Membrane distillation driven by solar energy: A review

Membrane distillation (MD) is considered a promising technology that is expected to compete with reverse osmosis (RO) for water desalination. The superiority of MD is mainly due to its ability to treat extremely high salinity water where RO is not feasible. In addition, the problem of accumulation of mycobacteria associated with RO does not exist in MD that operates at temperature as high as 90 °C. This review focuses on the types of solar collectors used to provide the temperature difference needed for MD operation. Comparisons between different types of MD systems powered by solar energy based on their operating temperature, membrane characteristics and type of solar collector is offered together with their advantages and disadvantages as well as relevant industrial applications. Comparison between MD and RO technologies revealed that the RO driven by photovoltaic energy source is considered the best approach for seawater water desalination because it not only achieves the highest daily productivity per meter square of solar field but also has the lowest operating cost. Nevertheless, the MD powered by solar energy is considered a promising technology for treatment of extremely saline water. It is also recommended to integrate MD with RO desalination system to achieve higher water recovery and reduce the overall environmental footprint.