The impact of iron bimetallic nanoparticles on bulk microbial growth in wastewater

Nanoscale zerovalent iron particles (nZVI or Fe⁰) have been widely used in wastewater treatment and their effect on mixed community bacteria is still under investigation. In this study, we demonstrated that it is possible to enhance the bacterial growth and accomplish biological wastewater treatment using Fe⁰-based nanoparticles. In a first step, nZVI particles were added to a mixed bacterial community by three different concentrations (50 mg/L, 1000 mg/L, and 5000 mg/L) and bacterial growth was recorded for 12 days of operation. In addition, the reactivity of nZVI was enhanced by adding a second metal to form the so-called bimetallic nanoparticles. Bacterial growth increased by 53.84 % and 84.61 % when exposed to nZVI and Cu/nZVI treatment, respectively. Transmission Electron Microscope (TEM) and X-Ray Diffraction (XRD) characterizations showed that Cu/nZVI nanoparticles presented higher dispersibility and lower agglomeration than bare nZVI. Also, chemical oxygen demand (COD) removal efficiency increased up to 33.21 %, 55.30 %, and 61.24 % in control, nZVI, and Cu/nZVI reactors, respectively. The medium change effect on bacterial cells growth was investigated and results showed that microbial colonies exhibited higher sensitivity to nZVI treatment in a different studied medium. System conditions were varied, and the variation of oxygen concentration could alleviate the negative effect. The study proved that nZVI and copper/Fe⁰ nanoparticles exhibited a positive effect on bacterial growth originated from a mixed culture inoculum as well as on the biological wastewater treatment. However, the medium showed a high sensitivity when the organic matter content was changed.