Eco-efficient treatment of ion exchange spent brine via electrodialysis to recover NaCl and minimize waste disposal

Abstract Natural organic matter (NOM) is removed from potable water for aesthetic, operational and indirect health concerns. NOM removal via ion exchange (IX) resins is receiving increasing attention owing to its simple operation. However, production of a spent brine during IX regeneration is the main drawback due to strict discharge regulations and limited and costly brine management options. In this study, the viability of desalinating the IX brine was assessed via electrodialysis (ED). ED desalination of the IX brine led to the production of highly pure NaCl and NOM-rich solutions which can be used for the IX regeneration and agricultural applications, respectively. Of particular interests were the impacts of the membrane permselectivity and implementation of pulsed electric field (PEF) on membrane fouling, desalination, purity of the NaCl solution and energy consumption. Our results demonstrated that ED desalination with monovalent ion permselective membranes consumed approximately 2 Wh per g of produced NaCl, achieved 88.8 % desalination, produced pure NaCl solution with negligible membrane fouling. Furthermore, for the first time, we demonstrated that PEF-ED intensified the process and decreased membrane fouling only when conventional ion-exchange membranes were used; while no significant difference was detected when PEF-ED was operated with monovalent ion permselective membranes.