On the performance limitation of reverse osmosis water desalination systems

The performance of Reverse Osmosis (RO) water desalination processes was investigated using a simulated brackish water plant based on spiral-wound membranes. A semi-rigorous mathematical model was employed in the simulation to calculate the water and salt fluxes at any point along the filtration channel. The effects of two key parameters, namely the transmembrane pressure and membrane surface area, on the performance of the process were investigated. Some insights into the performance limitation of RO processes were obtained. The rapid increase in the osmotic pressure of the brine was found to be the main factor which limits the performance of the plant. The study has also revealed that any attempts to develop new membranes for brackish water desalination which withstand higher operating pressures than 4.5 MPa will not result in significant gains in the plant performance. For seawaters having high salinity, the development of membranes, which operate at a pressure of up to 10 MPa, will significantly improve the membrane's productivity.