A method for cultivating low-temperature aerobic granular sludge

Abstract

The present invention discloses a method for cultivating low-temperature aerobic granular sludge, which relates to the field of sewage treatment technology. The method adopts high-concentration dissolved oxygen (DO) aeration and a long-cycle operation mode. The purpose is to improve the tolerance and adhesion ability of microorganisms to low-temperature environments by enhancing the carbon metabolism ability and extracellular polymer secretion of microorganisms. At the same time, the operation mode combining high aeration with mechanical stirring can not only generate a large shear force to remove loose biofilms on the sludge surface, but also enhance the aggregation ability of microorganisms by promoting the occurrence of pili, flagella and quorum sensing phenomena between microorganisms. The intermittent mode of operation creates a feast-famine environment for microbial growth, further enhancing the stability of the particles. As the operation cycle shortens, the system will further complete the particle screening, retaining low-temperature resistant aerobic granular sludge with strong sedimentation.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a method for cultivating low-temperature aerobic granular sludge. Background Art

[0002] Aerobic granular sludge is considered one of the most promising wastewater treatment technologies. It not only achieves simultaneous nitrogen and phosphorus removal but also minimizes energy consumption and floor space. Compared to traditional wastewater treatment technologies, aerobic granular sludge can reduce floor space requirements by 50–75%. However, in practice, this technology is highly susceptible to operational parameters. Temperature is a major factor affecting the stable operation of aerobic granular sludge. Studies have found that low temperatures and large temperature fluctuations can easily lead to granular sludge disintegration, thus affecting its wastewater treatment performance. Researchers believe that when the temperature drops below 12°C, the wastewater treatment efficiency of aerobic granular sludge is inhibited. As the temperature drops further, its nitrogen and phosphorus removal rate drops by more than 50%, and the granular structure gradually breaks down. Therefore, overcoming the effects of low temperatures on aerobic granular sludge is crucial for promoting the large-scale application of this technology.

[0003] In response to the technical bottlenecks faced by aerobic granular sludge at low temperatures, existing research still mainly adopts a gradual cooling method to enhance the tolerance of granular sludge to low temperatures. This will not only greatly prolong the startup time of the reactor, but also weaken the tolerance of microorganisms to low temperatures. Therefore, how to directly achieve the cultivation of aerobic granular sludge at low temperatures remains a major challenge facing many scholars. Due to the shortcomings of existing cultivation measures, there is an urgent need to develop a low-temperature resistant aerobic granular sludge cultivation method that can directly adapt to low-temperature environments, has strong denitrification and phosphorus removal performance, stable operation results and strong impact resistance to meet the needs of sewage treatment in cold regions of my country. Summary of the Invention

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

[0005] The object of the present invention is achieved through the following technical solution: A method for cultivating low-temperature aerobic granular sludge, comprising the following steps:

[0006] S1. Put the room temperature flocculent sludge into the SBR reactor;

[0007] S2, injecting simulated wastewater into the SBR reactor for 10-20 minutes, stirring the inside of the SBR reactor while injecting water;

[0008] S3, SBR reactor internal stirring is continued for 90~240min;

[0009] S4. Keep stirring and aerate the interior of the SBR reactor for 180-480 min, then stop aeration and stirring;

[0010] S5, sedimentation for 5-10 minutes;

[0011] S6, drain for 5-10 minutes;

[0012] S7, taking S2 to S6 as one operation cycle, repeat the operation cycle several times until 50 to 60 days later, low-temperature aerobic granular sludge is obtained;

[0013] In the first S4 step, when aeration is performed inside the SBR reactor, the dissolved oxygen concentration is 6-7 mg / L, and the gas flow meter flow rate is adjusted to 200-300 ml / min (to enhance the sludge screening ability). In the subsequent S4 step, after the sludge settling property gradually improves, the gas flow rate is reduced to 150-200 ml / min;

[0014] The temperature of the simulated wastewater is 4-5°C.

[0015] The startup phase adopts long-cycle mode with an operating cycle of 10 to 11 hours, and the operating cycle will be gradually shortened to 5 to 6 hours.

[0016] This method utilizes high-concentration dissolved oxygen (DO) aeration and long-cycle operation to enhance microbial carbon metabolism and extracellular polymer secretion, thereby improving their tolerance and adhesion to low-temperature environments. Furthermore, this combination of high aeration and mechanical agitation not only generates significant shear forces to remove loose biofilms from the sludge surface but also enhances microbial aggregation by promoting pili, flagella, and quorum sensing among microorganisms. The intermittent operation creates a feast-famine environment for microbial growth, further enhancing granule stability. As the operation cycle shortens, the system further refines granule separation, retaining highly settleable, low-temperature-resistant, aerobic granules.

[0017] In step S6, the drainage ratio is 30-50%.

[0018] In the SBR reactor, MLSS=4120~4457 mg / L, MLVSS=2218~2674 mg / L, f=0.54~0.60, wherein MLSS is the sludge concentration, MLVSS is the volatile suspended solids concentration, f is the MLVSS / MLSS ratio, and the height-to-diameter ratio of the SBR reactor is 1.70~1.75.

[0019] The carbon-nitrogen ratio of the simulated wastewater 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.

[0020] When the simulated wastewater is injected into the SBR reactor, sodium acetate is used as a carbon source, ammonium chloride is used as a nitrogen source, and potassium dihydrogen phosphate is used as a phosphorus source.

[0021] The stirring rate is 60-70 rpm.

[0022] In the subsequent operation cycle, when aeration was performed inside the SBR reactor, the dissolved oxygen concentration was 4~6 mg / L.

[0023] The beneficial effects of the present invention are:

[0024] (1) Provide theoretical support for the successful cultivation of aerobic granular sludge in low-temperature environments. Currently, many studies have shown that aerobic granular sludge will disintegrate and its nitrogen and phosphorus removal efficiency will decrease when the temperature is below 10°C. The acclimation method of the present invention can not only successfully achieve the acclimation of low-temperature activated sludge, but also ensure its strong nitrogen and phosphorus removal efficiency, which is of great significance to the promotion and application of aerobic granular sludge technology.

[0025] (2) Low-temperature aerobic granular sludge can be cultivated without adding low-temperature bacteria and flocculants during the cultivation process;

[0026] (3) Compared with traditional activated sludge, low-temperature aerobic granular sludge not only has a high biomass, but also has a strong phosphorus removal effect. After cultivation, the sludge biomass increased by 43.33%, and its total phosphorus removal rate exceeded 98%;

[0027] (4) The removal rates of ammonia nitrogen and total nitrogen by low-temperature aerobic granular sludge exceed 95% and 70%, respectively;

[0028] (5) Compared with normal temperature aerobic granular sludge, low temperature aerobic granular sludge has lower concentration and longer biological growth cycle, which can greatly shorten the sludge discharge cycle and sludge discharge volume;

[0029] (6) Low-temperature aerobic granular sludge can settle quickly within 5 minutes, and its settling performance is improved by more than 70%;

[0030] (7) Microorganisms with nitrification, denitrification and phosphorus accumulation effects were dominant in low-temperature aerobic granular sludge, and their relative abundance increased by 341.79%, 202.62% and 173.59%, respectively;

[0031] (8) The relative abundance of microorganisms with both nitrification and denitrification functions in low-temperature aerobic granular sludge increased by 62.84%;

[0032] (9) After cultivation and acclimation, the particle size of low-temperature aerobic granular sludge can reach up to 724.44 μm;

[0033] (10) The low-temperature aerobic granular sludge after cultivation and acclimatization can ensure that the wastewater can stably reach the Class A discharge standard at 4°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a 10 μm SEM image of the low-temperature aerobic granular sludge in Example 1;

[0035] Figure 2 This is a 3 μm scale SEM image of the low-temperature aerobic granular sludge in Example 1;

[0036] Figure 3 This is a schematic diagram of the relative abundance of nitrifying bacteria and denitrifying bacteria before and after acclimation of low-temperature aerobic granular sludge in Example 1;

[0037] Figure 4 Schematic diagram of the relative abundance of heterotrophic nitrification-denitrification bacteria before and after acclimation of low-temperature aerobic granular sludge in Example 1;

[0038] Figure 5 The influent and effluent NH4 in the SBR reactor operation process in Example 1 + — Schematic diagram of N concentration;

[0039] Figure 6 Schematic diagram of TN concentrations of influent and effluent during the operation of the SBR reactor in Example 1;

[0040] Figure 7 Schematic diagram of the TP concentrations of the inlet and outlet water during the operation of the SBR reactor in Example 1. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

[0042] It is to be noted that the directions of "left", "right", "up", "down", "front", "back", "inside" and "outside" in the following schemes are all relative directions and are not listed here one by one.

[0043] Example 1

[0044] refer to Figure 1-Figure 7 .

[0045] A method for cultivating low-temperature aerobic granular sludge comprises introducing ambient temperature flocculent sludge into a SBR reactor, starting the SBR reactor, and operating the SBR reactor. At this point, the MLSS in the SBR reactor is 4457 mg / L, the MLVSS is 2674 mg / L, and f is 0.60, where MLSS is the sludge concentration, MLVSS is the volatile suspended solids concentration, and f is the MLVSS / MLSS ratio. The height-to-diameter ratio of the SBR reactor is 1.70.

[0046] Simulated wastewater was injected into the SBR reactor while internal agitation was activated. Wastewater injection lasted for 20 minutes, marking the inlet stage. The carbon-nitrogen ratio of the simulated wastewater was controlled at 5.5, with an inlet ammonia nitrogen concentration of 43 mg / L, a COD concentration of 220 mg / L, and a total phosphorus concentration of 2.5 mg / L. 0.35 g / L of sodium bicarbonate was added as an acid-base buffer. The inlet water contained sodium acetate as the carbon source, ammonium chloride as the nitrogen source, and potassium dihydrogen phosphate as the phosphorus source. After injection, the SBR reactor was stirred continuously for 140 minutes, marking the anaerobic stage. While stirring was maintained, the SBR reactor was aerated for 480 minutes. Upon completion of aeration, stirring was stopped. The dissolved oxygen concentration during aeration was maintained at 6 mg / L, and the gas flowmeter was set at a flow rate of 200 ml / min, marking the aerobic stage. The reactor then settled for 10 minutes, marking the sedimentation stage. After sedimentation, the reactor was drained for 10 minutes, with the drainage ratio reaching 30% of the reactor volume, marking the draining stage.

[0047] The cycle of inlet phase, anaerobic phase, aerobic phase, sedimentation phase, and drainage phase was repeated repeatedly. The anaerobic phase was gradually shortened to 90 minutes, and the aerobic phase to 230 minutes. After 50 days of this process, low-temperature aerobic granular sludge was obtained. During subsequent cycles, aeration within the SBR reactor was maintained at a dissolved oxygen concentration of 4 mg / L and a medium gas flow rate of 150 ml / min. (Note: If the carbon-nitrogen ratio of the simulated wastewater injected during the inlet phase is higher than 50, the dissolved oxygen concentration is adjusted to 6 mg / L.)

[0048] The stirring rate of the SBR reactor was 60 rpm.

[0049] Example 2

[0050] A method for cultivating low-temperature aerobic granular sludge comprises introducing ambient temperature flocculent sludge into a SBR reactor, starting the SBR reactor, and operating the SBR reactor. At this point, the SBR reactor has MLSS = 4400 mg / L, MLVSS = 2500 mg / L, and f = 0.57, where MLSS is the sludge concentration, MLVSS is the volatile suspended solids concentration, and f is the MLVSS / MLSS ratio. The SBR reactor has a height-to-diameter ratio of 1.72.

[0051] Simulated wastewater was injected into the SBR reactor while internal agitation was activated. Wastewater injection lasted for 15 minutes, marking the inlet stage. The simulated wastewater had a carbon-nitrogen ratio of 5.25, an inlet ammonia nitrogen concentration of 40 mg / L, a COD concentration of 210 mg / L, and a total phosphorus concentration of 2 mg / L. 0.32 g / L of sodium bicarbonate was added as an acid-base buffer. The inlet water contained sodium acetate as the carbon source, ammonium chloride as the nitrogen source, and potassium dihydrogen phosphate as the phosphorus source. After injection, the SBR reactor was stirred continuously for 240 minutes, marking the anaerobic stage. While stirring was maintained, the SBR reactor was aerated for 380 minutes. Upon completion of aeration, agitation was stopped. Aeration maintained a dissolved oxygen concentration of 6.5 mg / L, and the gas flowmeter was set at a flow rate of 250 ml / min, marking the aerobic stage. This was followed by 7.5 minutes of sedimentation, marking the sedimentation stage. After sedimentation, drainage was performed for 7.5 minutes, with the drainage ratio reaching 40% of the reactor volume, marking the drainage stage.

[0052] The cycle of inflow phase, anaerobic phase, aerobic phase, sedimentation phase, and drainage phase was repeated repeatedly. The anaerobic phase was gradually shortened to 120 minutes, and the aerobic phase to 180 minutes. After 55 days of continuous operation, low-temperature aerobic granular sludge was obtained. During subsequent operation cycles, aeration within the SBR reactor was performed at a dissolved oxygen concentration of 5 mg / L and a gas flow rate of 175 ml / min. (Note: If the carbon-nitrogen ratio of the simulated wastewater injected during the inflow phase is higher than 50, the dissolved oxygen concentration is adjusted to 6.5 mg / L.)

[0053] The stirring rate of the SBR reactor during stirring was 65 rpm.

[0054] Example 3

[0055] A method for cultivating low-temperature aerobic granular sludge comprises introducing ambient temperature flocculent sludge into a SBR reactor, starting the SBR reactor, and operating the SBR reactor. At this point, the SBR reactor has MLSS = 4120 mg / L, MLVSS = 2218 mg / L, and f = 0.54, where MLSS is the sludge concentration, MLVSS is the volatile suspended solids concentration, and f is the MLVSS / MLSS ratio. The SBR reactor has a height-to-diameter ratio of 1.75.

[0056] Simulated wastewater was injected into the SBR reactor while internal agitation was activated. Wastewater injection lasted for 10 minutes, marking the inlet stage. The simulated wastewater had a carbon-to-nitrogen ratio of 5, an inlet ammonia nitrogen concentration of 39 mg / L, a COD concentration of 200 mg / L, and a total phosphorus concentration of 1.8 mg / L. 0.3 g / L of sodium bicarbonate was added as an acid-base buffer. The inlet water contained sodium acetate as the carbon source, ammonium chloride as the nitrogen source, and potassium dihydrogen phosphate as the phosphorus source. After injection, the SBR reactor was stirred continuously for 180 minutes, marking the anaerobic stage. While stirring was maintained, the SBR reactor was aerated for 400 minutes. Upon completion of aeration, stirring was stopped. The dissolved oxygen concentration during aeration was maintained at 7 mg / L, and the gas flowmeter was set to a flow rate of 300 ml / min, marking the aerobic stage. The solution then settled for 5 minutes, marking the sedimentation stage. After sedimentation, the solution was drained for 5 minutes, with the drainage ratio reaching 50% of the reactor volume, marking the drainage stage.

[0057] The cycle of inflow phase, anaerobic phase, aerobic phase, sedimentation phase, and drainage phase was repeated repeatedly. The anaerobic phase was gradually shortened to 95 minutes, and the aerobic phase to 185 minutes. After 60 days of continuous operation, low-temperature aerobic granular sludge was obtained. During subsequent operation cycles, aeration within the SBR reactor was performed at a dissolved oxygen concentration of 6 mg / L and a gas flow rate of 200 ml / min. (Note: If the carbon-nitrogen ratio of the simulated wastewater injected during the inflow phase is higher than 50, the dissolved oxygen concentration is adjusted to 7 mg / L.)

[0058] The stirring rate of the SBR reactor during stirring was 70 rpm.

[0059] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein by utilizing the above description or the techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. A method for cultivating low-temperature aerobic granular sludge, characterized in that: The following steps are involved: S1. Put the room temperature flocculent sludge into the SBR reactor; S2, injecting simulated wastewater into the SBR reactor for 10-20 minutes, stirring the inside of the SBR reactor at the same time; S3, SBR reactor internal stirring is continued for 90~240min; S4. Keep stirring and aerate the interior of the SBR reactor for 180-480 min, then stop aeration and stirring; S5, sedimentation for 5-10 minutes; S6, drain for 5-10 minutes; S7, taking S2 to S6 as one operation cycle, repeat the operation cycle several times until 50 to 60 days later, low-temperature aerobic granular sludge is obtained; In the first step S4, when aeration is performed inside the SBR reactor, the dissolved oxygen concentration is 6~7 mg / L; The temperature of simulated wastewater is 4~5℃; The first cycle runs for 10 to 11 hours, and subsequent cycles run for 5 to 6 hours. The carbon-nitrogen ratio of the simulated wastewater 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; In the subsequent operation cycle, when aeration was performed inside the SBR reactor, the dissolved oxygen concentration was 4~6 mg / L.

2. The method for cultivating low-temperature aerobic granular sludge according to claim 1, characterized in that: In step S6, the drainage ratio is 30-50%.

3. The method for cultivating low-temperature aerobic granular sludge according to claim 1, characterized in that: In the SBR reactor, MLSS=4120~4457 mg / L, MLVSS=2218~2674 mg / L, f=0.54~0.60, wherein MLSS is the sludge concentration, MLVSS is the volatile suspended solids concentration, f is the MLVSS / MLSS ratio, and the height-to-diameter ratio of the SBR reactor is 1.70~1.

75.

4. The method for cultivating low-temperature aerobic granular sludge according to claim 1, characterized in that: When the simulated wastewater is injected into the SBR reactor, sodium acetate is used as a carbon source, ammonium chloride is used as a nitrogen source, and potassium dihydrogen phosphate is used as a phosphorus source.

5. The method for cultivating low-temperature aerobic granular sludge according to claim 1, characterized in that: The stirring rate is 60-70 rpm.

6. The method for cultivating low-temperature aerobic granular sludge according to claim 1, characterized in that: In the first S4 step, the gas flow meter flow rate is adjusted to 200-300 ml / min, and the gas flow rate is reduced to 150-200 ml / min in subsequent S4 steps.

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