Autotrophic ammonia removal from landfill leachate in anaerobic membrane bioreactor

Abstract

Anaerobic ammonium oxidation (ANAMMOX) process, an advanced biological nitrogen removal, removes ammonia using nitrite as the electron acceptor without oxygen. In this paper, ANAMMOX process was adopted for removing -N from landfill leachate having low COD using anaerobic membrane bioreactor (AnMBR). The AnMBR was optimized for nitrogen loading rate (NLR) varying from 0.025 to 5 kg -N/m³/d with hydraulic retention time (HRT) ranging from 1 to 3 d. -N removal efficacy of 85.13±9.67% with the mean nitrogen removal rate of 5.54±0.63 kg -N/m³/d was achieved with NLR of 6.51±0.20 kg -N/m³/d at 1.5 d HRT. The nitrogen transformation intermediates in the form of hydrazine (N₂H₄) and hydroxylamine (NH₂OH) were 0.008±0.005 and 0.006±0.001 mg/l, respectively, indicating co-existence of aerobic ammonia oxidizers and ANAMMOX. The free ammonia (NH₃) and free nitrous acid (HNO₂) concentrations were 26.61±16.54 mg/l and (1.66±0.95)×10⁻⁵ mg/l, preventing -N oxidation to -N enabling sustained -N removal.

Keywords:

• landfill leachate
• anaerobic membrane bioreactor
• ANAMMOX
• ammonia removal
• autotrophic

Acknowledgements

The authors gratefully acknowledge the support given by the University Grants Commission Research Fellowship for meritorious scholars in sciences to carry out this study.