Achieving Mainstream Nitrogen Removal through Coupling Anammox with Denitratation.

Area of Science:

• Environmental Microbiology
• Wastewater Treatment Engineering
• Biogeochemical Cycles

Background:

• Achieving energy-neutral sewage treatment hinges on mainstream anammox (anaerobic ammonium oxidation).
• Current mainstream anammox strategies often rely on nitritation (ammonium to nitrite conversion).
• This study explores an alternative coupling of anammox with denitratation (nitrate to nitrite conversion).

Purpose of the Study:

• To demonstrate a novel mainstream anammox process coupling anammox with denitratation.
• To evaluate the efficiency and stability of this new process in a long-term anoxic/oxic (A/O) biofilm system.
• To investigate the microbial community and key metabolic pathways involved.

Main Methods:

• An anoxic/oxic (A/O) biofilm reactor was operated for over 400 days with synthetic domestic wastewater.
• Total nitrogen (TN) removal efficiency, C/N ratio, and dinitrogen production were quantified.
• Batch tests and metagenomic analysis were performed to understand microbial activity and community structure.

Main Results:

• The A/O biofilm system achieved 80 ± 4% total nitrogen removal at a low C/N ratio (2.6).
• Anammox accounted for 70% of dinitrogen production, with denitratation supplying the necessary nitrite.
• Metagenomic analysis revealed dominant species like Candidatus Jettenia caeni and Candidatus Kuenenia stuttgartiensis, with high nitrate reductase abundance.

Conclusions:

• Coupling anammox with denitratation offers a stable and efficient alternative for mainstream nitrogen removal in wastewater treatment.
• This nitrite-producing process demonstrates high total nitrogen removal efficiency, even at low C/N ratios.
• The system's stability and integration potential with existing technologies like high-rate activated sludge are significant advantages.