Improving anammox activity and reactor start-up speed by using CO₂/NaHCO₃ buffer

Area of Science:

• Environmental microbiology
• Wastewater treatment technologies

Background:

• Anammox bacteria exhibit slow growth rates and sensitivity to pH variations, complicating reactor start-up.
• Effective buffering strategies are crucial for optimizing anammox processes and achieving rapid reactor establishment.

Purpose of the Study:

• To investigate the impact of different buffer solutions on nitrogen removal and anammox sludge growth.
• To identify optimal buffering conditions for rapid and efficient anammox reactor start-up.

Main Methods:

• Comparative analysis of three buffer solutions: CO2/NaHCO3 buffer solution (CCBS), HEPES, and PBS.
• Monitoring nitrogen removal efficiency and anammox sludge characteristics in laboratory-scale reactors.
• Assessing anammox activity and bacterial community composition (dominant species: Candidatus Kuenenia).

Main Results:

• CCBS demonstrated superior performance in nitrogen removal compared to HEPES and PBS, which inhibited anammox activity.
• Reactors with 50 mmol/L CCBS achieved rapid start-up within 20 days, with high specific anammox activity (1.01±0.10 gN/(gVSS·day)) and volumetric activity (0.83±0.06 kgN/(m3·day)).
• Candidatus Kuenenia was identified as the dominant anammox bacteria (71.8% relative abundance), and CCBS facilitated quick start-up even under non-strict anaerobic conditions.

Conclusions:

• CO2/NaHCO3 buffer solution (CCBS) is highly effective for the rapid start-up of anammox reactors.
• CCBS promotes efficient nitrogen removal and supports the growth of dominant anammox bacteria like Candidatus Kuenenia.
• The findings offer a viable strategy for accelerating the development of engineered anammox systems.