A method for achieving stable and efficient short-range nitrification of urban sewage

Abstract

The present invention discloses a method for achieving stable and efficient short-term nitrification of urban sewage, which belongs to the field of sewage treatment. The method inoculates traditional activated sludge in a municipal sewage plant into a sequencing batch reactor, uses municipal sewage as the inlet, and adopts anaerobic / aerobic operation. In the startup phase, the dissolved oxygen concentration of the control system is 1-2 mg / L, and the sludge residence time is 20 days by controlling the amount of sludge discharged in the aerobic stage, so that the system exhibits good full-process nitrification performance. In the short-term nitrification implementation stage, the dissolved oxygen concentration of the system is maintained at 0.1-1 mg / L, and the sludge residence time is 10 days by controlling the amount of sludge discharged in the aerobic stage, the nitrite nitrogen concentration in the effluent is maintained at more than 20 mg / L, the nitrite accumulation rate reaches more than 80%, and the stable operation of the short-term nitrification system is achieved. The invention can be used for low-concentration ammonia nitrogen wastewater treatment, quickly achieve short-term nitrification of urban sewage and have good operational stability, low energy consumption, and easy regulation.

Description

Technical Field

[0001] The invention relates to a method for realizing stable and efficient short-range nitrification of urban sewage, and belongs to the field of sewage biological treatment. Background Art

[0002] Water, as an essential resource for human survival and economic development, is crucial to the development of human society. However, with the continuous development of industrialization and urbanization, the total amount of sewage generated and discharged has increased, and water pollution has become increasingly prominent. Nitrogen-containing pollutants, as the most common pollutants in sewage, have received widespread attention. Traditional biological denitrification processes based on the nitrification-denitrification principle require a large amount of aeration during the nitrification stage, and in subsequent stages, a large amount of carbon source must be added to ensure thorough denitrification, which increases the operating costs of sewage treatment plants. How to solve the problem of pollutant treatment and minimize energy consumption in the sewage treatment process has become a key issue in the field of water pollution control engineering.

[0003] As a cost-effective denitrification process, the short-cut nitrification process reduces aeration energy consumption by 25% during the nitrification process and saves 40% and 100% of the organic carbon source requirements for the subsequent denitrification and anaerobic ammonium oxidation processes, respectively, significantly contributing to energy conservation and cost reduction. However, the short-cut nitrification process still faces technical bottlenecks in its engineering application, especially for mainstream municipal wastewater systems with low ammonia nitrogen concentrations. The dynamic characteristics of municipal wastewater (such as water quality, pH, and temperature) make the mainstream PN / A process a highly complex "open biological process." The short-cut nitrification process performance has poor predictability and controllability for dynamic changes, making it difficult to stabilize nitrite accumulation. During the process of transporting municipal wastewater to the sewage treatment plant through the pipeline system, nitrifying bacteria (ammonia oxidizers and nitrite oxidizers) exist in the pipeline biofilm and are introduced into the sewage treatment plant raw water through the erosion of the biofilm. The continuous supply of nitrite oxidizers will potentially promote the development of nitrite oxidizer communities in the sewage treatment system, thereby disrupting short-cut nitrification. Therefore, the stable supply of nitrite nitrogen in the short-term nitrification process is still the main bottleneck for the application of anaerobic ammonium oxidation process in mainstream urban sewage. On this basis, it is expected to achieve energy saving and efficiency improvement of the deep denitrification process of urban sewage. Summary of the Invention

[0004] The technical problem addressed by this invention is a method for achieving stable and efficient short-term nitrification of municipal wastewater. This method aims to address the current issues of long startup cycles and difficulty maintaining stable short-term nitrification of municipal wastewater. By adjusting operating parameters to achieve stable short-term nitrification of municipal wastewater without incurring additional costs, this method, focusing on the full-process nitrification process, provides a new approach for the efficient application of short-term nitrification in sewage treatment plants under the "dual carbon" strategy. Its features include the following:

[0005] The device used comprises: a water inlet bucket (1), a sequencing batch reactor (2), a drainage bucket (3), a sludge discharge bucket (4), and a PLC control box (5); domestic sewage in the water inlet bucket is pumped into the sequencing batch reactor (2) via a water inlet pump (2.1) to achieve water inlet; the sequencing batch reactor (2) and the drainage bucket (3) are connected via a drainage valve (2.10); the sequencing batch reactor (2) discharges sludge via a sludge discharge pump (2.12), and the discharged sludge is collected in the sludge discharge bucket (4); the PLC control box (5) controls the air pump (2.3), the water inlet pump (2.1), the agitator (2.6), the sludge discharge pump (2.12), the drainage valve (2.10), the water quality online detector (2.7), the dissolved oxygen probe (2.8), and the pH probe (2.9).

[0006] Phase 1, reactor startup, the specific steps are as follows:

[0007] The activated sludge from the municipal sewage treatment plant is injected into the sequencing batch reactor (2); the influent is actual domestic sewage; the sequencing batch reactor (2) is operated alternately in an anaerobic / aerobic manner, and the mud-water mixture of the sequencing batch reactor (2) is heated by a heating device (2.13), and the temperature is controlled at 25±1°C. Each cycle includes five stages: water inlet, anaerobic stirring, aerobic stirring, sedimentation, and drainage idleness, and four cycles are performed every day; after the water inlet is completed, the anaerobic stirring stage is entered, and the anaerobic stirring stage is set to 1 hour; the aerobic stage is set to 3 hours, and the PLC control box (5) controls the air pump (2.3) to start. In the aerobic stage, the dissolved oxygen probe (2.8) of the water quality online detector WTW (2.7) is used to monitor the dissolved oxygen concentration in real time, and the gas flow meter (2.4) is used to control the dissolved oxygen concentration. The dissolved oxygen concentration is controlled to be 1-2 mg / L; at the end of the aerobic stage of each cycle, the sludge pump (2.12) is controlled by the PLC control box (5) to regularly discharge sludge from the sequencing batch reactor (2) to the sludge barrel (4), and the sludge age SRT is controlled to be 20 days; the PLC control box (5) controls the air pump (2.3) to be turned off, and controls the agitator (2.6) to stop stirring, and then the sedimentation stage lasts for 0.5 hours. The system controls the drainage through the drain valve (2.10) and enters the idle stage, and the drainage ratio is 50%; the effluent ammonia nitrogen removal rate at the end of the aerobic stirring stage is controlled to reach more than 90%, the ammonia nitrogen concentration is less than 10 mg / L, the nitrite nitrogen concentration is less than 1 mg / L, and the nitrate nitrogen concentration is greater than 20 mg / L, and the reactor startup stage is completed.

[0008] Phase II: the realization of short-range nitrification. The specific operation steps are as follows:

[0009] The sequencing batch reactor (2) operates in an anaerobic and aerobic mode, and the temperature is controlled at 25±1°C. Each cycle includes five stages: water inlet, anaerobic stirring, aerobic stirring, sedimentation, and drainage idleness, with four cycles per day. The water inlet is actual domestic sewage, and after the water inlet is completed, the anaerobic stirring stage is entered, and the anaerobic stirring stage is set to 1 hour; the aerobic stage is set to 3 hours, and the PLC control box (5) controls the air pump (2.3) to start. In the aerobic stage, the dissolved oxygen probe (2.8) of the water quality online detector WTW (2.7) is used to monitor the dissolved oxygen concentration in real time, and the dissolved oxygen concentration is controlled to 0.1-1 mg / L by the gas flow meter (2.4). At the end of the aerobic stage of each cycle, the PLC control box (5) is used to control the dissolved oxygen concentration to 0.1-1 mg / L. The sludge pump (2.12) is controlled to discharge sludge from the sequencing batch reactor (2) to the sludge barrel (4) at regular intervals, and the sludge age SRT is controlled to be 10 days; the PLC control box (5) controls the air pump (2.3) to be turned off, and controls the agitator (2.6) to stop stirring, and then the sedimentation stage lasts for 0.5 hours. The system controls the drainage through the drain valve (2.10) and enters the idle stage, with a drainage ratio of 50%; the ammonia nitrogen concentration at the end of the aerobic stirring stage is controlled to be maintained at 10-15 mg / L, the nitrite nitrogen concentration is above 20 mg / L, the nitrate nitrogen concentration is less than 1.0 mg / L, the nitrite accumulation rate reaches above 80%, and stable operation is maintained for more than 20 days, successfully achieving short-range nitrification of urban sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a structural schematic diagram of the test device of the present invention.

[0011] Figure 1 In the middle: 1 is the water inlet barrel, 2 is the sequencing batch reactor, 2.1 is the water inlet pump, 2.2 is the water inlet valve, 2.3 is the air pump, 2.4 is the gas flow meter, 2.5 is the aeration plate, 2.6 is the stirrer, 2.7 is the water quality online detector WTW, 2.8 is the dissolved oxygen probe, 2.9 is the pH probe, 2.10 is the drain valve, 2.11 is the sludge valve, 2.12 is the sludge pump, 2.13 is the heating device, 3 is the drain barrel, 4 is the sludge barrel, and 5 is the PLC control system.

[0012] Figure 2 It is the effect diagram of the present invention.

[0013] Figure 3 This is another effect diagram of the present invention. DETAILED DESCRIPTION

[0014] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0015] The raw water enters the sequencing batch reactor (2) from the water inlet tank (1) through the water inlet pump (2.1), and the mud-water mixture is mixed by the stirrer (2.6). The mud-water mixture in the sequencing batch reactor (2) is heated by the heating device (2.13), and the temperature is controlled at 25±1°C. The aeration in the aerobic stage is jointly controlled by the air pump (2.3) and the gas flow meter (2.4), and the dissolved oxygen concentration is controlled at 0.1-2mg / L. At the end of the aerobic stage of each cycle, the sludge pump (2.12) is controlled by the PLC control box (5) to regularly discharge sludge from the sequencing batch reactor (2) to the sludge barrel (4), and the sludge age SRT is controlled to 10-20 days. After the end of the aerobic stage, the sedimentation is carried out for 30 minutes, and then the drainage idle stage is entered. The PLC control box (5) controls the air pump (2.3), the water inlet pump (2.1), the agitator (2.6), the sludge pump (2.12), the drain valve (2.10), the water quality online detector (2.7), the dissolved oxygen probe (2.8) and the pH probe (2.9).

[0016] This patent is applicable to the treatment of urban sewage. The urban sewage used in the specific example comes from a septic tank in a residential area in Beijing. The water quality indicators are as follows: the average concentration of ammonia nitrogen is 68.3 mg / L, the average concentration of nitrite nitrogen and nitrate nitrogen are both less than 1 mg / L, and the average COD concentration is 170 mg / L. The required seed sludge comes from the traditional activated sludge of a municipal sewage treatment plant in Beijing and is injected into the sequencing batch reactor (2). The system device is as follows: Figure 1 As shown, the sequencing batch reactor (2) is made of organic glass and has an effective volume of 10L.

[0017] The specific operation operations are as follows:

[0018] The sequencing batch reactor (2) was operated in an anaerobic / aerobic manner, with four cycles per day, each lasting 6 hours, including water inlet (15 minutes), anaerobic stirring (45 minutes), aerobic stirring (180 minutes), sedimentation (30 minutes), drainage (5 minutes), and idleness (25 minutes). At the end of the aerobic stirring phase of each cycle, sludge was discharged from the sequencing batch reactor (2) to the sludge discharge tank (4) by controlling the sludge discharge pump (2.12), and the sludge retention time (SRT) was controlled to be 10-20 days. The dissolved oxygen concentration was controlled to be 0.1-2 mg / L by a gas flow meter (2.4).

[0019] During the reactor startup phase (days 1-15), the system was inoculated with sludge and started operating. The aeration rate was controlled at 300 mL / min, the dissolved oxygen concentration was 1-2 mg / L, and the sludge retention time (SRT) was controlled at 20 days. By the end of the aerobic agitation phase, the effluent ammonia nitrogen removal rate exceeded 90%, with ammonia nitrogen concentrations less than 10 mg / L, nitrite nitrogen concentrations less than 1 mg / L, and nitrate nitrogen concentrations greater than 20 mg / L, successfully initiating the full nitrification system.

[0020] During the short-term nitrification phase (days 16-130), the dissolved oxygen concentration was controlled at 0.1-1 mg / L, and the sludge retention time (SRT) was controlled at 10 days by increasing the sludge discharge at the end of the aerobic mixing phase. From days 16-35, the nitrite nitrogen concentration at the end of the aerobic mixing phase increased to 16 mg / L, while the nitrate nitrogen concentration decreased to 13 mg / L. Over the subsequent 36-130 days, the system maintained stable short-term nitrification performance, with a DO concentration range of 0.1-1 mg / L, an ammonia nitrogen concentration at the end of the aerobic mixing phase maintained at 10-15 mg / L, a nitrite nitrogen concentration above 20 mg / L, a nitrate nitrogen concentration below 1.0 mg / L, and a nitrite accumulation rate exceeding 80%, indicating that the activated sludge has good short-term nitrification characteristics.

[0021] The advantages of this invention are:

[0022] 1) Simple operation and strong stability, with a short startup cycle: The device of the present invention is a sequencing batch reactor (SBR). It only needs to control the sludge discharge and dissolved oxygen concentration to achieve rapid startup and stable operation of the short-range nitrification process, which is convenient for the transformation of existing SBR processes and the construction of small and medium-sized sewage treatment plants.

[0023] 2) Efficient and economical: This invention can achieve the retention of functional bacteria without using any chemicals, improve volumetric load, reduce floor space, and reduce operating costs, providing a new approach for the efficient application of short-range nitrification processes in sewage treatment plants under the background of "dual carbon";

[0024] 3) Suitable for developing new technologies for biological treatment of sewage: Based on the present invention, a partial short-range nitrification-anaerobic ammonium oxidation process can be constructed by inoculating or self-enriching anaerobic ammonium oxidizing bacteria to achieve deep denitrification of urban sewage.

[0025] The above is a specific implementation of the present invention, which is convenient for technicians in this technical field to better understand and apply the present invention, but the implementation of the present invention is not limited to this. Therefore, simple improvements made to the present invention by technicians in this technical field are within the scope of protection of the present invention.

Claims

1. A method for achieving stable and efficient short-range nitrification of urban sewage, characterized by: The device used comprises: a water inlet bucket (1), a sequencing batch reactor (2), a drainage bucket (3), a sludge discharge bucket (4), and a PLC control box (5); domestic sewage in the water inlet bucket is pumped into the sequencing batch reactor (2) via a water inlet pump (2.1) to achieve water inlet; the sequencing batch reactor (2) and the drainage bucket (3) are connected via a drainage valve (2.10); the sequencing batch reactor (2) discharges sludge via a sludge discharge pump (2.12), and the discharged sludge is collected in the sludge discharge bucket (4); the PLC control box (5) controls an air pump (2.3), a water inlet pump (2.1), an agitator (2.6), a sludge discharge pump (2.12), a drainage valve (2.10), an online water quality detector WTW (2.7), a dissolved oxygen probe (2.8), and a pH probe (2.9); Phase 1, reactor startup, the specific steps are as follows: The activated sludge from the municipal sewage treatment plant is injected into the sequencing batch reactor (2); the influent is actual domestic sewage; the sequencing batch reactor (2) is operated alternately in an anaerobic / aerobic manner, and the mud-water mixture in the sequencing batch reactor (2) is heated by a heating device (2.13), and the temperature is controlled at 25±1°C. Each cycle includes five stages: water inlet, anaerobic stirring, aerobic stirring, sedimentation, and drainage and idleness, with four cycles per day; after the water inlet is completed, the anaerobic stirring stage is entered, and the anaerobic stirring stage is set to 1h; the aerobic stage is set to 3h, and the PLC control box (5) controls the air pump (2.3) to start, and the dissolved oxygen concentration is monitored in real time during the aerobic stage, and the dissolved oxygen concentration is controlled to 1-2mg / L by a gas flow meter (2.4) At the end of the aerobic stage of each cycle, the sludge pump (2.12) is controlled by the PLC control box (5) to regularly discharge sludge from the sequencing batch reactor (2) to the sludge barrel (4), and the sludge age SRT is controlled to be 20 days; the PLC control box (5) controls the air pump (2.3) to be turned off, and controls the agitator (2.6) to stop stirring, and then the sedimentation stage lasts for 0.5 hours. The system controls the drainage through the drain valve (2.10) and enters the idle stage, and the drainage ratio is 50%; the effluent ammonia nitrogen removal rate at the end of the aerobic stirring stage is controlled to reach more than 90%, the ammonia nitrogen concentration is less than 10 mg / L, the nitrite nitrogen concentration is less than 1 mg / L, and the nitrate nitrogen concentration is greater than 20 mg / L, and the reactor startup stage is completed; Phase II: realization of short-range nitrification. The specific operation steps are as follows: The sequencing batch reactor (2) operates in an anaerobic and aerobic mode, and the temperature is controlled at 25±1°C. Each cycle includes five stages: water inlet, anaerobic stirring, aerobic stirring, sedimentation, and drainage idleness, with four cycles per day. The water inlet is actual domestic sewage, and after the water inlet is completed, it enters the anaerobic stirring stage, which is set to 1 hour; the aerobic stage is set to 3 hours, and the PLC control box (5) controls the air pump (2.3) to start. In the aerobic stage, the dissolved oxygen probe (2.8) of the water quality online detector WTW (2.7) is used to monitor the dissolved oxygen concentration in real time, and the dissolved oxygen concentration is controlled to 0.1-1 mg / L by the gas flow meter (2.4). At the end of the aerobic stage of each cycle, the PL The C control box (5) controls the sludge pump (2.12) to regularly discharge sludge from the sequencing batch reactor (2) to the sludge barrel (4), and controls the sludge age (SRT) to be 10 days; the PLC control box (5) controls the air pump (2.3) to be turned off, controls the agitator (2.6) to stop stirring, and then the sedimentation stage lasts for 0.5 hours. The system controls the drainage through the drain valve (2.10) and enters the idle stage, with a drainage ratio of 50%; the ammonia nitrogen concentration at the end of the aerobic stirring stage is controlled to be maintained at 10-15 mg / L, the nitrite nitrogen concentration is above 20 mg / L, the nitrate nitrogen concentration is less than 1.0 mg / L, the nitrite accumulation rate reaches above 80%, and stable operation is maintained for more than 20 days.

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