Effects of electrode design on electrodialysis reversal performance

Electrodialysis/electrodialysis reversal (ED/EDR) is a promising brackish water desalination processes. As with any other desalination process, ED/EDR can be affected by several operating and design factors, many of which have been investigated thoroughly. The influences of operating factorssuch as applied voltage, flowrate, and temperatureare known, as are the influences of several design factors, such as membrane characteristics, spacer configuration, and spacer thickness. However, no published results have explored how electrode design affects the process. This paper uses pilot-scale experiments at the Brackish Groundwater National Desalination Research Facility to investigate how three different electrode designsfull, recessed, and taperedaffect the performance of EDR systems. Performance was measured as the amount of electrical current in the stack, removal percentage, and standardized power consumption (SPC); the key factor for the comparison was considered to be SPC. The experiments were conducted at two levels of feed salinity (1.7 and 3.9mScm(-1)), three levels of feed flowrate (0.44, 0.57 and 0.69Ls(-1)), and five levels of applied voltage (30, 32.5, 35, 37.5, 40V) using three types of electrode (full, recessed, and tapered). Electrode type was found to affect electrical current, removal percentage, and SPC at both investigated salinity levels. It was also found that, although using a full electrode resulted in the highest removal percentage, the SPC of the recessed electrode was lower than the SPCs of the full and tapered electrodes in higher salinity. However, recessed and full electrodes had similar, but better performance in comparison to tapered electrode when brackish water with lower salinity was used.