Relationship between solid retention time and phosphorus removal in anaerobic-intermittent aeration process
Doojin Lee1, Moonil Kim, Jinwook Chung
1Korea Institute of Water and Environment, Korea Water Resources Corporation, 462-1 Jeonmin-dong, Yusung-gu, Daejeon 305-730, Korea.
Journal of Bioscience and Bioengineering
|May 16, 2007
Summary
Increasing solid retention time (SRT) in biological nutrient removal (BNR) systems enhances phosphorus removal efficiency by maximizing phosphate-accumulating organisms (PAOs). Optimal SRT balances PAO numbers and phosphorus wasting load for effective biological phosphorus removal.
Area of Science:
- Environmental Microbiology
- Wastewater Treatment Engineering
- Biotechnology
Background:
- Biological phosphorus removal is crucial for preventing eutrophication.
- Solid retention time (SRT) significantly influences the performance of biological nutrient removal (BNR) systems.
- Phosphate-accumulating organisms (PAOs) are key to effective biological phosphorus removal.
Purpose of the Study:
- To evaluate the impact of different solid retention times (SRTs) on phosphorus removal efficiency in lab-scale BNR reactors.
- To determine the optimal SRT for maximizing phosphorus removal and phosphorus wasting load.
- To assess the population dynamics of PAOs at varying SRTs.
Main Methods:
- Operation of lab-scale biological nutrient removal (BNR) reactors with anaerobic-intermittent aeration (AIA) at SRTs of 15, 20, and 30 days.
- Monitoring of phosphorus removal efficiency and sludge wasting load at each SRT.
- Aerobic digestion experiments to quantify phosphate-accumulating organisms (PAOs) and assess volatile suspended solid (VSS) destruction rates.
Main Results:
- Phosphorus removal efficiency reached 93% at an SRT of 20 days, which also corresponded to the highest phosphorus wasting load.
- Sludge from BNR reactors exhibited higher PAO content and slower VSS destruction rates compared to conventional activated sludge (CAS).
- Longer SRTs (30 days) showed a greater predominance of PAOs, indicated by slower VSS destruction and increased phosphorus release during aerobic digestion.
Conclusions:
- SRT is a critical parameter for optimizing biological phosphorus removal in BNR systems.
- Increasing SRT enhances PAO populations, leading to improved phosphorus removal efficiency.
- The optimal SRT should be determined based on maximizing both PAO numbers and phosphorus wasting load for effective wastewater treatment.
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