Combined impacts of aluminum and silica ions on RO membrane fouling in full-scale ultrapure water production facilities

• Published in: Desalination Vol. 577; p. 117380
• Main Authors: Park, Daeseon, Yeo, In-Ho, Lee, Jiseon, Kim, Hyojeon, Choi, Seungju, Kang, Seoktae
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 18.05.2024
• Subjects: Membrane fouling; Polyaluminum chloride (PAC); Residual aluminum ions; Reverse osmosis (RO); Ultrapure water production (UPW); Ultrapure water production (UPW); Residual aluminum ions; Polyaluminum chloride (PAC); Reverse osmosis (RO); Membrane fouling
• ISSN: 0011-9164; 1873-4464
• DOI: 10.1016/j.desal.2024.117380

In this study, a fouled reverse osmosis (RO) membrane from a full-scale ultrapure water (UPW) facility was autopsied and investigated to propose the fouling mechanism and mitigation strategies. Although the influent was introduced to the coagulation and ultrafiltration as the pre-treatment processes, thick fouling layers were found over the entire RO surface. The foulant was mainly composed of aluminum silicates due to the elevated Al concentration (up to 100 μg/L) originated from the coagulation process utilizing polyaluminum chloride, and high recovery (up to than 90%) of RO process. Lab-scale fouling tests also confirmed that the elevated Al concentration in the RO influent contributed to significant flux decline due to a bridging effect with negatively charged organic matter and the formation of aluminum silicates. The application of polydiallyldimethylammonium chloride as an alternative coagulant successfully mitigated the organic and silicate fouling. Therefore, control of the residual aluminum ions originated from the coagulation process is critical to mitigate both organic and inorganic fouling on RO membrane surfaces during the production of UPW. •Major foulants of a full-scale RO process for ultrapure water were identified.•Aluminum silicate was the major inorganic matter in the fouling formation.•The use of PAC for coagulation contributed to the high potential for Al fouling.•Organic coagulants such as PolyDADMAC can alleviate inorganic fouling.