Carbon source multi-point dynamic dosing method for sewage treatment AAO process

Abstract

This invention provides a multi-point dynamic carbon source addition method for AAO (Automatic Anoxic) processes in wastewater treatment. Addressing the issues of idle denitrification function in the second anoxic zone, inefficient carbon source addition, low utilization rate, and poor resistance to water quality fluctuations in dual-anoxic processes, this invention adds a second addition point after the inlet of the second anoxic zone, in addition to the existing addition point after the inlet of the first anoxic zone. Maintaining a constant total carbon source addition in the anoxic section, the denitrification function of the second anoxic zone is activated by redistributing the carbon source flow rate. Simultaneously and collaboratively controlling process parameters such as dissolved oxygen and sludge age, a closed-loop control logic of influent feedforward and effluent feedback is employed to achieve dynamic and precise addition. Experimental results show that the average TN removal rate in the second anoxic zone reaches 13.0%, and the total nitrogen in the effluent is stably controlled at 6.67 mg / L, which is better than the discharge standard. Carbon source utilization efficiency is significantly improved. This method requires no large-scale process modification, has strong resistance to water quality fluctuations, and provides a reliable technical path for the low-carbon and stable operation of wastewater treatment plants.

Description

Technical Field

[0001] This invention relates to the field of biological denitrification technology in urban wastewater treatment, and particularly to a method for dynamic multi-point addition of carbon sources in an AAO process for wastewater treatment. Background Technology

[0002] The Bardenpho process, with its high denitrification efficiency and stable operation, has become one of the mainstream technologies for upgrading and retrofitting urban wastewater treatment plants in my country. This process, through the setting of two-stage anoxic and aerobic units in series, theoretically can fully utilize the carbon source in the influent to achieve deep denitrification. However, in actual engineering operation, most wastewater treatment plants still use the traditional method of centralized single-point addition of carbon source at the inlet of the first anoxic zone, which has three major drawbacks. First, excessive addition of carbon source in the first anoxic zone results in unused, easily degradable carbon source entering the subsequent aerobic zone and being oxidized and decomposed by heterotrophic bacteria, not only wasting carbon source but also increasing aeration energy consumption in the aerobic zone. Second, due to the lack of usable carbon source in the second anoxic zone, the activity of denitrifying bacteria is inhibited, the denitrification function is basically lost, and the system's denitrification volume is not fully utilized. Third, the static addition mode cannot adapt to fluctuations in influent water quality and quantity. To ensure that the total nitrogen in the effluent meets the standards, excessive carbon source needs to be added in subsequent deep treatment units such as denitrification deep bed filters, further increasing operating costs.

[0003] While existing technologies include research on multi-point carbon source addition in AAO processes, most focus on segmented addition within the first anoxic zone, neglecting the functional activation of the second anoxic zone unique to the Bardenpho process. Furthermore, they generally improve denitrification efficiency by increasing the total carbon source dosage, failing to achieve total carbon source control and efficient utilization. Simultaneously, existing technologies do not coordinate carbon source addition with key process parameters such as dissolved oxygen, sludge age, and recirculation ratio, resulting in large fluctuations in carbon source utilization and a significant decrease in denitrification efficiency under low-temperature conditions, failing to meet the long-term, stable, and low-carbon operation requirements of wastewater treatment plants. Summary of the Invention

[0004] This invention proposes a multi-point dynamic carbon source addition method for the AAO process in wastewater treatment. Without increasing the total carbon source addition in the anoxic zone, it activates the denitrification function of the second anoxic zone. Through coordinated regulation of process parameters and closed-loop intelligent control, it improves the overall denitrification efficiency and resistance to water quality fluctuations of the system, reduces the carbon source consumption of the deep treatment unit, and achieves the synergistic goals of improving quality, reducing consumption, and increasing efficiency.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for dynamic multi-point carbon source addition in an AAO (Anoxic-Aerobic) wastewater treatment process, specifically for the Bardenpho dual-anoxic dual-aerobic AAO process, includes the following steps: Step 1: Set up the first carbon source addition point after the inlet of the first anoxic zone, and add an independent second carbon source addition point after the inlet of the second anoxic zone to construct a dual-point linkage addition system. Step 2: Keep the total carbon source addition flow rate of the anoxic section unchanged, transfer 20%-25% of the addition flow rate of the original first carbon source addition point to the second carbon source addition point, and use a multi-point linkage method to add carbon source to the two-stage anoxic areas in stages. Step 3: During the carbon source addition process, simultaneously and collaboratively control the dissolved oxygen in the aerobic zone, the sludge age in the system, the sludge return ratio, and the mixed liquor return ratio to activate the denitrification and nitrogen removal function in the second anoxic zone. Step 4: Dynamically adjust the carbon source allocation ratio based on the water quality monitoring data of each treatment unit, while reducing the amount of carbon source added to subsequent advanced treatment units.

[0006] Furthermore, in step 1, water quality monitoring points are set up at the inlet of the first anoxic zone, the outlet of the first anoxic zone, the inlet of the second anoxic zone, the outlet of the second anoxic zone, the outlet of the secondary sedimentation tank, and the outlet of the denitrification tank to monitor COD and TN concentrations in real time, while also monitoring the dissolved oxygen concentration and mixed liquor sludge concentration at the end of the aerobic zone.

[0007] Furthermore, in step 2, the carbon source is a sodium acetate solution with a mass concentration of 20-30 g / L, which is stirred and mixed evenly before being added and then delivered to each addition point by a metering pump.

[0008] Furthermore, in step 2, the first anoxic zone completes the main denitrification nitrogen removal, with a TN removal rate of 20.0%-22.2%, contributing 57.8%-58.0% to the total TN removal along the process.

[0009] Furthermore, in step 2, the second anoxic zone achieves supplemental denitrification, with a TN removal rate of 12.7%-13.3%, an average removal rate of 13.0%, and a contribution of 26.6%-29.7% to TN removal along the process.

[0010] Furthermore, in step 3, the dissolved oxygen concentration at the end of the aerobic zone is controlled to be 0.5-1.5 mg / L, the sludge age of the system is 12-18 days, the sludge return ratio is 50%-100%, and the mixed liquor return ratio is 150%-250%.

[0011] Furthermore, in step 4, the amount of carbon source added to the subsequent high-efficiency sedimentation tank is reduced by 9.4% compared to before optimization, the addition flow rate is controlled within the range of 200-400L / h, and the addition amount is adjusted in conjunction with the TN concentration of the secondary sedimentation tank effluent.

[0012] Furthermore, in step 4, dynamic differential control is carried out based on the differences in carbon source utilization rates of different parallel pools. For pools with carbon source utilization rates below 80%, the amount added at the second carbon source addition point is reduced by 10%-15%.

[0013] Furthermore, in step 4, a closed-loop control logic of feedforward influent TN load and feedback influent TN is adopted. The total carbon source dosage in the anoxic section is adjusted in real time according to the TN concentration of the influent, and the carbon source distribution ratio at each dosage point is finely adjusted according to the TN concentration of the effluent. The carbon source utilization rate is calculated by multiplying the TN removal amount by the carbon-nitrogen ratio and then dividing by the carbon source dosage. The theoretical carbon-nitrogen ratio TN:COD is 1:3-4.

[0014] Furthermore, in step 4, the total nitrogen in the system effluent is stably controlled below 6.67 mg / L; when the water temperature is below 15℃ in winter, the addition ratio of the second carbon source is increased by 3%-5% to ensure denitrification efficiency under low-temperature conditions.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The nitrogen removal effect is significantly improved and stabilized. The denitrification function of the second anoxic zone of the Bardenpho process was successfully activated, and the total TN removal rate of the system increased by more than 15% compared with that before optimization. The total nitrogen in the effluent was stably controlled below 6.67 mg / L, which is far better than the national standard, ensuring the safety of the effluent quality.

[0016] 2. Carbon source utilization rate has been significantly improved. Through the redistribution and segmented utilization of total carbon source, combined with the coordinated control of process parameters, the overall carbon source utilization rate has been increased by more than 25%. The Dongchi system has achieved carbon source utilization exceeding the theoretical value, and the carbon source addition amount in the deep treatment unit has been reduced by 9.4%.

[0017] 3. Outstanding economic benefits. After optimization, approximately 301.5 tons of carbon source are saved annually. Combined with savings in electricity and equipment maintenance costs, the direct annual cost savings are approximately 155,138 yuan. Further dynamic optimization of the West Pool could result in additional annual cost savings of approximately 4,282 yuan, with an investment payback period of less than 3 months, demonstrating significant economic benefits.

[0018] 4. Strong anti-interference capability. It adopts a closed-loop control logic of influent feedforward and effluent feedback, which can adapt to fluctuations in influent water quality and quantity in real time. Even under low temperature conditions in winter, it can still maintain a stable denitrification effect by adjusting the carbon source distribution ratio and sludge age.

[0019] 5. High promotional value. This method does not require large-scale modification of existing processes. It can be achieved simply by adding dosing points, installing online monitoring equipment, and optimizing operating parameters. It is simple to operate, stable in operation, and can be directly promoted and applied to all urban wastewater treatment plants using the dual-anoxic AAO process, providing a replicable technical paradigm and management experience for low-carbon operation in the industry. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1This is a graph showing the variation of TN concentration along the Dongchi system. Figure 2 This is a graph showing the trend of TN concentration changes in Dongchi on December 5th. Figure 3 This is a graph showing the variation of TN concentration along the Xichi system. Figure 4 This is a graph showing the trend of TN concentration changes in Xichi on December 5th. Figure 5 Comparison of TN removal effects between the east and west pools in the second anoxic zone; Figure 6 This is a graph showing the COD concentration changes in the Dongchi system. Figure 7 This is a graph showing the COD concentration changes in the Xichi system. Figure 8 This is a block diagram of the dynamic carbon source addition control logic of the present invention. Detailed Implementation

[0021] The specific embodiments of the present invention will be further described in detail with reference to the accompanying drawings.

[0022] This invention is applied to the second phase of the Chengnan Wastewater Treatment Plant in Wuhu City. The project has a designed treatment capacity of 100,000 m³ / d, with the biological system divided into two independent parallel series, an east pool and a west pool, each with a single series treatment capacity of 50,000 m³ / d. The main process adopts the Bardenpho dual-anoxic dual-aerobic process, followed by a radial flow secondary sedimentation tank, a magnetic coagulation sedimentation tank, a denitrification deep bed filter, and a sodium hypochlorite disinfection unit. Before optimization, the carbon source was a 25 g / L sodium acetate solution, added only at a single point after the inlet of the first anoxic zone at a flow rate of 450 L / h. The carbon source flow rate at the subsequent high-efficiency sedimentation tank was 200-800 L / h. The second anoxic zone had virtually no denitrification function. The total TN removal rate of the system was approximately 30%, and the effluent TN fluctuated significantly, frequently approaching the discharge standard limit of 8 mg / L.

[0023] This invention adds a second carbon source dosing point after the inlet of the second anoxic zone. The carbon source dosing pump adopts the Milton Roy GM series mechanical diaphragm metering pump, with a single pump flow range of 0-500 L / h and a metering accuracy of ±1%. It is equipped with a frequency converter to realize continuous flow adjustment. Hach NPW-160 online TN monitors and Hach CODmaxII online COD monitors are installed at the inlet of the first anoxic zone, the outlet of the first anoxic zone, the inlet of the second anoxic zone, the outlet of the second anoxic zone, the outlet of the secondary sedimentation tank, and the outlet of the denitrification tank, respectively. A Hach LDO dissolved oxygen monitor and a Hach MLSS sludge concentration monitor are installed at the end of the aerobic zone. All monitoring data are transmitted in real time to the plant's Siemens S7-300 PLC control system.

[0024] During system startup, the total carbon source addition flow rate in the anoxic zone remains constant at 500 L / h. The addition flow rate at the first carbon source addition point is adjusted to 350 L / h, and the addition flow rate at the second carbon source addition point is set to 150 L / h. Simultaneously, the dissolved oxygen concentration at the end of the aerobic zone is controlled at 1.0 ± 0.2 mg / L, the system sludge age is controlled at 15 days, the sludge return ratio is controlled at 70%, and the mixed liquor return ratio is controlled at 200%. During operation, wastewater first enters the first anoxic zone. Under the action of the carbon source added at the first carbon source addition point, denitrifying bacteria reduce approximately 60% of the nitrate nitrogen in the influent to nitrogen gas, completing the main denitrification process. Figure 1 and Figure 3 As shown, the TN removal rate in the first anoxic zone is 20.0%-22.2%, contributing 57.8%-58.0% to the total TN removal along the process. After nitrification in the first aerobic zone, the wastewater enters the second anoxic zone. Under the action of the carbon source added at the second carbon source addition point, the residual nitrate nitrogen is further removed by denitrification. Figure 2 and Figure 4 As shown, the TN removal rate in the second anoxic zone reached 12.7%-13.3%, with an average removal rate of about 13.0%, contributing 26.6%-29.7% to the TN removal along the process, and the denitrification function was effectively activated.

[0025] Since the first phase of the biochemical pool at the Chengnan Wastewater Treatment Plant has been under maintenance since October 29, the water quality data for November has been greatly affected by external factors. Therefore, the TN concentration data from December 5, 2024, was selected for analysis.

[0026] Water quality data from Dongchi Lake on December 5th were selected for analysis:

[0027] Similarly, water quality data from Xichi Lake on December 5th were selected for analysis:

[0028] like Figure 5 As shown, after one month of continuous operation, the TN removal in the second anoxic zone of both the East and West ponds stabilized between 0.5-1.3 mg / L, with the East pond showing better denitrification; on November 20th and 28th, the TN removal in the East pond was significantly higher than that in the West pond. Figure 6 and Figure 7As shown, the COD concentration at the outlet of the second anoxic zone in the East Pool was lower than that at the inlet, indicating efficient utilization of the carbon source and actual carbon source consumption lower than the theoretical value. Conversely, the COD concentration at the outlet of the second anoxic zone in the West Pool was higher than that at the inlet, suggesting incomplete utilization of the carbon source and room for further optimization. Based on these monitoring results, the control system automatically and dynamically adjusted the dosage at the second carbon source addition point in the West Pool, reducing the dosage by 15%, i.e., adjusting the addition flow rate to 127.5 L / h. The dosage in the East Pool remained unchanged. After the adjustment, the carbon source utilization rate in the West Pool increased to over 85%, without affecting the overall nitrogen removal effect of the system. After optimization, the carbon source addition flow rate in the subsequent high-efficiency sedimentation tank was reduced to 200-400 L / h, saving 9.4% of the dosage compared to before optimization.

[0029] To address fluctuations in influent water quality, the system employs a feedforward feedback closed-loop control logic. When the influent TN concentration is below 12 mg / L, the total carbon source dosage in the anoxic zone is reduced by 5%, and the dosage ratio between the first and second anoxic zones is adjusted to 7:3. When the influent TN concentration is between 12 and 15 mg / L, the total dosage remains unchanged, and the dosage ratio is adjusted to 6.5:3.5. When the influent TN concentration is above 15 mg / L, the total dosage is increased by 5%, and the dosage ratio is adjusted to 6:4. Simultaneously, the carbon source dosage in the high-efficiency sedimentation tank is fine-tuned based on the effluent TN concentration from the secondary sedimentation tank. When the effluent TN is above 7 mg / L, the dosage in the high-efficiency sedimentation tank is increased by 10%; when the effluent TN is below 6 mg / L, the dosage is reduced by 10%. In winter, when the water temperature is below 15℃, the activity of denitrifying bacteria decreases, and the system automatically increases the carbon source dosage ratio in the second anoxic zone by 5%, while extending the sludge age to 18 days to ensure denitrification efficiency under low-temperature conditions.

[0030] Monitoring data from three consecutive months of operation showed that the system's total TN removal rate remained stable at 34.6%-38.2%, and the total nitrogen in the effluent was consistently controlled at 6.2-6.9 mg / L, with an average of 6.67 mg / L, which is better than the national discharge standard of 8 mg / L. The carbon source utilization rate in the second anoxic zone of the East Pool reached over 110%, with actual carbon source consumption lower than the theoretical value; the carbon source utilization rate in the West Pool increased to over 85%, and the overall carbon source utilization rate throughout the process improved by more than 25% compared to before optimization.

[0031] The working principle of this invention is to add carbon source in stages to two-stage anoxic zones, achieving tiered utilization of carbon source and avoiding carbon source waste caused by excessive addition in the first anoxic zone and oxidation loss in the aerobic zone. Simultaneously, it activates the previously idle denitrification function of the second anoxic zone, increasing the system's effective nitrogen removal volume and improving overall nitrogen removal efficiency. By synergistically controlling process parameters such as dissolved oxygen and sludge age, an optimal growth and metabolic environment is created for denitrifying bacteria, further improving carbon source utilization efficiency. Employing feedforward feedback closed-loop control logic, the carbon source addition amount can be matched in real-time with the influent water quality and system operating status, significantly enhancing the system's resistance to water quality fluctuations, thereby reducing the amount of carbon source replenishment required in subsequent advanced treatment units, achieving efficient utilization of carbon source throughout the entire process and low-carbon, stable operation of the system.

[0032] Economic assessment: Before this study, the carbon source (sodium acetate) was added to the first anoxic zone at a concentration of approximately 25 g / L and a flow rate of approximately 450 L / h. The flow rate at the high-efficiency sedimentation tank was approximately 200-800 L / h (depending on the effluent from the secondary sedimentation tank). In this study, the concentration was approximately 25 g / L, the flow rate was 350 L / h in the first anoxic zone, 150 L / h in the second anoxic zone, and the flow rate at the high-efficiency sedimentation tank was approximately 200-400 L / h (depending on the effluent from the secondary sedimentation tank).

[0033] Because the dredging of the first-phase biological treatment pond in the plant area was carried out on October 29, and the carbon source was added to the second anoxic zone starting on November 5, the carbon source addition amount in December was selected for comparative analysis:

[0034] If we subtract the amount of carbon source added in the anoxic section, the required addition amounts for the second-phase high-efficiency sedimentation tank are: 17498 kg / d - 450 L / h × 24h × 25 g / L = 17228 kg / d; 15909 kg / d - (350 + 150) L / h × 24h × 25 g / L = 15609 kg / d. That is, after adding the carbon source addition point, the carbon source addition amount for the second-phase high-efficiency sedimentation tank is reduced by approximately 9.4% compared to before (17228 - 15609) / 17228.

[0035] The total amount of carbon source added in the second phase in 2024 was 4,735,190 kg. The estimated amount of carbon source added in the anoxic section was approximately 450 L / h × 24h × 25 g / L × 365d = 98,550 kg. Therefore, the amount of carbon source added in the second phase of the high-efficiency sedimentation tank was 4,735,190 kg - 98,550 kg = 4,636,640 kg. After adding the carbon source addition point, the annual carbon source addition amount can be saved (the carbon source addition in the high-efficiency sedimentation tank is mainly from November to April): 4,636,640 kg × 9.4% × (8 / 12) + (350 + 150 - 450) L / h × 24h × 25 g / L × 365d ≈ 301,512 kg ≈ 301.5 tons.

[0036] Currently, the carbon source utilization rate in the second anoxic zone of West Lake is low, and the dosage can be reduced by 10-15% in the future; while the carbon source utilization rate in East Lake is high, and the current status can be maintained, and the dosage in the first anoxic zone can be appropriately optimized.

[0037] The theoretical amount that can still be saved is: The energy saving in the second hypoxic zone of Xichi is: 150L / h × 15% = 22.5L / h; Daily energy saving: 22.5L / h × 24h = 540L / d; Carbon source concentration: 25,000 mg / L = 25 g / L; Daily carbon savings: 540L × 25g / L = 13,500g = 13.5kg / day; Annual carbon savings: 13.5 kg / d × 365 d = 4,927.5 kg ≈ 4.93 tons.

[0038] Economic benefit estimation: Compared with the economic benefit estimate before the experiment:

[0039] Given the low carbon source utilization rate in the second anoxic zone of Xichi, if this section is optimized in the future, reducing the dosage by 10-15%, the theoretical economic benefit estimate would be:

[0040] The above calculations show that, compared with the previous experiment, the multi-point carbon source addition method saves about 155,138 yuan per year. If the amount of carbon source added is dynamically optimized and the amount of carbon source in the second anoxic zone of Xichi is reduced by 15%, the annual cost can be further reduced by about 4,282 yuan.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for dynamic multi-point addition of carbon sources in an AAO (Automatic Atomic Oxidation) process for wastewater treatment, characterized in that, The Bardenpho dual-anoxic dual-aerobic AAO process includes the following steps: Step 1: Set up the first carbon source addition point after the inlet of the first anoxic zone, and add an independent second carbon source addition point after the inlet of the second anoxic zone to construct a dual-point linkage addition system. Step 2: Keep the total carbon source addition flow rate of the anoxic section unchanged, transfer 20%-25% of the addition flow rate of the original first carbon source addition point to the second carbon source addition point, and use a multi-point linkage method to add carbon source to the two-stage anoxic areas in stages. Step 3: During the carbon source addition process, simultaneously and collaboratively control the dissolved oxygen in the aerobic zone, the sludge age in the system, the sludge return ratio, and the mixed liquor return ratio to activate the denitrification and nitrogen removal function in the second anoxic zone. Step 4: Dynamically adjust the carbon source allocation ratio based on the water quality monitoring data of each treatment unit, while reducing the amount of carbon source added to subsequent advanced treatment units.

2. The method for multi-point dynamic carbon source addition in an AAO process for wastewater treatment as described in claim 1, characterized in that, In step 1, water quality monitoring points are set up at the inlet of the first anoxic zone, the outlet of the first anoxic zone, the inlet of the second anoxic zone, the outlet of the second anoxic zone, the outlet of the secondary sedimentation tank, and the outlet of the denitrification tank to monitor COD and TN concentrations in real time, while also monitoring the dissolved oxygen concentration and mixed liquor sludge concentration at the end of the aerobic zone.

3. The method for multi-point dynamic carbon source addition in an AAO process for wastewater treatment as described in claim 1, characterized in that, In step 2, the carbon source is a sodium acetate solution with a mass concentration of 20-30 g / L. Before addition, the solution is stirred and mixed evenly and then delivered to each addition point by a metering pump.

4. The method for multi-point dynamic carbon source addition in an AAO process for wastewater treatment as described in claim 1, characterized in that, In step 2, the first anoxic zone completes the main denitrification nitrogen removal, with a TN removal rate of 20.0%-22.2%, contributing 57.8%-58.0% to the total TN removal along the process.

5. The method for multi-point dynamic carbon source addition in an AAO process for wastewater treatment as described in claim 1, characterized in that, In step 2, supplemental denitrification is achieved in the second anoxic zone, with a TN removal rate of 12.7%-13.3%, contributing 26.6%-29.7% to the total TN removal along the process.

6. The method for multi-point dynamic carbon source addition in an AAO process for wastewater treatment as described in claim 1, characterized in that, In step 3, the dissolved oxygen concentration at the end of the aerobic zone is controlled to be 0.5-1.5 mg / L, the sludge age of the system is 12-18 days, the sludge return ratio is 50%-100%, and the mixed liquor return ratio is 150%-250%.

7. The method for multi-point dynamic carbon source addition in an AAO process for wastewater treatment as described in claim 1, characterized in that, In step 4, the amount of carbon source added to the subsequent high-efficiency sedimentation tank is reduced by 9.4% compared with the previous step, the addition flow rate is controlled in the range of 200-400L / h, and the addition amount is adjusted in conjunction with the TN concentration of the secondary sedimentation tank effluent.

8. The method for multi-point dynamic carbon source addition in an AAO process for wastewater treatment as described in claim 1, characterized in that, In step 4, dynamic differential control is carried out based on the differences in carbon source utilization rates of different parallel pools. For pools with carbon source utilization rates below 80%, the amount added at the second carbon source addition point is reduced by 10%-15%.

9. The method for multi-point dynamic carbon source addition in an AAO process for wastewater treatment as described in claim 1, characterized in that, In step 4, a closed-loop control logic of feedforward in the influent TN load and feedback in the effluent TN is adopted. The total carbon source dosage in the anoxic section is adjusted in real time according to the influent TN concentration, and the carbon source distribution ratio at each dosage point is finely adjusted according to the effluent TN concentration. The formula for calculating carbon source utilization rate is TN removal amount multiplied by carbon-nitrogen ratio and then divided by carbon source addition amount. The theoretical carbon-nitrogen ratio TN:COD is 1:3-4.

10. The method for multi-point dynamic carbon source addition in an AAO process for wastewater treatment as described in claim 1, characterized in that, In step 4, the total nitrogen in the system effluent is stably controlled below 6.67 mg / L; when the water temperature is below 15℃ in winter, the addition ratio of the second carbon source is increased by 3%-5% to ensure the denitrification efficiency under low temperature conditions.

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