Integrated microalgae rotating biofilm-membrane bioreactor without conveyor belt

Abstract

The application relates to an integrated microalgae rotary biofilm-membrane bioreactor without a conveying belt. A partition plate is detachably installed in the middle of a reaction tank and divides the reaction tank into a membrane bioreaction chamber and a microalgae rotary biofilm culture chamber; a fixing frame is fixedly connected in the microalgae rotary biofilm culture chamber; a lower roller is installed at the lower left end of the fixing frame, and an upper roller is installed at the upper right end of the fixing frame; a microalgae biofilm carrier belt is obliquely wound on the lower roller and the upper roller; a scraper is vertically and adjustably fixed on the fixing frame and is located below the upper roller and is spaced apart from the microalgae biofilm carrier belt by a certain distance; a microalgae collecting groove is fixed on the right side of the scraper; culture chamber aeration pipes and reaction chamber aeration pipes are installed on the bottom plate of the reaction tank, and air pumps are connected with the culture chamber aeration pipes and the reaction chamber aeration pipes respectively; a membrane assembly is detachably installed in the membrane bioreaction chamber through a clamping groove; and a peristaltic pump is connected with the membrane assembly through a water outlet pipe.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to an integrated conveyor belt-free microalgae rotary biofilm-membrane bioreactor. Background Technology

[0002] Microalgae can effectively utilize nutrients in wastewater through photosynthesis and convert them into biomass, producing valuable lipids, carbohydrates, proteins, pigments, etc., which can then be used to develop biofuels and biochemicals. Simultaneously, they remove nitrogen and phosphorus nutrients from wastewater. Compared to traditional plants, microalgae have advantages such as high photosynthetic efficiency, CO2 fixation, and rapid growth, showing great potential in wastewater treatment, biomass energy, and CO2 fixation.

[0003] Given their inherent advantages, microalgae have attracted widespread attention in wastewater treatment. However, wastewater exhibits heterogeneity characterized by high turbidity, high color, high salinity, and high ammonia nitrogen levels. High turbidity and color significantly reduce light transmittance, thus affecting microalgae photosynthesis, making microalgae cultivation challenging. Furthermore, the low cell density of microalgae, often suspended in water, greatly complicates harvesting. Traditional harvesting methods such as flocculation, centrifugation, and filtration are typically time-consuming and labor-intensive, which are key factors limiting microalgae wastewater purification. Microalgae biofilm cultivation allows for long-term or intermittent exposure to air. Since light directly affects the algal cells, the light penetration problem commonly encountered in suspension culture is greatly alleviated in microalgae biofilm cultivation systems. Simultaneously, microalgae attached to the biofilm carrier can be harvested simply by scraping, overcoming the harvesting difficulties of suspension culture. However, during the microalgae attachment and growth process, the biofilm may detach, leaving some microalgae suspended in the reactor, affecting the stability of the effluent quality. Therefore, there is currently a lack of cost-effective training methods.

[0004] In existing microalgae wastewater treatment technologies, the high turbidity and color of the wastewater significantly reduce light transmittance, thus affecting microalgae photosynthesis. The low concentration of the algal solution produced after cultivation and the individual suspended state of the microalgae cells pose significant challenges to harvesting. Traditional operations such as flocculation sedimentation, centrifugation, and filtration are typically time-consuming, labor-intensive, and expensive, further reducing the overall economic efficiency of the system. For example, Chinese invention patent application "A Water Environment Remediation Device and Process" (CN115159771A) achieves double-sided cultivation of microalgae using vertically distributed cylindrical and disc-shaped microalgae biofilms. An internal rotating shaft increases the utilization rate of light by the microalgae, providing the necessary light environment for growth. This allows the microalgae to utilize nutrients such as N and P in eutrophic water for abundant growth and reproduction, significantly reducing the load on subsequent biological systems, decreasing sludge production, and lowering system costs. However, this device is difficult to harvest, and the microalgae cultivation reactor is complex. For example, the Chinese utility model patent application "A Conveyor Belt Type Rotating Biofilm Reactor for Algae" (CN208151054U) describes a method where algal cells are attached to a wall-adhering material and fixed on a vertical conveyor belt, rotating in a nutrient-rich wastewater and CO2-rich air environment. When the microalgae film reaches a certain thickness, it is harvested with a scraper and used as microalgae fertilizer, reducing harvesting costs and improving economic efficiency. However, during the algae's growth, the biofilm is prone to detachment, leading to unstable effluent quality in the system. Summary of the Invention

[0005] To address the aforementioned technical problems, the purpose of this invention is to provide an integrated conveyor-free rotary microalgae biofilm-membrane bioreactor. This reactor utilizes nutrients in wastewater to provide a favorable environment for microalgae growth while maximizing wastewater purification. It provides a good growth environment for microalgae, fully utilizes nutrients such as nitrogen and phosphorus in wastewater for growth, and facilitates harvesting while improving effluent quality.

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

[0007] An integrated conveyor-free microalgae rotating biofilm-membrane bioreactor includes a drive roller 1, a fixed frame 2, a scraper 3, a microalgae collection tank 4, a reaction tank 5, a culture chamber aeration pipe 6, a lower roller 7, a partition 9, an air pump 10, a reaction chamber aeration pipe 12, a membrane module 13, a peristaltic pump 15, a microalgae biofilm carrier belt 16, a low-speed motor 18, and an upper roller 19.

[0008] The partition 9 is detachably installed in the middle of the reaction tank 5 via a slot, dividing the reaction tank 5 from left to right into a membrane bioreactor chamber and a microalgae rotating biofilm culture chamber.

[0009] The fixed frame 2 is fixedly connected to the microalgae rotating biofilm culture chamber; the lower roller 7 is installed on the lower left end of the fixed frame 2 via the lower roller shaft 8, and the upper roller 19 is installed on the upper right end of the fixed frame 2 via the upper roller shaft 20; the microalgae biofilm carrier belt 16 is obliquely wound around the lower roller 7 and the upper roller 19. During operation, the lower middle part of the microalgae biofilm carrier belt 16 is immersed in the mixture of algae solution and wastewater, while the other part is exposed to the air; the low-speed motor 18 is fixedly connected to the upper right end of the fixed frame 2, and the drive roller 1 is fixedly connected to the power output shaft of the low-speed motor 18. The drive roller 1 is in close contact with the algae biofilm carrier belt 16 on the outer side of the upper roller 19, and drives the microalgae biofilm carrier belt 16 to rotate through friction.

[0010] The scraper 3 is vertically and adjustablely fixed to the frame 2, located below the upper roller 19, and spaced a certain distance from the microalgae biofilm carrier belt 16; the microalgae collection tank 4 is fixed to the right side of the scraper 3. As the microalgae biofilm carrier belt 16 rotates, the microalgae attached to the microalgae biofilm carrier belt 16 and accumulating to a certain thickness are scraped off by the scraper 3 into the microalgae collection tank 4.

[0011] The aeration pipe 6 in the culture chamber and the aeration pipe 12 in the reaction chamber are installed on the bottom plate of the reaction tank 5. The aeration pipe 6 in the culture chamber is located in the microalgae rotating biofilm culture chamber, and the aeration pipe 12 in the reaction chamber is located in the membrane bioreactor chamber. The air pump 10 is connected to the aeration pipe 6 in the culture chamber and the aeration pipe 12 in the reaction chamber through the air inlet pipe 11.

[0012] The membrane module 13 is detachably installed in the membrane bioreactor chamber via a slot; the peristaltic pump 15 is connected to the membrane module 13 via an outlet pipe 14.

[0013] The microalgae biofilm carrier belt 16 is one of the following flexible materials: nylon cloth, cotton cloth, canvas, linen, or polyester.

[0014] The membrane module 13 is a flat ceramic membrane or a hollow fiber membrane.

[0015] The low-speed motor 18 is a variable frequency motor, which changes the rotational speed of the microalgae biofilm carrier belt 16, thereby changing the gas-liquid exchange frequency during the microalgae growth process.

[0016] The membrane of the membrane module 13 is made of polyvinylidene fluoride, polyacrylonitrile, polyethersulfone, cellulose acetate, polysulfone, polyamide, cellulose ester or regenerated cellulose.

[0017] The membrane of the membrane module 13 has a pore size of 0.05 to 0.2 μm.

[0018] The reaction tank 5 is made of transparent acrylic; its dimensions are 600 mm long × 300 mm wide × 150 mm high.

[0019] The bottom of the reaction tank 5 is provided with a liquid outlet 17.

[0020] The microalgae collection tank 4 is equipped with an algae discharge port at its right end.

[0021] The aeration pipe 6 in the culture chamber and the aeration pipe 12 in the reaction chamber are arranged in a serpentine pattern.

[0022] The microalgae in the algal solution are one or more of Chlorella, Scenedesmus, and Dunaliella salina; the wastewater is one or more of municipal wastewater, biogas slurry, livestock and poultry wastewater, dairy wastewater, landfill leachate, and printing wastewater.

[0023] A control method for an integrated conveyor-free rotating microalgae biofilm-membrane bioreactor includes the following steps:

[0024] S1. Immerse all components of the microalgae rotating biofilm-membrane bioreactor in NaClO for 24 hours; after disinfection, clean the components with clean water at least three times.

[0025] S2. Add algal solution and wastewater to the microalgae rotating biofilm culture chamber of reaction tank 5, maintaining the liquid level at 80-100 mm. This ensures the lower and middle parts of the microalgae biofilm carrier belt 16 are submerged in the mixture of algal solution and wastewater, while the remaining parts are exposed to air. Aeration is provided to the microalgae rotating biofilm culture chamber of reaction tank 5 via air pump 10 and aeration pipe 6, initiating microalgae cultivation. The cultivation temperature is 20-25℃. LED lights are used to provide illumination to reaction tank 5 at an intensity of 4000-8000 lux. Regularly apply light to the microalgae in reaction tank 5. Water is replenished in the rotating algae biofilm culture chamber. During the culture process, a low-speed motor 18 drives the microalgae biofilm carrier belt 16 to rotate. Microalgae are adsorbed onto the microalgae biofilm carrier belt 16 and grow continuously. Intermittently, the microalgae come into contact with air (CO2) and nutrients in the culture medium for gas-liquid exchange. As the microalgae biofilm carrier belt 16 rotates, the microalgae that have adhered to the microalgae biofilm carrier belt 16 and accumulated to a certain thickness are scraped off by the scraper 3 into the microalgae collection tank 4. At the same time, most of the N, P, COD, heavy metals, and antibiotics in the wastewater are removed.

[0026] S3. After a certain period of cultivation, the intermediate partition 9 is opened to allow the treated wastewater to flow from the microalgae rotating biofilm culture chamber to the membrane bioreactor chamber. Aeration is carried out in the membrane bioreactor chamber through the air pump 10 and the aeration pipe 12. After filtration by the membrane module 3, N, P, COD, heavy metals and antibiotics in the wastewater are further removed, and microalgae suspended in the wastewater are intercepted. Finally, the wastewater is discharged through the peristaltic pump 15.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention combines microalgae biofilm attachment culture and membrane concentration culture technology, which results in better microalgae harvesting and wastewater purification when cultivating microalgae in high-turbidity wastewater, improves effluent quality, and enhances the absorption of nutrients such as N and P.

[0029] The rotating microalgae biofilm culture system of the present invention has a simple structure, is easy to operate, and has flexible equipment adjustment. It adopts a transparent culture device with three-sided lighting and increases the light irradiation of microalgae by rotating, providing sufficient light conditions for microalgae growth and enhancing photosynthesis.

[0030] The friction between the rollers and the biofilm carrier drives the movement of the biofilm carrier, reducing the need for fixing or adhering the biofilm carrier, and making the biofilm carrier easy to replace. Attached Figure Description

[0031] Figure 1 This is a three-dimensional structural schematic diagram of the integrated conveyor-free microalgae rotary biofilm-membrane bioreactor of the present invention;

[0032] Figure 2 This is a cross-sectional schematic diagram of the integrated conveyor-free microalgae rotary biofilm-membrane bioreactor of the present invention.

[0033] Figure 3 This is a top view schematic diagram of the integrated conveyor-free microalgae rotary biofilm-membrane bioreactor of the present invention.

[0034] Figure 4 This is a partial structural schematic diagram of the integrated conveyor-free microalgae rotary biofilm-membrane bioreactor of the present invention;

[0035] Figure 5 This is a schematic diagram of the scraper 3 and the microalgae collection tank 4 of the present invention.

[0036] The reference numerals in the attached figures are:

[0037] 1. Drive roller 2. Fixture

[0038] 3 scrapers 4 microalgae collection tank

[0039] 5. Reaction tank; 6. Culture chamber aeration pipe

[0040] 7 lower rollers 8 lower roller shafts

[0041] 9 partitions 10 air pumps

[0042] 11 Inlet pipe 12 Reaction chamber aeration pipe

[0043] 13 Membrane module 14 Outlet pipe

[0044] 15 Peristaltic pumps 16 Microalgae biofilm carrier belt

[0045] 17 Liquid outlet 18 Low-speed motor

[0046] 19 Upper Roller 20 Upper Roller Shaft Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0048] like Figures 1-3 As shown, an integrated conveyor-free microalgae rotating biofilm-membrane bioreactor includes a drive roller 1, a fixed frame 2, a scraper 3, a microalgae collection tank 4, a reaction tank 5, a culture chamber aeration pipe 6, a lower roller 7, a lower roller shaft 8, a partition 9, an air pump 10, a reaction chamber aeration pipe 12, a membrane module 13, an outlet pipe 14, a peristaltic pump 15, a microalgae biofilm carrier belt 16, a liquid outlet 17, a low-speed motor 18, an upper roller 19, and an upper roller shaft 20.

[0049] The partition 9 is detachably installed in the middle of the reaction tank 5 via a slot, dividing the reaction tank 5 from left to right into a membrane bioreactor chamber and a microalgae rotating biofilm culture chamber; the bottom of the reaction tank 5 is provided with an outlet 17.

[0050] The fixed frame 2 is fixedly connected to the microalgae rotating biofilm culture chamber; the lower roller 7 is installed on the lower left end of the fixed frame 2 via the lower roller shaft 8, and the upper roller 19 is installed on the upper right end of the fixed frame 2 via the upper roller shaft 20; the microalgae biofilm carrier belt 16 is obliquely wound around the lower roller 7 and the upper roller 19. During operation, the lower middle part of the microalgae biofilm carrier belt 16 is immersed in the mixture of algae solution and wastewater, while the other part is exposed to the air; the low-speed motor 18 is fixedly connected to the upper right end of the fixed frame 2, and the drive roller 1 is fixedly connected to the power output shaft of the low-speed motor 18. The drive roller 1 is in close contact with the algae biofilm carrier belt 16 on the outer side of the upper roller 19, and drives the microalgae biofilm carrier belt 16 to rotate through friction.

[0051] like Figure 4 and Figure 5 As shown, the scraper 3 is vertically and adjustablely fixed to the mounting frame 2, located below the upper roller 19, and spaced a certain distance from the microalgae biofilm carrier belt 16. The microalgae collection tank 4 is fixed to the right side of the scraper 3. As the microalgae biofilm carrier belt 16 rotates, the microalgae attached to the microalgae biofilm carrier belt 16 and accumulating to a certain thickness are scraped off by the scraper 3 into the microalgae collection tank 4. The right end of the microalgae collection tank 4 is provided with an algae discharge port.

[0052] like Figure 2 and Figure 5As shown, the aeration pipe 6 in the culture chamber and the aeration pipe 12 in the reaction chamber are installed on the bottom plate of the reaction tank 5. The aeration pipe 6 in the culture chamber is located in the microalgae rotating biofilm culture chamber, and the aeration pipe 12 in the reaction chamber is located in the membrane bioreactor chamber. The air pump 10 is connected to the aeration pipe 6 in the culture chamber and the aeration pipe 12 in the reaction chamber through the air inlet pipe 11. The aeration pipe 6 in the culture chamber and the aeration pipe 12 in the reaction chamber are arranged in a serpentine pattern.

[0053] The membrane module 13 is detachably installed in the membrane bioreactor chamber via a slot; the peristaltic pump 15 is connected to the membrane module 13 via an outlet pipe 14.

[0054] Furthermore, the microalgae biofilm carrier belt 16 is one of the following flexible materials: nylon cloth, cotton cloth, canvas, linen, and polyester.

[0055] Furthermore, the low-speed motor 18 is an adjustable frequency converter motor, which changes the rotation speed of the microalgae biofilm carrier belt 16, thereby changing the gas-liquid exchange frequency during the microalgae growth process.

[0056] Furthermore, the position of the scraper 3 can be adjusted, thereby allowing for the scraping of microalgae of different thicknesses.

[0057] Furthermore, the membrane module 13 is a flat ceramic membrane or a hollow fiber membrane; the membrane material is polyvinylidene fluoride, polyacrylonitrile, polyethersulfone, cellulose acetate, polysulfone, polyamide, cellulose ester or regenerated cellulose; the membrane pore size is 0.05 to 0.2 μm.

[0058] The reaction tank 5 is made of transparent acrylic, which has good light transmittance, and its dimensions are 600 mm long × 300 mm wide × 150 mm high.

[0059] In this embodiment, the microalgae in the algal solution are one or more of Chlorella, Scenedesmus, and Dunaliella salina.

[0060] In this embodiment, the wastewater is one or more of the following: municipal wastewater, biogas slurry, livestock and poultry wastewater, dairy wastewater, landfill leachate, and printing wastewater.

[0061] A method for controlling a microalgae rotating biofilm-membrane bioreactor specifically includes the following steps:

[0062] S1. Immerse all components of the microalgae rotating biofilm-membrane bioreactor in NaClO for 24 hours; after disinfection, clean the components with clean water at least three times.

[0063] S2. Add algal solution and wastewater to the microalgae rotating biofilm culture chamber, maintaining the liquid level at 80-100 mm. The lower and middle parts of the microalgae biofilm carrier belt 16 are submerged in the mixture of algal solution and wastewater, while the rest is exposed to air. Aeration is provided to the microalgae rotating biofilm culture chamber in reaction tank 5 via air pump 10 and aeration pipe 6, initiating microalgae cultivation. The cultivation temperature is 20-25℃. LED lights provide three-sided illumination (top and left / right sides) to reaction tank 5, with a light intensity of 4000-8000 lux. Regularly add oxygen to the microalgae in reaction tank 5. Water is replenished in the rotating biofilm culture chamber; during the culture process, the microalgae biofilm carrier belt 16 is driven to rotate by a low-speed motor 18, and the microalgae are adsorbed on the microalgae biofilm carrier belt 16 and grow continuously. The microalgae are intermittently exposed to air-CO2 and nutrients in the culture medium for gas-liquid exchange. As the microalgae biofilm carrier belt 16 rotates, the microalgae attached to the microalgae biofilm carrier belt 16 and accumulating to a certain thickness are scraped off by the scraper 3 into the microalgae collection tank 4; at the same time, a large amount (about 80% to 90%) of N, P, COD, heavy metals and antibiotics in the wastewater are removed.

[0064] S3. After a certain cultivation period, the intermediate partition 9 is opened, allowing the treated wastewater to flow from the microalgae rotating biofilm cultivation chamber to the membrane bioreactor chamber. Aeration is then introduced into the membrane bioreactor chamber via the air pump 10 and the aeration pipe 12. After filtration by the membrane module 3, N, P, COD, heavy metals, and antibiotics in the wastewater are further removed, and suspended microalgae are intercepted. Finally, the wastewater is discharged via the peristaltic pump 15. The final removal rate of N, P, COD, heavy metals, and antibiotics in the wastewater reaches over 95%.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An integrated conveyor-free microalgae rotating biofilm-membrane bioreactor, characterized in that, The integrated conveyorless microalgae rotating biofilm-membrane bioreactor includes a drive roller (1), a fixed frame (2), a scraper (3), a microalgae collection tank (4), a reaction tank (5), a culture chamber aeration pipe (6), a lower roller (7), a partition (9), an air pump (10), a reaction chamber aeration pipe (12), a membrane module (13), a peristaltic pump (15), a microalgae biofilm carrier belt (16), a low-speed motor (18), and an upper roller (19). The partition (9) is detachably installed in the middle of the reaction tank (5) through a slot, dividing the reaction tank (5) from left to right into a membrane bioreactor and a microalgae rotating biofilm culture chamber; the reaction tank (5) is made of transparent acrylic and is illuminated on three sides. The fixed frame (2) is fixed in the microalgae rotating biofilm culture chamber; the lower roller (7) is installed on the lower left end of the fixed frame (2) via the lower roller shaft (8), and the upper roller (19) is installed on the upper right end of the fixed frame (2) via the upper roller shaft (20); the microalgae biofilm carrier belt (16) is obliquely wound around the lower roller (7) and the upper roller (19). During operation, the lower middle part of the microalgae biofilm carrier belt (16) is immersed in the mixture of algae solution and wastewater, while the other part is exposed to the air; The low-speed motor (18) is fixed to the upper right end of the fixed frame (2), and the drive roller (1) is fixed to the power output shaft of the low-speed motor (18). The drive roller (1) is in close contact with the algal biofilm carrier belt (16) on the outside of the upper roller (19), and drives the microalgal biofilm carrier belt (16) to rotate through friction. There is no additional transmission mechanism. The low-speed motor (18) is a variable frequency motor. By changing the rotation speed of the microalgal biofilm carrier belt (16), the gas-liquid exchange frequency during the microalgal growth process is changed. The scraper (3) is vertically and is fixedly mounted on the fixed frame (2) in an adjustable position. It is located below the upper roller (19) and is spaced a certain distance from the microalgae biofilm carrier belt (16). The microalgae collection tank (4) is fixedly mounted on the right side of the scraper (3). As the microalgae biofilm carrier belt (16) rotates, the microalgae attached to the microalgae biofilm carrier belt (16) and accumulated to a certain thickness are scraped off by the scraper (3) into the microalgae collection tank (4). The aeration pipe (6) in the culture chamber and the aeration pipe (12) in the reaction chamber are installed on the bottom plate of the reaction tank (5). The aeration pipe (6) in the culture chamber is located in the microalgae rotating biofilm culture chamber, and the aeration pipe (12) in the reaction chamber is located in the membrane bioreactor chamber. The air pump (10) is connected to the aeration pipe (6) in the culture chamber and the aeration pipe (12) in the reaction chamber through the air inlet pipe (11). The aeration pipe (6) in the culture chamber and the aeration pipe (12) in the reaction chamber are arranged in a serpentine pattern. The membrane module (13) is detachably installed in the membrane bioreactor chamber via a slot; the peristaltic pump (15) is connected to the membrane module (13) via an outlet pipe (14); The microalgae biofilm carrier belt (16) is one of the following flexible materials: nylon cloth, cotton cloth, canvas, linen, polyester; The membrane module (13) is a flat ceramic membrane or a hollow fiber membrane.

2. The integrated conveyorless microalgae rotating biofilm-membrane bioreactor according to claim 1, characterized in that, The membrane of the membrane module (13) is made of polyvinylidene fluoride, polyacrylonitrile, polyethersulfone, cellulose acetate, polysulfone, polyamide, cellulose ester or regenerated cellulose; the pore size of the membrane of the membrane module (13) is 0.05~0.2 μm.

3. The integrated conveyorless microalgae rotating biofilm-membrane bioreactor according to claim 1, characterized in that, The bottom of the reaction tank (5) is provided with an outlet (17); the right end of the microalgae collection tank (4) is provided with an algae discharge port.

4. The integrated conveyorless microalgae rotating biofilm-membrane bioreactor according to claim 1, characterized in that, The microalgae in the algal solution are one or more of Chlorella, Scenedesmus, and Dunaliella salina; the wastewater is one or more of municipal wastewater, biogas slurry, livestock and poultry wastewater, dairy wastewater, landfill leachate, and printing wastewater.

5. A control method for an integrated conveyorless microalgae rotating biofilm-membrane bioreactor as described in any one of claims 1-4, characterized in that, The control method includes the following steps: S1. Immerse all components of the microalgae rotating biofilm-membrane bioreactor in NaClO for 24 hours; after disinfection, clean the components with clean water. S2. Add algal solution and wastewater to the microalgae rotating biofilm culture chamber of the reaction tank (5), keeping the liquid level at 80-100 mm. This allows the lower part of the microalgae biofilm carrier belt (16) to be submerged in the mixture of algal solution and wastewater, while the rest is exposed to air. Aeration is then provided to the microalgae rotating biofilm culture chamber of the reaction tank (5) via an air pump (10) and aeration pipe (6) to begin microalgae cultivation. The cultivation temperature is 20-25°C. LED lights are used to provide illumination to the reaction tank (5) at a light intensity of 4000-8000 lux. The microalgae in the reaction tank (5) are periodically aerated. Water is added to the rotating biofilm culture chamber; during the culture process, the microalgae biofilm carrier belt (16) is driven to rotate by a low-speed motor (18). The microalgae are adsorbed on the microalgae biofilm carrier belt (16) and grow continuously. The microalgae are intermittently contacted with CO2-containing air and nutrients in the culture medium to carry out gas-liquid exchange. As the microalgae biofilm carrier belt (16) rotates, the microalgae attached to the microalgae biofilm carrier belt (16) and accumulated to a certain thickness are scraped off by the scraper (3) into the microalgae collection tank (4); at the same time, most of the N, P, COD, heavy metals and antibiotics in the wastewater are removed. S3. After a certain period of cultivation, open the middle partition (9) to allow the treated wastewater to flow from the microalgae rotating biofilm culture chamber to the membrane bioreactor chamber; aeration is carried out in the membrane bioreactor chamber through the air pump (10) and the aeration pipe (12) of the reaction chamber; after filtration by the membrane module (13), N, P, COD, heavy metals and antibiotics in the wastewater are further removed, and microalgae suspended in the wastewater are intercepted; finally, the wastewater is discharged through the peristaltic pump (15).

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