Micro-magnetic carrier type bacteria-algae biofilm reactor and application thereof

Abstract

The application discloses a kind of micro-magnetic carrier type bacteria alga biofilm reactor and its application, the upper portion of the micro-magnetic carrier type bacteria alga biofilm reactor is equipped with water inlet, the top middle of the micro-magnetic carrier type bacteria alga biofilm reactor is equipped with lamp tube extending inward, the inside of the micro-magnetic carrier type bacteria alga biofilm reactor is equipped with porous cloth gas distribution plate, the bottom of the porous cloth gas distribution plate is connected with aeration head by air pipe, the outside of aeration head is connected with air pump, the lower portion of the sidewall of the micro-magnetic carrier type bacteria alga biofilm reactor is equipped with water outlet, the micro-magnetic carrier type bacteria alga biofilm reactor is equipped with micro-magnetic carrier filler.The micro-magnetic carrier type bacteria alga biofilm reactor is used to treat wastewater, the micro-magnetic effect of micro-magnetic carrier filler is used to promote microbial electron transfer activity and energy metabolism activity, so that alga biofilm has higher carbon fixation and denitrification efficiency, so as to improve the operation efficiency of bacteria alga biofilm type sewage treatment system.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of high-efficiency low-consumption bacteria-algae coupling symbiosis sewage treatment device and sewage treatment method for sewage denitrification and carbon fixation, especially design a kind of high-efficiency denitrification carbon fixation algal biofilm reactor based on micro-magnetic carrier and its application, belong to sewage treatment technical field. BACKGROUND

[0002] The current mainstream sewage treatment process often uses activated sludge method, which has high aeration energy consumption and needs external carbon source for advanced denitrification. Algal biofilm technology has lower dependence on carbon source, greatly reducing chemical consumption. Moreover, while denitrifying and dephosphorizing, it can also fix carbon and produce oxygen through photosynthesis, reducing the aeration demand of the sewage treatment system. The biomass formed can also be used for energy production, generating economic benefits. It is a promising low-carbon sewage treatment technology. However, algal biofilm has the problems of slow growth and low denitrification and carbon fixation rate, which to some extent hinders the popularization and application of this process. It is urgent to develop an algal biofilm reactor with high-efficiency denitrification and carbon fixation.

[0003] CN114149084A discloses a plug flow bacteria-algae biofilm system, which includes a reactor body, a flow guide assembly and hollow fillers. The flow guide assembly divides the box into several areas, and the hollow fillers are inoculated with microalgae. Microalgae and bacteria continuously attach and grow on the inner and outer surfaces of the hollow fillers, forming a biofilm. The biofilm fully contacts with pollutants in the water body and adsorbs and degrades them, purifying the water quality. The above-mentioned technology uses ordinary fillers, which only provide a substrate for microbial attachment and growth. The biofilm formation is slow and the carbon fixation and denitrification efficiency of the algal biofilm cannot be enhanced. SUMMARY

[0004] The purpose of the present application is to provide an algal biofilm reactor using micro-magnetic carriers to load biomass, i.e. a micro-magnetic carrier type bacteria-algae biofilm reactor. The second purpose of the present application is to provide the application of the micro-magnetic carrier type bacteria-algae biofilm reactor in treating wastewater. The micro-magnetic effect of the carrier promotes microbial electron transfer activity and energy metabolism activity, enabling the algal biofilm to have higher carbon fixation and denitrification efficiency, thereby improving the operating efficiency of the bacteria-algae biofilm type sewage treatment system.

[0005] Technical solution: The micro-magnetic carrier type bacteria-algae biofilm reactor of the present application is provided with a water inlet at the upper part, a lamp tube extending inwardly at the top middle, a porous air distribution plate inside, an aeration head connected to the bottom of the air distribution plate through an air pipe, an air pump connected to the outside of the aeration head, a water outlet at the lower part of the side wall, and micro-magnetic carrier fillers inside the reactor.

[0006] Further, the micro-magnetic carrier filler is filled in the micro-magnetic carrier type bacteria-algae biofilm reactor at a filling rate of 40-80%.

[0007] Further, the micro-magnetic carrier filler comprises high-density polyethylene, neodymium-iron-boron, hydrophilic adjuvant and electrophilic adjuvant, and the mass ratio of the high-density polyethylene, neodymium-iron-boron, hydrophilic adjuvant and electrophilic adjuvant is 100:2-14:2:1.

[0008] Further, the hydrophilic adjuvant is clinoptilolite, and the electrophilic adjuvant is iron oxide.

[0009] Further, the magnetic field strength of the micro-magnetic carrier filler is 0.3-1.5 mT.

[0010] Further, the micro-magnetic carrier filler is in a hollow spherical structure.

[0011] Further, the porous gas distribution plate is in an umbrella structure.

[0012] The micro-magnetic carrier type bacteria-algae biofilm reactor is used for treating wastewater.

[0013] The application further comprises a method for treating wastewater by using the micro-magnetic carrier type bacteria-algae biofilm reactor.

[0014] (1) A film-hanging stage: the alga-bacteria symbiotic community is added to the micro-magnetic carrier type bacteria-algae biofilm reactor, the alga-bacteria symbiotic community is inoculated on the micro-magnetic carrier filler, and a biofilm is formed on the inner and outer surfaces of the micro-magnetic carrier filler.

[0015] (2) A wastewater treatment stage: the wastewater enters the micro-magnetic carrier type bacteria-algae biofilm reactor through the water inlet, the light tube is set to control the illumination time, the gas pump of the aeration head is used for timed micro-aeration, the umbrella-shaped porous gas distribution plate is used to form the upflowing micro-bubbles in the micro-magnetic carrier type bacteria-algae biofilm reactor, the micro-magnetic carrier filler is fluidized and aerated, the biofilm on the micro-magnetic carrier filler fully contacts the pollutants in the wastewater and adsorbs and degrades the pollutants, and the wastewater is purified, and the purified water finally flows out from the water outlet.

[0016] Further, in step (1), the biofilm formation stage is to add the alga-bacteria symbiotic community into the micro-magnetic carrier type bacteria-algae biofilm reactor, the nutrient solution enters the micro-magnetic carrier type bacteria-algae biofilm reactor through the water inlet, the hydraulic retention time is maintained at 12-24h, the continuous light illumination is more than 15 days, the required light illumination conditions are provided for the growth and reproduction of microalgae and bacteria, the micro-aeration is performed by a gas pump at a time interval, the micro-aeration time interval is 0.5h every 3h, the umbrella-shaped porous gas distribution plate forms the upflowing micro-bubbles in the micro-magnetic carrier type bacteria-algae biofilm reactor, the micro-magnetic carrier packing is fluidized and aerated, and the microalgae and bacteria are continuously attached and grown on the inner and outer surfaces of the micro-magnetic carrier packing to form the biofilm.

[0017] Further, the nutrient solution contains carbon source, constant elements such as nitrogen, phosphorus, calcium, magnesium and trace elements such as iron, zinc, manganese and cobalt.

[0018] Further, in step (2), the wastewater treatment stage maintains the hydraulic retention time at 12-24h.

[0019] Further, in step (2), the light tube control sets the light illumination time length: dark time length = 0.5-3:1.

[0020] Further, in step (2), the time interval of the timed micro-aeration is 0.5h every 3h.

[0021] The present application uses a micro-magnetic carrier to load the biomass of the algal biofilm reactor, utilizes the micro-magnetic effect of the micro-magnetic carrier packing to promote the microbial electron transfer activity and energy metabolism activity, makes the algal biofilm have higher carbon fixation and denitrification efficiency, and thus improves the operation efficiency of the bacteria-algae biofilm type wastewater treatment system.

[0022] Advantages: Compared with the prior art, the present application has the following obvious advantages:

[0023] (1) The present application utilizes the magnetic field to strengthen the denitrification and carbon fixation efficiency of the algal biofilm, realizes the shortening of the biofilm formation period by 30% under the action of the magnetic field, removes 3.6%-14.3% more total nitrogen than the non-micro-magnetic carrier reactor, and improves the carbon fixation effect by 50%-150% than the non-micro-magnetic carrier reactor.

[0024] (2) In the denitrification aspect, the total nitrogen removal rate of the present application method reaches 97.5% at most, the total nitrogen concentration of the effluent is only 0.76mg / L, the removal rate is improved by 1.2%-14.3% than that under other magnetic field conditions, the ammonia nitrogen removal rate of the effluent is as high as 99.9%, and the nitrate nitrogen of the effluent is only 0.67mg / L.

[0025] (3) In the carbon fixation aspect, the chlorophyll content is as high as 0.854mg / L after adding the micro-magnetic carrier packing, which is 2.5 times of that without adding the magnetic field, indicating that the microalgae can absorb more carbon dioxide through photosynthesis.

[0026] (4) The algal biofilm of the present invention has a maximum amount of 2.2 mg, which is 2.2 times that of the one without magnetic field (1.0 mg). The protein accumulation is the highest at 31.39 mg / L and the polysaccharide accumulation is the highest at 15.12 mg / L. The algal biofilm after the micro magnetic carrier packing of the present invention has superior carbon fixation performance and also helps to deeply denitrify wastewater. Attached Figure Description

[0027] Figure 1 This is a front view of the micromagnetic carrier-type bacterial and algal biofilm reactor of the present invention;

[0028] Figure 2 This is a top view of the micromagnetic carrier-type bacterial and algal biofilm reactor of the present invention;

[0029] Figure 3 This is a schematic diagram of the structure of the micro magnetic carrier packing described in this invention;

[0030] Figure 4 This is a graph showing the changes in species composition of algal biofilm in Example 2, obtained from the wall of an aerobic reaction tank in an actual wastewater treatment plant, under the influence of micromagnetic carriers with different magnetic field intensities.

[0031] Figure 5 The graphs show the carbon fixation effect under different magnetic field strengths in Example 2.

[0032] Figure 6 The graph shows the denitrification effect under different magnetic field strengths in Example 2. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0034] Example 1

[0035] like Figures 1-2 As shown, this invention discloses a micro-magnetic carrier type algae biofilm reactor. The reactor has an inlet 1 at the top and a lamp 2 extending inward from the center of the top, which can be controlled by a timer switch. Inside the reactor is an umbrella-shaped porous air distribution plate 3, and at the bottom are aeration heads 4 connected to the porous air distribution plate 3 via air inlet pipes. The aeration heads 4 are connected to an air pump 5 for timed micro-aeration, with the aeration rate controlled by adjusting the air valve of the air pump 5. An outlet 7 is located at the lower part of the side wall of the reactor. The reactor is filled with micro-magnetic carrier packing material 6 at a filling rate of 40-80%.

[0036] like Figure 3As shown, the micro-magnetic carrier filler 6 is a mixture of high-density polyethylene and neodymium iron boron with different mass ratios (high-density polyethylene: neodymium iron boron mass ratio = 100:2-100:14), and a certain proportion of hydrophilic auxiliary material clinoptilolite (high-density polyethylene: clinoptilolite mass ratio = 100:2) and electrokinetic auxiliary material iron oxide (high-density polyethylene: iron oxide mass ratio = 100:1) are added to prepare composite modified micro-magnetic carrier fillers with different magnetic field strengths (0.3-1.5 mT). The composite modified micro-magnetic carrier filler itself is a hollow circular spherical structure. Due to its high specific surface area, algal biofilm can simultaneously attach and grow on the multi-layer structure of the composite modified micro-magnetic carrier filler, resulting in high biomass per unit volume.

[0037] The method for treating wastewater using the micro-magnetic carrier type algal biofilm reactor described above includes the following steps:

[0038] (1) Obtain the algal-bacterial symbiotic community from the wall of the actual wastewater treatment plant's aerobic reaction tank and add it to the micro-magnetic carrier type algal biofilm reactor. Inoculate the algal-bacterial symbiotic community on the micro-magnetic carrier filler 6, and continuously attach and grow microalgae and bacteria on the inner and outer surfaces of the filler to form a biofilm on the inner and outer surfaces of the micro-magnetic carrier filler 6.

[0039] (2) Waste water enters the micro-magnetic carrier type algal biofilm reactor through the water inlet 1, maintains a hydraulic retention time of 12-24 h, controls the light tube 2 to set the light duration: dark duration = 0.5-3:1, provides the required light conditions for microalgae growth and reproduction, and performs timed micro-aeration through the air pump of the aeration head 4. The time interval for micro-aeration is 0.5 hours of aeration every 3 hours. The umbrella-shaped multi-hole gas distribution plate 3 forms small upflowing gas bubbles in the reactor 6. Oxygen is supplied in an intermittent aeration mode. The main purpose is to promote the mixing of the micro-magnetic carrier filler inside the micro-magnetic carrier type algal biofilm reactor with the wastewater, and the biofilm and the pollutants in the water body to fully contact, adsorb and degrade them, so that the water quality is purified. The purified water finally flows out from the water outlet 5.

[0040] Example 2: Treatment of wastewater using the micro-magnetic carrier type algal biofilm reactor described above

[0041] Treatment of wastewater using the micro-magnetic carrier type algal biofilm reactor described in Example 1

[0042] (1) Prepare the nutrient solution: control the pH of the nutrient solution to be 7.5-8.5 by adding NaHCO3, and the COD:N:P in the nutrient solution is 180:30:3.5 (unit mg / L). The composition of the nutrient solution is shown in Table 1.

[0043] Table 1 Nutrient solution composition

[0044]

[0045]

[0046] (2) Wastewater treatment phase: After the biofilm formation, the HRT was kept at 24 h, and the light was set as dark = 12 h:12 h by controlling the lamp 2. The oxygen was supplied by intermittent aeration, and the dissolved oxygen (DO) was kept at 2-4 mg / L by aeration for 0.5 h every 3 h. The influent was the same as that in the biofilm formation phase.

[0047] (2) Wastewater treatment phase: After the biofilm formation, the HRT was kept at 24 h, and the light was set as dark = 12 h:12 h by controlling the lamp 2. The oxygen was supplied by intermittent aeration, and the dissolved oxygen (DO) was kept at 2-4 mg / L by aeration for 0.5 h every 3 h. The influent was the same as that in the biofilm formation phase.

[0048] (3) The carrier filler without the magnetic field (the magnetic field strength is represented as 0 mT) used as a blank control was prepared by mixing high-density polyethylene, hydrophilic auxiliary material clinoptilolite, and electrophilic auxiliary material iron oxide at a mass ratio of 100:2:1 without adding neodymium iron boron according to the preparation method of the micro-magnetic carrier filler described above.

[0049] As a comparison, four different magnetic field strengths (0 mT, 0.3 mT, 0.9 mT, and 1.5 mT) of the carrier filler were used for algal biofilm culture. The raw material ratio of the four kinds of carrier fillers was high-density polyethylene:neodymium iron boron:clinoptilolite:iron oxide at a mass ratio of 100:0:2:1, 100:2:2:1, 100:8:2:1, and 100:14:2:1, corresponding to the magnetic field strengths of 0 mT, 0.3 mT, 0.9 mT, and 1.5 mT, respectively. The influent was controlled to be consistent in each group. The results are shown in Figures 5-6 .

[0050] The algal-bacterial symbiotic community structure in the algal biofilm reactor of the micro-magnetic carrier was subjected to DNA extraction, PCR amplification, amplification product purification, high-throughput sequencing, and analysis. The results are shown in Figure 4 .

[0051] Figure 4 Figure showing the species composition changes of the algal biofilm under the action of the micro-magnetic carrier with different magnetic field strengths for the algal-bacterial symbiotic community obtained from the wall of the aerobic reaction tank of an actual wastewater treatment plant in Example 2; wherein (a) is the community graph at the phylum level, and (b) is the community graph at the genus level. The results are shown in Figure 4It can be seen that the species composition of the microbial community in the reactor at the door level is mainly Proteobacteria, Cyanobacteria, Bacteroidota and Chloroflexi, and the proportion decreases in turn. Compared with the blank group with a magnetic field strength of 0 mT, the algal biofilm on the micro-magnetic carrier with a higher magnetic field strength has a higher abundance of Cyanobacteria, which is a group of green autotrophic plants and a large single-celled prokaryote capable of oxygen-producing photosynthesis. Blue algae can convert CO2 into biomass and produce oxygen, which makes the algal biofilm have stronger carbon fixation efficiency. Under the four magnetic field strengths, the abundance of Proteobacteria in the algal biofilm in the reactor is similar, indicating that the magnetic field does not affect the denitrifying bacteria. Among them, the abundance of Planctomycetes in the reactor under the magnetic field strength of 0.9 mT is significantly improved. Planctomycetes contains some anaerobic ammonia oxidation bacteria, and all the discovered anaerobic ammonia oxidation bacteria belong to the order of Planctomycetales, such as Candidatus Brocadia, which also indicates that an anaerobic environment conducive to the survival of anaerobic ammonia oxidation bacteria may be formed in the biofilm.

[0052] During the operation of the reactor, water samples were taken every 3 days on average, filtered with 0.45 μm glass fiber filter membrane, stored in a 4°C refrigerator, and the relevant indicators were detected within 24 hours. The measured conventional water quality indicators are COD, total nitrogen, ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen, respectively using the rapid sealed catalytic digestion method, potassium persulfate oxidation-ultraviolet spectrophotometry, salicylic acid-hypochlorite spectrophotometry, ultraviolet spectrophotometry, and diazotization coupling spectrophotometry. The specific detection methods can refer to the "National Environmental Protection Bureau Water and Wastewater Detection and Analysis Methods (Fourth Edition)". The measured algal biofilm indicators include biofilm amount, chlorophyll content, protein and polysaccharide content. Among them, the biofilm amount is detected by the volatile suspended solids (VSS) method, the chlorophyll content is extracted by the acetone spectrophotometry method, the protein content is detected by the BCA method, and the polysaccharide content is detected by the sulfanilic acid method. The actual initial concentrations of COD, total nitrogen, ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen in the wastewater influent were 180 mg / L, 30 mg / L, 30 mg / L, 0 mg / L, and 0 mg / L, respectively. The results showed that the COD concentration in the effluent of each reactor was between 3.91-9.72 mg / L, and the COD removal rate reached more than 94%, and the magnetic field had no significant effect on the COD removal efficiency of the algal biofilm. From the results of the total nitrogen and ammonia nitrogen in the effluent, it can be seen that the magnetic field has no significant effect on the removal of total nitrogen and ammonia nitrogen in the algal biofilm. Figure 5It can be seen that the chlorophyll content is an important indicator to evaluate the carbon fixation efficiency of algal biofilm, and the higher the content, the more carbon dioxide can be absorbed by microalgae through photosynthesis. The results show that the algal biofilm has a strong biomass accumulation capacity. After stable cultivation of the algal biofilm, the chlorophyll content under the 0.9 mT magnetic field (0.854 mg / L) is 2.5 times that without the magnetic field (0.337 mg / L), and the algal biofilm amount (2.2 mg) is 2.2 times that without the magnetic field (1.0 mg). The algal biofilm with the micro-magnetic carrier filler has superior carbon fixation performance and better benefits.

[0053] By Figure 6 It can be seen that in terms of denitrification effect, the total nitrogen removal rate of the magnetic field group reaches 97.6%, and the effluent total nitrogen concentration is 0.76 mg / L, which is 14.3% higher than the removal rate (83.2%) without adding the magnetic field. The promotion effect of the magnetic field on the denitrification effect of the algal biofilm is very significant. The effluent ammonia nitrogen and nitrite nitrogen concentrations are reduced to about 0.02 mg / L, and the effluent nitrate nitrogen concentration of the magnetic field group is also lower than that of the non-magnetic field group. Among them, the effluent nitrate nitrogen concentration under the 0.9 mT magnetic field is 0.67 mg / L, while the effluent nitrate nitrogen of the group without adding the magnetic field is 5.30 mg / L.

[0054] From the above experimental data, the micro-magnetic carrier-based algal biofilm reactor uses micro-magnetic carrier fillings for immobilized microalgae cultivation to purify wastewater deeply. The removal rate of TN in cultivation reaches more than 96%, with good removal effect and high stability, and promotes the synthesis of algal biofilm chlorophyll and protein, i.e. more microalgae in the algal biofilm system can perform photosynthesis, making it have stronger carbon fixation efficiency. It can be concluded that the microalgae cultivation system can realize efficient carbon fixation of microalgae while deeply denitrifying wastewater. In particular, the micro-magnetic carrier fillings cultivated by 0.9mT magnetic field have outstanding advantages in denitrification and carbon fixation. Specifically, in terms of denitrification, the total nitrogen removal rate of the micro-magnetic carrier fillings with 0.9mT magnetic field reaches 97.5%, and the effluent total nitrogen concentration is only 0.76mg / L, achieving the best removal effect in the 0-1.5mT magnetic field range, with a removal rate increase of 1.2%-14.3% compared with other magnetic field conditions. The effluent ammonia nitrogen concentration is also the lowest in the 0-1.5mT magnetic field range, with a removal rate of 99.9%. The effluent nitrate nitrogen accumulates to a certain extent in the later stage of cultivation, reaching 0.67mg / L, compared with the effluent nitrate nitrogen concentration of 1.25-5.30mg / L in other reactors in the 0-1.5mT magnetic field range, and the accumulation of effluent nitrate nitrogen under the 0.9mT magnetic field condition is the least, which is more conducive to the effluent total nitrogen meeting the discharge standard. In terms of carbon fixation, the chlorophyll content under the 0.9mT magnetic field is 0.854mg / L, which is 2.5 times that without adding a magnetic field, while the chlorophyll content under other magnetic field conditions in the 0-1.5mT magnetic field range is 0.337-0.531mg / L, and the 0.9mT magnetic field is the best condition for chlorophyll accumulation, indicating that microalgae can absorb more carbon dioxide through photosynthesis. Under the 0.9mT magnetic field, the algal biofilm quantity (2.2mg) is 2.2 times that without adding a magnetic field (1.0mg), which is 37.5%-120% higher than the biofilm accumulation of other groups under the 0-1.5mT condition. The protein accumulation under the 0.9mT condition is 31.39mg / L, and the polysaccharide accumulation is 15.12mg / L, which is 83%-543% and 14.9%-43.4% higher than other magnetic field groups, respectively. The results show that the micro-magnetic carrier fillings with 0.9mT magnetic field strength have superior carbon fixation performance, which also helps to deeply denitrify wastewater, and are the best choice.

Claims

1. A micro-magnetic carrier-based bacteria-algae biofilm reactor, characterized in that, The micro-magnetic carrier type algae-bacterial biofilm reactor is provided with a water inlet (1) at the upper part, a lamp tube (2) is arranged in the middle of the top of the micro-magnetic carrier type algae-bacterial biofilm reactor and extends inward, a porous cloth gas distribution plate (3) is arranged inside the micro-magnetic carrier type algae-bacterial biofilm reactor, an aeration head (4) is connected to the bottom of the porous cloth gas distribution plate (3) through a gas pipe, a gas pump (5) is connected to the outside of the aeration head (4), a water outlet (7) is arranged at the lower part of the side wall of the micro-magnetic carrier type algae-bacterial biofilm reactor, the micro-magnetic carrier filler (6) is arranged in the micro-magnetic carrier type algae-bacterial biofilm reactor, the alga-bacterial symbiotic community is inoculated on the micro-magnetic carrier filler (6), the biofilm is formed on the inner and outer surfaces of the micro-magnetic carrier filler (6), the magnetic field strength of the micro-magnetic carrier filler (6) is 0.3-1.5 mT, the micro-magnetic carrier filler (6) is a hollow spherical structure, and the porous cloth gas distribution plate (3) is an umbrella-shaped structure.

2. The micro-magnetic carrier-based bacteria-algae biofilm reactor according to claim 1, characterized in that, The micro-magnetic carrier filler (6) is filled in the micro-magnetic carrier type algae-bacterial biofilm reactor at a filling rate of 40-80%.

3. The micro-magnetic carrier-based bacteria-algae biofilm reactor according to claim 1, characterized in that, The micro-magnetic carrier filler (6) comprises high-density polyethylene, neodymium-iron-boron, hydrophilic adjuvants and electrophilic adjuvants, and the mass ratio of the high-density polyethylene, neodymium-iron-boron, hydrophilic adjuvants and electrophilic adjuvants is 100:2-14:2:

1.

4. The micro-magnetic carrier-based bacteria-algae biofilm reactor according to claim 3, characterized in that, The hydrophilic adjuvant is clinoptilolite, and the electrophilic adjuvant is iron oxide.

5. Application of the micro-magnetic carrier type algae-bacterial biofilm reactor in treating wastewater.

6. A method for treating wastewater by using the micro-magnetic carrier type algae-bacterial biofilm reactor, comprising the following steps: (1) a biofilm formation stage: the alga-bacterial symbiotic community is added to the micro-magnetic carrier type algae-bacterial biofilm reactor, and the alga-bacterial symbiotic community is inoculated on the micro-magnetic carrier filler (6) to form a biofilm on the inner and outer surfaces of the micro-magnetic carrier filler (6); (2) a wastewater treatment stage: the wastewater enters the micro-magnetic carrier type algae-bacterial biofilm reactor through the water inlet (1), the light illumination time is set by controlling the lamp tube (2), the gas pump (5) of the aeration head (4) is used for timed micro-aeration, the umbrella-shaped porous cloth gas distribution plate (3) forms the upflowing micro-bubbles in the micro-magnetic carrier type algae-bacterial biofilm reactor, the micro-magnetic carrier filler (6) is fluidized and aerated, the biofilm on the micro-magnetic carrier filler (6) fully contacts with the pollutants in the wastewater and adsorbs and degrades the pollutants, so that the wastewater is purified, and the purified water finally flows out from the water outlet (7).

7. The method of claim 6, wherein the step of applying is performed by a user. In step (1), the biofilm formation stage is to add the alga-bacteria symbiotic community into the micro-magnetic carrier type bacteria-algae biofilm reactor. The nutrient solution enters the micro-magnetic carrier type bacteria-algae biofilm reactor through the water inlet (1), the hydraulic retention time is maintained at 12-24 h, and the continuous light illumination is more than 15 days to provide the required light conditions for the growth and reproduction of microalgae and bacteria. The micro-aeration is performed by a gas pump (5) at a time interval of 0.5 h of aeration every 3 h. The umbrella-shaped porous gas distribution plate (3) forms the upflowing micro-bubbles in the micro-magnetic carrier type bacteria-algae biofilm reactor to fluidize and aerate the micro-magnetic carrier filler (6). The microalgae and bacteria continuously adhere and grow on the inner and outer surfaces of the micro-magnetic carrier filler (6) to form a biofilm. The nutrient solution contains carbon source, nitrogen, phosphorus, calcium, magnesium macroelements, and iron, zinc, manganese, cobalt microelements.

8. The application method according to claim 7, characterized in that, In step (2), the wastewater treatment stage maintains the hydraulic retention time at 12-24 h, controls the light tube (2) to set the light illumination time: dark time = 0.5-3:1, and the time interval of the timed micro-aeration is 0.5 h of aeration every 3 h.

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