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Study of control strategy and simulation in anoxic-oxic nitrogen removal process
Yong-Zhen Peng1, Zhi-Hui Wang, Shu-Ying Whang
1Key Lab of Beijing for Water Quality Science and Water Environmental Recovery Engineering, Beijing University of Technology, Beijing 100022, China. pyz@bjut.edu.cn
Journal of Environmental Sciences (China)
|August 9, 2005
Summary
Optimizing external carbon addition in anoxic-oxic (A/O) wastewater treatment is key. Maintaining nitrate plus nitrite (NOx(-) -N) near 2 mg/L optimizes total nitrogen removal and carbon dosage for better effluent quality.
Area of Science:
- Environmental Engineering
- Wastewater Treatment Technologies
- Process Control
Background:
- Low carbon to nitrogen (C/N) ratio in domestic wastewater challenges effective nutrient removal.
- Anoxic-oxic (A/O) processes require precise control of external carbon addition for optimal performance.
- Nitrate plus nitrite (NOx(-) -N) concentration is a critical parameter in anoxic denitrification.
Purpose of the Study:
- To develop and evaluate a control strategy for external carbon addition in A/O processes.
- To determine the optimal level of NOx(-) -N for efficient total nitrogen (TN) removal.
- To simulate and compare the effectiveness of different control strategies for carbon dosing.
Main Methods:
- Investigated the relationship between external carbon dosage and NOx(-) -N concentration in the anoxic zone.
- Developed a simplified mathematical model based on the Activated Sludge Model No. 1 (ASM No. 1).
- Simulated the performance of PI and feed-forward PI controllers for carbon dosage control.
Main Results:
- Total nitrogen (TN) removal efficiency plateaus when S(NO) exceeds approximately 2 mg/L.
- Maintaining S(NO) around 2 mg/L optimizes carbon dosage while meeting effluent quality standards.
- Both PI and feed-forward PI controllers demonstrated good dynamic response and steady precision.
- Feed-forward PI controller showed superior control performance by accounting for influent variations.
Conclusions:
- A control strategy targeting S(NO) at approximately 2 mg/L is effective for optimizing carbon dosage and effluent quality in A/O systems.
- Mathematical modeling and simulation confirm the viability of PI and feed-forward PI controllers for managing external carbon addition.
- Feed-forward PI control offers enhanced robustness against influent disturbances in wastewater treatment.