Nitrogen removal from wastewater for heterotrophic nitrification-aerobic denitrification bacterium with the combination of bacteriophage DEY7 and Fe nanoparticles

Heterotrophic nitrification-aerobic denitrification (HN-AD) is a promising strategy for nitrogen removal from wastewater. However, it is limited by factors such as phages in practical applications. Furthermore, nanoscale zero-valent iron (nZVI), a common addition in wastewater treatment systems, plays a crucial role in the HN-AD process. In this study, a strain of bacteriophage named DEY7 was isolated from the HN-AD bacterium YH01. In the absence of phage, adding nZVI to the HN-AD bacterium had a promotional effect on nitrogen removal by bacterium YH01, and the opitum nZVI dose was about 50 mg/L. With the addition of nZVI and phage DEY7, phages have different effects on the nitrification and denitrification of bacterium YH01. Ammonium (NH4+-N) removal was inhibited in heterotrophic nitrification, and 50 mg/L nZVI reduced the phage growth, at which point phage DEY7 had the least inhibitory effect on nitrogen removal. In aerobic denitrification, total nitrogen (TN) and nitrate (NO3--N) removal was inhibited, but the inhibition was unaffected by increasing nZVI dosages. In addition, the kinetic analysis suggested that the change of TN concentration in the HN-AD process fitted with the pseudo-first-order reaction model. These results provide novel insights toward biological nitrogen removal by HN-AD bacterium in the presence of bacteriophage.