Brine management from desalination plants for salt production utilizing high current density electrodialysis-evaporator hybrid system: A case study in Kuwait

Abstract

The potential of producing salt and low salinity water by treating synthetic brine was investigated in a pilot-scale electrodialysis-evaporator hybrid system as part of brine management. An electrodialyzer with 25 cell pairs of monovalent selective anion exchange membranes (AEMs) and monovalent selective cation exchange membranes (CEMs) were used. Effect of three different current densities (300 to 500 A/m2) and two different flowrates (400 L/h and 450 L/h) on brine treatment were evaluated in the current study. The results indicated that the aforementioned membranes were efficient in separating monovalent ions over divalent ions. Moreover, higher current density operation was favoured during the electrodialysis (ED) operation as the operation time for producing salt was shorter. Flowrate is a crucial parameter for the operation of the ED system, where higher flowrate (by 12.5%) reduced the operation time (by 30 min), reduced energy consumption (by 32%) and reduced system resistance (by 32.42%) leading to an increase in current efficiency (by 31.4%). The concentrated brine effluent from ED was fed to an evaporator to produce coarse salt with 84.75% salt recovery and low salinity water of 1526 ppm. Thus, ED-evaporator hybrid system was found to be a good option to treat reject brine from desalination plants.