Multi-stage Roto-dynamic RO System for Desalination.

Concentration polarization (CP) in reverse osmosis (RO) based desalination filters reduces operational efficiency, leads to membrane scaling and increases maintenance costs. This paper presents a multi-stage roto-dynamic RO system designed to address these issues by combining multiple rotating RO modules in series, each equipped with a rotor-stator configuration to enhance mass transfer and fluid flow over the porous RO membrane. The system promotes self-cleaning and controlled feed pressure, resulting in higher permeate discharge, with effective permeability reaching up to 0.3 LMH/Bar compared to 0.2 LMH/Bar in conventional spiral-wound RO module at seawater salinity of 547 mol/m3 and 55 Bar feed pressure. The specific energy consumption (SEC) of the multistage roto-dynamic RO system in the present study is 1.93 - 2.55 kWh/m³ while the typical range of SEC for conventional spiral-wound RO (SWRO) systems is 2.5 - 4 kWh/m³. In addition, the rotodynamic RO system is advantageous because it can maintain a high permeate production rate with less fouling and scaling. This is mainly due to the delayed onset of concentration polarization (CP) and the implementation of intermediate membrane cleaning through high cross-flow

velocities.

Keywords: Seawater desalination, Multi-stage Roto-dynamic RO System, Concentration Polarisation.