Sewage treatment method

Abstract

The invention discloses a sewage treatment method which comprises the following steps: sewage is treated through a sewage treatment area, and the sewage treatment area comprises an anaerobic area, an aerobic area and an anoxic area which are communicated in sequence; wherein the aerobic zone comprises a front section, a middle section and a rear section; in the aerobic zone, the ammonia nitrogen concentration and the dissolved oxygen concentration of the sewage in the middle section and the rear section of the aerobic zone are monitored in real time, and the aeration rate of the aerobic zone is regulated and controlled in real time according to the ammonia nitrogen concentration of the aerobic zone, so that the sewage treatment process is accurately controlled. According to the sewage treatment method provided by the invention, the sewage treatment effect can be monitored in real time, the aeration rate can be dynamically regulated and controlled according to the sewage quality, oxygen supply according to needs is realized, the aeration energy consumption is reduced while the sewage treatment effect is ensured, and thus the operation cost of sewage treatment is reduced; and secondly, the aeration rate of the aerobic zone can be flexibly adjusted according to the fluctuation of the inflow water quantity, so that the nitrogen and phosphorus removal effect is ensured.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment, and more specifically, to a wastewater treatment method. Background Technology

[0002] Due to its low carbon-to-nitrogen ratio, the key challenge in achieving compliant discharge of urban domestic sewage lies in the removal of total nitrogen. Ammonia nitrogen, as one of the main nitrogenous pollutants in sewage, can easily lead to eutrophication of water bodies if discharged directly without effective treatment, adversely affecting the ecological environment and human health. Therefore, how to efficiently and stably remove ammonia nitrogen from sewage has become one of the urgent technical problems to be solved in the field of sewage treatment.

[0003] Currently, to address the two key technical challenges of "difficulty in achieving discharge standards" and "difficulty in energy conservation and consumption reduction" in urban wastewater treatment, the anaerobic-aerobic-anoxic combined process is widely used in urban wastewater treatment due to its combined functions of organic matter removal and biological nitrogen removal. This process balances high-standard effluent requirements with low energy consumption and low carbon source consumption, achieving low-cost, high-efficiency deep treatment of wastewater through system optimization of the process pathway and reconstruction of energy metabolism mechanisms. However, the operating mode of the anaerobic / aerobic / anoxic process differs significantly from the traditional AAO (anaerobic / anoxic / aerobic) process, and its response mechanism to control parameters and microbial kinetics also differ significantly. Currently, there is a lack of systematic operation control methods and dynamic regulation strategies for the anaerobic / aerobic / anoxic process. Especially under conditions such as fluctuations in influent water quality and quantity, changes in ambient temperature, and low winter temperatures, how to stably maintain the nitrogen and phosphorus removal efficiency of the anaerobic / aerobic / anoxic system remains a key technical bottleneck restricting its large-scale application.

[0004] Therefore, how to provide a wastewater treatment method that can efficiently and stably control the wastewater treatment process is a technical problem that needs to be solved in this field. Summary of the Invention

[0005] In view of this, this application proposes a wastewater treatment method.

[0006] According to this application, a wastewater treatment method is proposed, comprising: treating wastewater in a wastewater treatment zone, the wastewater treatment zone comprising an anaerobic zone, an aerobic zone, and an anoxic zone connected in sequence; wherein the aerobic zone comprises a front section, a middle section, and a rear section; in the aerobic zone, the ammonia nitrogen concentration and dissolved oxygen concentration of the wastewater in the middle section and the rear section of the aerobic zone are monitored in real time, and the aeration rate of the aerobic zone is adjusted in real time according to the ammonia nitrogen concentration of the aerobic zone, so as to precisely control the wastewater treatment process.

[0007] Preferably, the aeration rate of the aerobic zone is determined based on the ammonia nitrogen concentration in the latter part of the aerobic zone; in winter, the ammonia nitrogen concentration in the aerobic zone is 0.5-1 mg / mL; in summer, the ammonia nitrogen concentration in the aerobic zone is 0.3-0.6 mg / mL.

[0008] Preferably, the aeration rate of the aerobic zone and / or the downstream section is determined based on the ammonia nitrogen concentration in the intermediate section; when the ammonia nitrogen concentration in the intermediate section exceeds the ammonia nitrogen concentration threshold, the aeration rate is increased to ensure that the nitrification reaction is stably completed in the aerobic zone; preferably, the ammonia nitrogen concentration threshold is that the ammonia nitrogen concentration in the intermediate section is greater than 1 / 3 of the ammonia nitrogen concentration in the influent of the aerobic zone.

[0009] Preferably, the dissolved oxygen in the front, middle and rear sections of the aerobic zone is distributed in a gradient.

[0010] Preferably, the dissolved oxygen is distributed in a gradient according to the dissolved oxygen concentration in the latter part; in winter, the dissolved oxygen concentration in the latter part is 0.3-0.5 mg / mL; in summer, the dissolved oxygen concentration in the latter part is 0.2-0.4 mg / L.

[0011] Preferably, the wastewater treatment area further includes: an online monitoring system installed in the middle and rear sections of the aerobic zone to monitor the ammonia nitrogen and dissolved oxygen concentrations in the aerobic zone in real time; an aeration system that provides oxygen to the aerobic zone and is electrically connected to the online monitoring system; and a control system that is electrically connected to the online monitoring system and the aeration system for adjusting the aeration rate of the aeration system.

[0012] Preferably, the online monitoring system is located at the end of the middle and later sections of the aerobic zone; the online monitoring system includes: an online ammonia nitrogen monitor for real-time monitoring of the ammonia nitrogen concentration in the middle and later sections of the aerobic zone; and an online dissolved oxygen monitor for real-time monitoring of the dissolved oxygen concentration in the middle and later sections of the aerobic zone.

[0013] Preferably, the aeration system includes: a blower disposed outside the aerobic zone for supplying oxygen to the aerobic zone; an aeration control unit electrically connected to the blower for controlling the aeration rate of the aerobic zone; an aeration main pipe connected to the blower; aeration branch pipes disposed at the front, middle, and rear sections of the aerobic zone and connected to the aeration main pipe; and aeration heads disposed within the aerobic zone, with densities at the front, middle, and rear sections representing 40%–50%, 30%–40%, and 20%–30% of the total number of aeration heads in the aerobic zone, respectively.

[0014] Preferably, the wastewater treatment area further includes: a flow meter installed at the inlet of the wastewater treatment area; an online water quality monitor for monitoring the pH, ammonia nitrogen concentration, and COD concentration of the wastewater inlet; and an online water temperature monitor for monitoring the water temperature of the wastewater inlet. The flow meter, the online water quality monitor, and the online water temperature monitor are electrically connected to the control system of the wastewater treatment area. The control system adjusts the aeration intensity of the aerobic zone based on the water quality and temperature of the wastewater inlet, providing space for adjusting the aeration volume of the aerobic zone.

[0015] Preferably, the wastewater treatment area further includes: a secondary sedimentation tank located at the end of the wastewater treatment area for separating wastewater and sludge; and a reoxygenation zone located behind the anoxic zone in the wastewater treatment area, connected to the anoxic zone and the secondary sedimentation tank, for keeping the wastewater in the secondary sedimentation tank in an aerobic state and preventing sludge from floating; wherein, a portion of the sludge in the secondary sedimentation tank is returned to the anaerobic and anoxic zones, and the other portion is directly discharged.

[0016] According to the wastewater treatment method in this application, the wastewater treatment effect can be monitored in real time, and the aeration volume can be dynamically adjusted according to the wastewater quality to achieve on-demand oxygen supply. While ensuring the wastewater treatment effect, the aeration energy consumption is reduced, thereby reducing the operating cost of wastewater treatment. Secondly, the aeration volume of the aerobic zone can be flexibly adjusted according to the fluctuation of the influent volume to ensure the effect of nitrogen and phosphorus removal.

[0017] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application, and the illustrative embodiments and descriptions thereof are used to explain this application. In the drawings: Figure 1 This is a schematic diagram of the wastewater treatment process according to the first embodiment of this application.

[0019] Figure 2 This is a schematic diagram of the wastewater treatment process according to the second embodiment of this application.

[0020] Figure 3 This is a schematic diagram of the wastewater treatment area according to this application.

[0021] Figure 4 This is a plan view of the aerobic zone according to this application.

[0022] Figure 5 This is a schematic diagram of aeration control in the aerobic zone according to the wastewater treatment method in this application. Detailed Implementation

[0023] The technical solution of this application will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] According to this application, such as Figures 1-5 As shown, a wastewater treatment method is proposed, which includes: wastewater being treated in a wastewater treatment zone, the wastewater treatment zone comprising an anaerobic zone 1, an aerobic zone 2, and an anoxic zone 3 connected in sequence; wherein, the aerobic zone 2 comprises a front section 21, a middle section 22, and a rear section 23; in the aerobic zone 2, the ammonia nitrogen concentration and dissolved oxygen concentration of the wastewater in the middle section 22 and the rear section 23 of the aerobic zone 2 are monitored in real time, and the aeration rate of the aerobic zone 2 is adjusted in real time according to the ammonia nitrogen concentration of the aerobic zone 2, so as to precisely control the wastewater treatment process.

[0025] The aforementioned wastewater treatment area also includes an inlet area, where wastewater can directly enter the anaerobic zone 1. Alternatively, a pretreatment area can be set up between the anaerobic zone 1 and the inlet area to remove large particulate impurities, floating matter, etc., from the wastewater to ensure stable operation of the wastewater treatment. The pretreatment area can take an appropriate form, such as a coarse screen, a fine screen, or a grit chamber, depending on the type of wastewater being treated.

[0026] The front section 21, middle section 22, and rear section 23 of the aforementioned aerobic zone 2 are located in the same space, or the front section 21, middle section 22, and rear section 23 are separated by a partition wall and connected in the middle by an inlet (outlet). Secondly, the front section 21, middle section 22, and rear section 23 are of the same length, each occupying 1 / 3 of the length of the aerobic zone 2.

[0027] Monitoring the ammonia nitrogen concentration in the latter part (23) of aerobic zone 2 is used to determine whether the ammonia nitrogen in the wastewater has been completely nitrified, while monitoring the ammonia nitrogen concentration in the middle part (22) is used to determine the stability of the nitrification reaction in aerobic zone 2 and the trend of load changes. This allows for real-time monitoring of the wastewater treatment effect and timely adjustment of the aeration rate in aerobic zone 2 based on water quality, improving the efficiency and effectiveness of ammonia nitrogen treatment. Furthermore, it avoids energy waste caused by over-aeration in aerobic zone 2, thereby reducing wastewater treatment costs.

[0028] According to a preferred embodiment of this application, the aeration rate of the aerobic zone 2 can be determined based on the ammonia nitrogen concentration in the latter part 23 of the aerobic zone 2. In winter, when the temperature is low, the ammonia nitrogen concentration in the aerobic zone 2 is 0.5-1 mg / mL. When the ammonia nitrogen concentration in the latter part 23 of the aerobic zone 2 is lower than 0.5 mg / mL, the aeration rate needs to be reduced; when the ammonia nitrogen concentration in the latter part 23 of the aerobic zone 2 is higher than 1 mg / mL, the aeration rate needs to be increased. In summer, when the temperature is high, the ammonia nitrogen concentration in the aerobic zone 2 is 0.3-0.6 mg / mL. When the ammonia nitrogen concentration in the latter part 23 of the aerobic zone 2 is lower than 0.3 mg / mL, the aeration rate needs to be reduced; when the ammonia nitrogen concentration in the latter part 23 of the aerobic zone 2 is higher than 0.6 mg / mL, the aeration rate needs to be increased.

[0029] According to another preferred embodiment of this application, the aeration rate of the aerobic zone 2 and / or the downstream section 23 is determined based on the ammonia nitrogen concentration of the intermediate section 22. When the ammonia nitrogen concentration of the intermediate section 22 exceeds the ammonia nitrogen concentration threshold, the aeration rate is increased to ensure that the nitrification reaction is stably completed in the aerobic zone 2. Preferably, the ammonia nitrogen concentration threshold is that the ammonia nitrogen concentration of the intermediate section 22 is greater than 1 / 3 of the ammonia nitrogen concentration in the influent of the aerobic zone 2. By increasing the aeration rate of the aerobic zone 2 or increasing the aeration rate of the downstream section 23 of the aerobic zone 2, the ammonia nitrogen in the wastewater is ensured to be nitrified as much as possible in the aerobic zone 2, so as to achieve a better wastewater treatment effect. The influent of the aerobic zone 2 is wastewater after pretreatment of the effluent and the return sludge. The control system 13 in the wastewater treatment area determines that the nitrification reaction is insufficient under the current load conditions, and then compensates by increasing the overall aeration rate of the aerobic zone 2 and / or increasing the aeration rate of the downstream section 23 of the aerobic zone 2. The two are synergistically regulated to ensure that the ammonia nitrogen at the end of the treatment zone is stably up to standard.

[0030] In this application, on the one hand, the aeration rate of aerobic zone 2 is determined according to the season. Ammonia nitrogen removal in aerobic zone 2 depends on nitrification. In winter, the water temperature is low, the oxygen utilization efficiency of nitrifying bacteria decreases, and the nitrification rate decreases significantly. At this time, it is necessary to increase the aeration rate of aerobic zone 2 to ensure nitrification efficiency. In summer, the water temperature is high, and the nitrification rate is fast. At this time, the aeration rate can be reduced to avoid over-aeration and save energy. On the other hand, the nitrification load of aerobic zone 2 can be directly reflected by the ratio of the ammonia nitrogen concentration in the middle section 22 of aerobic zone 2 to the ammonia nitrogen concentration in the influent. The ammonia nitrogen concentration in the middle section 22 of aerobic zone 2 can directly reflect the real-time removal status of ammonia nitrogen in the reaction process of aerobic zone 2. Moreover, the ratio of the two can reflect the influence of fluctuations in the influent ammonia nitrogen concentration, and can more realistically reflect whether the influent ammonia nitrogen matches the actual nitrification load. Therefore, this application considers the changes in water temperature during winter and summer, as well as the fluctuations in influent ammonia nitrogen concentration. These two aspects work synergistically to adjust the aeration rate in aerobic zone 2, thereby achieving timely and accurate adjustment of the aeration rate, saving energy, and ensuring nitrification efficiency. This dual-layer ammonia nitrogen control logic expands the control process from "outcome control" to "process control."

[0031] During the wastewater treatment process, the ammonia nitrogen concentration in the front section 21, middle section 22 and rear section 23 of the aerobic zone 2 gradually decreases. In order to provide oxygen that matches the ammonia nitrogen concentration in the wastewater, preferably, the dissolved oxygen in the front section 21, middle section 22 and rear section 23 of the aerobic zone 2 can be distributed in a gradient, so that the dissolved oxygen in each section matches the actual nitrification reaction load, improves the utilization rate of dissolved oxygen, reduces system energy consumption, and enhances the stability of the nitrification reaction.

[0032] The dissolved oxygen concentration in the latter part (23) of aerobic zone 2 directly reflects the sufficiency of oxygen supply in the entire aerobic zone 2. To meet the dissolved oxygen requirements of the entire aerobic zone 2, preferably, the dissolved oxygen exhibits a gradient distribution, which can be determined based on the dissolved oxygen concentration in the latter part (23). In winter, the dissolved oxygen concentration in the latter part (23) is 0.3-0.5 mg / mL; in summer, the dissolved oxygen concentration in the latter part (23) is 0.2-0.4 mg / L. By using the dissolved oxygen concentration in the latter part (23) of aerobic zone 2 as the basis for determining the dissolved oxygen gradient distribution, it is possible to ensure that the oxygen supply in the entire aerobic zone 2 meets the requirements of the nitrification reaction, while avoiding excessive dissolved oxygen entering the subsequent anoxic zone 3, thereby improving the system's nitrogen removal efficiency and reducing energy consumption.

[0033] Therefore, this application uses the dissolved oxygen concentration in the latter part (23) of aerobic zone 2 as the control benchmark for dissolved oxygen gradient distribution. The aeration intensity (aeration rate) is adjusted based on the ratio of ammonia nitrogen concentration in the middle part (22) of aerobic zone 2 to the influent ammonia nitrogen concentration. A segmented, stepped aeration method is adopted within aerobic zone 2. Simultaneously, the aeration rate is dynamically determined based on seasonal changes in ammonia nitrogen concentration in the latter part (23) of aerobic zone 2. This ensures that the oxygen supply in aerobic zone 2 matches the actual nitrification load in both spatial distribution and temporal regulation. This control method effectively compensates for the decreased activity of nitrifying microorganisms during low-temperature seasons, preventing ammonia nitrogen accumulation in aerobic zone 2. It also prevents over-aeration and reduces energy consumption during high-temperature seasons, thereby improving the overall nitrogen removal efficiency and operational stability of the system.

[0034] To achieve precise control of aeration in the wastewater treatment zone and save energy, the wastewater treatment zone may preferably include: an online monitoring system installed in the middle section 22 and the rear section 23 of the aerobic zone 2 to monitor the ammonia nitrogen and dissolved oxygen concentrations in the aerobic zone 2 in real time; an aeration system that provides oxygen to the aerobic zone 2 and is electrically connected to the online monitoring system; and a control system 13 electrically connected to the online monitoring system and the aeration system for adjusting the aeration rate of the aeration system. The control system 13 can be of an appropriate form, such as a PLC control system, a DCS control system, or a SCADA control system. Preferably, the control system is a PLC control system, which collects data from wastewater treatment and uploads it to the SCADA control system, which then controls the wastewater treatment process.

[0035] Preferably, the online monitoring system is located at the end of the middle section 22 and the end section 23 of the aerobic zone 2; the online monitoring system includes: an online ammonia nitrogen monitor 4, used to monitor the ammonia nitrogen concentration in the middle section 22 and the end section 23 of the aerobic zone 2 in real time; the online ammonia nitrogen monitor 4 adopts an ion-selective electrode method or an ultraviolet spectroscopy ammonia nitrogen analyzer, which can measure the total ammonia (NH4+) in the water in real time. + The ammonia nitrogen concentration (NH3) is fast and adaptable to influent fluctuations. To assess whether the nitrification reaction in the aerobic zone 2 is sufficient, an online ammonia nitrogen monitor 4 can also be installed at the influent end of the aerobic zone 2.

[0036] When the ammonia nitrogen concentration is higher than the set threshold, the speed of blower 6 is increased to improve the oxygen supply intensity; when the dissolved oxygen concentration exceeds the upper limit or is lower than the set target, the opening of the blower 6 duct valve is automatically adjusted to achieve on-demand air volume distribution; thus, closed-loop feedback control is achieved throughout the process to ensure stable, energy-saving and compliant operation of the anaerobic / aerobic / anoxic system.

[0037] The dissolved oxygen online monitoring instrument 5 is used to monitor the dissolved oxygen concentration in the middle section 22 and the rear section 23 of the aerobic zone 2 in real time. The dissolved oxygen online monitoring instrument 5 uses a polarographic or fluorescence method dissolved oxygen online probe and has an automatic temperature compensation function; it is installed by submersion or bracket fixation, with the probe tip placed in the water body of the aerobic zone; the dissolved oxygen online monitoring instrument 5 is also equipped with an automatic air blowing or brushing system to ensure continuous and stable dissolved oxygen concentration data.

[0038] To provide dissolved oxygen to the aerobic zone 2, the aeration system preferably includes: a blower 6, which is disposed outside the aerobic zone 2 and is used to provide oxygen to the aerobic zone 2; an aeration control unit 7, which is electrically connected to the blower 6 and is used to control the aeration rate of the aerobic zone 2; an aeration main pipe 8, which is connected to the blower 6; aeration branch pipes 9, which are respectively disposed in the front section 21, middle section 22 and rear section 23 of the aerobic zone 2 and are connected to the aeration main pipe 8; and aeration heads 10, which are disposed on the aeration plate in the aerobic zone 2, and the densities of the front section 21, middle section 22 and rear section 23 are 40%~50%, 30%~40% and 20%~30% of the total number of aeration heads 10 in the aerobic zone 2, respectively, preferably 50%, 30% and 20%. The density of the aeration heads 10 can be determined based on the ammonia nitrogen content in the wastewater to be treated. Valves are installed on both the aeration main pipe 8 and the aeration branch pipe 9. These valves are all electrically operated linear air flow regulating valves to independently control the aeration flow rate, achieving precise control of the aeration volume in each section of the aerobic zone 2. The electrically operated linear air flow regulating valves are electrically connected to the control system 13. The aeration control unit 7 is a blower frequency converter, which is electrically connected to the control system 13 and the blower 6. It controls the blower frequency converter based on the ammonia nitrogen concentration, thereby controlling the aeration intensity of the blower 6. The valves are electrically connected to the dissolved oxygen online monitoring instrument 5 and the control system 13. The control system 13 adjusts the aeration volume in the aerobic zone 2 and the aeration volume in different sections of the aerobic zone 2 based on the dissolved oxygen concentration, ensuring the oxygen required for the nitrification reaction in the front section 21 while preventing excessively high dissolved oxygen levels from inhibiting denitrification in the anoxic zone 3.

[0039] To further control the wastewater treatment process and achieve differentiated operation and regulation, preferably, the wastewater treatment area may further include: a flow meter installed at the inlet of the wastewater treatment area; an online water quality monitor for monitoring the pH, ammonia nitrogen concentration, and COD concentration of the influent wastewater; and an online water temperature monitor for monitoring the temperature of the influent wastewater. The flow meter, online water quality monitor, and online water temperature monitor are electrically connected to the control system 13 of the wastewater treatment area. The control system 13 adjusts the aeration intensity of the aerobic zone 2 based on the water quality and temperature of the influent wastewater, providing space for adjusting the aeration volume of the aerobic zone 2. This allows the control system 13 to perform disturbance prediction analysis based on influent water quality, quantity, and temperature to predict the required aeration intensity in advance, implement dynamic regulation strategies, and possess the ability to automatically identify changes in operating conditions and intelligently adjust operating parameters, significantly improving the system's adaptability in complex environments and the stability of effluent water quality.

[0040] To further ensure the effectiveness of wastewater treatment, preferably, the wastewater treatment zone further includes: a secondary sedimentation tank 11, located at the end of the wastewater treatment zone and connected to the reoxygenation zone 12 or the anoxic zone 3, used to separate wastewater and sludge; a reoxygenation zone 12, located behind the anoxic zone 3 and connected to both the anoxic zone 3 and the secondary sedimentation tank 11, used to maintain the dissolved oxygen level of the influent to the secondary sedimentation tank 11, preventing sludge from floating due to denitrification under anoxic conditions; and, further, allowing nitrification to occur when ammonia nitrogen is still present in the aerobic zone 2; the reoxygenation zone 12 is equipped with aeration heads, the density of which is the same as the density of the middle section 22 of the aerobic zone 2. The effluent from the anoxic zone 3 can directly enter the secondary sedimentation tank 11 or the reoxygenation zone 12, and the effluent from the reoxygenation zone 12 can then re-enter the secondary sedimentation tank 11. In this process, a portion of the sludge in the secondary sedimentation tank 11 is returned to the anaerobic and anoxic zones of the wastewater treatment area, while the remaining portion is directly discharged. The sludge return or direct discharge requires the control system 13 to automatically adjust the sludge discharge cycle based on water temperature, influent total nitrogen concentration, and effluent water quality. During winter or when influent total nitrogen levels rise, the sludge return ratio in the anaerobic zone 1 and anoxic zone 33 is increased to enhance denitrification capacity.

[0041] The technical advantages of the wastewater treatment method in this application are illustrated below with reference to specific embodiments.

[0042] Example 1: Water treatment capacity 50 m³ / d (1) Test apparatus This embodiment is a pilot-scale anaerobic / aerobic / anoxic / reoxygenation system for treating domestic sewage, with a daily treatment capacity of 50 m³ / d. The biological reactor consists of 12 zones: anaerobic, aerobic, anoxic, and reoxygenation. The volume ratio of the biological reactors is 1:2:4:0.5, with the anaerobic zone at 5 m³, the aerobic zone at 10 m³, the anoxic zone at 20 m³, and the reoxygenation zone at 2.5 m³. A secondary sedimentation tank with a volume of 6 m³ is also included.

[0043] The aerobic zone 2 employs the segmented aeration system design and airflow control strategy proposed in this invention: aeration heads 10 with densities of 50%, 30%, and 20% are respectively deployed in the front section 21, middle section 22, and rear section 23 of the aerobic zone, combined with independent air ducts and electric linear airflow regulating valves to form an airflow distribution control system. Each aeration branch is connected to a PLC control system, and real-time feedback signals are provided by an online dissolved oxygen (DO) meter at the end. The air source is configured as a 7.5kW blower 6, using frequency conversion control to achieve intelligent adjustment of the total airflow based on NH3-N concentration feedback.

[0044] In addition, dissolved oxygen (DO) and ammonia nitrogen (NH3-N) online monitoring instruments are installed in the middle and end sections of the aerobic zone 23, and flow meters are installed at the inlet and outlet. Through the feedback control logic proposed in this application, the above instrument signals are linked with the PLC control system to control the frequency of the blower 6 and the aeration volume of each zone, forming a stable oxygen gradient distribution and ensuring the rational operation of the microbial reaction zone.

[0045] (2) Operating conditions The system operated continuously for 90 days under natural outdoor climatic conditions, all during winter. During this period, the water temperature fluctuated between 10 and 18°C, representing a typical low-temperature, unsteady-state operating condition. No additional external carbon sources or chemical phosphorus removal agents were added throughout the experiment. Wastewater treatment relied solely on the control system, aeration system, online water quality monitor, online water temperature monitor, and flow meter described in this application for operational adjustments.

[0046] During the initial operation, the initial aeration distribution ratio and target control values ​​were set based on the influent load and the volume of the reaction tank: the dissolved oxygen target for the aerobic rear section (section 23) was 0.3~0.5 mg / L, the ammonia nitrogen trigger threshold was 0.5~1.0 mg / L, the sludge retention time (SRT) was set to 25 days, and the sludge return ratio in both the anaerobic and anoxic zones was 100%. The system has automatic alarm and automatic airflow redistribution functions to ensure that the aeration intensity and zone airflow can be adjusted in real time when the water temperature changes or the load fluctuates, thereby stabilizing the microbial reaction rate and denitrification effect.

[0047] (3) Results of the operation During continuous operation, the wastewater treatment method described in this application demonstrated good treatment capacity and stability. The main effluent water quality indicators are as follows: The average total nitrogen (TN) in the effluent was 5.8 mg / L; Total phosphorus (TP) was 0.15 mg / L; Ammonia nitrogen (NH3-N) remained consistently below 1 mg / L; The COD concentration in the effluent is 25 mg / L; All meet the Class A standard of the "Pollutant Discharge Standard for Urban Wastewater Treatment Plants".

[0048] In terms of energy consumption, the aeration energy consumption per unit volume of water in the wastewater treatment method of this application is approximately 0.25 kWh / m³, which is about 19% lower than that of the traditional A² / O process. In addition, due to the adoption of intelligent DO control and dynamic air volume distribution, the production of excess sludge is reduced by about 21% compared with the A² / O process, saving sludge treatment and disposal costs.

[0049] Under specific disturbance conditions, such as a sudden increase of 20% in the influent flow rate and a drop in water temperature to 10℃, the system can automatically increase the frequency of blower 6 from 30Hz to 42Hz and adjust the air volume distribution ratio of the downstream section 23. The DO of the downstream section 23 is stable below 0.5mg / L, and the total nitrogen fluctuation in the effluent is controlled within 1mg / L. This indicates that the "multi-point monitoring - linkage adjustment - feedback control" mechanism proposed in this invention has good environmental adaptability and dynamic response capability.

[0050] Example 2: Water treatment capacity 100m³ / d (1) Test apparatus This embodiment is a pilot-scale system of an anaerobic / aerobic / anoxic / reoxygenation process with a treatment capacity of 100 m³ / d. The bioreactor is divided into anaerobic zone 1, aerobic zone 2, anoxic zone 3, and reoxygenation zone. The volume of the bioreactor is configured in a ratio of 1:1.5:5:0.5, with 8 m³ for the anaerobic zone, 12 m³ for the aerobic zone, 40 m³ for the anoxic zone, and 4 m³ for the reoxygenation zone. The secondary sedimentation tank has a volume of 10 m³.

[0051] The aerobic zone adopts the zonal aeration configuration and airflow control mechanism proposed in this application. Aerobic zone 2 is divided into a front section 21, a middle section 22, and a rear section 23 according to the water flow direction. The density of aeration heads 10 accounts for 50%, 30%, and 20% of the total aeration devices in the aerobic zone, respectively. Each section of the duct is equipped with an independent electric linear airflow regulating valve and connected to a PLC control system. Real-time feedback signals are provided by the DO and NH3-N online instruments in the rear section 23, enabling on-demand oxygen supply and spatial gradient adjustment throughout the entire process.

[0052] Equipped with an 11kW permanent magnet variable frequency blower, the system monitors parameters including DO, ammonia nitrogen, inlet water temperature, water volume, and pH online. All data is collected by the PLC control system and uploaded to the remote SCADA system.

[0053] (2) Operating conditions The system operated continuously for 120 days under summer conditions, during which the ambient water temperature fluctuated between 20 and 30°C. Initial operating parameters were set as follows: target value of 23DO in the downstream section of 0.2–0.4 mg / L, ammonia nitrogen trigger value of 0.3–0.6 mg / L, system sludge age (SRT) of 20 days, and sludge return ratio of 100% in both the anaerobic and anoxic zones.

[0054] During operation, the system remained stable under design load for an extended period, while also simulating common summer abnormal conditions—a decrease in influent organic matter concentration, a drop in total nitrogen concentration, and a sudden increase in water volume caused by heavy rainfall. During this disturbance phase, the system's influent COD dropped to approximately 160 mg / L, the ammonia nitrogen concentration dropped to 15 mg / L, and the water volume increased instantaneously by 30%.

[0055] In response to this complex operating condition of low carbon and nitrogen loads plus a sudden increase in flow rate, the control system in this application quickly identifies changes in operating status, automatically reduces the blower frequency to 26Hz, and simultaneously adjusts the opening of the aeration valves in the front section 21 and the rear section 23 to achieve spatial redistribution of oxygen and maintain a stable dissolved oxygen level in the reaction zone.

[0056] (3) Results of the operation Continuous operation and disturbance test results show that the system's effluent water quality is excellent and stable. The total nitrogen (TN) in the effluent remained stable at 2 mg / L over a long period. Total phosphorus (TP) was maintained at 0.1 mg / L; The concentration of ammonia nitrogen (NH3-N) remained below 0.5 mg / L for an extended period. The COD concentration in the effluent was maintained at around 20 mg / L.

[0057] All indicators meet the Class A requirements of the "Urban Wastewater Treatment Plant Pollutant Discharge Standard", and it still has strong steady-state control capabilities, especially under the conditions of high temperature in summer and load fluctuations during the rainy season.

[0058] The unit water treatment aeration energy consumption is maintained at 0.23 kWh / m³, which is about 23% more energy-efficient than the traditional A / O process; thanks to the optimized oxygen supply control and stable microbial activity, the excess sludge production is reduced by about 25% compared to the traditional process.

[0059] In the disturbance test, facing the adverse conditions of short-term water quality load decline and water volume increase, the aeration strategy was stably adjusted through the feedback mechanism. The 23DO in the downstream stage was always maintained in the range of 0.2~0.4mg / L, and the maximum fluctuation of effluent TN did not exceed 2mg / L, which proves that the wastewater treatment method in this application has extremely strong dynamic adjustment capability and operational robustness.

[0060] The preferred embodiments of this application have been described in detail above. However, this application is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, and these simple modifications all fall within the protection scope of this application.

[0061] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not describe the various possible combinations separately.

[0062] Furthermore, various different embodiments of this application can be combined in any way, as long as they do not violate the spirit of this application, they should also be regarded as the content disclosed by this invention.

Claims

1. A wastewater treatment method, characterized in that, The wastewater treatment method includes: wastewater is treated in a wastewater treatment zone, which includes an anaerobic zone (1), an aerobic zone (2) and an anoxic zone (3) connected in sequence. The aerobic zone (2) includes a front section (21), a middle section (22) and a rear section (23). In the aerobic zone (2), the ammonia nitrogen concentration and dissolved oxygen concentration of the wastewater in the middle section (22) and the rear section (23) of the aerobic zone (2) are monitored in real time, and the aeration rate of the aerobic zone (2) is adjusted in real time according to the ammonia nitrogen concentration of the aerobic zone (2) in order to accurately control the wastewater treatment process.

2. The wastewater treatment method according to claim 1, characterized in that, The aeration rate of the aerobic zone (2) is determined based on the ammonia nitrogen concentration in the latter part (23) of the aerobic zone (2); In winter, the ammonia nitrogen concentration in the aerobic zone (2) is 0.5-1 mg / mL; in summer, the ammonia nitrogen concentration in the aerobic zone (2) is 0.3-0.6 mg / mL.

3. The wastewater treatment method according to claim 1, characterized in that, The aeration rate of the aerobic zone (2) and / or the rear section (23) is determined based on the ammonia nitrogen concentration of the middle section (22); When the ammonia nitrogen concentration in the middle section (22) exceeds the ammonia nitrogen concentration threshold, the aeration rate is increased to ensure that the nitrification reaction is stably completed in the aerobic zone (2). Preferably, the ammonia nitrogen concentration threshold is such that the ammonia nitrogen concentration in the middle section (22) is greater than 1 / 3 of the ammonia nitrogen concentration in the influent of the aerobic zone (2).

4. The wastewater treatment method according to claim 1, characterized in that, The dissolved oxygen in the front (21), middle (22) and rear (23) sections of the aerobic zone (2) is distributed in a gradient.

5. The wastewater treatment method according to claim 4, characterized in that, The gradient distribution of dissolved oxygen is determined based on the dissolved oxygen concentration in the latter section (23); In winter, the dissolved oxygen concentration of the latter section (23) is 0.3-0.5 mg / mL; in summer, the dissolved oxygen concentration of the latter section (23) is 0.2-0.4 mg / L.

6. The wastewater treatment method according to claim 1, characterized in that, The wastewater treatment area also includes: An online monitoring system is installed in the middle (22) and rear (23) sections of the aerobic zone (2) to monitor the ammonia nitrogen and dissolved oxygen concentrations of the aerobic zone (2) in real time. An aeration system that provides oxygen to the aerobic zone (2) and is electrically connected to the online monitoring system; A control system (13) is electrically connected to the online monitoring system and the aeration system and is used to adjust the aeration volume of the aeration system.

7. The wastewater treatment method according to claim 6, characterized in that, The online monitoring system is located at the end of the middle section (22) and the rear section (23) of the aerobic zone (2); the online monitoring system includes: An online ammonia nitrogen monitor (4) is used to monitor the ammonia nitrogen concentration in the middle (22) and rear (23) sections of the aerobic zone (2) in real time; The dissolved oxygen online monitoring instrument (5) is used to monitor the dissolved oxygen concentration in the middle section (22) and the rear section (23) of the aerobic zone (2) in real time.

8. The wastewater treatment method according to claim 6, characterized in that, The aeration system includes a blower (6), which is located outside the aerobic zone (2) and is used to provide oxygen to the aerobic zone (2); An aeration control unit (7) is electrically connected to the blower (6) and is used to control the aeration rate of the aerobic zone (2). Aeration main pipe (8) is connected to the blower (6); Aeration branch pipe (9) is respectively installed in the front section (21), middle section (22) and rear section (23) of the aerobic zone (2) and is connected to the aeration main pipe (8); Aeration head (10) is set in the aerobic zone (2), and the density of the front section (21), middle section (22) and rear section (23) is 40%~50%, 30%~40% and 20%~30% of the total number of aeration heads (10) in the aerobic zone (2), respectively.

9. The wastewater treatment method according to claim 1, characterized in that, The wastewater treatment area also includes: A flow meter is installed at the inlet end of the wastewater treatment area. An online water quality monitoring instrument is used to monitor the pH, ammonia nitrogen concentration, and COD concentration of wastewater influent. An online water temperature monitor is used to monitor the water temperature of the wastewater inlet. The flow meter, water quality online monitor and water temperature online monitor are electrically connected to the control system (13) of the wastewater treatment area. The control system (13) adjusts the aeration intensity of the aerobic zone (2) according to the water quality and water temperature of the wastewater inlet, so as to provide space for the adjustment of the aeration volume of the aerobic zone (2).

10. The wastewater treatment method according to claim 1, characterized in that, The wastewater treatment area also includes: Secondary sedimentation tank (11), which is located at the end of the wastewater treatment area, is used to separate wastewater and sludge; The reoxygenation zone (12) is located behind the anoxic zone (3) in the wastewater treatment area and is connected to the anoxic zone (3) and the secondary sedimentation tank (11). It is used to keep the wastewater in the secondary sedimentation tank (11) in an aerobic state and prevent sludge from floating. In this process, part of the sludge in the secondary sedimentation tank (11) is returned to the anaerobic zone (1) and the anoxic zone (3), while the other part is directly discharged.

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