(301f) Feasibility Study of High Cut Rate of Dissolved Mineral Salts In Electrodialysis Reversal Process

The shortage of drinking water is an uprising challenge in the world, and it is essential to desalinate and make use of saline and brackish waters. Use of Electrodialysis Reversal (EDR) and Reverse Osmosis (RO) systems has significantly increased during the last two decades. EDR technology uses electrical field to transport ions through selective membranes, while RO uses pressure to disuse water molecules through reverse osmosis membranes.

Relatively high capital expenditure (CapEx) of desalination technologies has limited the practical employment of saline and brackish water desalination. Hence, any attempt to reduce CapEx will result in greater utilization desalination technologies. Currently conventional separation percentage of total dissolved salts in EDR technology is about 40-60% per stage. Thus, depending on the saline/brackish water quality, in most cases EDR systems are designed to desalinate water in multiple stages, which results in higher CapEx costs. In this research the feasibility of increasing the cut rate of dissolved mineral salts by EDR process, which results in significant reduction of CapEx costs by reducing the number of EDR stages, has been studied.

Full scale pilot experimentation was performed in a 40 cell pair electrodialyser with about 12 gpm influent flow rate in Brackish Groundwater National Desalination Research Facility (BGNDRF) in Alamogordo, New Mexico. Feed brackish water was provided from a deep aquifer from Tularosa Basin, which is typical water quality in southwestern region of the United States. Short term limiting current experiments were performed that demonstrated the entitlement of 88 – 99% cut rate of dissolved solids per stage. Next, long term experiments were performed to demonstrated the feasibility of high cut rate operation. Finally, the effects of electrode design, spacer design, and membrane chemistry on sustainable operation were evaluated.