Simultaneous partial nitritation and anammox at low temperature with granular sludge

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment

Background:

• Energy autarchic wastewater treatment plants require efficient mainstream autotrophic nitrogen removal.
• Autotrophic nitrogen removal processes are crucial for sustainable wastewater management.

Purpose of the Study:

• To investigate the feasibility of autotrophic nitrogen removal in a single reactor using granular sludge.
• To assess the impact of temperature and dissolved oxygen on nitrogen removal efficiency.

Main Methods:

• Operation of a lab-scale gas-lift sequencing batch reactor with granular sludge for over 500 days.
• Controlled operation at varying temperatures (20-10°C) and ammonium concentrations (60-160 mg-N L⁻¹).
• Utilized dissolved oxygen (DO) concentration as a control parameter to suppress nitrification.

Main Results:

• Effective suppression of nitrification was achieved at 20°C and 15°C using DO control.
• Nitrogen removal rates reached 0.4 g-NTot L⁻¹ d⁻¹ with efficiencies of 75-85%.
• Prolonged operation at 10°C led to a decline in anammox activity and process efficiency.

Conclusions:

• Autotrophic nitrogen removal in a single reactor with granular sludge is a viable concept for mainstream wastewater treatment.
• DO control is a critical factor for successful autotrophic nitrogen removal, especially at moderate temperatures.
• Low temperatures (10°C) negatively impact anammox activity, requiring further investigation for optimization.