Several engineering equations in the design of reverse osmosis plants

Concentration of aqueous urea and propylene glycol solutions was carried out by reverse osmosis using two composite membranes (PEC-1000 and FT3O(SW)) under the following conditions: pressure 2.0–6.0 Mpa; temperature 10–60°C; concentration 1000 ppm. With the increase of operating temperature membrane permeation flux exponentially increases and solute rejection slowly decreases. The dependence of solute rejection on temperature is not only related to membranes but also related to solutes. Solution permeability, L p and solute permeability ω strongly depend on operating temperature, bus reflection coefficient σ seems independent of temperature. Two equations for L p, and ω as a function of operating temperature were presented and applied to experimental data. Two expressions of permeation flux correction factor (PFCF) and solute passage correction factor (SPCF) were derived, and the effects of operating variables such as temperature, pressure and concentration on membrane performance were estimated, correcting the membrane performance from standard conditions to operating conditions.