Energy-saving "NF/EDR" integrated membrane process for seawater desalination Part I. Seawater desalination by NF membrane with high desalination capacity

In this study, an energy-saving nanofiltration/Reverse electrodialysis (NF/EDR) integrated membrane process for seawater desalination was proposed and about a total desalination removal of 99% could be obtained. The system energy consumption was < 2.15KWh/m [3], which is close to the most advanced level and the Total Dissolved Solids (TDS) of produced water was lower than 250 mg/L, the lowest can be 70---90 mg/L, demonstrating that the integrated system is an economically feasible and efficient desalination system. This paper is an important part of this system about the study on NF process, where a NF90-4040 membrane element with high desalination capacity was chosen by comparing the separation performance of the existing NF membranes at home and abroad, and the effects of operation pressure, feed concentration, stream temperature and feed flow on NF process were discussed in detail. The results showed that with the NF90-4040 membrane element, approximately 90% of the system desalination removal (SDR) was achieved, which was much higher than that of regular NF membranes. Furthermore, a NF system with an energy recovery device (ERD) was constructed. Compared with the NF system without ERD, the energy consumption of the ERD-based system was reduced by 46.4%. All the results are beneficial to the development of new integrated routes for seawater desalination based on high desalination capacity NF membrane, which is expected to play a significant role in the “NF/EDR” integrated membrane process.