Numerical Modeling Of Gypsum Dissolution Mechanism in Roto-dynamic RO Systems at Seawater Salinity.

Concentration polarization (CP) and mineral scaling are significant challenges in reverse osmosis (RO) systems, particularly for brackish and seawater desalination. These phenomena adversely affect membrane performance, reducing efficiency and lifespan. This study aims to address these limitations by investigating the effects of intermediate membrane wash enhanced with induced shear and flow dynamics on CP and gypsum scaling. A numerical framework has been developed to simulate the dissolution of gypsum scale formation during desalination at seawater salinity of 0.5 M over the RO membrane. This study introduces a dissolution mechanism in the proposed novel roto-dynamic RO system, where we have shown the numerical investigation of gypsum scaling at different feed and operational conditions. Here we will take the scaling condition as initial condition to model the intermediate membrane wash process involves depressurization of RO unit to 1 bar, and letting the dynamic flow effectively reducing CP and dissolving scale deposits. Enhanced shear is achieved by rotating the fluid over the RO membrane with the help of rotating disk called rotor, increasing shear rate and species transport. This dynamic mechanism demonstrates the potential to mitigate scaling, thereby improving membrane performance and operational sustainability. The findings provide a basis for optimizing RO systems and advancing sustainable desalination technologies.

We have combined a moment-based population balance method for modeling nucleation and crystal growth with CFD solver (ANSYS-Fluent) for simulating the viscous fluid flow, reactive species transport, permeate flow through the membrane, concentration polarization, mass transfer from dissolved phase to the solid crystal/precipitate (scale), permeability loss of membrane and reduction of permeate discharge. Here we will be also showing the modeling of scale dissolution for at different flow condition for the overall optimal operation of the proposed rotodynamic RO system.