Considering Reverse Osmosis and Electrodialysis Reversal for Desalination of Brackish Groundwater Containing High Silica

Abstract

Brackish water desalination is an important alternative for developing drinking water sources in arid regions. Electrodialysis reversal (EDR) and reverse osmosis (RO) are suitable technologies for desalination of brackish groundwater. Pilot testing conducted with brackish groundwater containing 1,200 mg/L of total dissolved solids (TDS) and 60 mg/L of silica demonstrated that RO can operate at 10 gfd with 75 percent recovery and 96 percent TDS rejection. As predicted by modeling software for the same water chemistry, the EDR process can operate at 88 percent recovery with TDS rejection of 78 percent. Order of magnitude cost estimates (−30 percent and +50 percent) prepared for three feed-flow scenarios (3, 5, and 8 mgd) for RO and EDR treating the same groundwater suggested both processes are comparable, especially when feedwater contains elevated silica levels.