Novel energy-efficient electrodialysis system for continuous brackish water desalination: Innovative stack configurations and optimal inflow modes

Abstract

Electrodialysis (ED) is a well-established brackish water (BW) desalination technology that has been commercially applied for decades. However, the energy efficiency of BWED cannot approach optimization because of the low salt concentration of BW. In this study, a novel two hydraulic-stage ED desalination system was presented to enhance mass transfer and reduce energy consumption. In terms of energy-efficient strategies, it involved not only innovative membrane stack configurations (resin-filled electrode cells and asymmetric cell pairs design) but also optimizing inflow modes (electrolytes parallel flow and dilute/concentrate counter flow). Results showed that thin resin-filled (1 mm) electrode cells, asymmetric cell pair design (cell pairs ratio of 1st and 2nd-hydraulic stages, 1.2), and optimizations of general inflow mode were beneficial for savings 10–30% of energy consumption at the same salt removal ratio (SR). The synergistic effects of these strategies indicated that this novel ED system could save ∼40% of the energy consumption at the same SR, compared with conventional two hydraulic-stage ED system (CED). Three stage continuous BWED performance tests, compared with a CED, showed that a 36.9% total energy saving could be achieved using the novel ED system when the BW concentration decreased from 3500 mg/L to the quality requirement of drinking water (∼450 mg/L). It was therefore possible to open the way for saving energy in BWED systems.