Removal of nitrogen from livestock wastewater by iron cycling under feammox and no3–-dependent fe(Ii) oxidation coupling reaction

Abstract

In this paper, three groups of controlled variable experiments were compared for 64 d, which was + based on the coupling reaction of Feammox (NH4 oxidation with Fe(III) reduction) and NDFO (NO3–-dependent Fe(II) oxidation), to explore the nitrogen removal effect of Feammox and NDFO coupling technology on livestock wastewater and iron recycling mechanism under anaerobic con-ditions. Through the analysis of transformation in the contents of various nitrogen and iron in the experimental operation system, it was found that the simultaneous nitrogen removal occurred with the presence of interconversion between Fe(II) and Fe(III). The Fe(III) added in the C2 group advanced the progress of Feammox and realized the iron cycle to remove nitrogen under the com-bination of Feammox and NDFO. However, after 50 d of operation, due to the insufficient NO3 – content, the nitrogen removal was weakened, and the final ammonia nitrogen removal rate was – 65.1%, and the total nitrogen removal rate was 71.2%. Comparatively, the C3 group added NO3 regularly based on the C2 group which promoted the NDFO reaction and further realized the + circle of Feammox and NDFO. The final NH4 removal rate reached 88.9%, and the total nitrogen removal rate reached 84.6%, which was significantly better than the C2 group and the blank group. The analysis of the microbial community by 16S rRNA high-throughput sequencing technology concluded that the main functional microorganism under the system was Ignavibacteria. This study provides a new theoretical basis for the exploration of Fe/N cycling mechanism under Feammox-NDFO coupling technology and nitrogen treatment in livestock wastewater in the future.