AUTHOR=Wu Yifeng , Liu Xiangru , Wang Qi , Han Dongxu , Lin Shanshan 

TITLE=Fe3O4-Fused Magnetic Air Stone Prepared From Wasted Iron Slag Enhances Denitrification in a Biofilm Reactor by Increasing Electron Transfer Flow

JOURNAL=Frontiers in Chemistry

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2022.948453

DOI=10.3389/fchem.2022.948453

ISSN=2296-2646

ABSTRACT=nFe3O4 was prepared from wasted iron slag and loaded onto air stone (named magnetic air stone or MAS in the following text). The main component of air stone is carborundum. To study the magnetic effects of MAS on denitrification, a biofilm reactor was built and its microbial community structure and electron transfer in denitrification was analyzed. The results showed that MAS improved performance of the reactor in both carbon and nitrogen removals compared with air stone (AS) control, and the average removal efficiency of COD, TN, and NH4+-N increased by 17.15%, 16.1% and 11.58%, respectively. High-throughput sequencing revealed that magnetism of MAS had significant effect on diversity and richness of microorganisms in the biofilm. The addition of MAS also reduced the inhibition of rotenone, mipalene dihydrochloride (QDH) and sodium azide on the respiratory chain in denitrification and enhanced the accumulation of nitrite. In order to provide sufficient substrate for the following denitrification process. Therefore, the denitrification process is accelerated. The results allowed us to deduce the acceleration sites of MAS in the denitrification electron transport chain.
The existence of MAS provides a new channel for the denitrifying electron transport process. Even in the presence of respiratory inhibitors of denitrifying enzymes， The electron transfer channel provided by MAS still exists objectively, this is the mechanism that MAS can restore the denitrification process inhibited by respiratory inhibitors to a certain extent.