Nitrate-dependent ferrous oxidation: Feasibility, mechanism, and application prospects for wastewater treatment

Nitrate-dependent ferrous oxidation (NDFO) has substantial potential as a new microbially mediated denitrification technology for treating low carbon/nitrogen wastewater. This study provides a systematic and comprehensive overview of the NDFO process and describes the underlying mechanisms and functional microorganisms from various perspectives. The possible electron transfer pathways involved in the NDFO process are discussed in detail. The focus is on the key influencing factors, namely dissolved oxygen, pH, temperature, organic carbon, Fe(II) sources, Fe/N, and coexisting ions, which were explored. The greatest limitation of the NDFO process is "iron crusting," and a re-examination of its mineralization mechanism, effects of mineralization, and crust prevention strategies would help to enhance nitrogen removal performance. Additionally, a coupled electrochemical-biological NDFO process suitable for low carbon/nitrogen wastewater is proposed to improve the stability of nitrogen removal and shorten the start-up time of the system in the NDFO process. Finally, recent trends and challenges of the NDFO process in wastewater treatment applications are summarized. This review presents novel insights into the engineering of the NDFO process, providing a reference for parameter optimization and practical application.