Nitrogen removal performance of aerobic denitrifying bacteria enhanced by an iron-anode pulsed electric field

Abstract

Abstract Pulsed electric field (PEF) technology has attracted considerable attention because it can efficiently treat pollutants that are difficult to degrade. In this study, a PEF system using iron as the electrode was constructed to investigate the effect of PEF–Fe on the growth and metabolism of aerobic denitrifying bacteria and the effectiveness of wastewater nitrogen removal. The chemical oxygen demand, NO3-–N and nitrate removal rates were 98.93%, 97.60% and 24.40 mg·L−1·h−1, respectively, under optimal conditions. As confirmed in this study, PEF–Fe could improve the key enzyme activities of W207-14. Scanning electron microscopy revealed that the surface of PEF–Fe-treated W207-14 was intact and smooth without any irreversible deformation. Flow cytometry combined with fluorescence staining analysis also confirmed reversible electroporation on the cell membrane surface of PEF–Fe-treated W207-14. Differentially expressed gene enrichment analysis showed that PEF–Fe activated the transmembrane transport function of ATP-binding cassette transporte (ABC) transport proteins and enhanced the cell membrane permeability of aerobic denitrifying bacteria. The significant differential expression of iron–sulphur cluster proteins facilitated the regulation of electron transport and maintenance of the dynamic balance of iron ions within the PEF–Fe system.