Computational Modeling and Energy Optimization of Reverse Osmosis Desalination under Fouling Effects and Variable Operating Conditions

Freshwater scarcity is one of the most pressing global challenges, driving the need for efficient and sustainable desalination solutions. Reverse osmosis (RO) has emerged as the leading approach due to its high salt rejection, operational flexibility, and lower energy use compared with thermal processes; nonetheless, membrane fouling and scaling remain persistent obstacles that degrade performance and raise costs. In this work, we develop a compact computational model for spiral-wound RO using the Engineering Equation Solver (EES) and validate it against the commercial WAVE tool, achieving over 90% agreement. Sensitivity analysis quantifies how feed pressure and a lumped fouling factor affect key indicators-permeate flow rate, recovery ratio, salt rejection, net driving pressure (NDP), and specific energy consumption (SEC). Higher feeding pressures increase permeate productivity but, under fouling, can substantially elevate SEC; increasing fouling reduces flux and recovery, lowers effective rejection, and raises SEC. These results underscore the need to optimize operating setpoint's and implement fouling control. In practice, integrating energy-recovery devices particularly isobaric pressure exchangers (PX) together with robust pretreatment reduces SEC and extends membrane life, improving the sustainability of RO plants.