Comparison of electrodialysis reversal (EDR) and electrodeionization reversal (EDIR) for water softening

In the present study, EDR (electrodialysis reversal) and EDIR (electrodeionization reversal), ion exchange membrane processes using periodic change of the polarity, were examined as water softening process. The LCD (limiting current density) was empirically determined as a function of linear flow velocity with different hardness concentrations in synthetic solutions. In addition, the influence of the LCD on the transport phenomena and water splitting were investigated. Accordingly, an appropriate operating current was selected for the constant current operation based on the LCD.The process performances of EDR and EDIR were compared for removal of hardness materials from a groundwater. Water softening performances of both EDR and EDIR processes were performed with various operation parameters including current density, flow velocity and hardness concentration. The EDIR process showed notably lower electric resistance and power consumption than the EDR process. The study showed that the EDIR process with an optimized constant current mode and periodic polarity change could be used as an effective water softening process by decreasing resistance and power consumption.

The empirical limiting current density as functions of flow rate and hardness concentration was determined for the operation current in the electrodeionization reversal (EDIR).Figure optionsDownload as PowerPoint slideHighlights
► Periodical change of the polarity was examined as a water softening process.
► Appropriate current density was chosen for the constant current operation.
► Process performances of EDR and EDIR were compared for water softening.
► EDIR process showed a lower electric resistance and power consumption.