Nitrification and denitrification culture system establishment method based on biofloc in-situ culture and culture system

Abstract

The invention discloses a nitrification and denitrification culture system establishment method based on biofloc in-situ culture and a culture system, and belongs to the technical field of aquaculture. Aiming at the problems of long establishment time of a nitrification system and incomplete nitrate nitrogen treatment in the prior art, the invention provides a technical scheme of establishing a nitrification and denitrification culture system on the basis of in-situ culture of biological floccules, and by constructing the culture system, in-situ culture of the biological floccules and domestication of endogenous indigenous nitrification and denitrification flora, the nitrification and denitrification culture system is established. Meanwhile, the culture system is dynamically maintained, rapid establishment of a nitrification system in the culture process and full-path conversion of nitrogen-water body nitrogen (NH3-N, NO2-N, NO3-N)-nitrogen which is not digested and utilized in feed are achieved through the system, and the system has the advantages of being simple in structure, easy and convenient to operate and efficient in water treatment; the method can be widely applied to breeding of aquatic animals with the capacity of tolerating high-concentration suspended particles and adapting to a high-density breeding environment.

Description

Technical Field

[0001] This application relates to the field of aquaculture technology, and in particular to a method for establishing a nitrification-denitrification aquaculture system based on in-situ culture of bioflocs and an aquaculture system. Background Technology

[0002] In modern aquaculture, microbial floc culture has gradually gained widespread application as an innovative water quality management method. This method promotes the development of microbial communities in the water, forming a dynamically balanced ecosystem, aiming to improve water quality, reduce diseases, and mitigate environmental impact.

[0003] Currently, biofloc technology has two modes: heterotrophic and autotrophic. Heterotrophic bioflocs are difficult to promote due to their high oxygen consumption and difficulty in management. In comparison, autotrophic bioflocs have shown significant advantages in aquaculture, especially in promoting in-situ culture technology and intensive and sustainable aquaculture models, and have important theoretical and practical value.

[0004] However, the current problem is that establishing a nitrification system in situ with bioflocs takes a long time, and the long-term accumulation of nitrite puts farmed animals under constant stress, easily leading to farming failure. Although ex-situ culture can shorten the establishment time of the nitrification system, it requires advance cultivation or preservation, which limits production. After the nitrification system is established, the problem of nitrate accumulation arises, and the discharge of aquaculture wastewater can also cause eutrophication of water bodies. Summary of the Invention

[0005] The main objective of this application is to provide a method and system for establishing a nitrification-denitrification aquaculture system based on in-situ culture of bioflocs. This application eliminates the need for pre-culturing bioflocs for ex-situ inoculation and for physically isolating nitrification and denitrification units, enabling the conversion of undigested nitrogen in feed to nitrogen trioxide (NH3) in water during the aquaculture process. - -N, NO2 - -N, NO3 - The complete conversion of nitrogen (N-N) is simple and efficient, laying a technological foundation for the large-scale development of green and environmentally friendly aquaculture.

[0006] To achieve the above objectives, this application proposes a method for establishing a nitrification-denitrification aquaculture system based on in-situ culture of bioflocs, the method comprising: Step (1) Construction of the aquaculture system: The aquaculture system includes: aquaculture pond, centrifugal pump, water pushing and oxygenation device, biofloc collection device and plastic pipe fittings; Step (2) In-situ culture of bioflocs: The aquaculture water in the aquaculture pond is filtered and disinfected. After testing and confirming that there is no disinfectant residue, Bacillus activating solution is added. On the day after the addition of the Bacillus activating solution, the aquaculture animals and feed are added to the aquaculture pond. At fixed times for 12 to 14 consecutive days, organic carbon source is added to the aquaculture pond. During the in-situ culture of bioflocs, if the pH value of the aquaculture water is <7.0 and / or the total alkalinity is <100 mg / L, sodium bicarbonate is used for adjustment. Step (3) Acclimation of endogenous native nitrifying and denitrifying bacteria: Before the nitrification system matures, feed is added to the aquaculture water at 70% to 80% of the preset normal feeding amount, and sodium bicarbonate is added to increase the total alkalinity of the aquaculture water to above 250 mg / L, and the pH value is maintained at 7.5 to 8.5. After the nitrification system matures, feed is added to the aquaculture water according to the preset normal feeding amount, and Bacillus is added every 4 to 6 days at a concentration of 1 mg / L. Sodium bicarbonate is used to control the total alkalinity in the range of 150 to 200 mg / L and the pH value is maintained at 7.0 to 8.0. The concentration of biofloc is dynamically monitored and controlled using an Inhofe conical tube and the biofloc collection device. The water flow velocity flowing to the biofloc deposition tube in the biofloc collection device is adjusted to control the biofloc concentration FV30 ≤ 15 ml / L until the nitrification-denitrification system matures. Step (4) Dynamic maintenance of the aquaculture system: After the nitrification and denitrification system matures, if the farmed animal is shrimp, the concentration of bioflocs FV30 in the aquaculture pond is adjusted to 5~15 ml / L; if the farmed animal is fish, the concentration of bioflocs FV30 in the aquaculture pond is adjusted to 10~25 ml / L; the floc structure is maintained by adding 1 mg / L of Bacillus to the aquaculture water every 4~6 days; the total alkalinity of the aquaculture water is adjusted to 130~160 mg / L and the pH value is maintained at 7.5~8.0 using sodium bicarbonate; the water loss in the aquaculture pond is replenished every 3~5 days.

[0007] In one embodiment, the water temperature in the aquaculture pond is controlled at 22~33 ℃, and the light intensity is ≤50 lx.

[0008] In one embodiment, in step (2), the organic carbon source is at least one of brown sugar, raw sugar and molasses.

[0009] In one embodiment, in step (2), the feeding time of the farmed animals is 2 hours after the farmed animals are put into the breeding pond.

[0010] In one embodiment, in step (2), the method of delivering the organic carbon source includes: Starting from the day of feeding, the organic carbon source is added to the aquaculture pond at a fixed time and in a preset ratio for 5 to 7 consecutive days, and the ratio between the daily addition of the organic carbon source and the daily addition of the feed is ≥3.0. Then, the addition of the organic carbon source is gradually reduced until it drops to 0 g on the 12th to 14th day.

[0011] In one embodiment, in step (3), the maturity of the nitrification system is indicated by the ammonia nitrogen and nitrite in the aquaculture water of the aquaculture pond both dropping to below 0.5 mg / L, and the maturity of the nitrification-denitrification system is indicated by the nitrate in the aquaculture water of the aquaculture pond dropping to below 0.5 mg / L.

[0012] In one embodiment, in step (3), the water flow velocity is ≤0.5 m. 3 / h.

[0013] To achieve the above objectives, this application also proposes an aquaculture system applicable to the method for establishing a nitrification-denitrification aquaculture system based on in-situ culture of bioflocs as described above. The aquaculture system includes: an aquaculture pond, a centrifugal pump, a water-pushing and aeration device, a biofloc collection device, and plastic pipe fittings.

[0014] In one embodiment, the length-to-width ratio of the aquaculture pond is ≥2.5, the inner corners are set with inner rounded corners, and a flow guide wall is provided in the middle area; The water-pushing and oxygenating device is based on the Venturi effect, is made of plastic pipes, and is fixed to the bottom of the aquaculture pond along the water flow direction in the aquaculture system, with intervals of 3-5 m between each other. The volume of the biofloc collection device accounts for ≥1% of the aquaculture water in the aquaculture pond, and the cone angle of its conical part is 60°~120°.

[0015] In one embodiment, the diversion wall includes at least one of a wall, a baffle, a geomembrane, and a woven membrane.

[0016] Compared with the prior art, the beneficial effects of this application include: (1) Simple structure: The aquaculture system used in the method of establishing the nitrification and denitrification aquaculture system only requires three core components: centrifugal pump, water pushing and oxygenation device and biofloc collection device. It can achieve the effects of pushing water, oxygenation and dynamic control of floc concentration without complicated facilities.

[0017] (2) Easy to operate: The in-situ culture and water treatment mode is adopted. There is no need for off-site inoculation, pre-culture of bioflocs or physical isolation of nitrification and denitrification units. There is no need to pay attention to the C / N ratio. The nitrification and denitrification aquaculture system can be established by operating in stages and steps, which is convenient for front-line technicians to operate.

[0018] (3) Short establishment time of nitrification system: The cycle from water intake to the maturity of endogenous indigenous nitrification system is less than 41 days, which is significantly shorter than the maturity cycle of existing in-situ culture nitrification system, thus relieving the stress of nitrite on farmed animals in advance.

[0019] (4) Strong water treatment capacity: It can achieve the goal of "removing nitrogen from feed that is not utilized by farmed animals and reducing nitrogen in water (NH3)". - -N, NO2 - -N, NO3 - The entire process of converting nitrogen (N) into nitrogen gas ensures that the concentration of nitrogen in water is stably controlled at ≤0.5mg / L, breaking through the bottleneck of nitrate accumulation in aquaculture systems, achieving near-zero emissions during the aquaculture process, and significantly reducing the eutrophication threat posed by aquaculture wastewater to the ecological environment. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0021] To more clearly illustrate the technical solutions in the embodiments or conventional technologies of this application, the accompanying drawings used in the description of the embodiments or conventional technologies will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating an embodiment of this application; Figure 2 This is a schematic diagram of the aquaculture system provided in the embodiments of this application; Figure 3 This is a schematic diagram of the water-pushing and oxygenating device provided in the embodiments of this application; Figure 4 This is a graph showing the variation of nitrogen in the aquaculture water in Example 1 of this application.

[0023] Explanation of reference numerals in the attached figures: 100. Aquaculture pond; 101. Flow guide wall; 102. Ecological passage; 103. Plastic drain pipe; 104. Centrifugal pump; 105. Main water pipe; 106. Water-pushing and oxygenating device; 107. Biofloc collection device; 108. Drainage tube; 109. Drainage tube ball valve; 110. Biofloc deposition tube; 111. Return pipe; 112. Biofloc drain valve; 113. Aquaculture pond water drain valve; 201. Threaded union; 202. Throat; 203. Intake pipe.

[0024] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The following detailed description, with appropriate reference to the accompanying drawings, discloses the method for establishing a nitrification-denitrification aquaculture system based on in-situ culture of bioflocs and the implementation method of the aquaculture system of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0026] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~10 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" means that all real numbers between "0~5" have been listed in this article; "0~5" is just a shortened representation of these numerical combinations. In addition, when a parameter is stated as ≥2, it is equivalent to disclosing all real numbers where the parameter is 2 or greater than 2; when a parameter is stated as ≤100, it is equivalent to disclosing all real numbers where the parameter is 0 to 100.

[0027] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0028] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0029] Conventional biofloc technology includes two modes: heterotrophic and autotrophic. Heterotrophic bioflocs are difficult to promote due to their high oxygen consumption and management challenges. In contrast, autotrophic bioflocs have shown significant advantages in aquaculture, especially in promoting in-situ culture technology and intensive, sustainable aquaculture models, holding important theoretical and practical value. However, current challenges include the long time required for in-situ nitrification system establishment with bioflocs, leading to prolonged nitrite accumulation and stress on farmed animals, potentially causing aquaculture failure. While ex-situ culture can shorten the nitrification system establishment time, it requires advance cultivation or preservation, limiting production. After the nitrification system is established, nitrate accumulation becomes a problem, and the discharge of aquaculture wastewater can also cause eutrophication.

[0030] Based on this, refer to Figure 1 Embodiment 1 of this application provides a method for establishing a nitrification-denitrification aquaculture system based on in-situ culture of bioflocs, including: Step (1) Construction of the aquaculture system: The aquaculture system includes: aquaculture ponds, centrifugal pumps, water-pushing and oxygenating devices, biofloc collection devices and related supporting plastic pipe fittings.

[0031] In one feasible embodiment, the aquaculture pond is rectangular with a length-to-width ratio ≥ 2.5. The inner corners are rounded to form inner rounded corners, and a flow guide wall is provided in the middle area of ​​the pond. A 10-30 cm wide ecological channel is reserved in the middle of the flow guide wall to facilitate the free movement of the farmed animals. The water-pushing and aeration device is based on the Venturi effect and is made using plastic pipes. It has the dual functions of directional water pushing and efficient aeration, creating a circular water flow in the aquaculture pond. It is fixed to the bottom of the pond along the water flow direction, spaced 3-5 m apart. The volume of the biofloc collection device accounts for ≥ 1% of the aquaculture water volume in the pond. Its conical part has a cone angle of 60°-120°, which can dynamically adjust the biofloc concentration in the pond to maintain water quality stability.

[0032] Optionally, refer to Figure 2The aquaculture system includes: an aquaculture pond 100, a centrifugal pump 104, a water-pushing and aeration device 106, a biofloc collection device 107, and related supporting plastic pipe fittings (e.g., PVC pipe fittings). The aquaculture pond 100 is rectangular, with a depth of 1.2m~1.5m and a length-to-width ratio ≥2.5. The inner corners of the walls are rounded. A flow guide wall 101 is provided in the central area of ​​the aquaculture pond 100, with a 20cm wide ecological channel 102 reserved in the middle to facilitate the free movement of the farmed animals. The flow guide wall 101 can be a conventional wall, baffle, or other isolation material that promotes the regular flow of water (e.g., geomembrane, woven membrane, etc.). When the centrifugal pump 104 is working, the water from the aquaculture pond enters the main water pipe 105 through the outlet holes on the plastic drain pipe 103 of the aquaculture pond 100. The outlet holes are evenly distributed on a section of the plastic drain pipe 103 30-40 cm from the bottom of the pond, with a diameter of 15 mm and a spacing of 1.5 cm. The main water pipe 105 is connected to a water-pushing and oxygenating device 106. This device, based on the Venturi effect, is made of plastic tubing and is fixed to the aquaculture pond 100 using pipe clamps. These devices are spaced 4 m apart within the aquaculture system and function as both directional water-pushing devices and highly efficient oxygenators, creating a circular water flow in the aquaculture pond 100. The biofloc collection device 107 is connected to the main water pipe 105 via a biofloc collection device inlet pipe 108. When in operation, the inlet pipe ball valve 109 on the inlet pipe 108 of the biofloc collection device 107 is opened, allowing pool water to enter the biofloc sedimentation pipe 110. The settled water then flows into the aquaculture pond 100 via the return pipe 111. The pool water enters the biofloc sedimentation pipe 110 tangentially through the inlet pipe 108 to create swirling sedimentation, improving separation efficiency. The conical portion at the bottom of the biofloc collection device 107 is made of white or transparent material for easy observation of biofloc deposition and discharge. Its volume accounts for 2% of the aquaculture water volume, and the cone angle is 75°. The aquaculture system also includes a biofloc drain valve 112 and an aquaculture pond water drain valve 113. Figure 2 The dashed arrows represent the water flow direction in the main water pipe 105 and the water-pushing and oxygenating device 106, while the solid arrows represent the water flow direction in the aquaculture pond 100.

[0033] Optionally, a schematic diagram of the water-pushing oxygenation device 106 is provided. Figure 3 The main water pipe 105 is connected to the water-pushing and oxygenating device 106 via a threaded union 201. When the water flows through the throat 202, the flow velocity increases significantly, forming a local negative pressure zone. The side of the throat 202 is connected to the air inlet pipe 203. The negative pressure draws air into the water flow, and the high-speed water flow cuts the air into tiny bubbles, forming an air-water mixed flow. The mixed flow is ejected from the outlet, propelling the water body to flow in a specific direction and increasing the dissolved oxygen content.

[0034] Step (2) In-situ culture of bioflocs: The aquaculture water in the aquaculture pond is filtered and disinfected. After testing and confirming that there is no disinfectant residue, Bacillus activating solution is added. The aquaculture animals and feed are added the day after the Bacillus activating solution is added. Organic carbon source is added to the aquaculture pond at fixed times for 12 to 14 consecutive days. During the in-situ culture of bioflocs, if the pH value of the aquaculture water is <7.0 and / or the total alkalinity is <100 mg / L, sodium bicarbonate is used for adjustment.

[0035] In one feasible embodiment, the method of adding Bacillus activating solution includes: mixing Bacillus, soluble organic carbon source and appropriate amount of pond water, aerating for 2-4 hours and then pouring into the aquaculture pond, and then adding soluble organic carbon source at fixed times for 12-14 consecutive days. The organic carbon source can promote the rapid formation of bioflocs, provide a carrier for the subsequent domestication of endogenous indigenous nitrifying and denitrifying bacteria, and is conducive to the control of ammonia nitrogen in the aquaculture water, reducing the stress of ammonia nitrogen on aquatic animals.

[0036] In one feasible embodiment, the timing of feed and animal feeding can be different; for example, the timing of feed feeding can be determined based on the type of animal being raised.

[0037] Optionally, if the farmed animals are juvenile shrimp, feeding should begin 2 hours after release to reduce the risk of cannibalism of molting individuals. If the farmed animals are fish fry, feeding should begin the day after release.

[0038] Optionally, starting from the day of feeding, add an organic carbon source (i.e., a soluble organic carbon source solution) to the aquaculture pond at fixed times and in a specific ratio for 5-7 consecutive days, with the daily ratio of organic carbon source addition to feed addition ≥3.0. The higher the crude protein content of the feed, the higher this ratio should be. Subsequently, gradually reduce the amount of soluble organic carbon source until, on day 12-14, the amount of organic carbon source is reduced to 0 g.

[0039] Optionally, during the culture of bioflocs, if the pH value is <7.0 and / or the total alkalinity is <100 mg / L (calculated as CaCO3; in subsequent examples, both pH value and / or total alkalinity are calculated as CaCO3), sodium bicarbonate may be used for adjustment.

[0040] Optionally, step (2) in situ culture of bioflocs includes: Day 1: The aquaculture water flows into the aquaculture pond after being filtered through a filter bag. Then, the centrifugal pump is turned on to start the aquaculture system. Chlorine dioxide is used for disinfection to make the effective chlorine dioxide concentration in the pond water 0.15 mg / L. After testing and confirming that there is no disinfectant residue, the pre-prepared Bacillus activating solution (1 mg / L Bacillus activator + 30 mg / L brown sugar + pond water, aerated for 3 h) is poured in.

[0041] Days 2-7: On day 2, farmed animals are introduced. Juvenile shrimp are fed 2 hours after introduction to reduce the risk of cannibalism of molting individuals. Fish fry are fed the day after introduction. During this period, brown sugar solution is sprinkled at fixed times each day. The ratio of brown sugar to feed weight is 3.0-5.0, with a higher ratio for higher crude protein content in the feed.

[0042] Days 8 to 13: Feed normally, sprinkle brown sugar solution at the same time every day, and gradually reduce the amount of brown sugar until the amount of brown sugar is reduced to 0 g on the 13th day.

[0043] Step (3) Acclimation of endogenous indigenous nitrifying and denitrifying bacteria: Before the nitrification system matures, feed is added to the aquaculture water at 70%~80% of the preset normal feeding amount. This reduces the rate of nitrite accumulation and shortens the time that nitrite levels remain high before the nitrification system matures. In addition, sodium bicarbonate is added to gradually increase the total alkalinity of the aquaculture water to above 250 mg / L, maintaining the pH value between 7.5 and 8.5. This replenishes the total alkalinity consumed by nitrifying bacteria, maintains pH stability, improves the aquatic animals' tolerance to nitrite, and provides good reproductive conditions for the acclimation of nitrifying bacteria. When both ammonia nitrogen and nitrite in the aquaculture water drop below 0.5 mg / L, it indicates that the nitrification system has matured.

[0044] After the nitrification system matures and nitrite stress is relieved, feed can be added to the aquaculture water at the preset normal feeding rate. From the start of nitrification system maturity, Bacillus subtilis is added at a concentration of 1 mg / L, and again every 4-6 days at a concentration of 1 mg / L, to promote the flocculation of organic particles in the aquaculture water and maintain the biofloc structure. Sodium bicarbonate is used to control the total alkalinity within the range of 150-200 mg / L, and the pH value is maintained between 7.0 and 8.0. An Inhofe conical tube and the biofloc collection device are used for dynamic monitoring and control of the biofloc concentration. The water flow velocity towards the biofloc deposition tube in the biofloc collection device is adjusted to control the biofloc concentration FV30 ≤ 15 ml / L. When nitrate drops below 0.5 mg / L, it indicates that the acclimatization of the endogenous indigenous nitrifying and denitrifying bacteria community is complete.

[0045] Optionally, in step (3), during the domestication stage of endogenous nitrifying and denitrifying bacteria, no additional organic carbon source is added except for the feed.

[0046] Optionally, the organic carbon source includes at least one of brown sugar, raw sugar, and molasses.

[0047] Optionally, the organic carbon source is a soluble organic carbon source that can be utilized by Bacillus.

[0048] Optionally, the biofloc concentration adjustment includes: collecting a uniform water sample from the middle layer of the aquaculture pond; pouring the water sample into an Inhofe conical tube to full volume (1000 ml); allowing it to stand for 30 minutes, avoiding vibration during this period; and reading the volume occupied by the settled flocs (mg / L), which is the FV30 value. The flow rate of water towards the biofloc collection device is adjusted using a ball valve on the drainage pipe, and the flow rate is controlled to be ≤0.5 m / s. 3 / h, the concentration of bioflocs is measured every 8 to 12 hours, and the biofloc removal rate is controlled within 20% on the same day.

[0049] Step (4) Dynamic maintenance of the aquaculture system: After the nitrification and denitrification system matures, if the farmed animals are shrimp, adjust the concentration of bioflocs FV30 in the aquaculture pond to 5~15 ml / L; if the farmed animals are fish, adjust the concentration of bioflocs FV30 in the aquaculture pond to 10~25 ml / L; maintain the floc structure by adding 1 mg / L of Bacillus to the aquaculture water every 4~6 days; use sodium bicarbonate to adjust the total alkalinity to 130~160 mg / L and maintain the pH value between 7.5~8.0; replenish the water lost in the aquaculture pond due to evaporation or removal of bioflocs every 3~5 days.

[0050] Optionally, the farmed animals are aquatic animals that can tolerate high concentrations of suspended particles and adapt to high-density farming environments.

[0051] Alternatively, the farmed animals may be Litopenaeus vannamei.

[0052] Optionally, embodiments of this application also provide the application of a method for establishing a nitrification-denitrification aquaculture system based on in-situ culture of bioflocs in Litopenaeus vannamei aquaculture.

[0053] Optionally, step (4) dynamic maintenance of the aquaculture system includes adjustment of biofloc concentration, adjustment of biofloc structure, adjustment of total alkalinity of aquaculture water and water replenishment.

[0054] Optionally, the biofloc structure regulation includes: continuing the operation of step (3), adding 1 mg / L of Bacillus to the aquaculture water every 5 days to maintain the floc structure.

[0055] Optionally, the total alkalinity of the aquaculture water is adjusted by controlling the total alkalinity at 130-160 mg / L and the pH value at 7.5-8.0.

[0056] Optionally, the water replenishment operation includes replenishing the water lost due to discharge from the biofloc collection device and evaporation every 4 days.

[0057] Alternatively, taking into account the nitrifying and denitrifying bacteria and the growth characteristics of farmed animals, the aquaculture system is operated within a certain water temperature range (22~33 ℃) and limited light intensity (≤50 lx).

[0058] In this embodiment, addressing the problems of long establishment time and incomplete nitrate nitrogen treatment in existing technologies, a technical solution is proposed to establish a nitrification-denitrification aquaculture system based on in-situ culture of bioflocs. By constructing the aquaculture system and cultivating bioflocs in situ, endogenous indigenous nitrifying and denitrifying bacteria are domesticated. Simultaneously, the aquaculture system is dynamically maintained. This system enables rapid establishment of the nitrification system during the aquaculture process and the removal of undigested nitrogen from feed and nitrogen from water (NH3). - -N, NO2 - -N, NO3 - The entire process of converting nitrogen (N-) through a single pathway is characterized by its simple structure, easy operation, and high efficiency in water treatment. It can be widely applied to the breeding of aquatic animals that can tolerate high concentrations of suspended particles and adapt to high-density aquaculture environments.

[0059] To make the objectives, technical solutions, and beneficial effects of this application clearer, the specific implementation methods provided in this application are further described in detail below with reference to specific embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents, instruments, and materials used, unless otherwise specified by manufacturer, are all commercially available conventional products.

[0060] Example 1 The aquaculture system operates inside the workshop. During operation, the water temperature is 26~32 ℃ and the salinity is 26~30. During the day, curtains are used to block out light, so that the light intensity is ≤40 lx.

[0061] (1) Construction of aquaculture system Two parallel, identical breeding ponds in the workshop were connected by a sewage pipe. Each breeding pond has an inner area of ​​24m². 2 (8 m × 3 m), pool depth 1.3 m, using a woven membrane as a guide wall, 6 m in length; centrifugal pump 1.5 kW; 8 water-pushing and aeration devices made using PVC pipe fittings (diameter ø25 mm), 4 in each aquaculture pool, distributed on both sides of the guide wall, spaced 4 m apart; PVC sewage outlet pipe diameter ø90 mm, main water pipe diameter ø50 mm; biofloc collection device with a volume of approximately 1 m³. 3 The biofloc collection device has a diversion pipe diameter of ø20 mm, a biofloc deposition pipe diameter of ø250 mm and a length of 400 mm, a return pipe diameter of ø50 mm, and a drain valve connection pipe diameter of ø32 mm. Each breeding pond is equipped with a feeding platform for observing the feeding of the animals.

[0062] (2) In situ culture of bioflocs Day 1: At 8:00 AM, the aquaculture pond was filled with water to a depth of 1 m. The centrifugal pump was turned on and the pond water was disinfected with 0.15 mg / L effective chlorine dioxide. At 3:00 PM, it was found that there was no disinfectant residue. The pre-prepared Bacillus activating solution (48 g Bacillus subtilis + 720 g brown sugar + 15 L pond water, aerated for 3 h) was poured in.

[0063] Days 2-7: On the morning of the second day, from 10:00 to 11:00, stock 7200 juvenile Pacific white shrimp (approximately 3 cm in length and 0.36 g in weight per shrimp, 300 shrimp per pond) per pond. 3 Feed #0 feed at 18 g / meal at 14:00 and 19:00. Starting from the third day, feed 4 meals / day (feeding times: 6:00, 10:30, 15:00 and 19:30), adjusting the feeding amount according to the feeding situation. At the same time, sprinkle brown sugar solution around 8:30 every morning, with the amount of brown sugar used that day being 4.0 times the weight of the feed.

[0064] Days 8 to 13: Feeding time is the same as above. Sprinkle brown sugar solution around 8:30 am every day, and gradually reduce the amount of brown sugar according to 30mg / L, 24mg / L, 18mg / L, 12mg / L, 6mg / L and 0mg / L, until the amount of brown sugar is reduced to 0 g on the 13th day.

[0065] (3) Domestication of endogenous indigenous nitrifying and denitrifying bacteria No organic carbon source is added at this stage. As nitrite levels increase, total alkalinity is gradually increased, reaching a peak of 330 mg / L at nitrite levels.

[0066] During this stage, no additional organic carbon sources will be added besides feed.

[0067] Before the nitrification system matures, feed at 70-80% of the normal feeding rate; gradually increase the total alkalinity to above 250 mg / L by adding sodium bicarbonate, maintaining the pH between 7.5 and 8.5. On day 41 of culture, the ammonia nitrogen in the culture water is 0.2 mg / L and the nitrite is 0.38 mg / L, indicating that the nitrification system has matured. The changes in the three nitrogen groups in the culture water are shown in the curves below. Figure 4 As shown. Before the nitration system matures, the ball valve in the drainage tube remains closed.

[0068] After the nitrification system matures, nitrite stress is relieved, and normal feeding can resume. From the start of nitrification system maturity, Bacillus subtilis is added at a concentration of 1 mg / L, and this concentration is repeated every 5 days. This is to promote the flocculation of organic particles in the aquaculture water and maintain the biofloc structure. The total alkalinity is controlled using sodium bicarbonate within the range of 150–200 mg / L, and the pH is maintained between 7.2 and 7.9. The concentration of bioflocs is dynamically monitored and controlled using an Inhofe conical tube and the aforementioned biofloc collection device. The water flow velocity towards the biofloc deposition tube is adjusted to ≤0.5 m / s as needed. 3 / h, the concentration of bioflocs FV30 was adjusted to ≤15 ml / L. On day 47 of culture, the nitrate level in the culture water was 0.15 mg / L, marking the completion of the acclimatization of the endogenous indigenous nitrifying and denitrifying bacteria. The nitrogen content changes in the culture water are shown in the curves below. Figure 4 As shown.

[0069] (4) Dynamic maintenance of the reproductive system After the nitrification and denitrification system matures, the concentration of bioflocs (FV30) in shrimp farming is controlled within the range of 10-15 ml / L. The floc structure is maintained by adding 1 mg / L of Bacillus to the farming water every 5 days. The total alkalinity is controlled within the range of 130-160 mg / L using sodium bicarbonate, and the pH value is maintained between 7.5 and 8.0. The water lost due to evaporation or removal of bioflocs is replenished every 4 days.

[0070] During the rearing period, adjust the feed amount every 2-3 days, with an adjustment range of 5%-10%. The adjustment range depends on the length of time the shrimp spends eating before the adjustment; if the shrimp finishes eating very quickly, the adjustment range can be larger; conversely, the adjustment range should be smaller. If the shrimp eats more slowly, reduce the number of feedings, the amount of feed, or both. Select feed with appropriate particle size and a suitable daily ration ratio based on the size of the shrimp. During the peak molting period (2-3 days before or after the first and fifteenth of the lunar month) or when a large number of shrimp are observed molting, actively reduce the feed by about 20% and supplement with calcium, magnesium, potassium, and other elements as needed. The changes in nitrogen levels in the water during the rearing period are detailed in [link to relevant documentation]. Figure 4 The breeding results are shown in Table 1.

[0071] Table 1

[0072] The embodiments described above are merely preferred embodiments of this application and are not intended to limit the scope of this application. Any equivalent substitutions or improvements made based on the description and drawings of this application, or direct / indirect applications in other related technical fields, without departing from the spirit of this application, shall fall within the protection scope defined by the claims of this application.

Claims

1. A method for establishing a nitrification-denitrification aquaculture system based on in-situ culture of bioflocs, characterized in that, The method includes: Step (1) Construction of the aquaculture system: The aquaculture system includes: aquaculture pond, centrifugal pump, water pushing and oxygenation device, biofloc collection device and plastic pipe fittings; Step (2) In-situ culture of bioflocs: The aquaculture water in the aquaculture pond is filtered and disinfected. After testing and confirming that there is no disinfectant residue, Bacillus activating solution is added. On the day after the addition of the Bacillus activating solution, the aquaculture animals and feed are added to the aquaculture pond. At fixed times for 12 to 14 consecutive days, organic carbon source is added to the aquaculture pond. During the in-situ culture of bioflocs, if the pH value of the aquaculture water is <7.0 and / or the total alkalinity is <100 mg / L, sodium bicarbonate is used for adjustment. Step (3) Acclimation of endogenous native nitrifying and denitrifying bacteria: Before the nitrification system matures, feed is added to the aquaculture water at 70% to 80% of the preset normal feeding amount, and sodium bicarbonate is added to increase the total alkalinity of the aquaculture water to above 250 mg / L, and the pH value is maintained at 7.5 to 8.

5. After the nitrification system matures, feed is added to the aquaculture water according to the preset normal feeding amount, and Bacillus is added every 4 to 6 days at a concentration of 1 mg / L. Sodium bicarbonate is used to control the total alkalinity in the range of 150 to 200 mg / L and the pH value is maintained at 7.0 to 8.

0. The concentration of biofloc is dynamically monitored and controlled using an Inhofe conical tube and the biofloc collection device. The water flow velocity flowing to the biofloc deposition tube in the biofloc collection device is adjusted to control the biofloc concentration FV30 ≤ 15 ml / L until the nitrification-denitrification system matures. Step (4) Dynamic maintenance of the aquaculture system: After the nitrification and denitrification system matures, if the farmed animal is shrimp, the concentration of bioflocs FV30 in the aquaculture pond is adjusted to 5~15 ml / L; if the farmed animal is fish, the concentration of bioflocs FV30 in the aquaculture pond is adjusted to 10~25 ml / L; the floc structure is maintained by adding 1 mg / L of Bacillus to the aquaculture water every 4~6 days; the total alkalinity of the aquaculture water is adjusted to 130~160 mg / L and the pH value is maintained at 7.5~8.0 using sodium bicarbonate; the water loss in the aquaculture pond is replenished every 3~5 days.

2. The method as described in claim 1, characterized in that, The water temperature in the breeding pond is controlled at 22~33 ℃, and the light intensity is ≤50 lx.

3. The method as described in claim 1, characterized in that, In step (2), the organic carbon source includes at least one of brown sugar, raw sugar, and molasses.

4. The method as described in claim 1, characterized in that, In step (2), the feeding time of the farmed animals is 2 hours after the farmed animals are put into the breeding pond.

5. The method as described in claim 1, characterized in that, In step (2), the method of delivering the organic carbon source includes: Starting from the day of feeding, the organic carbon source is added to the aquaculture pond at a fixed time and in a preset ratio for 5 to 7 consecutive days, and the ratio between the daily addition of the organic carbon source and the daily addition of the feed is ≥3.

0. Then, the addition of the organic carbon source is gradually reduced until it drops to 0 g on the 12th to 14th day.

6. The method as described in claim 1, characterized in that, In step (3), the maturity of the nitrification system is indicated by the ammonia nitrogen and nitrite in the aquaculture water of the aquaculture pond both dropping to below 0.5 mg / L, and the maturity of the nitrification-denitrification system is indicated by the nitrate in the aquaculture water of the aquaculture pond dropping to below 0.5 mg / L.

7. The method as described in claim 1, characterized in that, In step (3), the water flow velocity is ≤0.5 m. 3 / h.

8. A breeding system, characterized in that, The aquaculture system is applied to the method for establishing a nitrification-denitrification aquaculture system based on in-situ culture of bioflocs as described in any one of claims 1 to 7. The aquaculture system includes: an aquaculture pond, a centrifugal pump, a water-pushing and oxygenating device, a biofloc collection device, and plastic pipe fittings.

9. The aquaculture system as described in claim 8, characterized in that, The length-to-width ratio of the aquaculture pond is ≥2.5, the inner corners are set with inner rounded corners, and a flow guide wall is provided in the middle area; The water-pushing and oxygenating device is based on the Venturi effect, is made of plastic pipes, and is fixed to the bottom of the aquaculture pond along the water flow direction in the aquaculture system, with intervals of 3-5 m between each other. The volume of the biofloc collection device accounts for ≥1% of the aquaculture water in the aquaculture pond, and the cone angle of its conical part is 60°~120°.

10. The aquaculture system as described in claim 9, characterized in that, The diversion wall includes at least one of the following: a wall, a baffle, a geomembrane, and a woven membrane.

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