[Startup Strategies for the SNAD Granular Sludge Process at Low Temperature]

Area of Science:

• Environmental Science
• Water Treatment Engineering
• Microbiology

Background:

• Simultaneous partial nitrification, ANAMMOX, and denitrification (SNAD) processes are crucial for advanced wastewater treatment.
• Optimizing startup strategies is essential for efficient and stable nitrogen removal.

Purpose of the Study:

• To investigate the impact of different startup strategies on SNAD granular sludge processes.
• To compare the effectiveness of initiating with the completely autotrophic nitrogen removal over nitrite (CANON) and anaerobic ammonia oxidation-denitrification (SAD) processes.

Main Methods:

• Initiating SNAD processes using CANON at 12.7°C (R1) and SAD at 18.3°C (R2).
• Monitoring ammonia nitrogen and total nitrogen removal rates under varying ammonia concentrations.
• Observing microbial community shifts, particularly Nitrite-Oxidizing Bacteria (NOB) proliferation.

Main Results:

• The R2 reactor (SAD startup) achieved a higher total nitrogen removal rate (89.1%) compared to R1 (86.7%).
• R2 consistently met stringent discharge standards (<6 mg·L⁻¹ total nitrogen), even at low ammonia concentrations.
• The anaerobic SAD startup effectively suppressed NOB, ensuring system stability and successful SNAD operation.

Conclusions:

• The SAD process startup is a more effective strategy for initiating SNAD granular sludge processes.
• Anaerobic operation during startup is key to preventing NOB overgrowth and achieving stable, high-efficiency nitrogen removal.
• This approach ensures compliance with environmental discharge regulations for total nitrogen.