Intentional Fouling Enabled In Situ Healing of Compromised Reverse Osmosis Membranes for Desalination and Water Purification

Reverse osmosis (RO) membranes used for desalination and water purification commonly get damaged due to the increase of differential pressure, abrasion with the abrasive components in the feedwater, oxidation, and even degradation with periodical cleaning, resulting in a low-quality product water. Herein, we propose an in situ membrane healing method by temporarily filtering contaminated water (e.g., containing organic foulants) through damaged sites under increased hydraulic drag during filtration, healing the damaged sites by organic pollutants. The filtration performance of the pristine, compromised, and healed membranes was examined in terms of water flux, salt rejection, virus retention, and boron rejection. The healed membrane by organic foulants exhibited nearly equivalent selectivity and water flux to the pristine membrane and showed excellent stability against chemical cleaning. Filtration of the real surface water showed an even faster healing process than synthetic feedwaters containing a single organic foulant or mixed organic foulants. Mechanistic analysis showed that the abrupt increase of water flux at the damaged site induced the fast deposition of foulants followed by compaction under high hydraulic pressure. Our present study demonstrates that the in situ healing protocol is an effective and feasible approach to heal the compromised membrane and ensure the operational stability of RO membrane systems.