Megaton Water System: High Salinity Pressure Retarded Osmosis

Abstract Seawater reverse osmosis (SWRO) plants are facing significant problems, such as energy reduction and disposal management of concentrated brine. In order to solve those problems at the same time, the energy recovery with purification of advance treatment of sewage by Pressure Retarded Osmosis (PRO) was proposed in the Mega-ton Water System Project, under the Japanese national project of “Funding Program for World-Leading Innovative R&D on Science and Technology” (FIRST Program). PRO prototype plant test was conducted using concentrated brine from a SWRO plant and fresh water from regional wastewater treatment facility. CTA hollow-fiber membrane modules were examined in the PRO prototype plant and the test operation was carried out for more than 1 year. We have reached the maximum membrane power density, 13.5 W/m 2 , using 10-inch module. Following were still existing obstacles for further effective PRO. It was also challenging how to get clean fresh water from waste or river water without additional cost. Innovative new technologies were also required to address these concerns. We have also done plant cost estimation and surveyed financial impacts on the energy saving of SWRO operation, based on the situation of currently operated SWRO plants worldwide, especially about those of the Megaton scale. Those studies indicated that the potential market of PRO was 1–2 GW, and 10% energy saving was possible on the Megaton scale SWRO plants. Those results indicate that the commercialization plant would be available in the very near future.