Nanofiltration of Greywater to Remove Micropollutants

Global freshwater resources are currently experiencing increasingly high stress due to extreme weather events brought along by climate change and the ever-growing global population. To protect these natural resources while meeting the growing water demand, local solutions, such as the reclamation of domestic wastewater, have gained interest. Implementing source-separated sanitation concepts, where toilet water (blackwater) is separately collected from all other sources of domestic water (greywater), can enhance the ease of recovery of nutrients, energy, and water. Biological greywater treatment systems have been implemented in recent decades, opening the door to the potential reuse of this stream. However, the occurrence of micropollutants has limited the full-scale adoption of greywater treatment plants for water reclamation. Micropollutants are substances found at trace concentrations (ng.L-1 - µg.L-1) in wastewater that could harm the environment when discharged. Therefore, post-treatment solutions are required to reduce the discharge of micropollutants by treatment plants and limit the risks posed by these substances during reuse. One promising post-treatment technology is the use of hollow-fiber nanofiltration membranes. These membranes have proven effective barriers for micropollutants in lab-scale experiments and have recently become commercially available for large-scale applications. However, translating lab-scale results to real-world applications is not straightforward. Further knowledge is needed to determine the role these membranes can play in greywater treatment. This thesis investigates the applicability of the polyelectrolyte multilayer based hollow-fiber nanofiltration membranes as a post-treatment for removing micropollutants during greywater treatment. Key factors, such as the water matrix, influence of fouling, and effective membrane integrity monitoring solutions, were investigated to study the applicability of these newly developed membranes in greywater treatment systems. This thesis showed the potential of hollow fiber nanofiltration as an additional treatment step for removing micropollutants from greywater. While high retentions of micropollutants could be achieved under controlled conditions, full-scale implementation of hollow-fiber nanofiltration in greywater treatment systems still requires further research. Topics, such as the effects of nanofiltration concentrate recirculation and the further valorization of the permeate, need further research to unlock the full potential of hollow-fiber nanofiltration in greywater reclamation systems.