Method for realizing stable operation of nitrosation by utilizing algal-bacterial symbiotic system

Abstract

The invention discloses a method for realizing stable operation of nitrosation by utilizing an algal-bacterial symbiotic system, relates to the technical field of sewage treatment, and provides the method for realizing stable operation of nitrosation by utilizing the algal-bacterial symbiotic system, which comprises the following steps: irradiating blue light on the algal-bacterial symbiotic system; according to the concentration of the solid substances in the algal-bacterial symbiotic system, the illumination intensity of the blue light is set according to a formula. According to the method disclosed by the invention, the response relationship between the light intensity of the blue light and the concentration of the solid substances is provided aiming at the shielding property of the solid substances such as activated sludge and algae in the algal-bacterial symbiotic system to the light, so that the blue light can be fully utilized; therefore, stable operation of a nitrosation system is maintained, and an important foundation is laid for stable operation of a wastewater short-cut nitrification and denitrification / short-cut nitrification anaerobic ammonia oxidation process.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a method for realizing stable operation of nitrite by utilizing a bacteria-algae symbiotic system. Background Art

[0002] In the field of modern water treatment and pollution control, the study of low-carbon nitrogen conversion pathways has become a hot topic. Among them, the short-range nitrification-anaerobic ammonium oxidation (PN / A) process has attracted much attention due to its advantages of high nitrogen conversion capacity, low energy consumption and less residual sludge. PN / A first oxidizes ammonia nitrogen to nitrite through short-range nitrification, and then converts nitrite and ammonia nitrogen into nitrogen gas simultaneously through anaerobic ammonium oxidation, achieving the goals of energy saving and pollution reduction. In this process, the stability of the nitrite reaction is crucial, especially when it is applied to the treatment of low-ammonia wastewater. At present, the shielding of light by bacteria and algae solids in the bacterial-algal symbiotic system results in limited light penetration and irradiation range, resulting in the bacterial-algal symbiotic system being mostly in laboratory small-scale tests and unable to be enlarged by engineering. In the process of realizing short-range nitrification in the bacterial-algal symbiotic system, how to use light sources to inhibit the activity of nitrifying bacteria in the nitrite system and drive the stable accumulation of nitrite has not received comprehensive attention. Summary of the invention

[0003] The purpose of the present invention is to provide a method for realizing stable operation of nitrite by using a bacteria-algae symbiotic system, so as to solve the problems existing in the above-mentioned prior art and realize stable operation of nitrite.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a method for realizing stable operation of nitrite by using a bacteria-algae symbiotic system, wherein the bacteria-algae symbiotic system is irradiated with blue light; the illumination intensity of the irradiated blue light is set according to the concentration of solid matter in the bacteria-algae symbiotic system; the illumination intensity of the irradiated blue light is greater than or equal to the blue light intensity calculated according to the formula shown in Formula 1;

[0006] y=-210+2.3x, where x is the concentration of solid matter and y is the light intensity.

[0007] Preferably, the ratio of the blue light illumination time to the dark time is 16h:8h; and the blue light illumination is performed continuously.

[0008] Preferably, the illumination intensity of the blue light is 100-3500 Lux; and the concentration of the solid substance is 100-3000 mg MLSS / L.

[0009] Preferably, the bacteria-algae symbiotic system is a symbiotic system formed by activated sludge and microalgae; the solid matter includes activated sludge and microalgae; the initial concentration of the solid matter in the bacteria-algae symbiotic system is 100 mg MLSS / L; the illumination intensity of the blue light is 100 Lux;

[0010] Preferably, as the concentration of solid matter in the bacteria-algae symbiotic system increases, the intensity of the blue light calculated according to the formula shown in Formula 1 is used to increase the intensity of the blue light irradiation.

[0011] Preferably, the method is carried out using a biological denitrification device; after activated sludge and microalgae are inoculated in the wastewater to be treated, blue light irradiation is performed for 24 hours a day during the startup phase of the biological denitrification device until the nitrite accumulation rate reaches more than 90%; during the normal operation of the biological denitrification device, the blue light irradiation time is adjusted to 16 hours / day.

[0012] Preferably, the biological denitrification device includes an outer shell, an illumination mechanism, a cleaning mechanism and a plurality of biological turntable mechanisms, the outer shell is provided with an inlet pipe for introducing wastewater, and an outlet pipe for discharging treated water, the biological turntable mechanism is installed in the outer shell, and the biological turntable mechanism can rotate in the outer shell, the lower part of the biological turntable mechanism is immersed in the wastewater, and the upper part of the biological turntable mechanism is located above the wastewater surface, the cleaning mechanism is installed on the inner wall of the outer shell, and the cleaning mechanism is used to clean the bacteria and algae film on the surface of the biological turntable mechanism, the illumination mechanism is located in the outer shell, and is used to provide illumination to the outer shell, the upper end of the outer shell is also provided with an air inlet for gas entry, and an air outlet for gas discharge, and the lower end of the outer shell is also provided with a mud discharge pipe for mud discharge.

[0013] Preferably, the outer shell includes a trough body and a cover, the cover can be snapped onto the upper end of the trough body, and the biological turntable mechanism and the cleaning mechanism are both installed in the trough body, and the illumination mechanism is installed on the inner top surface of the cover and / or the biological turntable mechanism; a plurality of partitions arranged in sequence are installed in the trough body, and the plurality of partitions divide the trough body into a plurality of treatment areas, the water inlet pipe is connected to the treatment area located at the first end, and the water outlet pipe is connected to the treatment area located at the second end, and adjacent treatment areas can be connected; the biological turntable mechanism includes a plurality of biological turntable assemblies, each of the treatment areas is rotatably installed with one biological turntable assembly, and the plurality of biological turntable assemblies are coaxially arranged, and each of the biological turntable assemblies is formed by a plurality of biological turntables connected to the same rotating shaft.

[0014] Preferably, the illumination mechanism comprises a plurality of light sources, and the plurality of light sources are evenly distributed on the inner top surface of the cover and the end surface of the biological turntable; and the inner surface of the cover and the surface of the biological turntable are both provided with a reflective layer.

[0015] Preferably, the cleaning mechanism is a brush, one side of the brush is mounted on the inner wall of the outer shell through a lifting mechanism, and the other side of the brush extends toward the outer edge of the biological turntable mechanism.

[0016] Compared with the prior art, the present invention has achieved the following technical effects:

[0017] The present invention provides a method for realizing stable operation of nitrite by using a bacteria-algae symbiotic system, irradiating the bacteria-algae symbiotic system with blue light; and setting the illumination intensity of the blue light according to a formula according to the concentration of solid matter in the bacteria-algae symbiotic system. The method of the present invention proposes a response relationship between the light intensity of blue light and the concentration of solid matter in view of the shielding of light by solid matter such as activated sludge and algae in the bacteria-algae symbiotic system, ensuring that the blue light can be fully utilized, thereby maintaining the stable operation of the nitrite system, and laying an important foundation for the stable operation of the wastewater short-range nitrification and denitrification / short-range nitrification anaerobic ammonia oxidation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a top view of the biological denitrification device of the present invention (part of the cover is omitted);

[0020] Figure 2 for Figure 1 The cross-sectional view at AA;

[0021] Figure 3 for Figure 1 Cross-sectional view at BB;

[0022] Figure 4 It is a schematic diagram of the structure of the biological turntable in the present invention;

[0023] In the figure: 1-tank body, 2-cover, 3-water inlet pipe, 4-water outlet pipe, 5-air inlet hole, 6-air outlet hole, 7-rotating shaft, 8-biological turntable, 9-brush, 10-mud discharge pipe, 11-light source, 12-partition plate, 13-barrier unit plate. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention provides a method for realizing stable operation of nitrite by using a bacteria-algae symbiotic system, wherein the bacteria-algae symbiotic system is irradiated with blue light; the illumination intensity of the irradiated blue light is set according to the concentration of solid matter in the bacteria-algae symbiotic system; the illumination intensity of the irradiated blue light is greater than or equal to the blue light intensity calculated according to the formula shown in Formula 1;

[0026] y=-210+2.3x, where x is the concentration of solid matter and y is the light intensity.

[0027] The method of the present invention aims at the light shielding property of activated sludge in the bacteria-algae symbiotic system, proposes a response relationship between the intensity of blue light and the concentration of activated sludge, ensures that the sludge can be fully irradiated, and then inhibits all NOB activities, thereby maintaining the stable operation of the nitrite system.

[0028] The present invention adopts blue light as the light source of the bacteria-algae symbiotic system to stimulate the secretion of extracellular polymers (blue light stimulates extracellular polymers, EPS), enhance the activity of antioxidant enzymes, effectively reduce the level of reactive oxygen, resist oxidative stress damage, efficiently inhibit the growth of nitrifying bacteria, promote the accumulation of nitrite, provide favorable conditions for nitrosation reaction, and thus be beneficial to the stability of nitrosation reaction.

[0029] Under different light sources, nitrogen conversion in the bacterial-algal symbiotic system showed significant differences. Compared with other light sources (darkness, ultraviolet light, white light (composite light), green light and red light), the ammonia nitrogen removal rate (NaRE) of blue light is the most ideal. And blue light can significantly promote NO 2- -N generation. In addition, blue light can only effectively inhibit NOB activity, making the nitrous oxide accumulation rate (NiAE) as high as 100%. Nitrous oxide accumulation rate (NiAR) is a key indicator to characterize AOB activity. Blue light can significantly promote the nitrite reaction rate, and NiAR is high. Secondly, blue light significantly promotes the synergistic effect of bacteria and algae and microbial diversity. Therefore, blue light plays an important role in promoting NO in the nitrite process. 2- -N accumulation rate and accumulation rate have significant advantages.

[0030] In the specific implementation of the present invention, the blue light source is placed outside the bacteria-algae symbiotic system, and the material of the bacteria-algae symbiotic system container is a transparent material; or, the blue light source is built into the bacteria-algae symbiotic system, and the inner side of the bacteria-algae symbiotic system container is a reflective material to ensure full utilization of the light source. In the specific implementation of the present invention, the irradiation of blue light can be achieved through optical fiber light guide technology, LED or other light-emitting media.

[0031] In one embodiment of the present invention, as the concentration of solid matter in the bacteria-algae symbiotic system increases, the intensity of the blue light calculated according to the formula shown in Formula 1 is used to increase the intensity of the blue light irradiation.

[0032] In one embodiment of the present invention, the ratio of the illumination time of the blue light to the dark time is 16h:8h; the illumination cycle of the blue light is 24h, wherein the illumination time is 16h and the dark time is 8h; the irradiation of the blue light is performed continuously. The present invention provides DNA repair time for functional microorganisms such as aerobic ammonia oxidizing bacteria by setting a reasonable illumination cycle (16h illumination, 8h dark), thereby further improving the stability of the bacterial-algal symbiotic system.

[0033] In the specific implementation process of the present invention, the illumination intensity of the blue light is 100-3500 lux, further is 100 lux, 500 lux, 900 lux, 1300 lux, 1700 lux, 2100 lux, 2500 lux, 2900 lux, 3300 lux or 3500 lux; the concentration of the solid substance is 100-3000 mgMLSS / L, further is 100 mgMLSS / L, 500 mgMLSS / L, 900 mgMLSS / L, 1300 mgMLSS / L or 3000 mgMLSS / L; the peak value of the blue light is 445 nm.

[0034] In one embodiment of the present invention, the concentration of the solid matter is 100 mg MLSS / L; the illumination intensity of the blue light is 100 lux. With low MLSS, the light source can better penetrate the water body and fully act on the microorganisms, thereby improving the reaction efficiency. The use of low light intensity can effectively reduce the energy consumption of lighting equipment, especially in the sewage treatment process, the optimized configuration of light intensity enables the system to reduce energy consumption while still maintaining a high treatment effect.

[0035] In another embodiment of the present invention, the concentration of the solid substance is 500 mg MLSS / L; the illumination intensity of the blue light is ≥ 900 lux, further 900 lux.

[0036] In another embodiment of the present invention, the concentration of the solid substance is 900 mg MLSS / L; the illumination intensity of the blue light is ≥ 1700 lux, further 1700 lux.

[0037] In another embodiment of the present invention, the concentration of the solid substance is 1300 mg MLSS / L; the illumination intensity of the blue light is ≥ 2900 lux, further 2900 lux.

[0038] In one embodiment of the present invention, the bacteria-algae symbiotic system is a symbiotic system formed by activated sludge and microalgae; the solid matter includes activated sludge and microalgae, and further, the solid matter consists of activated sludge and microalgae; the present invention has no special restriction on the ratio of the activated sludge and microalgae, and the conventional ratio in the art can be adopted; the method is carried out using a biological denitrification device; after the activated sludge and microalgae are inoculated in the wastewater to be treated, during the startup phase of the biological denitrification device, 24 hours of blue light irradiation is carried out throughout the day until the nitrite accumulation rate reaches more than 90%, and the bacteria-algae symbiotic system stabilizes nitrite. The present invention maintains environmental stability by 24 hours of blue light irradiation throughout the day, and achieves the enrichment of nitrite-forming microorganisms and the inhibition of nitrifying microorganisms in the system by stabilizing environmental conditions; during the normal operation of the biological denitrification device, the blue light irradiation time is adjusted to 16h / d.

[0039] In one embodiment of the present invention, the initial concentration of solid matter in the bacteria-algae symbiotic system is 100 mgMLSS / L; and the illumination intensity of the blue light is 100 lux.

[0040] In one embodiment of the present invention, the activated sludge is ordinary activated sludge from a municipal sewage treatment plant; the microalgae are inoculated Chlorella or Coralleaf or are microalgae species that come with the activated sludge. When the microalgae species come with the activated sludge, the solid matter is activated sludge.

[0041] In one embodiment of the present invention, the wastewater is wastewater containing ammonia nitrogen; the wastewater containing ammonia nitrogen is low ammonia wastewater or low carbon nitrogen ratio wastewater; the ammonia nitrogen content of the wastewater is ≤80 mg / L; the COD / nitrogen concentration ratio of the wastewater is <1. The bacteria-algae symbiotic system of the present invention is used for wastewater denitrification treatment.

[0042] In one embodiment of the present invention, the concentration of dissolved oxygen in the bacteria-algae symbiotic system is 0.1-0.5 mg / L; the dissolved oxygen in the bacteria-algae symbiotic system is provided by microalgae; when the concentration of microalgae is high, resulting in a high concentration of dissolved oxygen, the concentration of dissolved oxygen is adjusted by reducing the illumination time of blue light.

[0043] In one embodiment of the present invention, the temperature of the bacteria-algae symbiotic system is 10-25° C.; the pH value of the bacteria-algae symbiotic system is 7-8.5.

[0044] In one embodiment of the present invention, the method is carried out using a biological denitrification device.

[0045] In one embodiment of the present invention, after activated sludge and microalgae are inoculated in the biological denitrification device, wastewater is introduced.

[0046] like Figure 1 to Figure 4 As shown, the biological denitrification device in this embodiment includes an outer shell, an illumination mechanism, a cleaning mechanism and a plurality of biological rotary disk mechanisms. The outer shell is provided with an inlet pipe 3 for introducing wastewater and an outlet pipe 4 for discharging treated water, thereby realizing wastewater treatment and replenishment. The biological rotary disk mechanism is installed in the outer shell, and the outer shell is used to play a certain sealing role to prevent odor from overflowing. The biological rotary disk mechanism can rotate in the outer shell, thereby making the mixed water quality in the outer shell uniform, and no other stirring device is required, so that the structure is simpler and the cost is lower. The lower part of the biological rotary disk mechanism is immersed in In the wastewater, the upper part of the biological turntable mechanism is located above the wastewater surface, so that the upper part of the biological turntable mechanism is exposed to the air and the lower part is submerged in the water. At the same time, with the rotation of the biological turntable mechanism, an anaerobic and aerobic exchange can be formed. Preferably, the water level in the outer shell makes 1 / 3 of the biological turntable mechanism underwater and 2 / 3 exposed to the air. For the part of the biological turntable mechanism located underwater, the solid concentration around it is preferably controlled at 100 mgSS / L to enhance the light transmittance and utilization rate. The cleaning mechanism is installed on the inner wall of the outer shell, and the cleaning mechanism is used to clean the biological turntable mechanism. The bacterial algae film on the surface, as the reaction proceeds, when the thickness of the bacterial algae film accumulated on the surface of the biological turntable mechanism is high, the bacterial algae film can contact the cleaning mechanism, and then as the biological turntable mechanism rotates, a part of the bacterial algae film can be scraped off to maintain the film thickness of the bacteria and algae, so as to facilitate the irradiation depth of light and the inhibition of nitrifying bacteria inside the biofilm on the biological turntable mechanism. The lighting mechanism is located in the outer shell and is used to provide light to the outer shell, and the light can be one of blue light or ultraviolet light, or a combination of light. At the same time, both LED lights and optical fiber materials can be used for lighting, and then through the lighting mechanism The growth of NOB in the nitrite process is inhibited, and at the same time, partial resource recovery of valuable substances is achieved through algae, effectively solving the stability problem of denitrification in the partial nitrite-anaerobic ammonia oxidation process under low-temperature and low-ammonia environment. The upper end of the outer shell is also provided with an air inlet 5 for gas entry, so there is no need to set up an aeration device. The oxygen mainly comes from the photosynthesis of algae. When the oxygen is insufficient, the oxygen of the bacteria-algae symbiotic system can be supplemented by inhaling air through the air inlet 5. The upper end of the outer shell is also provided with an air outlet 6 for gas discharge, which can realize the collection of tail gas. The lower end of the outer shell is also provided with a mud discharge pipe 10 for mud discharge.

[0047] The outer shell includes a tank body 1 and a cover 2. The cover 2 can be buckled on the upper end of the tank body 1 to play a sealing role. The biological turntable mechanism and the cleaning mechanism are both installed in the tank body 1. The illumination mechanism is installed on the inner top surface of the cover 2 and / or on the biological turntable mechanism to ensure the light intensity. In actual application, the part of the biological turntable mechanism exposed to the air can be illuminated by the illumination mechanism located on the inner top surface of the cover 2. At the same time, the part submerged in water adopts a low sludge volume system, which cooperates with the illumination mechanism installed on the biological turntable mechanism for partial illumination to achieve NOB activity inhibition, which can effectively solve the light irradiation problem of light reaction; a plurality of partitions 12 arranged in sequence are installed in the tank body 1, and the plurality of partitions 12 divide the tank body 1 into a plurality of treatment areas. The water inlet pipe 3 is connected to the treatment area at the first end. domain, the outlet pipe 4 is connected to the treatment area located at the second end, and adjacent treatment areas can be connected; the biological turntable mechanism includes multiple biological turntable assemblies, each treatment area has a biological turntable assembly rotatably installed, and the multiple biological turntable assemblies are coaxially arranged, each biological turntable assembly can be driven by the same rotating shaft 7, each biological turntable assembly is formed by multiple biological turntables 8 connected to the same rotating shaft 7, and there is a spacing between adjacent biological turntables 8, the spacing is preferably 65mm, the diameter of the biological turntable 8 is preferably 2-3m, and the thickness is preferably 1-15m. The biological turntable 8 is preferably made of transparent polymer fiber, more preferably made of wavy glass fiber, which can increase the surface roughness and facilitate the attachment of bacteria and algae. At the same time, the built-in luminescent light source material can improve the utilization rate of the light source.

[0048] The number of biological rotary disk mechanisms can be determined according to the pollutant load, and can be a single group or multiple groups. When multiple groups are provided, each biological rotary disk mechanism can be separated by installing a barrier unit plate 13 inside the outer shell.

[0049] The illumination mechanism includes a plurality of light sources 11, which are evenly distributed on the inner top surface of the cover 2 and the end surface of the biological turntable 8. As another embodiment, the light source 11 can also be arranged outside the outer shell, but in this case the outer shell needs to be transparent to ensure that it can transmit light; the inner surface of the cover 2 and the surface of the biological turntable 8 are both provided with a reflective layer to improve the utilization rate of the light source. In actual application, the on and off time of the light source 11 can also be adjusted according to the required illumination time.

[0050] The cleaning mechanism is a brush 9, one side of which is installed on the inner wall of the outer shell through a lifting mechanism. The lifting mechanism can drive the brush 9 to rise and fall, and the other side of the brush 9 extends toward the outer edge of the biological turntable mechanism to achieve control of the thickness of the algae film on the surface of the biological turntable mechanism.

[0051] In order to further illustrate the present invention, the technical solution provided by the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0052] Example 1 A method for achieving stable operation of nitrite using a bacterial-algal symbiotic system

[0053] 1. Device and control parameters

[0054] The biological denitrification device in the present embodiment was used, with the temperature controlled at 25±1° C., the HRT controlled at 24 h, and the DO controlled at 0.1 mg / L.

[0055] 2. Simulated wastewater and inoculated mud source

[0056] The wastewater is artificially simulated and NH4 + -N concentration is controlled at 50mg / L; the influent does not contain NO2 - -N、NO3 - -N. The inoculated sludge is activated sludge from a sewage treatment plant.

[0057] 3. Light source and method

[0058] The light source is blue light: the peak is 445nm.

[0059] Regulation of light intensity and activated sludge concentration: the light intensity is 100 lux, and the activated sludge concentration is 100 mg MLSS / L. At the initial start-up, the activated sludge concentration is 100 mg MLSS / L, and the system is irradiated with 100 lux of blue light for 24 hours, and then wastewater containing ammonia nitrogen is introduced to achieve the enrichment of nitrite microorganisms and the inhibition of nitrifying microorganisms in the system by stabilizing environmental conditions. After the system is stable, the illumination time is adjusted to a light cycle of 24 hours, with 16 hours of illumination time and 8 hours of darkness. Irradiate the bacteria-algae symbiotic system with blue light; according to the concentration of solid matter in the bacteria-algae symbiotic system, set the light intensity of the blue light according to the formula shown in Formula 1. The dissolved oxygen in the bacteria-algae symbiotic system is provided by microalgae, and the dissolved oxygen concentration is controlled at 0.1-0.5 mg / L. When the concentration of microalgae is high, resulting in high dissolved oxygen, it is preferred to reduce the illumination time rather than the light intensity. Temperature and pH control: The temperature of the bacteria-algae symbiotic system is controlled at 10-25°C, and the pH value is controlled at 7-8.5.

[0060] Comparative Example 1 Experiments with different light intensities at different sludge concentration levels

[0061] Divided into groups B to E, each with 6 treatments, the lighting time is unified as 24h, as follows:

[0062] Group B: MLSS was controlled at 100 mg / L, and the blue light intensity was set to B1 (0 lux), B2 (100 lux), B3 (500 lux), B4 (900 lux), B5 (1300 lux), and B6 (1700 lux);

[0063] Group C: MLSS was controlled at 500 mg / L, and the blue light intensity was set to C1 (0 lux), C2 (100 lux), C3 (500 lux), C4 (900 lux), C5 (1300 lux), and C6 (1700 lux);

[0064] Group D: MLSS was controlled at 900 mg / L, and the blue light intensity was set to D1 (0 lux), D2 (900 lux), D3 (1300 lux), D4 (1700 lux), D5 (2100 lux), and D6 (2500 lux);

[0065] Group E: MLSS was controlled at 1300 mg / L, and the blue light intensity was set to E1 (0 lux), E2 (1700 lux), E3 (2100 lux), E4 (2500 lux), E5 (2900 lux), and E6 (3300 lux).

[0066] The method is as in Example 1. The following detection is performed:

[0067] 1. Routine water quality analysis

[0068] During the operation of the biological denitrification device, the inlet and outlet NH4 + -N, NO2 - -N、NO3 - -N, pH value, DO are measured. NH4 + -N using sodium reagent spectrophotometry, NO2 - -N、NO3 - -N was determined by ion chromatography, and pH and DO were determined by online monitoring equipment.

[0069] 2. EPS extraction and analysis

[0070] After taking 2g of sludge homogenate, the sludge suspension was mixed with distilled water in a volume ratio of 1:9, and placed in a constant temperature water bath at 80℃ for crude extraction for 45min. After cooling, it was centrifuged at 4℃ and 14000r / min for 25min. The supernatant was taken to determine the polysaccharide and protein. The polysaccharide was determined by the sulfuric acid-phenol method, and the protein was determined by the method in the Tiangen BCA protein quantification kit.

[0071] 3. Active oxygen analysis

[0072] The anti-oxidative stress capacity of sludge was analyzed by measuring intracellular ROS. The intracellular reactive oxygen species of sludge samples were measured using a ROS detection kit (DCFH-DA S0033, Beyotime, China). The sludge samples obtained after washing with 0.1×PBS were resuspended in 0.5mL DCFH-DA (1:1000 configuration) working solution and incubated at 37°C in the dark. Then, the samples were washed twice with 0.1×PBS to remove excess fluorescent dye, and the supernatant was taken and the fluorescence intensity was detected by a microplate reader (BioTek Synergy H1, USA) at 488nm excitation / 525nm emission wavelength. The ROS content of the samples at each time period was expressed as the ratio of its fluorescence intensity to the fluorescence intensity of the dark group sludge samples (Ni et al., 2022). The bottom mud-water mixture was taken to make a slide, and the fluorescent area was observed on a fluorescence inverted microscope (IX73, China).

[0073] 4. Enzyme activity analysis

[0074] Crude enzyme extraction: Take 10mL of sludge, centrifuge at 4℃ (8000g, 10min), wash the sludge twice with 0.01M PBS with pH=7.4 and resuspend. Place the centrifuge tube containing the sludge on ice, break the wall with an ultrasonic wall breaking machine for 5min (20KHZ, 4℃, ultrasonic treatment for 2s, pause for 3s), centrifuge at 12000g for 10min at 4℃ after breaking, and take the supernatant for enzyme activity test.

[0075] Lactate dehydrogenase (LDH) activity: LDH content was determined using a lactate dehydrogenase assay kit (A020-2, Jiancheng, Nanjing, China).

[0076] Catalase (CAT) activity: Catalase assay kit (A007-1-1, Jiancheng, Nanjing, China) was used to determine CAT activity. The main principle is that the reaction of catalase decomposing H2O2 can be quickly terminated by adding ammonium molybdate, and the remaining H2O2 reacts with ammonium molybdate to produce a light yellow complex. The change in the complex is measured at 405nm, and the activity of CAT can be calculated.

[0077] Superoxide dismutase (SOD) activity: SOD activity was determined using a superoxide dismutase assay kit (A001-3, Jiancheng, Nanjing, China).

[0078] 5. High-throughput sequencing

[0079] 2g of wet sludge was taken and entrusted to Majorbio Bio-Pharm Technology Co. Ltd. (Shanghai, China) for microbial high-throughput sequencing and population analysis. The total DNA extracted was PCR amplified and purified using primers 338F (ACTCCTACGGGAAGCA, SEQ ID NO.1) and 806R (GGACT ACHVGGGTWTCTAAT, SEQ ID NO.2) in the V3-V4 region of the bacterial 16S rRNA gene, and then high-throughput sequencing was performed on the Illumina sequencing platform Miseq PE 300. Finally, the valid data of each sample was subjected to OUT cluster analysis and species taxonomy analysis.

[0080] 6. Metagenomic analysis

[0081] The samples were commissioned to Majorbio Bio-Pharm Technology Co. Ltd. (Shanghai, China) for metagenomic sequencing. After DNA extraction from the samples, a NEXTFLEX RapidDNA-Seq (Bioo Scientific, US) library was constructed and sequenced for quality control analysis. High-quality reads were aligned with the non-redundant gene set (95% identity) using SOAPaligner software (V.2.21) to count the abundance of each gene in the sample. The amino acid sequence of the non-redundant gene set was aligned with the NR database using Diamond software (V.0.8.35) to obtain species annotation information, and the abundance of the species was calculated based on the gene abundance corresponding to the species. Similarly, the amino acid sequence of the non-redundant gene set was aligned with the KEGG database to obtain the KEGG functional annotation of the gene.

[0082] The results are as follows:

[0083] The level of MLSS affects the penetration depth of light in the reactor and the effective irradiation of microorganisms, and has an important impact on the performance and efficiency of the nitrification system.

[0084] In group B, MLSS was controlled at 100 mg / L and different intensities of blue light irradiation were performed. Low-intensity blue light B2 (100 lux) has a continuous and stable ammonia nitrogen removal capacity, and NaRE steadily increased from 40.82% to 57.2%. For B3 (500 lux), B4 (900 lux), B5 (1300 lux) and B6 (1700 lux), although NaRE can reach 61.66%, 54.62%, 62.1% and 61.52% respectively after only 10 days, they dropped sharply to 46.2%, 39.8%, 23.19% and 16.37% respectively at 35 days. In NO2- In terms of -N generation, the high light intensity B6 (1700 lux) achieved a NiAE value of 99.27% ​​in just 3 days, but after the 10th day, the NiAE dropped sharply to 18.19%, indicating that high light intensity has an inhibitory effect on the performance of AOB. 2- -N concentration was maintained at 21.64±2.47mg / L within 22-34 days, and NiAE fluctuated within 97.84%, with significantly better stability than other light intensities. In addition, the highest NiAR of B2 (100lux) was 0.0238kg / (m 3 ·d), showing NO2 - The advantage of efficient accumulation of -N indicates that for the nitrification system with MLSS of 100 mg / L, NiAE and NiAR with blue light of 100 lux have long-term stability.

[0085] After the MLSS of group C was raised to 500 mg / L, the average NaRE of C2 (100 lux) and C3 (500 lux) were 36.72% and 39.82% respectively within 35 days, which were 19.65% and 29.75% higher than that of C1 (0 lux). The NaRE of C4 (900 lux) was relatively stable, maintaining at around 42.06%. The NaRE of C5 (1300 lux) and C6 (1700 lux) fluctuated greatly. Among them, the NaRE of C6 (1700 lux) dropped from 61.28% on the 10th day to 27.8% on the 30th day. 2- In terms of -N accumulation, high light intensity also achieved rapid nitrification, but the maintenance time was shorter. Within 20 to 35 days, the NiAE of C5 (1300 lux) and C6 (1700 lux) were 93.36% and 91.78%, but the NiAR was as low as 0.0124 and 0.0074 kg / (m3·d), respectively. In low light intensity, as the light intensity increased from 0 to 900 lux, the NiAR also increased, and the NiAR of C4 (900 lux) could be as high as 0.0231 kg / (m 3 ·d), which is 2.68 times that of C1(0lux). - -N generation, during the 10-35d period, the average NO3 - -N concentration will be higher than C4 (900lux), C5 (1300lux) and C6 (1700lux). Therefore, the light intensity needs to be increased to 900lux to maintain high NiAE and high NiAR for a MLSS of 500mg / L system.

[0086] When the MLSS in group D was raised to 900 mg / L, the maximum light intensity was further increased to 2500 lux. During the 10-35 days, the NaRE of D4 (1700 lux) could reach 53.84%, and the NO 2- -N concentration is up to 22.45mg / L, and can achieve 99.73% NiAE and 0.0225kg / (m 3 ·d) NiAR has certain advantages in promoting and stabilizing the nitrosation reaction. For high light intensity D6 (2500lux), although NiAE is above 97% in 25-35d, the NiAR value is always at 0.0050kg / (m 3 ·d) or less. For the low light intensity D2 (900 lux) group, NO 3- -N concentration is equivalent to the level of D1 (0lux), NiAR is as low as 50.32%, and NiAR is 0.0104kg / (m3·d). Under low light intensity, NOB activity is higher than AOB. In summary, when MLSS is increased to 900mg / L, the blue light intensity needs to reach 1700lux to maintain the stability of the nitrification system.

[0087] Group E increased MLSS to 1300 mg / L and the maximum light intensity to 3300 lux. During the 10-35 day period, the average NaRE of E2 (1700 lux), E3 (2100 lux), E4 (2500 lux) and E5 (2900 lux) were higher than that of E1 (0 lux), and NaRE increased with the increase of light intensity. In E5 (2900 lux), NaRE was as high as 52.79%. However, when the light intensity reached 3300 lux, the average NaRE of E6 decreased to 38.84%. In terms of NiAE, E4 (2500 lux) and E5 (2900 lux) could be as high as 100%. In NO 3- -N generation, E4 (2500lux) and E5 (2900lux) NO3 - -N concentration was maintained below 1 mg / L after 8 days. Among them, the highest NiAR of E5 (2900 lux) was 0.0210 kg / (m 3 ·d), which is significantly better than other light intensities. Therefore, for the nitrification system with MLSS of 1300 mg / L, the blue light intensity of 2900 lux has the best long-term accumulation of NO 2- Advantages of -N.

[0088] In summary, in different light intensities at different sludge levels, the EPS content increased with the increase of light intensity, but the EPS concentration decreased significantly when the optimal light intensity was exceeded. For example, in a blue light system with an MLSS of 100 mg / L, as the light intensity increased from B1 (0 lux) to B4 (1300 lux), the EPS content increased from 116.48±3.31 mg / gVSS to 188.79±4.47 mg / gVSS. However, when the light intensity increased to B6 (1700 lux), the EPS content dropped significantly to 123.64±3.32 mg / gVSS. At this time, when the light intensity exceeded the bacterial tolerance threshold, a large number of cells died, and the LDH concentration rose to 0.15-0.2 U / mgprot, resulting in a decrease in EPS secretion capacity. High light intensity (B5 and B6) also caused the SOD and CAT contents to drop to 10-15 and 0.5-0.8 U / mgprot, respectively, indirectly causing an increase in the relative value of ROS fluorescence intensity.

[0089] In the blue light system with MLSS of 100 mg / L, the relative abundances of Ellin6067, Ardenticatenales and Nitrosomonas in B2 (100 lux) were as high as 3.38%, 2.67% and 1.29%, respectively, while in the high light intensity B6 (1700 lux) group, they were as low as 0.69%, 0.51% and 0.05%, respectively. The relative abundances of Nitrospira in B1 (0 lux), B2 (100 lux), B3 (500 lux), B4 (900 lux), B5 (1300 lux) and B6 (1700 lux) groups were 1.06%, 0.08%, 0.72%, 0.28% and 0.02%, respectively. Prolonging the blue light irradiation time can effectively inhibit Nitrospira. The relative abundance of Nitrospira in F5 (24h / 0h) was 0.15%, which was 64% lower than that in F1 (0h / 24h). Providing an 18h / 6h light-dark ratio is more conducive to AOB survival than 24h light. The relative abundance of Ellin6067 in F1 (0h / 24h), F2 (6h / 8h), F3 (12h / 12h), F4 (18h / 6h) and F5 (24h / 0h) were 0.84%, 1.23%, 1.69%, 2.78% and 1.80%, respectively.

[0090] Comparative Example 2 Effect of Light Exposure Time on Nitrite

[0091] The light source is blue light, the light intensity is 100 lux, and the initial inoculation activated sludge concentration is 100 mg MLSS / L. The light-dark ratio is set to F1 (0h / 24h), F2 (6h / 18h), F3 (12h / 12h), F4 (18h / 6h) and F5 (24h / 0h).

[0092] The method is as in Example 1. Conventional water quality analysis and EPS extraction and analysis are performed as in Comparative Example 1.

[0093] The results showed that under different light exposure times, the NaRE of F2 (6h / 18h), F3 (12h / 12h), F4 (18h / 6h) and F5 (24h / 0h) were all maintained at about 45%, with small overall differences, and were significantly better than F1 (0h / 24h). 2- The amount of -N generated increases with the increase of the proportion of light time, which further shows that the appropriate amount of light helps to stabilize the nitrite system. However, when the light-dark ratio increases to 24h / 0h, a turning point occurs. At this time, the NO of F5 (24h / 0h) 2- -N generation will be lower than F4 (18h / 6h). 3- In terms of -N generation, the average concentrations of F1 (0h / 24h), F2 (6h / 18h) and F3 (12h / 12h) were 11.85, 7.88 and 6.36 mg / L respectively, which were higher than those of F4 (18h / 6h) and F5 (24h / 0h). Among them, the NiAE of F4 (18h / 6h) could reach up to 100%, and the NiAR could reach up to 0.0259 kg / (m 3 ·d), which was 3.73 times higher than that of F1 (0h / 24h), showing a better nitrosation potential. Therefore, optimizing the lighting conditions and providing a suitable light-dark ratio (18h / 6h) can significantly promote the nitrosation process.

[0094] In summary, the illumination time will affect the EPS content and antioxidant enzyme activity. With the increase of the blue light-dark ratio, the EPS concentration increased significantly. The EPS concentration of F5 (24h / 0h) was 1.87 times that of F1 (0h / 24h). The CAT and SOD activities of F4 (16h / 8h) were 2.21±0.04U / mgpro and 31.65±0.53U / mgprot, respectively, which were significantly higher than the others.

[0095] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for achieving stable operation of nitrite by using a bacterial-algal symbiotic system, characterized in that: The bacteria-algae symbiotic system is irradiated with blue light; the illumination intensity of the irradiated blue light is set according to the concentration of solid matter in the bacteria-algae symbiotic system; the illumination intensity of the irradiated blue light is greater than or equal to the blue light intensity calculated according to the formula shown in Formula 1; y=-210+2.3x, where x is the concentration of solid matter and y is the light intensity.

2. The method according to claim 1, characterized in that: The ratio of the blue light illumination time to the dark time is 16h:8h.

3. The method according to claim 1, characterized in that The illumination intensity of the blue light is 100-3500 Lux; the concentration of the solid substance is 100-3000 mg MLSS / L.

4. The method according to claim 1, characterized in that: The bacteria-algae symbiotic system is a symbiotic system formed by activated sludge and microalgae; the solid matter includes activated sludge and microalgae; the initial concentration of the solid matter in the bacteria-algae symbiotic system is 100 mg MLSS / L; and the illumination intensity of the blue light is 100 Lux.

5. The method according to claim 1, characterized in that As the concentration of solid matter in the bacteria-algae symbiotic system increases, the intensity of the blue light is increased according to the blue light intensity calculated by the formula shown in Formula 1.

6. The method according to claim 1, characterized in that The method adopts a biological denitrification device; after activated sludge and microalgae are inoculated in the wastewater to be treated, blue light irradiation is performed for 24 hours a day during the startup stage of the biological denitrification device until the nitrite accumulation rate reaches more than 90%; during the normal operation of the biological denitrification device, the blue light irradiation time is adjusted to 16 hours / day.

7. The method according to claim 6, characterized in that The biological denitrification device includes an outer shell, an illumination mechanism, a cleaning mechanism and a plurality of biological rotary disk mechanisms. The outer shell is provided with an inlet pipe for introducing wastewater and an outlet pipe for discharging treated water. The biological rotary disk mechanism is installed in the outer shell and can rotate in the outer shell. The lower part of the biological rotary disk mechanism is immersed in the wastewater, and the upper part of the biological rotary disk mechanism is located above the wastewater surface. The cleaning mechanism is installed on the inner wall of the outer shell and is used to clean the bacteria and algae film on the surface of the biological rotary disk mechanism. The illumination mechanism is located in the outer shell and is used to provide illumination to the outer shell. The upper end of the outer shell is also provided with an air inlet for gas to enter and an air outlet for gas to discharge. The lower end of the outer shell is also provided with a mud discharge pipe for mud discharge.

8. The method according to claim 7, characterized in that The outer shell includes a trough body and a cover, the cover can be snapped onto the upper end of the trough body, and the biological turntable mechanism and the cleaning mechanism are both installed in the trough body, and the illumination mechanism is installed on the inner top surface of the cover and / or the biological turntable mechanism; a plurality of partitions arranged in sequence are installed in the trough body, and the plurality of partitions divide the trough body into a plurality of treatment areas, the water inlet pipe is connected to the treatment area located at the first end, and the water outlet pipe is connected to the treatment area located at the second end, and adjacent treatment areas can be connected; the biological turntable mechanism includes a plurality of biological turntable assemblies, each of the treatment areas is rotatably installed with a biological turntable assembly, and the plurality of biological turntable assemblies are coaxially arranged, and each of the biological turntable assemblies is formed by a plurality of biological turntables connected to the same rotating shaft.

9. The method according to claim 8, characterized in that The illumination mechanism comprises a plurality of light sources, and the plurality of light sources are evenly distributed on the inner top surface of the cover and the end surface of the biological turntable; the inner surface of the cover and the surface of the biological turntable are both provided with a reflective layer.

10. The method according to claim 7, characterized in that The cleaning mechanism is a brush, one side of which is mounted on the inner wall of the outer shell through a lifting mechanism, and the other side of which extends toward the outer edge of the biological turntable mechanism.

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