Study on the mechanism of enhanced anaerobic ammonia oxidation performance by extracellular electron acceptor biochar

ABSTRACT

Anaerobic ammonia oxidation process has the advantages of energy and cost reduction, therefore, it has been considered as one of the main alternatives to conventional biological denitrification process in recent years. Biochar has been applied in the anammox process for nitrogen removal efficiency. But, due to its extracellular electron transfer capacity and abundance of redox-specific functional groups, which served as extracellular electron acceptor to anaerobically oxidize NH₄⁺ is still controversy. In this study, the anaerobic ammonia oxidation was investigated when biochar was used as electron acceptor in the wastewater. According to the optimal process variables determined in the batch tests, when the influent NH₄⁺-N concentration in the anaerobic ammonia oxidation reaction was 30–50 mg/L and the biochar dosing was at 10 g/L, it showed some promotion in the long-term experiments. The anaerobic ammonia oxidation process with biochar as the electron acceptor reached more than 60% NH₄⁺-N removal efficiency in the system, and the ΔNO₃^--N/ΔNH₄⁺-N ratio reached 0.19 which tended to the theoretical value. After 20 days, the voltage in the system keeps fluctuating about 4 mV, indicated that the functional bacteria using biochar as the electron acceptor gradually dominated the system. In addition, the abundance of norank_f__norank_o__SBR1031 in the Chloroflexi phylum has increased significantly at 29.92%, while the abundance of the major genus Candidatus_Kuenenia in AnAOB has decreased slightly at 11.47%.

GRAPHICAL ABSTRACT

KEYWORDS:

• Anaerobic ammonia oxidation
• electron acceptor
• biochar
• microbial community
• denitrification efficiency

Acknowledgements

Li Zhang: Investigation, Writing review & editing. Qi Jiang: Experimental work, Formal analysis, Writing original draft. Diannan Huang: Writing review & editing. Di Luo: Conceptualization, Writing review. Yunan Gao and Ye Bin: Supervision, Funding acquisition.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data and materials that support the results or analyses presented in this paper are freely available from all authors by request.

Additional information

Funding

This work was supported by GuangDong Basic and Applied Basic Research Foundation [grant number 2022A1515140184]; Major Science and Technology Program for Water Pollution Control and Treatment [grant number 2014ZX07202-011].