Co-locating reverse electrodialysis with reverse osmosis desalination: Synergies and implications

Abstract

In this paper, we investigated the synergistic effects of co-locating reverse electrodialysis (RED) with other water and power infrastructures. The potential benefit of greater salinity (e.g., using brine from seawater desalination plants) and higher feed water temperature (e.g., through the co-location with power plants) were studied. Maximum RED power was obtained when the low salinity stream (LS) had moderate salinity (0.01–0.02M NaCl), which can be explained by the competing effects of reduced internal resistance and decreased electrochemical potential upon increasing the LS concentration. At the same time, greater salinity of the high salinity stream (HS) and higher feed water temperature both significantly improved the power performance. Compared to the HS temperature, the LS temperature played a more important role due to the dominance of electrical resistance of the LS compartment. When RED was applied as a pre- or post-treatment to RO, it can efficiently remove salt from the HS stream (e.g., nearly 50% reduction in the HS concentration demonstrated in our bench scale evaluation). We further show that, during the RED salt removal process, the ionic efficiency (~ 76% in the current study) was closely related to the permselectivity of the ion exchange membranes.