Simultaneous nitrification, denitrification, and phosphorus removal in a lab-scale sequencing batch reactor.

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment

Background:

• Simultaneous nitrification and denitrification (SND) and enhanced biological phosphorus removal (EBPR) reduce energy and chemical oxygen demand (COD) for nutrient removal.
• Combining these processes offers potential for simultaneous nitrogen and phosphorus removal with minimal COD requirements.

Purpose of the Study:

• To investigate the feasibility of achieving simultaneous nitrification, denitrification, and phosphorus removal in a lab-scale sequencing batch reactor (SBR).
• To evaluate the efficiency of nutrient removal under low dissolved oxygen (DO) conditions and identify the microbial pathways involved.

Main Methods:

• Operation of a lab-scale SBR in an alternating anaerobic-aerobic mode.
• Controlled low dissolved oxygen (DO) concentration (0.5 mg/L) during the aerobic phase.
• Analysis of nutrient concentrations, COD, polyhydroxyalkanoates (PHAs), and off-gas composition.

Main Results:

• The SBR successfully accomplished simultaneous nitrification, denitrification, and phosphorus removal.
• Phosphorus removal to <0.5 mg/L was achieved by polyphosphate-accumulating organisms (PAOs) utilizing released PHAs.
• Nitrogen removal occurred via the nitrite pathway, with nitrous oxide (N(2)O) as the primary denitrification product, indicating the dominance of denitrifying glycogen-accumulating organisms (DGAOs).

Conclusions:

• The combined SND and EBPR process is effective for simultaneous nitrogen and phosphorus removal with low COD demand.
• Denitrification proceeds via the nitrite pathway, primarily driven by DGAOs, and produces N(2)O.
• This approach offers a promising strategy for energy-efficient wastewater treatment.