Reverse Osmosis–Pressure Retarded Osmosis hybrid system: Modelling, simulation and optimization

• Simulation and sensitivity analysis of integrated SWRO-PRO system configurations for eliminating brine post-treatment step. • Identification of energy efficient novel SWRO - PRO hybrid desalination process for reducing the SWRO pre-treatment cost. • Method for optimization of hybrid SWRO-PRO system design and operating parameters to achieve minimum NSEC.

Mathematical model for SWRO–PRO hybrid system was developed and implemented in Modelica language using Dymola software tool. The verified individual process unit models are used for SWRO–PRO flowsheet simulation studies and the following observations were made: • When sea water was used as feed solution for PRO, the SWRO–PRO hybrid system is found to be an unsustainable system with respect to SWRO system. • This is mainly due to severe ICP in PRO unit. Unless the ICP is nullified with help of innovative PRO membranes, the self-sustainable SWRO– PRO configuration may not be viable if sea water is used as a FS solution. • When water waster was used as FS for PRO, the SWRO–PRO hybrid system was found to be energy efficient solution for desalination application.