Evaluation of Drinkable Water Permeation through the Membrane of a Centrifugal Reverse Osmosis Module*

Fluid permeation in membranes is a complex process influenced by pressure gradient, solute concentration, membrane permeability, and fluid dynamics. Understanding these mechanisms is crucial for optimizing desalination systems. Two distinct approaches are widely used to evaluate the mass transport in desalination membranes: the thermodynamic equilibrium-controlled (TEC) approach and the mass transfer-controlled (MTC) approach. The TEC approach assumes that the local osmotic pressure is equal to the transmembrane pressure with infinite permeability, without taking the membrane properties into account, whereas the MTC approach considers membrane permeability and area to evaluate water recovery. In the present study, the water recovery rate and specific energy consumption of a novel centrifugal reverse osmosis (CRO) module are evaluated using both approaches for different feed flow rates. The pressure accumulation in the CRO module due to centrifugal forces is computed through computational fluid dynamics (CFD) simulations. The feed flow rate has effects only in the MTC approach. For a larger flow rate, the evaluated operating pressure of the CRO module is found higher in the MTC approach to achieve a certain water recovery rate. Both approaches show similar results at very low flow rates such as 0.01 GPM. The net specific energy consumption of CRO is 30% less than that of RO in the TEC approach for a 50% water recovery rate as reported previously, and this amount decreased to 18% for the more realistic MTC approach for a 0.1 GPM feed flow rate.