Experiments involved deionized water (0.1-20 µS cm -1 ; TREION TM , TREITEL Chemical Engineering Ltd, Israel); NaOH and HCl (J.T.Baker, Poland); H2SO4 (96%) and Na2HPO4.H2O (Carlo Erba, France); H3PO4 (85%, Biolab-chemicals, Israel); and anhydrous Na2SO4, MgSO4.7H2O, K2SO4, CaCl2.2H2O, and NaF (Merck, Germany). Membranes, ED stack, and the ED 64004 cell were from PCCell GmbH, Germany. The properties of the ED membranes are listed in Table . All batch ED experiments with synthetic WW involved a BED 1-4 bench-scale laboratory electrodialyser (PCCell GmbH, Germany) connected to a DC power supply (HCS-3202, Manson). Two commercially available stacks were used with five cell pairs of monovalent selective cation-exchange membrane (MVS-CEM, PC VK), differing in their anion-exchange membranes (AEMs, PC SA or PC Acid 100), as shown in Table . The experimental setup and membrane configurations are depicted in Figure . In most experiments, the synthetic WW contained fluoride, so all equipment such as feed vessels and analytical instruments were polypropylene/polyethylene-based, as appropriate for handling fluoride solutions. The stack spacers were also replaced with polypropylene (1 mm thick) spacers.