Influence of operating state of a pilot-scale ultrafiltration system on virus removal for potable water reuse

Abstract

Ultrafiltration (UF) membranes are widely used in potable water reuse, but their virus removal capabilities can be underestimated due to operational variability and membrane damage over time. This study evaluates the log reduction values (LRVs) of a pilot-scale UF system continuously processing tertiary treated wastewater, focusing on a compromised membrane. Virus removal was assessed under various operational states, including physical backwash (PBW) and chemically enhanced backwash (CEB). Samples were collected after CEB, before PBW, and after PBW. Indigenous viruses such as AiV, NoVGII, enteric AdV, PMMoV, CGMMV, and crAssphage were quantified using (RT-)qPCR, alongside spiked MS2 bacteriophage. A laboratory-scale study examined the synergistic effects of hydraulic and chemical stresses, with deteriorated membrane fibers analyzed through field emission scanning electron microscope (FE-SEM), SEM equipped with energy-dispersive X-ray spectroscopy (SEM-EDS), and liquid–liquid displacement porometry (LLDP). Despite structural damage and fouling observed in compromised fibers, the Kruskal–Wallis test revealed no significant differences (p > 0.05) in virus removal across operational states, indicating consistent UF performance. Laboratory-scale MS2 filtration studies showed a significant effect of water quality on increasing LRV (p < 0.05) in compromised fibers. This study underscores UF systems’ robustness in virus removal and highlights membrane integrity loss pathways in real-world applications.