Enhanced nitrogen removal and antibiotic resistance genes control through electrocatalytic reduction and the underlying mechanisms

The control of antibiotic resistance genes (ARGs) and removal of nitrogen are the main challenges in antibiotic wastewater treatment. This study adopted the multielectrode microbial fuel cell (MFC) to promote autotrophic denitrification and adopted agricultural waste as a slow-release carbon source to enhance heterotrophic denitrification while running in a siphoning mode. The associated metabolic process and mechanism were explored. The results showed that the electrochemical catalysis and siphoning aeration significantly improved the removal of COD and antibiotics. The number of ARGs and MGEs decreased significantly when both the electrochemical process and the siphoning mode were used. The removal of NH4+-N was limited under open-circuit conditions, and the removal was lower than 35.4% in all the reactors. Under electrochemical conditions, the addition of slow-release carbon sources promoted heterotrophic denitrification, and the removal of TN increased by 42.9%. The microbial mechanism of nitrogen removal and ARG control under the electrochemical process were revealed by metagenomic analysis. Compared with the control group, there were a large number of functional genes related to iron REDOX (oorB, oorD, moxR, moxA, mnxG, and mcoA) in the system, which promoted the efficiency of nitrogen removal through coupling with genes related to the nitrogen metabolic pathway. The results can provide a reference for ARGs control and nitrogen removal in the treatment of antibiotic wastewater containing high nitrogen concentrations.