A method for removing organic pollutants based on an algae-bacteria symbiotic system

Abstract

This invention belongs to the field of wastewater treatment, specifically relating to a method for removing organic pollutants based on an algae-bacterial symbiotic system. The method involves passing organic pollutant-laden wastewater through a symbiotic treatment pond, in which aquatic plants, functional algae, and microorganisms on biochar are planted. These aquatic plants, functional algae, and functional microorganisms on the biochar together constitute a grass-algae-bacterial symbiotic system. The functional algae are a mixture of *Scenedesmus niger*, *Microcystis aeruginosa*, and *Chlorella vulgaris*, while the functional microorganisms on the biochar are a mixture of *Arthrobacter*, *Pseudomonas*, *Microbacterium*, and *Acidobacterium*. This invention uses a grass-algae-bacterial symbiotic system to treat wastewater, achieving a high organic pollutant removal rate. The mutually beneficial symbiotic relationship among the three components helps maintain the stability of the symbiotic system, and the entire system is easy to construct. Furthermore, it reduces operating costs and avoids secondary pollution to the environment.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for removing organic pollutants based on an algae-bacteria symbiotic system. Background Technology

[0002] With the rapid increase in the number of urban wastewater treatment plants, the problem of the recalcitrant degradation of macromolecular organic matter and new pollutants in the effluent is receiving increasing attention. These organic substances are difficult to treat effectively in wastewater treatment plants using traditional physical and chemical methods, and the discharge of such organic wastewater poses serious environmental pollution and health risks. Therefore, researching how to efficiently treat wastewater containing macromolecular organic matter is of significant practical importance.

[0003] Currently, wastewater treatment for macromolecular organic pollutants still has the following shortcomings: (1) Limited treatment efficiency: Macromolecular organic pollutants have complex structures and high stability, and traditional physical and chemical treatment methods are not very effective at removing them. Current treatment technologies have limited treatment efficiency when treating macromolecular organic pollutants and are difficult to completely remove these pollutants. (2) High energy consumption: Current macromolecular organic wastewater treatment methods often require a large amount of energy input, such as high pressure and high temperature, in order to achieve efficient removal, which leads to high energy consumption in the treatment process and does not meet the requirements of sustainable development. (3) High technical cost: Current macromolecular organic wastewater treatment technologies usually require the use of expensive materials, equipment and reagents, resulting in high treatment costs. (4) Generation of intermediate products: Some treatment methods may generate some difficult-to-degrade intermediate products when treating macromolecular organic pollutants, which may pose a risk of secondary pollution to the environment. (5) Lack of targeted treatment methods: Different types of macromolecular organic pollutants have different structures and properties and require targeted treatment methods, but current treatment technologies are often general and difficult to effectively treat different pollutants.

[0004] While some progress has been made, there are still shortcomings in the treatment of wastewater containing macromolecular organic pollutants. Future research needs to focus on improving treatment efficiency, reducing energy consumption and technology costs, avoiding the generation of intermediate products, and developing targeted treatment methods to achieve more efficient, economical, and sustainable treatment technologies. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for removing organic pollutants based on an algae-bacteria symbiotic system, which can effectively decompose macromolecular organic matter in wastewater and reduce overall costs while ensuring wastewater purification.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An organic pollutant removal method based on an algae-bacterial symbiotic system involves passing organic pollutant effluent through a symbiotic treatment pond. The symbiotic treatment pond contains aquatic plants, functional algae, and microorganisms on biochar. The aquatic plants, functional algae, and functional microorganisms on the biochar together constitute a grass-algae-bacterial symbiotic system.

[0008] The functional algae are composed of a mixture of Scenedesmus acuminata, Microcystis aeruginosa, and Chlorella vulgaris, and are used to remove macromolecular pollutants such as PFAS and aromatic hydrocarbons from the water. The functional microorganisms carried on the biochar are composed of a mixture of Arthrobacter, Pseudomonas, Microbacteria, and Acidobacteria, and are used to degrade macromolecular organic matter in wastewater, such as PFOA and PFOS.

[0009] Furthermore, the symbiotic treatment pond has a water depth of 3m, a hydraulic retention time of 8h, and a water flow velocity of 500m / s. 3 / d, operating temperature is 20-25℃.

[0010] Furthermore, the volume ratio of the released Scenedesmus acuminata, Microcystis aeruginosa, and Chlorella vulgaris is 1.5–2.0:1.5–2.0:1.5–2.0, and the release amount is 500,000 cells / L.

[0011] Furthermore, the ratio of Arthrobacter:Pseudomonas:Microbacterium:AcidMicrobe on the biochar is 3-5:3-4:5-6:5-7, and the amount of biochar used to carry the microorganisms is 10 kg / m³. 3 .

[0012] Furthermore, the aquatic plants are a variety of wetland plants, emergent plants, floating-leaved plants, and submerged plants; wetland plants can be cattails, canna lilies, reeds, etc.; emergent plants can be shiitake mushroom grass, water onion, loosestrife, etc.; floating-leaved plants can be lotus, lotus, etc.; submerged plants can be goldfish algae, foxtail algae, eelgrass, etc.

[0013] Furthermore, 15-20g of modified biochar, 1mL of bacterial strain, 2g of urea, 3.2g of glucose, 2.5g of sodium chloride, and 3g of dipotassium hydrogen phosphate were added to 1L of distilled water and dissolved completely. Then, acetate starch and glucono-delta-lactone were added until saturated. After stirring evenly, the mixture was kept for 3-5 hours to solidify. Finally, it was made into units of equal volume and stored at room temperature. Urea, glucose, sodium chloride, and dipotassium hydrogen phosphate can provide nutrients for the early growth of microorganisms.

[0014] Furthermore, the method for preparing the modified biochar is as follows:

[0015] S1: Harvest aquatic plants and react them at 200℃~250℃ and 50bar for 10 hours. Then, process them into hydrothermal biochar using hydrothermal carbonization technology. After grinding, pass the biochar through a 100-mesh sieve to obtain hydrothermal biochar powder. The modified biochar used is made from aquatic plants, realizing the resource utilization of aquatic plants.

[0016] S2: Soak hydrothermal biochar powder in a 0.5 mol / L sodium bicarbonate solution, heat to 50°C and stir constantly. After 2 hours, rinse with clean water, filter and dry to obtain modified biochar powder A.

[0017] S3: Modified biochar powder A, 4-diacetol, ethyl phenoxyacetate, gallium oxide, and nano iron powder are added to a mixer in a mass ratio of 15:5:3:1:1 and stirred for 30 minutes to obtain modified biochar powder B. Gallium oxide, which is used in biochar modification, has multiple oxidation states and can serve as an active center to increase the chemical functional groups of biochar and improve its activity. Nano iron acts as a catalyst to promote the pyrolysis of macromolecular organic matter in biochar raw materials, forming more micropores, thereby increasing the porosity and specific surface area of ​​biochar.

[0018] S4: Mix the mixture with deionized water at a ratio of 1:5 to 7 and place it in a closed pressure vessel to synthesize modified biochar C at a temperature of 200 to 250°C;

[0019] S5: Take 20g of modified biochar C from S4 and add it to 1L of bamboo vinegar. Distill under reduced pressure for 1 hour using equipment such as a rotary evaporator, water bath, and water circulation vacuum pump. After drying, the modified biochar is obtained. Bamboo vinegar has strong antioxidant properties. Modifying biochar with bamboo vinegar can improve its stability and durability.

[0020] Furthermore, the nano-iron powder refers to iron particles with a particle size between 1 nm and 100 nm, and the bamboo vinegar is refined bamboo vinegar after removing tar.

[0021] Furthermore, the symbiotic treatment pond is also equipped with an aeration system and a dissolved oxygen monitoring device. The dissolved oxygen monitoring device monitors the dynamics of dissolved oxygen in the water in real time and controls the dissolved oxygen in the water to be between 2.0 and 4.0 mg / L. The nano-aeration system uses aeration pipes with nanopore size to form tiny bubbles that form a mist in the overlying water, without disturbing the bottom sediment.

[0022] Furthermore, since some microorganisms, such as microacid bacteria, need to be artificially cultivated and domesticated before they can adapt to the wild environment, functional algae and functional microorganisms need to be cultivated and domesticated on land for a period of time before being added to the water. The specific cultivation and domestication steps are as follows:

[0023] Functional microorganisms and algae were cultured in agar medium, and a light-dark alternation environment of 16 hours of light and 8 hours of darkness was set. After one month of culture, they were successively transferred to wastewater diluted 10 times, 5 times, and 2 times, and acclimated for 5 days each. The treated wastewater was tested. If the treatment efficiency of the target pollutant was greater than 60%, the culture and acclimation were completed, and the wastewater could be put into the water body of the symbiotic treatment pond.

[0024] The beneficial effects of this invention are:

[0025] This invention employs a multifunctional algae system and a multifunctional microbial system, together with aquatic plants, to construct a grass-algae-bacteria symbiotic system. Using this system to treat wastewater achieves a high organic pollutant removal rate. The synergistic and mutually beneficial interaction of the three systems helps maintain the stability of the symbiotic system, and the entire system is easy to construct. It also reduces operating costs and avoids secondary pollution to the environment.

[0026] The grass-algae-bacteria symbiotic system constructed using the method of this invention can effectively decompose macromolecular organic matter in wastewater. Furthermore, the oxygen produced by algae photosynthesis can increase the dissolved oxygen content in the water, and the low-molecular-weight organic matter from photosynthetic carbon fixation products can also provide a carbon source for microorganisms that decompose macromolecular organic pollutants. While ensuring wastewater purification, it reduces overall costs and provides maximum convenience for subsequent treatment. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0028] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention. Detailed Implementation

[0029] 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 the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art are within the scope of protection of the present invention.

[0030] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0031] Example 1

[0032] An organic pollutant removal method based on an algae-bacterial symbiotic system involves passing organic pollutant effluent through a symbiotic treatment pond. The symbiotic treatment pond contains aquatic plants, functional algae, and microorganisms on biochar. The aquatic plants, functional algae, and functional microorganisms on the biochar together constitute a grass-algae-bacterial symbiotic system.

[0033] The functional algae are a mixture of Scenedesmus acuminate, Microcystis aeruginosa, and Chlorella vulgaris. The functional microorganisms mounted on biochar are a mixture of Arthrobacter, Pseudomonas, Microbacteria, and Acidobacteria. The functional algae are used to remove large molecular pollutants such as PFAS and aromatic hydrocarbons from the water. The functional microorganisms mounted on biochar are a mixture of Arthrobacter, Pseudomonas, Microbacteria, and Acidobacteria to degrade large molecular organic matter in wastewater, such as PFOA and PFOS. This further decomposes large, recalcitrant organic matter in wastewater into smaller molecules, facilitating subsequent treatment. The biochar is loose and porous, and the modified biochar provides a good growth space for the functional microorganisms. The functional microorganisms are screened and cultivated.

[0034] The effectiveness of a single type of algae or bacteria in treating different pollutants in water is limited. This invention, through the screening of three types of algae and four types of bacteria, achieves a greater treatment effect on wastewater than the sum of the purification effects of a single type of algae or bacteria. Effective purification of organic pollutant effluent is achieved by combining a small number of algae and bacteria. At the same time, the smaller number of types of bacteria and algae means that they are easier to cultivate. The mutualistic symbiotic relationship between different algae and bacteria maintains the stability of the algae or microbial system. Meanwhile, the presence of aquatic plants can limit the large-scale reproduction of algae and prevent algal blooms, thus ensuring the long-term operation of the grass-algae-bacteria symbiotic system of this application.

[0035] Furthermore, the symbiotic treatment pond has a water depth of 3m, a hydraulic retention time of 8h, and a water flow velocity of 500m / s. 3 / d, operating temperature is 20-25℃.

[0036] Furthermore, the volume ratio of the released Scenedesmus acuminata, Microcystis aeruginosa, and Chlorella vulgaris is 1.5–2.0:1.5–2.0:1.5–2.0, and the release amount is 500,000 cells / L.

[0037] Furthermore, the ratio of Arthrobacter:Pseudomonas:Microbacterium:AcidMicrobe on the biochar is 3-5:3-4:5-6:5-7, and the amount of biochar used to carry the microorganisms is 10 kg / m³. 3 .

[0038] Furthermore, the aquatic plants are a variety of wetland plants, emergent plants, floating-leaved plants, and submerged plants; the symbiotic treatment pond includes at least two different types of aquatic plants; wetland plants can be cattails, canna lilies, reeds, etc.; emergent plants can be shiitake mushroom grass, water onions, loosestrife, etc.; floating-leaved plants can be lotus, water lilies, etc.; submerged plants can be goldfish algae, foxtail algae, eelgrass, etc.; there are no special requirements for the planting substrate of aquatic plants.

[0039] Furthermore, 15-20g of modified biochar, 1mL of bacterial strain, 2g of urea, 3.2g of glucose, 2.5g of sodium chloride, and 3g of dipotassium hydrogen phosphate were added to 1L of distilled water and dissolved completely. Then, acetate starch and glucono-delta-lactone were added until saturation. After stirring evenly, the mixture was kept for 3-5 hours to solidify. Finally, it was made into units of equal volume and stored at room temperature.

[0040] Furthermore, the method for preparing the modified biochar is as follows:

[0041] S1: Harvest aquatic plants and react them at 200℃~250℃ and 50bar for 10 hours. Then, process them into hydrothermal biochar using hydrothermal carbonization technology. After grinding, pass the biochar through a 100-mesh sieve to obtain hydrothermal biochar powder. The modified biochar used is made from aquatic plants, realizing the resource utilization of aquatic plants.

[0042] S2: Soak hydrothermal biochar powder in a 0.5 mol / L sodium bicarbonate solution, heat to 50°C and stir constantly. After 2 hours, rinse with clean water, filter and dry to obtain modified biochar powder A.

[0043] S3: Modified biochar powder A, 4-diacetol, ethyl phenoxyacetate, gallium oxide, and nano iron powder are added to a mixer in a mass ratio of 15:5:3:1:1 and stirred for 30 minutes to obtain modified biochar powder B. Gallium oxide, which is used in biochar modification, has multiple oxidation states and can serve as an active center to increase the chemical functional groups of biochar and improve its activity. Nano iron acts as a catalyst to promote the pyrolysis of macromolecular organic matter in biochar raw materials, forming more micropores, thereby increasing the porosity and specific surface area of ​​biochar.

[0044] S4: Mix the mixture with deionized water at a ratio of 1:5 to 7 and place it in a closed pressure vessel to synthesize modified biochar C at a temperature of 200 to 250°C;

[0045] S5: Take 20g of modified biochar C from S4 and add it to 1L of bamboo vinegar. Distill under reduced pressure for 1 hour using equipment such as a rotary evaporator, water bath, and water circulation vacuum pump. After drying, the modified biochar is obtained. Bamboo vinegar has strong antioxidant properties. Modifying biochar with bamboo vinegar can improve its stability and durability. Biochar is loose and porous, which is an excellent place for microbial survival. After modification with 4-diacetol, ethyl phenoxyacetate, gallium oxide, and nano iron, the strength of the biochar skeleton can be enhanced.

[0046] Furthermore, the nano-iron powder refers to iron particles with a particle size between 1 nm and 100 nm, and the bamboo vinegar is refined bamboo vinegar after removing tar.

[0047] Furthermore, the symbiotic treatment pond is also equipped with an aeration system and a dissolved oxygen monitoring device. The dissolved oxygen monitoring device monitors the dynamics of dissolved oxygen in the water in real time and controls the dissolved oxygen in the water to be between 2.0 and 4.0 mg / L. The nano-aeration system uses aeration pipes with nanopore size to form tiny bubbles that form a mist in the overlying water, without disturbing the bottom sediment.

[0048] Furthermore, since some microorganisms, such as microacid bacteria, need to be artificially cultivated and domesticated before they can adapt to the wild environment, functional algae and functional microorganisms need to be cultivated and domesticated on land for a period of time before being added to the water. The specific cultivation and domestication steps are as follows:

[0049] Functional microorganisms and algae were cultured in agar medium, and a light-dark alternation environment of 16 hours of light and 8 hours of darkness was set. After one month of culture, they were successively transferred to wastewater diluted 10 times, 5 times, and 2 times, and acclimated for 5 days each. The treated wastewater was tested. If the treatment efficiency of the target pollutant was greater than 60%, the culture and acclimation were completed, and the wastewater could be put into the water body of the symbiotic treatment pond.

[0050] Wastewater treatment plants typically discharge effluent with high total nitrogen, low organic carbon, and a low C / N ratio, making it unsuitable for microbial growth. This invention targets effluent containing novel and macromolecular organic pollutants. By screening and cultivating functional algae, a multifunctional algae system is constructed to enrich and absorb macromolecular pollutants such as PFASs and aromatic hydrocarbons in the wastewater, further purifying the water. Simultaneously, the photosynthesis of algae generates oxygen, increasing dissolved oxygen in the water. The low-molecular-weight organic matter produced by photosynthesis can provide a carbon source for microorganisms that decompose macromolecular organic pollutants. The treatment effect of a single type of algae or bacteria on different pollutants in water is limited. This invention, through the screening of three types of algae and four types of bacteria, achieves a wastewater treatment effect greater than the sum of the purification effects of a single type of algae or bacteria. Effective purification of organic pollutant effluent is achieved through a combination of a relatively small number of algae and bacteria. Furthermore, the smaller number of algae and bacteria species means that the algae and bacteria are easier to cultivate, making the entire system easier to construct.

[0051] In one specific embodiment, the ratio of functional algae added is Scenedesmus acuminata: Microcystis aeruginosa: Chlorella vulgaris = 2:1.5:1.5, and the ratio of functional microorganisms added is Arthrobacter: Pseudomonas: Microbacteria: Acidobacteria = 4:3:5:6.

[0052] In this specific embodiment, the preparation method of modified biochar is as follows:

[0053] S1: Harvest aquatic plants, react them at 200℃ and 50 bar for 10 hours, and then process them into hydrothermal biochar using hydrothermal carbonization technology. After grinding, the biochar powder is obtained by passing it through a 100-mesh sieve.

[0054] S2: Soak hydrothermal biochar powder in a 0.5 mol / L sodium bicarbonate solution, heat to 50°C and stir constantly. After 2 hours, rinse with clean water, filter and dry to obtain modified biochar powder A.

[0055] S3: Add modified biochar powder A, 4-diacetol, ethyl phenoxyacetate, gallium oxide, and nano iron powder to a mixer in a mass ratio of 15:5:3:1:1 and mix thoroughly for 30 minutes to obtain modified biochar powder B.

[0056] S4: Mix the mixture with deionized water at a ratio of 1:5 and place it in a closed pressure vessel to synthesize modified biochar C at a temperature of 200℃;

[0057] S5: Take 20g of modified biochar C from S4 and add it to 1L of bamboo vinegar. Distill under reduced pressure for 1 hour using equipment such as a rotary evaporator, water bath, and water circulation vacuum pump. After drying, the modified biochar is obtained.

[0058] In one specific embodiment, the preparation steps of the microbial-loaded biochar are as follows: 15g of modified biochar, 1mL of bacterial strain, 2g of urea, 3.2g of glucose, 2.5g of sodium chloride, and 3g of dipotassium hydrogen phosphate are added to 1L of distilled water and fully dissolved. Then, acetate starch and glucono-delta-lactone are added until saturated. After stirring evenly, the mixture is kept for 3 hours to solidify. Finally, it is made into units of the same size and stored at room temperature. The resulting product is microbial-loaded biochar.

[0059] Example 2

[0060] In this embodiment, the ratio of functional algae is Scenedesmus acuminata: Microcystis aeruginosa: Chlorella vulgaris = 1.5: 2.0: 1.5, and the ratio of functional microorganisms is Arthrobacter: Pseudomonas: Microbacteria: Acidobacteria = 3: 4: 6: 5.

[0061] In this specific embodiment, the preparation method of modified biochar is as follows:

[0062] S1: Harvest aquatic plants, react them at 250℃ and 50 bar for 10 hours, and then process them into hydrothermal biochar using hydrothermal carbonization technology. After grinding, the biochar powder is obtained by passing it through a 100-mesh sieve.

[0063] S2: Soak hydrothermal biochar powder in a 0.5 mol / L sodium bicarbonate solution, heat to 50°C and stir constantly. After 2 hours, rinse with clean water, filter and dry to obtain modified biochar powder A.

[0064] S3: Add modified biochar powder A, 4-diacetol, ethyl phenoxyacetate, gallium oxide, and nano iron powder to a mixer in a mass ratio of 15:5:3:1:1 and mix thoroughly for 30 minutes to obtain modified biochar powder B.

[0065] S4: Mix the mixture with deionized water at a ratio of 1:5 and place it in a closed pressure vessel to synthesize modified biochar C at a temperature of 200℃;

[0066] S5: Take 20g of modified biochar C from S4 and add it to 1L of bamboo vinegar. Distill under reduced pressure for 1 hour using equipment such as a rotary evaporator, water bath, and water circulation vacuum pump. After drying, the modified biochar is obtained.

[0067] In this embodiment, the preparation steps of the microbial-loaded biochar are as follows: 20g of modified biochar, 1mL of bacterial strain, 2g of urea, 3.2g of glucose, 2.5g of sodium chloride, and 3g of dipotassium hydrogen phosphate are added to 1L of distilled water and fully dissolved. Then, acetate starch and glucono-delta-lactone are added until saturated. After stirring evenly, the mixture is kept for 4 hours to solidify. Finally, it is made into units of the same size and stored at room temperature. The resulting product is microbial-loaded biochar.

[0068] Example 3

[0069] In this embodiment, the ratio of functional algae is Scenedesmus acuminata: Microcystis aeruginosa: Chlorella vulgaris = 1.5: 1.5: 2.0, and the ratio of functional microorganisms is Arthrobacter: Pseudomonas: Microbacteria: Acidobacteria = 5: 3: 6: 7.

[0070] In this specific embodiment, the preparation method of modified biochar is as follows:

[0071] S1: Harvest aquatic plants and react them at 220℃ and 50 bar for 10 hours. Then, process them into hydrothermal biochar using hydrothermal carbonization technology. Grind the biochar and pass it through a 100-mesh sieve to obtain hydrothermal biochar powder.

[0072] S2: Soak hydrothermal biochar powder in a 0.5 mol / L sodium bicarbonate solution, heat to 50°C and stir constantly. After 2 hours, rinse with clean water, filter and dry to obtain modified biochar powder A.

[0073] S3: Add modified biochar powder A, 4-diacetol, ethyl phenoxyacetate, gallium oxide, and nano iron powder to a mixer in a mass ratio of 15:5:3:1:1 and mix thoroughly for 30 minutes to obtain modified biochar powder B.

[0074] S4: Mix the mixture with deionized water at a ratio of 1:7 and place it in a sealed pressure vessel to synthesize modified biochar C at a temperature of 200℃.

[0075] S5: Take 20g of modified biochar C from S4 and add it to 1L of bamboo vinegar. Distill under reduced pressure for 1 hour using equipment such as a rotary evaporator, water bath, and water circulation vacuum pump. After drying, the modified biochar is obtained.

[0076] In this embodiment, the preparation steps of the microbial-loaded biochar are as follows: 20g of modified biochar, 1mL of bacterial strain, 2g of urea, 3.2g of glucose, 2.5g of sodium chloride, and 3g of dipotassium hydrogen phosphate are added to 1L of distilled water and fully dissolved. Then, acetate starch and glucono-delta-lactone are added until saturation. After stirring evenly, the mixture is kept for 5 hours to solidify. Finally, it is made into units of the same size and stored at room temperature. The resulting product is microbial-loaded biochar.

[0077] Comparative Example

[0078] Examples 1 to 3 were used as three control groups to conduct a comparative experiment on wastewater treatment:

[0079] Control group 1 involved treating wastewater with only functional algae, without adding microorganisms, biochar, or aquatic plants;

[0080] Control group 2 used only unmodified ordinary biochar to construct a functional microbial system to treat wastewater, without adding functional algae and aquatic plants;

[0081] Control group 3 used only aquatic plants to treat wastewater, without adding functional algae and microorganisms carried on biochar;

[0082] The conditions for wastewater treatment are: the flow velocity of the effluent from the wastewater treatment plant is 0.5 m / s, and the hydraulic retention time is 8 hours.

[0083] The sampling and testing items before and after wastewater treatment included PFASs (per- and polyfluoroalkyl substances), PFOA (perfluorooctanoic acid), PFOS (perfluorooctane sulfonate), polybrominated diphenyl ethers, EDCs (endocrine disruptors), and phthalates. The experimental data obtained are shown in Table 1.

[0084] Table 1. Removal rates of various items from wastewater samples before and after treatment.

[0085]

[0086] Table 1 shows that the removal rates of wastewater treated individually by control groups 1, 2, and 3 were relatively low. The combined removal rates of PFASs, PFOA, PFOS, polybrominated diphenyl ethers, EDCs, and phthalates from control groups 1, 2, and 3 were 79.3%, 61.7%, 79.1%, 75.7%, 62.3%, and 63.9%, respectively. This indicates that the present invention has a high removal efficiency for organic pollutants in wastewater, while microbial systems constructed from algae, aquatic plants, or unmodified biochar have poor removal effects on organic matter. Table 2 shows the changes in the combined removal rates of each example compared to the three control groups.

[0087] Table 2 shows the changes in removal rate of each embodiment compared to the three control groups.

[0088]

[0089] As shown in Table 2, the variation in removal rate of each embodiment compared to the three control groups ranged from 10.4% to 31.9%. This indicates that the wastewater treatment effect of the grass-algae-bacteria symbiotic system is significantly greater than the combined effect of the individual wastewater treatment of grass, algae, and unmodified ordinary biochar-based functional microbial systems, achieving a very high organic pollutant removal rate. It also indicates that by modifying the biochar, enhancing its porosity, stability, and antioxidant properties, a better living environment is provided for the microorganisms. This invention utilizes functional algae, functional microorganisms, and aquatic plants to construct a grass-algae-bacteria symbiotic system, and by leveraging the combined properties of these three elements, significantly improves the removal rate of organic pollutants.

[0090] It is understood that the above description is merely exemplary and the embodiments of this application are not intended to limit the scope of the invention. The above description is only a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A method for removing organic pollutants based on an algae-bacteria symbiotic system, characterized in that: The wastewater containing organic pollutants flows through a symbiotic treatment pond, which is planted with aquatic plants, functional algae, and microorganisms on biochar. The aquatic plants, functional algae, and functional microorganisms on the biochar together constitute a grass-algae-bacteria symbiotic system. The functional algae are composed of a mixture of Scenedesmus acuminata, Microcystis aeruginosa, and Chlorella vulgaris, and the functional microorganisms carried on biochar are composed of a mixture of Arthrobacter, Pseudomonas, Microbacterium, and Acidobacterium. The preparation steps of the microorganism-loaded biochar are as follows: 15-20g of modified biochar, 1mL of bacterial strain, 2g of urea, 3.2g of glucose, 2.5g of sodium chloride, and 3g of dipotassium hydrogen phosphate are added to 1L of distilled water and fully dissolved. Then, acetate starch and glucono-delta-lactone are added until saturated. After stirring evenly, it is kept for 3-5 hours to solidify. Finally, it is made into units of the same volume and stored at room temperature. The modified biochar is prepared as follows: S1: Harvest aquatic plants and react them at 200℃~250℃ and 50bar for 10h. Then, process them into hydrothermal biochar using hydrothermal carbonization technology. Grind the biochar and pass it through a 100-mesh sieve to obtain hydrothermal biochar powder. S2: Soak hydrothermal biochar powder in a 0.5 mol / L sodium bicarbonate solution, heat to 50°C and stir constantly. After 2 hours, rinse with clean water, filter and dry to obtain modified biochar powder A. S3: Add modified biochar powder A, 4-diacetol, ethyl phenoxyacetate, gallium oxide, and nano iron powder to a mixer in a mass ratio of 15:5:3:1:1 and mix thoroughly for 30 minutes to obtain modified biochar powder B. S4: Mix the mixture with deionized water at a ratio of 1:5 to 7 and place it in a closed pressure vessel to synthesize modified biochar C at a temperature of 200 to 250°C; S5: Take 20g of modified biochar C from S4 and add it to 1L of bamboo vinegar. Distill under reduced pressure for 1 hour using a rotary evaporator, water bath, and water circulation vacuum pump. After drying, the modified biochar is obtained.

2. The method for removing organic pollutants based on an algae-bacteria symbiotic system according to claim 1, characterized in that: The symbiotic treatment pond has a water depth of 3m, a hydraulic retention time of 8h, and a water flow velocity of 500m / s. 3 / d, operating temperature is 20-25℃.

3. The method for removing organic pollutants based on an algae-bacteria symbiotic system according to claim 1, characterized in that: The volume ratio of the *Scenedesmus acuminata*, *Microcystis aeruginosa*, and *Chlorella vulgaris* added was 1.5–2.0:1.5–2.0:1.5–2.0, and the addition amount was 500,000 cells / L.

4. The method for removing organic pollutants based on an algae-bacteria symbiotic system according to claim 1, characterized in that: The ratio of Arthrobacterium:Pseudomonas:Microbacterium:AcidMicrobe on biochar is 3-5:3-4:5-6:5-7, and the amount of biochar on which the microorganisms are loaded is 10 kg / m³. 3 .

5. The method for removing organic pollutants based on an algae-bacteria symbiotic system according to claim 1, characterized in that: The aquatic plants mentioned are a variety of plants including wetland plants, emergent plants, floating-leaved plants, and submerged plants.

6. The method for removing organic pollutants based on an algae-bacteria symbiotic system according to claim 1, characterized in that: The nano iron powder refers to iron particles with a particle size between 1 nm and 100 nm, and the bamboo vinegar is refined bamboo vinegar after removing tar.

7. The method for removing organic pollutants based on an algae-bacteria symbiotic system according to claim 1, characterized in that: The symbiotic treatment pond is also equipped with an aeration system and dissolved oxygen monitoring equipment. The dissolved oxygen monitoring equipment monitors the dynamics of dissolved oxygen in the water in real time and controls the dissolved oxygen in the water to be between 2.0 and 4.0 mg / L.

8. The method for removing organic pollutants based on an algae-bacteria symbiotic system according to claim 1, characterized in that: Functional algae and microorganisms are cultured and acclimatized on land for a period of time before being introduced into the water. The specific cultivation and acclimatization steps are as follows: Functional microorganisms and algae were cultured in agar medium, and a light-dark alternation environment of 16 hours of light and 8 hours of darkness was set. After one month of culture, they were successively transferred to wastewater diluted 10 times, 5 times, and 2 times, and acclimated for 5 days each. The treated wastewater was tested. If the treatment efficiency of the target pollutant was greater than 60%, the culture and acclimation were completed, and the wastewater could be put into the water body of the symbiotic treatment pond.

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