Size-dependent transport and fouling formation of organic matters in a pilot-scale PFFO-RO hybrid system for real wastewater treatment

The forward osmosis (FO)-reverse osmosis (RO) hybrid system has been gaining considerable interest because of its wide applicability and feasibility in both wastewater treatment and seawater desalination. However, as the FO process treats wastewater in the hybrid system, fouling of the FO membrane is a crucial factor in the FO-RO hybrid system, which determines the performance of the entire hybrid system. A few studies have reported that the configuration of the PFFO module has potential advantages, such as a higher cross flow velocity, higher fouling resistance, and lower pressure drop compared to conventional spiral wound-type modules. In this study, the first to investigate the performance of the PFFO-RO hybrid system in long-term operation, the performance and fouling characteristics of the PFFO-RO hybrid system in real wastewater treatment, and seawater desalination over two months were investigated. At the end of the process, organic compounds, mainly humic substances such as humic and fulvic acid, accounted for 89.32% and 91.46% of the foulant on the PFFO and RO membranes, respectively. Moreover, organic compounds with molecular weights over 500 Da were removed by PFFO, and those over 60 Da were removed by RO. This study can provide the information about maintenance of the PFFO-RO hybrid process in wastewater treatment.