A numerical study on concentration polarization and system performance of spiral wound RO membrane modules

The development of concentration polarization in a spiral wound reverse osmosis membrane channel and the depolarization effect of spacers are important concerns for understanding the performance of membrane processes. However, an accurate quantification of these effects derived from fundamental principles is impractical due to the complexity of the processes. In this study, a macroscopic method was developed to estimate the effect of concentration polarization on the performance of the spiral wound membrane modules. Concentration polarization in a channel filled with spacers was described as a combination of two extreme cases, namely the undisturbed concentration polarization and complete depolarization (uniform distribution across the channel height). With the introduction of a polarization factor for the degree of concentration polarization, a mathematical model was developed for the permeate flux in the spiral wound modules. The proposed model was solved numerically to simulate the performance of a long membrane channel under various operation conditions. The simulation results demonstrated that the model developed in this study was a feasible way to estimate concentration polarization in spiral wound modules. Excellent fitness was found between the numerical simulations and experimental observations of the average permeate fluxes in along membrane channel of spiral wound membrane modules.