Method and device for realizing granulation of bacteria and algae and synergistic denitrification of high-salinity wastewater

Abstract

The application relates to the technical field of wastewater treatment, and discloses a high-salinity wastewater treatment method and device for realizing granulation of bacteria-algae and synergistic denitrification, the method comprising the following steps: placing microalgae and aerobic granular sludge in a photobioreactor for initial culture; after the initial culture, adding magnetic iron oxide nanoparticles into the photobioreactor for reinforced culture to obtain bacteria-algae symbiotic aerobic granular sludge; and using the bacteria-algae symbiotic aerobic granular sludge for denitrification treatment of wastewater. By adding magnetic iron oxide nanoparticles in the growth process of bacteria-algae, the application can effectively solve the problems of slow aggregation and nucleation of bacteria-algae in the ABGS formation process, low activity of algal cell photosynthetic electron transport and decreased denitrification efficiency under high-salinity stress, and can simultaneously reinforce the rapid aggregation and nucleation of bacteria-algae, improve the photosynthetic system electron transport efficiency of algal cells under high-salinity stress, and improve the denitrification efficiency of microorganisms.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a method and device for treating high-salt wastewater by achieving bacterial and algal granulation and coordinated denitrification. Background Art

[0002] With the continuous acceleration of the industrialization process, the discharge of industrial wastewater continues to grow. Among them, high-salt wastewater accounts for a significant proportion of industrial wastewater. High-salt wastewater comes from a wide range of sources, mainly involving chemical, pharmaceutical, printing and dyeing industries. Its salt content is usually as high as 3% to 10%, and it contains a large amount of nitrogen pollutants. For example, the salinity of landfill leachate exceeds 1% (in terms of NaCl), NH4 + -N concentration ranges from 50 to 5500 mg / L. If this type of high-salt wastewater is discharged directly without proper treatment, it will cause serious pollution to the soil and water bodies.

[0003] Bacteria-algae symbiotic aerobic granular sludge is an emerging wastewater treatment technology that combines the denitrification ability of algae with the efficient pollutant removal efficiency of aerobic granular sludge (AGS), which can improve denitrification efficiency and enhance the system's resistance to shock loads and ion tolerance.

[0004] However, in a high-salt environment, although algal cells have good salt tolerance, the electron transfer efficiency and photosynthesis of their photosynthetic system will decrease, resulting in poor denitrification effect.

[0005] Therefore, how to improve the denitrification effect under high salt stress is a technical problem that needs to be solved urgently. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a method and device for treating high-salinity wastewater by achieving bacterial and algal granulation and synergistic denitrification. The method for treating high-salinity wastewater by achieving bacterial and algal granulation and synergistic denitrification comprises the following steps:

[0007] S1: Place microalgae and aerobic granular sludge in a photobioreactor for initial cultivation;

[0008] S2: After the initial culture, magnetic iron oxide nanoparticles are added to the photobioreactor for enhanced culture to obtain bacteria-algae symbiotic aerobic granular sludge;

[0009] S3: Denitrification treatment of wastewater is performed using the bacteria-algae symbiotic aerobic granular sludge.

[0010] Furthermore, the microalgae is Chlorella.

[0011] Furthermore, the magnetic iron oxide nanoparticles are Fe3O4.

[0012] Furthermore, the added amount of the magnetic iron oxide nanoparticles is 50-300 mg / L.

[0013] Furthermore, in step S1, the mass ratio of the Chlorella to the aerobic granular sludge is 1:(1-10).

[0014] Furthermore, the initial culture time is 6-8 days.

[0015] Furthermore, in the initial culture stage and the intensive culture stage, the time ratio of the light stage to the dark stage every day is 12h:12h.

[0016] Furthermore, the illumination intensity during the illumination stage is 5000 lux.

[0017] Another object of the present invention is to provide a high-salt wastewater treatment device that realizes bacterial and algae granulation and synergistic denitrification, and to treat wastewater using the high-salt wastewater treatment method that realizes bacterial and algae granulation and synergistic denitrification as described above.

[0018] Furthermore, it comprises a water inlet unit, a photobioreactor and a water outlet unit connected in sequence; an aeration unit and a stirring unit are arranged in the photobioreactor; and a light strip is wrapped around the outside of the photobioreactor.

[0019] The embodiments of the present invention have the following technical effects:

[0020] The high-salt wastewater treatment method provided in the present application, which achieves bacterial-algal granulation and synergistic denitrification, can effectively solve the problems of slow bacterial-algal aggregation and nucleation during ABGS formation, low activity of algal cell photosynthetic electron transfer bodies under high salt stress, and decreased denitrification efficiency by adding magnetic iron oxide nanoparticles during the growth of bacteria and algae. It can simultaneously enhance the rapid aggregation and nucleation of bacteria-algal cells, improve the electron transfer efficiency of the algal cell photosynthetic system under high salt stress, and improve the denitrification efficiency of microorganisms. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a schematic diagram of the ABGS denitrification pathway model under the enhanced effect of magnetic iron oxide nanoparticles of the present invention;

[0023] Figure 2 It is a schematic diagram of the assembly of the high-salt wastewater treatment device for realizing bacterial and algal granulation and coordinated denitrification according to the present invention.

[0024] In the figure: 1-water inlet tank; 2-water inlet pump; 3-water inlet valve; 4-aeration head; 5-mixing blade; 6-electric stirrer; 7-permanent magnet; 8-sampling valve; 9-sampling port; 10-water outlet valve; 11-water outlet pump; 12-water storage tank; 13-sludge outlet; 14-air flow meter; 15-blower; 16-timer; 17-photobioreactor; 18-light strip. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are considered to be within the scope of the present invention.

[0026] Currently, bacterial-algal symbiotic aerobic granular sludge is widely used in saline wastewater denitrification due to its high nitrogen removal efficiency, strong resistance to shock loads, and ion tolerance. At low salinity (≤1%), the bacterial-algal granular sludge (ABGS) system can achieve a 90% ammonia nitrogen removal rate. However, when salinity exceeds 2%, the activity of the electron transport carrier proteins in the algal photosynthetic system II is inhibited, hindering electron transport involved in photosynthesis and disrupting the balance between algal photosynthesis and respiration. The ammonia nitrogen removal rate drops to 54%, and continues to decline with increasing salinity. Furthermore, due to the inherent characteristics of microalgae cells, which are prone to cell loss, coupled with the strong electrostatic repulsion between bacteria and microalgae, bacterial-algal cell nucleation is difficult to achieve.

[0027] In order to solve the problem of poor denitrification effect in a high-salinity environment, the present application provides a high-salinity wastewater treatment method that realizes bacterial and algal granulation and synergistic denitrification, which comprises the following steps:

[0028] S1: Place microalgae and aerobic granular sludge in a photobioreactor for initial cultivation;

[0029] Preferably, the microalgae and aerobic granular sludge in this step are both pre-cultured; specifically, preferably, in the pre-culture stage, the flocculent aerobic activated sludge from the sewage treatment plant is acclimated for 10 days and the sludge is regularly discharged to improve the microbial activity and enhance the settling performance of the sludge;

[0030] The microalgae and BG11 medium were mixed in a certain ratio and cultured continuously for several days until the color turned dark green, and the concentration was measured; in this application, the microalgae and BG11 medium were preferably mixed in a mass ratio of 1:1 and cultured continuously for 30 days;

[0031] In this initial cultivation stage, in order to reduce the loss of algae in the reactor, it is preferred to use a light intensity of about 5000 lux to continuously illuminate the mixed liquid for 24 hours. No aeration conditions are set during the pre-cultivation stage. Under these conditions, microalgae convert carbon dioxide (CO2) and water (H2O) into organic matter through photosynthesis and release oxygen (O2). The heterotrophic bacteria in the granular sludge use the oxygen produced by the microalgae to degrade the organic matter in the sewage into CO2, inorganic nitrogen (such as 、 etc.) and phosphates ( ) and other simple substances. These substances further serve as nutrients and carbon sources required for microalgae photosynthesis, and are used to synthesize important intracellular substances such as proteins and nucleic acids. In the early stage of culture, it is preferred to replace 200mL of nutrient solution every 5 days and let it stand for 1 hour each time to maintain nutrient balance and prevent the activity of the bacterial community from decreasing due to insufficient substrate. Algae attach to the surface or inside of the sludge flocs and form "algae-bacteria aggregates" together with bacteria. The aggregates achieve adhesion through extracellular polymers (EPS), thereby significantly improving the sedimentation performance of the system. When the bacteria-algae symbiotic system shows good sedimentation performance, the supernatant is replaced every 2 days, and the sedimentation time is set to 30 minutes each time. After 7 days of culture, the sludge flocs are green and the supernatant is clear and transparent, indicating that a stable bacteria-algae symbiotic system has been initially established.

[0032] S2: After the initial culture, magnetic iron oxide nanoparticles are added to the photobioreactor for enhanced culture to obtain bacterial-algal symbiotic aerobic granular sludge;

[0033] During the treatment of high-salt wastewater, under high-salt stress, the efficiency of electron transfer in the photosynthetic system is reduced. In addition, microalgae cells are small, with a density close to that of water and strong electrostatic repulsion, making it difficult for them to aggregate and nucleate with bacteria. Based on this, the present application introduces magnetic iron oxide nanoparticles. Due to their unique electronic structure and iron elements, magnetic iron oxide nanoparticles can promote the secretion of extracellular polymers (EPS), thereby effectively reducing the electrostatic repulsion between microorganisms, promoting the enrichment and cultivation of microalgae, and microbial aggregation. At the same time, the iron dissolved from magnetic iron oxide nanoparticles can combine with intracellular proteins to form cytochrome C (photosynthetic electron carrier), ferrooxidoreductin (an important substance in the photosynthetic electron transport chain, providing electrons to NADP + ) and other important photosynthetic electron transporters or catalysts, and then participate in the photosynthesis of algae cells. Iron also participates in the respiration of algae cells. For example, important respiratory enzymes such as peroxidase and peroxidase contain iron; and iron can be reduced to Fe 2+ and oxidized Fe 3+The redox cycle process between them directly participates in the electron transfer in the microbial denitrification process, thereby promoting the conversion or removal of nitrogen, and then the introduction of magnetic iron oxide nanoparticles can enhance the granulation of bacteria and algae and synergistically remove nitrogen.

[0034] The magnetic iron oxide nanoparticles introduced in this application have good electrical neutralization properties, promote microbial granulation and metabolic induction, and can effectively improve the aggregation and signal exchange efficiency between bacteria and algae, thereby realizing rapid flocculation and nucleation of bacteria and algae cells; utilize the good compatibility, nanosize and magnetic effect of magnetic iron oxide nanoparticles to effectively promote the secretion of important photosynthetic electron transfer bodies such as cytochrome C and catalysts, thereby simultaneously enhancing the activity of algae photosynthetic electron transfer bodies, improving the electron transfer efficiency of the photosynthetic system, and improving the denitrification efficiency of microorganisms; the magnetic iron oxide nanoparticles introduced in this application can stimulate bacteria and algae to release a large amount of extracellular polymers (EPS) to accelerate aggregation, and metal ions form ion bridges with EPS, thereby improving the adhesion of bacteria and algae and enhancing the dense structure of particles.

[0035] The high-salt wastewater treatment method provided in the present application, which realizes bacterial and algal granulation and synergistic denitrification, can form a stable bacterial and algal symbiotic aerobic system through 40 to 60 days of cultivation.

[0036] In this step, the magnetic iron oxide nanoparticles cause bacteria and algae to aggregate, increasing EPS secretion. The pH in the reactor is preferably maintained in the neutral range (7.0-7.8) to ensure good denitrification activity of the microorganisms.

[0037] S3: Denitrification of wastewater using bacterial-algal symbiotic aerobic granular sludge.

[0038] See also Figure 1 As shown in the figure, the nitrogen removal pathway of ABGS in this step is as follows: the algae's phototaxis and photosynthetic oxygen production properties enable the particles to form aerobic, anoxic, and anaerobic zones from the outside to the inside. The establishment of a dissolved oxygen gradient can achieve nitrogen metabolic cooperation between autotrophic and heterotrophic microorganisms; at the same time, magnetic iron oxide nanoparticles stimulate the activity of algae's photosynthetic electron transporters, improving the assimilation and absorption of nitrogen-containing substances such as ammonia nitrogen and nitrate nitrogen by microalgae under high salt stress. In addition, the electron transfer efficiency of iron further improves the nitrogen removal effect.

[0039] The high-salt wastewater treatment method provided in the present application, which achieves bacterial-algal granulation and synergistic denitrification, can effectively solve the problems of slow bacterial-algal aggregation and nucleation during ABGS formation, low activity of algal cell photosynthetic electron transfer bodies under high salt stress, and decreased denitrification efficiency by adding magnetic iron oxide nanoparticles during the growth of bacteria and algae. It can simultaneously enhance the rapid aggregation and nucleation of bacteria-algal cells, improve the electron transfer efficiency of the algal cell photosynthetic system under high salt stress, and improve the denitrification efficiency of microorganisms.

[0040] The microalgae in the present application are preferably freshwater microalgae, and further preferably the microalgae are Chlorella, which utilizes the characteristics of Chlorella such as strong oxygen production capacity, fast growth rate, and strong environmental adaptability to ensure the wastewater treatment effect.

[0041] In order to ensure the synergistic nitrogen removal effect, the present application prefers that the magnetic iron oxide nanoparticles are Fe3O4; and further prefers that the addition amount of the magnetic iron oxide nanoparticles is 50-300 mg / L.

[0042] In order to take into account both denitrification effect and economy, the present application preferably adopts a mass ratio of Chlorella to aerobic granular sludge in step S1 of 1: (1-10), and further preferably 1:1.

[0043] The preferred initial culture period for this application is 6-8 days, and more preferably 7 days. Specifically, after the cultured algal liquid and acclimated aerobic granular sludge are placed in a photobioreactor and cultured for 6-8 days, magnetic iron oxide nanoparticles are added to promote microbial granulation and metabolic induction, significantly increasing the efficiency of aggregation and signal exchange between bacteria and algae, thereby achieving rapid flocculation and nucleation of bacterial and algal cells. Simultaneously, these nanoparticles can simultaneously enhance the activity of electron transporters in algal photosynthesis, thereby improving the denitrification efficiency of the microbial system. Adding nanoparticles after the pre-culture stage effectively balances the functionality of the nanoparticles with the tolerance of the microorganisms.

[0044] Furthermore, direct addition of magnetic iron oxide nanoparticles at the beginning of the culture can inhibit Chlorella photosynthesis and bacterial metabolism. After 7 days of pre-culture, the extracellular polymeric substances (EPS, such as polysaccharides and proteins) secreted by the algal aggregates can coat the magnetic iron oxide nanoparticles, reducing their surface activity through coordination, chelation, or electrostatic adsorption, thereby minimizing damage to the microorganisms. At this point, the algal aggregates already possess a certain degree of sedimentation properties, and the addition of magnetic iron oxide nanoparticles can enhance sedimentation efficiency through magnetic response properties (e.g., magnetic flocculation). However, if magnetic iron oxide nanoparticles are added early in the culture, they may become dispersed in the system, making it difficult for them to bind to the algal aggregates, thereby reducing the rate of flocculation and nucleation.

[0045] The present application prefers the initial culture stage and the intensive culture stage, and the time ratio of the light stage to the dark stage is 12h:12h every day, and the light intensity of the light stage is 5000lux; specifically, the light-dark ratio is preferably 12h:12h, the time period between 7-19 o'clock is the light stage, with natural light and light strips as light sources, and the light intensity is 5000lux; the time period between 19-7 o'clock is the dark stage.

[0046] Furthermore, during the initial and enhanced cultivation stages, the bacterial-algal symbiotic aerobic granular sludge is preferably constructed as follows: at room temperature, acclimated activated sludge and algal liquid are introduced into a photobioreactor in a specific ratio. An appropriate amount of synthetic domestic wastewater may be added. During the initial cultivation phase, 200 mL of nutrient solution is replaced every five days, with each nutrient solution allowed to settle for one hour. Once the bacterial-algal system has established good settling properties, the supernatant is replaced every two days, with each settling period lasting 30 minutes. Furthermore, illumination of the photobioreactor is provided by a light strip, with the duration of illumination controlled by a timer to maintain a light:dark ratio of 12 hours. The reactor is operated as follows: three 8-hour cycles per day, each consisting of a 30-minute water inlet, a 60-minute anoxic phase, a 300-minute aerobic phase, a 60-minute settling phase, and a 30-minute drainage phase. The settling time decreases gradually to 10 minutes with increasing particle size. The volume exchange rate is 50%.

[0047] Another object of the present application is to provide a high-salt wastewater treatment device that realizes bacterial and algae granulation and synergistic denitrification, and the device treats wastewater by the high-salt wastewater treatment method that realizes bacterial and algae granulation and synergistic denitrification as described above.

[0048] The high-salt wastewater treatment device provided in the present application realizes the granulation of bacteria and algae and synergistic denitrification. During the treatment process, by adding magnetic iron oxide nanoparticles during the growth of bacteria and algae, it can effectively solve the problems of slow aggregation and nucleation of bacteria and algae during the formation of ABGS, low activity of photosynthetic electron transfer bodies of algal cells under high salt stress, and decreased denitrification efficiency. It can simultaneously enhance the rapid aggregation and nucleation of bacteria and algae cells, improve the electron transfer efficiency of the photosynthetic system of algal cells under high salt stress, and improve the denitrification efficiency of microorganisms.

[0049] The high-salt wastewater treatment device for achieving bacterial and algal granulation and coordinated denitrification in the present application includes a water inlet unit, a photobioreactor 17 and a water outlet unit connected in sequence; an aeration unit and a stirring unit are provided in the photobioreactor 17; and a light strip 18 is wrapped around the outside of the photobioreactor.

[0050] During operation, the wastewater to be treated is input into the photobioreactor through the water inlet unit, the wastewater is denitrified in the photobioreactor, and the denitrified water is discharged through the water outlet unit.

[0051] For details, see Figure 2 As shown, the water inlet unit in the device includes a water inlet tank 1, a water inlet pump 2, and a water inlet valve 3 connected in sequence; the high-salt and high-nitrogen wastewater to be treated in the water inlet tank 1 is transferred to the photobioreactor 17 through the water inlet pump 2, and the timer 16 is controlled to regularly inlet water.

[0052] The photobioreactor 17 is a place for water treatment and is used for the growth of bacteria and algae. During operation, microalgae, aerobic granular sludge, magnetic iron oxide nanoparticles and wastewater are added to the photobioreactor 17 to react.

[0053] The aeration unit includes an aeration head 4, a blower 15, an air flow meter 14 and a timer 16; the aeration head 4 is provided in the photobioreactor 17, and preferably the aeration head 4 adopts a sand core microporous aerator; a blower 15 connected to the aeration head 4 is provided on the outside, and an air flow meter 14 is provided on the pipeline between the blower 15 and the aeration head 4 to facilitate aeration operation during operation, and preferably the aeration volume is controlled at 2cm / s by the air flow meter 14; the device also includes a timer 16 connected to the blower 15, so that the blower 15 can be started regularly by the timer 16 for aerobic aeration.

[0054] The stirring unit includes a stirring blade 5 arranged in the photobioreactor 17, and an electric stirrer 6 connected to the stirring blade 5. The electric stirrer 6 drives the stirring blade 5 to rotate to prevent the nanomaterial from agglomerating, and to evenly distribute the bacteria and algae and the nanomaterial, and controls the timer 16 to perform regular anaerobic stirring.

[0055] A sampling port 9 and a sampling valve 8 are provided on the side wall of the photobioreactor 17 to facilitate sampling and analysis.

[0056] The water outlet unit includes a water storage tank 12, a water outlet pump 11 provided on the pipeline between the water storage tank 12 and the photobioreactor 17, and a water outlet valve 10 provided on the pipeline between the water outlet pump 11 and the photobioreactor 17, so as to discharge the purified water through the water outlet unit.

[0057] The side wall of the photobioreactor 17 is also provided with a mud discharge port 13 to facilitate mud discharge operations as needed.

[0058] After a certain period of sedimentation in the photobioreactor 17 , the treated supernatant is discharged from the water outlet unit of the photobioreactor 17 , and the settled sludge is discharged from the sludge outlet 13 , and then enters the next cycle.

[0059] In the present application, a permanent magnet 7 is also provided on the side wall of the photobioreactor 17, so that the magnetic biological effect of the permanent magnet 7 and the external weak magnetic field can improve the activity of microorganisms, enhance the stability of the bacteria-algae system, and promote the aggregation of denitrification functional bacteria and the nitrogen assimilation of microalgae, thereby improving the denitrification efficiency; in order to achieve the control of light, the present application preferably adopts a transparent material for the side wall of the photobioreactor 17, and a light strip 18 is wound around the outside of the photobioreactor 17 to facilitate light control through the light strip 18; the present application preferably adopts a light strip 18 of the same model for light illumination of the photobioreactor 17, and controls the illumination duration of the reactor by the time timer 16 so that the light-dark ratio is 12h:12h.

[0060] The specific operation operations are as follows:

[0061] Light strips 18 on the outer wall of the photobioreactor 17 provide a light intensity of 5000 lux, with 12 hours of continuous light and 12 hours of continuous darkness. Acclimated aerobic granular sludge and Chlorella vulgaris are added to the photobioreactor 17. An electric stirrer 6 prevents nanomaterial aggregation and evenly distributes the bacteria, algae, and nanomaterials. Aeration heads 4 are located at the bottom of the photobioreactor 17 and are connected to an air flow meter 14, a blower 15, and a timer 16 to facilitate aerobic aeration. Three 8-hour cycles are performed daily, each consisting of a 30-minute water inlet, a 60-minute anoxic phase, a 300-minute aerobic phase, a 60-minute sedimentation phase, and a 30-minute drainage phase. Sedimentation time gradually decreases to 10 minutes as particle size increases. After seven days of incubation, magnetic iron oxide nanoparticles (Fe₃O₄) are added to the four photobioreactors 17. This stimulates the bacteria and algae to release large amounts of EPS, accelerating aggregation. The metal ions form ionic bridges with the EPS, thereby improving bacterial and algae adhesion and enhancing the dense particle structure. After a period of cultivation, the yellow aerobic granular sludge in the reactor began to turn green, forming a green bacteria-algae symbiotic aerobic granular sludge system.

[0062] For ease of understanding, the present application describes the solutions of the present application in the form of specific embodiments.

[0063] Unless otherwise specified, the aerobic granular sludge in each example and comparative example of the present application was acclimated according to the following method:

[0064] Place the aerobic activated sludge in a bucket and add an appropriate amount of clean water for 24 hours of aeration. Then, allow the sludge to settle and drain the supernatant. Add an appropriate amount of artificially prepared domestic wastewater as a nutrient solution. Continue cultivating for several days during the acclimation period, replacing the nutrient solution daily. Stop aeration 2 hours before replacing the nutrient solution, and drain the sludge regularly to maintain the mixed liquor suspended solids (MLSS) concentration within the range of 5000-6000 mg / L. After 10 days of acclimation, the bacterial colony is fully adapted.

[0065] The Chlorella in each embodiment and comparative example of the present application was cultured according to the following method:

[0066] In the experiment, the purchased common freshwater Chlorella liquid with strong oxygen production capacity, fast expansion speed and strong environmental adaptability was mixed with BG11 culture medium in a mass ratio of 1:1 and then divided into multiple sterile 500mL conical flasks. The conical flasks were then placed in a light incubator for expansion culture. Under the conditions of 25°C, a light-dark ratio of 12h:12h, and a light intensity of 3000lux, the culture was continued for several days, 200mL of nutrient solution was replaced every 3 days, and the mixture was stirred once every morning and evening to make it uniform. After continuous culture for several days until its color turned dark green, its concentration was measured;

[0067] The specific ingredients of the nutrient solution used in each example and comparative example of this application are shown in Table 1:

[0068] Table 1

[0069]

[0070] Example 1

[0071] This embodiment provides a wastewater treatment method, the treatment process is as follows Figure 2 The device shown is operated.

[0072] Construction of bacteria-algae symbiotic aerobic granular sludge: At room temperature, the acclimated activated sludge and algae liquid were poured into the photobioreactor 17 at a mass ratio of 1:1, and an appropriate amount of synthetic domestic wastewater was added; the composition of the synthetic wastewater in parts by weight is shown in Table 2:

[0073] Table 2

[0074]

[0075] The composition of the trace element solution is shown in Table 3:

[0076] Table 3

[0077]

[0078] Different concentrations of NaCl (10g / L, 20g / L, 30g / L, and 40g / L) were added to the synthetic wastewater to gradually increase its salinity to a range of 1% to 4%. The mass ratio of synthetic domestic wastewater to acclimated activated sludge was 400:1.

[0079] During the initial culture phase, 200 mL of nutrient solution was replaced every five days, allowing the culture to settle for one hour. Once the bacterial and algal system was well settled, the supernatant was replaced every two days, allowing the culture to settle for 30 minutes. Light strips 18 provided illumination for the photobioreactor 17, with a timer 16 controlling the duration of illumination to maintain a 12-hour light-to-dark ratio.

[0080] The operation mode is as follows: the photobioreactor 17 adopts an 8-h cycle model at room temperature and operates three cycles per day, including 30 minutes of static water inflow, 60 minutes of anaerobic stirring, 300 minutes of aerobic aeration, 60 minutes of sedimentation, and 30 minutes of water discharge. The hydraulic retention time (HRT) is maintained at 16 hours, the volume exchange rate is 50%, and the sludge retention time (SRT) is about 60 days.

[0081] After 40 to 60 days of cultivation, a stable bacteria-algae symbiotic aerobic system is formed.

[0082] (2) The wastewater with a salinity of 1% is input into the photobioreactor 17 and treated by the bacteria-algae symbiotic aerobic system; the operation mode is the same as step (1).

[0083] After testing, the total nitrogen (TN) removal rate of ABGS was 70.65%, NH4 + -N removal rate is greater than 99%.

[0084] Example 2

[0085] The difference between this embodiment and embodiment 1 is that in step (2), wastewater with a salinity of 2% is input into the photobioreactor 17 and treated by the bacteria-algae symbiotic aerobic system.

[0086] After testing, the TN removal rate of ABGS was 68.49%, NH4 + -N removal rate is greater than 99%.

[0087] Example 3

[0088] The difference between this embodiment and embodiment 1 is that in step (2), wastewater with a salinity of 3% is input into the photobioreactor 17 and treated by the bacteria-algae symbiotic aerobic system.

[0089] After testing, the TN removal rate of ABGS was 67.96%, and the NH4 + -N removal rate is greater than 99%.

[0090] Example 4

[0091] The difference between this embodiment and embodiment 1 is that in step (2), wastewater with a salinity of 4% is input into the photobioreactor 17 and treated by the bacteria-algae symbiotic aerobic system.

[0092] After testing, the TN removal rate of ABGS was 67.74%, NH4 + The -N removal rate was 84.8%.

[0093] The data of Examples 1-4 show that in the bacterial-algal symbiotic aerobic granular sludge system without the addition of magnetic iron oxide nanoparticles, the TN removal rate of ABGS decreased from 70.65% at 1% salinity to 67.96% at 3% salinity, and the NH4 + -N removal rate is greater than 99%. When the salinity rises to 4%, the TN removal rate of ABGS can still be maintained at about 67.74%, while NH4 + The -N removal rate decreased significantly, and the concentration increased to about 7.6 mg / L.

[0094] It can be seen that when the bacteria-algae symbiotic aerobic granular sludge system without the addition of magnetic iron oxide nanoparticles is used to treat high-salt wastewater, the ammonia nitrogen removal rate is significantly reduced.

[0095] Example 5

[0096] This embodiment provides a wastewater treatment method, the treatment process is as follows Figure 2 The device shown is operated.

[0097] Construction of bacteria-algae symbiotic aerobic granular sludge: At room temperature, the acclimated activated sludge and algae liquid were poured into the photobioreactor 17 at a mass ratio of 1:1, and an appropriate amount of synthetic domestic wastewater was added; the composition of the synthetic wastewater in parts by weight is shown in Table 4:

[0098] Table 4

[0099]

[0100] The composition of the trace element solution is shown in Table 5:

[0101] Table 5

[0102]

[0103] The mass ratio of artificial synthetic domestic wastewater to domesticated activated sludge is 400:1.

[0104] During the initial culture phase, 200 mL of nutrient solution was replaced every five days, allowing the culture to settle for one hour. Once the bacterial and algal system was well settled, the supernatant was replaced every two days, allowing the culture to settle for 30 minutes. Light strips 18 provided illumination for the photobioreactor 17, with a timer 16 controlling the duration of illumination to maintain a 12-hour light-to-dark ratio.

[0105] The operation mode is as follows: the photobioreactor 17 adopts an 8-h cycle model at room temperature and operates three cycles per day, including 30 minutes of static water inflow, 60 minutes of anaerobic stirring, 300 minutes of aerobic aeration, 60 minutes of sedimentation, and 30 minutes of water discharge.

[0106] After operating for 7 days in the above-mentioned operation mode, magnetic iron oxide nanoparticles Fe3O4 were added to the photobioreactor 17 at a concentration of 50 mg / L, and the operation was continued in the above-mentioned manner; the hydraulic retention time (HRT) was maintained at 8 h, the volume exchange rate was 50%, and the sludge retention time (SRT) was approximately 60 days.

[0107] After 35 to 50 days of cultivation, a stable bacteria-algae symbiotic aerobic system is formed.

[0108] (2) The wastewater with a salinity of 4% is input into the photobioreactor 17 and treated by the bacteria-algae symbiotic aerobic system; the operation mode is the same as step (1).

[0109] After testing, the total nitrogen (TN) removal rate of ABGS was 79.66%, NH4 + The -N removal rate was 92.44%.

[0110] Example 6

[0111] The difference between this embodiment and embodiment 5 is that the added amount of magnetic iron oxide nanoparticles Fe3O4 is 175 mg / L.

[0112] After testing, the total nitrogen (TN) removal rate of ABGS was 73.92%, NH4 + The -N removal rate was 90.25%.

[0113] Example 7

[0114] The difference between this embodiment and embodiment 5 is that the added amount of magnetic iron oxide nanoparticles Fe3O4 is 300 mg / L.

[0115] After testing, the total nitrogen (TN) removal rate of ABGS was 68.53%, NH4 + The -N removal rate was 88.87%.

[0116] The data of Examples 4-7 show that the denitrification performance of the bacteria-algae system with 50 mg / LFe3O4 added is the best, and the average TN removal rate is increased by 11.92% compared with 67.74% of the blank group.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating high-salinity wastewater by achieving bacterial and algal granulation and synergistic denitrification, characterized in that: The steps include: S1: Place microalgae and aerobic granular sludge in a photobioreactor for initial cultivation; S2: After the initial culture, magnetic iron oxide nanoparticles are added to the photobioreactor for enhanced culture to obtain bacteria-algae symbiotic aerobic granular sludge; S3: Denitrification treatment of wastewater using the bacteria-algae symbiotic aerobic granular sludge; The initial culture time is 6-8 days; The amount of the magnetic iron oxide nanoparticles added is 50-300 mg / L; The magnetic iron oxide nanoparticles are Fe3O4, which effectively solve the problems of slow aggregation and nucleation of bacteria and algae during the formation of ABGS, low activity of photosynthetic electron transporters in algal cells under high salt stress, and decreased denitrification efficiency. They simultaneously enhance the rapid aggregation and nucleation of bacteria and algal cells, improve the electron transfer efficiency of the photosynthetic system of algal cells under high salt stress, and improve the denitrification efficiency of microorganisms. In the initial culture stage and the intensive culture stage, the time ratio of the light phase to the dark phase is 12h:12h every day; After the initial cultivation, the extracellular polymers secreted by the bacterial and algal aggregates wrap the magnetic iron oxide nanoparticles, reducing their surface activity through coordination chelation or electrostatic adsorption, thereby reducing damage to microorganisms.

2. The method for treating high-salinity wastewater by achieving bacterial and algal granulation and synergistic denitrification according to claim 1, characterized in that: The microalgae is Chlorella.

3. The method for treating high-salinity wastewater by achieving bacterial and algal granulation and synergistic denitrification according to claim 2, characterized in that: In step S1, the mass ratio of the Chlorella to the aerobic granular sludge is 1:(1-10).

4. The method for treating high-salinity wastewater by achieving bacterial and algal granulation and synergistic denitrification according to claim 1, characterized in that: The illumination intensity during the illumination stage is 5000 lux.

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