Use of soluble iron salt as an electron acceptor to provide Fe(III) for Feammox process: Ammonium removal performance and mechanism

Abstract

Fe(III) reduction coupled with anaerobic ammonium oxidation (Feammox) is a newly discovered biological ammonium removal technology. Compared to anaerobic ammonium oxidation (anammox) process, Feammox does not require NO2−-N as a reaction substrate and is more tolerant to heavy metals. In this study, soluble iron salts FeCl3 was added to anaerobic sequencing batch reactor (ASBR) to start Feammox process. The effects of Fe/N, pH and temperature on the Feammox performance were investigated. Optimal working conditions were determined by combining the variation law of nitrogen and iron elements. The results showed that the best NH4+-N removal efficiency when Fe/N, pH and temperature were 0.15, 6.5 and 30 °C, respectively. The modified Boltzmann model fitted better in Feammox kinetic analysis (R2 = 0.9789), which could clearly explain that the degradation of substrate and the generation of product. Microbial analysis showed that in addition to the typical iron-reducing bacteria, the dominant genus Candidatus_Brocadia of anammox was also enriched in the system with relative abundance of 3.16 %, implying that both Feammox and anammox contributed to the transformation of NH4+-N. Overall, optimizing the operating conditions of Feammox is important significance to maintain the stability of NH4+-N removal performance and provide theoretical basis for constructing a novel wastewater treatment process.