Investigation of Ag and magnetite nanoparticle effect on the membrane fouling in membrane bioreactor

Abstract

In this study, Ag nanoparticles (Ag NPs) as antibacterial substance and Fe3O4 nanoparticles (Fe3O4 NPs) as magnetic material were synthesized and then utilized in the MBR system (Ag NPs-MBR/Fe3O4 NPs-MBR), and for synthetic petrochemical wastewater treatment, their effect on biomass characteristics and consequently effect on membrane fouling was evaluated. Chemical oxygen demand (COD), extracellular polymeric substance (EPS), soluble microbial product (SMP), flux, membrane fouling resistance, as well as particle size distribution, Fourier transform infra-red (FTIR) spectroscopy, and scanning electron microscope (SEM) analysis were performed for performance evaluation. The average particle size of Fe3O4 NPs and Ag NPs was 2 and 10 nm, respectively. It was observed that overall, the application of nanoparticles results in better removal of organic matter in the system. Control-MBR, Ag NPs-MBR, and Fe3O4 NPs-MBR reduce COD by 80, 96.64, and 95.35%, respectively. Besides, improvement in flux rate by 41% and 32% for Ag NPs-MBR and Fe3O4 NPs-MBR was observed, respectively. EPS in Ag NPs-MBR and Fe3O4 NPs-MBR decreased by 49% and 38%, while SMP decreased by 66% and 54%, respectively. The FTIR analysis also confirmed the reduction in EPS and SMP. SEM images revealed that the cake layer on the membrane in the Ag NPs-MBR system has more porosity. Based on the results, the application of NPs in MBR systems leads to significantly improved performance and reduced membrane fouling.