Optimization of nitrogen removal performance of multistage AO step-feed process for a municipal wastewater treatment plant

ZHU Zhuo; DAN Qiongpeng; ZHANG Xiongfei; PANG Bo; PENG Yongzhen

doi:10.13205/j.hjgc.202509001

Volume 43 Issue 9

Sep. 2025

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ZHU Zhuo, DAN Qiongpeng, ZHANG Xiongfei, PANG Bo, PENG Yongzhen. Optimization of nitrogen removal performance of multistage AO step-feed process for a municipal wastewater treatment plant[J]. ENVIRONMENTAL ENGINEERING , 2025, 43(9): 1-8. doi: 10.13205/j.hjgc.202509001

Citation:

ZHU Zhuo, DAN Qiongpeng, ZHANG Xiongfei, PANG Bo, PENG Yongzhen. Optimization of nitrogen removal performance of multistage AO step-feed process for a municipal wastewater treatment plant[J]. ENVIRONMENTAL ENGINEERING , 2025, 43(9): 1-8. doi: 10.13205/j.hjgc.202509001

Citation:

ZHU Zhuo, DAN Qiongpeng, ZHANG Xiongfei, PANG Bo, PENG Yongzhen. Optimization of nitrogen removal performance of multistage AO step-feed process for a municipal wastewater treatment plant[J]. ENVIRONMENTAL ENGINEERING , 2025, 43(9): 1-8. doi: 10.13205/j.hjgc.202509001

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Optimization of nitrogen removal performance of multistage AO step-feed process for a municipal wastewater treatment plant

doi: 10.13205/j.hjgc.202509001

1. General Water of China Co. Ltd., Beijing 100022, China;
2. CECEP Shenzhen Renewable Energy Co., Ltd., Shenzhen 518104, China;
3. National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Beijing University of Technology, Beijing 100124, China

Received Date: 2025-04-01
Available Online: 2025-11-05
Publish Date: 2025-09-01

Abstract

Abstract

In the context of enhanced requirements for wastewater treatment efficiency and increasingly stringent effluent standards for total nitrogen （TN）， this study conducted a systematic process optimization investigation at a wastewater treatment plant in Shenzhen with a designed capacity of 350000 m³/d. The plant combined a two-stage anoxic/oxic （AO） enhanced system for nitrogen removal on the basis of the anaeroxic/anoxic/oxic （A²O） process （i.e.， an A²O + multi-stage AO improved process）， but there were problems such as low utilization of carbon sources， insufficient use of the multi-stage AO， poor control of dissolved oxygen （DO） and fluctuations of TN in the effluent. In terms of process operating parameters， the influent distribution ratio among the anaerobic， anoxic zone 2， and anoxic zone 3 was adjusted from 7∶3∶0 to 4∶4∶2， while the internal recirculation was deactivated； regarding aeration control， the air-to-water ratio was reduced from 3∶1 to 2∶1； and in terms of pharmaceutical dosing， the number of carbon source dosing points was decreased from three （anaerobic zone， anoxic zone 2， and anoxic zone 3） to one （anoxic zone 3）. Under the premise of requiring no new structures， additional equipment， or production shutdown， dual objectives of reducing operating costs and improving effluent water quality were achieved. Following process optimization， the limitation on TN removal efficiency caused by internal reflux was eliminated， with the average TN concentration in the effluent decreasing from （11.93±1.37） mg/L to （8.11±2.00） mg/L. The raw water carbon source was efficiently allocated to each anoxic zone. As a result， the unit consumption of carbon source dosing decreased from 1.48 mg COD/L to 0.62 mg COD/L， with a reduction rate of 58.07%， while the unit electricity consumption dropped from 0.339 kW·h/m³ to 0.296 kW·h/m³， with a decrease rate of 12.88%. Over an 11-month operational period， carbon source dosing was reduced by 371.45 tons， electricity consumption decreased by 4221043.40 kW·h， and carbon emissions were cut by 3343488.47 kg CO₂-eq. This process optimization not only enhanced the operational efficiency of the wastewater treatment plant but also achieved energy savings and emission reduction， providing valuable insights and reference for the optimization and upgrading of similar wastewater treatment plants.
- municipal wastewater treatment plant,
- multi-stage AO,
- nitrogen removal,
- process optimization,
- energy saving and carbon reduction

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References(16)

References

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