Desalination of non-traditional water and desalination brine using selective electrodialysis for irrigation

Abstract:

The unsustainability of traditional water supplies has bolstered the development of alternative water sources using various advanced treatment technologies. In this study, monovalent permselective cation-exchange membrane CR671 was developed, and bench- and pilot-scale experiments were conducted to demonstrate the technical viability and economic feasibility of the selective electrodialysis system through treatment of reclaimed water, brackish groundwater, and RO concentrate.

Selective electrodialysis can preferentially reject monovalent ions and adjust sodium adsorption ratio for fit-for-purpose applications. For instance, pilot-scale selective electrodialysis of brackish groundwater demonstrated excellent monovalent permselectivity with up to 9 times better, as compared to the corresponding standard normal electrodialysis system. Advanced analytical approaches of physicochemical and electrochemical properties were employed to successfully elucidate the mechanisms of enhanced permselectivity. The desalting efficiency was highly comparable at the same current density between bench- and pilot-scale electrodialysis system, proportional to the ratio of residence time in electrodialysis stack. The consistent desalination performance between bench- and pilot-scale testing treating various water sources, e.g., reclaimed water (TDS~1,150 mg/L) and brackish groundwater (TDS~2,700 mg/L), presented a high potential of simulation of pilot-scale electrodialysis system using bench-scale testing. Techno-economic analysis proved the selective electrodialysis system could achieve higher water recovery and cost competitiveness, e.g., more than 21% total cost reduction achieved in treating reclaimed water for golf course irrigation, in comparison to the existing UF-RO treatment.

This study provides novel theoretical and practical insights into desalination of non-traditional water sources using selective electrodialysis, and demonstrated it as a technical viable and cost effective method to treat non-traditional waters for fit-for-purpose applications such as irrigation.