Virus removal of new and aged UF membranes at full-scale in a wastewater reclamation plant

Abstract

Ultrafiltration (UF) membrane technology is widely used in water recycling schemes as a physical barrier for the removal of human pathogens. Assessing the consequence of long-term operation (membrane ageing) as well operational extremes on pathogen removal performance is crucial for assessing health risks of human exposure to recycled water. In this study, challenge testing with MS2 bacteriophage (MS2) was undertaken to validate the integrity of full-scale UF membranes used for virus removal in a wastewater recycling plant (WRP). Validation was performed on new (6 months old) and aged (6 years old) membrane units. The impact of a hazardous event—in the form of a short-lived, high turbidity spike—was also assessed since this event affected the hydraulic throughput of exposed membrane units. Validation of the new membranes demonstrated a mean virus log removal value (LRV) of 3.0 log₁₀ (SD = 0.6), with 5th and 95th percentile values ranging between 2.3 and 3.9 log₁₀ units. Re-validation of the membranes exposed to the hazardous event as well as those that were aged demonstrated that the virus LRV was comparable and had reduced by 1.0 log₁₀ units, measuring 2.0 log₁₀ (SD = 0.2), however the LRV performance was more stable, where the 5th and 95th percentile values ranged between only 1.7 and 2.2 log₁₀ units. Very little research has previously examined the consequence of membrane ageing or hazardous events on the LRV performance of full-scale UF systems, and thus the findings presented here will facilitate improvements in risk management, in the design of installations and in the operation of UF membrane systems.