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Phosphorus removal under anoxic conditions in a continuous-flow A2N two-sludge process.
1School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin, PR China 150091.
Summary
The Anaerobic-Anoxic/Nitrification (A2N) system efficiently removes phosphorus and nitrogen from wastewater. Optimal performance is achieved with a specific influent COD/TN ratio, sludge retention time, and sludge flow rates.
Area of Science:
- Environmental Engineering
- Wastewater Treatment Technologies
- Microbial Ecology
Background:
- The Anaerobic-Anoxic/Nitrification (A2N) system is a continuous-flow, two-sludge process.
- Polyphosphate-accumulating organisms (PAOs) utilize organic substrate and nitrate for enhanced phosphorus removal under anoxic conditions.
Purpose of the Study:
- To evaluate the phosphorus removal capacity of a modified A2N system.
- To investigate factors influencing phosphorus and nitrogen removal efficiency in the A2N system.
Main Methods:
- A lab-scale A2N system was operated for 260 days using domestic sewage.
- Key operational parameters including influent COD/TN ratio, Sludge Retention Time (SRT), Bypass Sludge Flow rate (BSF), and Return Sludge Flow rate (RSF) were investigated.
Main Results:
- Optimal phosphorus and nitrogen removal occurred at an influent COD/TN ratio of approximately 6.49.
- An SRT of 14 days was found to be optimal.
- BSF and RSF were optimized at 26-33% of the influent flow rate for maximum nutrient removal.
Conclusions:
- The modified A2N system demonstrates high efficiency in simultaneous phosphorus and nitrogen removal.
- Optimizing operational parameters like COD/TN ratio, SRT, BSF, and RSF is crucial for maximizing nutrient removal in A2N systems.