[Running Condition and Bacterial Community Associated with the Partial Nitritation System]

Area of Science:

• Environmental microbiology
• Wastewater treatment
• Biotechnology

Background:

• Partial nitritation is a key process in wastewater treatment for nitrogen removal.
• Optimizing conditions is crucial for efficient microbial activity and effluent quality.
• Understanding microbial community dynamics is essential for process control.

Purpose of the Study:

• To investigate the optimal operating conditions for partial nitritation.
• To characterize the microbial community structure during partial nitritation.
• To assess the feasibility and economic viability of the partial nitritation process.

Main Methods:

• Operated a reactor under controlled conditions: high sludge concentration (>4000 mg/L), low dissolved oxygen (<0.2 mg/L), temperature (15-29°C), HRT (4.6 h), and circulation ratio (75%).
• Utilized quantitative PCR and 16S rRNA gene clone libraries to analyze microbial communities.
• Performed phylogenetic analysis of bacterial amoA gene sequences.

Main Results:

• Optimal conditions maximized microbial biomass and achieved a nitrite to ammonium ratio of approximately 1.0 by adjusting dissolved oxygen.
• Ammonia-oxidizing bacteria, particularly Nitrosomonas, dominated the microbial community, promoting partial nitritation at low dissolved oxygen.
• Planctomycetes abundance was higher in partial nitritation compared to conventional nitrification; Nitrobacter and Nitrospira were undetected.

Conclusions:

• Partial nitritation is technically and economically feasible under optimized conditions.
• Low dissolved oxygen favors specific ammonia-oxidizing bacteria, enhancing process efficiency.
• The distinct microbial community structure in partial nitritation differs significantly from conventional nitrification systems.