Enhanced nitrogen removal from micro-polluted water by Fe (II)/Fe (III) cycling under intermittent aeration

The potential of iron-carbon materials (FeC) as inorganic electron donors for aerobic denitrification of micro-polluted source water was explored. For this purpose, a raw water denitrification experiment was conducted using FeC under intermittent aeration condition. Then, magnetite was added as a biological carrier to construct another system, FeC and magnetite intermittent aeration reaction system, (FCMI). The findings revealed that FCMI notably removed the pollutants with the removal efficiencies of nitrate, total nitrogen, total phosphorus, and chemical oxygen demand reaching 95.63%, 88.62%, 90.48%, and 61.46%, respectively. Cycling between aerobic and anaerobic environments facilitated the formation of Fe (II)/Fe (III) cycle within FeC materials. Microbial profiling revealed that Proteobacteria and Actinobacteria comprised 97.14% of the total abundance in FCMI. Iron-reducing bacteria and aerobic denitrifying bacteria were found to thrive on the surface of magnetite materials. The abundance of enzymes related to denitrification under intermittent aeration exceeded those under continuous aeration levels by 8–19%. This study verifies the ability of iron electrons to cycle under intermittent aeration condition and proposes a novel strategy for in-situ denitrification of micro-polluted source water.