A stepwise approach to predict the performance of forward osmosis operation: Effect of temperature and flow direction

The objective of this research was to use a stepwise approach to develop a temperature-dependent prediction model for scale-up of forward osmosis. A Sobol sensitivity analysis confirmed that water permeability (A) of Forward Osmosis (FO) membrane has significant effect on water flux while salt permeability (B) has limited impact. Statistical analysis indicated that the stepwise model prediction provided improved agreement with experimental measurements of water and salt fluxes compared to prediction from a lumped parameter model over the range from 15 °C to 35 °C. The temperature predictions from the stepwise model were in close agreement with experimental temperatures; with deviations of less than 0.2 °C. When simulated with the increase in the length and width of the flow channel, the differences in predictions between the stepwise and lumped model increased. These results emphasize that parameter variations along the channel length should be accommodated by the stepwise model. In simulations using the stepwise model, the co-current flow mode was found to generate higher water flux than the counter-current flow mode. The results and analysis from this investigation demonstrate the advantages of the stepwise model for prediction of water flux for scale-up of FO operations.