Techno-economic assessment of pervaporation desalination of hypersaline water

The development of pervaporation desalination has seen continuous interest due to the ability of this technology to handle high salinity feeds in the absence of high hydraulic pressure. As pervaporation utilizes the difference of partial vapor pressure as the main driving force for separation, an elevated feed temperature is often needed, and this significantly increases the energy requirements of pervaporation desalination. The advancement of high-performance pervaporation desalination membranes with high water flux and salt rejection in recent years could make this desalination technology competitive to other hypersaline desalination processes. Unfortunately, there is a lack of understanding of the energy requirements necessary for an economic assessment of pervaporation desalination applied for highly saline feed solutions. In this study, the energy requirements and the economic feasibility of pervaporation desalination for hypersaline desalination were evaluated using previously developed high-performance cellulose triacetate/cellulose nanocrystals nanocomposite membranes as the membrane model. The results showed that thermal energy was still the main factor that determined the overall water production cost. Increasing the plant capacity decreased the water cost while increasing the feed salinity from 90 to 200 g L-1 increased the water production cost due to the drop of the water production rate, which requires to expand the membrane surface area to obtain the same plant capacity. A series configuration showed the lowest thermal energy compared to a single and parallel configuration. However, the single configuration is more attractive than a series and parallel configuration when the pervaporation desalination utilized free low-grade waste heat. Hence, PV desalination for treating hypersaline water can be competitive if the process could be integrated with low-grade waste heat from industrial plants as a thermal energy source.