Method for culturing low-temperature aerobic granular sludge

Abstract

The invention discloses a method for culturing low-temperature aerobic granular sludge, and relates to the technical field of sewage treatment, and the method adopts a high-concentration dissolved oxygen (DO) aeration and long-period operation mode to improve the tolerance and adhesion capacity of microorganisms to a low-temperature environment by enhancing the carbon metabolism capacity and extracellular polymeric substance secretion of the microorganisms. Meanwhile, the operation mode of combining high aeration and mechanical stirring not only can generate larger shearing force to remove loose biological membranes on the surface of the sludge, but also can enhance the aggregation ability of the microorganisms by promoting quorum sensing phenomena among fimbriae, flagellum and the microorganisms. The intermittent operation mode creates a satiation-starvation environment for the growth of microorganisms, and further enhances the stability of the particles. Along with shortening of the operation cycle, the system can further complete particle screening, and the low-temperature-resistant aerobic granular sludge with high settleability is reserved.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and specifically to a method for culturing aerobic granular sludge at low temperature. Background Art

[0002] Aerobic granular sludge is considered to be the most promising sewage treatment technology at present. This technology can not only achieve synchronous nitrogen and phosphorus removal, but also minimize energy consumption and floor area. Compared with traditional sewage treatment technologies, aerobic granular sludge can reduce the floor area by 50 - 75%. However, this technology is extremely vulnerable to operating parameters during actual operation. Among them, temperature is the main factor affecting the stable operation of aerobic granular sludge. Research has found that at low temperatures and large temperature fluctuations, it is extremely easy to cause the disintegration of granular sludge, thereby affecting its sewage treatment performance. Researchers believe that when the temperature is below 12 °C, the sewage treatment efficiency of aerobic granular sludge will be inhibited. When the temperature further decreases, the removal rate of nitrogen and phosphorus in sewage will drop by more than 50%, and the granular structure will gradually crack. Therefore, how to overcome the influence of low temperature on aerobic granular sludge is of great significance for promoting the large-scale application of this technology.

[0003] In response to the technical bottleneck faced by aerobic granular sludge at low temperature, existing research still mainly adopts the method of gradually reducing the temperature to enhance the tolerance of granular sludge to low temperature. This will not only greatly prolong the start-up time of the reactor, but also weaken the tolerance of microorganisms to low temperature. Therefore, how to directly cultivate aerobic granular sludge at low temperature is still a major challenge faced by many scholars. Based on the drawbacks of existing cultivation measures, there is an urgent need to develop a cultivation method for low-temperature-tolerant aerobic granular sludge that can directly adapt to low-temperature environments, has strong nitrogen and phosphorus removal performance, stable operation effects, and strong shock resistance to meet the sewage treatment in cold regions of our country. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and propose a method for culturing aerobic granular sludge at low temperature, which can directly cultivate aerobic granular sludge at low temperature.

[0005] The purpose of the present invention is achieved by the following technical solutions: A method for culturing aerobic granular sludge at low temperature, comprising the following steps: S1. Put normal-temperature flocculent sludge into the SBR reactor. S2. Inject simulated wastewater into the SBR reactor for 10 - 20 min, and stir the inside of the SBR reactor while injecting water. S3. Continuously stir the inside of the SBR reactor for 90 - 240 min. S4. While maintaining stirring, aerate the inside of the SBR reactor for 180 - 480 min, and then stop aeration and stirring. S5. Precipitate for 5 - 10 min; S6. Drain water for 5 - 10 min; S7. Take S2 - S6 as one operation cycle and continuously repeat the operation cycle for multiple times. After 50 - 60 days, low - temperature aerobic granular sludge is obtained; In the first S4 step, when aeration is carried out inside the SBR reactor, the dissolved oxygen concentration is 6 - 7 mg / L, and the flow rate of the gas flowmeter is adjusted to 200 - 300 ml / min (to enhance the screening ability of the sludge). In subsequent S4 steps, after the sludge sedimentation performance gradually improves, the gas flow rate is reduced to 150 - 200 ml / min; The temperature of the simulated wastewater is 4 - 5 °C.

[0006] In the startup stage, it is operated in a long - cycle mode with an operation cycle of 10 - 11 h, and subsequently, the operation cycle is gradually reduced to 5 - 6 h.

[0007] The purpose of this method using high - concentration dissolved oxygen (DO) aeration and long - cycle operation mode is to improve the tolerance and adhesion ability of microorganisms to low - temperature environments by enhancing the microbial carbon metabolism ability and extracellular polymer secretion. At the same time, the operation mode combining high - aeration and mechanical stirring can not only generate a large shear force to remove the loose biofilm on the sludge surface, but also enhance the aggregation ability of microorganisms by promoting the occurrence of pili, flagella and quorum sensing among microorganisms. The intermittent operation mode creates a feast - famine environment for the growth of microorganisms, further enhancing the stability of the granules. As the operation cycle shortens, the system will further complete granule screening and retain the low - temperature - tolerant aerobic granular sludge with stronger sedimentation performance.

[0008] In the step S6, the drainage ratio is 30 - 50%.

[0009] In the SBR reactor, MLSS = 4120 - 4457 mg / L, MLVSS = 2218 - 2674 mg / L, f = 0.54 - 0.60, where MLS is the sludge concentration, MLVS is the volatile suspended solid concentration, f is the ratio of MLVSS / MLSS, and the height - to - diameter ratio of the SBR reactor is 1.70 - 1.75.

[0010] The carbon - nitrogen ratio of the simulated wastewater quality is controlled at 5 - 5.5, the influent ammonia - nitrogen concentration is 39 - 43 mg / L, the COD concentration is 200 - 220 mg / L, the total phosphorus concentration is 1.8 - 2.5 mg / L, and 0.3 - 0.35 g / L of sodium bicarbonate is added as an acid - base buffer.

[0011] When the simulated wastewater is injected into the SBR reactor, sodium acetate is used as the carbon source, ammonium chloride is used as the nitrogen source, and potassium dihydrogen phosphate is used as the phosphorus source.

[0012] The stirring rate is 60 - 70 rpm.

[0013] During subsequent operation cycles, when aeration is carried out inside the SBR reactor, the dissolved oxygen concentration is 4 - 6 mg / L.

[0014] The beneficial effects of the present invention are as follows: (1) Provide theoretical support for the successful cultivation of aerobic granular sludge in low-temperature environments. At present, many studies believe that when the temperature is lower than 10 °C, aerobic granular sludge will disintegrate and the nitrogen and phosphorus removal efficiency will decline. However, through the domestication method of the present invention, not only can the domestication of low-temperature activated sludge be successfully achieved, but also its strong nitrogen and phosphorus removal efficiency can be ensured, which is of great significance for the popularization and application of aerobic granular sludge technology.

[0015] (2) During the cultivation process, the cultivation of low-temperature aerobic granular sludge can be achieved without adding low-temperature bacterial agents and flocculants; (3) Compared with traditional activated sludge, low-temperature aerobic granular sludge not only has a high biomass but also has an extremely strong phosphorus removal effect. After cultivation, the sludge biomass increased by 43.33%, and its total phosphorus removal rate exceeded 98%; (4) The removal rates of ammonia nitrogen and total nitrogen by low-temperature aerobic granular sludge exceed 95% and 70% respectively; (5) Compared with aerobic granular sludge at normal temperature, low-temperature aerobic granular sludge has a lower concentration and a longer biological growth cycle, which can significantly shorten the sludge discharge cycle and the sludge discharge volume; (6) Low-temperature aerobic granular sludge can settle rapidly within 5 minutes, and its sedimentation performance has increased by more than 70%; (7) Microorganisms with nitrification, denitrification, and phosphorus-accumulating effects in low-temperature aerobic granular sludge are in a dominant position, and their relative abundances have increased by 341.79%, 202.62%, and 173.59% respectively; (8) The relative abundance of microorganisms with both nitrification and denitrification functions in low-temperature aerobic granular sludge has increased by 62.84%; (9) After cultivation and domestication, the maximum particle size of low-temperature aerobic granular sludge can reach 724.44 μm; (10) The cultivated and domesticated low-temperature aerobic granular sludge can ensure that the sewage reaches the first-class A discharge standard stably at 4 °C. Description of the Drawings

[0016] Figure 1 SEM image of 10 μm scale of low-temperature aerobic granular sludge in Example 1; Figure 2 SEM image of 3 μm scale of low-temperature aerobic granular sludge in Example 1; Figure 3Schematic diagram of the relative abundances of nitrifying bacteria and denitrifying bacteria before and after the domestication of low-temperature aerobic granular sludge in Example 1; Figure 4 Schematic diagram of the relative abundances of heterotrophic nitrifying-denitrifying bacteria before and after the domestication of low-temperature aerobic granular sludge in Example 1; Figure 5 For the influent and effluent NH4 + — N concentrations during the operation of the SBR reactor in Example 1; Figure 6 Schematic diagram of the influent and effluent TN concentrations during the operation of the SBR reactor in Example 1; Figure 7 Schematic diagram of the influent and effluent TP concentrations during the operation of the SBR reactor in Example 1. Detailed implementation manners

[0017] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0018] Herein, it is noted that the orientation concepts of "left", "right", "up", "down", "front", "rear", "inner", and "outer" in the following solutions are all relative directions, and will not be listed one by one here.

[0019] Example 1

[0020] Refer to Figures 1-7 。

[0021] A method for culturing low-temperature aerobic granular sludge, which involves putting normal-temperature flocculent sludge into the interior of an SBR reactor, starting the SBR reactor, and operating the SBR reactor. At this time, in the SBR reactor, MLSS = 4457 mg / L, MLVSS = 2674 mg / L, f = 0.60, where MLSS is the sludge concentration, MLVSS is the volatile suspended solid concentration, f is the MLVSS / MLSS ratio, and the height-diameter ratio of the SBR reactor is 1.70.

[0022] Inject simulated wastewater into the SBR reactor and simultaneously start the internal agitation of the SBR reactor. The duration of wastewater injection is 20 min, which is the influent stage. The carbon-nitrogen ratio of the simulated wastewater quality is controlled at 5.5, the influent ammonia nitrogen concentration is 43 mg / L, the COD concentration is 220 mg / L, the total phosphorus concentration is 2.5 mg / L, and 0.35 g / L sodium bicarbonate is added as an acid-base buffer. Sodium acetate is used as the carbon source, ammonium chloride is used as the nitrogen source, and potassium dihydrogen phosphate is used as the phosphorus source for the influent. After the injection is completed, the internal agitation of the SBR reactor continues for 140 min, which is the aerobic stage. While continuing to maintain the agitation, aeration is carried out inside the SBR reactor for 480 min. When the aeration ends, the agitation is stopped, and the dissolved oxygen concentration during aeration is 6 mg / L, and the flow rate of the gas flowmeter is adjusted to 200 ml / min, which is the anaerobic stage. Then sedimentation is carried out for 10 min, which is the sedimentation stage. After sedimentation, drainage is carried out for 10 min, and the drainage ratio is 30% of the internal volume of the reactor, which is the drainage stage.

[0023] Continue to repeat the operation cycle of the influent stage - aerobic stage - anaerobic stage - sedimentation stage - drainage stage in a cycle. Gradually shorten the aerobic stage to 90 min and the anaerobic stage to 230 min. After 50 days, low-temperature aerobic granular sludge is obtained. In the subsequent operation cycles, when aeration is carried out inside the SBR reactor, the dissolved oxygen concentration is 4 mg / L, and the gas flow rate is 150 ml / min (it should be noted here that if the carbon-nitrogen ratio of the simulated wastewater injected in the influent stage is higher than 50 at this time, the dissolved oxygen concentration is adjusted to 6 mg / L).

[0024] The agitation rate during the agitation of the SBR reactor is 60 rpm.

[0025] Example 2

[0026] A method for culturing low-temperature aerobic granular sludge. Put room-temperature flocculent sludge into the SBR reactor, start the SBR reactor, and the SBR reactor operates. At this time, in the SBR reactor, MLSS = 4400 mg / L, MLVSS = 2500 mg / L, f = 0.57, where MLSS is the sludge concentration, MLVSS is the volatile suspended solid concentration, f is the MLVSS / MLSS ratio, and the height-diameter ratio of the SBR reactor is 1.72.

[0027] Inject simulated wastewater into the SBR reactor and simultaneously start the internal agitation of the SBR reactor. The duration of wastewater injection is 15 minutes, which is the influent stage. The carbon-nitrogen ratio of the simulated wastewater quality is controlled at 5.25, the influent ammonia nitrogen concentration is 40 mg / L, the COD concentration is 210 mg / L, the total phosphorus concentration is 2 mg / L, and 0.32 g / L of sodium bicarbonate is added as an acid-base buffer. The influent uses sodium acetate as the carbon source, ammonium chloride as the nitrogen source, and potassium dihydrogen phosphate as the phosphorus source. After the injection of water is completed, the internal agitation of the SBR reactor continues for 240 minutes, which is the aerobic stage. While continuing to maintain the agitation, aeration is carried out inside the SBR reactor for 380 minutes. When the aeration ends, the agitation is stopped, and the dissolved oxygen concentration during aeration is 6.5 mg / L, and the flow rate of the gas flowmeter is adjusted to 250 ml / min, which is the anaerobic stage. Then sedimentation occurs for 7.5 minutes, which is the sedimentation stage. After sedimentation, drainage is carried out for 7.5 minutes, and the drainage ratio is 40% of the volume of the reactor content, which is the drainage stage.

[0028] Continue to repeat the influent stage - aerobic stage - anaerobic stage - sedimentation stage - drainage stage in a cycle. Gradually shorten the aerobic stage to 120 minutes and the anaerobic stage to 180 minutes. After 55 days, low-temperature aerobic granular sludge is obtained. In subsequent operation cycles, when aeration is carried out inside the SBR reactor, the dissolved oxygen concentration is 5 mg / L, and the gas flow rate is 175 ml / min (here it is stated that if the carbon-nitrogen ratio of the simulated wastewater injected in the influent stage is higher than 50 at this time, the dissolved oxygen concentration is adjusted to 6.5 mg / L).

[0029] The agitation rate during the agitation of the SBR reactor is 65 rpm.

[0030] Example 3

[0031] A method for culturing low-temperature aerobic granular sludge, put room-temperature flocculent sludge into the SBR reactor, start the SBR reactor, and the SBR reactor runs. At this time, in the SBR reactor, MLSS = 4120 mg / L, MLVSS = 2218 mg / L, f = 0.54, where MLSS is the sludge concentration, MLVSS is the volatile suspended solid concentration, f is the ratio of MLVSS / MLSS, and the height-diameter ratio of the SBR reactor is 1.75.

[0032] Inject simulated wastewater into the SBR reactor and simultaneously start the internal stirring of the SBR reactor. The duration of wastewater injection is 10 minutes, which is the influent stage. The carbon-nitrogen ratio of the simulated wastewater quality is controlled at 5, the influent ammonia nitrogen concentration is 39 mg / L, the COD concentration is 200 mg / L, the total phosphorus concentration is 1.8 mg / L, and 0.3 g / L of sodium bicarbonate is added as an acid-base buffer. The influent uses sodium acetate as the carbon source, ammonium chloride as the nitrogen source, and potassium dihydrogen phosphate as the phosphorus source. After the injection is completed, the internal stirring of the SBR reactor continues for 180 minutes, which is the aerobic stage. While continuing to maintain the stirring, the SBR reactor is aerated for 400 minutes. When the aeration ends, the stirring is stopped. The dissolved oxygen concentration during aeration is 7 mg / L, and the flow rate of the gas flowmeter is adjusted to 300 ml / min, which is the anaerobic stage. Then sedimentation occurs for 5 minutes, which is the sedimentation stage. After sedimentation, drainage occurs for 5 minutes, and the drainage ratio is 50% of the reactor volume, which is the drainage stage.

[0033] Continue to repeat the influent stage - aerobic stage - anaerobic stage - sedimentation stage - drainage stage in a cycle. Gradually shorten the aerobic stage to 95 minutes and the anaerobic stage to 185 minutes. After 60 days, low-temperature aerobic granular sludge is obtained. In subsequent operating cycles, when aerating inside the SBR reactor, the dissolved oxygen concentration is 6 mg / L, and the gas flow rate is 200 ml / min (it should be noted here that if the carbon-nitrogen ratio of the simulated wastewater injected during the influent stage is higher than 50 at this time, the dissolved oxygen concentration is adjusted to 7 mg / L).

[0034] The stirring rate during the stirring of the SBR reactor is 70 rpm.

[0035] The above is only the preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications, and environments, and can be changed within the scope of the concept described herein through the above description or the technology or knowledge in related fields. And the changes and alterations made by those skilled in the art that do not depart from the spirit and scope of the present invention should all be within the protection scope of the appended claims of the present invention.

Claims

1. A method for culturing low-temperature aerobic granular sludge, characterized in that, It includes the following steps: S1. Put the normal-temperature flocculent sludge into the SBR reactor; S2. Inject simulated wastewater into the SBR reactor for 10 - 20 min. While injecting water, stir the inside of the SBR reactor; S3. Continuously stir the inside of the SBR reactor for 90 - 240 min; S4. While maintaining stirring, aerate the inside of the SBR reactor for 180 - 480 min, then stop aeration and stirring; S5. Sediment for 5 - 10 min; S6. Drain water for 5 - 10 min; S7. Take S2 - S6 as one operation cycle, continuously repeat the operation cycle for multiple times. After 50 - 60 days, obtain low-temperature aerobic granular sludge; In the first execution of step S4, when aerating the inside of the SBR reactor, the dissolved oxygen concentration is 6 - 7 mg / L; The temperature of the simulated wastewater is 4 - 5 °C; The operation duration of the first cycle is 10 - 11 h, and the operation duration of subsequent cycles is 5 - 6 h.

2. The method for culturing low-temperature aerobic granular sludge according to claim 1, characterized in that: In the said step S6, the drainage ratio is 30 - 50%; 3. A method for culturing low-temperature aerobic granular sludge according to claim 1, characterized in that: In the said SBR reactor, MLSS = 4120 - 4457 mg / L, MLVSS = 2218 - 2674 mg / L, f = 0.54 - 0.60, where MLSS is the sludge concentration, MLVSS is the volatile suspended solid concentration, f is the ratio of MLVSS / MLSS, and the height-diameter ratio of the SBR reactor is 1.70 - 1.

75.

4. A method for culturing low-temperature aerobic granular sludge according to claim 1, characterized in that: The carbon-nitrogen ratio of the said simulated wastewater quality is controlled at 5 - 5.5, the influent ammonia nitrogen concentration is 39 - 43 mg / L, the COD concentration is 200 - 220 mg / L, the total phosphorus concentration is 1.8 - 2.5 mg / L, and 0.3 - 0.35 g / L sodium bicarbonate is added as an acid-base buffer; 5. A method for culturing low-temperature aerobic granular sludge according to claim 1, characterized in that: When injecting the simulated wastewater into the SBR reactor, sodium acetate is used as the carbon source, ammonium chloride is used as the nitrogen source, and potassium dihydrogen phosphate is used as the phosphorus source; 6. The method for culturing low-temperature aerobic granular sludge according to claim 1, wherein: The stirring rate is 60 - 70 rpm; 7. A method for culturing low-temperature aerobic granular sludge according to claim 1, characterized in that: In subsequent operation cycles, when aerating the inside of the SBR reactor, the dissolved oxygen concentration is 4 - 6 mg / L; 8. A method for culturing low-temperature aerobic granular sludge according to claim 1, characterized in that: In the first execution of step S4, the flow rate of the gas flowmeter is adjusted to 200 - 300 ml / min, and in subsequent step S4, the gas flow rate is reduced to 150 - 200 ml / min.

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