Performance and microbial community analysis of two sludge type reactors in achieving mainstream deammonification...

Area of Science:

• Environmental Science
• Microbiology
• Chemical Engineering

Background:

• Deammonification is an energy-efficient nitrogen removal method.
• Mainstream deammonification for low-strength ammonium wastewater faces challenges.
• Sidestream deammonification is effective for high-strength wastewater.

Purpose of the Study:

• To investigate the stability and efficiency of mainstream deammonification with hydrazine addition.
• To compare the performance of a deammonification granular reactor and a mixed sludge reactor.
• To analyze the microbial community and activity in both reactor types.

Main Methods:

• Two reactors were operated with hydrazine (N2H4) addition.
• One reactor used granular sludge, the other used mixed sludge (ammonia oxidizing bacteria and anaerobic ammonia oxidizing bacteria).
• Total nitrogen removal efficiency (TNRE) and nitrogen removal rate (NRR) were measured. Microbial community analysis (genus abundance) and ex-situ activity assays were performed.

Main Results:

• The deammonification granular reactor showed higher TNRE (80.5 ± 5.8%) and NRR (0.33 ± 0.04 g/(L·day)).
• Granular sludge facilitated balanced activity between ammonia oxidizing bacteria (AOB) and anaerobic ammonia oxidizing bacteria (AnAOB).
• Hydrazine enhanced AnAOB and suppressed nitrite oxidizing bacteria (NOB) in the mixed sludge reactor, potentially due to spatial distribution.

Conclusions:

• Mainstream deammonification can be stabilized with hydrazine addition.
• Granular sludge reactors are more efficient for low-strength ammonium wastewater treatment.
• Hydrazine influences microbial community dynamics, favoring AnAOB and suppressing NOB.