Reverse osmosis (RO) and nanofiltration (NF) membranes provide high levels of treatment for microbial and chemical pollutants alike. They play key roles in desalination, potable reuse projects, and many challenging industrial purification applications. Several regulations focusing on the control of waterborne diseases impact treatment systems employing RO and/or NF. Removal of waterborne microbes and pathogens is measured by the microbial log removal value (LRV); however, the industry standards for assessing LRV underestimate the actual LRV from RO and NF processes. This project sought to bridge this discrepancy by identifying direct integrity test (DIT) methods and performing long-term validation testing to demonstrate Giardia, Cryptosporidium, and enteric virus LRV credit for high-pressure RO and NF membrane systems. Research partner: California State Water Resources Control Board. Published in 2023.