Electrodialysis (ED) is an efficient process for the treatment of drinking water with high nitrate concentration. However it achieves only a transfer of pollution by producing concentrated brines. This study demonstrated the feasibility of ED brine denitrification in a membrane bioreactor (MBR). The results showed the high efficiency of the MBR despite the drastic conditions of nitrate concentration, pH and salinity of the ED concentrates. The denitrification kinetics close to 0.01 mgNO(3)(-)-NmgVSS(-1) h(-1) were in agreement with the literature values obtained with usual conditions. Next, the efficiency and performance of the hybrid process to treat ground water contaminated by nitrate was demonstrated in situ at Rodilhan (France). After ED treatment, the nitrate concentration of the treated water remained below the acceptable value (50 mg l(-1)) and a softening of the treated water was obtained. The membrane bioreactor allowed the almost total destruction of ED concentrate nitrate (99 %) with kinetics close to 0.3 kgNO(3)(-)-N kgVSS(-1) d(-1) and a sludge production of 0.5 gVSS gNO(3)(-).