Experimental and simulation studies of two types of 5-inch scale hollow fiber membrane modules for pressure-retarded osmosis

This study experimentally and theoretically analyzed the performance of two types of large-scale hollow fiber (HF) forward osmosis (FO) modules for pressure retarded osmosis (PRO). The effects of operating conditions on the module performance of the 5-inch scale HF modules with a cross-wound HF configuration were investigated. A modified analytical model, based on the friction-concentration polarization (FCP) model, which combined the PRO theory with water flux and salt leakage, was proposed for PRO performance estimation. The theoretical results agreed within 9.7% deviation with the experimental results under all conditions. The energy efficiency of the HF PRO module was also theoretically derived. The power generation estimation for the 5-inch membrane module revealed that 10 to 15% of the energy could be recovered from the reverse osmosis seawater desalination process. However, some parts of the membrane could not be used efficiently inside the modules because of the non-optimal dimensions. Therefore, new types of modules, having shorter lengths and larger module diameters, were proposed and provided greater net energy output, as compared with the original module, due to the reduction of both the region where the water was not sufficiently permeated and the pressure drop inside the HF membrane.