Method and device for cultivating strong alkali-resistant aerobic denitrification granular sludge

Abstract

The application discloses a strong alkali-resistant aerobic denitrification granular sludge cultivation method and device. The method solves the problems of low treatment efficiency, complex operation condition, high operation cost, and difficulty of traditional aerobic denitrification bacteria in gathering in a reactor when a conventional biological denitrification process is used to treat strong alkali high-concentration nitric acid nitrogen wastewater. The strong alkali-resistant aerobic denitrification granular sludge has the characteristics of high nitric acid nitrogen removal efficiency, simple operation, high nitrogen removal efficiency, low operation cost, low capital cost, and stable treatment effect.

Description

Technical Field

[0001] This invention relates to a method and apparatus for cultivating highly alkali-resistant aerobic denitrifying granular sludge. It belongs to the field of wastewater treatment technology. Background Technology

[0002] Biological denitrification is a commonly used method for removing nitrogen from wastewater. Traditional biological denitrification technologies suffer from problems such as large plant area and high treatment costs because the nitrification and denitrification processes are carried out in two separate reaction units.

[0003] Biological denitrification often leads to poor sludge settling performance in the treatment of high-concentration nitrate nitrogen wastewater due to the large amount of nitrogen gas generated during denitrification. This necessitates measures such as short-term air stripping to address this issue. Furthermore, denitrification is frequently accompanied by pH increases, while the optimal pH range for denitrifying microorganisms is 6.5-7.5. When the pH of the reaction system deviates from this range, the removal efficiency decreases. This problem is particularly pronounced in the treatment of high-pH, high-concentration nitrate nitrogen wastewater. Under high pH conditions, sludge flocs disintegrate, resulting in poor sludge settling and reduced sludge activity. Although adjusting the influent pH by adding acid can solve these problems, it increases operating costs and complexity. Moreover, many wastewaters contain not only nitrate nitrogen but also large amounts of ammonia nitrogen. Such wastewater requires an aerobic process to convert ammonia nitrogen to nitrate nitrogen, followed by an anoxic denitrification process for further nitrogen removal. This inevitably increases wastewater treatment infrastructure and operating costs.

[0004] Aerobic denitrification technology makes it possible to achieve nitrification and denitrification within the same structure. This technology reduces both infrastructure and operating costs, making it a focus of attention. Various aerobic denitrifying bacteria have been screened, and extensive research has been conducted on the factors influencing their aerobic denitrification efficiency and denitrification mechanisms. However, in practical applications, aerobic denitrifying bacteria often suffer significant losses, preventing them from remaining in the treatment system and making it difficult to maintain treatment effectiveness. These problems are particularly prominent in the treatment of highly alkaline wastewater.

[0005] Existing technologies typically employ methods that immobilize aerobic denitrifying bacteria to form a biofilm in order to address the problem of aerobic denitrifying bacteria loss. However, this method suffers from slow aerobic denitrification biofilm formation and biofilm disintegration due to the inability of denitrifying bacteria to adapt to a strongly alkaline environment.

[0006] CN102583722A discloses a method for immobilizing and cultivating aerobic granular sludge. The method involves first immobilizing and cultivating various microorganisms in activated sludge to obtain initial seed sludge, and then adding a flocculant and / or dominant bacterial species to promote the further rapid growth of the granules. In the target wastewater, aerobic granular sludge with high activity and good tolerance to load fluctuations can be successfully cultivated in a short period of time.

[0007] Currently, extensive research is being conducted on the formation of aerobic granular sludge, focusing on reactor structure, substrate type, and control conditions. Patent CN101941760A discloses an apparatus for cultivating aerobic granular sludge and its proprietary reactor; patent CN101948168A discloses a method for cultivating aerobic granular sludge using a step-by-step influent mode; and CN102583721A discloses a method for cultivating aerobic granular sludge resistant to load fluctuations in low-concentration wastewater. However, these processes either have drawbacks such as excessively long cultivation times (e.g., 50-70 days, or even hundreds of days), or require reactors with special structures to cultivate aerobic granular sludge, and, most importantly, have limited nitrogen removal capacity under aerobic conditions.

[0008] To improve the nitrogen removal performance of aerobic granular sludge under aerobic conditions, researchers have attempted to couple granular sludge technology with aerobic denitrification technology. CN101811772A discloses a wastewater treatment method using aerobic denitrification with granular sludge, employing wastewater treatment plant sludge as inoculum, cultivating 3-8 mm granular sludge in 98 days, achieving a 99% nitrate nitrogen removal rate after 12 hours. CN101928067 discloses a method for cultivating aerobic denitrifying granular sludge, selecting one or more types of aerobic flocculent sludge, anaerobic flocculent sludge, or anaerobic granular sludge and loading them into an upflow aerobic sludge bed reactor equipped with a three-phase separator. The disclosed aerobic granular sludge and aerobic denitrifying granular sludge can only be used to treat neutral and weakly alkaline wastewater, with poor treatment effects on strongly alkaline, high-nitrogen wastewater, and suffers from problems such as long cultivation times and low nitrogen removal efficiency. Therefore, seeking rapid granulation and stable operation methods for aerobic sludge under strongly alkaline conditions is of great significance for the treatment of strongly alkaline nitrogenous wastewater. Summary of the Invention

[0009] This invention addresses the problems of low treatment efficiency, complex control conditions, and high operating costs in the treatment of highly alkaline, high-concentration nitrate nitrogen wastewater using existing biotechnology, as well as the difficulty in the aggregation of traditional aerobic denitrifying bacteria within the reactor. It utilizes the strong alkali tolerance and self-aggregation characteristics of aerobic denitrifying bacteria, especially under highly alkaline conditions, to further increase the secretion of extracellular polymers to cope with the adverse effects of the alkaline environment, thereby promoting the aggregation of microorganisms. Therefore, a novel method for cultivating highly alkaline aerobic denitrifying granular sludge and an apparatus for implementing this method are proposed.

[0010] A method for cultivating strongly alkaline aerobic denitrifying granular sludge involves first cultivating flocculent sludge with a concentration of 300-500 mg / L in an acclimation reactor for 10-20 days under strongly alkaline conditions, controlling the dissolved oxygen in the reactor at 2-4 mg / L, until the sludge concentration increases to over 1000 mg / L. Simultaneously, wastewater with a pH of 9-11 is aerated in air for 10-20 hours daily, twice a day, with a water exchange rate of 20%-30% each time, for 10-20 days. Subsequently, the acclimated sludge and aerated microorganisms are transferred to a wastewater treatment reactor. The influent ratio is controlled at 30%-60%, the dissolved oxygen in the wastewater treatment reactor is 4-6 mg / L, and the ratio of organic matter to nitrate nitrogen in the influent is 4-8:1. The operating mode of the wastewater treatment reactor is controlled as follows: influent 1-5 minutes, idle for 34-30 minutes, mixed-intensity aeration for 290-318 minutes, sedimentation for 2-30 minutes, and effluent discharge for 5 minutes.

[0011] The sludge contains the denitrifying bacteria, which are Pseudomonas.

[0012] The strongly alkaline conditions refer to a pH value of 8.0-11.0, more preferably 9-11, and most preferably 10-10.5.

[0013] When the influent C / N ratio is 6-15, pH is 9.0-11.0, initial nitrate nitrogen concentration is 100-220 mg / L, and temperature is 15-25℃, the removal rate of nitrate nitrogen and total nitrogen reaches over 95%, the relative abundance of aerobic denitrifying bacteria is over 65%, and the SVI value decreases to below 40 ml / g within 30-50 days, with sludge particle size reaching over 200 μm.

[0014] The wastewater mainly contains 500-1000 mg / L of organic matter, 100-300 mg / L of nitrate nitrogen, 10-50 mg / L of ammonia nitrogen, 10-30 mg / L of phosphate, and has a pH value of 9-11.

[0015] The mixed intensity aeration is operated at low gas volume for 10-40 minutes and at high gas volume for 250-308 minutes; the low gas volume is defined as a dissolved oxygen concentration of 1-2 mg / L; and the high gas volume is defined as a dissolved oxygen concentration of 6-8 mg / L.

[0016] The wastewater treatment reactor includes a circular cylinder (15), a third conical cylinder (14), a first conical cylinder (8), and a second conical cylinder (9), an aeration sand head (12), a first gas flow meter (6) and a second gas flow meter (7), a first electric valve (2) and a second electric valve (3), a first time controller (4), a second time controller (5), a fixed plate (16), an air compressor (1), and an outlet (17); the circular cylinder (15) and the conical cylinder (14) are connected by flanges, the fixed plate (16) and the circular cylinder (15) are fixedly connected by adhesive, and the first gas flow meter (6) and the second gas flow meter (7) are threadedly connected to the fixed plate (16); the first gas flow meter (6) The first electric valve (2) is connected to the first electric valve (2), which is controlled by the first time controller (4) to open or close; the second gas flow meter (7) is connected to the second electric valve (3), which is controlled by the second time controller (5) to open or close; the gas compressor (1) is connected to the first electric valve (2) and the second electric valve (3); the circular cylinder (15) is provided with a first conical cylinder (8), a second conical cylinder (9) and an aeration sand head (12), and the first conical cylinder (8) and the second conical cylinder (9) are fixed on the circular cylinder (15); the side of the circular cylinder (15) is provided with a sampling port (11) and a water outlet (17); the lower part of the third conical cylinder (14) is provided with a control valve (13).

[0017] The height-to-diameter ratio of the cylindrical body (15) is 2:1-4:1, more preferably 2:1-3:1.

[0018] The height-to-diameter ratio of the wastewater treatment reactor is 3:1-8:1, preferably 4:1-6:1.

[0019] The specific operation process is as follows: the wastewater enters the reaction cylinder (15). First, according to the pre-set aeration conditions, the first time controller (4) is turned on and the reactor runs at a low aeration intensity for 40-10 minutes. Then the first time controller (4) is turned off. During this process, dissolved oxygen and shearing action are provided by the aeration sand head (12). Next, the second time controller (5) is turned on and the reactor runs at a high aeration intensity for 250-308 minutes. Then the second time controller (5) is turned off. Then the sludge in the reactor is in a settling state, and the sludge and wastewater are separated in the reaction cylinder (15) by means of the conical cylinder (9). Finally, the wastewater is discharged at the outlet (17) of the reaction cylinder (15).

[0020] This method features high nitrate nitrogen removal efficiency, simple operation, high nitrogen removal efficiency, low operating cost, and low infrastructure cost. It can efficiently remove nitrate nitrogen from wastewater under aerobic conditions and can also remove nitrate nitrogen under anoxic conditions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of an aerobic denitrification granular sludge reactor, where: 1. Air compressor; 2. First electric valve; 3. Second electric valve; 4. First time controller; 5. Second time controller; 6. First gas flow meter; 7. Second gas flow meter; 8. First conical cylinder; 9. Second conical cylinder; 10. Sampling tube; 11. Sampling port; 12. Aeration sand head; 13. Control valve; 14. Third conical cylinder; 15. Circular cylinder; 16. Fixing plate; 17. Outlet. Detailed Implementation

[0022] Example 1

[0023] A method for cultivating strongly alkaline aerobic denitrification granular sludge: First, under strongly alkaline conditions (pH = 8.0-11.0), flocculent sludge with a concentration of 300-500 mg / L is cultivated and acclimated for 10-20 days in a reactor with an influent wastewater pH of 9-11 and a height-to-diameter ratio of 8:1, while controlling the dissolved oxygen in the reactor at 2-4 mg / L, until the sludge concentration increases to over 1000 mg / L; simultaneously, wastewater with a pH of around 10 is aerated in the air for 10-20 hours daily. Twice daily, with a water exchange rate of 20%-30% each time, the process lasts 10-20 days. Subsequently, the acclimated sludge and aerated, enriched microorganisms are transferred to a wastewater reactor. The influent ratio is controlled at 30%-60%, dissolved oxygen in the reactor is 4-6 mg / L, and the ratio of organic matter to nitrate nitrogen in the influent is 4-8:1. The reactor operation mode is controlled as follows: 1-5 minutes of influent, 34-30 minutes of idle time, 290-318 minutes of mixed-intensity aeration, 30-2 minutes of sedimentation, and 5 minutes of effluent discharge. When the influent C / N ratio is 6-15, pH is 9.0-11.0, initial nitrate nitrogen concentration is 100-220 mg / L, and temperature is 15-25℃, the nitrate nitrogen and total nitrogen removal rates reach over 95%, the relative abundance of aerobic denitrifying bacteria is over 65%, and the SVI value decreases to below 40 ml / g within 30-50 days, with sludge particle size reaching over 200 μm. The wastewater mainly contains 500-1000 mg / L of organic matter, 100-300 mg / L of nitrate nitrogen, 10-50 mg / L of ammonia nitrogen, and 10-30 mg / L of phosphate, with a pH of 9-11. The mixed-intensity aeration operates at a low gas volume (dissolved oxygen concentration of 1-2 mg / L) for 40-10 minutes and at a high gas volume (dissolved oxygen concentration of 6-8 mg / L) for 250-308 minutes.

[0024] The wastewater treatment reactor includes a circular cylinder (15), a third conical cylinder (14), a first conical cylinder (8), a second conical cylinder (9), an aeration sand head (12), a first gas flow meter (6), a second gas flow meter (7), a first electric valve (2), a second electric valve (3), a first time controller (4), a second time controller (5), a fixing plate (16), an air compressor (1), and an outlet (17); the circular cylinder (15) and the conical cylinder (14) are connected by flanges, and the fixing plate (16) and the circular cylinder (15) are fixedly connected by adhesive. The first gas flow meter (6) and the second gas flow meter (7) are... The first gas flow meter (6) is connected to the fixed plate (16) by threads; the first electric valve (2) is connected to the first electric valve (2), which is controlled by the first time controller (4); the second gas flow meter (7) is connected to the second electric valve (3), which is controlled by the second time controller (5); the gas compressor (1) is connected to the first electric valve (2) and the second electric valve (3); the circular cylinder (15) is provided with a first conical cylinder (8), a second conical cylinder (9) and an aeration sand head (12), and the first conical cylinder (8) and the second conical cylinder (9) are fixed on the circular cylinder (15). The circular cylinder (15) is provided with a sampling port (11) and a water outlet (17) on its side. The third conical cylinder (14) is provided with a control valve (13) at its lower part.

[0025] The specific operation process is as follows: the wastewater enters the reaction cylinder (15). First, according to the pre-set aeration conditions, the first time controller (4) is turned on, and the reactor runs at a low aeration intensity for 40-10 minutes. Then, the first time controller (4) is turned off. During this process, dissolved oxygen and shearing action are provided by the aeration sand head (12). Next, the second time controller (5) is turned on, and the reactor runs at a high aeration intensity for 250-308 minutes. Then, the second time controller (5) is turned off. Then, the sludge in the reactor is in a settling state, and the sludge and wastewater are separated in the reaction cylinder (15) by means of the conical cylinder (9). Finally, the wastewater is discharged at the outlet (17) of the reaction cylinder (15). The aerobic denitrification granular sludge has been operating stably for more than 60 days, the nitrate nitrogen removal rate is stable at more than 95%, and the particle size of the granular sludge is more than 0.2 mm.

[0026] Example 2

[0027] The aeration sand head is placed inside the first conical cylinder (8) and located above the second conical cylinder (9). This arrangement helps to increase gas shear force and promote gas and liquid separation, allowing the alkali-resistant aerobic denitrification granular sludge to form granules within 40 days. Other processes are the same as in Example 1. The aerobic denitrification granular sludge operates stably for more than 60 days, with a nitrate nitrogen removal rate of more than 96% and a granular sludge particle size of more than 0.2 mm.

[0028] Comparative Example 1

[0029] The implementation steps were the same as in Example 1, except that the reactor was started under neutral pH conditions (pH 6-8). The results showed that the granular sludge in the reactor operated under neutral conditions disintegrated.

[0030] Comparative Example 2

[0031] The implementation steps were the same as in Example 1, except that the reactor was a conventional reactor. The results showed that the granular sludge in the reactor operating under neutral conditions disintegrated after 26 days.

[0032] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined by the present invention, and all such modifications and additions should fall within the protection scope of the present invention.

Claims

1. A method for cultivating strongly alkaline aerobic denitrifying granular sludge, characterized in that, First, under strongly alkaline conditions, flocculent sludge with a concentration of 300-500 mg / L is cultivated and acclimated in an acclimation reactor for 10-20 days, with dissolved oxygen controlled at 2-4 mg / L, until the sludge concentration increases to over 1000 mg / L. Simultaneously, wastewater with a pH of 9-11 is aerated in air for 10-20 hours daily, twice a day, with a water exchange rate of 20%-30% each time, for 10-20 days. Then, the acclimated sludge and aerated microorganisms are transferred to a wastewater treatment reactor. The influent ratio is controlled at 30%-60%, dissolved oxygen in the reactor is 4-6 mg / L, and the ratio of organic matter to nitrate nitrogen in the influent is 4-8:

1. The operating mode of the wastewater treatment reactor is controlled as follows: influent 1-5 minutes, idle 34-30 minutes, mixed-intensity aeration 290-318 minutes, sedimentation 30-50 minutes, and effluent discharge 5-10 minutes. The mixed intensity aeration is operated at low gas volume for 10-40 minutes and at high gas volume for 250-308 minutes; the low gas volume is defined as a dissolved oxygen concentration of 1-2 mg / L; and the high gas volume is defined as a dissolved oxygen concentration of 6-8 mg / L.

2. The method as described in claim 1, characterized in that... The sludge contains denitrifying bacteria, which are Pseudomonas.

3. The method as described in claim 1, characterized in that... The strongly alkaline conditions refer to a pH value of 8.0-11.

0.

4. The method as described in claim 3, characterized in that... The strongly alkaline conditions refer to a pH value of 10-10.

5.

5. The method as described in claim 1, characterized in that... When the influent C / N ratio is 6-15, the pH is 9.0-11.0, the initial nitrate nitrogen concentration is 100-220 mg / L, and the temperature is 15-25℃, the removal rates of nitrate nitrogen and total nitrogen reach over 95%, the relative abundance of aerobic denitrifying bacteria is over 65%, and the SVI value decreases to below 40 ml / g within 30-50 days, with the sludge particle size reaching over 200 μm.

6. The method as described in claim 1, characterized in that... The wastewater mainly contains 500-1000 mg / L of organic matter, 100-300 mg / L of nitrate nitrogen, 10-50 mg / L of ammonia nitrogen, 10-30 mg / L of phosphate, and has a pH value of 9-11.

7. The method as described in claim 1, characterized in that... The wastewater treatment reactor includes a cylindrical body (15), a third conical body (14), a first conical body (8) and a second conical body (9), an aeration sand head (12), a first gas flow meter (6) and a second gas flow meter (7), a first electric valve (2) and a second electric valve (3), a first time controller (4), a second time controller (5), a fixed plate (16), an air compressor (1), and an outlet (17); the cylindrical body (15) and the third conical body (14) are connected by flanges, the fixed plate (16) and the cylindrical body (15) are fixedly connected by adhesive, and the first gas flow meter (6) and the second gas flow meter (7) are threaded to the fixed plate (16); the first gas flow meter (6) The first electric valve (2) is connected to the second electric flow meter (7) and the second electric valve (3), which is controlled by the first time controller (4) to open or close. The second electric flow meter (7) is connected to the second electric valve (3), which is controlled by the second time controller (5) to open or close. The air compressor (1) is connected to the first electric valve (2) and the second electric valve (3). The circular cylinder (15) is provided with a first conical cylinder (8), a second conical cylinder (9) and an aeration sand head (12), which are fixed on the circular cylinder (15). The circular cylinder (15) is provided with a sampling port (11) and a water outlet (17) on its side. The third conical cylinder (14) is provided with a control valve (13) at its lower part.

8. The method as described in claim 7, characterized in that The height-to-diameter ratio of the cylindrical body (15) is 2:1-4:

1.

9. The method as described in claim 8, characterized in that... The height-to-diameter ratio of the cylindrical body (15) is 2:1-3:

1.

10. The method as described in claim 7, characterized in that... The height-to-diameter ratio of the wastewater treatment reactor is 3:1-8:

1.

11. The method as described in claim 10, characterized in that... The height-to-diameter ratio of the wastewater treatment reactor is 4:1-6:1.

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