A method for treating bacterial and algal wastewater and a functional carrier material for treating bacterial and algal wastewater

Abstract

This invention discloses a method for treating wastewater using bacteria and algae, and a functional carrier material for such treatment. The method comprises the following steps: adding the functional carrier material to a bacterial-algae system, using wastewater as the reaction solution, and treating the wastewater under natural light and in a closed, non-aerated environment. The functional carrier material includes a metal-organic framework (MOF), carbon quantum dots, and a fixation carrier. The MOF uses iron and zinc as metals and trimesic acid as an organic ligand. The carbon quantum dots are made from recovered bacterial and algae biomass from the wastewater treatment system. The fixation carrier is any one of polyurethane sponge, nylon mesh, cotton cloth, or polyester fiber. This method for treating wastewater using a bacterial-algae system increases CO2 enrichment and solar spectrum absorption in the water, providing a favorable environment for microalgal photosynthetic carbon fixation and carbon-oxygen exchange between bacteria and algae, thereby improving the overall system's organic matter degradation and carbon fixation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment / carbon fixation, and in particular to a method for treating bacteria and algae sewage and a functional carrier material for treating bacteria and algae sewage. Background Art

[0002] At present, the biological treatment method for urban sewage treatment is still mainly based on the activated sludge method. As a high-carbon emission industry, it is estimated that its total carbon emissions account for 1-3% of the total social total. In addition to electricity consumption, traditional sewage treatment processes produce a large amount of CO2 released into the atmosphere during the biological stage of organic pollutant degradation. In the current dual-carbon context, the sewage treatment industry has a great demand for low-carbon emission or even zero / negative carbon emission carbon reduction and carbon fixation sewage treatment technology.

[0003] The bacteria-algae system is a promising sewage treatment technology that uses the symbiosis between microalgae and bacteria to treat sewage. In the bacteria-algae symbiotic system, microalgae fix the CO2 produced by bacteria degrading organic matter through their own growth metabolism dominated by photosynthesis. At the same time, the O2 produced by photosynthesis can be provided to heterotrophic bacteria for respiration, reducing CO2 emissions while reducing the sewage treatment system's demand for high-energy aeration. Therefore, from the perspective of biological carbon fixation and energy conservation, the bacteria-algae system is expected to achieve low-carbon development in the sewage treatment industry.

[0004] Although the symbiosis between bacteria and algae in theory has a good carbon and oxygen material exchange effect, there are still two problems in the actual process: First, the CO2 produced by bacteria degrading organic matter diffuses to the surrounding of microalgae through the concentration gradient in the water, and the diffusion rate is low, but at the same time, the rate of CO2 released into the air from the water is fast, so most of the CO2 in the water is released into the air, while the CO2 concentration in the water environment around the microalgae is low, and the absorption and biotransformation efficiency of CO2 by microalgae is low; second, only a small part of the wavelength band (red light and blue-violet light) in the sunlight spectrum is suitable for microalgae to absorb CO2 photosynthesis, and there is a partial loss of sunlight after filtering and refraction by the wall of the biological reactor, which also causes the insufficient utilization of sunlight by microalgae photosynthesis. The above two reasons lead to the low efficiency of CO2 produced by bacteria degrading organic matter in the bacteria-algae system being absorbed and biotransformed by algae, limiting the application efficiency of the bacteria-algae system as a carbon reduction technology in urban sewage treatment.

[0005] In order to alleviate the limitation of low CO2 concentration in the environment surrounding microalgae, enriching CO2 in water and accelerating its absorption and conversion is an effective method. MOF materials have application potential in the field of CO2 gas adsorption due to their porous structure, high specific surface area and other advantages, but the current CO2 adsorption materials are generally limited to gas phase environment and physical environment. For example, patent CN202180068170.1 discloses the grafting of tetraamine ligands onto magnesium-based metal organic frameworks for CO2 capture, and the MOF material in the invention is used to remove CO2 from combustion air; patent CN202111003353.3 discloses the preparation and application of a metal organic framework material MOF-74, 2,5-dihydroxyterephthalic acid as an organic ligand, cobalt nitrate, nickel nitrate, cerium nitrate, copper nitrate, and zinc nitrate as metal salts, and the prepared MOF material is used for CO2 adsorption; the MOF materials in the above series of related patents are all used for CO2 adsorption in gas phases and physical environments such as industrial or combustion air at room temperature and pressure, and do not involve whether it has good biocompatibility after combining with a microbial system and whether it can play an excellent effect in the aqueous phase. At present, the research on the adsorption of CO2 by MOF materials is mostly applied in the gas phase, less in the aqueous phase, and most MOF materials are biotoxic and have poor biocompatibility. It is necessary to develop efficient and friendly functional materials in the aqueous biological carbon fixation system.

[0006] Patent CN202211277247.9 discloses a microalgae culture medium containing a self-assembled CO2 capture material, and a preparation method and application thereof. The self-assembled CO2 capture material contained in the microalgae culture medium refers to at least one of a metal-organic framework material, a molecular sieve, a carbon material, and a porous adsorbent, wherein the metal-organic framework material comprises NH2-MIL-101(Fe), NH2-MIL-53(Fe), MIL-101-Fe, MIL-101-Cr, MIL-88-Fe, and MIL-88-Cr, and the carbon material comprises at least one of activated carbon, graphene, carbon nanotubes, and fullerenes. The invention configures the above-mentioned materials as CO2 adsorbents into a microalgae culture medium. The culture process requires continuous air aeration and subsequent microalgae harvesting requires centrifugation, which increases the cost of the culture process.

[0007] Patent CN202410078293.9 discloses a method for cultivating and fixing microalgae by adding Zn / Fe-MOFs nanoparticles into a microalgae photobioreactor to promote inorganic carbon conversion. The material preparation process in this patent has a high pyrolysis treatment temperature (700~1200°C), which places high demands on instruments and equipment and is more dangerous.

[0008] It can be seen that although the existing MOF materials used in aqueous bacteria-algae systems have improved the photosynthetic carbon fixation efficiency of microalgae to a certain extent, there are still problems such as harsh reaction conditions, high costs, and inability to separate from the culture medium. In addition, the problem of insufficient utilization of sunlight by microalgae photosynthesis has not been solved.

[0009] Patent CN202110810744.X discloses a metal organic framework-based fluorescent carbon quantum dots (MOF-CDs) and a preparation method thereof. The organic ligands of the MOF material include one or more of 2-methylimidazole, 4-imidazole dithiocarboxylic acid, and triazole. The pre-carbon raw material is a MOF material, and it is used as a powdered material for drug loading and passive targeting of specific disease sites. In this invention, the high specific surface area and pore size of the MOF material are used for drug loading, and the fluorescent signal of the quantum dots is used for material tracing. Although it can achieve dual effects, the subsequent material recovery and processing is difficult.

[0010] Patent CN202311730806.1 discloses a CQD-MOF-stabilized polysulfone hollow porous microsphere and its preparation and application, which achieves good degradation of tetracycline and methylene blue, relying on the large number of active sites and photocatalytic ability of CQD-MOF. It does not utilize photoluminescence ability and does not involve bacterial and algal system sewage treatment technology.

[0011] It can be seen that the role of carbon quantum dots in current carbon quantum dots / MOF materials is mainly to enhance the photocatalytic ability of organic matter or to use their fluorescence signals for material tracking. There are no reports on the use of MOF materials and carbon quantum dots to prepare functional carrier materials to improve the photosynthesis efficiency of microalgae in order to address the problems of incomplete utilization of natural light and low conversion and absorption efficiency of inorganic carbon in bacteria and algae systems under natural light for practical applications.

[0012] In summary, how to provide a microenvironment that is more conducive to synergistic metabolism for the bacteria and algae microorganisms that treat domestic sewage under natural light under the premise of milder reaction conditions and lower preparation costs, thereby improving the absorption and bioconversion efficiency of CO2 produced by bacterial degradation of organic matter by microalgae in the bacteria and algae system, is still a technical problem that needs to be urgently solved in the low-carbon development of the sewage treatment industry. Summary of the invention

[0013] The purpose of the present invention is to provide a method for treating bacteria and algae wastewater and a functional carrier material for treating bacteria and algae wastewater, and to utilize the excellent characteristics of carbon quantum dots such as ultraviolet absorption and photoluminescence to improve the utilization of solar energy. Microalgae directly receive the emitted light of carbon quantum dots as supplementary light energy input for photosynthesis, thereby improving their photosynthesis efficiency. MOF materials and carbon quantum dots are further combined with fixed carriers for bacteria and algae attachment in bacteria and algae systems and provide local high CO2 concentrations and emission light wavelengths, thereby promoting photosynthesis to absorb and convert CO2 and release more O2 to supply the growth and metabolism of heterotrophic bacteria, thereby improving the organic matter degradation and carbon fixation efficiency of the entire system.

[0014] To achieve the above object, the present invention adopts the following technical solution:

[0015] In a first aspect, the present invention provides a method for treating bacterial and algal wastewater, comprising the following steps:

[0016] The functional carrier material for bacteria-algae wastewater treatment is added into the bacteria-algae system, and the wastewater is used as the reaction liquid to treat the wastewater under natural light and in a closed state without aeration;

[0017] The functional carrier material for treating bacteria and algae wastewater includes metal organic framework materials, carbon quantum dots and fixed carriers;

[0018] The metal organic framework material uses iron and zinc as metals and trimesic acid as an organic ligand;

[0019] The carbon quantum dots are made from bacterial and algal biomass recovered from a bacterial and algal wastewater treatment system;

[0020] The fixed carrier is any one of polyurethane sponge, nylon net, cotton cloth and polyester fiber.

[0021] In the above-mentioned bacteria-algae wastewater treatment method, in the bacteria-algae system, the bacteria are activated sludge bacteria, and the algae are one or more of Chlorella, Scenedesmus, Arthrospira platensis, Monospinipes, and Leucophaga;

[0022] The mass ratio of bacteria to algae in the bacteria-algae system is 4:1;

[0023] The initial addition concentration of the bacteria and algae biomass in the bacteria and algae system is 2 g / L.

[0024] In the above-mentioned bacterial and algal wastewater treatment method, in the functional carrier material for bacterial and algal wastewater treatment, the ratio of the mass of the metal organic framework material, the mass of the carbon quantum dots and the volume of the fixed carrier is (0.3-1.25) mg: (0.05-0.2) mg: 1 cm³;

[0025] The volume of the functional carrier material for bacteria-algae wastewater treatment is 30% of the volume of the bacteria-algae system.

[0026] In the above-mentioned method for treating bacteria and algae wastewater, the method for preparing the metal organic framework material comprises the following steps:

[0027] a1) dispersing iron salt, zinc salt and trimesic acid in a solvent, stirring, and collecting the precipitated product;

[0028] The molar ratio of the iron salt, the zinc salt and the trimesic acid is 1:1:1;

[0029] a2) drying and calcining the precipitated product in sequence to obtain the metal organic framework material;

[0030] The drying temperature is 70 to 105°C and the drying time is 6 to 15 hours;

[0031] The calcination temperature is 350° C. and the calcination time is 4 to 8 h.

[0032] In the above-mentioned method for treating bacteria and algae wastewater, the method for preparing carbon quantum dots comprises the following steps:

[0033] b1) dispersing the bacterial and algal biomass recovered from the bacterial and algal domestic sewage treatment system in water, heating it for hydrothermal reaction, and collecting the supernatant by centrifugation after the reaction is completed;

[0034] Every 1-5 g of the bacterial and algal biomass is dispersed in 10-50 mL of water;

[0035] The temperature of the hydrothermal reaction is 150-200°C and the time is 2-4 h;

[0036] b2) placing the supernatant in a dialysis bag and immersing the dialysis bag in water for dialysis, and collecting the liquid in the bag for freeze-drying after the dialysis is completed to obtain the carbon quantum dots;

[0037] In the dialysis step, the cutoff capacity of the dialysis bag is 1000 Da.

[0038] In the above-mentioned method for treating bacteria and algae wastewater, the method for preparing the functional carrier material for treating bacteria and algae wastewater comprises the following steps:

[0039] 1) mixing the metal organic framework material and the adhesive in a solvent, adding the fixed carrier to perform a first impregnation treatment, and drying after the treatment to obtain an intermediate carrier;

[0040] 2) dissolving the carbon quantum dots in a glutaraldehyde solution, adding the intermediate carrier to perform a second impregnation treatment, and drying after the treatment to obtain the functional carrier material for bacteria and algae wastewater treatment.

[0041] In the above-mentioned method for treating bacteria and algae wastewater, the wastewater is domestic wastewater.

[0042] In a second aspect, the present invention protects a functional carrier material for bacterial and algal wastewater treatment, including a metal organic framework material, carbon quantum dots and a fixed carrier;

[0043] The metal organic framework material uses iron and zinc as metals and trimesic acid as an organic ligand;

[0044] The carbon quantum dots are made from bacterial and algal biomass recovered from a bacterial and algal wastewater treatment system;

[0045] The fixed carrier is any one of polyurethane sponge, nylon mesh, cotton cloth, and polyester fiber;

[0046] The ratio of the mass of the metal organic framework material, the mass of the carbon quantum dots and the volume of the fixed carrier is 0.3125 mg:0.125 mg:1 cm³.

[0047] In a third aspect, the present invention provides a method for preparing a functional carrier material for treating bacteria and algae wastewater, comprising the following steps:

[0048] 1) mixing the metal organic framework material and the adhesive in a solvent, adding the fixed carrier to perform a first impregnation treatment, and drying after the treatment to obtain an intermediate carrier;

[0049] 2) dissolving the carbon quantum dots in a glutaraldehyde solution, adding the intermediate carrier to perform a second impregnation treatment, and drying after the treatment to obtain the functional carrier material for bacteria and algae wastewater treatment.

[0050] In the above-mentioned method for preparing the functional carrier material for treating bacteria and algae wastewater, the method for preparing the metal organic framework material comprises the following steps:

[0051] a1) dispersing iron salt, zinc salt and trimesic acid in a solvent, stirring, and collecting the precipitated product;

[0052] The molar ratio of the iron salt, the zinc salt and the trimesic acid is 1:1:1;

[0053] The solvent is ethanol, and 5.04 g of trimesic acid is added to every 46 mL of the ethanol;

[0054] The stirring speed is 100 rpm to 300 rpm, and the time is 40 to 60 h;

[0055] a2) drying and calcining the precipitated product in sequence to obtain the metal organic framework material;

[0056] The drying temperature is 70 to 105°C and the drying time is 6 to 15 hours;

[0057] The calcination temperature is 350°C and the calcination time is 4 to 8 hours;

[0058] In step 1), the adhesive is polyvinylidene fluoride;

[0059] In step 1), the solvent is N,N-dimethylformamide;

[0060] The first immersion treatment is to repeatedly squeeze the fixed carrier in the mixed solution so that the gaps in the fixed carrier are fully in contact with the mixed solution, and at the same time, the mixed solution is ultrasonicated for 2 to 5 hours;

[0061] The method for preparing carbon quantum dots comprises the following steps:

[0062] b1) dispersing the bacterial and algal biomass recovered from the bacterial and algal domestic sewage treatment system in water, heating it for hydrothermal reaction, and collecting the supernatant by centrifugation after the reaction is completed;

[0063] Every 1-5 g of the bacterial and algal biomass is dispersed in 10-50 mL of water;

[0064] The temperature of the hydrothermal reaction is 150-200°C and the time is 2-4 h;

[0065] The centrifugal speed is 8000-10000 rpm, and the time is 20-30 min;

[0066] b2) placing the supernatant in a dialysis bag and immersing the dialysis bag in water for dialysis, and collecting the liquid in the bag for freeze-drying after the dialysis is completed to obtain the carbon quantum dots;

[0067] In the dialysis step, the cutoff of the dialysis bag is 1000 Da, the dialysis time is 36 to 60 hours, and the water is changed at least 3 times during the dialysis step;

[0068] The mass ratio of the metal organic framework material to the adhesive polyvinylidene fluoride resin is (1-2): 1;

[0069] In step 2), 15 to 25 mg of the carbon quantum dots are dissolved in 10 to 50 mL of a glutaraldehyde solution having a mass concentration of 2.5 to 5%;

[0070] The second impregnation treatment is soaking, and the soaking time is 3 to 5 hours;

[0071] The drying temperature is 60-80° C. and the drying time is 10-12 hours.

[0072] The present invention has the following beneficial effects:

[0073] (1) The raw materials and preparation process of the present invention can save energy consumption, and can be used to degrade and transform organic matter (organic carbon) and fix inorganic carbon in coupling with biological systems with good results. The present invention uses Fe-Zn-based MOF materials and bacteria-algae biomass carbon quantum dots to prepare functional carrier materials. The raw materials are green and cheap, the preparation steps are simple, and the energy consumption is low. It is used in the bacteria-algae system to treat sewage, which increases the CO2 enrichment and solar spectrum absorption in the water, provides a favorable environment for photosynthetic carbon fixation of microalgae and the exchange of carbon and oxygen substances between bacteria and algae, and improves the degradation of organic matter and CO2 enrichment and conversion efficiency of the bacteria-algae system in treating domestic sewage.

[0074] (2) The present invention does not require additional carbon source and energy input during the application process, thereby reducing the direct CO2 emissions from the system caused by the mismatch between the rate of CO2 produced by heterotrophic bacteria degrading organic matter, the diffusion rate of CO2 in water, and the rate of CO2 fixation by microalgae photosynthesis, while reducing the indirect carbon emissions caused by energy consumption during the aeration process.

[0075] (3) The composite carrier material synthesized in the present invention has no recycling problem, does not affect the effluent quality, and alleviates the problem of the effluent requiring further treatment due to the loss of microalgae in the effluent of the suspended bacteria-algae system.

[0076] (4) Using MOF materials to enrich CO2 and increase the local concentration of microalgae can better exert the photoluminescence effect of CQDs and use it as a supplementary light energy input.

[0077] (5) The present invention targets the limitation of photosynthetic carbon fixation in the bacteria-algae system, and uses activated sludge and Chlorella as the microbial basis of the bacteria-algae system. In a closed, non-aerated state, the addition of functional carrier materials can provide a favorable microenvironment with local high CO2 concentration and blue light emission, thereby improving the photosynthetic efficiency of microalgae, thereby promoting the carbon-oxygen cycle between bacteria and algae and achieving an improvement in the degradation of organic matter and carbon fixation efficiency during sewage treatment.

[0078] In summary, the present invention provides a method for preparing a simple, bio-friendly, composite functional CQDs@MOFs functional carrier material and its application in a bacteria-algae system; the functional carrier material prepared by the method of the present invention has a good promoting effect on carbon fixation in the bacteria-algae system, and its use in carbon fixation in the bacteria-algae domestic sewage treatment process has important application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 This is a schematic diagram of the principle of using the functional carrier material of the present invention to enhance the carbon fixation effect of the bacteria and algae system in treating domestic sewage.

[0080] Figure 2 This is a graph showing the carbon fixation efficiency of the bacterial and algal domestic sewage treatment process at different bacterial and algal biomass concentrations in Example 1 of the present invention.

[0081] Figure 3 This is a graph showing the growth of bacterial and algal biomass at different carrier filling rates in Example 2 of the present invention.

[0082] Figure 4 This is a diagram showing the carbon fixation of the bacteria-algae wastewater treatment system under different load ratios in Example 3 of the present invention.

[0083] Figure 5 The scanning electron microscope (a, b) and energy spectrum (c) images of the CQDs@MOFs functional carrier material prepared in Example 4 of the present invention.

[0084] Figure 6 It is a comparison chart of the organic matter degradation efficiency of Example 5 and Comparative Examples 1-3 in the process of bacterial and algal domestic sewage treatment.

[0085] Figure 7 It is a comparison chart of the carbon fixation performance test of Example 5 and Comparative Examples 1-3 in the bacteria and algae wastewater treatment system. DETAILED DESCRIPTION

[0086] As described in the background technology, the bacteria-algae system uses the symbiotic effect between microalgae and bacteria to treat sewage, but the CO2 produced by the degradation of organic matter by bacteria in the bacteria-algae system is absorbed by algae and the bioconversion efficiency is low, which limits the application efficiency of the bacteria-algae system as a carbon reduction technology in urban sewage treatment. In the first part, the present invention provides a bacteria-algae sewage treatment method, comprising the following steps: adding a functional carrier material for bacteria-algae sewage treatment to the bacteria-algae system, using sewage as a reaction liquid, and treating sewage under natural light, closed and aerated conditions; the functional carrier material for bacteria-algae sewage treatment includes metal organic framework materials, carbon quantum dots and fixed carriers; the metal organic framework material (MOF material) uses iron and zinc as metals and trimesic acid as organic ligands; the carbon quantum dots (CQDs) are made of bacteria-algae biomass recovered from the bacteria-algae sewage treatment system; the fixed carrier is any one of polyurethane sponge, nylon mesh, cotton cloth, and polyester fiber.

[0087] Based on the above technical scheme, the present invention adds functional carrier materials including metal organic framework materials, carbon quantum dots and fixed carriers into the bacteria-algae system for sewage treatment, and utilizes the excellent characteristics of carbon quantum dots such as ultraviolet absorption and photoluminescence to improve the utilization of solar energy. Microalgae directly receive the emitted light of carbon quantum dots as the light energy input for photosynthesis, thereby improving their photosynthesis efficiency. Furthermore, MOF materials and carbon quantum dots are combined with fixed carriers for bacteria-algae attachment in the bacteria-algae system, providing local high CO2 concentration and emission light wavelength, promoting photosynthesis to absorb and transform CO2 and release more O2 to supply heterotrophic bacteria growth metabolism. Figure 1As shown, after the functional carrier material is added to the bacteria-algae system, it can enrich CO2 in the water and emit blue-violet light by photoluminescence, thereby creating a favorable microenvironment with high CO2 concentration and suitable light wavelength for photosynthesis in the reaction system, improving the carbon-oxygen cycle between bacteria and algae, thereby enhancing the organic matter degradation and carbon fixation effect in the bacteria-algae sewage treatment process; the present invention reduces the system CO2 emission caused by the mismatch between the rate of CO2 produced by bacteria degrading sewage organic matter, the diffusion rate of CO2 in water and the rate of CO2 fixation by microalgae photosynthesis, strengthens the use of sunlight by the bacteria-algae system under natural light, and can effectively improve the organic matter degradation and carbon fixation effect of the bacteria-algae system on domestic sewage.

[0088] In addition, MOF materials are porous structural materials with H3BTC as organic ligands and Fe and Zn as metal active sites. They have an enrichment effect on CO2 in water and have good biocompatibility. This may be because metal Fe plays an extremely important role in physiological processes such as plant photosynthesis, respiration, nitrogen fixation, protein and nucleic acid synthesis, and metal Zn is closely related to carbon anhydrase, a key enzyme for carbon fixation, which helps the system to fix inorganic carbon; CQDs are carbon quantum dots prepared from bacteria and algae biomass. The above two materials are attached to a fixed carrier by a cross-linking method to obtain the functional carrier material of the present invention, which is a composite functional carrier material that can enhance the degradation of organic matter and carbon fixation efficiency in the process of treating domestic sewage by bacteria and algae systems.

[0089] Furthermore, during the treatment process, the functional carrier material is added to the bacteria-algae domestic sewage treatment system, and the activated sludge bacteria and Chlorella are fixedly attached to the functional carrier material after being cultured and domesticated, forming a bacteria-algae symbiotic biofilm on the functional carrier material, which increases the biomass of bacteria and algae. At the same time, CO2 in the water can be enriched on the functional carrier material. The bacteria in the biofilm have the function of degrading organic matter in the water, and the algae in the biofilm have the function of absorbing and converting CO2 and inorganic carbon, which is not only conducive to the degradation of organic matter in the water, but also enhances the photosynthetic absorption and conversion of CO2 and inorganic carbon by algae. In the present invention, the functional material can fix carbon in sewage, including organic carbon, inorganic carbon in sewage, and CO2 produced by bacteria degrading organic matter.

[0090] According to the present invention, in the bacteria-algae system, the bacteria are activated sludge bacteria, and the algae are one or more of Chlorella, Scenedesmus, Arthrospira platensis, Monopterus, and Leucophaga; the bacteria-algae mass ratio of the bacteria-algae system is 4:1; the bacteria-algae ratio refers to the ratio of the mass of organic matter in the suspended solids contained in the bacteria in a unit volume of reaction liquid to the mass of biomass of microalgae species; the initial addition concentration of bacteria-algae biomass in the bacteria-algae system is 2 g / L. In one embodiment of the present invention, the mass ratio of bacteria and algae in the bacteria-algae system is 4:1. The effect of the amount of bacteria and algae added on the final organic matter degradation and carbon fixation effect is explored. The results show that when the initial addition concentration of bacteria and algae biomass is too low, the microorganisms cannot fully exert their metabolic effects in the system. When the initial addition concentration of bacteria and algae biomass is too high, the bacteria and algae biomass concentration in the bacteria and algae system is too high, and shading will occur, reducing the absorption of light energy by Chlorella in the bacteria and algae system, thereby reducing the absorption and conversion of CO2 and the production of O2. Too low or too high initial addition concentration of bacteria and algae biomass is not conducive to carbon fixation, and the carbon fixation effect of 2 g / L bacteria and algae biomass concentration is the best. The term "initial addition concentration of bacteria and algae biomass" refers to the mass concentration of organic biomass including activated sludge bacteria and microalgae species added to the reaction system when the bacteria and algae system is initially constructed. As an example, the initial addition algae species in the bacteria and algae system is Chlorella vulgaris, which comes from the freshwater algae species bank of the Institute of Hydrobiology, Chinese Academy of Sciences, and the species number is FACHB-31. As an example, the initially added bacteria in the bacteria-algae system are activated sludge bacteria for sewage treatment, such as the activated sludge bacteria with product number WS388 from Shanghai Bilaiqing Biotechnology Co., Ltd., or activated sludge bacteria from an aerobic tank in a sewage treatment plant.

[0091] According to the present invention, in the functional carrier material for bacteria-algae wastewater treatment, the ratio of the mass of the metal organic framework material, the mass of the carbon quantum dots and the volume of the fixed carrier is 0.3125 mg: 0.125 mg: 1 cm³; the volume of the functional carrier material for bacteria-algae wastewater treatment is 30% of the volume of the bacteria-algae system. In one embodiment of the present invention, the effect of the carrier filling rate on the growth of microorganisms in the bacteria-algae system was investigated. The initial biomass concentration of the activated sludge flora and Chlorella was 2 g / L, and the initial bacteria-algae ratio was 4:1. The results showed that when the carrier filling rate was 30%, the algae-bacteria biofilm system had the best carrier filling rate. Among them, the carrier filling rate refers to the volume percentage of the carrier in the bacteria-algae system. When the carrier is loaded with metal organic framework materials and carbon quantum dots, the filling rate of the functional carrier is calculated based on the volume of the fixed carrier. In one embodiment of the present invention, the effect of MOF material loading ratio on carbon fixation efficiency in bacteria-algae system was investigated. The volume of functional carrier material for bacteria-algae wastewater treatment was 30% of the volume of bacteria-algae system, the initial biomass concentration of activated sludge flora and Chlorella was 2 g / L, and the initial bacteria-algae ratio was 4:1. When the material loading ratio of metal-organic framework material was 0.3125 mg / cm³, the TC fixation and organic carbon degradation effects were the best. Among them, the material loading ratio of metal-organic framework material is the mass ratio of metal-organic framework material to the volume ratio of fixed carrier.

[0092] According to the present invention, the preparation method of the metal organic framework material comprises the following steps: a1) dispersing iron salt, zinc salt and trimesic acid in a solvent and stirring, and collecting the precipitated product; the molar ratio of the iron salt, the zinc salt and the trimesic acid is 1:1:1; a2) drying and calcining the precipitated product in sequence to obtain the metal organic framework material; the drying temperature is 70 to 105°C and the time is 6 to 15 h, such as drying at 80°C for 12 h; the calcining temperature is 350°C and the time is 4 to 8 h, such as calcining at 350°C for 6 h. The preparation method of the carbon quantum dots comprises the following steps: b1) dispersing the bacteria and algae biomass recovered from the bacteria and algae domestic sewage treatment system in water, heating for hydrothermal reaction, and collecting the supernatant by centrifugation after the reaction is completed; every 1 to 5 g of the bacteria and algae biomass is dispersed in 10 to 50 mL of water, such as 3 g of the bacteria and algae biomass is dispersed in 20 mL of ultrapure water; the temperature of the hydrothermal reaction is 150 to 200° C., and the time is 2 to 4 h, such as hydrothermal reaction at 180° C. for 3 h; b2) placing the supernatant in a dialysis bag and immersing the dialysis bag in water for dialysis, and collecting the liquid in the bag after the dialysis is completed for freeze-drying to obtain the carbon quantum dots; in the dialysis step, the retention capacity of the dialysis bag is 1000 Da. In a specific embodiment of the present invention, the carbon quantum dots are made of bacterial and algal biomass recovered from a bacterial and algal system. The bacterial and algal biomass has been published in the article "Photosynthesis Characterization of Mutant Algae and Enhanced Carbon Fixation of Algae-Bacteria Symbiosis Treating Municipal Wastewater". Its main microbial composition is shown in figure 6 (b) R1, and is obtained by the following steps: taking out the suspended bacterial and algal liquid from the bacterial and algal reactor, mixing it and determining the biomass concentration, and then taking a corresponding volume of the suspended bacterial and algal liquid and centrifuging it at 8000 rpm for 3 min.

[0093] According to the present invention, the preparation method of the functional carrier material for treating bacteria and algae wastewater comprises the following steps: 1) mixing the metal organic framework material and the adhesive in a solvent, and then adding the fixed carrier for the first impregnation treatment, drying after the treatment, to obtain an intermediate carrier; 2) dissolving the carbon quantum dots in a glutaraldehyde solution, and then adding the intermediate carrier for the second impregnation treatment, and drying after the treatment, to obtain the functional carrier material for treating bacteria and algae wastewater. It can be understood that by using an adhesive to bond the MOF material to the surface and voids of the carrier, it can be understood that for the method of the present invention, any adhesive that can bond the MOF material to the fixed carrier can be used, not just limited to polyvinylidene fluoride (PVDF), and the solvent can be selected according to the adhesive composition.

[0094] According to the present invention, the sewage is domestic sewage. In an embodiment of the present invention, the sewage adopts simulated sewage with the following composition: 150 mg / L NH4Cl, 300 mg / L NaHCO3, 5 mg / L CaCl2, 35 mg / L MgSO4, 30 mg / L KH2PO4, 500 mg / L glucose, 1.5 mg / L FeSO4·7H2O, 0.1 mg / L CuSO4, 0.2 mg / L ZnSO4·7H2O, 0.2 mg / L MnSO4·7H2O, 0.3 mg / L NaCl, 0.2 mg / L CoCl2·6H2O, 0.5 mg / L Ma2MoO4·2H2O, and the pH of the solution is adjusted to 7.0 with 1 mol / L HCl.

[0095] In the second part, the present invention provides a functional carrier material for bacteria and algae wastewater treatment, including a metal organic framework material, a carbon quantum dot and a fixed carrier; the metal organic framework material uses iron and zinc as metals and trimesic acid as an organic ligand; the carbon quantum dots are made of bacteria and algae biomass recovered from the bacteria and algae wastewater treatment system; the fixed carrier is any one of polyurethane sponge, nylon mesh, cotton cloth, and polyester fiber; the ratio of the mass of the metal organic framework material, the mass of the carbon quantum dots, and the volume of the fixed carrier is (0.3-1.25) mg: (0.05-0.2) mg: 1 cm³. As an example, the ratio of the mass of the metal organic framework material, the mass of the carbon quantum dots, and the volume of the fixed carrier is 0.3125 mg: 0.125 mg: 1 cm³.

[0096] In the third part, the present invention provides a method for preparing the functional carrier material for bacteria and algae wastewater treatment, comprising the following steps: 1) mixing the metal organic framework material and the adhesive in a solvent, and then adding the fixed carrier for a first impregnation treatment, and drying after the treatment to obtain an intermediate carrier; 2) dissolving the carbon quantum dots in a glutaraldehyde solution, and then adding the intermediate carrier for a second impregnation treatment, and drying after the treatment to obtain the functional carrier material for bacteria and algae wastewater treatment.

[0097] According to the present invention, the preparation method of the metal organic framework material comprises the following steps: a1) dispersing iron salt, zinc salt and trimesic acid in a solvent and stirring, and collecting the precipitated product; the molar ratio of the iron salt, the zinc salt and the trimesic acid is 1:1:1; the solvent is ethanol, and 5.04 g of the trimesic acid is added to every 46 mL of the ethanol; the stirring speed is 100 rpm to 300 rpm, and the time is 40 to 60 h, such as stirring at 150 rpm for 48 h; the collected precipitated product can be obtained by centrifuging at 5000 rpm for 3 min; a2) drying and calcining the precipitated product in sequence to obtain the metal organic framework material; the drying temperature is 70 to 105°C, and the time is 6 to 15 h, such as drying at 80°C for 12 h; the calcining temperature is 350°C, and the time is 4 to 8 h, such as calcining for 6 h.

[0098] According to the present invention, in step 1), the adhesive is polyvinylidene fluoride; in step 1), the solvent is N,N-dimethylformamide (DMF); the first impregnation treatment is to repeatedly squeeze the fixed carrier in the mixed solution so that the voids in the fixed carrier are fully in contact with the mixed solution, and the mixed solution is ultrasonicated at the same time, and the ultrasonic time is 2 to 5 hours, such as ultrasonication for 2 hours; wherein, the extrusion treatment can make all the voids of the fixed carrier with a large specific surface area fully in contact with the mixed solution, so that the MOF material in the mixed solution is fully loaded in the fixed carrier; after the treatment is completed, it can be dried at 80°C.

[0099] According to the present invention, the preparation method of the carbon quantum dots comprises the following steps: b1) dispersing the algae biomass recovered from the algae domestic sewage treatment system in water, heating for hydrothermal reaction, and collecting the supernatant by centrifugation after the reaction is completed; every 1 to 5 g of the algae biomass is dispersed in 10 to 50 mL of water, such as every 3 g of the algae biomass is dispersed in 20 mL of water; the temperature of the hydrothermal reaction is 150 to 200°C, and the time is 2 to 4 h, such as hydrothermal reaction at 180°C for 3 h; the speed of the centrifugation is 8000 to 10000 rpm, and the time is 20 to 30 min, such as centrifugation at 10000 rpm for 20 min; b2) placing the supernatant in a dialysis bag and immersing the dialysis bag in water for dialysis, and collecting the liquid in the bag after the dialysis is completed for freeze-drying to obtain the carbon quantum dots; in the dialysis step, the retention capacity of the dialysis bag is 1000 Da, and the dialysis time is 36 to 60 h, such as dialysis for 48 h, during which the water is changed at least 3 times; the mass ratio of the metal organic framework material to the adhesive polyvinylidene fluoride resin is (1-2):1, such as 1:1.

[0100] According to the present invention, in step 2), every 15 to 25 mg of the carbon quantum dots is dissolved in 10 to 50 mL of a glutaraldehyde solution having a mass concentration of 2.5 to 5%, such as every 25 mg of CQDs is dissolved in 10 mL of a glutaraldehyde solution having a mass concentration of 5%; the second impregnation treatment is immersion, and the immersion time is 3 to 5 h, such as 3 h; similarly, the second impregnation treatment is used to fully fix the carbon quantum dots in the fixed carrier; the drying temperature is 60 to 80°C, and the time is 10 to 12 h, such as drying at 60°C for 12 h.

[0101] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0102] The methods used in the following examples, unless otherwise specified, are all conventional methods, carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0103] The initial added bacteria in the bacteria-algae system in the following examples are activated sludge bacteria purchased from Shanghai Bilaiqing Biotechnology Co., Ltd., product number WS388. After purchase, they were domesticated in the laboratory for 7 to 10 days before being used in the experiment.

[0104] The initial algae species added to the bacteria-algae system in the following examples is Chlorella vulgaris C. vulgaris , from the freshwater algae species bank of the Institute of Hydrobiology, Chinese Academy of Sciences, the strain number is FACHB-31.

[0105] The bacterial and algal biomass used to prepare CQDs in the following examples was preserved in the laboratory and has been published in the article Photosynthesis Characterization of Mutant Algae and Enhanced Carbon Fixation of Algae–Bacteria Symbiosis Treating Municipal Wastewater. Its main microbial composition is shown in figure 6 (b) R1, which is obtained by the following steps: taking out the suspended bacterial and algal liquid from the bacterial and algal reactor, mixing it and determining the biomass concentration, and then taking the corresponding volume of the suspended bacterial and algal liquid and centrifuging it at 8000 rpm for 3 min.

[0106] The sewage in the following embodiments adopts simulated sewage of the following composition: 150 mg / L NH4Cl, 300 mg / LNaHCO3, 5 mg / L CaCl2, 35 mg / L MgSO4, 30 mg / L KH2PO4, 500 mg / L glucose, 1.5 mg / LFeSO4·7H2O, 0.1 mg / L CuSO4, 0.2 mg / L ZnSO4·7H2O, 0.2 mg / L MnSO4·7H2O, 0.3 mg / LNaCl, 0.2 mg / L CoCl2·6H2O, 0.5 mg / L Ma2MoO4·2H2O, and the pH of the solution is adjusted to 7.0 with 1 mol / L HCl.

[0107] The polyurethane sponge carrier in the following embodiments was purchased from Henan Saiyue Environmental Protection Technology Co., Ltd., and the product number is SY0006.

[0108] Example 1: Investigating the effect of the amount of bacteria and algae added on the final organic matter degradation and carbon fixation effect

[0109] The experiment on the effect of the amount of bacteria and algae added on the final carbon fixation effect was carried out according to the following steps

[0110] (1) Activated sludge bacteria and Chlorella vulgaris were added into a 200 mL anaerobic bottle at a biomass ratio of 4:1 and concentrations of 0, 1, 2, and 3 g / L. The reaction solution was simulated domestic sewage, and a bacterial-algal biological sewage treatment system was constructed.

[0111] (2) The bacteria and algae wastewater was treated under natural light. A certain amount of the initial reaction liquid and the reaction liquid after a certain period of time were taken out and filtered through a 0.45 μm filter membrane to obtain liquid samples for subsequent water sample detection and analysis.

[0112] IC and TC concentrations were measured using a Shimadzu total organic carbon analyzer.

[0113] Figure 2The carbon fixation efficiency diagram of the bacterial algae domestic sewage treatment process under different bacterial algae biomass concentrations in Example 1 is shown. Under the treatment conditions of this example, the bacterial algae biomass concentration of 2 g / L has a better carbon fixation efficiency in the bacterial algae system. At 36 h, the IC fixation rate is 18.04% and 6.33% higher than that of 1 g / L and 3 g / L, respectively; the TC fixation rate is 2.17% and 2.57% higher than that of 1 g / L and 3 g / L, respectively. The carbon fixation effect of the bacterial algae biomass concentration of 2 g / L is higher than that of the bacterial algae biomass concentration of 1 g / L because more microorganisms play a metabolic role in the system; and the carbon fixation effect of the bacterial algae system with a bacterial algae biomass concentration of 3 g / L is lower than that of 2 g / L because the bacterial algae biomass concentration in the bacterial algae system is too high, which will cause shading, reduce the absorption of light energy by Chlorella in the bacterial algae system, and then reduce the absorption and conversion of CO2 and the production of O2, thereby reducing the carbon fixation rate of the system. Therefore, in the present invention, a bacteria-algae biomass concentration of 2 g / L is selected as the initial biomass addition concentration of the bacteria-algae system.

[0114] Example 2: Investigating the effect of carrier filling rate on microbial growth in bacteria-algae system

[0115] The experiment on the effect of carrier filling rate on the growth of microorganisms in the bacteria-algae system was carried out according to the following steps.

[0116] (1) Activated sludge bacteria and Chlorella vulgaris were added into a 200 mL anaerobic bottle at an initial biomass concentration of 2 g / L and an initial bacteria-algae ratio of 4:1. The reaction liquid was simulated domestic sewage. Polyurethane sponge carriers with a total volume of 20 cm³ (filling rate 10%), 40 cm³ (filling rate 20%), 60 cm³ (filling rate 30%), and 80 cm³ (filling rate 40%) were added into the system, respectively, to construct bacteria-algae domestic sewage treatment systems with different carrier filling rates.

[0117] (2) The wastewater was treated with bacteria and algae under natural light. 50% of the reaction solution was exchanged every 24 h to ensure sufficient nutrients for microbial growth. The microbial biomass in the bacteria and algae system was measured after one week.

[0118] (3) Direct determination of the MLVSS of biomass in the liquid phase; the biofilm biomass determination process is as follows: the original polyurethane sponge carrier is removed from the system, and the biomass on the carrier is removed by ultrasound, vibration, and extrusion, and its MLVSS is determined.

[0119] Figure 3The growth of algae biomass under different carrier filling rates is shown in Figure 1. Carriers were added at filling rates of 10%, 20%, 30%, and 40%, and the biofilm growth and algae biomass of the system were observed after one week of growth. As can be seen from the figure, the total biomass was the highest at a filling rate of 40%. Although the total biomass was slightly less than that of the 40% filling rate system at a filling rate of 30%, the biomass of the biofilm phase was the highest and significantly higher than that of the biofilm biomass in other filling rate systems, which was 29.92% higher than that of the 40% filling rate system. In terms of the biofilm biomass per unit volume of carrier, the biofilm biomass per unit volume of carrier under the 30% carrier filling rate system was 2.03%, 10.72%, and 73.23% higher than that of the 10%, 20%, and 40% carrier filling rate systems, respectively. Therefore, a carrier filling rate of 30% was selected as the optimal carrier filling rate for the algae biofilm system.

[0120] Example 3: Investigating the effect of MOF material loading ratio on carbon fixation efficiency in bacteria-algae system

[0121] The experiment on the effect of MOF material loading ratio on carbon fixation efficiency in bacteria-algae system was carried out according to the following steps

[0122] (1) Add 9.62 g Fe(NO3)3·9H2O and 3.27 g ZnCl2 to 46 ml ethanol. After complete dissolution, add 5.04 g H3BTC. Stir at 150 rpm for 48 h, centrifuge at 5000 rpm for 3 min, wash three times with ethanol, and retain the mixed precipitate. Dry it in an oven at 80 °C for 12 h. Place the dried material in a crucible and calcine it at 350 °C for 6 h to obtain Fe-Zn-based MOF material.

[0123] (2) Weigh 0, 30, 50, 100, 200, and 300 mg of MOF material and dissolve them in 10 mL of DMF. Weigh 50 mg of PVDF material and dissolve it in 10 mL of DMF. After the two solutions are dissolved, mix them and place a polyurethane sponge carrier (20 pieces, each with a size of 2×2×2 cm) in them. The loading ratios are 0, 0.1875 mg / cm³, 0.3125 mg / cm³, 0.6250 mg / cm³, 1.25 mg / cm³, and 1.875 mg / cm³, respectively. Repeatedly squeeze and ultrasonicate in the solution for 2 h, then take out and dry in an oven at 80°C.

[0124] (3) The carrier material prepared in step (2) was added at a rate of 30% of the volume of the bacteria-algae reaction liquid system to a bacteria-algae system with a bacteria-algae biomass concentration of 2 g / L and a bacteria-algae ratio of 4:1. The reaction liquid was simulated domestic sewage and was placed under natural light for bacteria-algae sewage treatment. A certain amount of the initial reaction liquid and the reaction liquid after a certain interval was taken out and filtered through a 0.45 μm filter membrane to obtain a liquid sample for subsequent water sample detection and analysis.

[0125] Figure 4 The carbon fixation of the bacteria-algae sewage treatment system under different loading ratios was measured by adding the loading agent at material loading ratios of 0, 0.1875, 0.3125, 0.6250, 1.25, and 1.875 mg / cm³ and a filling rate of 30% to determine the carbon fixation effect of the system in the process of treating domestic sewage. Figure 3 It can be seen that as the loading rate gradually increases from 0 to 0.3125, the organic carbon degradation rate and total carbon fixation rate gradually increase, but as the loading rate further increases, the organic carbon degradation rate and total carbon fixation rate begin to decrease, but overall they are higher than the control group. At a loading rate of 0.3125, the organic carbon degradation rate in 12 h reaches 93.20%, which is 3.04%, 9.95%, 8.43% and 17.95% higher than the loading rates of 0.1875, 0.6250, 1.25 and 1.875, respectively. At a loading rate of 0.3125, the TC fixation rate in 24 h reaches 89.58%, which is 6.53%, 8.64%, 5.92% and 17.42% higher than the loading rates of 0.1875, 0.6250, 1.25 and 1.875, respectively. Therefore, 0.3125 mg / cm³ is the optimal loading rate.

[0126] Example 4: Preparation of CQDs@MOFs functional carrier material

[0127] The CQDs@MOFs functional carrier material was prepared according to the following steps:

[0128] (1) Add 9.62 g Fe(NO3)3·9H2O and 3.27 g ZnCl2 to 46 ml ethanol. After complete dissolution, add 5.04 g H3BTC. Stir at 150 rpm for 48 h, centrifuge at 5000 rpm for 3 min, wash three times with ethanol, and retain the mixed precipitate. Dry it in an oven at 80 °C for 12 h. Place the dried material in a crucible and calcine it at 350 °C for 6 h to obtain Fe-Zn-based MOF material.

[0129] (2) 3 g of algal biomass harvested from the algal system was washed three times, resuspended in 20 mL of ultrapure water, placed in a 100 mL reactor and hydrothermaled at 180 °C for 3 h. After the reactor was cooled to room temperature, it was taken out and centrifuged at 10,000 rpm for 20 min. The yellow supernatant was retained. The supernatant was placed in a dialysis bag with a cutoff volume of 1,000 Da and the dialysis bag was immersed in water for 48 h. During this period, the water was changed three times. The light yellow liquid in the bag was collected and freeze-dried to obtain algal biomass CQDs.

[0130] (3) Weigh 50 mg of MOF material and dissolve it in 10 mL of DMF. Weigh 50 mg of PVDF material and dissolve it in 10 mL of DMF. After the two solutions are dissolved, mix them and place a polyurethane sponge carrier (20 pieces, each with a size of 2×2×2 cm) in them. Repeatedly squeeze and ultrasonicate them in the solution for 2 h, then take them out and dry them in an oven at 80°C.

[0131] (4) Dissolve 50 mg of CQDs in 20 mL of 5% glutaraldehyde solution, soak the carrier material obtained in step (3) in the CQDs glutaraldehyde solution for 3 h, take it out and place it in an oven at 60 ° C for 12 h to dry, and obtain a CQDs@MOFs functional carrier material.

[0132] Figure 5 The scanning electron microscope (a, b) and energy spectrum (c) images of the CQDs@MOFs functional carrier material show that the material is successfully combined with the original carrier to form a functional carrier material. The porous structure on the surface of the functional carrier material provides more sites for the attachment of bacteria and algae microorganisms, thereby providing adsorption space and transmission channels for CO2 and O2 released during the growth and metabolism of bacteria and algae. The metal Fe on the surface plays an extremely important role in the physiological processes of plant photosynthesis, respiration, nitrogen fixation, protein and nucleic acid synthesis, and is beneficial to the photosynthesis of microalgae; the metal Zn is closely related to carbonic anhydrase, a key enzyme for carbon fixation, and helps the system fix inorganic carbon.

[0133] Example 5: Functional carrier materials for bacterial and algal domestic sewage treatment

[0134] The functional carrier material prepared in Example 4 was added at a rate of 30% by volume of the bacteria-algae reaction liquid system to a bacteria-algae system with a bacteria-algae biomass concentration of 2 g / L and a bacteria-algae ratio of 4:1. The reaction liquid was simulated domestic sewage, which was placed under natural light for bacteria-algae sewage treatment. A certain amount of the initial reaction liquid and the reaction liquid after a certain interval was taken out and filtered through a 0.45 μm filter membrane to obtain a liquid sample for subsequent water sample detection and analysis.

[0135] The water sample analysis included COD concentration and total carbon (TC) concentration.

[0136] The COD concentration was measured using the potassium dichromate method, and the TC concentration was measured using a Shimadzu total organic carbon analyzer.

[0137] Draw a curve of COD degradation rate versus treatment time.

[0138] The calculation formula of COD degradation rate is as follows:

[0139]

[0140] Where, K is the COD degradation rate, %; is the COD concentration in the bacteria-algae system at the initial moment, mg / L; is the COD concentration in the bacteria-algae system at time t, mg / L.

[0141] The TC fixation rate was calculated for a treatment time of 6 h. The calculation formula for the TC fixation rate is as follows:

[0142]

[0143] Where, F is the TC fixed rate, %; is the TC concentration in the bacteria-algae system at the initial moment, mg / L; is the TC concentration in the bacteria-algae system at time t, mg / L.

[0144] Comparative Example 1

[0145] The operation is the same as that in Example 5, except that the functional carrier material prepared in Example 4 is not added, and only the bacteria-algae system is used to treat domestic sewage.

[0146] Comparative Example 2

[0147] The operation is the same as that of Example 5, except that the functional carrier material prepared in Example 4 is replaced by the Fe-Zn-based MOF powder material prepared in step (1) of Example 4.

[0148] Comparative Example 3

[0149] The operation is the same as that of Example 5, except that the functional carrier material prepared in Example 4 is replaced by the algae biomass CQDs prepared in step (2) of Example 4.

[0150] Figure 6 The organic matter degradation efficiency diagram of Example 5 and Comparative Examples 1-3 in the process of treating domestic sewage with algae and bacteria is shown in FIG. Figure 6 It can be seen that under the promotion of the functional carrier material of the present invention, the COD Class A effluent standard can be reached more quickly, and the organic matter degradation efficiency is increased by up to 22.61% during the 6 h treatment process.

[0151] Figure 7 The carbon fixation efficiency diagram of the bacteria-algae domestic sewage treatment process of Example 5 and Comparative Examples 1-3 is as follows. Under the promotion of the functional carrier material of the present invention, the total carbon fixation efficiency of the 6-h bacteria-algae system can be increased by 21.15%.

[0152] Depend on Figure 6-7It can be seen from the treatment results of the materials in each treatment group on the bacterial and algal domestic sewage that during the 6 h treatment process, the carbon fixation effect of comparative example 2 was improved by 10.14% compared with that of comparative example 1, the carbon fixation effect of comparative example 3 was improved by 5.83% compared with that of comparative example 1, and the carbon fixation effect of embodiment 5 was improved by 19.15% compared with that of comparative example 1. The improvement effect of comparative example 3 compared with comparative example 1 was higher than the simple sum of comparative examples 2 and 3. It can be seen that compared with the blank control and the materials using metal organic framework materials alone and carbon quantum dots alone, the functional carrier material CQDs@MOFs used in embodiment 5 fixed the metal organic framework materials and carbon quantum dots on the fixed carrier for the bacterial and algal system to treat sewage, which improved the degradation of organic matter and CO2 enrichment and This is because the present invention not only utilizes the excellent characteristics of carbon quantum dots such as ultraviolet absorption and photoluminescence to improve the utilization of solar energy, but also allows microalgae to directly receive the emitted light of carbon quantum dots as supplementary light energy input for photosynthesis, thereby improving its photosynthesis efficiency. It also further combines MOF materials and carbon quantum dots into fixed carriers for the attachment of bacteria and algae in the bacteria-algae system and provides local high CO2 concentration and emission light wavelength, thereby promoting photosynthesis to absorb and convert CO2 and release more O2 to supply the growth and metabolism of heterotrophic bacteria, providing a favorable microenvironment of high CO2 and supplementary light energy for the bacteria and algae microorganisms in the system, and the two work together to further enhance the organic matter degradation and carbon fixation efficiency of the entire system.

[0153] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, can implement the present invention in a wider range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principle of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departing from the disclosed scope in the application and the changes made with conventional techniques known in the art.

Claims

1. A method for treating bacterial and algal wastewater, characterized in that: The steps include: The functional carrier material for bacteria-algae wastewater treatment is added into the bacteria-algae system, and the wastewater is used as the reaction liquid to treat the wastewater under natural light and in a closed state without aeration; The functional carrier material for treating bacteria and algae wastewater includes metal organic framework materials, carbon quantum dots and fixed carriers; The metal organic framework material uses iron and zinc as metals and trimesic acid as an organic ligand; The carbon quantum dots are made from bacterial and algal biomass recovered from a bacterial and algal wastewater treatment system; The fixed carrier is any one of polyurethane sponge, nylon net, cotton cloth and polyester fiber.

2. The method for treating bacteria and algae wastewater according to claim 1, characterized in that: In the bacteria-algae system, the bacteria are activated sludge bacteria, and the algae are one or more of Chlorella, Scenedesmus, Arthrospira platensis, Monospinipes, and Leucophaga; The mass ratio of bacteria to algae in the bacteria-algae system is 4:1; The initial addition concentration of the bacteria and algae biomass in the bacteria and algae system is 2 g / L.

3. The method for treating bacteria and algae wastewater according to any one of claims 1 to 2, characterized in that: In the functional carrier material for treating bacteria and algae wastewater, the ratio of the mass of the metal organic framework material, the mass of the carbon quantum dots and the volume of the fixed carrier is 0.3125 mg: 0.125 mg: 1 cm³; The volume of the functional carrier material for bacteria-algae wastewater treatment is 30% of the volume of the bacteria-algae system.

4. The method for treating bacteria and algae wastewater according to claim 1, characterized in that: The method for preparing the metal organic framework material comprises the following steps: a1) dispersing iron salt, zinc salt and trimesic acid in a solvent, stirring, and collecting the precipitated product; The molar ratio of the iron salt, the zinc salt and the trimesic acid is 1:1:1; a2) drying and calcining the precipitated product in sequence to obtain the metal organic framework material; The drying temperature is 70 to 105°C and the drying time is 6 to 15 hours; The calcination temperature is 350° C. and the calcination time is 4 to 8 h.

5. The method for treating bacteria and algae wastewater according to claim 1, characterized in that: The method for preparing carbon quantum dots comprises the following steps: b1) dispersing the bacterial and algal biomass recovered from the bacterial and algal domestic sewage treatment system in water, heating it for hydrothermal reaction, and collecting the supernatant by centrifugation after the reaction is completed; Every 1-5 g of the bacterial and algal biomass is dispersed in 10-50 mL of water; The temperature of the hydrothermal reaction is 150-200°C and the time is 2-4 h; b2) placing the supernatant in a dialysis bag and immersing the dialysis bag in water for dialysis, and collecting the liquid in the bag for freeze-drying after the dialysis is completed to obtain the carbon quantum dots; In the dialysis step, the cutoff capacity of the dialysis bag is 1000 Da.

6. The method for treating bacteria and algae wastewater according to claim 1, characterized in that: The method for preparing the functional carrier material for treating bacteria and algae wastewater comprises the following steps: 1) mixing the metal organic framework material and the adhesive in a solvent, adding the fixed carrier to perform a first impregnation treatment, and drying after the treatment to obtain an intermediate carrier; 2) dissolving the carbon quantum dots in a glutaraldehyde solution, adding the intermediate carrier to perform a second impregnation treatment, and drying after the treatment to obtain the functional carrier material for bacteria and algae wastewater treatment.

7. The method for treating bacteria and algae wastewater according to claim 1, characterized in that: The sewage is domestic sewage.

8. A functional carrier material for bacterial and algal wastewater treatment, characterized in that: Including metal organic framework materials, carbon quantum dots and fixed carriers; The metal organic framework material uses iron and zinc as metals and trimesic acid as an organic ligand; The carbon quantum dots are made from bacterial and algal biomass recovered from a bacterial and algal wastewater treatment system; The fixed carrier is any one of polyurethane sponge, nylon mesh, cotton cloth, and polyester fiber; The ratio of the mass of the metal organic framework material, the mass of the carbon quantum dots and the volume of the fixed carrier is (0.3-1.25) mg: (0.05-0.2) mg: 1 cm³.

9. The method for preparing the functional carrier material for treating bacteria and algae wastewater according to claim 8 comprises the following steps: 1) mixing the metal organic framework material and the adhesive in a solvent, adding the fixed carrier to perform a first impregnation treatment, and drying after the treatment to obtain an intermediate carrier; 2) dissolving the carbon quantum dots in a glutaraldehyde solution, adding the intermediate carrier to perform a second impregnation treatment, and drying after the treatment to obtain the functional carrier material for bacteria and algae wastewater treatment.

10. The method for preparing a functional carrier material for treating bacteria and algae wastewater according to claim 9, characterized in that: The method for preparing the metal organic framework material comprises the following steps: a1) dispersing iron salt, zinc salt and trimesic acid in a solvent, stirring, and collecting the precipitated product; The molar ratio of the iron salt, the zinc salt and the trimesic acid is 1:1:1; The solvent is ethanol, and 5.04 g of trimesic acid is added to every 46 mL of the ethanol; The stirring speed is 100 rpm to 300 rpm, and the time is 40 to 60 h; a2) drying and calcining the precipitated product in sequence to obtain the metal organic framework material; The drying temperature is 70 to 105°C and the drying time is 6 to 15 hours; The calcination temperature is 350°C and the calcination time is 4 to 8 hours; In step 1), the adhesive is polyvinylidene fluoride; In step 1), the solvent is N,N-dimethylformamide; The first immersion treatment is to repeatedly squeeze the fixed carrier in the mixed solution so that the gaps in the fixed carrier are fully in contact with the mixed solution, and at the same time, the mixed solution is ultrasonicated for 2 to 5 hours; The method for preparing carbon quantum dots comprises the following steps: b1) dispersing the bacterial and algal biomass recovered from the bacterial and algal domestic sewage treatment system in water, heating it for hydrothermal reaction, and collecting the supernatant by centrifugation after the reaction is completed; Every 1-5 g of the bacterial and algal biomass is dispersed in 10-50 mL of water; The temperature of the hydrothermal reaction is 150-200°C and the time is 2-4 h; The centrifugal speed is 8000-10000 rpm, and the time is 20-30 min; b2) placing the supernatant in a dialysis bag and immersing the dialysis bag in water for dialysis, and collecting the liquid in the bag for freeze-drying after the dialysis is completed to obtain the carbon quantum dots; In the dialysis step, the cutoff of the dialysis bag is 1000 Da, the dialysis time is 36 to 60 h, and the water is changed at least 3 times during the dialysis step; The mass ratio of the metal organic framework material to the adhesive polyvinylidene fluoride resin is (1-2): 1; In step 2), 15 to 25 mg of the carbon quantum dots are dissolved in 10 to 50 mL of a glutaraldehyde solution having a mass concentration of 2.5 to 5%; The second impregnation treatment is soaking, and the soaking time is 3 to 5 hours; The drying temperature is 60-80° C. and the drying time is 10-12 h.

Images