Recent advances in membrane distillation hybrids for energy-efficient process configurations: Technology categorization, operational parameters identification, and energy recovery strategies

Membrane distillation (MD) hybrids have the potential to integrate heat recovery mechanisms, enhancing freshwater productivity and minimizing specific energy consumption. However, the recent development of innovative hybrid MD systems for resource recovery have not yet been thoroughly assessed. Hence, this work presents a critical review on recent advances in membrane distillation hybrids and their technological developments towards resource recovery. The potential integration of MD configurations with other various membrane osmotic desalination technologies such as reverse osmosis (RO), nanofiltration (NF), reverse electrodialysis (RED), forward osmosis (FO), and freezing desalination (FD) is comprehensively discussed. More so, the hybridization of diversified MD processes with conventional thermal distillation systems including multi-vapor compression (MVC), multi-stage flash (MSF), humidification–dehumidification (HDH), and multi-effect distillation (MED) is also of great interest in this work. Additionally, the design and operational considerations that enhance hybrid MD systems, including membrane development and optimization of heat requirements are reviewed and evaluated in this work. The summarized findings revealed that the hybrid MD-RO is the best potential integration of MD compared with other desalination technologies, in which this integration successfully achieves a high-water recovery ratio of up to 90 %. Moreover, the integration between MD and FO also shows a good potential for treatment of extremely saline water, and oily wastewater. This integration also shows significant improvement in concentrating RO brine compared to using MD only. From thermal desalination technologies, the integration between MD and the existing MED plants is also recommended as MED is ranked as the second technology after RO. The MED brine also has considerably elevated temperature that significantly improves the performance of the MD. In summary, this review underscores the promising potential of MD hybrids in resource recovery within different desalination scenarios. It also delves into future recommendations aimed at enhancing hybrid MD, including considerations such as pilot-scale implementation, module arrangement, and advancements in membrane technology.