A biofilm forming process based on mother bed expansion culture mode and suitable for high salinity seawater recirculating aquaculture system

Abstract

The application discloses a biofilm culturing process based on a mother bed extension culturing mode and suitable for a high-salinity seawater circulating aquaculture system, and belongs to the technical field of water circulating aquaculture in fishery production facilities. First, a biochemical pool is selected as a mother pool (mother bed), biological fillers are concentrated for biofilm culturing, after adding bacteria, a nutrient source is supplemented in a timed and quantitative manner to control water quality parameters, and corresponding temperature and pH are controlled, when ammonia nitrogen and NO2 ‑ concentrations are stably reduced to less than 0.5 mg / L, the mother bed biofilm culturing is successful; subsequently, 10-20% of the mother bed biological fillers of each system are added and distributed for inoculation to seawater inoculation systems, so that the overall biofilm culturing time is shortened and the biofilm culturing cost is reduced. The application is particularly suitable for a high-salinity seawater circulating water aquaculture system, solves the problems of difficult biofilm culturing and slow system maturation of a high-salinity seawater water treatment system, and has the effects of cost reduction and benefit increase.

Description

Technical Field

[0001] This invention relates to a biofilm attachment process for a water recirculation aquaculture system, and more particularly, to a biofilm attachment process based on a mother bed expansion culture method and applicable to high-salinity seawater recirculation aquaculture systems, belonging to the field of water recirculation aquaculture technology in fishery production facilities. Background Technology

[0002] With the increasing demand for healthy and sustainable development in aquaculture, recirculating aquaculture systems (RAS), as an emerging industrialized aquaculture technology, have become a new trend in fisheries. However, due to the characteristics of intensive aquaculture, the accumulation of nitrogen in the aquaculture water is faster and at higher concentrations than in traditional aquaculture methods, especially ammonia nitrogen and nitrite, which pose a significant threat to the health of farmed organisms. Therefore, the treatment of ammonia nitrogen and nitrite in the water is one of the keys to the success of RAS.

[0003] Currently, the most commonly used denitrification method in recirculating aquaculture systems (RAS) is biological denitrification (including two mainstream processes: biofilm process and activated sludge process), which has high denitrification efficiency and low energy consumption. In RAS systems, the biofilm process (MBBR process, also known as moving bed biofilm reactor) is mainly used. In the biological treatment tank, biological packing material is added, and nitrifying bacteria attach and grow on the surface of the packing material. The specific principle is as follows: when circulating water passes through the biological treatment tank, the nitrifying bacteria attached to the biological packing material use inorganic carbon in the water as a carbon source to oxidize ammonia nitrogen and nitrite to obtain energy for their own activities and to multiply. Through the process of "ammonia nitrogen → nitrite → nitrate," the nitrate is ultimately discharged through water replenishment, ultimately achieving the purpose of purifying the water quality.

[0004] The core of biological denitrification lies in cultivating a microbial community adapted to the aquaculture water environment. However, in existing research and applications of microbial biofilm formation methods in recirculating aquaculture systems, especially in high-salinity (salinity greater than 35‰) seawater recirculating aquaculture, there is a lack of feasible solutions that integrate with production. Some methods employ pre-biofilm formation (e.g., CN118307142A), hoping to recirculate immediately after stocking. However, in practice, the characteristics of the microorganisms are not taken into account, and the inhibitory effects of high salinity and nutrient concentrations are ignored. This results in slow attachment and proliferation of microorganisms on new packing materials, poor biofilm formation, and continuous accumulation of nitrite, prolonging the entire biofilm formation cycle or even causing biofilm failure, increasing biofilm formation costs, and disrupting the entire aquaculture plan. Other methods use natural biofilm formation synchronized with production, but the biofilm formation rate is slow, the effluent from the biological treatment tank does not meet the aquaculture requirements, and the aquaculture tank needs large-scale drainage and replacement. Several cycles of aquaculture are required to gradually meet production requirements, which contradicts the concept of recirculating aquaculture.

[0005] Furthermore, existing technology CN105036356A discloses "a method for cultivating a salt-tolerant biofilm," but it addresses the problem that the salt tolerance of existing biofilm processes still cannot exceed 1%-5%. Specifically, it discloses that after successful cultivation of the salt-tolerant biofilm, marine aquaculture wastewater (salinity 3%-4%) is added to acclimate the biofilm, improving its COD degradation capacity for treating marine aquaculture wastewater. Additionally, CN111847663A discloses "a reactor and method for acclimatizing and enriching sulfur autotrophic denitrifying bacteria in a seawater matrix," which specifically addresses the difficulties in starting up sulfur autotrophic denitrification biofilm processes in high-salinity wastewater and the suppression of denitrification performance.

[0006] Therefore, a biofilm attachment strategy that meets practical needs is required to be suitable for high-salinity seawater recirculation aquaculture processes. Summary of the Invention

[0007] This invention aims to solve the problems of cumbersome steps, long time consumption, and high energy consumption in existing biofilm formation processes. It proposes a biofilm formation process based on a mother bed expansion culture method, suitable for high-salinity seawater (salinity greater than 35‰) recirculating aquaculture systems. Specifically, a mother bed expansion culture method is first used to ensure successful biofilm formation; then, well-grown mother bed packing material is distributed and inoculated into the high-salinity seawater recirculating aquaculture system. This shortens the overall biofilm formation time, reduces biofilm formation costs, and is well-suited for high-salinity seawater recirculating aquaculture systems.

[0008] To achieve the above technical objectives, the following technical solution is proposed:

[0009] A biofilm attachment process based on mother bed expansion culture and suitable for high-salinity seawater recirculating aquaculture systems includes the following steps:

[0010] S1 Calculation of Mother Bed Bio-filler Quantity: Based on the total filler quantity designed for the high-salinity seawater recirculating aquaculture system, and using a distribution ratio of 10-20%, the required mother bed bio-filler quantity for the high-salinity seawater recirculating aquaculture system is calculated.

[0011] The 10-20% allocation ratio is set to ensure successful biofilm formation in the seawater inoculation system, reasonable reaction time, and a reasonable allocation of the workload of operators. It can be further adjusted according to actual needs.

[0012] S2 Calculation of Mother Bed Quantity: Based on a mother bed biological filler filling rate of 45-55%, the required number of mother beds for a high-salinity seawater recirculating aquaculture system is determined.

[0013] Among them, the setting of a 45-55% mother bed biological packing filling rate controls the maximum filling rate of the mother bed to ensure the complete fluidization of the packing, thereby improving the subsequent biofilm formation efficiency and quality.

[0014] S3 Add fresh water, microbial agent, and mother bed biological packing: Add fresh water to the mother bed to the designed water level, then add microbial agent to the mother bed at an effective water volume dosage of 180-220 mg / L; then add mother bed biological packing and aerate for 45-50 hours (e.g., turn on the Roots blower).

[0015] In this process, freshwater biofilm is used, and after adding the microbial agent, the substrate is first thoroughly aerated to activate the agent before subsequent nutrient adjustments are made, which facilitates the accelerated maturation of the mother bed packing. Preferably, the microbial agent used is a liquid compound nitrifying bacteria.

[0016] S4 adds nutrients to the mother bed;

[0017] The specific process is as follows:

[0018] S4.1 Start the Roots blower to aerate and oxygenate, keeping the MBBR packing in a fluidized tumbling state; add sodium bicarbonate to adjust the total alkalinity in the mother bed to >100 mg / L;

[0019] S4.2 Add nitrogen sources (such as ammonium chloride and sodium nitrite) to freshwater to control the ammonia nitrogen concentration in the freshwater body to 10-15 mg / L and the nitrite concentration to 10-15 mg / L;

[0020] S4.3 Add a phosphorus source (such as potassium dihydrogen phosphate) to freshwater with an N:P ratio of 5:1.

[0021] S4.4 Control the temperature of freshwater to >25℃;

[0022] S5 Water Quality Environment Monitoring;

[0023] The specific process is as follows:

[0024] S5.1 Water quality testing: When ammonia nitrogen concentration < 0.5 mg / L and nitrite concentration < 0.5 mg / L, nitrogen source (such as ammonium chloride and sodium nitrite) is added again to control the ammonia nitrogen concentration in freshwater to 10-15 mg / L and the nitrite concentration to 10-15 mg / L.

[0025] S5.2 Maintain dissolved oxygen ≥5mg / L and control the temperature of freshwater >25℃;

[0026] S5.3 Add sodium carbonate or sodium bicarbonate to maintain total alkalinity >100 mg / L and pH 7.5-8.0;

[0027] Specifically, nitrifying 1 mg of ammonia nitrogen requires 7.14 mg of alkalinity. According to the pH-alkalinity relationship equation established by the chemical equilibrium of the carbonate system, a residual total alkalinity greater than 40 mg / L is needed to maintain a pH > 7 in the aquatic environment. Furthermore, in actual operation, it was found that when the ammonia nitrogen concentration is 10-15 mg / L, as the nitrification reaction proceeds, when the residual alkalinity is < 100 mg / L, the pH is less than 7.5, and the nitrification rate of the mother bed begins to decrease. Therefore, this technical solution controls the alkalinity to > 100 mg / L, effectively ensuring the nitrification efficiency of the microorganisms.

[0028] S6 mother bed biological packing material inoculation;

[0029] When the mother bed is continuously supplemented with nutrients for 7 days, and the ammonia nitrogen concentration is <0.5mg / L and the nitrite concentration is <0.5mg / L within 24 hours, the mother bed packing is considered to have successfully attached biofilm, and mature packing is obtained. Cultivation is stopped, and the mother bed biological packing (accounting for 10-20% of the total packing in the seawater inoculation system) is added to the seawater inoculation system according to the allocation ratio in step S1. The remaining 80-90% of the total packing in each seawater inoculation system is added in batches in step S7 below. The initial addition of new packing is done at a ratio of mother bed biological packing to new packing of 1:1.

[0030] The specific process is as follows:

[0031] S6.1 Add the mother bed biological packing material into the seawater inoculation system according to the allocation ratio in step S1;

[0032] S6.2 Add new packing material in batches according to the designed amount of new packing material for the seawater inoculation system; the interval between additions shall be based on the complete fluidization of the added new packing material.

[0033] S7 Seawater Inoculation System Biofilm Formation: High-salinity seawater is added to the seawater inoculation system to the design water level and aerated. High-salinity seawater is used for direct biofilm formation because mature microbial communities can quickly adapt to the high-salinity environment and enable new packing materials to attach quickly, shortening the biofilm formation time of the entire system.

[0034] The specific process is as follows:

[0035] S7.1 Add a nitrogen source (ammonium chloride) to high-salinity seawater to control the ammonia nitrogen concentration in the high-salinity seawater to 10-15 mg / L;

[0036] The difference between this method and adding two nitrogen sources for biofilm formation in the mother bed is that the mature microbial community in the mother bed biological packing has a complete nitrification process, so there is no need to use nitrite to regulate the proliferation of nitrite-oxidizing bacteria. At the same time, it reduces the types of agents and lowers the purchase and storage costs.

[0037] S7.2 Add a phosphorus source (such as potassium dihydrogen phosphate) to high-salinity seawater with an N:P ratio of 5:1.

[0038] S7.3 When the concentrations of ammonia nitrogen and nitrite are both <0.5 mg / L, continue to add nitrogen source as required in step S7.1;

[0039] Ammonia nitrogen and nitrite were tested every other day. When the concentrations of ammonia nitrogen and nitrite were both <0.5 mg / L, nitrogen source was added again.

[0040] S7.4 Add sodium carbonate or sodium bicarbonate to maintain total alkalinity >100mg / L and pH 7.5-8.0; control dissolved oxygen ≥5mg / L and water temperature >25℃;

[0041] S7.5 After the newly added packing material has fluidized, add another portion of the new packing material;

[0042] S8 was incorporated into the high-salinity seawater recirculating aquaculture system;

[0043] The specific process is as follows:

[0044] S8.1 Judgment: When the seawater inoculation system adds nitrogen source daily according to step S7, and the ammonia nitrogen concentration in the high salinity seawater is <0.5mg / L and the nitrite concentration is <0.5mg / L within 24 hours for 7 consecutive days, the seawater inoculation system is considered to have successfully inoculated and formed a biofilm, and it is then incorporated into the circulation.

[0045] S8.2 Circulation: Control the initial circulating water volume to 10% of the designed circulating water volume, and let it enter the circulating water treatment system. The effluent from the circulating water treatment system is tested daily.

[0046] S8.3 Increment: The circulating water volume is controlled with ammonia nitrogen concentration <0.5mg / L and nitrite concentration <0.5mg / L as reference values. When the ammonia nitrogen and nitrite concentrations are both stable <0.5mg / L for 3 consecutive days, the circulating water volume is increased by 10% until the circulating water volume reaches the design circulating volume.

[0047] During the circulation process, the total alkalinity is controlled to be >100mg / L, and the pH is 7.5-8.0.

[0048] The beneficial technical effects of adopting this technical solution are as follows:

[0049] I. In this invention, centralized culture in a mother bed is the core. After maturation, the mature biofilm is inoculated and attached to the substrate. The salinity adaptability of the mature biofilm is utilized, along with precise addition of nutrient source concentration and stable temperature control, to rapidly cultivate new substrate. This avoids the problems of salinity inhibition and substrate concentration inhibition, which are common in traditional biofilm attachment methods, leading to difficulties in biofilm adhesion and long attachment times.

[0050] Second, the present invention uses centralized culture mother bed packing material, which also avoids the energy consumption problem caused by the full-scale deployment of traditional film attaching methods. Especially for newly built breeding bases, this method can be used to attach film during the construction period of the base, and inoculate after construction, shortening the breeding cycle and reducing costs and increasing efficiency for enterprises. Attached Figure Description

[0051] Figure 1 This is a flowchart of Example 1;

[0052] Figure 2 The figure shows the comparison of ammonia nitrogen removal effects of different proportions of mature packing materials in Example 1.

[0053] Figure 3 The figure shows the comparison of the nitrite removal effect of different proportions of mature filler in Example 1.

[0054] Figure 4 The following is a field diagram of the biofilm formation operation in Example 2 (biofilm formation was successful, and microorganisms were attached to the packing material).

[0055] Figure 5 To discuss the working state diagram (fluidization state) of the new packing material in Example 3 when it was not added in batches;

[0056] Figure 6 To discuss the working state diagram (fluidization state) of the new packing material added in batches in Example 3;

[0057] Figure 7 The figure shows the comparison of the effects of different microbial agent dosages on nitrite removal rates in Example 4.

[0058] Figure 8 This is a schematic diagram showing the arrangement of the various systems in the invention;

[0059] In the diagram, 1 is the mother bed, 2 is the seawater inoculation system, and 3 is the high-salinity seawater recirculation aquaculture system. Detailed Implementation

[0060] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0061] Example 1

[0062] A biofilm attachment technology based on mother bed expansion culture and suitable for high-salinity seawater recirculating aquaculture systems, such as Figure 1 , Figure 8 As shown, it includes the following steps:

[0063] S1 Calculation of Mother Bed Bio-filler Quantity: Based on the total filler quantity designed for the high-salinity seawater recirculating aquaculture system, and using a distribution ratio of 10-20%, the required mother bed bio-filler quantity for the high-salinity seawater recirculating aquaculture system is calculated.

[0064] The 10-20% allocation ratio is set to ensure successful biofilm formation in the seawater inoculation system, reasonable reaction time, and appropriate manpower for operation, and can be adjusted appropriately according to actual needs.

[0065] S2 Calculation of Mother Bed Quantity: Based on a mother bed biological filler filling rate of 45-55%, the required number of mother beds for a high-salinity seawater recirculating aquaculture system is determined.

[0066] Among them, the setting of a 45-55% mother bed biological packing filling rate controls the maximum filling rate of the mother bed to ensure the complete fluidization of the packing, thereby improving the subsequent biofilm formation efficiency and quality.

[0067] S3 Add fresh water, microbial agent, and mother bed biological packing: Add fresh water to the mother bed to the designed water level, then add microbial agent to the mother bed at an effective water volume dosage of 180-220 mg / L; then add mother bed biological packing and aerate for 45-50 hours (e.g., turn on the Roots blower).

[0068] In this process, freshwater biofilm is used, and after adding the microbial agent, the substrate is first thoroughly aerated to activate the agent before subsequent nutrient adjustments are made, which facilitates the accelerated maturation of the mother bed packing. Preferably, the microbial agent used is a liquid compound nitrifying bacteria.

[0069] S4 adds nutrients to the mother bed;

[0070] The specific process is as follows:

[0071] S4.1 Start the Roots blower to aerate and oxygenate, keeping the MBBR packing in a fluidized tumbling state; add sodium bicarbonate to adjust the total alkalinity in the mother bed to >100 mg / L;

[0072] S4.2 Add nitrogen sources (such as ammonium chloride and sodium nitrite) to freshwater to control the ammonia nitrogen concentration in the freshwater body to 10-15 mg / L and the nitrite concentration to 10-15 mg / L;

[0073] S4.3 Add a phosphorus source (such as potassium dihydrogen phosphate) to freshwater with an N:P ratio of 5:1.

[0074] S4.4 Control the temperature of freshwater to >25℃;

[0075] S5 Water Quality Environment Monitoring;

[0076] The specific process is as follows:

[0077] S5.1 Water quality testing: When ammonia nitrogen concentration < 0.5 mg / L and nitrite concentration < 0.5 mg / L, nitrogen source (such as ammonium chloride and sodium nitrite) is added again to control the ammonia nitrogen concentration in freshwater to 10-15 mg / L and the nitrite concentration to 10-15 mg / L.

[0078] S5.2 Maintain dissolved oxygen ≥5mg / L and control the temperature of freshwater >25℃;

[0079] S5.3 Add sodium carbonate or sodium bicarbonate to maintain total alkalinity >100 mg / L and pH 7.5-8.0;

[0080] Specifically, nitrifying 1 mg of ammonia nitrogen requires 7.14 mg of alkalinity. According to the pH-alkalinity relationship equation established by the chemical equilibrium of the carbonate system, a residual total alkalinity greater than 40 mg / L is needed to maintain a pH > 7 in the aquatic environment. Furthermore, in actual operation, it was found that when the ammonia nitrogen concentration is 10-15 mg / L, as the nitrification reaction proceeds, when the residual alkalinity is < 100 mg / L, the pH is less than 7.5, and the nitrification rate of the mother bed begins to decrease. Therefore, this technical solution controls the alkalinity to > 100 mg / L, effectively ensuring the nitrification efficiency of the microorganisms.

[0081] Total alkalinity > 100 mg / L is considered the residual alkalinity of freshwater. The alkalinity consumed needs to be replenished based on the amount of ammonia nitrogen removed. The calculation method for sodium bicarbonate addition is: sodium bicarbonate addition = biological tank volume × (336 + ammonia nitrogen removal concentration value × 12), where the ammonia nitrogen removal concentration value is 10-15 mg / L.

[0082] S6 mother bed biological packing material inoculation;

[0083] When the mother bed is continuously supplemented with nutrients for 7 days, and the ammonia nitrogen concentration is <0.5 mg / L and the nitrite concentration is <0.5 mg / L within 24 hours, the mother bed packing is considered to have successfully formed a biofilm, and mature packing material is obtained. Cultivation is then stopped. The mother bed biological packing material (accounting for 10-20% of the total packing material in the seawater inoculation system) is added to the seawater inoculation system according to the allocation ratio in step S1. The remaining 80-90% of the total packing material in each seawater inoculation system is added in batches in step S7 below. The initial addition of new packing material is at a ratio of mother bed biological packing material to new packing material of 1:1; the remaining new packing material is added to the seawater inoculation system in two batches at ratios of 1:1 and 1:2. The specific purpose is that, as mentioned above, the fluidization of new packing material in water takes a long time, especially in high-salinity seawater. If all of it is added at once, the packing material will be affected by buoyancy and aeration, with most of it exposed to the air and not participating in biofilm formation, thus prolonging the biofilm formation time in the system. Adding nutrients in proportion and in batches can enable the new packing material to quickly attach microorganisms and fluidize quickly. In actual operation, it also facilitates the rapid dissolution of nutrients in high-salinity seawater.

[0084] The specific process is as follows:

[0085] S6.1 Add the mother bed biological packing material into the seawater inoculation system according to the allocation ratio in step S1;

[0086] S6.2 Add new packing material in batches according to the designed amount of new packing material for the seawater inoculation system; the interval between additions shall be based on the complete fluidization of the added new packing material.

[0087] S7 Seawater Inoculation System Biofilm Formation: High-salinity seawater is added to the seawater inoculation system to the design water level and aerated. High-salinity seawater is used for direct biofilm formation because mature microbial communities can quickly adapt to the high-salinity environment and enable new packing materials to attach quickly, shortening the biofilm formation time of the entire system.

[0088] The specific process is as follows:

[0089] S7.1 Add a nitrogen source (ammonium chloride) to high-salinity seawater to control the ammonia nitrogen concentration in the high-salinity seawater to 10-15 mg / L;

[0090] The difference between this method and adding two nitrogen sources for biofilm formation in the mother bed is that the mature microbial community in the mother bed biological packing has a complete nitrification process, so there is no need to use nitrite to regulate the proliferation of nitrite-oxidizing bacteria. At the same time, it reduces the types of agents and lowers the purchase and storage costs.

[0091] S7.2 Add a phosphorus source (such as potassium dihydrogen phosphate) to high-salinity seawater with an N:P ratio of 5:1.

[0092] S7.3 When the concentrations of ammonia nitrogen and nitrite are both <0.5 mg / L, continue to add nitrogen source as required in step S7.1;

[0093] Ammonia nitrogen and nitrite were tested every other day. When the concentrations of ammonia nitrogen and nitrite were both <0.5 mg / L, nitrogen source was added again.

[0094] S7.4 Add sodium carbonate or sodium bicarbonate to maintain total alkalinity >100mg / L and pH 7.5-8.0; control dissolved oxygen ≥5mg / L and water temperature >25℃;

[0095] S7.5 After the newly added packing material has fluidized, add another portion of the new packing material;

[0096] S8 was incorporated into the high-salinity seawater recirculating aquaculture system;

[0097] The specific process is as follows:

[0098] S8.1 Judgment: When the seawater inoculation system adds nitrogen source daily according to step S7, and the ammonia nitrogen concentration in the high salinity seawater is <0.5mg / L and the nitrite concentration is <0.5mg / L within 24 hours for 7 consecutive days, the seawater inoculation system is considered to have successfully inoculated and formed a biofilm, and it is then incorporated into the circulation.

[0099] S8.2 Circulation: Control the initial circulating water volume to 10% of the designed circulating water volume, and let it enter the circulating water treatment system. The effluent from the circulating water treatment system is tested daily.

[0100] S8.3 Increment: The circulating water volume is controlled with ammonia nitrogen concentration <0.5mg / L and nitrite concentration <0.5mg / L as reference values. When the ammonia nitrogen and nitrite concentrations are both stable <0.5mg / L for 3 consecutive days, the circulating water volume is increased by 10% until the circulating water volume reaches the design circulating volume.

[0101] During the circulation process, the total alkalinity is controlled to be >100mg / L, and the pH is 7.5-8.0.

[0102] Example 2

[0103] Based on Example 1, this example provides further explanation regarding the quantity of biological packing material in the mother bed and the calculation of the total number of mother beds, as detailed below:

[0104] The amount of packing material used in a single high-salinity seawater recirculating aquaculture system is: a (m³), effective water volume is x (m³), a total of N systems. Therefore, the amount of packing material used in the mother bed is:

[0105] ;

[0106] Furthermore, utilizing the system's circulating water treatment tank, the number of mother beds is:

[0107] .

[0108] Example 3

[0109] Based on Examples 1-2, the microbial inoculant in this example is further explained as follows:

[0110] The microbial agents used are commercially available. Whether in powder or liquid form, they are in a dormant state due to production and transportation, and the microorganisms require activation stimulation. To maximize the utilization of the system treatment tank while saving aeration and heat preservation energy (in winter when there is no cheap heat source), a mother bed biological packing filling rate of 45-55% is adopted. Since a large amount of packing is used in a single tank, the biological packing can be added to the mother bed in two stages. Due to the surface structure of the new biological packing, most of it will drift initially. However, fresh water fluidizes more rapidly than seawater. Therefore, the order of adding fresh water, microbial agents, and mother bed biological packing is limited to shorten the total time for agent activation and packing fluidization.

[0111] In addition, the microbial agent includes components of compound nitrifying bacteria, preferably including nitrifying bacteria and nitrite-oxidizing bacteria (which are commonly selected strains).

[0112] Discussion of Example 1

[0113] Based on Example 1, this discussion example examines the impact of the mature packing material distribution ratio on ammonia nitrogen removal rate and nitrite (hereinafter referred to as nitrite) removal rate. Details are as follows:

[0114] The effects of different amounts of mature packing material (5% mother bed biological packing), 10% mature packing material (10% mother bed biological packing), 20% mature packing material (20% mother bed biological packing), 100% mature packing material (100% mother bed biological packing), and 100% new packing material were compared under the same control conditions. The results are as follows: Figure 2 and Figure 3 As shown.

[0115] Figure 2 In the experiment, the ammonia nitrogen treatment change trend of the 20% mature packing ratio experimental group was consistent with that of the 100% mature packing ratio experimental group, achieving the same treatment effect as the 100% mature packing ratio experimental group, with a time much shorter than that of the 5% and 10% mature packing ratio experimental groups.

[0116] Figure 3 In the experimental group with a 20% mature packing ratio, the trend of nitrite treatment was consistent with that of the experimental group with a 100% mature packing ratio. Nitrite in the experimental groups with a 5% and 10% mature packing ratios continued to accumulate. These two experimental groups achieved the same treatment effect as the experimental groups with a 20% and 100% mature packing ratios, but required a longer time.

[0117] Therefore, considering factors such as cost, time, and treatment effectiveness, the proportion of mature packing material is limited to 10-20%.

[0118] Discussion of Example 2

[0119] Based on Example 1, this discussion example is based on publicly available information (such as: Water Supply and Drainage Design Manual, edited by Beijing Municipal Engineering Design and Research Institute Co., Ltd.). Based on extensive engineering application experience, it is found that the maximum aerobic zone filling rate in the seawater inoculation system is 60%, and the anoxic zone filling rate is 50%. All seawater inoculation systems in the base adopt aerobic aeration technology.

[0120] Therefore, while ensuring the fluidization requirements of the packing and the energy consumption of the blower, the filling rate of the mother bed biological packing is set at 45-50%, such as... Figure 4 As shown.

[0121] Discussion of Example 3

[0122] Building upon Example 1, this discussion example examines the impact of the new filler addition method on the seawater inoculation system. Specifically:

[0123] 1. When using a single-addition method, the packing material overflows during aeration, making it impossible to observe the aeration process or add nutrients. Figure 5 ;

[0124] Second, the packing was added in batches according to a proportional ratio, and no packing overflow occurred; the packing fluidization was normal. Figure 6 .

[0125] Therefore, the seawater inoculation system adds the new packing material in batches, and the new packing material is added in three batches at a volume ratio of 1:1, 1:1, and 1:2 with the mother bed biological packing material (mature packing material).

[0126] Discussion of Example 4

[0127] Based on Example 1, this discussion case investigates the effect of microbial agent dosage on nitrite removal rate. Specifically, three concentration gradients were designed for the effective water volume: 200 mg / L, 400 mg / L, and 600 mg / L; then, the nitrite removal rate of the microbial agent at the corresponding concentrations was statistically analyzed.

[0128] like Figure 7 As shown, by comparing the removal rate of nitrite by microbial agents, it was found that microbial agents at high concentrations did not show a significant removal advantage. Therefore, considering factors such as cost and removal rate, the effective water volume dosage was determined to be 180-220 mg / L.

[0129] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biofilm attachment process based on mother bed expansion culture and applicable to high-salinity seawater recirculating aquaculture systems, characterized in that, Includes the following steps: S1 Calculation of Mother Bed Bio-filler Quantity: Based on the total filler quantity designed for the high-salinity seawater recirculating aquaculture system, and using a distribution ratio of 10-20%, the required mother bed bio-filler quantity for the high-salinity seawater recirculating aquaculture system is calculated. S2 Calculation of Mother Bed Quantity: Based on a mother bed biological filler filling rate of 45-55%, the required number of mother beds for a high-salinity seawater recirculating aquaculture system is determined. S3 Add fresh water, microbial agent, and mother bed biological packing: Add fresh water to the mother bed to the design water level, then add microbial agent to the mother bed at an effective water volume dosage of 180-220 mg / L; then add mother bed biological packing and aerate for 45-50 hours. S4 adds nutrients to the mother bed to control the following in the freshwater: ammonia nitrogen concentration of 10-15 mg / L, nitrite concentration of 10-15 mg / L, and temperature >25℃; Specifically, it includes: S4.1 Aeration and oxygenation are carried out to maintain the biological packing material in the mother bed in a fluidized and tumbling state, and the total alkalinity in the mother bed is adjusted to >100 mg / L; S4.2 Add a nitrogen source to freshwater to control the concentration of ammonia nitrogen and nitrite in the freshwater body to 10-15 mg / L and 10-15 mg / L respectively; S4.3 Add a phosphorus source to freshwater with an N:P ratio of 5:1; S4.4 Control the temperature of freshwater to >25℃; The nitrogen sources include ammonium chloride and sodium nitrite, and the phosphorus source is potassium dihydrogen phosphate. S5 water quality environmental monitoring and control: dissolved oxygen ≥ 5 mg / L, total alkalinity > 100 mg / L, pH 7.5-8.0; S6 Mother Bed Bio-filler Inoculation: When the mother bed is continuously supplemented with nutrients for 7 days, and the ammonia nitrogen concentration is <0.5mg / L and the nitrite concentration is <0.5mg / L within 24 hours, the mother bed bio-filler is considered to have successfully attached to the biofilm, and the culture is stopped; according to the distribution ratio in step S1, the mother bed bio-filler is added to the seawater inoculation system separately, and new filler is added to the seawater inoculation system in batches; The interval between batches of adding the mother bed biological packing material is based on the complete fluidization of the added mother bed biological packing material. The new packing was added in three batches at a volume ratio of 1:1, 1:1, and 1:2 between the mother bed biological packing and the new packing. S7 Seawater Inoculation System Biofilm Formation: Add high-salinity seawater to the seawater inoculation system to the designed water level and aerate; control the high-salinity seawater body to have the following concentrations: ammonia nitrogen 10-15 mg / L, dissolved oxygen ≥5 mg / L, total alkalinity >100 mg / L, pH 7.5-8.0, and water temperature >25℃. Specifically, it includes: S7.1 Add a nitrogen source to high-salinity seawater to control the ammonia nitrogen concentration in the high-salinity seawater to 10-15 mg / L; S7.2 Add a phosphorus source to high-salinity seawater with an N:P ratio of 5:1; S7.3 When both ammonia nitrogen and nitrite levels are <0.5 mg / L, continue adding nitrogen source as required in step S7.1; Ammonia nitrogen and nitrite were tested every other day. When the ammonia nitrogen and nitrite levels were both <0.5 mg / L, a nitrogen source was added again. S7.4 Add sodium carbonate or sodium bicarbonate to control total alkalinity > 100 mg / L and pH 7.5-8.0; control dissolved oxygen ≥ 5 mg / L and water temperature > 25℃; S7.5 After the newly added packing material has fluidized, add another portion of the new packing material; The nitrogen source is ammonium chloride, and the phosphorus source is potassium dihydrogen phosphate. S8 is incorporated into the high-salinity seawater recirculating aquaculture system.

2. The biofilm formation process based on the mother bed expansion culture method and applicable to high-salinity seawater recirculating aquaculture systems according to claim 1, characterized in that, The total alkalinity in the mother bed was adjusted to >100 mg / L by adding sodium bicarbonate.

3. The biofilm formation process based on the mother bed expansion culture method and applicable to high-salinity seawater recirculating aquaculture systems according to claim 1, characterized in that, The water quality monitoring in step S5 specifically includes: S5.1 Water quality testing: When ammonia nitrogen concentration < 0.5 mg / L and nitrite concentration < 0.5 mg / L, add nitrogen source until the ammonia nitrogen concentration and nitrite concentration in the freshwater body are 10-15 mg / L and 10-15 mg / L respectively. S5.2 Maintain dissolved oxygen ≥5mg / L and control the temperature of freshwater >25℃; S5.3 Add sodium carbonate or sodium bicarbonate to maintain total alkalinity >100mg / L and pH 7.5-8.

0.

4. The biofilm formation process based on the mother bed expansion culture method and applicable to high-salinity seawater recirculating aquaculture systems according to claim 1, characterized in that, Step S8, which involves incorporating a high-salinity seawater recirculating aquaculture system, specifically includes: Judgment: When the seawater inoculation system adds nitrogen source daily according to step S7, and the ammonia nitrogen concentration in the high salinity seawater is <0.5mg / L and the nitrite concentration is <0.5mg / L within 24 hours for 7 consecutive days, the seawater inoculation system is considered to have successfully inoculated and formed a biofilm, and can be incorporated into the circulation. Circulation: The initial circulating water volume is controlled at 10% of the designed circulating water volume, and the water enters the circulating water treatment system. The effluent from the circulating water treatment system is tested daily. Increment: The circulating water volume is controlled with ammonia nitrogen concentration <0.5mg / L and nitrite concentration <0.5mg / L as reference values. When the ammonia nitrogen and nitrite concentrations are stable at <0.5mg / L for 3 consecutive days, the circulating water volume is increased by 10% until the circulating water volume reaches the design circulation volume. During the circulation process, the total alkalinity is controlled to be >100mg / L, and the pH is 7.5-8.0.

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