Brine recovery using reverse electrodialysis in membrane-based desalination processes

• We evaluated the influence of desalination brines on reverse electrodialysis (RED).
• We modified the RED model developed by Veerman et al.
• We obtained maximum powers of 1.48 and 1.86 W/m2 with the RO and FO brines.
• Using RED, the SEC of the RO and FO processes can be reduced by 7.8% and 13.5%.

Power enhancement is a key issue in the commercialization of RED. In this paper, we report a method to improve the power generation using brines discharged from two different membrane-based desalination processes. We modified a RED model proposed by Veerman and co-workers, and this modified model was in agreement with experimental results. We considered river water and seawater as the diluted solutions for RED. The power density with RO (1.48 W/m2) and FO (1.86 W/m2) increased 1.5-fold and 2-fold, respectively, compared with that using seawater. When seawater was used as the diluted solution, the RED power decreased considerably. We characterized the RED performance using the intermembrane distance and the inlet flow rate. The power generated monotonously increased with decreasing compartment thickness and increasing flow rate. The net power had a specific optimal value because of a drastic growth in the pumping power. In our system, the optimal intermembrane distance was 0.1 mm (RO brine) and 0.3 mm (FO brine). We also computed the energy cost owing to RED. The results showed that the energy consumption could be lowered by ~ 7.8% from the typical value for RO. We found a drastic decrease for FO with the energy consumption lowered by ~ 13.5%.

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