Concentration Polarization at the RO Membrane

Every reverse-osmosis membrane fights a hidden enemy at its own surface: as pure water is pulled through, the salt it leaves behind piles up faster than crossflow turbulence can sweep it away, forming a thin high-salinity boundary layer that raises the local osmotic pressure and eats into the driving force the feed pump paid for. This simulator solves the coupled solution-diffusion and film-theory equations that govern that layer in real time — using a Sherwood-number correlation for a spacer-filled feed channel to get the mass-transfer coefficient — while a particle-based drift-diffusion simulation of individual salt ions renders the resulting concentration boundary layer directly: watch it thicken under higher pressure and thin out as you raise the crossflow velocity, while live readouts track permeate flux, the polarization factor β = C_w/C_b, and salt rejection.