Denitrification of drinking water by the association of an electrodialysisprocess and a membrane bioreactor: feasibility and application

A hybrid process combining electrodialysis and a membrane bioreactor was in vestigated to treat ground waters with excessive nitrate concentrations. El ectrodialysis (ED) allowed the nitrate separation producing, on one hand, p artially demineralized waters whose ion concentrations were in agreement wi th the norm, and on the other hand, brines that were treated by a membrane bioreactor. Experiments performed at laboratory scale with synthetic soluti ons and pre-industrial scale to treat a ground water contaminated by nitrat es showed high efficiency of the hybrid process. The nitrate concentration of the treated water remained below the acceptable value (50 mg/l(-1)) and even below the recommended value (25 mg/l(-1)) for drinking water. Moreover , the ED treatment induced a softening of the treated water. The biological denitrification allowed the almost total removal of nitrates (99%) with ki netics close to 0.3kgN-NO3/kg MVS/d and a limited sludge production of 0.5g V.S.S/gN-NO3.