Method for realizing stable and efficient short-cut nitrification of municipal sewage

Abstract

The invention discloses a method for realizing stable and efficient short-cut nitrification of municipal sewage, and belongs to the field of sewage treatment. According to the method, traditional activated sludge in a municipal sewage plant is inoculated into a sequencing batch reactor, municipal sewage is adopted as inflow water, and anaerobic / aerobic operation is adopted. In the starting stage, the dissolved oxygen concentration of the system is controlled to be 1-2 mg / L, and the sludge retention time is 20 days by controlling the sludge discharge amount in the aerobic stage, so that the system shows good whole-course nitrification performance. In the short-cut nitrification implementation stage, the dissolved oxygen concentration of the system is kept to be 0.1-1 mg / L, the sludge retention time is 10 days by controlling the sludge discharge amount in the aerobic stage, the nitrite nitrogen concentration of effluent is kept to be 20 mg / L or above, the nitrite accumulation rate reaches 80% or above, and stable operation of the short-cut nitrification system is achieved. The device can be used for treating low-concentration ammonia-nitrogen wastewater, quickly realizes short-cut nitrification of urban sewage, has good operation stability, and is low in energy consumption and easy to regulate and control.

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] As a necessary resource for the survival and economic development of human society, water is of vital importance 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 the problem of water pollution has become increasingly prominent. Nitrogen-containing pollutants, as the most common pollutants in sewage, have received widespread attention. The traditional biological denitrification process based on the nitrification-denitrification principle requires a large amount of aeration in the nitrification stage. In addition, a large amount of carbon source needs to be added in the subsequent stage to ensure thorough denitrification, which increases the operating cost of the sewage treatment plant. How to solve the problem of pollutant treatment and maximize the reduction of energy consumption in the sewage treatment process has become a focal issue in the field of water pollution control engineering.

[0003] As an economical and efficient denitrification process, the short-cut nitrification process reduces 25% of the aeration energy consumption in the nitrification process, and saves 40% and 100% of the organic carbon source requirements of the subsequent denitrification and anaerobic ammonia oxidation processes, respectively, which can significantly play a role in energy saving and consumption reduction. However, there are still technical bottlenecks in the engineering application of the short-cut nitrification process, especially for the mainstream municipal sewage system with low ammonia nitrogen concentration. The dynamic characteristics of municipal sewage (such as water quality, pH, temperature) make the mainstream PN / A process a highly complex "open biological process", and the process performance of short-cut nitrification has poor predictability and controllability for dynamic changes, making it difficult for nitrite to accumulate stably. In the process of transporting municipal sewage to the sewage treatment plant through the pipeline system, since nitrifying bacteria (ammonia oxidizing bacteria and nitrite oxidizing bacteria) exist in the pipeline biofilm and are introduced into the raw water of the sewage plant with the erosion of the biofilm, the continuous supply of nitrite oxidizing bacteria will potentially promote the development of nitrite oxidizing bacteria communities in the sewage treatment system, thereby leading to the destruction of 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 urban sewage deep denitrification process. Summary of the invention

[0004] The technical problem provided by the present invention is a method for achieving stable and efficient short-term nitrification of urban sewage, aiming to solve the problem that the current short-term nitrification of urban sewage has a long startup cycle and is difficult to maintain stably. Taking the full-process nitrification process as the research object, the stable short-term nitrification of urban sewage is achieved by adjusting the operating parameters without incurring additional costs, providing a new idea for the efficient application of short-term nitrification technology in sewage treatment plants under the background of "dual carbon". Its characteristics 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); the domestic sewage in the water inlet bucket is pumped into the sequencing batch reactor (2) through a water inlet pump (2.1) to achieve water inlet; the sequencing batch reactor (2) and the drainage bucket (3) are connected through a drainage valve (2.10); the sequencing batch reactor (2) discharges sludge through 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 operating 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 sludge-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 and 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 1h; the aerobic stage is set to 3h, 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, and the system enters the idle stage after controlling the drainage through the drainage valve (2.10), 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 anaerobically and aerobically mode, 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, and four cycles are performed every day. The water inlet is actual domestic sewage. 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 through the gas flow meter (2.4); at the end of the aerobic stage of each cycle, the PLC control box (5) 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, 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 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 more than 80%, and the stable operation is maintained for more than 20 days, successfully realizing the short-range nitrification of urban sewage. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0011] Figure 1 In the figure: 1 is the water inlet bucket, 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 mud valve, 2.12 is the mud pump, 2.13 is the heating device, 3 is the water drain bucket, 4 is the mud bucket, 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 are 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 agitator (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 be 10-20 days. After the aerobic stage, the sedimentation is carried out for 30 minutes, and 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 ammonia nitrogen concentration is 68.3 mg / L, the average nitrite nitrogen concentration and nitrate nitrogen concentration 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 is as follows:

[0018] The sequencing batch reactor (2) is operated in an anaerobic / aerobic mode, with four cycles set daily, each cycle 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, the sludge is discharged from the sequencing batch reactor (2) to the sludge discharge barrel (4) by controlling the sludge discharge pump (2.12), and the sludge retention time SRT is controlled to be 10-20 days. The dissolved oxygen concentration is controlled to be 0.1-2 mg / L by a gas flow meter (2.4).

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

[0020] In the short-term nitrification realization stage (16-130 days), the dissolved oxygen concentration was controlled at 0.1-1 mg / L, and the sludge retention time SRT was controlled to 10 days by increasing the sludge discharge at the end of the aerobic stirring stage. On days 16-35, the nitrite nitrogen concentration at the end of the aerobic stirring stage increased to 16 mg / L, and the nitrate nitrogen concentration dropped to 13 mg / L. In the subsequent 36-130 days, the system maintained stable short-term nitrification performance, with a DO concentration range of 0.1-1 mg / L, ammonia nitrogen concentration at the end of the aerobic stirring stage maintained at 10-15 mg / L, nitrite nitrogen concentration above 20 mg / L, nitrate nitrogen concentration less than 1.0 mg / L, and nitrite accumulation rate reached more than 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, short start-up period: The device of the present invention is a sequencing batch reactor (SBR), which can achieve rapid start-up and stable operation of the short-range nitrification process by simply controlling the sludge discharge and dissolved oxygen concentration, which is convenient for the transformation of the existing SBR process and the construction of small and medium-sized sewage treatment plants;

[0023] 2) High efficiency and economy: The present invention can achieve the retention of functional bacteria without using any agents, improve volume load, reduce floor space, and reduce operating costs, providing a new idea for the efficient application of short-range nitrification processes in sewage treatment plants under the background of "double 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 all 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); the domestic sewage in the water inlet bucket is pumped into the sequencing batch reactor (2) through a water inlet pump (2.1) to realize water inlet; the sequencing batch reactor (2) and the drainage bucket (3) are connected through a drainage valve (2.10); the sequencing batch reactor (2) discharges sludge through 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); Phase 1, reactor startup, the specific operating 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 sludge-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 and 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 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 through 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 enters the idle stage after controlling the drainage through the drain valve (2.10), 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, the realization of short-range nitrification, the specific operation steps are as follows: The sequencing batch reactor (2) operates in anaerobically and aerobically mode, 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, and four cycles are performed every day. The water inlet is actual domestic sewage. 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 through 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 discharge sludge from the sequencing batch reactor (2) to the sludge barrel (4) at regular intervals, 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, and the drainage ratio is 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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