Studies have been conduced on a groundwater containing 850-1100 mg/l of total dissolved solids (TDS) and 80 mg/l of nitrate to remove nitrate by coupling electrodialysis and bioreactor. The performances of the pilot plant during the period of the tests (more than one year) were proved. The optimisation of recovery rates was carried out by the study of the influence on the water recoveries of the addition of acid and antiscalant to the brine stream. The moderated performances of the bioreactor were shown.