Waters containing low amounts of sodium formate and sodium hydroxide were processed in order to regenerate formic acid. The treatment was performed in three steps: wastewaters neutralization, sodium formate concentration by conventional electrodialysis (ED), and sodium formate splitting into formic acid and sodium hydroxide by bipolar membrane electrodialysis (BMED). A coupling of these processes was performed. ED was carried out with a current efficiency of 90% and sodium formate concentration up to 2 mol dm(-3). BMED was performed in a three-compartment cell configuration. Formic acid solution up to 30% was obtained with current efficiency of 80% under a current density of 500 A m(-2). Diffusion of molecular formic acid explains the current efficiency loss. The current efficiency varies with acid concentration and current density. Diffusion is more important through the anion-exchange membrane than through the bipolar membrane (2.5-fold). Depleted salt produced in BMED was recycled to the neutralisation step. (c) 2006 Elsevier B.V. All rights reserved.