Synergistic pathways and microbial mechanisms of iron-mediated nitrogen transformation in wastewater treatment...

Microorganism driven iron-nitrogen metabolic cycles demonstrate broad application prospects in the field of wastewater treatment. As a ubiquitous element in the environment, iron is not only an essential trace element for microbial metabolism and growth but also plays multiple roles that extend beyond its nutritional function in the biological nitrogen removal process. The iron-nitrogen cycle is often closely associated with processes such as Anammox, Nitrification, Denitrification, DNRA, and Feammox. Although the mechanisms of iron-mediated biological nitrogen removal may vary depending on the iron valence states, the common transformation characteristics of these pathways provide important clues for understanding element-microbe interactions. This review systematically elaborates on the metabolic pathways and mechanisms of iron-involved biological-specifically Feammox, NDFO, and Anammox-and abiotic nitrogen removal processes. It further analyzes the influence of iron on heterotrophic and autotrophic nitrogen removal from the perspectives of microbial communities and electron transfer. Furthermore, the article identifies key challenges currently faced by iron-mediated biological nitrogen removal technologies and offers insights into future research directions to promote further development and engineering.