Roles of Fe(II), Fe(III) and Fe0 in denitrification and anammox process: Mechanisms, advances and perspectives

As the dominating parts of biological systems, microorganisms mediate the nitrogen removal process. Iron ion included Fe(II), Fe(III), and zero-valent iron (Fe0), enhanced nitrogen removal efficiency during the denitrification and anaerobic ammonia oxidation (anammox) processes, accelerated the electron transfer process, regulated the distribution of microbial flora by improving the metabolic activity and the secretion of extracellular polymeric substances. At the same time, iron ion has negative effects, which are discussed. Finally, this paper proposed the direction of research related to iron-mediated denitrification and anammox technology in wastewater treatment in the future.