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Updated: Jan 20, 2026

Laboratory-determined Phosphorus Flux from Lake Sediments as a Measure of Internal Phosphorus Loading
Published on: March 6, 2014
Particular internal recirculation frequency scope for enhancing denitrifying phosphorus removal in an oxidation ditch
Shao Po Wang1, Jing Jie Yu1, Fan Kai Su2
1Tianjin Key Laboratory of Aquatic Science and Technology, Tianjin Chengjian University, Tianjin 300384, China; School of Environmental & Municipal Engineering, Tianjin Chengjian University, Tianjin 300384, China; and Municipal Experimental Teaching Demonstration Center of Environmental and Municipal Engineering, Tianjin Chengjian University, Tianjin 300384, China E-mail: yjj.mary@yahoo.com; yjj.mary@163.com.
Optimizing internal recirculation frequency (IRF) in oxidation ditch (OD) systems enhances denitrifying phosphorus removal (DNPR). Proper IRF control is key for efficient simultaneous nitrogen and phosphorus removal in wastewater treatment.
Area of Science:
- Environmental Engineering
- Water Treatment Technologies
- Microbial Ecology
Background:
- Oxidation ditch (OD) systems are widely used for wastewater treatment.
- Internal recirculation frequency (IRF) is a critical operational parameter influencing system performance.
- Denitrifying phosphorus removal (DNPR) is essential for nutrient management in wastewater.
Purpose of the Study:
- To investigate the impact of internal recirculation frequency (IRF) on denitrifying phosphorus removal (DNPR) in an oxidation ditch (OD) system.
- To determine the optimal IRF range for maximizing nutrient removal efficiencies.
- To understand the relationship between IRF and the microbial community dynamics (DPAOs/PAOs ratio).
Main Methods:
- Batch experiments were conducted to measure the ratios of denitrifying polyphosphate-accumulating organisms (DPAOs) to polyphosphate-accumulating organisms (PAOs) under varying IRF conditions.
- Mass balance method was employed to analyze nutrient transformations based on IRF changes.
- Nutrient removal efficiencies for total phosphorus (TP) and total nitrogen (TN) were evaluated.
Main Results:
- An optimal IRF range of 3.4–7.5 h⁻¹ resulted in a DPAOs/PAOs ratio of approximately 50%.
- Within this optimal range, TP removal exceeded 20%, and TN removal via DNPR was over 11%, with overall TP and TN removal efficiencies of >93% and >80%, respectively.
- Higher IRF (>11.5 h⁻¹) significantly decreased TN removal efficiency, hindering simultaneous nitrogen and phosphorus removal.
Conclusions:
- The internal recirculation frequency (IRF) significantly influences the denitrifying phosphorus removal (DNPR) performance of oxidation ditch (OD) systems.
- Controlling IRF within an optimal range (3.4–7.5 h⁻¹) is crucial for achieving high efficiencies in simultaneous nitrogen and phosphorus removal.
- The findings provide valuable insights for optimizing OD system operation for enhanced nutrient removal.
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Nitrogen, phosphorus, and potassium are the main components of soil fertilizer. These methods isolate each nutrient from the soil into a solution that can be analyzed using turbidity and color to determine the...
