Modeling-Based Comparison of Gypsum Scaling Potential between Reverse Osmosis and Electrodialysis for Brackish Water Desalination

Brackish water desalination offers a sustainable solution to water scarcity, but mineral scaling such as gypsum scaling poses a major operational challenge. While electrodialysis (ED) has emerged as a promising alternative to reverse osmosis (RO) for brackish water desalination, the propensity to mineral scaling has not been systematically compared between these two processes. This study employs a process modeling approach to compare gypsum scaling propensity between RO and ED, focusing on a low feed salinity regime (∼3 g L–1). Gypsum scaling is evaluated in RO as a function of water recovery, applied pressure, and membrane water permeance, while it is assessed in ED for the concentrate stream as a function of salt removal under varying cell pair voltages and water recoveries. Results reveal that increasing applied pressure or membrane water permeance intensifies gypsum scaling in RO and reduces the water recovery at gypsum saturation. In ED, co-ions and counterions exhibit distinct behaviors of accumulation near the membrane surface, with scaling potential increasing at higher water recovery and lower cell pair voltage. At consistent system productivity, gypsum scaling imposes a more significant constraint on RO than ED, highlighting the potential of ED as a more robust alternative to RO and informing technology selection and optimization in brackish water desalination.