Impact of iron-based nanoparticles on microbial denitrification by Paracoccus sp. strain YF1

• Impact of iron-based nanoparticles on microbial denitrification by Paracoccus.
• Adding Fe or Fe/Ni led to a decrease in cell growth and denitrification.
• The solution pH and temperature impacted on the nitrate removal and bacterial growth.
• SEM, XRD and EDS used for the characterization of change of surface of Fe or Fe/Ni.

This study investigates the effects of Fe and Fe/Ni nanoparticles on biological denitrification when using Paracoccus sp. strain YF1. Results show that adding Fe and Fe/Ni nanoparticles to the cells decreased their growth and denitrification rate. Compared to that of free cells (control 89.47%), a decrease (64.33%) in the presence of 1000 mg/L Fe/Ni nanoparticles was observed, while a small decline in the denitrification rate (76.36%) was obtained when the concentration of Fe nanoparticles was 1000 mg/L. These were further confirmed by adding Fe2+, Fe3+, Fe3O4, Fe2+/Ni2+ and Fe3+/Ni2+ individually to the free cell system. Furthermore, Fe and Fe/Ni nanoparticles influenced the nitrate removal and bacterial growth under different pH and temperature conditions. SEM, XRD and EDS demonstrated that iron oxides formed as a result of nanoparticles corrosion in biological medium. Finally the presence of nanoparticles around some bacteria was observed.