Membrane-based seawater desalination technology is represented by reverse osmosis. Its principle involves using high pressure to drive seawater through a semi-permeable membrane, separating water molecules from salt ions. Due to the high osmotic pressure of seawater, the system requires a high-pressure pump to provide sufficient pressure (typically 5–8 MPa), along with high-desalination-rate membrane materials (such as composite polyamide membranes). The advantages of this technology are relatively low energy consumption and strong system modularity, making it the most widely used mainstream technology globally.
Thermal seawater desalination technologies mainly include multi-stage flash evaporation (MSF) and multi-effect distillation (MED). These technologies heat seawater to vaporize it, then condense it into fresh water, achieving brine separation. MSF improves efficiency through multi-stage reduced-pressure flash evaporation, while MED utilizes multi-stage evaporators to reuse heat energy. Thermal technologies are suitable for integration with power plant waste heat or industrial waste heat, but they have high energy consumption and require large-scale equipment.
Other emerging technologies include electrodialysis, forward osmosis, and hybrid processes. Electrodialysis uses an electric field to drive ions through ion-exchange membranes for separation, making it suitable for low-salinity water treatment. Forward osmosis uses osmotic pressure difference to drive water migration. Hybrid processes combine membrane methods with thermal methods or pretreatment technologies to improve overall efficiency and stability.
At the systems engineering level, seawater desalination technology also includes crucial pretreatment and energy recovery technologies. For example, pretreatment methods such as sand filtration and ultrafiltration reduce fouling loads and extend membrane life; energy recovery devices (ERD) recover the pressure energy of concentrated brine, significantly reducing operating energy consumption. Overall, seawater desalination technology is a comprehensive water treatment system centered on reverse osmosis and supplemented by the synergistic optimization of multiple processes.