Solar-powered forward osmosis as a sustainable water treatment solution: A review

Abstract

Water scarcity is a critical challenge affecting economic growth, societal stability and ecosystem balance. Wastewater reuse and desalination have been recognized as viable methods for securing sustainable water supplies. Forward osmosis (FO), with its inherent advantages over energy-intensive reverse osmosis (RO), has gained significant attention as a promising technology for both wastewater reuse and desalination applications. However, a key challenge for FO is the regeneration of the draw solution, which is a high-energy step needed to recover the water and reuse the draw solute. One potential solution to address both the water and energy challenges is the integration of solar energy into FO systems. This can be achieved by using solar energy to power the draw solution regeneration process, thereby reducing dependence on conventional energy. This review provides a brief overview of FO emerging applications across various fields, with a particular focus on the integration of solar energy for draw solution regeneration, including the use of photovoltaic (PV) systems, solar thermal systems, photovoltaic thermal (PVT) systems and solar-driven interfacial evaporation. The energy demands of draw solute recovery and the role of solar energy in FO are elucidated, along with the challenges and perspectives of scaling solar-driven FO systems. While it remains uncertain whether solar-powered FO can achieve the cost advantages of large-scale operations comparable to RO, its potential integration with other membrane and non-membrane processes presents significant opportunities for further techno-economic studies to evaluate its viability alongside conventional RO processes. Finally, target factors and translation into real-world applications are presented.