Osmotic energy recovery from hypersaline waters, such as produced water from oil and gas reservoirs and concentrated brine, is strategically significant to water utilization and sustainable energy production. Much attention has been given to pressure-retarded osmosis (PRO) as a potentially viable process for osmotic energy recovery. To predict the performance of various operable PRO configurations in conjunction with prior art membranes, a robust simulation tool has been developed in this work that is based on an equation of state for electrolyte solutions and a detailed mass transfer model. The salinities of draw and feed inlet streams are specified such that they are representative of produced water and seawater, respectively. By integrating fluxes over discrete elements, the simulator is able to capture the effects of continuous dilution on thermodynamic property profiles across the membrane area. This has implications for the scalability of coupon-scale power density measurements. The quantitative impact of electrolyte solution non-ideality on calculated energy recovery is evaluated based on a representative PRO process configuration. (C) 2019 Elsevier Ltd. All rights reserved.