A method for purifying the wastewater from California bass farming

Abstract

This invention discloses a method for purifying wastewater from California bass farming, belonging to the field of aquaculture wastewater treatment technology. The purification method includes the following steps: planting barley, peas, and herbs in the California bass farming wastewater, and adding a carrier-immobilized compound microbial agent to the wastewater before planting the barley, peas, and herbs. By synergistically adding the carrier-immobilized compound microbial agent and planting specific plants (barley, peas, and herbs) in the water, a highly efficient plant-carrier-immobilized compound microbial agent synergistic purification system is constructed. Through the triple synergistic effect of plants, microorganisms, and the carrier, the system effectively overcomes the problems of low efficiency, incomplete nitrogen and phosphorus removal, and poor system stability inherent in traditional single-plant purification technologies, thereby achieving stable and efficient purification of California bass farming wastewater with high pollution loads.

Description

Technical Field

[0001] This invention relates to the field of aquaculture wastewater treatment technology, and in particular to a method for purifying the wastewater from California bass farming. Background Technology

[0002] With the large-scale development of the California bass farming industry, the large amount of wastewater generated during the farming process has become a significant source of water pollution. California bass farming wastewater contains high concentrations of pollutants such as ammonia nitrogen, nitrite, total phosphorus, and suspended solids. Direct discharge of this wastewater can lead to eutrophication of receiving water bodies, causing excessive algae growth, reduced dissolved oxygen, and damage to aquatic ecosystems. It also hinders the sustainable development of the aquaculture industry.

[0003] Currently, the main methods for purifying aquaculture wastewater include physical treatment, chemical treatment, and biological treatment. Physical treatment methods (such as sedimentation and filtration) can remove some suspended solids, but they are ineffective at removing dissolved nitrogen and phosphorus. Chemical treatment methods (such as adding flocculants) are prone to secondary pollution and have high operating costs. Among biological treatment methods, aquatic plant purification is widely used due to its low cost and environmental friendliness. However, aquatic plant purification methods have the following drawbacks:

[0004] (1) Low purification efficiency: It often uses a single plant for purification, but when the initial concentration of pollutants in the effluent is high, the absorption load of a single plant is large, and the initial purification rate is slow.

[0005] (2) Incomplete removal of nitrogen and phosphorus: Relying solely on plant absorption cannot completely convert nitrate nitrogen and organic phosphorus in the effluent, and total phosphorus and ammonia nitrogen in the effluent may still exceed the standards;

[0006] (3) Greatly affected by the environment: When there is insufficient light or temperature fluctuations, the photosynthesis of plants is weakened, and the purification effect is unstable.

[0007] Therefore, there is an urgent need to develop a method for purifying California bass aquaculture wastewater that can synergistically improve purification efficiency, enhance pollutant removal effects, and adapt to complex environments, in order to overcome the shortcomings of existing technologies. Summary of the Invention

[0008] The purpose of this invention is to provide a method for purifying the wastewater from California bass farming, in order to solve the problems existing in the prior art.

[0009] To achieve the above objectives, the present invention provides the following solution:

[0010] One of the technical solutions of the present invention: a method for purifying the wastewater from California bass farming, comprising the following steps:

[0011] Barley, peas, and vanilla were planted in the tailwater of California bass farming, and a bulk immobilized compound microbial agent was added to the water before planting the barley, peas, and vanilla.

[0012] This invention provides a method for purifying California bass aquaculture wastewater. By synergistically introducing a carrier-immobilized composite microbial agent into the water body and planting specific plants (barley, peas, and herbs), a highly efficient carrier-immobilized composite microbial agent synergistic purification system is constructed. In this system, the carrier-immobilized composite microbial agent not only provides a stable microenvironment for functional microorganisms, significantly enhancing their colonization ability and metabolic activity in the water body, playing a dual role of "slow release" and "protection," but its carrier itself (such as modified biochar) can directly remove some pollutants through adsorption. Simultaneously, while the plant roots absorb nutrients such as nitrogen and phosphorus, they also provide a large biofilm carrier for the attachment and growth of microorganisms, forming a close "root-microbe" symbiotic system. During the degradation of pollutants, the functional microorganisms also produce substances that promote plant growth, further enhancing the plant's ability to absorb and transform pollutants. This triple synergistic effect of plants, microorganisms, and carriers effectively overcomes the problems of low efficiency, incomplete nitrogen and phosphorus removal, and poor system stability inherent in traditional single-plant purification technologies, thus achieving stable and efficient purification of high-pollution California bass aquaculture wastewater.

[0013] Furthermore, the dosage of the carrier-immobilized composite bacterial agent is 5-10 mg / L.

[0014] Furthermore, the preparation steps of the carrier-immobilized composite microbial agent include: loading the composite microbial agent into modified biochar to obtain a microbial agent / carrier composite; and encapsulating the microbial agent / carrier composite to obtain the carrier-immobilized composite microbial agent.

[0015] Further, the preparation steps of the modified biochar include: drying and crushing corn stalks, then carbonizing them at a temperature of 400-500℃ for 1-3 hours to obtain biochar; soaking the biochar in a magnesium sulfate solution, drying it after soaking, and then carbonizing it again at a temperature of 400-500℃ for 1-3 hours to obtain the modified biochar.

[0016] This invention selects biochar as a microbial carrier and modifies it by soaking in magnesium sulfate solution combined with secondary carbonization, effectively improving the purification effect on the wastewater from California bass farming. Biochar itself has excellent adsorption properties, can rapidly accumulate pollutants, and provides a stable habitat for microorganisms. The modification treatment further enhances its function: the loaded magnesium ions can specifically enhance the phosphorus removal effect; the optimized pore structure increases the specific surface area; and the improved surface chemistry is more conducive to microbial attachment and growth.

[0017] Furthermore, the pulverization specifically refers to pulverizing to the point where it can pass through a 40-mesh sieve.

[0018] Furthermore, the concentration of the magnesium sulfate solution is 0.5-1.0 mol / L.

[0019] Furthermore, the ratio of the biochar to the magnesium sulfate solution is 1g:20-30mL.

[0020] Furthermore, the soaking treatment is carried out at a temperature of 40-50°C for 1-3 hours.

[0021] Furthermore, after the secondary carbonization is completed, the process also includes grinding the material until it can pass through a 100-mesh sieve.

[0022] Furthermore, the compound microbial agent includes: Nitrosomonas, Nitrobacterium, Bacillus cereus, Pseudomonas Sturmea, Bacillus licheniformis, Lactobacillus plantarum, and Rhodopseudomonas palustris.

[0023] The compound microbial agent used in this invention is a scientifically formulated blend of seven functional microbial agents: *Nitrosomonas*, *Nitrobacterium*, *Bacillus cereus*, *Pseudomonas stolonifer*, *Bacillus licheniformis*, *Lactobacillus plantarum*, and *Rhodopseudomonas palustris*. Through functional complementarity and metabolic synergy, these agents constitute a highly efficient and stable micro-ecosystem for pollutant degradation. The synergistic effect is specifically manifested in:

[0024] (1) Highly efficient synergistic conversion of nitrogen: Nitrifying bacteria convert highly toxic ammonia nitrogen into nitrite, which is then further converted into nitrate by Nitrifying bacteria, completing the nitrification process. Subsequently, denitrifying bacteria such as Pseudomonas Sturmectii reduce nitrate and nitrite to nitrogen gas under specific conditions and release it into the atmosphere, thereby achieving complete removal of total nitrogen from the water. This relay effect of "nitrification-denitrification" avoids the accumulation of intermediate products (such as nitrite) and ensures the integrity and high efficiency of nitrogen conversion.

[0025] (2) Synergistic removal of organic matter and phosphorus: Bacillus cereus and Bacillus licheniformis have a strong ability to secrete extracellular enzymes, which can rapidly degrade large molecular organic pollutants such as uneaten feed and feces in the tailwater, converting them into small molecular substances, providing carbon sources for other strains (such as nitrifying bacteria), and reducing the chemical oxygen demand and turbidity of the water. Lactic acid bacteria such as Lactobacillus plantarum can produce organic acids, which helps in the conversion and absorption of soluble phosphorus. Some strains can also directly absorb and utilize phosphorus through microbial assimilation.

[0026] (3) Enhanced Function and System Stability: Bacillus licheniformis, Bacillus cereus, and other bacteria can also produce antibacterial substances, inhibiting the growth of harmful pathogens in the water and improving the biosafety of the system. Rhodopseudomonas palustris, as a photosynthetic bacterium, can utilize small-molecule organic matter under light conditions and remove harmful substances such as sulfides without consuming oxygen, thus broadening the range of purification conditions. The combined action of various bacterial agents forms a complex symbiotic relationship, enhancing the resistance and stability of the bacterial agent community in the face of fluctuations in the quality of the tailwater.

[0027] (4) Mutual promotion between plants and microbial agents: The plant growth hormones (such as indoleacetic acid) and vitamins produced by the compound microbial agents during metabolism can stimulate the development of barley, pea and vanilla roots, and enhance their ability to absorb nutrients and pollutants. Conversely, the organic matter secreted by the plant roots provides a dedicated "food source" for the microbial agents, promoting their growth and reproduction, thus forming a mutually beneficial "root-microbe" symbiotic system.

[0028] In summary, this compound microbial agent is not a simple superposition of microbial agents, but rather a synergistic network constructed through precise functional design, encompassing multiple functions such as nitrification, denitrification, organic matter degradation, phosphorus conversion, and pathogen inhibition. This synergistic effect is the key microbiological basis for achieving deep and efficient purification of California bass aquaculture wastewater. It complements the modified biochar carrier and specific plant systems, jointly ensuring the superiority and stability of the purification effect.

[0029] Furthermore, the loading of the composite microbial agent onto the modified biochar includes: mixing the modified biochar and the bacterial suspension of the composite microbial agent, shaking and adsorbing for 20-24 hours, and then filtering, washing, and drying to obtain the microbial agent / carrier composite.

[0030] Furthermore, the bacterial content of each bacterial agent in the bacterial suspension of the compound bacterial agent is 1.0 × 10⁻⁶. 9 -5.0×10 9 CFU / mL.

[0031] Optionally, the bacterial suspension of the compound bacterial agent is prepared by mixing commercially available liquid bacterial agent and sterile distilled water.

[0032] Furthermore, the ratio of the modified biochar to the bacterial suspension of the composite bacterial agent is 1g:10-20mL.

[0033] Furthermore, the temperature of the oscillation adsorption is 20-30℃, and the vibration speed is 100-200rpm.

[0034] Optionally, the drying temperature is 20-30°C.

[0035] Further, the encapsulation of the bacterial agent / carrier complex includes: mixing polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water, heating and stirring until it becomes colloidal, cooling and then adding the bacterial agent / carrier complex, and then dripping it into a saturated boric acid solution containing 3-5wt% CaCl2, and curing at low temperature for 20-24 hours to obtain the carrier-immobilized composite bacterial agent.

[0036] In this invention, polyvinyl alcohol, sodium alginate, and chitosan are used to encapsulate modified biochar loaded with a composite microbial agent. The main function of this encapsulation layer is to create a stable and controllable microenvironment. This encapsulation layer acts as a "protective shield" and a "slow-release reservoir," significantly improving the survival rate and persistence of the microbial agent in the wastewater. Furthermore, the chitosan has good biocompatibility, providing a more suitable growth and metabolic environment for immobilized microorganisms, which is beneficial for maintaining the activity of the microbial agent.

[0037] Furthermore, the mass ratio of polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water is 5-8:0.3-0.5:0.3-0.5:0.2-0.4:100.

[0038] Furthermore, the heating and stirring temperature is 90-100℃.

[0039] Furthermore, the amount of the bacterial agent / carrier complex added is 15-25% of the sum of the mass of polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water.

[0040] Furthermore, the low-temperature curing temperature is 5-10℃.

[0041] Optionally, the process after low-temperature curing may further include steps of filtration, washing, and drying; the drying temperature is 30-35°C.

[0042] Furthermore, the planting of barley, peas, and vanilla in the California bass aquaculture tailwater includes: evenly sowing germinated barley, pea, and vanilla seeds in a planting basket, then embedding the planting basket into the planting holes of a floating board, and then floating the floating board on the surface of the California bass aquaculture tailwater; the planting ratio of barley, peas, and vanilla is 1:1:1.

[0043] Barley, peas, and vanilla work synergistically to achieve optimal overall water purification results.

[0044] Furthermore, the floating board has an area coverage of 70-80% over the tailwater of the California bass aquaculture.

[0045] Furthermore, the total planting density of barley, hemp peas, and vanilla on the floating board is 18-24 plants / m². 2 .

[0046] The present invention discloses the following technical effects:

[0047] The present invention provides a method for purifying California bass aquaculture wastewater by synergistically introducing a carrier-immobilized compound microbial agent into the water body and planting specific plants (barley, peas, and herbs), thus constructing a highly efficient plant-carrier immobilized compound microbial agent synergistic purification system. Through the triple synergistic effect of plants, microorganisms, and carriers, the method effectively overcomes the problems of low efficiency, incomplete nitrogen and phosphorus removal, and poor system stability of traditional single-plant purification technologies, thereby achieving stable and efficient purification of high-pollution California bass aquaculture wastewater. Detailed Implementation

[0048] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0049] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0050] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0051] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0052] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0053] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0054] In the following embodiments and comparative examples of the present invention, room temperature specifically refers to 20-30°C.

[0055] All raw materials used in the following embodiments and comparative examples of the present invention are common commercially available products, wherein the bacterial suspension of the compound bacterial agent is made by mixing commercially available liquid bacterial agents of each bacterial agent with sterile distilled water.

[0056] The preparation steps of the modified biochar used in the following embodiments and comparative examples of the present invention are as follows: corn stalks are dried and crushed until they can pass through a 40-mesh sieve, and then carbonized at 450°C for 2 hours to obtain biochar; the biochar is soaked in a 0.8 mol / L magnesium sulfate solution (the ratio of biochar to magnesium sulfate solution is 1 g: 25 mL) at 45°C for 2 hours, dried after soaking, and then carbonized again at 450°C for 2 hours. After the second carbonization, the carbonization product is ground until it can pass through a 100-mesh sieve to obtain modified biochar.

[0057] The initial physicochemical properties of the California bass aquaculture wastewater used in the following embodiments and comparative examples of the present invention are the same, as shown in Table 1.

[0058] The water purification tests in the following embodiments and comparative examples of this invention were all conducted outdoors under natural conditions (if it rained, the shielding was provided and removed after the rain stopped). All tests began on April 1, 2025 (the date of administration of the immobilized compound bacterial agent). The water tanks used were all 1m×1m×1m in size. Three sets of parallel tests were set up for each embodiment and comparative example, and the average value of the test results was taken.

[0059] The specific test items and methods involved in the physicochemical property testing of the initial California bass farming wastewater and the water after purification experiments in the following embodiments and comparative examples of the present invention are as follows:

[0060] Total hardness, total alkalinity, total Kjeldahl phosphorus, ammonia nitrogen, and nitrite in the water were determined using the MAC3 method on an iFIA7 fully automated flow injection analyzer; turbidity was determined using an LTURB-3B precision turbidimeter; and pH and dissolved oxygen were determined using an online monitoring instrument.

[0061] Example 1

[0062] Fill the tank with 0.7m of California bass aquaculture tailwater, then add the bulk immobilized compound bacterial agent (dosage: 5mg / L), and let it stand for three days (stir once a day for 10 minutes each time).

[0063] Evenly sow the germinated barley, pea, and vanilla seeds (6 seeds per basket) onto the absorbent cotton in three planting baskets. Cover each basket with a thin layer of quartz sand (0.5 cm thick, to secure the seeds and prevent water from washing them away). Then, embed the three planting baskets into a 0.75 m² area.2 In the planting holes of the floating board (i.e., the area of ​​the floating board covering the tailwater of the California bass aquaculture is 75%), the planting density of barley, peas, and vanilla on the floating board is 6 plants / m². 2 The total planting density is 18 plants / m². 2 The planting ratio of barley, peas, and vanilla was 1:1:1. A floating board was placed in a tank containing wastewater from California bass farming, after three days of adding a bulk immobilized compound microbial agent. A nylon rope was used to connect the fixing ring to the fixing hole at the top of the tank, ensuring the floating board floated stably (in contact with the water surface, without tilting). Twelve days after the floating board was placed, the physicochemical properties of the purified water were tested, as shown in Table 1.

[0064] The preparation steps of the carrier-immobilized composite bacterial agent are as follows:

[0065] S1. A bacterial suspension of modified biochar and compound microbial agents (prepared by mixing commercially available liquid microbial agents of *Nitrosomonas*, *Nitrobacterium*, *Bacillus cereus*, *Pseudomonas stolonifer*, *Bacillus licheniformis*, *Lactobacillus plantarum*, and *Rhodopseudomonas palustris* with sterile distilled water; the bacterial content of each agent in the bacterial suspension of the compound microbial agent is 1.0 × 10⁻⁶) 9 The bacterial agent / carrier complex was mixed in an Erlenmeyer flask at a ratio of 1 g: 10 mL. The Erlenmeyer flask was placed in a constant temperature shaker (20℃, 100 rpm) and shaken for 20 h for adsorption. After the adsorption was completed, the mixture was filtered, rinsed three times with sterile physiological saline, and dried at 20℃ to obtain the bacterial agent / carrier complex.

[0066] S2. Polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water are mixed in a mass ratio of 5:0.3:0.3:0.2:100. The mixture is heated and stirred at 100°C until it becomes a colloidal state. After cooling to room temperature, the bacterial agent / carrier complex is added (the amount of bacterial agent / carrier complex added is 15% of the sum of the mass of polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water). The mixture is stirred evenly to obtain a mixture. Then, the mixture is dropped into a saturated boric acid solution containing 3wt% CaCl2 and cured at 5°C for 20 hours. After filtration, washing with water and drying at 30°C, the carrier-immobilized composite bacterial agent is obtained.

[0067] Example 2

[0068] Fill the tank with 0.7m of California bass aquaculture tailwater, then add the bulk immobilized compound bacterial agent (dosage: 8mg / L), and let it stand for three days (stir once a day for 10 minutes each time).

[0069] Evenly sow the germinated barley, pea, and vanilla seeds (7 seeds per basket) onto the absorbent cotton in three planting baskets. Cover each basket with a thin layer of quartz sand (0.5 cm thick, to secure the seeds and prevent water from washing them away). Then, embed the three planting baskets into a 0.75 m² area. 2 In the planting holes of the floating board (i.e., the area of ​​the floating board covering the California bass aquaculture tailwater is 75%), the planting density of barley, peas, and vanilla on the floating board is 7 plants / m². 2 The total planting density is 21 plants / m². 2 The planting ratio of barley, peas, and vanilla was 1:1:1. A floating board was placed in a tank containing wastewater from California bass farming, after three days of adding a bulk immobilized compound microbial agent. A nylon rope was used to connect the fixing ring to the fixing hole at the top of the tank, ensuring the floating board floated stably (in contact with the water surface, without tilting). Twelve days after the floating board was placed, the physicochemical properties of the purified water were tested, as shown in Table 1.

[0070] The preparation steps of the carrier-immobilized composite bacterial agent are as follows:

[0071] S1. A bacterial suspension of modified biochar and compound microbial agents (prepared by mixing commercially available liquid microbial agents of *Nitrosomonas*, *Nitrobacterium*, *Bacillus cereus*, *Pseudomonas stolonifer*, *Bacillus licheniformis*, *Lactobacillus plantarum*, and *Rhodopseudomonas palustris* with sterile distilled water; the bacterial content of each agent in the bacterial suspension of the compound microbial agent is 3.0 × 10⁻⁶) 9 The bacterial agent / carrier complex was mixed in an Erlenmeyer flask at a ratio of 1 g: 15 mL. The Erlenmeyer flask was placed in a constant temperature shaker (25℃, 150 rpm) and shaken for 22 h for adsorption. After the adsorption was completed, the mixture was filtered, rinsed three times with sterile physiological saline, and dried at 25℃.

[0072] S2. Polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water are mixed in a mass ratio of 6:0.4:0.4:0.3:100. The mixture is heated and stirred at 100°C until it becomes a colloidal state. After cooling to room temperature, the bacterial agent / carrier complex is added (the amount of bacterial agent / carrier complex added is 20% of the sum of the mass of polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water). The mixture is stirred evenly to obtain a mixture. Then, the mixture is dropped into a saturated boric acid solution containing 4wt% CaCl2 and cured at 8°C for 22 hours. Then, the mixture is filtered, washed with water and dried at 30°C to obtain a carrier-immobilized composite bacterial agent.

[0073] Example 3

[0074] Fill the tank with 0.7m of California bass aquaculture tailwater, then add the bulk immobilized compound bacterial agent (dosage: 10mg / L), and let it stand for three days (stir once a day for 10 minutes each time).

[0075] Evenly sow the germinated barley, pea, and vanilla seeds (8 seeds per basket) onto the absorbent cotton in three planting baskets. Cover each basket with a thin layer of quartz sand (0.5 cm thick, to secure the seeds and prevent water from washing them away). Then, embed the three planting baskets into a 0.75 m² area. 2 In the planting holes of the floating board (i.e., the area of ​​the floating board covering the California bass aquaculture tailwater is 75%), the planting density of barley, peas, and vanilla on the floating board is 8 plants / m². 2 The total planting density is 24 plants / m². 2 The planting ratio of barley, peas, and vanilla was 1:1:1. A floating board was placed in a tank containing wastewater from California bass farming, after three days of adding a bulk immobilized compound microbial agent. A nylon rope was used to connect the fixing ring to the fixing hole at the top of the tank, ensuring the floating board floated stably (in contact with the water surface, without tilting). Twelve days after the floating board was placed, the physicochemical properties of the purified water were tested, as shown in Table 1.

[0076] The preparation steps of the carrier-immobilized composite bacterial agent are as follows:

[0077] S1. A bacterial suspension of modified biochar and compound microbial agents (prepared by mixing commercially available liquid microbial agents of *Nitrosomonas*, *Nitrobacterium*, *Bacillus cereus*, *Pseudomonas stolonifer*, *Bacillus licheniformis*, *Lactobacillus plantarum*, and *Rhodopseudomonas palustris* with sterile distilled water; the bacterial content of each agent in the bacterial suspension of the compound microbial agent is 5.0 × 10⁻⁶) 9 The bacterial agent / carrier complex was mixed in an Erlenmeyer flask at a ratio of 1g:10-20mL. The Erlenmeyer flask was placed in a constant temperature shaker (30℃, 200rpm) for 24h of shaking and adsorption. After the shaking and adsorption were completed, the mixture was filtered, rinsed three times with sterile physiological saline, and dried at 30℃ to obtain the bacterial agent / carrier complex.

[0078] S2. Polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water are mixed in a mass ratio of 8:0.5:0.5:0.4:100. The mixture is heated and stirred at 100°C until it becomes a colloidal state. After cooling to room temperature, the bacterial agent / carrier complex is added (the amount of bacterial agent / carrier complex added is 25% of the sum of the mass of polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water). The mixture is stirred evenly to obtain a mixture. Then, the mixture is dropped into a saturated boric acid solution containing 5wt% CaCl2 and cured at 10°C for 24 hours. The mixture is then filtered, washed with water, and dried at 30°C to obtain a carrier-immobilized composite bacterial agent.

[0079] Comparative Example 1

[0080] Fill the tank with 0.7m of California bass aquaculture wastewater. Evenly sow the germinated barley, pea, and vanilla seeds (6 seeds per basket) onto the absorbent cotton in three planting baskets. Cover each basket with a thin layer of quartz sand (0.5cm thick, to secure the seeds and prevent water from washing them away). Then, embed the three planting baskets into a 0.75m² area... 2 In the planting holes of the floating board (i.e., the area of ​​the floating board covering the tailwater of the California bass aquaculture is 75%), the planting density of barley, peas, and vanilla on the floating board is 6 plants / m². 2 The total planting density is 18 plants / m². 2 The ratio of barley, peas, and vanilla planted was 1:1:1. A floating board was placed in a tank containing wastewater from California bass farming. A nylon rope was used to connect the fixing ring to a fixing hole at the top of the tank, ensuring the floating board floated stably (in contact with the water surface, without tilting). Twelve days after the floating board was placed in the tank, the physicochemical properties of the purified water were tested, as shown in Table 1.

[0081] Comparative Example 2

[0082] Fill the tank with 0.7m of California bass aquaculture tailwater. Evenly sow the germinated barley and vanilla seeds (6 seeds per basket) onto the absorbent cotton in three planting baskets; one basket contains only barley seeds, one only vanilla seeds, and the last basket contains half barley seeds and half vanilla seeds. Cover each basket with a thin layer of quartz sand (0.5cm thick, to secure the seeds and prevent water from washing them away). Then, embed the three planting baskets into a 0.75m² area... 2 In the planting holes of the floating board (i.e., the area of ​​the floating board covering the California bass aquaculture tailwater is 75%), the planting density of barley and vanilla on the floating board is 9 plants / m². 2 The total planting density is 18 plants / m². 2The ratio of barley to vanilla planted was 1:1. A floating board was placed in a tank containing wastewater from California bass farming. A nylon rope was used to connect the fixing ring to a fixing hole at the top of the tank, ensuring the floating board floated stably (in contact with the water surface, without tilting). Twelve days after the floating board was placed in the tank, the physicochemical properties of the purified water were tested, as shown in Table 1.

[0083] Comparative Example 3

[0084] Fill the tank with 0.7m of California bass aquaculture wastewater. Evenly sow the germinated pea and vanilla seeds onto the absorbent cotton in three planting baskets (6 seeds per basket; one basket sows only pea seeds, one only vanilla seeds, and the last basket is half pea seeds and half vanilla seeds). Cover each basket with a thin layer of quartz sand (0.5cm thick, to secure the seeds and prevent water from washing them away). Then, embed the three planting baskets into a 0.75m² area... 2 In the planting holes of the floating board (i.e., the area of ​​the floating board covering the California bass aquaculture tailwater is 75%), the planting density of peas and vanilla on the floating board is 9 plants / m². 2 The total planting density is 18 plants / m². 2 The ratio of hemp peas to vanilla was 1:1. A floating board was placed in a tank containing wastewater from California bass farming. A nylon rope was used to connect the fixing ring to a fixing hole at the top of the tank, ensuring the floating board floated stably (in contact with the water surface, without tilting). Twelve days after the floating board was placed in the tank, the physicochemical properties of the purified water were tested, as shown in Table 1.

[0085] Comparative Example 4

[0086] Same as Example 1, except that the preparation steps of the carrier-immobilized composite bacterial agent are as follows:

[0087] S1. Dry the corn stalks, crush them until they can pass through a 40-mesh sieve, and then carbonize them at 450℃ for 4 hours. After carbonization, grind the carbonized product until it can pass through a 100-mesh sieve to obtain biochar.

[0088] S2. A bacterial suspension of biochar and compound microbial agent (prepared by mixing commercially available liquid microbial agents of *Nitrosomonas*, *Nitrobacterium*, *Bacillus cereus*, *Pseudomonas stolonifer*, *Bacillus licheniformis*, *Lactobacillus plantarum*, and *Rhodopseudomonas palustris* with sterile distilled water; the bacterial content of each agent in the compound microbial agent suspension is 1.0 × 10⁻⁶) 9The bacterial agent / carrier complex was mixed in an Erlenmeyer flask at a ratio of 1 g: 10 mL. The Erlenmeyer flask was placed in a constant temperature shaker (20℃, 100 rpm) and shaken for 20 h for adsorption. After the adsorption was completed, the mixture was filtered, rinsed three times with sterile physiological saline, and dried at 20℃ to obtain the bacterial agent / carrier complex.

[0089] S3. Mix polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water in a mass ratio of 5:0.3:0.3:0.2:100, heat and stir at 100℃ until it becomes colloidal, cool to room temperature and then add the bacterial agent / carrier complex (the amount of bacterial agent / carrier complex added is 15% of the sum of the mass of polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water), stir evenly to obtain a mixture; then add the mixture dropwise into a saturated boric acid solution containing 3wt% CaCl2, solidify at 5℃ for 20h, then filter, wash with water and dry at 30℃ to obtain the carrier-immobilized composite bacterial agent.

[0090] Comparative Example 5

[0091] Same as Example 1, except that the preparation steps of the carrier-immobilized composite bacterial agent are as follows:

[0092] S1. A bacterial suspension of modified biochar and compound microbial agent (prepared by mixing commercially available liquid microbial agents of *Nitrosomonas*, *Nitrobacterium*, *Bacillus cereus*, *Pseudomonas stolonifer*, *Lactobacillus plantarum*, and *Rhodopseudomonas palustris* with sterile distilled water; the bacterial suspension of compound microbial agent contains 2.0 × 10⁻⁶ *Bacillus cereus* bacteria) 9 CFU / mL, the bacterial count of other bacterial agents was 1.0 × 10⁻⁶. 9 The bacterial agent / carrier complex was mixed in an Erlenmeyer flask at a ratio of 1 g: 10 mL. The Erlenmeyer flask was placed in a constant temperature shaker (20℃, 100 rpm) and shaken for 20 h for adsorption. After the adsorption was completed, the mixture was filtered, rinsed three times with sterile physiological saline, and dried at 20℃ to obtain the bacterial agent / carrier complex.

[0093] S2. Polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water are mixed in a mass ratio of 5:0.3:0.3:0.2:100. The mixture is heated and stirred at 100°C until it becomes a colloidal state. After cooling to room temperature, the bacterial agent / carrier complex is added (the amount of bacterial agent / carrier complex added is 15% of the sum of the mass of polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water). The mixture is stirred evenly to obtain a mixture. Then, the mixture is dropped into a saturated boric acid solution containing 3wt% CaCl2 and cured at 5°C for 20 hours. After filtration, washing with water and drying at 30°C, the carrier-immobilized composite bacterial agent is obtained.

[0094] Comparative Example 6

[0095] Same as Example 1, except that the preparation steps of the carrier-immobilized composite bacterial agent are as follows:

[0096] S1. A bacterial suspension of modified biochar and compound microbial agent (prepared by mixing commercially available liquid microbial agents of *Nitrosomonas*, *Nitrobacterium*, *Bacillus licheniformis*, *Pseudomonas stolonifer*, *Lactobacillus plantarum*, and *Rhodopseudomonas palustris* with sterile distilled water; the bacterial suspension of compound microbial agent contains 2.0 × 10⁻⁶ *Bacillus licheniformis* bacteria) 9 CFU / mL, the bacterial count of other bacterial agents was 1.0 × 10⁻⁶. 9 The bacterial agent / carrier complex was mixed in an Erlenmeyer flask at a ratio of 1 g: 10 mL. The Erlenmeyer flask was placed in a constant temperature shaker (20℃, 100 rpm) and shaken for 20 h for adsorption. After the adsorption was completed, the mixture was filtered, rinsed three times with sterile physiological saline, and dried at 20℃ to obtain the bacterial agent / carrier complex.

[0097] S2. Polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water are mixed in a mass ratio of 5:0.3:0.3:0.2:100. The mixture is heated and stirred at 100°C until it becomes a colloidal state. After cooling to room temperature, the bacterial agent / carrier complex is added (the amount of bacterial agent / carrier complex added is 15% of the sum of the mass of polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water). The mixture is stirred evenly to obtain a mixture. Then, the mixture is dropped into a saturated boric acid solution containing 3wt% CaCl2 and cured at 5°C for 20 hours. After filtration, washing with water and drying at 30°C, the carrier-immobilized composite bacterial agent is obtained.

[0098] Comparative Example 7

[0099] Same as Example 1, except that the preparation steps of the carrier-immobilized composite bacterial agent are as follows:

[0100] S1. A bacterial suspension of modified biochar and compound microbial agents (prepared by mixing commercially available liquid microbial agents of *Nitrosomonas*, *Nitrobacterium*, *Bacillus cereus*, *Pseudomonas stolonifer*, *Bacillus licheniformis*, *Lactobacillus plantarum*, and *Rhodopseudomonas palustris* with sterile distilled water; the bacterial content of each agent in the bacterial suspension of the compound microbial agent is 1.0 × 10⁻⁶) 9 The bacterial agent / carrier complex was mixed in an Erlenmeyer flask at a ratio of 1 g: 10 mL. The Erlenmeyer flask was placed in a constant temperature shaker (20℃, 100 rpm) and shaken for 20 h for adsorption. After the adsorption was completed, the mixture was filtered, rinsed three times with sterile physiological saline, and dried at 20℃ to obtain the bacterial agent / carrier complex.

[0101] S2. Polyvinyl alcohol, sodium alginate, Al2(SO4)3 and water are mixed in a mass ratio of 5:0.3:0.2:100. The mixture is heated and stirred at 100°C until it becomes a colloidal state. After cooling to room temperature, the bacterial agent / carrier complex is added (the amount of bacterial agent / carrier complex added is 15% of the sum of the mass of polyvinyl alcohol, sodium alginate, Al2(SO4)3 and water). The mixture is stirred evenly to obtain a mixture. Then the mixture is dropped into a saturated boric acid solution containing 3wt% CaCl2 and cured at 5°C for 20 hours. Then it is filtered, washed with water and dried at 30°C to obtain the carrier-immobilized composite bacterial agent.

[0102] Table 1

[0103]

[0104] As shown in Table 1, the purification method provided by this invention (Examples 1-3) exhibits excellent purification effects on the wastewater from California bass farming. Compared with the initial wastewater, all key pollutant indicators were significantly reduced. This indicates that the method can achieve deep and simultaneous removal of nitrogen, phosphorus, and suspended solids.

[0105] Comparative experiments showed that the synergistic effect of plants, microorganisms, and the carrier is key to achieving efficient purification. The purification effect of Comparative Example 1 (plants only) was far inferior to that of the examples, demonstrating the limited purification capacity of a single plant. Comparative Examples 2 and 3 (incomplete plant combinations) also showed poor results, highlighting the necessity of the synergistic effect of barley, peas, and herbs. While the purification effects of Comparative Examples 4-7 (with reduced types of microbial agents or changes in the preparation method of the carrier-immobilized composite microbial agent) were better than those of Comparative Examples 1-3, they were significantly inferior to those of Examples 1-3, confirming the indispensable role of the modified biochar carrier and the complete composite microbial agent synergistic encapsulation system.

[0106] In addition, the reason why the dissolved oxygen in Example 1 is lower than that in Comparative Examples 1-3 may be because the degradation by microorganisms consumes some of the dissolved oxygen. Although the dissolved oxygen is lower, its removal effect on pollutants is far better than that in Comparative Examples 1-3. Therefore, its overall water purification effect is significantly better than that in Comparative Examples 1-3.

[0107] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for purifying wastewater from California bass farming, characterized in that, Includes the following steps: Barley, peas, and vanilla were planted in the tailwater of California bass farming, and a bulk immobilized compound microbial agent was added to the tailwater before planting the barley, peas, and vanilla. The preparation steps of the carrier-immobilized composite microbial agent include: loading the composite microbial agent into modified biochar to obtain a microbial agent / carrier composite; and encapsulating the microbial agent / carrier composite to obtain the carrier-immobilized composite microbial agent. The preparation steps of the modified biochar include: drying and crushing corn stalks, then carbonizing them at 400-500℃ for 1-3 hours to obtain biochar; soaking the biochar in magnesium sulfate solution, drying it after soaking, and then carbonizing it again at 400-500℃ for 1-3 hours to obtain the modified biochar. The compound microbial agent includes: Nitrosomonas, Nitrobacterium, Bacillus cereus, Pseudomonas Sturmea, Bacillus licheniformis, Lactobacillus plantarum, and Rhodopseudomonas palustris. The encapsulation of the bacterial agent / carrier complex includes: mixing polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water, heating and stirring until it becomes colloidal, cooling and then adding the bacterial agent / carrier complex, and then dropping it into a saturated boric acid solution containing 3-5wt% CaCl2, and curing at low temperature for 20-24 hours to obtain the carrier-immobilized composite bacterial agent; The method of planting barley, peas, and vanilla in the tailwater of California bass farming includes: evenly sowing germinated barley, pea, and vanilla seeds in a planting basket, then embedding the planting basket into the planting holes of a floating board, and then floating the floating board on the surface of the California bass farming tailwater; the planting ratio of barley, peas, and vanilla is 1:1:

1.

2. The method for purifying the wastewater from California bass farming as described in claim 1, characterized in that, The concentration of the magnesium sulfate solution is 0.5-1.0 mol / L; And / or, the ratio of the biochar to the magnesium sulfate solution is 1g:20-30mL; And / or, the soaking treatment is performed at a temperature of 40-50°C for 1-3 hours.

3. The method for purifying the wastewater from California bass farming as described in claim 1, characterized in that, The process of loading the composite microbial agent into modified biochar includes: mixing the modified biochar and the bacterial suspension of the composite microbial agent, shaking and adsorbing for 20-24 hours, and then filtering, washing, and drying to obtain the microbial agent / carrier composite.

4. The method for purifying the wastewater from California bass farming as described in claim 3, characterized in that, The bacterial content of each agent in the bacterial suspension of the compound microbial agent is 1.0 × 10⁻⁶. 9 -5.0×10 9 CFU / mL; And / or, the ratio of the modified biochar to the bacterial suspension of the composite bacterial agent is 1g:10-20mL; And / or, the temperature of the oscillation adsorption is 20-30℃, and the vibration speed is 100-200rpm.

5. The method for purifying the wastewater from California bass farming as described in claim 1, characterized in that, The mass ratio of polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3, and water is 5-8:0.3-0.5:0.3-0.5:0.2-0.4:

100. And / or, the heating and stirring temperature is 90-100℃; And / or, the amount of the bacterial agent / carrier complex added is 15-25% of the sum of the mass of the polyvinyl alcohol, sodium alginate, chitosan, Al2(SO4)3 and water; And / or, the low-temperature curing temperature is 5-10℃.

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