Evaluation and Modeling of Electrodialysis for High-Recovery Brackish Water Desalination
This research investigates the feasibility of desalination of brackish water with electrodialysis (ED), using laboratory testing and mathematical modeling. Several experiments were performed to characterize ion-specific transport and to evaluate tradeoffs between salinity removal and specific energy consumption. A 200 cm2 Ameridia ED stack was used to perform desalination experiments with real brackish groundwater from the Kay Bailey Hutchison desalination plant in El Paso, Texas, and the results showed limiting current density of 160 A/m2 for 5 cm/s. A higher conductivity reduction was observed for flow velocity of 5 cm/s compared to 13 cm/s. Ion transport selectivity (based on relative removal ratio) decreased in the order of Ca2+, Cl-, Na+, and SO42-. The electrical conductivity of multi-component aqueous solutions was modeled based on ionic composition and ion pair complexes. Several experiments were performed to calibrate the model and compare it with conductivity and cation transport number data cited in the literature. The developed model is capable of estimating the electrical conductivity and ionic transport numbers of aqueous solutions up to 100 mS/cm at 25°C with a root mean square error of 0.305 mS/cm, a relative root mean square error of 9.7%, and R-squared value of 0.997. A mathematical model for steady-state ED operation was developed based on Nernst-Planck ionic transport and other theoretical principals to simulate the hydraulic, chemical, and electrical performance of the system. The model accurately predicted the removal of sodium and chloride (R-squared of more than 0.96); however, the model significantly underpredicted calcium separation and overpredicted sulfate separation. The model predicted the SEC of low and high velocities precisely predicted with RRMSE of 8% and 18%, respectively. Future work should incorporate membrane selectivity into the transport modeling.
Civil engineering|Environmental engineering
Jafarzade Ghadimi, Shahrouz, "Evaluation and Modeling of Electrodialysis for High-Recovery Brackish Water Desalination" (2020). ETD Collection for University of Texas, El Paso. AAI28088281.