Flexible Nitrite Supply Alternative for Mainstream Anammox: Advances in Enhancing Process Stability

Area of Science:

• Environmental Science
• Microbiology
• Chemical Engineering

Background:

• Anaerobic ammonium oxidation (anammox) is a sustainable wastewater treatment but limited by unstable nitrite production and nitrate residue.
• Current nitritation-based anammox processes face challenges in large-scale application due to process instability.

Purpose of the Study:

• To evaluate an efficient alternative to nitritation-based anammox by substituting nitrite supply with partial-denitrification (PD) under mainstream conditions.
• To assess the performance of a partial-denitrification coupled anammox (PD/A) process for municipal wastewater treatment.

Main Methods:

• A PD/A process was implemented by mixing nitrifying effluents with raw wastewater.
• The process involved partial oxidation of ammonia to nitrate, followed by PD (nitrate to nitrite) and anammox.
• Microbial community analysis identified dominant genera responsible for PD and anammox.

Main Results:

• Excellent effluent quality was achieved with total nitrogen < 5 mg L^-1, even with temperature fluctuations (25.7-16.3 °C).
• The dominant denitrifiers were Thauera (36.4%-37.4%), coexisting with anammox bacteria Candidatus Brocadia (0.33%-0.46%).
• The PD/A process reduced aeration energy consumption by up to 50% and organic resource demand by 80%, with lower N₂O production.

Conclusions:

• Coupling anammox with flexible nitrite supply via partial-denitrification is a stable and efficient mainstream wastewater treatment strategy.
• The PD/A process demonstrates significant reductions in operational costs and environmental impact compared to conventional methods.
• This approach holds great potential for sustainable and economical municipal wastewater treatment.