A method for treating high-ammonia nitrogen wastewater using mixed algae membrane

Abstract

The present invention belongs to the technical field of high-ammonia nitrogen wastewater treatment. The present invention discloses a strain of Synechocystis S1 that can form a mixed algae film with green algae and its application. The present invention also discloses a method for treating high-ammonia nitrogen wastewater by using Synechocystis S1 and green algae to form a mixed algae film, the method comprising adding a mixed seed liquid of Synechocystis and green algae into a rotating biofilm reactor for film culture to form a mixed algae film, and then operating the rotating biofilm reactor to treat high-ammonia nitrogen wastewater. The method of the present invention can treat high-ammonia nitrogen wastewater with a concentration of 1000 mg / L, and has a high biomass yield and a good ammonia nitrogen removal effect. Algal cells can be recovered by scraping, overcoming the shortcomings of low light utilization, difficult harvesting, and inability to continuously process and operate in traditional suspension culture methods. Ammonia nitrogen in wastewater can be continuously and efficiently bioconverted while harvesting high-value microalgae biomass.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-ammonia nitrogen wastewater treatment, and more specifically, relates to a method for treating high-ammonia nitrogen wastewater using a mixed algae membrane. Background Art

[0002] High-ammonia nitrogen wastewater refers to contaminated water bodies with ammonia nitrogen concentrations exceeding 200 mg / L. It has a wide range of sources, complex composition, and high discharge volumes. It is commonly found in industrial and aquaculture wastewater, including sources such as metal smelting, food processing, livestock and poultry farming, landfill leachate, and the semiconductor industry. Discharge into water bodies can lead to eutrophication and biotoxicity, as well as a range of serious environmental problems such as soil degradation and groundwater contamination. Current traditional treatment methods (such as physical stripping, chemical precipitation, and biological nitrification / denitrification processes) suffer from numerous shortcomings, including high treatment costs, sludge generation, complex and lengthy processes, and the potential for secondary pollution.

[0003] Microalgae are algae that are so small that their morphological structure can only be discerned under a microscope. On the one hand, microalgae have the characteristics of simple microbial structure and rapid growth and reproduction, making them easy to cultivate on a large scale. On the other hand, microalgae can use solar energy (their photosynthetic efficiency is higher than that of plants) and nitrogen and phosphorus in water as nutrients to grow autotrophically and accumulate large amounts of high-value bioactive substances such as proteins, oils, polyunsaturated fatty acids, and carotenoids in their cells. Compared with traditional methods of resource utilization of high-ammonia nitrogen wastewater, the use of microalgae to treat high-ammonia nitrogen wastewater does not produce or release toxic substances during the treatment process, and can also simultaneously obtain large amounts of microalgae biomass; this biomass can be further processed into high-value-added products such as fertilizers, biofuels, animal feed, and chemical products, realizing the resource recycling of wastewater, reducing its treatment costs, and meeting the development needs of a circular economy. Microalgae-based treatment technologies have gradually become a hot topic in wastewater treatment research.

[0004] However, although ammonia nitrogen is a form of nitrogen source that is easily utilized by most microalgae, most microalgae have low tolerance to high concentrations of ammonia nitrogen and are difficult to directly apply to the treatment of high ammonia nitrogen wastewater. The currently reported scheme for treating high ammonia nitrogen wastewater using mixed algae membrane technology can only tolerate up to 600 mg / L (CN106396112A). The current practice in practical applications is to pretreat ammonia nitrogen wastewater to reduce the ammonia nitrogen concentration, such as "A method for treating high-concentration ammonia nitrogen pig biogas" (CN104445816A), which uses zeolite to pretreat high ammonia nitrogen biogas; "A method for culturing microalgae using adsorption treatment of ammonia nitrogen wastewater" (CN109912136A), which uses adsorbents such as activated carbon and ion exchange resins to pretreat high ammonia nitrogen wastewater, etc.

[0005] Recently, Wei Dong et al. disclosed a method for directly treating high-ammonia nitrogen wastewater by fermenting and culturing Chlorella pyrenoides (CN110627213B). Although this technology can directly treat high-concentration ammonia nitrogen wastewater without pretreatment to reduce the ammonia nitrogen concentration, its fermentation process requires feeding (such as carbon source, phosphorus source), the design of the photofermentation device is complex, the treatment method is cumbersome, and it is a batch culture and cannot be processed and operated continuously. More importantly, in these microalgae treatment methods, the microalgae are all suspended in the water body. The attenuation of light will cause the algae yield to decrease, thereby reducing the wastewater treatment efficiency. In addition, when recovering algae cells, methods such as centrifugation and filtration have high energy consumption, gravity-driven sedimentation method has low efficiency, and flocculation technology has the risk of introducing metal ions such as aluminum and iron. Immobilization technologies such as embedding and covalent binding greatly increase the difficulty of treatment and operating costs. The problem of harvesting algae cells has seriously restricted the development and application of microalgae wastewater treatment methods.

[0006] Therefore, in view of the shortcomings of the existing technology of using microalgae to treat high ammonia nitrogen wastewater, it is urgent to develop a green, efficient, low-energy-cost and simple-to-operate treatment method. Summary of the Invention

[0007] In order to overcome the shortcomings of the existing use of microalgae to treat wastewater with high ammonia nitrogen tolerance and the inability to operate continuously, the present invention provides a method for treating high ammonia nitrogen wastewater using a mixed algae film, specifically a method for using a rotating biofilm reactor to cultivate a blue algae and a green algae to form a mixed algae film to bioconvert high ammonia nitrogen in water.

[0008] The first object of the present invention is to provide a strain of Synechocystis that can form a mixed algae film with green algae for treating high ammonia nitrogen wastewater.

[0009] The second object of the present invention is to provide the use of the above-mentioned Synechocystis in treating ammonia nitrogen wastewater.

[0010] The third object of the present invention is to provide the use of the above-mentioned Synechocystis in cooperating with green algae to treat ammonia nitrogen wastewater or forming algae film with green algae.

[0011] The fourth object of the present invention is to provide a method for treating high-ammonia nitrogen wastewater using mixed algae membranes.

[0012] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0013] The present invention provides a strain of Synechocystis S1 that can form a mixed algae film with green algae and is used to treat high-ammonia nitrogen wastewater. The strain has been deposited in the China Center for Type Culture Collection on October 25, 2023, and the strain collection number is CCTCC NO: M20231999.

[0014] By using the mixed algae membrane formed by Synechocystis and green algae and then using a rotating biofilm reactor, extremely high concentrations of ammonia nitrogen wastewater can be directly treated with high efficiency, low energy consumption and simple operation. Therefore, the present invention provides the following applications:

[0015] The present invention provides the use of the above-mentioned Synechocystis S1 in treating ammonia nitrogen wastewater.

[0016] The present invention also provides the use of the above-mentioned Synechocystis S1 in cooperating with green algae to treat ammonia nitrogen wastewater or forming an algae film with green algae.

[0017] The present invention provides a method for treating high-ammonia nitrogen wastewater using a mixed algae film. The method comprises adding a mixed seed liquid of the above-mentioned Synechocystis S1 and green algae into a rotating biofilm reactor for film culture to form a mixed algae film, and then operating the rotating biofilm reactor to treat the high-ammonia nitrogen wastewater.

[0018] Preferably, the density of the mixed seed liquid of Synechocystis S1 and green algae is not less than 0.5 g / L.

[0019] Preferably, the density of the mixed seed liquid of Synechocystis S1 and green algae is 0.5-100 g / L.

[0020] Preferably, the mixed seed solution is obtained by mixing and culturing the algae solution of Synechocystis S1 and the algae solution of Chlorella at a volume ratio of (1-9):(1-9).

[0021] More preferably, the mixed seed liquid is obtained by mixing and culturing the algae liquid of Synechocystis S1 and the algae liquid of Chlorella at a volume ratio of (1-3):(1-3) (more preferably, by mixing and culturing at a volume ratio of 1:1).

[0022] Preferably, the green algae is Chlorella pyrenoidosa.

[0023] Specifically, the ammonia nitrogen wastewater is high-concentration ammonia nitrogen wastewater with an ammonia nitrogen concentration exceeding 200 mg / L, such as high-concentration ammonia nitrogen wastewater with an ammonia nitrogen concentration of 200 to 1000 mg / L.

[0024] Preferably, the hydraulic retention time of the wastewater treatment is 1 to 5 days. More preferably, the hydraulic retention time of the wastewater treatment is 1 to 3 days.

[0025] Preferably, before the mixed seed liquid is added to the rotating biofilm reactor, the rotating biofilm reactor needs to be run in water for 12 to 48 hours.

[0026] More preferably, before the mixed seed liquid is added to the rotating biofilm reactor, the rotating biofilm reactor needs to run in water for 24 hours.

[0027] Preferably, the culture conditions of the mixed seed solution are 20-30° C., 100-200 rpm rotation speed and 2500-2700 lux light intensity.

[0028] More preferably, the culture conditions of the mixed seed solution are culturing at 25° C., 150 rpm and 2600 lux light intensity.

[0029] Preferably, the film-covered culture conditions are culturing at 20-30° C., 100-200 rpm, and 2500-2700 lux for 5-10 days.

[0030] As an optional embodiment, the method for treating high-ammonia nitrogen wastewater using a mixed algae membrane of Synechocystis S1 and Chlorella pyrenoidosa comprises the following steps:

[0031] S1. Preparation of mixed seed solution:

[0032] S11. The slant-preserved Synechocystis S1 and Chlorella pyrenoidosa were inoculated into BG11 medium for activation and cultured at 20-30°C, 100-200 rpm, and 2500-2700 lux to obtain two algae solutions: Synechocystis S1 and Chlorella pyrenoidosa.

[0033] S12. The algae solution of Synechocystis S1 and the algae solution of Chlorella pyrenoidosa were mixed in a ratio of (1 to 9): (1 to 9) and then cultured. The resulting mixed algae solution was the mixed seed solution.

[0034] S2. Film coating: The mixed seed solution of step S1 is added to a rotary biofilm reactor for film culture for 5 to 10 days to form a mixed algae film. After the algae film is formed, the excess microalgae on the film are scraped off;

[0035] S3. Wastewater treatment: The ammonia nitrogen wastewater is used as the reactor inlet water and passed into the rotating biofilm reactor for treatment. Different hydraulic retention times are set to continuously treat the ammonia nitrogen wastewater mixed with algae film. The microalgae on the membrane are scraped and collected after 5 to 10 days.

[0036] Preferably, the step S11 is to culture the algae until the density of the algae liquid is not less than 0.5 g / L.

[0037] In practice, when the amount used is large, a multi-stage expansion culture method can be used to prepare a large amount of algae liquid.

[0038] Preferably, the culture conditions in step S12 are 20-30° C., 100-200 rpm, and 2500-2700 lux light intensity until the algae liquid density is not less than 0.5 g / L.

[0039] Preferably, the rotating biofilm reactor frame described in step S2 is made of aluminum alloy.

[0040] Preferably, the rotating biofilm reactor in step S2 is a semi-submerged rotating biofilm reactor.

[0041] Preferably, the rotation speed of the rotating biofilm reactor in step S2 is 2 to 6 cm / s.

[0042] Preferably, before adding the mixed seed liquid to the rotating biofilm reactor in step S2, pure water needs to be added to the water tank of the rotating biofilm reactor, and the membrane needs to run in the pure water for 24 hours to form a humid environment. After that, the pure water in the water tank is drained and the mixed seed liquid is added.

[0043] Preferably, step S3 sets the hydraulic body retention time to 1 to 5 days.

[0044] More preferably, step S3 sets the hydraulic body retention time to 3 days.

[0045] The present invention has the following beneficial effects:

[0046] The present invention utilizes a rotating biofilm reactor to cultivate a blue algae and a green algae to form a mixed algae film to continuously treat high-ammonia nitrogen wastewater. The mixed algae film can directly treat high-ammonia nitrogen wastewater without pretreatment, and no feeding is required during the treatment process, allowing for continuous wastewater treatment. The mixed algae film formed by the film growth of this technology has strong tolerance to high ammonia nitrogen and can tolerate an ammonia nitrogen concentration of 1000 mg / L. It has high biomass yield and good ammonia nitrogen removal effect. The algae cells can be recovered by scraping without feeding (i.e., no additional carbon source, phosphorus source, etc.) and can be continuously operated and treated. This overcomes the shortcomings of traditional suspension culture methods such as low light utilization, difficulty in harvesting, and inability to continuously process and operate. It can continuously and efficiently bioconvert ammonia nitrogen in wastewater while harvesting high-value microalgae biomass. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 100mg / L(a), 250mg / L(b), 500mg / L(c) and 1000mg / L(d)NH4 + Growth status of mixed algae films under different -N concentrations.

[0048] Figure 2 For different NH4 + -N concentration (RAB-1 represents RAB with HRT set to 1 day; RAB-3 represents RAB with HRT set to 3 days; BC-3 represents BC with HRT set to 3 days).

[0049] Figure 3NH4 in the reactor inlet and outlet during the treatment of 250mg / L (a), 500mg / L (b) and 1000mg / L (c) ammonia nitrogen wastewater + -N concentration determination results.

[0050] Figure 4 The results of ammonia nitrogen removal rates when different algae films were used to treat wastewater with high ammonia nitrogen concentrations. DETAILED DESCRIPTION

[0051] The present invention will be further described below with reference to the accompanying drawings and specific examples, but the examples do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0052] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0053] In the following examples, Chlorella pyrenoidosa was purchased from the Freshwater Algae Culture Collection at the Institute of Hydrobiology, Chinese Academy of Sciences (FACHB), with the number FACHB-27. Oscillatoria lutea var. contorta was purchased from the Freshwater Algae Culture Collection at the Institute of Hydrobiology, Chinese Academy of Sciences, with the number FACHB-278.

[0054] The formula of BG11 culture medium is NaNO3 1500mg / L, MgSO4·7H2O 75mg / L, K2HPO4·3H2O52mg / L, CaCl2·2H2O 36mg / L, Na2CO3 20mg / L, Ctric acid·H2O 6.6mg / L, Ferric ammonium citrate 6mg / L, EDTANa2·2H2O 1.1mg / L, A5 (Trace metal solution) 1mL / L; the formula of A5 (Trace metal solution) is H3BO3 2.86g / L, MnCl4·4H2O 1.86g / L, Na2MoO4·2H2O 0.39g / L, ZnSO4·7H2O 0.22g / L, CuSO4·5H2O 0.08g / L, Co(NOз)2·6H2O 0.05g / L.

[0055] In the following examples, the biomass yield was determined using the dry weight method. The specific procedure was as follows: the harvested microalgae biomass was washed three times with pure water and then filtered using a filter membrane (the filter membrane had been dried in a 105°C oven to constant weight and the weight recorded). After filtration, the filter membrane with the algal cell precipitate was dried again at 105°C for more than 6 hours until the filter membrane weight no longer changed. The filter membrane was then cooled to room temperature in a desiccator and weighed again. The difference in weight before and after filtration was the weight of the harvested microalgae biomass. Converting to a working volume of 1.2 L yielded the total biomass, which was then divided by the corresponding working cycle to obtain the biomass yield.

[0056] The rotating biofilm reactor used in the examples is specifically the rotating algae biofilm photobioreactor described in the inventor's previously applied US Patent No. 11691902B2. The rotating biofilm reactor includes components such as a frame, a motor, a rotating drum, a membrane, and a water tank (1.2 L).

[0057] Example 1 Isolation and identification of Synechocystis S1

[0058] 1. Strain Isolation

[0059] Surface water samples were collected from shrimp ponds on Haiou Island in Panyu District, Guangzhou. Algal cells were collected by filtering 200 mL of the sample through a GF / C filter (1.2 μm). The filtered membrane was placed in a sampling tube containing an appropriate amount of sterile BG11 culture medium and transported to the laboratory at low temperature to maintain viability. The algal cells on the membrane in the sampling tube were washed and transferred to BG11 culture medium for culture. When the algal solution turned blue-green, a small amount of the solution was diluted and serially diluted. A 10 μL sample was squeezed onto a coverslip for microscopic observation (the dilution factor was determined so that only one cell was visible in each field of view). Based on the dilution concentration, 100 μL of the diluted sample was spread onto BG11 solid culture medium. Three plates were plated for each sample, sealed with parafilm, and placed inverted under 1000-3000 lux light for observation. Once colonies emerged, single colonies were streaked. After two to three rounds of purification, a pure strain of microalgae was obtained, designated strain S1.

[0060] 2. Identification of strain S1

[0061] Morphological identification: The single colony of strain S1 grown on BG11 solid medium was nearly round and blue-green in color.

[0062] Molecular biological identification: strain S1 was identified as belonging to the genus Synechocystis by molecular biological 16S rDNA sequencing and comparison.

[0063] In summary, strain S1 was identified as Synechocystis sp. and was deposited in the China Center for Type Culture Collection on October 25, 2023, with the strain accession number CCTCC NO: M 20231999.

[0064] Example 2 Preparation of mixed microalgae seed solution

[0065] The preparation method of microalgae mixed seed liquid is as follows:

[0066] S11. Inoculate the slant-preserved Synechocystis and Chlorella pyrenoidosa into BG11 medium for activation. Cultivate at 25°C, 150 rpm, and 2600 lux for approximately 10 days. Expand the culture when the algal solution shows a noticeable color change and the algal cell density is high (algal solution density is not less than 0.5 g / L).

[0067] S12. First expansion culture: Take 10 mL of Synechocystis algae liquid and 10 mL of Chlorella pyrenoidosa algae liquid, respectively, and inoculate them into 90 mL of BG11 medium in Erlenmeyer flasks. Cultivate at 25°C, 150 rpm, and 2600 lux light intensity for 2 weeks.

[0068] S13. Second Expansion Culture: Perform a second expansion culture of each algae species using a bubble column reactor. Add 400 mL of algae solution and 800 mL of BG11 medium to each reactor. Connect an air pump to introduce air (to prevent the algae from sinking to the bottom, at an air rate of 1 mL / s). Cultivate at 25°C, 150 rpm, and 2600 lux light intensity until the algae solution density is no less than 0.5 g / L, thereby obtaining a high-density algae solution.

[0069] S14. Add 15 L of Synechocystis algae solution and 15 L of Chlorella pyrenoidosa algae solution to a flat-plate reactor, add 130 L of BG11 culture medium, and continue culturing at 25°C, 150 rpm, and 2600 lux light intensity for about one week, until the algae solution density reaches above 0.5 g / L. The resulting mixed algae solution is the mixed seed solution.

[0070] Example 3 Preparation of microalgae mixed seed solution

[0071] The microalgae seed liquid preparation method involves inoculating slant-preserved Synechocystis and Chlorella pyrenoidosa into BG11 medium for activation. The cells are then cultured at 20°C, 200 rpm, and 2700 lux for approximately 10 days. The cells are then expanded when the color of the algae solution changes significantly and the cell density reaches a high level. 10 mL of the algae solution is then inoculated into 90 mL of BG11 medium in a conical flask and cultured at 25°C, 150 rpm, and 2600 lux for two weeks. A second expansion culture of each algae type is then performed using a bubble column reactor. 400 mL of the algae solution and 800 mL of BG11 medium are added to each reactor. Air is then pumped in at a rate of 1 mL / s to prevent the algae from sinking to the bottom. The cells are then cultured at 25°C, 150 rpm, and 2600 lux until the algae solution density reaches 0.5 g / L or higher, thus obtaining a high-density algae solution. Add 3 L of Synechocystis liquid and 27 L of Chlorella pyrenoidosa liquid into a flat-plate reactor, add 130 L of BG11 culture medium, and continue culturing at 25°C, 150 rpm, and 2600 lux light intensity for about one week until the algae liquid density reaches above 0.5 g / L. The resulting mixed algae liquid is the mixed seed liquid.

[0072] Example 4 Preparation of mixed microalgae seed solution

[0073] The microalgae seed liquid preparation method involves inoculating slant-preserved Synechocystis and Chlorella pyrenoidosa into BG11 medium for activation. The cells are then cultured at 30°C, 100 rpm, and 2500 lux for approximately 10 days. The cells are then expanded when the color of the algae solution changes significantly and the cell density reaches a high level. 10 mL of the algae solution is then inoculated into 90 mL of BG11 medium in a conical flask and cultured at 25°C, 150 rpm, and 2600 lux for two weeks. A second expansion culture of each algae type is then performed using a bubble column reactor. 400 mL of the algae solution and 800 mL of BG11 medium are added to each reactor. Air is then pumped in at a rate of 1 mL / s to prevent the algae from sinking to the bottom. The cells are then cultured at 25°C, 150 rpm, and 2600 lux until the algae solution density reaches 0.5 g / L or higher, yielding a high-density algae solution. Add 27 L of Synechocystis liquid and 3 L of Chlorella pyrenoidosa liquid into a flat-plate reactor, add 130 L of BG11 culture medium, and continue culturing at 25°C, 150 rpm, and 2600 lux light intensity for about one week until the algae liquid density reaches above 0.5 g / L. The resulting mixed algae liquid is the mixed seed liquid.

[0074] Example 5

[0075] (1) Test method

[0076] Pure water was added to the water tank of a revolving algal biofilm photobioreactor (RAB). After the membrane was run in the pure water for 24 hours to form a humid environment, the pure water in the water tank was drained, and the mixed seed liquid in Example 2 was added and continued to operate to grow microalgae film. The amount of mixed seed liquid added was such that the membrane of the RAB was submerged. After the microalgae film grew for 10 days, the excess microalgae on the film were scraped and collected to obtain a mixed algae film of Synechocystis and Chlorella pyrenoidosa formed on the RAB.

[0077] High-ammonia nitrogen wastewater with varying concentrations served as reactor influent and was passed through a revolving algal biofilm photobioreactor (RAB) and a bubble column suspension culture reactor (BC). The hydraulic retention time (HRT) of the RAB was set at 1 and 3 days, while the HRT of the BC was set at 3 days. The RAB rotated at a speed of 4 cm / s, and microalgae from the RAB and BC were collected every 10 days for biomass yield measurement.

[0078] The high-ammonia nitrogen wastewater used as reactor influent was prepared by adding the ammonium salt NH4Cl to the nitrogen-free BG11 medium (nitrogen source removed, i.e., NaNO3 is not added to the BG11 medium formula). The final ammonia nitrogen concentration in the nitrogen-free BG11 medium was adjusted by adjusting the amount of NH4Cl added. Four final ammonia nitrogen concentrations were set for the high-ammonia nitrogen wastewater: 100 mg / L, 250 mg / L, 500 mg / L, and 1000 mg / L.

[0079] (2) Test results

[0080] Different NH4 + The growth status of the mixed algae film of Synechocystis and Chlorella pyrenoidosa under -N concentration is as follows Figure 1 As shown, from Figure 1 It can be seen that the mixed algae films cultured in wastewater with different concentrations of ammonia nitrogen grew well, and their growth was not significantly inhibited even when the ammonia nitrogen concentration reached 1000 mg / L.

[0081] The microalgae biomass yields of different treatment groups were as follows Figure 2 As shown, from Figure 2It can be seen that the mixed algae films cultured in ammonia nitrogen wastewater in RAB all grew well, and their growth was not significantly inhibited even when the ammonia nitrogen concentration reached 1000 mg / L. This shows that when Synechocystis and Chlorella pyrenoidosa are grown on RAB films, they can not only effectively control microbial contamination within the system, which is beneficial to the stability of the biofilm system, but also enhance tolerance to high ammonia nitrogen. In addition, the biomass yield of the microalgae culture system with a hydraulic retention time of 3 days was significantly higher than that of the treatment with a hydraulic retention time of 1 day. In contrast, the microalgae cultured in suspension in BC were completely dead when the ammonia nitrogen concentration reached 500 mg / L due to the influence of drainage loss and high ammonia nitrogen.

[0082] Example 6

[0083] (1) Test method

[0084] Mixed algal biofilms of Synechocystis and Chlorella pyrenoidosa formed on RABs were obtained using the experimental method described in Example 5. High-ammonia nitrogen wastewater with varying concentrations was used as reactor influent and passed through the RABs for continuous influent and effluent treatment. The RABs were set to hydraulic retention times of 1 and 3 days, respectively. The ammonia nitrogen concentration in the reactor effluent of each treatment group was measured daily, and the reactors operated continuously for 30 days.

[0085] The high-ammonia nitrogen wastewater used as reactor influent was prepared by adding the ammonium salt NH4Cl to the nitrogen-free BG11 medium (nitrogen source removed, i.e., NaNO3 is not added to the BG11 medium formula). The final ammonia nitrogen concentration in the nitrogen-free BG11 medium was adjusted by adjusting the amount of NH4Cl added. Three final ammonia nitrogen concentrations were set for the high-ammonia nitrogen wastewater: 250 mg / L, 500 mg / L, and 1000 mg / L.

[0086] The results of ammonia nitrogen concentration determination in the effluent of each treatment group are as follows Figure 3 As shown, from Figure 3 It can be seen that when the hydraulic retention time is 3 days, the mixed algae film of Synechocystis and Chlorella can completely remove 250mg / L and 500mg / L ammonia nitrogen, and the removal rate of 1000mg / L ammonia nitrogen is 84%; when the hydraulic retention time is 1 day, the removal rates of the mixed algae film for 250mg / L, 500mg / L and 1000mg / L ammonia nitrogen are 96%, 94% and 80% respectively, and the removal rates are as high as 781mg / L-day and 5208mg / m 2 -day.

[0087] Compared with the traditional use of single microalgae to treat wastewater, the use of the mixed algae film formed by Synechocystis and Chlorella pyrenoidosa in the present invention to treat high-ammonia nitrogen wastewater has obvious advantages.

[0088] Example 7 Comparison of three algae film treatment technologies

[0089] (1) Preparation methods of different algal membranes

[0090] 1. Preparation method of single-species Chlorella pyrenoidosa algae membrane

[0091] The method for preparing a single-species seed solution of Chlorella pyrenoidosa was similar to that in Example 2, except that Chlorella pyrenoidosa was cultured alone, rather than Synechocystis. After the secondary expansion culture, 30 L of the Chlorella pyrenoidosa solution was added to a flat-plate reactor, followed by 130 L of BG11 culture medium to obtain a single-species seed solution of Chlorella pyrenoidosa. All other preparation parameters and conditions were similar to those in Example 2.

[0092] A single species of Chlorella pyrenoidosa algae membrane was prepared by referring to the method of Example 5. The difference from Example 5 is that the single species of Chlorella pyrenoidosa seed liquid prepared in this example was added after the pure water in the water tank was drained.

[0093] 2. Preparation method of mixed algae membrane of Chlorella pyrenoidosa and Oscillatoria

[0094] The preparation method of the mixed seed solution of Chlorella pyrenoidosa and Oscillatoria is referred to Example 2, except that Synechocystis is replaced by Oscillatoria lutea var. contorta, and the other preparation parameters and conditions are referred to Example 2.

[0095] A mixed algae membrane of Chlorella pyrenoidosa and Oscillatoria was prepared according to the method of Example 5. The difference from Example 5 is that the mixed seed liquid of Chlorella pyrenoidosa and Oscillatoria prepared in this example was added after the pure water in the water tank was drained.

[0096] 3. The preparation method of the mixed algae membrane of Chlorella pyrenoidosa and Synechocystis is the same as that in Example 5.

[0097] (2) Test methods

[0098] Three types of algae films were used, namely, single-species Chlorella pyrenoidosa algae film (Cp), mixed algae film of Chlorella pyrenoidosa and Oscillatoria (Cp+Oc), and mixed algae film of Chlorella pyrenoidosa and Synechocystis (Cp+Ss). High-ammonia nitrogen wastewater with different concentrations was used as reactor influent and passed into RAB for continuous influent and effluent treatment of high-ammonia nitrogen wastewater. The hydraulic retention time was set to 3 days, and the average ammonia nitrogen removal rate of each treatment group was measured during the stable period. The reactor was operated continuously for 30 days.

[0099] The high-ammonia nitrogen wastewater used as reactor influent was prepared by adding the ammonium salt NH4Cl to the nitrogen-free BG11 medium (nitrogen source removed, i.e., NaNO3 is not added to the BG11 medium formula). The final ammonia nitrogen concentration in the nitrogen-free BG11 medium was adjusted by adjusting the amount of NH4Cl added. Three final ammonia nitrogen concentrations were set for the high-ammonia nitrogen wastewater: 250 mg / L, 500 mg / L, and 1000 mg / L.

[0100] (3) Test results

[0101] The ammonia nitrogen removal rates of different algae membranes when treating wastewater with different concentrations of high ammonia nitrogen are shown in the following table. Figure 4 As shown, from Figure 4 As can be seen, the removal efficiencies of single-species Chlorella pyrenoidosa films and mixed films of Chlorella pyrenoidosa and Oscillatoria at 250, 500, and 1000 mg / L ammonia nitrogen were significantly lower than those of mixed films of Chlorella pyrenoidosa and Synechocystis. Although Oscillatoria and Synechocystis belong to the phylum Cyanobacteria, their combined film-forming properties with Chlorella pyrenoidosa are poor, with almost no film formation occurring. Compared to single-species Chlorella pyrenoidosa films and composite films with other cyanobacteria, mixed films of Chlorella pyrenoidosa and Synechocystis exhibit significant advantages in treating high-ammonia nitrogen wastewater.

[0102] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for treating ammonia nitrogen wastewater using a mixed algae membrane, characterized in that: The mixed seed liquid of Synechocystis sp. S1 and green algae is added to a rotating biofilm reactor for film culture to form a mixed algae film, and then the rotating biofilm reactor is operated to treat ammonia nitrogen wastewater, and the hydraulic retention time of the wastewater treatment is 1 to 3 days; the Synechocystis sp. S1 has been preserved in the China Center for Type Culture Collection on October 25, 2023, and the strain preservation number is CCTCC NO: M 20231999; the green algae is Chlorella vulgaris; the ammonia nitrogen wastewater is high-concentration ammonia nitrogen wastewater with an ammonia nitrogen concentration exceeding 500 mg / L.

2. The method according to claim 1, wherein The density of the mixed seed solution of Synechocystis S1 and green algae is not less than 0.5 g / L.

3. The method according to claim 1 or 2, characterized in that The mixed seed solution was obtained by mixing the algae solution of Synechocystis S1 and the algae solution of Chlorella at a volume ratio of (1~9):(1~9).

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