Effects of nZVI and Fe3O4 NPs on anaerobic methanogenesis, microbial communities and metabolic pathways for treating domestic wastewater at ambient temperature

Abstract

Anaerobic methanogenesis from domestic wastewater is one of the promising way to wastewater resource utilization. In this study, the effects of nanoscale zero-valent iron (nZVI) and nano ferroferric oxide (Fe3O4 NPs) on organic matter removal, methanogenesis, microbial communities, and metabolic pathways in the anaerobic biofilm system for treating domestic wastewater at ambient temperature were studied. The results showed nZVI and Fe3O4 NPs not only promoted the hydrolytic fermentation process of the anaerobic biofilm system, but also facilitated the removal of refractory organic matter. Especially, Fe3O4 NPs improved the methanogenic efficiency, shortened the lag time, and entered the rapid methanogenic stage rapidly. Fe3O4 NPs formed direct interspecies electron transfer (DIET) and symbiotic relationship between the acetic acid oxidizing bacteria and the methanogenic bacteria. Furthermore, Fe3O4 NPs promoted the biosynthesis of F420. In the Fe3O4 NPs system, the CO2-reduced methanogenesis, as the main methanogenic pathway, was enhanced.