Fouling characteristics and cleaning strategies of reverse osmosis membranes at different stages in a wastewater reclamation process

Membrane fouling is the main issue impeding reverse osmosis (RO), a crucial technology for the wastewater reuse process. This study systematically investigated the composition of membrane foulants at different positions on the RO element and the main causes contributing to membrane fouling using membrane autopsy in a pilot-scale RO process for wastewater reclamation. Membrane foulants were analyzed quantitatively and qualitatively using two fouled RO membrane elements from various vessels. The results revealed that the lead RO membrane suffers more severe membrane fouling, which mainly consists of organic matter (aromatic protein-like and soluble microbial product-like) and biofilm. The inorganic fouling, such as Ca, Fe, and Na, is the major foulant composition of the tail RO membrane. The physical cleaning process showed insufficient flux recovery in both fouled RO membranes. The alkaline cleaning was more effective for the lead-fouled membrane, while the acid cleaning was more effective for the tail-fouled membrane. This study offers control strategies for wastewater reclamation as well as a thorough comprehensive knowledge of the composition of membrane fouling and its major contributors at various locations along the RO membrane.