Effects of operating conditions on ion removal from brackish water using a pilot-scale electrodialysis reversal system

Abstract

Understanding the effects of operating factors on ion removal in the electrodialysis/electrodialysis reversal (ED/EDR) process can significantly benefit industrial applications, enabling process optimization through different combinations of operational factors. Several studies have shown the effects of specific operating factors on ion removal, and it has been established that superficial velocity influences ion removal. However, previous studies have yielded mixed results on whether increases in superficial velocity increase or decrease ion removal; also, since previous studies are based on laboratory-scale ED systems, the results may not be fully applicable to full-scale desalination due to differences in system characteristics such as membrane area, flow path, and degree of superficial velocity’s effect on ion removal. Therefore, this experimental study employs a pilot-scale EDR system that is very similar to a full-scale system in order to explore the effects of applied voltage, superficial velocity, and feed water temperature on ion removal. Additionally, a conceptual explanation is developed to explain the inconclusive results from previous research. The findings of this experiment confirmed that increases in superficial velocity decreased ion removal, and this result can help predict and optimize full-scale operations. In the investigated ranges, increasing voltage and temperature resulted in increased ion removal, while increasing superficial velocity resulted in decreased ion removal. The experiments were conducted at the Brackish Groundwater National Desalination Research Facility in Alamogordo, NM, USA on a General Electric Company pilot-scale EDR system with a maximum product flow rate of 45 L/min, using brackish water with a conductivity of 1,700 μS/cm.