Non-toxic properties of TiO and STiO nanocomposite PES ultrafiltration membranes for application in membrane-based environmental biotechnology.

In membrane bioreactor (MBR) technology, nanocomposite membrane has a great potential to improve the filtration performance and antifouling. However, antibacterial activity of nanoparticles (NPs) is a significant disadvantage which can be impacted to bacterial growth and microbial community in MBRs. The modified polyethersulfone (PES) ultrafiltration (UF) membranes in the study were prepared by using TiO NPs and TiO NPs functionalized with sulfonation (STiO). The antibacterial effect of NPs and non-toxic properties of nanocomposite membranes were examined by using three different Gram-negative bacterial species isolated from a local full scale membrane bioreactor treating municipal wastewater (Escherichia coli, Pantoea agglomerans, and Pseudomonas graminis). Results are revealed that the TiO and STiO NPs have 60% of antibacterial activity based on disc diffusion, viability tests, and TEM analysis. However, the PES-TiO and PES-STiO nanocomposite UF membranes showed significantly lower antibacterial activity (<95%, significance at p < 0.0001), indicating innocuous to bacterial growth. This study highlights that the PES-TiO and PES-STiO nanocomposite membrane is more sustainable than PES membrane and promising materials for MBRs, by taking advantage of non-toxic properties to bacterial growth.