Biological Denitrification process in anoxic fluidized bed reactor is a simple way to eliminate nitrate – nitrogen that pollute the groundwater. In this method the biofilm (including organic bacteria) was cultured on the reactor bed particles, which we chose granular activated carbon (1-3) mm. The raw water containing Nitrate ions and bacteria nutrients was pumped into the bottom of the reactor in an adequate velocity to fluidize the bed particles holding the biofilm. Ethanol and DeHydrogenated Sodium ortho phosphate was chosen as bacteria nutrients, Ethanol as carbonic nutrient and DeHydrogenated Sodium ortho phosphate as phosphoric nutrient.