A device and method for realizing denitrification of an AOA process based on super-long anoxic retention time

Abstract

The application discloses a device and method for realizing denitrification of AOA process based on super-long anoxic retention time, and belongs to the field of sewage biological treatment. The anoxic retention time is regarded as super-long anoxic retention time when the anoxic retention time is 16 hours or above. The method is to store part of organic matters in the influent as internal carbon source in an anaerobic stage, then nitrite produced by short-cut nitrification in an aerobic stage enters an anoxic stage, then under the condition of super-long anoxic reaction time, external carbon source is used for external denitrification by external denitrifying bacteria, and then internal carbon source stored by internal denitrifying bacteria is used for internal denitrification to realize denitrification. Due to the super-long anoxic reaction time, sludge fermentation may occur in the system, and small-molecule organic matters produced by fermentation can also be used for denitrification, so that multi-path denitrification is realized to ensure deep denitrification under the condition of long anoxic operation time. The application reduces the carbon source demand for sewage denitrification, and can realize efficient and energy-saving nitrogen removal of low C / N domestic sewage.

Description

TECHNICAL FIELD

[0001] The application relates to a method for realizing endogenous denitrification reinforced AOA process denitrification based on super-long anoxic retention time, and belongs to the field of sewage biological treatment. BACKGROUND

[0002] With the rapid development of human activities and society, the ecological environment situation of the world is becoming more and more severe. The traditional nitrification-denitrification denitrification process needs a large amount of aeration, and in order to meet the requirements of the effluent, a large amount of external carbon source needs to be added. The energy consumption brought by aeration and the additional cost of adding carbon source significantly increase the cost of sewage treatment.

[0003] As an efficient autotrophic denitrification process, the anaerobic ammonia oxidation process has many advantages such as saving carbon source, not needing aeration, and low sludge yield. However, the application of the anaerobic ammonia oxidation process in mainstream municipal sewage is limited by the lack of nitrite substrate. At present, there are mainly two processes, short-cut nitrification and short-cut denitrification, to provide nitrite substrate for anaerobic ammonia oxidation. Short-cut nitrification can reduce the amount of aeration, reduce sludge yield and save carbon source in application, but also has limitations such as difficult start-up and difficulty in completely washing NOB

[0004] At present, the main control strategies to realize short-cut nitrification include controlling dissolved oxygen, maintaining ammonia nitrogen remaining at the end of the aerobic stage, adding hydroxylamine, etc. According to previous research, each of the foregoing methods alone can realize short-cut nitrification, but recent research shows that the combination of two or more methods is relatively easier to realize and maintain stable short-cut nitrification.

[0005] Hydraulic retention time refers to the average residence time of sewage to be treated in the reactor. In the anaerobic / aerobic / anoxic operation mode, the residence time of each stage is the anaerobic residence time, the aerobic residence time and the anoxic residence time. For biological treatment, HRT should meet the requirements of the corresponding process, otherwise the hydraulic retention time is insufficient, the biochemical reaction is not complete, and the treatment degree is weak; too long hydraulic retention time will cause system sludge aging. For anoxic residence time, sixteen hours and above are considered as super-long residence time.

[0006] The discovery of endogenous denitrification enables people to have a deeper understanding of denitrification with nitrite or nitrate nitrogen. In theory, endogenous denitrification can achieve 100% deep denitrification, and has stronger stability than exogenous denitrification in the case of large fluctuations in carbon-nitrogen ratio. In subsequent operation, combined with the control of relatively short sludge age and the maintenance of appropriate sludge concentration and the adjustment of the ratio of influent domestic sewage to dilution water, the control of influent C / N as 3 can realize deep denitrification under long anoxic residence time, providing a new idea for sewage denitrification. SUMMARY

[0007] The purpose of the present application is to provide a device and method for realizing internal denitrification as the dominant process under long anoxic reaction time operation for low C / N ratio municipal sewage deep denitrification. In the device, domestic sewage in the raw water tank enters the anaerobic stage of the SBR reactor, and a certain proportion of dilution water also enters. The internal carbon source is stored under anaerobic conditions, and the phosphorus accumulating organisms convert COD and VFA into PHA, and part of the nitrogen-containing organic matter is ammoniated. Subsequently, the sewage enters the aerobic stage, and the short-cut nitrification process produces nitrite nitrogen. Subsequently, it enters the anoxic stage. Microorganisms first utilize part of the external carbon source for external denitrification, and then the denitrifying bacteria that have stored internal carbon sources utilize nitrite as an electron acceptor in the process of internal denitrification to reduce nitrogen to nitrogen gas for nitrogen removal. In addition, due to the long residence time, difficult-to-utilize organic matter will also be converted into utilizable carbon sources to further participate in denitrification and nitrogen removal. In summary, under the ultra-long anoxic residence time, multi-path denitrification ensures the deep removal of total nitrogen, providing a new idea for low C / N ratio municipal sewage deep denitrification.

[0008] A method for realizing internal denitrification to strengthen AOA process denitrification based on ultra-long anoxic residence time, the device used mainly includes: a SBR reactor (12) and online pH, DO detection equipment; as shown in Figure 1 The SBR reactor (12) enters domestic sewage through the water inlet system (1), and the stirrer (5) is arranged to stir the internal activated sludge of the reactor to be uniformly mixed; drainage is performed through the water outlet valve (9); the SBR reactor (12) side wall is provided with a drainage valve I (8), a water outlet valve (9), a drainage valve II (10), and a drainage valve III (11), wherein the drainage valve I (8) is used for overflow emptying, and the drainage valve II (10) is used for experimental sludge discharge; the pH probe (3) and the DO probe (4) are connected with the WTW host (2) through data lines, and can reflect the operation parameters inside the reactor.

[0009] A method for realizing internal denitrification to strengthen AOA process denitrification based on ultra-long anoxic residence time, characterized in that it comprises the following steps:

[0010] (1) By operating under long anoxic reaction time, the total nitrogen concentration of the effluent is finally controlled within the range of 5-10 mg / L under ultra-long anoxic reaction time. The anoxic residence time is sixteen hours or more, which is considered as ultra-long anoxic residence time. The sludge type is short-cut nitrification floc sludge inoculated in a sewage treatment plant, and the reactor is debugged to ensure the normal operation of each equipment; the short-cut nitrification sludge taken back is divided and packed, and the activated sludge with a concentration of 8000-12000 mg / L is obtained after centrifugation at a speed of 4000 rpm for three minutes, and then added to the SBR reactor.

[0011] (2) the actual city sewage is introduced, the short-range nitrification flocculation sludge concentration of the sewage plant is controlled to be between 3000-4000 mg / L, the AOA mode is operated, the anaerobic residence time is set to be 2 h, the aerobic residence time is set to be 4 h, and the anoxic residence time is set to be 16 h. In order to ensure that the endogenous denitrification bacteria taking nitrite as an electron acceptor are enriched, the aeration time and the aeration amount are regulated in the aerobic stage, the dissolved oxygen is controlled, and the ammonia nitrogen is controlled to be remained, so that the short-range nitrification is maintained to be stable, and the endogenous denitrification bacteria are provided with sufficient nitrite as a substrate to carry out the denitrification reaction; the dissolved oxygen is controlled to be below 0.05 mg / L in the anaerobic and anoxic stages, the dissolved oxygen is controlled to be 2-3 mg / L in the aerobic stage, and the residual ammonia nitrogen is maintained to be 5-8 mg / L at the end of the aerobic stage. The sludge state and the material change in the reactor are determined by regularly sampling, the nitrite accumulation rate at the end of the aerobic stage is observed fixedly every day, the exogenous denitrification activity in the anaerobic stage, the digestion activity in the aerobic stage and the endogenous denitrification activity of the system in the anoxic stage are determined by the batch experiment method, and when the total nitrogen in the effluent reaches the range of 5-10 mg / L and is maintained to be stable, it is considered that the system is successfully started.

[0012] (3) the SBR reactor is kept to be stably operated every day for two cycles, each cycle is twelve hours, including 10 min of water inlet, 60 min of anaerobic stirring, 120 min of aerobic aeration, 480 min of anoxic stirring, 30 min of sedimentation, 5 min of water outlet, and the rest time is idle, and the water outlet ratio is 50%; in the stable operation stage, the sludge age is kept to be 20-25 days; the proportion of the domestic sewage and the dilution water is adjusted, and the C / N of the water inlet is controlled to be 3; the three nitrogen contents at the end of the anaerobic stage, the end of the aerobic stage and the effluent are measured every day to observe the internal carbon source storage, the short-range nitrification effect and the overall denitrification performance.

[0013] The present application is a kind of based on long anoxic residence time to realize the method for denitrification of endogenous denitrification enhanced AOA process, compared with the technology of short anoxic residence time for denitrification, has the following advantages:

[0014] Effectively utilize carbon source, easily realize the depth removal of nitrogen in sewage, and promote the further application of endogenous denitrification in actual sewage treatment.

[0015] Compared with the exogenous denitrification bacteria domesticated by short anoxic residence time, the polysaccharide bacteria domesticated by long anoxic reaction time have stronger tolerance to environmental changes, and can relatively stably achieve stable and deep denitrification.

[0016] Long anoxic residence time processing reduces sludge production, because in the longer reaction time, microorganisms can more effectively utilize carbon source, and part of the refractory organic matter is degraded into available organic matter, so that the organic matter is better utilized for nitrogen removal. The reduction of sludge production can save part of the subsequent sludge treatment cost. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structural diagram of a process for realizing nitrogen removal by endogenous denitrification reinforced AOA based on super-long anoxic retention time.

[0018] In the figure: 1 is a water inlet system, 2 is a WTW host, 3 is a pH probe, 4 is a DO probe, 5 is a stirrer, 6 is a rotor flowmeter, 7 is a V20 air pump, 8 is a drainage valve I, 9 is a water outlet valve, 10 is a drainage valve II, 11 is a drainage valve III, and 12 is an SBR reactor.

[0019] Figure 2 is a reaction time diagram of each stage in a cycle of the AOA operation mode. DETAILED DESCRIPTION

[0020] The application will be further described in detail below in combination with the drawings and technical solutions, but the application is not limited to the following embodiments.

[0021] REFERENCE Figure 1 A method and device schematic diagram for realizing nitrogen removal by endogenous denitrification reinforced AOA based on super-long anoxic retention time, the device mainly comprises: an SBR reactor (12) and online pH and DO detection equipment; as shown in the figure, the SBR reactor (12) enters domestic sewage through a water inlet system (1), a stirrer (5) is arranged to stir to mix the activated sludge in the reactor; drainage is performed through a water outlet valve (9); the SBR reactor (12) is provided with a drainage valve I (8), a water outlet valve (9), a drainage valve II (10) and a drainage valve III (11) on the side wall, wherein the drainage valve I (8) is used for overflow emptying, and the drainage valve II (10) is used for experimental sludge discharge; a pH probe (3) and a DO probe (4) are connected to a WTW host (2) through data lines to obtain the operation parameters in the reactor. Figure 1

[0022] REFERENCE Figure 1 A method and device schematic diagram for realizing nitrogen removal by endogenous denitrification reinforced AOA based on super-long anoxic retention time, the device mainly comprises: an SBR reactor (12) and online pH and DO detection equipment; as shown in the figure, the SBR reactor (12) enters domestic sewage through a water inlet system (1), a stirrer (5) is arranged to stir to mix the activated sludge in the reactor; drainage is performed through a water outlet valve (9); the SBR reactor (12) is provided with a drainage valve I (8), a water outlet valve (9), a drainage valve II (10) and a drainage valve III (11) on the side wall, wherein the drainage valve I (8) is used for overflow emptying, and the drainage valve II (10) is used for experimental sludge discharge; a pH probe (3) and a DO probe (4) are connected to a WTW host (2) through data lines to obtain the operation parameters in the reactor.

[0022] REFERENCE Figure 1 A method and device schematic diagram for realizing nitrogen removal by endogenous denitrification reinforced AOA based on super-long anoxic retention time, the device mainly comprises: an SBR reactor (12) and online pH and DO detection equipment; as shown in the figure, the SBR reactor (12) enters domestic sewage through a water inlet system (1), a stirrer (5) is arranged to stir to mix the activated sludge in the reactor; drainage is performed through a water outlet valve (9); the SBR reactor (12) is provided with a drainage valve I (8), a water outlet valve (9), a drainage valve II (10) and a drainage valve III (11) on the side wall, wherein the drainage valve I (8) is used for overflow emptying, and the drainage valve II (10) is used for experimental sludge discharge; a pH probe (3) and a DO probe (4) are connected to a WTW host (2) through data lines to obtain the operation parameters in the reactor.

[0023] (1) By operating under long anoxic reaction time, the total nitrogen concentration of the effluent is controlled within 5-10 mg / L under super-long anoxic reaction time operation. The anoxic retention time is 16 hours or more, which is considered as super-long anoxic retention time. The sludge type is short-cut nitrification floc sludge inoculated in a sewage treatment plant, and the reactor is debugged to ensure the normal operation of each equipment; the short-cut nitrification sludge is divided and centrifuged at a speed of 4000 rpm for three minutes, and the activated sludge with a concentration of 8000-12000 mg / L obtained after centrifugation for three times is added to the SBR reactor.

[0024] (2) Actual urban sewage was introduced, and the concentration of short-cut nitrifying flocculent sludge from the sewage treatment plant was controlled to be between 3000 and 4000 mg / L in the SBR reactor after mixing. The reactor was operated in AOA mode, with an anaerobic retention time of 2 h, an aerobic retention time of 4 h, and an anoxic retention time of 16 h. To ensure the enrichment of endogenous denitrifying bacteria that use nitrite as an electron acceptor, the aeration time and aeration rate were adjusted during the aerobic stage to control dissolved oxygen and residual ammonia nitrogen to maintain stable short-cut nitrification and provide sufficient nitrite as a substrate for denitrification by endogenous denitrifying bacteria. Dissolved oxygen was controlled below 0.05 mg / L during the anaerobic and anoxic stages, and 2-3 mg / L during the aerobic stage. The residual ammonia nitrogen at the end of the aerobic stage was maintained at 5-8 mg / L. Regularly sample and measure the sludge state and material changes inside the reactor. Observe the nitrite accumulation rate at the end of the aerobic stage every day. Determine the exogenous denitrification activity in the anaerobic stage, the digestion activity in the aerobic stage, and the endogenous denitrification activity in the anoxic stage through batch experiments. The system is considered to have started successfully when the total nitrogen in the effluent reaches the range of 5-10 mg / L and remains stable.

[0025] (3) Maintain the SBR reactor in stable operation for two cycles per day, each cycle lasting twelve hours, including 10 minutes of influent, 60 minutes of anaerobic stirring, 120 minutes of aerobic aeration, 480 minutes of anoxic stirring, 30 minutes of sedimentation, and 5 minutes of drainage. The remaining time is idle, with a drainage ratio of 50%. During the stable operation phase, maintain a sludge age of 20-25 days. Adjust the ratio of influent domestic sewage to dilution water to control the influent C / N ratio to 3. Measure the anaerobic end, aerobic end, and effluent nitrogen content daily to observe the internal carbon source storage, short-cut nitrification effect, and overall denitrification performance.

[0026] The test results show that after the system stabilizes, the ammonia nitrogen in the final effluent is... Nitrite Total nitrogen 5 mg / L ≤ TN ≤ 10 mg / L.

[0027] This invention relates to an apparatus and method for enhancing nitrogen removal in anoxic AOA (anaerobic retention time) process through endogenous denitrification. This method enables deep removal of nitrogen from wastewater through endogenous denitrification, promoting the application of endogenous denitrification in actual wastewater treatment. It also efficiently maintains short-cut nitrification, reduces carbon source consumption, and achieves deep nitrogen removal in urban domestic wastewater with a low carbon-to-nitrogen ratio. This invention can be widely used for nitrogen removal in urban domestic wastewater.

[0028] The above describes in detail the device and method for denitrification by AOA process through endogenous denitrification strengthening based on ultra-long anoxic residence time provided by the application, and the principle and implementation mode of the application are described by using specific examples, and the above implementation examples are only used to help understand the method of the application and its core idea; meanwhile, for those skilled in the art, the specific implementation mode and application will be changed according to the idea of the application, and the above description should not be understood as a limitation on the application.

Claims

1. A method for enhancing nitrogen removal in an AOA process through endogenous denitrification based on an ultra-long anoxic residence time, characterized in that, The apparatus used includes: an SBR reactor (12), a pH probe (3), and a DO probe (4); the SBR reactor (12) is fed with domestic sewage through the inlet system (1), and a stirrer (5) is set up to stir and mix the activated sludge inside the reactor; the sludge is drained through the outlet valve (9); the SBR reactor (12) is equipped with a drain valve I (8), an outlet valve (9), a drain valve II (10), and a drain valve III (11) on its side wall, wherein the drain valve I (8) is used for overflow and the drain valve II (10) is used for experimental sludge discharge; the pH probe (3) and the DO probe (4) are connected to the WTW host (2) through a data cable; (1) Anoxic retention time of sixteen hours or more is considered as ultra-long anoxic retention time; the sludge type is inoculated short-cut nitrification flocculent sludge from a wastewater treatment plant; the short-cut nitrification sludge is collected and packaged, centrifuged at 4000 rpm, and the supernatant is discarded after centrifugation to obtain activated sludge with a concentration of 8000-12000 mg / L, which is then added to the SBR reactor. (2) Finally, under long anoxic retention time operation, the total nitrogen concentration of the effluent is controlled within the range of 5-10 mg / L and kept stable; domestic sewage is introduced, and short-cut nitrification flocculent sludge from the sewage treatment plant is added to the SBR reactor and the concentration of the mixed sludge is controlled between 3000 and 4000 mg / L. The reactor is operated in AOA mode, with the anaerobic retention time set to 2 h, the aerobic retention time to 4 h, and the anoxic retention time to 16 h; the dissolved oxygen in the anaerobic and anoxic stages is controlled below 0.05 mg / L, the dissolved oxygen in the aerobic stage is controlled at 2-3 mg / L, and the residual ammonia nitrogen at the end of the aerobic stage is maintained at 5-8 mg / L; when the total nitrogen in the effluent reaches the range of 5-10 mg / L, the system is considered to have started successfully. (3) Maintain the SBR reactor in stable operation for two cycles per day, each cycle lasting twelve hours, including 10 minutes of influent, 60 minutes of anaerobic stirring, 120 minutes of aerobic aeration, 480 minutes of anoxic stirring, 30 minutes of sedimentation, and 5 minutes of drainage. The remaining time is idle, with a drainage ratio of 50%. During the stable operation phase, maintain a sludge age of 20-25 days. Adjust the ratio of influent domestic sewage to dilution water to control the influent C / N ratio to 3. Domestic sewage enters the anaerobic stage of the SBR reactor, along with a certain proportion of dilution water. Under anaerobic conditions, endogenous bacteria store internal carbon sources, while polyphosphate-accumulating bacteria convert COD and VFA into PHA, and some nitrogenous organic matter undergoes ammoniation. Subsequently, the sewage enters the aerobic stage, where short-cut nitrification produces nitrite nitrogen. Then, it enters the anoxic stage, where microorganisms first utilize some external carbon sources for external denitrification. Afterward, denitrifying bacteria that have stored internal carbon sources use nitrite as an electron acceptor to reduce it to nitrogen gas for nitrogen removal during the internal denitrification process.

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