Scientific Contributions

Seawater reverse osmosis (SWRO) membrane systems face inevitable performance decline due to biofouling, which imposes significant economic costs, accounting up to 25 % of water production costs in desalination plants. Current industry practices primarily rely on chemical cleaning treatments to restore membrane performance. However, these methods involve substantial expenses related to chemical acquisition, storage, and transportation, extended plant downtimes, and premature membrane replacement due to reduced lifespan. Additionally, the disposal of chemical waste raises serious environmental concerns. Micro-nano bubbles (MNBs), consisting of gas-filled cavities (from <1 μm to 5 μm in diameter), have emerged as a promising alternative for biofouling control. This study evaluates the performance of the air-filled (AMNBs) and CO2-nucleated bubbles (N_CO2) as curative cleaning-in-place (CIP) treatments and preventive daily treatments under conditions representative of SWRO systems. Using membrane fouling simulators (MFSs) and pressure drop as a performance indicator, curative AMNBs, and N_CO2 treatments achieved 49 %–56 % pressure drop recovery, comparable to conventional chemical cleaning (51 %) and significantly outperforming hydraulic flushing (24 %). Optical coherence tomography (OCT) imaging and biomass analyses confirmed these findings, revealing effective biofilm removal due to MNB's action. Preventive treatments demonstrated that Nucleated CO2 bubbles delayed performance decline by 123 %, AMNBs by 95 %, and hydraulic flushing by only 15 % compared to controls. OCT imaging and membrane biomass analysis confirmed reduced biofilm growth and biomass accumulation in bubble-treated systems. These results indicate that MNB technologies hold great potential as a sustainable and eco-friendly alternative to chemical cleaning for biofouling management in SWRO systems.