How efficiently does a metabolically enhanced system with denitrifying anaerobic methane oxidizing microorganisms...

Area of Science:

• Environmental microbiology
• Bioreactor engineering
• Wastewater treatment

Background:

• Nitrite-dependent anaerobic methane oxidation (N-damo) is a promising process for nitrogen removal.
• Simultaneous removal of methane and antibiotics in wastewater is a significant environmental challenge.
• High biomass activities and loading rates are crucial for efficient N-damo process performance.

Purpose of the Study:

• To investigate the N-damo process at high biomass activities for simultaneous removal of nitrite, methane, and antibiotics.
• To evaluate the impact of a novel operational strategy involving Cerium addition on N-damo process stability and efficiency.
• To analyze the microbial community composition and its correlation with process performance and antibiotic removal.

Main Methods:

• Operation of two Membrane Bioreactors (MBRs) at three high nitrite loading rates (NLRs).
• Addition of Cerium as a trace element to the feeding medium to enhance reactor stability.
• Monitoring of nitrite removal activity, methane oxidation, and biotransformation of selected antibiotics.
• Analysis of microbial community composition using high-throughput sequencing.

Main Results:

• Achieved high nitrite removal activity (up to 540 mg N-NO⁻₂ g⁻¹ VSS d⁻¹), comparable to heterotrophic denitrification.
• Cerium addition stabilized reactor operation at high NLRs, enabling long-term performance.
• N-damo bacteria (Candidatus Methylomirabilis) dominated the microbial community, though their relative abundance decreased with increased biomass activity.
• High biotransformation rates were observed for sulfamethoxazole, trimethoprim, cefalexin, and azithromycin; ciprofloxacin showed minimal removal.

Conclusions:

• The N-damo process, enhanced by Cerium, can effectively remove nitrite and methane at high loading rates.
• Microbial community composition, rather than metabolic activity alone, significantly influences antibiotic removal efficiency.
• Further research is needed to optimize N-damo processes for comprehensive contaminant removal in wastewater treatment.