Efficient recirculating aquaculture system and method constructed by using granular zoogloea

Abstract

The invention discloses an efficient recirculating aquaculture system and method constructed by using granular zoogloea, and belongs to the technical field of freshwater aquaculture wastewater treatment. The high-efficiency circulating water culture system comprises aquaculture equipment, a circulating water tank and a circulating water tank, wherein the aquaculture equipment comprises a culture barrel; the nitrification and denitrification equipment comprises a reactor and an activated sludge unit, and the activated sludge unit is located in the reactor; the oxygen increasing equipment comprises an oxygen increasing machine; wherein the bottom of the aquaculture equipment is in pipeline communication with the bottom of the reactor through a water pump; the top of the aquaculture equipment is communicated with the reactor through a pipeline provided with an electromagnetic valve; then, the system is utilized, and water feeding, aerobic aeration, standing, anaerobic reaction and drainage are used as a complete operation cycle for recirculating aquaculture. By means of the circulating water culture system and method, the concentration of ammonia nitrogen, nitrite and nitrate difficult to remove in the aquaculture circulating water system can be effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of freshwater aquaculture wastewater treatment, and in particular relates to a high-efficiency circulating water aquaculture system and method using granular bacterial flocs. Background Art

[0002] In recent years, Zoogloea has received great attention as a new type of environmental biotechnology. In the field of sewage treatment, this technology quickly selects microbial aggregates with faster sedimentation speed through a short sedimentation time, promoting the formation of dense aggregates in activated sludge. Solid-liquid separation is achieved by gravity sedimentation in the same reactor, making mud-water separation more efficient without the need for additional filtration steps. This not only significantly reduces the land area of ​​the sewage treatment plant, but also eliminates the traditional secondary sedimentation tank, which has a significant land-saving advantage.

[0003] During the sewage treatment process, the microorganisms in the activated sludge rely on the oxygen provided by the aeration system to quickly degrade or transform pollutants dissolved in the sewage. This method allows the microorganisms to utilize the pollutants, thereby achieving rapid and efficient sewage purification. Compared with the natural purification process that takes 4 to 6 weeks to complete in nature, the same purification task can be completed in a sewage treatment plant with the help of granular bacterial flocs in just 4 to 6 hours. This significant time reduction greatly improves the efficiency of sewage treatment.

[0004] A large number of studies have been conducted on high-concentration, high carbon-nitrogen ratio wastewater (chemical oxygen demand COD up to 1400 mg·L -1 The granular bacterial floccules were successfully cultivated under the conditions of low carbon nitrogen ratio (COD about 500mg·L) and C / N ratio up to 10-20, which enriched the understanding of the formation process, characteristics and performance of sludge granulation. -1 Attempts have been made to cultivate and operate granular bacterial flocs under conditions of low carbon dioxide (C / N ratio of about 5-10). For example, at the Garmerwolde wastewater plant in the Netherlands, a sequencing batch reactor (SBR) model was used to process domestic sewage (with an average influent COD of 506 mg·L -1 , the average influent C / N ratio was 7-9) and the proportion of sludge with particle size larger than 0.2 mm exceeded 80%; when the influent COD was 390 mg·L -1Under the conditions of 1.5-2.0% COD / L and 8.6-23.5 mgN / L (domestic sewage), SBR can cultivate granular bacterial flocs with a particle size of 0.63-1.6 mm. However, the pollutant concentration and carbon-nitrogen ratio in freshwater aquaculture wastewater are much lower (7.5-35.5 mgCOD / L and 8.6-23.5 mgN / L, C / N ratio is 1-4). At present, there are still few studies on the successful cultivation of granular bacterial flocs in SBR in low carbon-nitrogen ratio sewage, especially in aquaculture circulating water, and there is a lack of unified understanding of the formation characteristics, microbial community structure and function of granular bacterial flocs. For example, at present, the sewage used for the successful cultivation of granular bacterial flocs in sequencing batch reactors (SBRs) is mainly domestic and industrial wastewater, which usually has a high carbon-nitrogen ratio (C / N>10). The inoculum microorganisms used are mainly derived from activated sludge in sewage treatment or domesticated human feces. However, when traditional activated sludge is used for inoculation to treat aquaculture wastewater, the content of low-load (COD <150 mg / L, total nitrogen <10 mg / L) resistant microorganisms in traditional activated sludge is low due to the low load (<150 mg / L) and low carbon-nitrogen ratio (C / N) (1-4) of aquaculture wastewater. Using it as inoculated sludge to cultivate granular bacterial flocs will result in a long start-up period, low relative abundance of low-load resistant microorganisms, and poor impact resistance of sludge particles. Therefore, it is of great significance to study the characteristics of granular bacterial flocs cultivated under low carbon-nitrogen ratio sewage conditions. This research direction has particularly important application prospects for the treatment of aquaculture wastewater.

[0005] Biofloc technology (BFT) is also a research hotspot in recent years. The key points of the technology are to add carbon sources to the aquaculture water, adjust the carbon-nitrogen ratio of the aquaculture water, and fully utilize the assimilation of heterotrophic microorganisms in situ to achieve the purpose of removing inorganic nitrogen (ammonia nitrogen, nitrite nitrogen, nitrate nitrogen) from the aquaculture water. In this process, substances such as feces, food residues and organic debris will flocculate to form particulate matter, which can be ingested by aquaculture organisms, thereby realizing the secondary utilization of protein and ultimately achieving the purpose of regulating water quality. However, the current biofloc technology has several disadvantages. First, the technology requires extremely precise control of the carbon-nitrogen ratio, which poses a great challenge to management. If the carbon source is not added properly, it is easy to cause an imbalance in the microbial community, which will have an adverse effect on water quality. In addition, the long-term addition of carbon sources not only complicates the operation process, but also significantly increases the cost of aquaculture. Therefore, biofloc technology faces problems such as complex management and high cost in practical applications, which limit its promotion and application in large-scale aquaculture. This also shows that developing a more efficient, lower-cost and easier-to-manage method for cultivating microbial aggregates has important practical significance.

[0006] Recirculating Aquaculture System (RAS) is an efficient aquaculture method that reduces water resource consumption and environmental pollution by reusing and filtering water. Its core principle is to return the aquaculture water to the aquaculture pond for use after a series of treatment steps, such as solid filtration, biological filtration, ultraviolet disinfection and oxygen supplementation. And because the water quality is easy to control, high-density aquaculture can be achieved to increase production. However, if a complete recirculating aquaculture system is currently built, more complex equipment and infrastructure, such as filtration systems, oxygenation equipment, heating or cooling devices, etc., are required, so the initial construction cost is high. Secondly, due to the need to maintain stable water quality, there are many devices that need to be continuously operated in the system, including pumps, filters, disinfection equipment, etc., resulting in high energy consumption and maintenance costs. In addition, RAS has strict requirements on water quality control and management, and requires professional operating skills and knowledge. Farmers must have rich experience in water quality management. At the same time, equipment maintenance is complex, and the system's filters, biological filters, oxygenation equipment, etc. need to be cleaned and maintained regularly. The maintenance cost is high and if the equipment fails, it may affect the operation of the entire aquaculture system. Finally, there is a biosafety risk. As water circulates in the system, pathogens may spread rapidly in the system. If the pathogens are not eliminated in time, they may cause serious diseases. Therefore, the system requires strict disinfection and disease prevention and control measures.

[0007] In summary, in aquaculture circulating water systems, since the concentrations of toxic substances (such as ammonium and nitrite) in aquaculture wastewater are low, how to efficiently remove these pollutants is crucial to maintaining the health and sustainable development of fish production. Therefore, it is urgent to provide an efficient circulating water aquaculture system and method that can effectively reduce the concentrations of toxic ammonium, nitrite and difficult-to-remove nitrate in aquaculture. Summary of the invention

[0008] In view of the above technical problems, the present invention proposes a system and method for constructing a high-efficiency circulating water aquaculture system using granular bacterial flocs.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] One of the technical solutions of the present invention:

[0011] A highly efficient circulating water aquaculture system using granular bacterial flocs, comprising:

[0012] Aquaculture equipment, including aquaculture drums;

[0013] The nitrification and denitrification equipment comprises a reactor and an activated sludge unit, wherein the activated sludge unit is located inside the reactor; the activated sludge unit is a granular bacterial floc;

[0014] Aeration equipment, including aerators and microporous aeration systems;

[0015] Wherein, the bottom of the aquaculture equipment is connected to the bottom of the reactor through a pipeline via a water pump;

[0016] The top of the aquaculture equipment is connected to the reactor via a pipeline provided with a solenoid valve.

[0017] Beneficial effects: The present invention not only simplifies the equipment and infrastructure of the recirculating aquaculture system (only an aerator, a sequencing batch reactor, and aquaculture barrels are required), but also reduces the operating cost; after the granular bacterial flocs are successfully domesticated, the effluent water quality is stable and no additional management and regulation is required; the equipment maintenance is efficient and does not require disinfection, only simple cleaning and wiping; in addition, since only the sediments of the cultured species are used to cultivate the granular bacterial flocs and there is no injection of external water bodies, the entire recirculating aquaculture system has basically no risk of invasion by pathogenic bacteria.

[0018] Preferably, the type of fish cultured in the culture barrel is grass carp.

[0019] Preferably, the height-to-diameter ratio of the reactor is >4.

[0020] Preferably, an agitator is provided inside the reactor to ensure good mixing and shearing force in the reactor.

[0021] Furthermore, the reactor is provided with a timing controller to precisely control the reaction process.

[0022] Preferably, a microporous aeration system is provided at the bottom layer inside the reactor, wherein the microporous aeration system comprises a microporous aeration head, and an aerator aerates the reactor through the microporous aeration head.

[0023] The second technical solution of the present invention:

[0024] A method for constructing an efficient circulating water aquaculture system using granular bacterial flocs, using the above-mentioned efficient circulating water aquaculture system, with 15 minutes of water intake and anaerobic reaction, 180 minutes of aerobic aeration (gas flow rate is 1NL / min), 30 minutes of standing and anaerobic reaction, and 15 minutes of drainage as a complete operation cycle, the operation process includes the following steps:

[0025] (1) Use a water pump to allow the aquaculture wastewater at the bottom of the aquaculture equipment to enter the reactor and undergo an anaerobic reaction with the granular bacterial flocs inside the reactor;

[0026] (2) using an aerator to aerate the reactor through a microporous aeration head, so that the aquaculture wastewater and the granular bacterial flocs are aerobically aerated;

[0027] (3) Standing and anaerobic reaction;

[0028] (4) Use a solenoid valve to discharge the water in the reactor into the aquaculture equipment so that the volume exchange rate of the reactor reaches 50%.

[0029] Beneficial effects: In the breeding drum, fish take in a large amount of feed and excrete a large amount of excrement every day, and some of the uneaten feed will sink to the bottom and become residue. These two types of pollutants will continue to accumulate in the water body, generating ammonia nitrogen and nitrite that are toxic to fish. To solve this problem, the present invention treats the breeding wastewater at the bottom of the breeding drum by self-cultivated flocs (activated sludge units). Aerobic aeration and stirring for 180 minutes per cycle fully mixes the flocs with the wastewater, and uses the insoluble carbon sources in the excrement and feed residues and some soluble carbon sources dissolved in the water body as nutrients to remove ammonia nitrogen and nitrite in the water body through nitrification. Subsequently, during the water intake and anaerobic reaction stages of 15 minutes per cycle, the flocs use the newly entered carbon source to carry out denitrification, thereby effectively removing nitrates from the water.

[0030] Preferably, during the high-efficiency circulating aquaculture method, six operation cycles are performed every day.

[0031] Preferably, during operation, the sludge retention time (SRT) of the granular flocs is 30 days, and 1 / 30 of the total flocs are discharged into the culture barrel every day.

[0032] Preferably, in the initial stage of operation, a carbon source (glucose) is added to the breeding barrel until the carbon-nitrogen ratio in the breeding barrel is >6, COD>400, and TN>60, and then the addition is stopped.

[0033] Preferably, the preparation process of the granular bacterial micelle is:

[0034] The aquaculture wastewater at the bottom of the aquaculture equipment is introduced into the sequencing batch reactor (SBR) through a water pump, and then subjected to aeration and static sedimentation in sequence, and then introduced again, which is regarded as a complete introduction cycle, until the sludge concentration in the reactor exceeds 1g / L, and the sludge sedimentation ratio of the mixed liquid reaches 15% to 20%, and the aeration is stopped; granular bacterial flocs are obtained in the reactor;

[0035] Among them, in the second and subsequent introduction cycles, nutrient solution needs to be added during the process of introducing aquaculture wastewater.

[0036] Beneficial effects: The present invention improves the success rate of culturing granular bacterial flocs by domesticating specific bacterial species (sediments of specific aquatic products, grass carp) to adapt them to the aquaculture wastewater environment with low load and low carbon-nitrogen ratio.

[0037] Furthermore, during the exposure process, the stirring rate of the stirrer in the reactor was 50 rpm; and the gas (oxygen) flow rate was 2 NL / min.

[0038] Beneficial effects: The stirring force and gas flow rate of the electromagnetic stirrer in the reactor have a great influence on the formation and activity of bacterial flocs. By adjusting the force and flow rate, the particle size and structure of sludge particles can be controlled, thereby improving the formation efficiency and treatment capacity of bacterial flocs.

[0039] Furthermore, the exposure time is 2-3 days, and the static sedimentation time is 1-1.5 hours.

[0040] Furthermore, the nutrient solution includes the following raw materials: 857 mg / L glucose, 44.6 mg / L ammonium sulfate, 3.6 mg / L potassium dihydrogen phosphate, 10 mg / L magnesium sulfate, 10 mg / L ferrous sulfate and 10 mg / L calcium chloride.

[0041] Furthermore, the amount of water introduced into the process in each cycle increases by 1-2L compared with the previous cycle until it reaches 90% of the effective volume of the reactor; the exposure time in each cycle is shortened by 12h compared with the previous cycle.

[0042] Preferably, during operation, the operating temperature of the reactor is 20-25° C., the dissolved oxygen concentration in the reactor is 3-5 mg / L, and the rotation speed of the agitator in the reactor is always 50 rpm.

[0043] Beneficial effects: In sludge culture, the level of dissolved oxygen plays a key role in the growth of microorganisms and the effect of wastewater treatment. Properly controlling the internal pressure of the reactor through the concentration of dissolved oxygen helps to maintain an appropriate dissolved oxygen level and ensure the removal efficiency of organic matter and nitrogen and phosphorus.

[0044] Compared with the prior art, the present invention has the following advantages and technical effects:

[0045] 1. Targeted improvements: The present invention combines the characteristics of specific aquaculture species and aquaculture wastewater, and makes targeted improvements through the domestication of bacterial sources, the construction of reactors, and the control pressure of sludge culture. These improvements effectively solve the problem of successfully culturing granular bacterial flocs from aquaculture wastewater under low load and low carbon-nitrogen ratio conditions.

[0046] 2. Self-circulating aquaculture model: Based on the water quality requirements of the aquaculture target objects during the aquaculture process, as well as the changes in the sewage load and nutrient salt ratio generated at different growth stages, the present invention constructs a self-circulating aquaculture water model combining biofloc and activated sludge reactor. This model not only improves the utilization efficiency of water resources and protein, but also effectively reduces the impact of wastewater discharge on the environment.

[0047] 3. Efficient sludge cultivation: By optimizing the control pressure of sludge cultivation, the present invention can successfully cultivate highly active granular bacterial flocs under low load and low carbon-nitrogen ratio conditions. This efficient bacterial floc cultivation technology significantly improves the effect and efficiency of wastewater treatment.

[0048] 4. Improved comprehensive benefits: The improvements in the present invention in terms of bacterial strain domestication, reactor construction, sludge culture and ex situ culture with in situ placement of granular bacterial flocs not only improve the efficiency of wastewater treatment, but also reduce operating costs, with significant economic and environmental benefits.

[0049] In summary, the present invention adopts a sequencing batch reactor and uses the sediment of a specific aquaculture species as an inoculum to cultivate granular bacterial flocs for treating low-load fishery aquaculture circulating water. Compared with traditional activated sludge, it has significant advantages in the floc formation process, physical and chemical properties and water treatment performance. It solves the problems of increased cost and increased difficulty in regulation caused by the addition of carbon sources. That is, the present invention cultivates granular bacterial flocs by ex situ cultivation and in situ delivery, and accurately controls the carbon-nitrogen ratio by feeding fish, so that inorganic nitrogen in the aquaculture water, protein in particulate matter, soluble carbon sources, and insoluble carbon sources in fish excrement are efficiently utilized.

[0050] In addition, the above-mentioned circulating water aquaculture system and method defined in the present invention can form a microbial population and related functional structures with high abundance, strong impact resistance and good tail water decontamination effect. At the same time, the cultivation method of activated sludge bacteria and the reactor control process in the process of granular bacterial floc formation are improved and innovated. This innovation not only improves the efficiency and effect of aquaculture wastewater treatment, but also provides new ideas and technical support for low-load sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0052] Figure 1 This is a structural diagram of a circulating aquaculture system in Example 1 of the present invention;

[0053] Among them, 1. agitator, 2. manual ball valve, 3. first solenoid valve, 4. second solenoid valve, 5. third solenoid valve, 6. first water pump, 7. second water pump, 8. breeding barrel, 9. reactor, 10. polypropylene cylinder with perforated tray, 11. activated carbon filler, 12. sewage outlet, 13. portable filter, 14. first aerator, 15. second aerator, 16. third aerator, 17. check valve, 18. microporous aeration head;

[0054] Figure 2This is a diagram showing the fluctuation trend and removal efficiency of ammonia nitrogen in the reactor of the circulating aquaculture system of Example 1 of the present invention after 171 days of operation;

[0055] Figure 3 This is a diagram showing the fluctuation trend and removal rate of nitrite in the reactor of the circulating aquaculture system of Example 1 of the present invention after 171 days of operation;

[0056] Figure 4 This is a diagram showing the fluctuation trend and removal rate of nitrate in the reactor of the circulating aquaculture system of Example 1 of the present invention after 171 days of operation;

[0057] Figure 5 This is a C / N variation trend curve diagram in the reactor of the recirculating aquaculture system of Example 1 of the present invention after running for 171 days;

[0058] Figure 6 This is an electron microscope scanning image of the granular bacterial micelle in the reactor;

[0059] Figure 7 The pictures are of granular bacterial flocs in the reactor (left), the structure of aerobic granular sludge (middle) and the microscope picture (right);

[0060] Figure 8 It is a bar chart of the Alpha diversity index of the floc particles. DETAILED DESCRIPTION

[0061] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0062] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0063] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0064] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0065] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0066] The present invention discloses a method for constructing efficient circulating aquaculture using granular bacterial flocs, comprising the following steps:

[0067] (1) The selected aquatic animals are placed in breeding barrels to adapt to the breeding conditions; during the breeding process, the water quality parameters are strictly controlled to ensure the healthy growth of the aquatic animals;

[0068] (2) Cultivation of granular bacterial flocs: 6L of aquaculture wastewater at the bottom of the aquaculture drum in step (1) is introduced into a sequencing batch reactor (SBR), and subjected to 2-3 days of aeration (aeration only without the introduction of water) and 1-1.5 hours of static sedimentation, and then introduced again to promote the formation of bacterial flocs and the sedimentation of sludge; this is considered a complete introduction cycle, and the aeration is stopped until the sludge concentration in the reactor exceeds 1g / L and the sludge sedimentation ratio of the mixed solution reaches 15% to 20%;

[0069] Among them, in the second and subsequent introduction cycles, nutrient solution is added during the introduction of aquaculture wastewater to provide the required carbon source, nitrogen source and other essential nutrients for microbial growth, so as to promote the formation and activity of granular bacterial flocs;

[0070] (3) The recirculating aquaculture is carried out with 15 minutes of water intake, 180 minutes of aerobic aeration, 30 minutes of static and anaerobic reaction, and 15 minutes of drainage as a complete operation cycle. The specific steps are as follows:

[0071] ① Pump the aquaculture wastewater into the reactor from the bottom of the aquaculture barrel in a plug flow manner (i.e., pump the water from the aquaculture barrel into the reactor through a water pump) to complete the water intake;

[0072] ② Aerobic aeration, during which the aerator aerates the bottom of the reactor through the microporous aeration head and stirs it through the agitator to ensure good mixing and shear force in the reactor;

[0073] ③Standing and anaerobic reaction;

[0074] ④ Drain water so that the volume exchange rate of the reactor reaches 50%.

[0075] (4) After the water quality discharged in step (3) is stabilized, the pH value in the reactor and the culture barrel is adjusted to maintain it above 7.3 to provide sufficient alkalinity for denitrification. At this time, granular bacterial flocs integrating nitrification and denitrification are also cultivated.

[0076] In some preferred embodiments, in step (3), glucose is added to the breeding barrel as a carbon source at the early stage of system operation, and when the carbon-nitrogen ratio in the breeding barrel exceeds 6, COD>400, and TN>60, the addition of carbon source is stopped.

[0077] In summary, in the initial stage of the operation of the reactor, the present invention adjusts the COD level by adding a small amount of carbon source, and adjusts the frequency of aeration and water inlet according to the sludge concentration and sedimentation ratio. Subsequently, the reactor enters the stable operation stage, stops adding carbon source, adapts the granular bacterial flocs to the aquaculture water body, and domesticates them to use the excrement of aquatic animals and the soluble carbon source in the aquaculture water body as food for assimilation. And multiple operation cycles are carried out every day, each cycle includes continuous stages such as water inlet, aerobic aeration, standing, anaerobic reaction, and drainage; during the entire operation period, a specific sludge retention time (SRT) is maintained, a portion of the granular bacterial flocs are discharged into the aquaculture barrel, and the pH value and dissolved oxygen concentration are monitored to ensure the effective operation of the system.

[0078] In some preferred embodiments, in step (2), the height-to-diameter ratio of the sequencing batch reactor is greater than 4; the sequencing batch reactor is provided with a timing controller, and the reaction process is precisely controlled by the timing controller.

[0079] In some preferred embodiments, in step (2), the nutrient solution includes the following raw materials: 857 mg / L glucose, 44.6 mg / L ammonium sulfate, 3.6 mg / L potassium dihydrogen phosphate, 10 mg / L magnesium sulfate, 10 mg / L ferrous sulfate and 10 mg / L calcium chloride.

[0080] In some preferred embodiments, in step (2), the water inlet volume introduced into the process in each cycle is increased by 1-2 L compared with the water inlet volume in the previous cycle until it reaches 90% of the effective volume of the reactor; and the exposure time in each cycle is shortened by 12 h compared with the previous cycle.

[0081] In some preferred embodiments, the stable water quality in step (4) is characterized by obvious nitrification of the effluent, that is, toxic ammonium and nitrite are removed in large quantities, and nitrate begins to accumulate.

[0082] The "room temperature" in the present invention refers to 20-30°C unless otherwise specified.

[0083] The "parts" described in the present invention, unless otherwise specified, refer to parts by mass.

[0084] The raw materials used in the present invention are all purchased from the market.

[0085] The technical solution of the present invention is further illustrated by the following embodiments.

[0086] Example 1

[0087] like Figure 1 As shown, a highly efficient circulating water aquaculture system using granular bacterial flocs is constructed, comprising:

[0088] Aquaculture equipment, including aquaculture drums 8;

[0089] The nitrification and denitrification equipment comprises a reactor 9 and an activated sludge unit (granular bacterial flocs), wherein the activated sludge unit is located inside the reactor 9;

[0090] Aeration equipment, including aerators and microporous aeration systems;

[0091] Specifically:

[0092] The second aerator 15 and the third aerator 16 are provided on the left and right sides of the culture drum 8, and a counterclockwise (such as Figure 1 The vortex (indicated by the arrow in the middle) performs gravity screening on large particles such as feces and food residues in the breeding barrel 8, and some heavy waste is discharged from the sewage outlet 12 provided at the bottom of the breeding barrel 8;

[0093] The bottom of the breeding drum 8 is connected to the bottom of the reactor 9 through a first water pump 6, and a second solenoid valve 4 is installed to prevent backflow. A portable filter 13 is installed at the bottom of the reactor 9. The top of the breeding drum 8 is connected to the top of the reactor 9 through a first solenoid valve 3, thereby forming a circulating water breeding system.

[0094] The reactor 9 has a height-to-diameter ratio of >4; and a stirrer 1 is provided inside the reactor to ensure good mixing and shearing force in the reactor;

[0095] A microporous aeration head 18 is provided at the bottom of the reactor 9, and aeration is carried out into the reactor 9 through the first aerator 14. A check valve 17 is provided between the first aerator 14 and the microporous aeration head 18 to prevent backflow of the reactor 9 when it is stationary.

[0096] A manual ball valve 2 is provided on the top of the reactor to prevent the first solenoid valve 3 of the reactor from being blocked, resulting in excessive water inflow. An overflow port is provided to facilitate manual drainage;

[0097] A polypropylene cylinder 10 with a perforated tray is arranged in the middle layer inside the reactor 9, and a screen is arranged on the polypropylene cylinder with a perforated tray. An activated carbon filler 11 is loaded on the upper layer of the screen, and its function is to adsorb large-particle bacterial flocs; the direction indicated by the arrow is the direction of water flow, and the water flow is driven to fully pass through the activated carbon filler 11 under the dual effects of the microporous aeration head 18 and the agitator 1.

[0098] A portable filter screen 13 with a mesh size of 28 is provided at the bottom of the reactor 9. Its function is to intercept larger particles of bacterial flocs and discharge smaller particles of bacterial flocs during sludge discharge. The third solenoid valve 5 is connected to the second water pump 7 at the bottom of the reactor 9. The third solenoid valve 5 and the second water pump 7 are controlled by a timing controller to discharge sludge, thereby controlling the sludge age of the bacterial flocs in the reactor 9.

[0099] Example 2

[0100] The circulating aquaculture method using the circulating aquaculture system in Example 1 comprises the following steps:

[0101] The grass carp used in this embodiment comes from the grass carp breeding pond of the Pearl River Fisheries Research Institute. The grass carp was placed in a breeding drum (300L) in the ecological breeding room of the Pearl River Fisheries Research Institute for temporary breeding for 1 week. During this period, the commercial feed of Guangdong Tongwei Co., Ltd. was fed to adapt the fish to the breeding environment. Before the breeding experiment began, 110 grass carps of uniform size (average weight 0.253kg) and healthy were selected for the experiment. Feed once at 8:30 and 18:30 every day, 100g each time, and the water temperature was recorded regularly. The water temperature was controlled at 20-25°C during the breeding period, and the dissolved oxygen concentration was 4-5mg / L.

[0102] The granular bacterial flocs were cultured in a sequencing batch reactor (SBR), which was made of plexiglass, had a height-to-diameter ratio of 4.5, and an effective volume of 30.774 L. The operation of the SBR was controlled by a timing controller to control the reaction process.

[0103] This embodiment adopts intermittent culture to cultivate the granular bacterial micelles in the reactor, and the specific steps are as follows:

[0104] First, the aquaculture wastewater (containing a large amount of sediment, fish feces, bait residues, etc., about 6L) at the bottom of the aquaculture barrel is introduced into the reactor, and the water supply is stopped. The aeration is started (only aeration without water supply, and the oxygen flow rate during the aeration process is 2NL / min). After 2-3 days of aeration, aeration is stopped and the reactor is allowed to settle for 1-1.5 hours.

[0105] Then, the aquaculture wastewater at the bottom of the aquaculture barrel is introduced again (the water volume accounts for about 1 / 5 of the effective volume of the reactor, about 6L), and then the nutrient solution is added for the second and subsequent introduction of aquaculture wastewater. The addition amount is 857mg of glucose, 44.6mg of ammonium sulfate, 3.6mg of potassium dihydrogen phosphate, 10mg of magnesium sulfate, 10mg of ferrous sulfate and 10mg of calcium chloride per liter of wastewater, which can provide the carbon source, nitrogen source and other essential nutrients required for microbial growth to promote the formation and activity of granular bacterial flocs. After that, the three processes of venting, settling and water inlet are repeated, but the water inlet volume each time is increased compared with the last time (about 1-2L, until it reaches 90% of the effective volume of the reactor), and the venting time each time is shortened by 12h compared with the last time.

[0106] When the sewage temperature in the reactor is 15-20℃, after about 15 days, the sludge concentration in the reactor can exceed 1g / L, and the sludge settling ratio of the mixed liquid reaches 15% to 20%. At this time, the aeration can be stopped and the whole system can be connected to each breeding barrel to operate.

[0107] In the early stage of system operation, COD was low, and glucose was added as a carbon source; when the carbon-nitrogen ratio in the sampling and detection of the culture barrel exceeded 6, COD>400, and TN>60, the carbon source was stopped, and the bacterial flocs were domesticated to adapt to the culture water body, so that they could use the fish feces and bait residues in the wastewater at the bottom of the culture barrel as carbon sources for growth and reproduction. The reactor runs 6 cycles a day, and each cycle includes four consecutive stages: ①15min water inlet (wastewater at the bottom of the culture barrel), during which the culture wastewater is pumped into the reactor from the bottom in a plug flow manner; ②180min aerobic aeration, during which the aerator aerates through the bottom of the reactor (gas flow rate is 1NL / min) and stirs through the stirrer (stirring speed is 50rpm) to ensure good mixing and shear force in the reactor; ③30min standing and anaerobic reaction; ④15min drainage. In one cycle, the volume exchange rate of the reactor reaches 50%. During the operation, the sludge retention time (SRT) of the floccules is 30 days, and 1 / 30 of the floccules in the reactor are discharged into the culture barrel every day. The dissolved oxygen concentration in the reactor is monitored to be 3-5 mg / L; the reactor is operated at room temperature (20-25°C). When the discharged water quality is stable, the pH value in the reactor and the culture barrel is adjusted to maintain it above 7.3, providing sufficient alkalinity for denitrification, and at this time, granular floccules integrating nitrification and denitrification are also cultivated.

[0108] Figure 2The fluctuation trend and removal rate effect diagram of ammonia nitrogen in the reactor of Example 1 after the system was operated for 171 days; wherein, C (RE) is the removal rate, C1 is the reactor inlet water, and C2 is the reactor outlet water (the same below); it can be seen from the figure that in the initial stage, the reactor immediately showed its significant ammonia nitrogen removal ability after being connected to the system, and the removal rate reached 80.03% in 1-11 days. However, in the following 13 to 28 days, the ammonia nitrogen removal rate dropped significantly due to the impact of higher organic load on some microorganisms. This downward trend caused ammonia nitrogen to accumulate in the system, and by the 23rd day, the ammonia nitrogen concentration accumulated to a peak of 26.02 mg / L. After continuous adaptation and proliferation of microbial populations, the ammonia nitrogen that was originally in a state of unsalability was effectively degraded. By the 35th day, the ammonia nitrogen concentration in the system returned to normal levels, proving the stability and reliability of the breeding method in long-term operation.

[0109] Figure 3 The fluctuation trend and removal rate effect diagram of nitrite in the reactor of Example 1 system running for 171 days. It can be seen from the figure that when the system was initially running, the nitrite concentration was already high, reaching 7.8 mg / L. Despite this, the bacterial flocs have shown efficient removal ability of nitrite since the early stage, with a removal rate of up to 94.95%. In the recirculating aquaculture system, the nitrite concentration has experienced significant fluctuations due to the accumulation of feces and food residues excreted by fish after feeding. However, the nitrifying bacteria in the system have a very high utilization efficiency of nitrite, so that the nitrite concentration in the effluent can be maintained below 0.55 mg / L, and even dropped to 0 mg / L in some periods. In general, the nitrite content in the effluent showed a stable trend, and the average removal rate reached 86.01%. This data shows that even under the condition of organic load fluctuations, the microbial flora in the aquaculture method of the present invention can still effectively treat nitrite and keep the water quality stable. It further confirms the feasibility and efficiency of the aquaculture method and system of the present invention in practical applications.

[0110] Figure 4 The fluctuation trend and removal rate effect diagram of nitrate in the reactor of Example 1 system running for 171 days. It can be seen from the figure that the nitrate content continues to accumulate in the first 86 days. During this period, because the abundance of denitrifying bacteria has not yet reached a high level, and the granular bacterial flocs fail to form enough extracellular polymers, the system fails to achieve the simultaneous nitrification and denitrification. Despite this, the system still exhibits a certain denitrification capacity, which effectively slows down the accumulation rate of nitrate. From the 86th day, the denitrification in the reactor began to dominate, and the denitrification rate exceeded the nitrification rate, causing the nitrate content to begin to decline. This change marks that the system has entered a new stable stage, the activity of denitrifying bacteria has increased, and the extracellular polymers of the granular bacterial flocs have also been significantly increased, thereby achieving more efficient nitrate removal.

[0111] The above analysis shows that the aquaculture method of the present invention can achieve effective control and removal of nitrates through the gradual adaptation and adjustment of the microbial flora during long-term operation. This not only proves the potential of the method in treating nitrates, but also provides important experimental data and theoretical basis for future process optimization.

[0112] Figure 5 It is a linear graph of the C / N variation trend in the reactor in the system of Example 1; it can be seen from the figure that in the initial stage of system operation (from the 1st day to the 30th day): the C / N ratio reaches the highest value on the 1st day, close to 7. Subsequently, in the first 30 days, the C / N ratio drops rapidly and fluctuates between 2 and 4. This is because the nitrogen element in the reactor gradually increases in the initial stage, causing the C / N ratio to drop rapidly. Mid-term stage (from the 30th day to the 110th day): in this stage, the C / N ratio fluctuates relatively greatly, with several rising peaks, the maximum of which is close to 3.5. The overall trend is to maintain a level of about 2, indicating that the ratio of carbon to nitrogen is relatively stable. Late stage (from the 110th day to the 170th day): the C / N ratio shows large fluctuations again, especially a higher peak (greater than 5) appears around the 140th day. Despite the peak fluctuations, the C / N ratio is generally maintained in the range of about 3. That is, the C / N ratio fluctuates within a certain range, but does not change significantly, which indicates that the generation and treatment efficiency of grass carp metabolic waste have reached a stable state, indicating that the system has entered a relatively stable operating state.

[0113] Over time, although the accumulation of total nitrogen (TN) and total phosphorus (TP) caused the COD removal performance to decline, overall, the average COD removal rate was still maintained at 36%. This performance shows that even when the concentrations of TN and TP increase, the recirculating aquaculture method and system of the present invention still have a certain anti-interference ability and a stable organic matter treatment effect.

[0114] In summary, by analyzing the changing trends of ammonia nitrogen, nitrite, nitrate and C / N, the following conclusions can be drawn: Through the use of granular bacterial flocs to construct an efficient circulating water aquaculture system and method defined in the present invention, that is, comprehensive use of microbial flora aggregates for aquaculture, it is possible to effectively remove organic and inorganic pollutants in aquaculture wastewater during long-term operation, maintain water quality stability, and demonstrate its potential and advantages in practical applications.

[0115] Figure 6 This is the electron microscope scanning image of the reactor granular bacterial floc. Figure 7The following are the actual photos of granular bacterial flocs (left), the structure of aerobic granular sludge (middle) and the microscope image (right). As can be seen from the figure, after 171 days of acclimation, the bacterial flocs have initially formed a granular structure, and the particle size has reached 0.25mm. The formation of this structure marks the self-organization and adaptive evolution of the microbial community, laying the foundation for the stability and functionality of the granular bacterial flocs.

[0116] As the particles continue to grow, the space for microbial growth and metabolism inside them increases significantly, and the specific surface area on the surface and inside of the particles also expands. This expansion of specific surface area not only enhances the contact efficiency between the particles and the matrix, but also provides a more suitable habitat for the diverse microbial community, thereby further optimizing the processing capacity of the reactor. In addition, the granular structure helps to improve the sedimentation performance and mechanical stability of the particles, which is of great significance for maintaining the long-term operation of the reactor.

[0117] Figure 8 The Alpha diversity index bar chart shows that the floc particles taken out of the reactor on the 55th day were named R1-A, and the floc particles taken out of the reactor on the 171st day were named R1-B. 372,034 quality sequences and 1,121 bacterial OTUs were obtained from all floc particle samples by paired-end sequencing and OTU clustering. The diversity of microbial communities is reflected by the Shannon and Simpson indexes, and the richness of microbial communities is reflected by the Ace and Chao1 indexes. In the community of R1-B, the Shannon index, Chao1 index, ACE index, and Simpson index all performed better than those of R1-A, indicating that the community of R1-B became more diverse and balanced after a longer period of cultivation and environmental adaptation. This may be because the flocs underwent optimization of the microbial population during the cultivation process, and the excellent microbial community gradually dominated, thereby improving the overall functionality and stability of the community.

[0118] The Chao1 and ACE indices of R1-B were significantly higher than those of R1-A, which may indicate that the microbial community in the reactor gradually became richer during the long-term cultivation process, especially the abundance of rare species increased. This species diversification may be related to the distribution of resources in the reactor, changes in environmental conditions, and the improved adaptability of the bacterial flocs to these conditions.

[0119] At the same time, the lower value of the Simpson index also reflects that the R1-B community is better balanced, the species distribution tends to be even, and there is less single dominant species dominating. This may be that the flocculent group has adapted to the changes in the reactor during the long-term cultivation process, promoting the coexistence of multiple microorganisms. The higher Shannon index in the R1-B sample further indicates that after a longer period of cultivation, the diversity of the microbial community has been significantly improved. This means that on the 171st day, the reactor has accumulated more types of microorganisms, and the relative abundance of these microorganisms tends to be balanced.

[0120] Judging from the performance of the R1-B sample, the high diversity and high balance of its microbial community may make the community more adaptable and stable in the face of environmental fluctuations (such as changes in temperature, pH, water quality, etc.). This community stability is crucial for long-term aquaculture systems and helps improve the purification capacity and shock resistance within the reactor.

[0121] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A highly efficient circulating water aquaculture system constructed by using granular bacterial flocs, characterized in that: The high-efficiency circulating water aquaculture system includes: Aquaculture equipment, including aquaculture drums; The nitrification and denitrification equipment comprises a reactor and an activated sludge unit, wherein the activated sludge unit is located inside the reactor; the activated sludge unit is a granular bacterial floc; Aeration equipment, including aerators; Wherein, the bottom of the aquaculture equipment is connected to the bottom of the reactor through a pipeline via a water pump; The top of the aquaculture equipment is connected to the reactor via a pipeline provided with a solenoid valve.

2. The method of claim 1, wherein the method comprises: A stirrer is arranged inside the reactor.

3. The method of constructing a high-efficiency circulating water aquaculture system using granular bacterial flocs according to claim 2, characterized in that: The reactor has a height-to-diameter ratio of >4.

4. The method of claim 1 for constructing a highly efficient circulating water aquaculture system using granular bacterial flocs, characterized in that: A microporous aeration system is arranged at the bottom layer inside the reactor, and the aerator aerates the reactor through the microporous aeration system.

5. A method for constructing a highly efficient circulating water aquaculture using granular bacterial flocs, characterized in that: The high-efficiency circulating aquaculture system according to any one of claims 1 to 4 is used, with 15 minutes of water intake, 180 minutes of aerobic aeration, 30 minutes of standing and anaerobic reaction, and 15 minutes of drainage as a complete operation cycle, and the operation process includes the following steps: (1) Use a water pump to allow the aquaculture wastewater at the bottom of the aquaculture equipment to enter the reactor and undergo an anaerobic reaction with the granular bacterial flocs; (2) Using an aerator to aerate the reactor, so that the aquaculture wastewater and the granular bacterial flocs are aerobically aerated; (3) Standing and anaerobic reaction; (4) Use a solenoid valve to discharge the water in the reactor into the aquaculture equipment so that the volume exchange rate of the reactor is 50%.

6. A method for constructing a highly efficient circulating water aquaculture using granular bacterial flocs according to claim 5, characterized in that: At the beginning of operation, add carbon source to the breeding barrel until the carbon-nitrogen ratio in the breeding barrel is >6, COD>400, and TN>60, then stop adding.

7. A method for constructing a highly efficient circulating water aquaculture using granular bacterial flocs according to claim 5, characterized in that: The preparation process of the granular bacterial micelle is as follows: The aquaculture wastewater at the bottom of the aquaculture equipment is introduced into the reactor through a water pump, and then subjected to aeration and static sedimentation in sequence, and then introduced again, which is a complete cycle until the sludge concentration in the reactor exceeds 1 g / L and the sludge sedimentation ratio reaches 15% to 20%. The aeration is stopped and granular bacterial flocs are obtained in the reactor; In the second and subsequent cycles, nutrient solution needs to be added when introducing aquaculture wastewater.

8. A method for constructing a highly efficient circulating aquaculture system using granular bacterial flocs according to claim 7, characterized in that: The exposure time is 2-3 days; the static sedimentation time is 1-1.5 hours.

9. A method for constructing a highly efficient circulating aquaculture using granular bacterial flocs according to claim 7, characterized in that: The amount of water introduced into the process in each cycle increases by 1-2L compared with the previous cycle until it reaches 90% of the effective volume of the reactor; the exposure time in each cycle is shortened by 12h compared with the previous cycle.

10. The method for constructing a highly efficient circulating aquaculture system using granular bacterial flocs according to claim 5, characterized in that: During operation, the sludge retention time of the granular flocs was 30 days.

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