Hollow fiber type PRO module and its characteristics

Abstract Seawater desalination reverse osmosis, SWRO, is expected to be a promising process to solve the problem of water scarcity. However, higher cost-effectiveness and less energy consumption are required for SWRO plants. Forward osmosis, FO processes using the comparable permselective membranes same as RO have gained renewed interest in recent years, and they might become a solution for the most challenging problem of water and energy scarcity. This FO process is expected to have capability of applying energy-saving seawater desalination and power generation by Pressure Retarded Osmosis, PRO. Especially, the PRO technology has drawn attention as a process that could recover energy from the salinity difference between the concentrated brine from SWRO plant and pure water and reduce energy consumption of SWRO plant. A Cellulose triacetate (CTA) hollow fiber type PRO module has been developed and PRO probabilities have been investigated by operating at a prototype PRO plant. The PRO module has characteristics similar to RO module such as high selectivity, chlorine resistance and sufficient pressure resistance. A CTA hollow fiber type PRO membrane module can be expected to have superior fouling resistance compared to a polyamide PRO membrane module from the viewpoint of chemical property such as chlorine resistance. The performance of the PRO module was investigated and analyzed by a hollow fiber type FO module analytical model. The investigation has found that this analytical model based on solution–diffusion model was applicable to the CTA hollow fiber type PRO module. The PRO module configuration and operating condition are expected to be optimized more effectively by this analytical model in the future.