Insights into two stable mainstream deammonification process and different microbial community dynamics at ambient...

Area of Science:

• Environmental microbiology
• Wastewater treatment engineering

Background:

• Achieving stable mainstream deammonification remains a significant challenge in wastewater treatment.
• Ambient temperature operation is desirable for energy efficiency but can impact microbial community stability.

Purpose of the Study:

• To evaluate nitrogen removal efficiency and microbial community dynamics in two deammonification reactor configurations at ambient temperatures.
• To investigate the factors influencing the stability and performance of deammonification processes under varying conditions.

Main Methods:

• Operation of two deammonification reactors (granular sludge R1, mixed sludge R2) at ambient temperatures (21-28 °C).
• Monitoring nitrogen removal rates and microbial community composition using molecular techniques.
• Analysis of gene abundances related to ammonia oxidation and denitrification.

Main Results:

• Satisfactory nitrogen removal was achieved in both reactors (R1: 0.42 ± 0.03 kg N/(m³·d), R2: 0.39 ± 0.04 kg N/(m³·d)).
• Anammox bacteria (Candidatus Jettenia) demonstrated high adaptability and efficient activity (0.84-1.54 mg N/(g VSS·h)).
• Low Nitrospira abundance was observed due to hydrazine inhibition and competition from denitrifying bacteria (Denitratisoma), which were more abundant in R2 (9.2%-18.5%).
• Reactor R1 exhibited greater resistance to unfavorable conditions compared to R2.

Conclusions:

• Stable deammonification is achievable at ambient temperatures, with granular sludge reactors showing enhanced robustness.
• The microbial community structure, particularly the balance between anammox, ammonia-oxidizing, and denitrifying bacteria, is crucial for process stability.
• Further research into optimizing conditions to mitigate hydrazine inhibition and manage denitrifying bacteria competition is warranted.