Nanoparticles applied in membrane bioreactors: Potential impact on reactor performance and microbial communities

Both aerobic and anaerobic membrane bioreactors (MBRs) are able to remove contaminants of emerging concern from wastewater at high efficiencies. However, the main bottleneck of this technology is membrane biofouling. Coating heavy metal nanoparticles on the surface of membrane has been proposed as an effective antifouling strategy. Nevertheless, metal nanoparticles can potentially result in detrimental impact on the overall functionality of the MBRs. This book chapter aims to understand how nanoparticles impact MBRs. To achieve this aim, the chapter starts off by illustrating the antibacterial mechanisms of nanoparticles. The chapter then critically reviews past studies that illustrate the antibacterial effect of nanoparticles against pure bacterial cultures and biofilm-associated populations. Finally, the chapter evaluates if the presence of nanoparticles would affect the overall performance of aerobic and anaerobic biological processes. Specifically, the impact of heavy metal nanoparticles on nitrogen and phosphorus removal process was discussed. The effect on anaerobic fermentation, which is comprised of hydrolysis, acidogenesis, acetogenesis, and methanogenesis, was also reviewed.