Membrane distillation for water recovery and its fouling phenomena

The total volume of water on Earth is circa 300 million cubic miles, with close to 98.0% being salt water and the remaining 2.0% fresh water. It has been increasingly more challenging to harvest fresh water from surface water, seawater and even from wastewater due to the combination of factors, viz. burgeoning population growth, rapid industrialization and climate change. Recently, membrane distillation (MD) emerges as a promising cost-effective thermal driven sustainable water recovery technology when integrated with renewable energy sources. However, one of the major challenges for MD is the membrane fouling, which has been gaining popularity in the recent literature, as well. The membrane fouling propensity for MD is very much depends on the type of feed water, suitability of membrane and the operating conditions. The objective of this review is to investigate the fouling phenomena of membrane distillation in wastewater treatment and desalination. The design of membrane and its system from the perspective of material and process design were discussed to provide an insight on the current and future advancement in MD technology for water recovery. Finally, the future trend of MD is projected based on the state of the art development of MD process.