Emerging desalination technologies: Current status, challenges and future trends

Emerging technologies present many new possibilities for diversifying the desalination industry, which is currently dominated by thermal desalination, and reverse osmosis. In this review, we highlight recent developments in emerging desalination technologies, focusing on those nearing commercialization i.e. forward osmosis and membrane distillation, as well as electrochemical processes that hold potential for technological maturity and upscaling. Literature shows that emerging desalination technologies have benefited greatly from advances in nanomaterials. However, a membrane-based approach alone will not realize commercialization of forward osmosis or membrane distillation. In the case of forward osmosis, appropriate selection of draw solute as well as low-cost recovery of the draw solution towards low energy consumption will be important in full-scale commercialization. In membrane distillation, use of low-grade heat as well as hybrid systems driven by renewable energy sources are likely to facilitate growth. We also review advances in smart process monitoring and control through innovative in situ methods that can further lower operational costs associated with manual sampling and frequent membrane replacement, particularly in membrane distillation. Furthermore, breakthroughs in desalination batteries to remove salt ions using high capacity battery materials may lead to the revival of electrochemical processes for seawater desalination as well as niche desalination applications. Future work should be geared towards optimization of system design and economic assessment of upscaling.