TOWARDS EFFICIENT DESALINATION: MODELING, PILOTING, AND FOULING CONTROL IN BATCH REVERSE OSMOSIS SYSTEMS

Conventional reverse osmosis (RO) is the most commonly used desalination method due to its high salt rejection efficiency. Despite advances in membrane materials, energy recovery devices, and high-efficiency pumps, RO systems suffer from high energy consumption and water cost. To address these challenges, alternative configurations, such as transient RO processes (i.e., semi-batch RO and batch RO), are thought to be energy-efficient variants. These transient processes are dynamically time-dependent and pressure-driven that can desalinate feed water by cycling the brine through the RO membrane module. Fair comparisons between RO configurations are lacking, hybrid renewable systems have yet to demonstrate economic viability, and claims of improved biofouling resistance in transient processes are not yet validated at demo-scale.

This thesis introduces a theoretical implementation of semi-batch and batch RO processes in large seawater RO facilities incorporating the most efficient equipment, pre-treatment methods, and enhanced RO membranes. The results suggest that the implementation of semi-batch and batch RO can significantly reduce the overall specific energy consumption of seawater RO facilities beyond the thermodynamic minimum by 69% and 82%, respectively. Hybridizing batch RO with a renewable energy method capable of harvesting osmotic power can further reduce the desalination energy consumption and serve as a demand-response strategy to supply electricity back to the grid. The hybrid configuration reduced desalination energy consumption by up to 26.6% compared to conventional RO and 10.2% compared to stand-alone batch RO.

Biofouling shortens RO membrane lifespan, lowers permeate flux, and increases pressure requirements. Lab-scale experiments comparing conventional and batch RO systems demonstrate that the salinity cycling in batch RO significantly mitigates biofouling and enhances water flux. Building on these findings, we aim to transition from theory and lab-scale validation to a full pilot-scale system. This pilot, developed through integrated system design, modeling, and experimental validation, will enable a comprehensive comparison of conventional, semi-batch, and batch RO modes - showcasing the operational advantages of batch RO in terms of efficiency, fouling resistance, and energy savings.