Pressure retarded osmosis for power generation and seawater desalination: Performance analysis

The present study evaluated the performance of pressure retarded osmosis-reverse osmosis (PRO-RO) process for power generation and seawater desalination. Two pre-developed software were used separately to estimate the performance of forward osmosis (FO) and RO process. The draw and feed solutions in the FO process were seawater and low-quality water; i.e. wastewater effluent and brackish water. The simulation results showed that the FO performance increased with increasing seawater salinity and decreased with increasing feed water TDS. Increasing the feed and draw solution flow rate resulted in an increase in the FO performance especially when brackish water was used as a feed solution in the FO process. Power generation from the PRO process was found to increase with increasing the TDS of seawater and the flow rate of feed and draw solutions. The simulation results, however, showed that the PRO process was more sensitive to the increase in the seawater TDS than the flow rate of feed and draw solutions. For fresh water supply, the diluted seawater from the FO process was treated by RO membrane system. Up to 31% decrease in the desalination power consumption can be achieved by the PRO-RO process. It was also found that the increase in the draw solution flow rate resulted in an increase of the permeate concentration and power consumption. This issue should be considered in the operation of the PRO-RO system in order to reduce the overall treatment cost.