Energy and economic assessment of high-recovery seawater desalination integrated with pressure-retarded osmosis: Employing high-pressure RO, high-pressure NF, and low-salt-rejection RO

초록

To improve the energy efficiency and water productivity of seawater desalination, high-recovery reverse osmosis (HRRO) processes targeting 65–75% recovery are attracting significant interest, yet their integration with pressure-retarded osmosis (PRO) using hypersaline concentrate as a draw solution remains insufficiently explored. This study systematically compares PRO integration across three distinct HRRO configurations—SWRO–HPRO–MS, SWRO–SWRO–HPNF, and LSRRO—employing process models validated with pilot data and commercial software. PRO integration via pressure exchangers (PX) consistently reduces the SEC by 0.11–0.28 kWh/m3 and the levelized cost of water by 0.010–0.016 $/m3 compared to standalone HRRO, whereas Pelton turbine-based systems increase net costs. The SWRO–HPRO–MS–PRO/PX configuration achieves superior energetic and economic performance due to its efficient stage-wise pressure distribution. However, sensitivity analysis across varying seawater temperatures (5–30 °C) and salinities (30–40 g/L) reveals operationally infeasible regions under high-salinity, low-temperature conditions due to mechanical pressure constraints. These findings map the performance boundaries and configuration-specific trade-offs of HRRO–PRO hybrids, offering a quantitative basis for site-specific optimization in sustainable high-recovery desalination deployment.

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