Simultaneous nitrogen and phosphorus removal under low dissolved oxygen conditions

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Microbial Ecology in Wastewater

Background:

• Conventional activated sludge processes often struggle with efficient biological nitrogen and phosphorus removal.
• Increasingly stringent environmental regulations necessitate advanced wastewater treatment solutions.
• Nutrient pollution from wastewater poses significant risks to aquatic ecosystems.

Purpose of the Study:

• To evaluate the efficacy of a low dissolved oxygen activated sludge process for enhanced biological nutrient removal.
• To determine the performance of this process under varying influent loads of chemical oxygen demand (CODcr), total nitrogen (TN), and total phosphorus (TP).
• To assess the feasibility of retrofitting existing activated sludge systems with this low dissolved oxygen approach.

Main Methods:

• A full-scale test was conducted using a low dissolved oxygen activated sludge process.
• Influent concentrations of CODcr, TN, and TP were monitored across a defined range.
• Effluent quality parameters including CODcr, BOD5, NH3-N, TN, and TP were measured over a two-month period.

Main Results:

• The process achieved high average removal efficiencies: 94.9% for CODcr, 86.7% for TN, and 93.0% for TP.
• Effluent concentrations consistently met standards, with means below 50 mg/L for CODcr, 25 mg/L for BOD5, 10 mg/L for NH3-N, and 1.0 mg/L for TP.
• The process demonstrated robustness across a wide range of influent nutrient and organic loads.

Conclusions:

• The low dissolved oxygen activated sludge process is highly effective for simultaneous biological nitrogen and phosphorus removal.
• This process offers a simplified system design with fewer facilities compared to conventional methods.
• Retrofitting conventional activated sludge plants with this low dissolved oxygen process presents a practical and efficient upgrade pathway for improved nutrient management.