at a height of 2 cm from the water surface, and the natural settling time of the test blocks from contact with the water surface to complete submersion was recorded. Ten samples from the same group were taken and the average value was calculated.

[0119] The initial mass of the dried, constant-weight test block was recorded, and then it was completely immersed in deionized water at 25°C for 24 hours. After immersion, the test block was removed, suspended for 30 seconds to allow free water to drip from its surface, and then weighed again. The saturated water absorption ratio of each group of fillers was obtained by calculating the ratio of the mass difference before and after immersion to the initial mass.

[0120] Four cylindrical glass reactors with an effective volume of 50 liters were constructed, and four sets of test packing materials of equal volume were added to each reactor. Prepared simulated aquaculture wastewater was injected into the reactors, with ammonium chloride added as the sole nitrogen source, controlling the initial ammonia nitrogen concentration at 5.0 mg / L. An equal amount of commercially available pure-culture freeze-dried nitrifying bacteria preparation was inoculated. The reactors were operated under continuous constant aeration at a water temperature of 28℃. Ammonia nitrogen concentrations were sampled daily, and consumed substrate was replenished. The time when the ammonia nitrogen degradation rate remained above 90% for three consecutive days was recorded as the biofilm formation and maturity time.

[0121] After the biofilm in each reactor matured and operated stably for one week, the ultimate nitrogen removal rate (UDR) test was conducted. A high concentration of ammonium chloride and sodium nitrite solution was instantaneously added to the system, causing the initial ammonia nitrogen and nitrite concentrations in the water to spike to 20.0 mg / L. High-frequency sampling was performed over the following 24 hours. By fitting the slope of the linear interval of the concentration decrease curve, the maximum ammonia oxidation rate (AOR) and maximum nitrite oxidation rate (NOR) per unit volume of packing material were calculated.

[0122] Table 1. Test data on hydrophilicity and biochemical denitrification kinetics of each group of biological packing materials.

[0123] Test object Natural settling time (s) Saturated water absorption ratio (%) Time to maturity of biofilm (d) Maximum ammonia oxidation rate (g N / m 3 • d) <![CDATA[Maximum nitrite oxidation rate (gN / m 3 ·d)]]> Preparation Example 1 4.2 812.4 9 154.3 112.5 Preparation Example 2 5.7 765.1 10 142.1 105.8 Preparation Example 3 3.8 889.6 8 171.6 128.4 Comparative Example 5 3854.6 121.3 28 45.2 31.6

[0124] Conclusion Analysis:

[0125] Combined with Table 1 Figure 1 It is evident that unmodified polyethylene biofiller exhibits materials science limitations in denitrification biochemical treatment systems. (Observation) Figure 1The bar chart and line graph of Comparative Example 5 show that the inherent hydrophobic properties of polyethylene make it extremely difficult for the test sample to settle naturally after being immersed in water. The suspension and floating for over 3,000 seconds hinders effective mass exchange between the deep pores inside the material and the external water, directly reflected in its low saturated water absorption rate of only 121.3%. This interfacial repulsion effect directly interferes with the early colonization process of the microbial community. Because autotrophic nitrifying bacteria with a slight negative charge in the water are unable to overcome the surface tension at the solid-liquid interface and thus attach to the hydrophobic substrate, the actual experimental process... Figure 1 The corresponding broken line trend on the right side matches perfectly, while Comparative Example 5 took a full 28 days to barely reach a stable biofilm state. After the polyurethane matrix was modified by introducing chain extenders and crosslinking agents through a specific process, the thermodynamic behavior of the material's phase interface was fundamentally reversed. The modified samples prepared in Examples 1 to 3 were all able to rapidly penetrate the water surface and sink to the bottom of the container within seconds. Figure 1 The corresponding bar chart data, showing saturation water absorption ratios of 765.1% to 889.6%, demonstrates that the three-dimensional internal micropores constructed through cross-linking are wetted by water molecules. This three-dimensional and highly hydrophilic microenvironment provides an ideal attachment anchor for polar microorganisms. In the early stages, the bacterial community no longer needs to consume a large amount of energy to secrete extracellular polymers to passively modify the substrate surface, thus compressing the fragile biofilm maturation period to 8 to 10 days.

[0126] Combined with Table 1 Figure 2 It can be seen that the determination of the denitrification kinetic limiting parameters further confirms the advantages at the microecological level. From Figure 2 The contrast between the light and dark gray bar charts clearly shows that the maximum ammonia oxidation rate and maximum nitrite oxidation rate of the hydrophilic modified filler generally jump to about three times that of the traditional polyethylene material. Taking Preparation Example 3, which shows the most outstanding performance, as an example, its maximum ammonia oxidation rate reaches 171.6 gN / m³. 3 ·d, far exceeding the 45.2 gN / m of Comparative Example 5. 3 •d. The hydrophilicization of the filler substrate not only increases the effective biomass loading per unit volume, but also constructs unobstructed substrate diffusion channels within the pores, allowing high concentrations of ammonia nitrogen substrate and dissolved oxygen molecules to easily penetrate the water film and reach the bacterial cells, maintaining the high-speed operation of the biochemical reaction enzyme system. The physicochemical changes at the microscopic interface of the bottom material ultimately achieve a qualitative leap in the macroscopic biochemical reaction rate. The high treatment efficiency observed in conventional experiments provides a sufficient buffer margin for subsequent responses to the acute nitrogen load shock caused by high-density feeding in the later stages of shrimp larvae rearing.

[0127] Test Example 2:

[0128] This test case mainly verifies the hydraulic microcirculation characteristics of the in-situ biological tank and the anti-clogging and self-cleaning mechanism of the bubble sweeping system. The experimental object is the in-situ biological tank with the structure set in Example 1. The comparison objects are the biological tank in Comparative Example 2, which uses a mechanical centrifugal water pump to replace bottom aeration to drive circulation, and the biological tank in Comparative Example 3, which closes the external auxiliary micropore backwashing air source.

[0129] The three types of micro in-situ biological test prototypes were built in three sets of standard experimental tanks. Example 1 maintained the operation of both bottom-level airlift power and the outer bubble sweeping net through dual pipelines; Comparative Example 2 did not use the airlift effect generated by the bottom nanoporous aeration disc 6 as the circulation power, but instead used an external centrifugal water pump with equivalent flow parameters to directly draw water from inside the tank 1 to generate forced circulation, while maintaining basic oxygen supply conditions in the packing area inside the tank through an independent aeration branch; Comparative Example 3 maintained the bottom-level airlift power, but cut off the auxiliary microporous backwashing air pipe 4 outside the water inlet window 8 of the escape-proof net frame 3. All three systems were equipped with a standard escape-proof net frame 3 with a pore size of 200 μm.

[0130] Start each system's circulation device and run it for 30 minutes to stabilize the basic hydrological flow pattern. Using a high-precision three-dimensional Doppler microvelocity meter, select 15 measuring points in a grid pattern, 5 mm away from the outside of the escape-prevention net frame 3, record the local water inflow suction velocity perpendicular to the net surface, and calculate the overall average value.

[0131] A mixed homogenate made of crushed kelp and shrimp feed was quantitatively added to the water in each test tank to artificially create a high-load turbidity test water quality with a total suspended particulate matter concentration as high as 120 mg / L, thereby simulating the harsh water conditions in the middle and late stages of aquaculture where uneaten feed and excrement accumulate.

[0132] The system operated continuously for 72 hours after the suspended solids were introduced. Every 12 hours, the actual water levels outside the escape-prevention net frame 3 and inside the in-situ tank were simultaneously measured using a high-precision differential pressure level gauge. The time-series changes in the internal and external water head level difference were recorded and calculated to assess the dynamic evolution of the filter screen pores being blocked by organic debris.

[0133] Table 2. Dynamic test data on the hydraulic characteristics and filter anti-clogging performance of the in-situ biological tank.

[0134] Test object Inlet water suction velocity (cm / s) 12-hour liquid level difference (mm) 24-hour liquid level difference (mm) 36-hour liquid level difference (mm) 48-hour liquid level difference (mm) Liquid level difference over 60 hours (mm) 72-hour liquid level difference (mm) Example 1 0.86 2.1 2.5 3.2 2.9 3.4 3.7 Comparative Example 2 12.35 14.6 29.8 45.1 63.7 81.2 104.5 Comparative Example 3 0.82 6.4 13.7 25.4 38.9 52.3 68.1

[0135] Conclusion Analysis:

[0136] Combined with Table 2 Figure 3 (a) It can be seen that there are fundamental differences in the hydrodynamic mechanisms between traditional centrifugal water pumps and air-lift negative pressure microcirculation. Observation Figure 3(a) The bar chart reflecting the performance of different prototype devices clearly shows that in Comparative Example 2, due to the use of a mechanical water pump to forcibly pump water, the inflow velocity on the surface of the escape-proof net frame 3 surged to 12.35 cm / s. This strong, concentrated water flow far exceeds the escape dynamic limit of early shrimp larvae, which is typically only 2 to 5 cm / s. In practical engineering applications, this could easily lead to a large number of larvae being forcibly adsorbed onto the net surface, causing mechanical crushing and death. Examples 1 and Comparative Example 3 abandoned the mechanical pump and relied on the density difference of the air-water mixture generated by internal nano-aeration to drive fluid circulation. Both examples... Figure 3 The bar chart in (a) shows extremely low heights, corresponding to influent suction velocities strictly limited to extremely low levels of 0.86 cm / s and 0.82 cm / s, respectively. This gentle flow field design based on airlift dynamics cuts off the pathway for seedlings to be entrained and adsorbed by high-speed water flow from the fundamental mechanism of fluid mechanics, providing basic biosafety assurance for the seedling stage.

[0137] Combined with Table 2 Figure 3 (b) It can be seen that although the weak inflow velocity ensures the safety of the shrimp larvae, it makes the micron-sized mesh highly susceptible to the adhesion and trapping of suspended organic debris. Figure 3 (b) The recorded test run time and the dynamic evolution curve of the water head level difference inside and outside the filter screen clearly expose this engineering pain point. Observing the dashed-triangular broken line representing Comparative Example 3, in the absence of the auxiliary microporous backwashing air pipe 4, the system relies solely on pure negative pressure for water intake. The water head level difference inside and outside the filter screen shows an irreversible upward trend with the increase of test run time, deteriorating from 6.4 mm at 12 hours to 68.1 mm at 72 hours. This indicates that the micro-filter pores are rapidly blocked by polysaccharide mucus and crushed uneaten feed accumulated in the aquaculture water. The dashed-square broken line representing Comparative Example 2 reflects that the high-speed concentrated suction formed by the mechanical water pump continuously presses suspended particles onto the surface of the escape-proof net frame 3, causing organic debris to be rapidly compacted, bridged, and form a blockage layer around the mesh. The water level difference continues to soar throughout the test cycle, exceeding 100 mm to reach 104.5 mm at 72 hours. At this point, the material exchange function between the system and the external pool water is almost paralyzed. Example 1 breaks the cycle of passive clogging by cleverly adding an auxiliary microporous backflushing air source outside the water inlet window 8. Figure 3In (b), the solid dotted line representing Example 1 remains smoothly close to the horizontal axis. During the complete test run from 12 to 72 hours, the water head level difference between the inside and outside of the filter screen is 2.1 mm, 2.5 mm, 3.2 mm, 2.9 mm, 3.4 mm, and 3.7 mm, respectively, and is always firmly locked within a small fluctuation range. The continuously rising microbubble flow attached to the screen forms a high-frequency oscillating fluid shear barrier on the outside of the screen surface. The pulsating momentum transfer of the gas-liquid two-phase flow continuously strips away the tiny particles that attempt to adhere to the periphery of the pores. Relying on this low-energy physical self-cleaning mechanism, the system maintains excellent hydraulic permeability when dealing with the long-term impact of high-load turbid water quality, providing a reliable guarantee for the internal hydrophilic filler to maintain a sufficient supply of ammonia nitrogen substrate.

[0138] Test Example 3:

[0139] This test case primarily verifies the changing trends of water quality physicochemical indicators and the maintenance of transparency throughout the entire seeding cycle, and compares the differences in engineering applications of different seeding strategies in suppressing water toxin outbreaks and maintaining water visibility. The experimental subjects were independent seeding systems constructed in Examples 1, 2, and 3, which combined early-stage clear water seeding with later-stage in-situ biological tank treatment. Three control groups were also introduced: Comparative Example 1 used a traditional biofloc seeding system with carbon source added throughout the process; Comparative Example 4 used a system with later-stage in-situ biological tanks but with the packing material inside the tank not pretreated and matured in an off-site manner; and Comparative Example 5 used a system with later-stage in-situ biological tanks but with conventional polyethylene (PE) packing material inside the tank.

[0140] Six identical indoor standardized shrimp larvae rearing ponds, each with an effective volume of 10 cubic meters, were prepared. To ensure comparability between different water treatment schemes, this test case adopted unified standardized evaluation conditions. All groups were stocked with the same batch of Litopenaeus vannamei larvae at a stocking density of 1600 shrimp / cubic meter, and a 30-day rearing evaluation was conducted. Examples 1 to 3 used the five types of hydrophilic modified porous polyurethane biological packing material, packing ratio, ex-situ biofilm maturation parameters, in-situ biological tank intervention method, escape-proof net frame with three apertures, aeration intensity, and subsequent water change control methods as specified in their respective examples. Comparative Examples 1, 4, and 5 used the water treatment methods in their corresponding comparative schemes. After the initial rearing showed no abnormalities, all groups implemented a unified microparticle pellet feed feeding system, lighting conditions, and temperature control system during the subsequent 30-day rearing period.

[0141] Throughout the 30-day seedling period, water samples were collected daily at 9:00 AM at a fixed location 30 cm below the water surface in the center of each seedling pond. Turbidity (NTU) was measured using a calibrated portable turbidity meter. Considering the phased differences in the seedling strategy over time and to ensure consistency in the statistical standards of each group, this test case uniformly used day 10 as the dividing point between the early and late phases, calculating the average turbidity for the early phase (days 0-10) and the average turbidity for the late phase (days 11-30).

[0142] Water samples were collected from each pond every two days during the seedling stage. The analysis was conducted strictly according to national standard water quality analysis methods. The total ammonia nitrogen (TAN) concentration was determined using the salicylic acid spectrophotometric method, and the nitrite nitrogen (NO2-N) concentration was determined using the diazo-coupling spectrophotometric method. By integrating the monitoring data from the entire period, the maximum peak values ​​of TAN and nitrite nitrogen in each pond during the later stages of seedling cultivation, due to accumulated feed load, were screened and extracted. This allowed for the evaluation of the system's buffering and purification capabilities against sudden water quality deterioration.

[0143] Table 3. Water quality physicochemical core indicators and transparency test data for each seedling scheme throughout the entire life cycle.

[0144] Test object Early stage average turbidity (NTU) Later average turbidity (NTU) Maximum ammonia nitrogen peak value (mg / L) Maximum nitrite peak value (mg / L) Example 1 5.2 6.8 0.43 0.21 Example 2 4.8 5.9 0.51 0.28 Example 3 5.5 7.4 0.38 0.15 Comparative Example 1 45.6 98.4 2.14 3.65 Comparative Example 4 5.1 12.6 4.82 5.12 Comparative Example 5 5.3 18.2 3.15 2.87

[0145] Conclusion Analysis:

[0146] Combined with Table 3 Figure 4 (a) It can be seen that the traditional biofloc method and the clear water-in-situ tank combination scheme of the present invention exhibit two completely different evolutionary paths in terms of water quality sensory characteristics. Observation Figure 4 (a) shows a bar chart reflecting the average turbidity (NTU) at different seedling stages. Light gray bars represent the average turbidity in the early stage (0-10 days), and dark gray bars represent the average turbidity in the later stage (11-30 days). The two sets of bars representing Comparative Example 1 are particularly striking. Due to the continuous addition of carbon sources to the water to stimulate the proliferation of heterotrophic bacteria, the average turbidity in the early stage (0-10 days) has already reached 45.6 NTU. As uneaten feed and feces increase and flocs age in the later stages of cultivation, the average turbidity in the later stage (11-30 days) soars to 98.4 NTU. In actual production observation, this high turbidity is usually accompanied by a large amount of foam accumulation on the water surface, making it impossible for farmers to see the feeding status and healthy background color of the shrimp larvae at the bottom of the water layer. Examples 1 to 3 effectively broke the chain of uncontrolled growth of suspended particles in the water by using a strategy of large-scale water exchange in the early stage combined with closed biological tanks in the later stage. Figure 4In (a), the average turbidity (0-10 days) of the three groups in the early stage was effectively controlled within the extremely low range of 5.2 NTU, 4.8 NTU, and 5.5 NTU, respectively. Even after the large-scale water change was stopped and the in-situ biological tank took over the purification, the average turbidity (11-30 days) only increased slightly, remaining at 6.8 NTU, 5.9 NTU, and 7.4 NTU, respectively. In contrast, although Comparative Examples 4 and 5 also maintained a low average turbidity (0-10 days) of 5.1 NTU and 5.3 NTU, respectively, due to the difference in the core efficiency of subsequent biological treatment, their average turbidity (11-30 days) climbed to 12.6 NTU and 18.2 NTU, respectively, indicating that the water quality had already shown signs of deterioration. The system in the example maintained a clear and visible state throughout the entire cycle, eliminating sensory interference caused by the decay of stagnant flocs, and laying the foundation for dealing with substrate impact in the later stage.

[0147] Combined with Table 3 Figure 4 (b) It can be seen that constructing the core of water treatment on the ex-situ pre-cured hydrophilic modified packing provides substantial denitrification flux support to resist acute nitrogen shock in the later stage of aquaculture. Figure 4 (b) Specifically, it presents the peak concentrations (mg / L) of water toxins in each system when facing substrate loading, with the dark gray column corresponding to the maximum ammonia nitrogen peak and the light gray column corresponding to the maximum nitrite peak. As the feeding amount increases exponentially after the fry reach day 15, the substrate release rate within the water body far exceeds the metabolic limit of natural aquatic microorganisms. From Figure 4(b) The column heights show that Examples 1 to 3 exhibited extremely strong buffering capacity, with maximum ammonia nitrogen peaks of only 0.43 mg / L, 0.51 mg / L, and 0.38 mg / L, respectively, and maximum nitrite peaks as low as 0.21 mg / L, 0.28 mg / L, and 0.15 mg / L, respectively, consistently controlled below the safe concentration standards for aquaculture. In stark contrast, Comparative Example 4, due to the lack of prior ex-situ biofilm maturation of the packing material in the in-situ biological tank, required a natural colonization period of up to ten days after being placed in the seedling pond. During this period, the biochemical purification system was essentially inactive, resulting in a maximum ammonia nitrogen peak of 4.82 mg / L and a maximum nitrite peak of 5.12 mg / L. This lethal level of toxin accumulation could easily lead to the complete annihilation of the shrimp larvae. Although Comparative Example 5 underwent pretreatment, it was filled with conventional hydrophobic PE packing material. Limited by the low water absorption and biofilm activity of the bottom material, the nitrifying bacteria load per unit volume could not match the massive nitrogen excretion load in the later stages, resulting in dangerously high peak ammonia nitrogen and nitrite levels of 3.15 mg / L and 2.87 mg / L, respectively. Comparative Example 1, using the traditional floc method, also exhibited the drawback of extreme instability in the mid-to-late stages, with peak ammonia nitrogen and nitrite levels reaching 2.14 mg / L and 3.65 mg / L, respectively. The on-site water quality evolution clearly demonstrates that visible physical intervention in the early stages must be seamlessly integrated with high-flux biological metabolism in the later stages. A pre-matured, highly efficient micro-ecological community can instantly take over the nitrogen cycle in the water, cutting off the pathway for harmful toxins to accumulate into nitrite and even non-ionic ammonia.

[0148] Test Example 4:

[0149] This test case primarily transforms the aforementioned technical indicators into direct production and economic indicators. By evaluating the final seedling survival rate and the frequency of human intervention, the economic benefits and equipment operation and maintenance stability of this invention in actual shrimp seedling production are assessed. The test subjects include the complete seedling systems corresponding to Examples 1 to 3 and Comparative Examples 1 to 5.

[0150] In Test Example 4, to ensure the comparability of production effect evaluation between the examples and comparative examples, all test ponds adopted standardized evaluation conditions with an effective volume of 10 cubic meters, a stocking density of 1600 shrimp / cubic meter, and an initial stocking quantity of 16,000 shrimp. A 30-day seedling production cycle was conducted uniformly. After the 30-day standardized seedling production cycle, the water in each test pond was drained, and standardized fine-mesh nets were used to collect all remaining shrimp larvae from the bottom of the ponds. During the collection process, large suspended particles and biological debris in the water were simultaneously filtered out. A combination of weighing sampling and localized manual counting was used to count the total number of healthy surviving shrimp larvae in each pond, and the final survival rate was calculated based on the uniform initial stocking quantity of 16,000 shrimp per pond.

[0151] During the one - month production operation period, the time span of the continuous normal operation of the water treatment devices in each system was recorded in detail. The number of days between forced shutdowns for maintenance due to fluid circulation stagnation, filter screen blockage, or extremely deteriorated water quality was defined as the mean time between failures (MTBF) of the water treatment system. For the examples and comparative examples using in - situ bio - barrels, it specifically corresponded to the time point when the water flow circulation inside the barrel body 1 failed; for Comparative Example 1 using the traditional flocculation method, it corresponded to the time point when the bottom - pool sewage filter screen was blocked by flocs, resulting in the inability to discharge sewage.

[0152] Full - time personnel were arranged to log all equipment intervention operations. During the entire fry - seedling rearing cycle, the total number of times when, due to the loss of hydrodynamic force or the failure of physical interception, a high - pressure water gun was forced to be used to violently wash and peel the anti - escape net frame 3 around the in - situ bio - barrel or the bottom - pool sewage component was counted and recorded as the total number of passive cleanings for the entire cycle.

[0153] Table 4. Statistical test data of production benefits and equipment operation and maintenance for each fry - seedling rearing system

[0154] Test object Final seedling survival rate (%) Mean time between failures (MTBF) of a water treatment system (d) Total number of passive cleaning cycles (times) Example 1 91.4 28.5 1 Example 2 88.7 30.0 0 Example 3 93.2 29.2 1 Comparative Example 1 64.3 11.2 3 Comparative Example 2 38.6 3.4 8 Comparative Example 3 54.1 4.2 7 Comparative Example 4 18.5 15.6 2 Comparative Example 5 47.9 14.3 2

[0155] Note: The production benefit and equipment operation and maintenance data of Examples 1 - 3 and Comparative Examples 1 - 5 listed in Table 4 were all obtained based on the unified standardized evaluation conditions of Test Example 4, that is, the effective volume of each test pool was 10 cubic meters, the fry - stocking density was 1600 tails per cubic meter, and the fry - seedling rearing evaluation period was 30 days.

[0156] Conclusion analysis:

[0157] Combined with Table 4 and Figure 5 (a) It can be seen that in the actual production scenario, systematic mistakes in a single link will cause a substantial blow to the survival rate of shrimp fry, and the systematic engineering design of the present invention has established a strict safety barrier for the fry - seedling rearing period. Observe Figure 5(a) The vertical axis reflects the final survival rate (%). The survival rates of Examples 1, 2, and 3 are as high as 91.4%, 88.7%, and 93.2%, respectively, firmly occupying the range above the high-yield baseline. The physical and chemical mechanisms leading to large-scale seedling mortality in the control groups are different. In Control Example 2, due to the simple use of mechanical pumping, the strong local physical adsorption force caused direct mechanical damage to the shrimp seedlings in the planktonic state, and its final survival rate (%) dropped to 38.6%. Although there was no risk of physical entrainment in Control Example 4, the lack of pretreatment and biofilm formation process in the internal packing material of the system led to the loss of control over ammonia nitrogen and other toxins in the water in the middle and late stages, causing acute poisoning of the entire pond, and the survival rate was a dismal 18.5%. In addition, the survival rate of Control Example 1, which used the traditional floc method, was 64.3%, while the survival rates of Control Examples 3 and 5, which used no external sweeping net and ordinary hydrophobic packing material, hovered only around 54.1% and 47.9%, respectively. Field research and observation show that traditional methods rely entirely on flocculants to treat water quality, resulting in the water's physicochemical indicators constantly fluctuating to a critical state. This leads to the elimination of some weaker larvae during the fragile molting period. The successful implementation scheme achieves such high and stable survival rates precisely because the underlying airlift hydrodynamic model avoids physical flow field damage, and the pre-cured, highly efficient hydrophilic microecological packing material eliminates the risk of chemical toxins. The optimization of the underlying fluid dynamics and materials science ultimately yielded definite results in the macroscopic survival rate data.

[0158] Combined with Table 4 Figure 5 (b) It can be seen that the fluid coupling operation of the bubble sweeping system and the underlying airlift components fundamentally reshapes the on-site operation and maintenance logic of aquaculture equipment. Analysis Figure 5In the dual-axis system constructed in (b), the light gray bar chart corresponding to the left vertical axis represents the mean time between failures (d), and the solid line graph with black squares on the right vertical axis represents the total number of passive cleanings (times) throughout the cycle. In Comparative Example 2, due to the use of a mechanical centrifugal water pump to form high-speed centralized suction, suspended particles are quickly compacted and adhere to the surface of the anti-escape mesh frame 3. Even with conventional oxygen supply conditions, it is difficult to avoid rapid deterioration of filter clogging. In Comparative Example 3, due to the lack of air bubble sweeping airflow outside the anti-escape mesh frame 3, it is unable to continuously remove organic debris and polysaccharide mucus adhering to the mesh surface. Therefore, the height of the light gray bars in both systems is significantly lower, and the corresponding mean time between failures (d) is severely compressed to only 3.4 days and 4.2 days, respectively. The high-load water quality environment at the site was extremely harsh. Every three to four days, the micron-sized escape-proof net frame 3 would be completely clogged by polysaccharide mucus and organic uneaten feed in the water. This forced the aquaculture personnel to shut down the system and remove it from the water for high-pressure washing. This was reflected in the line graph representing the total number of passive cleanings throughout the cycle, where the data points for the two comparative examples soared to a peak of 8 and 7 times, respectively. Although the situation was slightly better for comparative examples 1, 4, and 5, their mean time between failures (MTBF) was only maintained at 11.2 days, 15.6 days, and 14.3 days, respectively, corresponding to a total of 3, 2, and 2 passive cleanings throughout the cycle. In contrast, the system of the example with fully activated bubble sweeping showed a sustained and extremely stable pulsating scouring effect induced by airflow on the outer surface of the mesh. Taking Example 2 as an example, the system did not experience any substantial hydraulic blockage throughout the entire seedling stage, and its average fault-free operating period (d) reached 30 days at full load. The data point on the line graph directly hit the bottom, indicating that the total number of passive cleanings (times) throughout the entire cycle dropped directly to 0. The operating status of Examples 1 and 3 was also excellent, with fault-free periods of 28.5 days and 29.2 days respectively, and the corresponding number of passive cleanings on the line graph was only 1. This innovative engineering structure not only eliminates the dead spots of traditional equipment where dead skin adheres to the walls, and reduces the severe water disturbance and stress response caused by frequent high-pressure flushing to sensitive seedlings in the pool, but also enables the entire water treatment microcirculation system to have adaptive self-cleaning capabilities across the entire production cycle, completing the equipment technology iteration from passive manual repair to full maintenance-free operation.

[0159] See appendix Figure 6 -Appendix Figure 9The present invention also includes an in-situ biological tank for early-stage clear water seedling raising and later-stage in-situ treatment, comprising a tank body 1, an inlet window 8 on the side wall of the tank body 1, a support plate 7 inside the tank body 1, and a hydrophilic modified porous polyurethane biological filler 5 inside the tank body 1, the hydrophilic modified porous polyurethane biological filler 5 being located on top of the support plate 7. Rails 2 are fixedly connected to both the inner and outer sides of the tank body 1, and an anti-escape net frame 3 is engaged in the middle of the rails 2. A nanoporous aeration disc 6 is provided inside the tank body 1 to establish an air-lift negative pressure microcirculation inside the tank body 1. An auxiliary microporous backwashing air pipe 4 is provided at the air inlet end of the nanoporous aeration disc 6, and the other end of the auxiliary microporous backwashing air pipe 4 is located outside the inlet window 8 to establish an air bubble sweeping barrier outside the anti-escape net frame 3.

[0160] In one specific embodiment, the support plate 7 is horizontally fixed to the lower half of the tank body 1. The support plate 7 has water permeable holes. The function of the support plate 7 is to support the hydrophilic modified porous polyurethane biological filler 5, prevent the hydrophilic modified porous polyurethane biological filler 5 from settling and clogging the bottom structure, and at the same time, the water permeable holes ensure that water flow and air bubbles pass through smoothly. The hydrophilic modified porous polyurethane biological filler 5 is stacked on top of the support plate 7. The hydrophilic modified porous polyurethane biological filler 5 is used to provide a space carrier for nitrifying bacteria to attach and proliferate, and to intercept and degrade ammonia nitrogen in the water body when water flows through. The nanoporous aeration disc 6 is installed at the bottom of the tank body 1 below the support plate 7. After connecting to the external air source, the nanoporous aeration disc 6 releases microbubbles. The bubbles not only provide dissolved oxygen for the aerobic microorganisms attached to the hydrophilic modified porous polyurethane biological filler 5, but also the rising bubbles drive the water inside the tank body 1 to overflow upwards, generating a negative pressure suction effect inside the tank body 1. The negative pressure suction effect causes the water from the external seedling pond to pass through the water inlet window 8 and enter the tank body 1 to form a circulation. One end of the auxiliary microporous backwashing air pipe 4 is connected to the air inlet pipe of the nanoporous aeration disc 6, and the other end of the auxiliary microporous backwashing air pipe 4 passes through the side wall of the tank body 1 and extends to the bottom of the water inlet window 8. The auxiliary microporous backwashing air pipe 4 releases rising air bubbles. The air bubbles adhere to the outer surface of the escape-proof net frame 3 and move upward, peeling off the organic debris and polysaccharide mucus trapped on the surface of the escape-proof net frame 3, maintaining the hydraulic permeability of the water inlet window 8, and preventing the water inlet pores from being blocked.

[0161] See appendix Figure 6 and attached Figure 8 The anti-escape mesh frames 3 with different mesh counts are snapped into the inner and outer sides of the barrel body 1 by the rails 2. This is used to seamlessly replace the anti-escape mesh frames 3 with mesh frames of different counts.

[0162] In one specific embodiment, the guide rail 2 includes an inner sliding groove and an outer sliding groove that are parallel to each other. The guide rail 2 is used to provide vertical guidance and positioning for the escape-proof net frame 3 and to form a tight seal at the edge of the escape-proof net frame 3 to prevent the nauplius larvae of Litopenaeus vannamei from leaking out of the gap. The function of the escape-proof net frame 3 is to prevent the nauplius larvae of Litopenaeus vannamei from entering the interior of the barrel 1. In the early stages of shrimp larvae rearing, a smaller-diameter escape-proof net frame 3 is inserted into the inner chute to prevent the tiny early-stage Litopenaeus vannamei nauplii from being drawn into the tank 1 by the negative pressure water flow. When the Litopenaeus vannamei nauplii grows to the set size, its swimming ability increases and its body size increases. At this time, it is necessary to reduce the water flow resistance of the escape-proof net frame 3 and increase the water circulation flow. The operator aligns the new escape-proof net frame 3 with the outer chute and inserts it downwards so that the new escape-proof net frame 3 completely covers the water inlet window 8. Then, the old escape-proof net frame 3 in the inner chute is pulled upwards. Throughout the replacement process, the water inlet window 8 is always covered by a double or single layer of escape-proof net frame 3 to maintain the spatial isolation of the Litopenaeus vannamei nauplii.

[0163] Please see the appendix Figure 7 The volume of the hydrophilic modified porous polyurethane biofiller 5 accounts for 30% to 70% of the total internal volume of the barrel 1.

[0164] In one specific embodiment, the volume ratio of the hydrophilic modified porous polyurethane biological packing 5 to the total internal volume of the tank 1 is set to 30%, 50%, or 70%. The purpose of setting the volume ratio is to balance the biological treatment efficiency and hydraulic characteristics. If the packing volume ratio is less than 30%, the total surface area provided by the hydrophilic modified porous polyurethane biological packing 5 is limited, resulting in insufficient biomass of attached nitrifying bacteria, which cannot cope with the acute nitrogen excretion load caused by high-density feeding in the later stage of seedling cultivation. If the packing volume ratio is greater than 70%, the dense hydrophilic modified porous polyurethane biological packing 5 increases the resistance during the upward process of the air-water mixture, weakens the air lift negative pressure microcirculation power generated by the nanoporous aeration disc 6, and causes a dead water zone to form inside the tank 1. When filling the hydrophilic modified porous polyurethane biological packing 5, the total internal volume of the tank 1 from the bottom to the overflow port is measured, the required apparent volume of the hydrophilic modified porous polyurethane biological packing 5 is calculated according to the set volume ratio, and the corresponding volume of the hydrophilic modified porous polyurethane biological packing 5 is measured and put into the tank 1 and placed on the support plate 7.

Claims

1. A method for raising shrimp seedlings in clear water in the early stage and then treating them in situ in the later stage, characterized in that, Includes the following steps: Prepare the water body of the seedling pond to obtain the prepared seedling pond. At the same time, in an independent pretreatment tank, perform off-site biofilm maturation on the hydrophilic modified porous polyurethane biological packing material (5) in the in-situ biological tank to obtain the matured in-situ biological tank. Based on the prepared seedling pond, a compound probiotic preparation and live Brachiopoda foldis were inoculated into the seedling pond, and Litopenaeus vannamei nauplius were released. The nauplius vannamei larvae were fed with microparticle pellet feed, and the water was changed and sewage was drained daily to carry out the initial water clearing and seedling raising process. After the seedlings in the early stage reach the set time, the matured in-situ biological tank is semi-submerged and fixed in the seedling pond, and isolated by the anti-escape net frame (3). The nano-microporous aeration disc (6) at the bottom of the in-situ biological tank is opened to establish air lift negative pressure microcirculation. At the same time, the auxiliary microporous backwashing air pipe (4) outside the water inlet window (8) is opened to establish a bubble sweeping net barrier. Meanwhile, the daily water exchange rate is reduced for later in-situ treatment. Based on the seedling pond where the post-treatment is carried out, when the nauplius larvae of Litopenaeus vannamei grow to the set size, the escape-proof net frame (3) of the in-situ biological tank is replaced, and seedlings are continuously bred until they emerge and are transferred to another pond.

2. The shrimp seedling raising method according to claim 1, characterized in that, The specific procedures for preparing the water in the seedling pond are as follows: Seawater filtered by sand was injected into the seedling pond, and potassium persulfate compound salt was sprinkled for disinfection. Then sodium thiosulfate was sprinkled to eliminate oxidative residues, and sodium bicarbonate was added to adjust the total alkalinity of the water to 120-150 mg / L.

3. The shrimp seedling raising method according to claim 1, characterized in that, The specific process of ectopic biofilm maturation is as follows: The in-situ biological tank was placed in a separate pretreatment tank. Ammonium chloride was added to the pretreatment tank to achieve an ammonia nitrogen concentration of 3.0–5.0 mg / L, and simultaneously, 1.0–2.0 g / m³ of pure freeze-dried live bacterial powder nitrifying bacteria was added. 3 Turn on the nanoporous aeration disc (6) at the bottom of the in-situ biological tank and control the aeration intensity to 8-10 m. 3 / h·m 2 It runs continuously for 10 to 15 days to complete the ectopic biofilm maturation.

4. The shrimp seedling raising method according to claim 1, characterized in that, The specific procedures for daily water changes and wastewater discharge are as follows: Starting from the third day after stocking, open the drain pipe at the bottom of the pond daily to remove waste and replace it with fresh water of the same salinity. The daily water replacement volume should be 20%–30% of the total pond volume. Every 3–5 days, supplement the water with a compound probiotic preparation at a rate of 0.5–1.0 g / m³. 3 .

5. The shrimp seedling raising method according to claim 1, characterized in that, The preparation method of hydrophilic modified porous polyurethane biofiller (5) includes the following steps: Polypropylene glycol was dehydrated at 100–110 °C and under a vacuum of -0.09 MPa. After cooling, 4,4'-diphenylmethane diisocyanate was added, and the mixture was stirred and reacted under nitrogen protection to obtain an isocyanate-terminated polyurethane prepolymer. Mix the foaming materials evenly to prepare an aqueous foaming solution; At room temperature, the aqueous foaming liquid is added to the polyurethane prepolymer and mixed at high speed, and then poured into a mold to obtain a foaming system. After the foaming system has finished expanding and lost its fluidity, it is placed in an oven to mature, and finally cut into pieces to obtain the hydrophilic modified porous polyurethane biofiller (5).

6. The shrimp larvae raising method according to claim 5, characterized in that, The foaming raw materials include N-methyldiethanolamine, 1,1,1-trimethylolpropane, deionized water, stannous octoate, triethylenediamine, and polysiloxane-polyether copolymer.

7. The shrimp larvae raising method according to claim 1, characterized in that, The set time is 7 to 10 days after the seedlings are released; When the auxiliary microporous backwashing air pipe (4) outside the water inlet window (8) is opened, the air supply pressure is controlled at 0.02 to 0.05 MPa; The daily water exchange rate is controlled at 5% to 10%; The Litopenaeus vannamei nauplius were grown to a set size of PL15 or higher.

8. An in-situ biological tank for initial water seedling establishment and subsequent in-situ treatment, characterized in that: The method for raising shrimp seedlings according to any one of claims 1-7 includes a barrel (1), with a water inlet window (8) on the side wall of the barrel, a support plate (7) inside the barrel (1), and a hydrophilic modified porous polyurethane biological filler (5) inside the barrel (1). The hydrophilic modified porous polyurethane biological filler (5) is located on the top of the support plate (7). The inner and outer sides of the barrel (1) are fixedly connected with rails (2), and an anti-escape net frame (3) is clamped in the middle of the rails (2). A nanoporous aeration disc (6) is provided inside the barrel (1) to establish a negative pressure microcirculation inside the barrel (1). An auxiliary microporous backwashing air pipe (4) is provided at the air inlet end of the nanoporous aeration disc (6). The other end of the auxiliary microporous backwashing air pipe (4) is located outside the water inlet window (8) to establish an air bubble sweeping barrier outside the anti-escape net frame (3).

9. The in-situ biological tank according to claim 8, characterized in that, The anti-escape net frames (3) that are snapped into the inner and outer sides of the barrel body (1) have different mesh counts, which are used to seamlessly replace the anti-escape net frames (3) with net frames of different mesh counts.

10. The in-situ biological tank according to claim 8, characterized in that, The volume of the hydrophilic modified porous polyurethane biofiller (5) accounts for 30% to 70% of the total internal volume of the barrel (1).

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