Energy Efficient Forward Osmosis to Maximize Dewatering Rates

Forward osmosis (FO) is a membrane separation process driven by the osmotic pressure difference between a high-salinity draw solution (DS) and a low-salinity feed solution (FS). This pressure-free dewatering method is highly energy efficient, making it suitable for concentration and resource recovery. However, conventional FO systems using series-connected modules suffer from progressive DS dilution and FS concentration, leading to a reduction in the osmotic driving force and thereby limiting the overall performance. To address this issue, we propose a novel hybrid FO module configuration in which the FS flows in series while the DS is split and distributed in parallel across moules. This configuration was evaluated using an experimentally validated FO module model and RO simulation tools. Under seawater (600 mM NaCl) as DS and brackish water (10 mM NaCl) as FS, a conventional three-stage FO module achieved an enrichment ratio of 2.5 with an energy consumption of 0.151 kWh/m3. In contrast, the proposed draw solution split distribution (DSSD) achieved an enrichment ratio of 12.5 at a reduced energy consumption of 0.137 kWh/m3. In comparison, a reverse osmosis system consuming 0.58 kWh/m3 achieved a similar enrichment ratio of 12.3. These results demonstrate the high energy efficiency and dewatering capacity of the proposed FO configuration, highlighting its potential for industrial applications in food processing, beverage production, pharmaceuticals and agriculture.