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The New A-⊘OHO process Based on DO Gradients and Load-Ratio Allocation Enabling Mainstream PN/A in Toxic Industrial
Xiaoqian Cheng1, Acong Chen2, Tuo Wei3
1School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, China.
Bioresource Technology
|December 1, 2025
Summary
A novel wastewater treatment process selectively accumulates nitrogen species, overcoming limitations of partial nitritation-anammox (PN/A) for industrial applications. This optimized A-OHO process significantly reduces total nitrogen and energy consumption.
Area of Science:
- Environmental Engineering
- Wastewater Treatment Technologies
- Bioreactor Design
Background:
- Partial nitritation-anammox (PN/A) offers energy savings and carbon neutrality but faces challenges with toxic pollutants and nitrogen ratio control.
- Coking wastewater presents unique difficulties for conventional PN/A due to high pollutant concentrations and variable loads.
Purpose of the Study:
- To develop and optimize a novel pilot-scale coking wastewater treatment process (A-OHO) for enhanced nitrogen removal.
- To investigate the critical role of dissolved oxygen (DO) gradients and DO-to-pollutant ratios in nitrogen species transformation.
- To establish a practical strategy for mainstream PN/A application in high-concentration industrial wastewater.
Main Methods:
- Implementation of a pilot-scale A-OHO process with controlled dissolved oxygen (DO) concentration gradients.
- Utilized thermodynamic, kinetic, and SHAP analyses to understand nitrogen transformation mechanisms.
- Integrated machine learning and the TCW-ASM3 model for optimizing operating conditions and patterns.
- Developed the A-OHO process into an A-⊘OHO configuration with parallel reactors (ONH3 and ONO2).
Main Results:
- The A-OHO process successfully achieved selective accumulation of nitrogen species through DO regulation.
- DO concentration and DO/pollutant ratios (DO/COD, DO/NH4+-N) were identified as critical factors.
- The A-⊘OHO process sustained anammox without external carbon or recirculation by controlling flow rates and hydraulic retention times (HRT).
- Simulated results showed a decrease in total nitrogen (TN) from 148.20 mg/L to 28.56 mg/L with an optimized flow ratio (0.4) and HRT (15 h/19 h).
- Energy consumption was reduced to 1.55 kWh/m3, a saving of 3.79 kWh/m3 compared to conventional methods.
Conclusions:
- The developed A-⊘OHO process provides a viable strategy for overcoming technical barriers of PN/A in high-concentration industrial wastewater.
- This approach enables effective total nitrogen (TN) emission control to very low levels.
- The study offers a sustainable solution for industrial wastewater management with significant energy savings.
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