The effect of a support material on the nitrification rate in biofilm reactors

The nitrification process in a Packed Bed Biofilm Reactor (PBBR) was investigated. The inert and carbonaceous materials were tested as the support materials. The results proved the feasibility of nitrification at pH value below 5.0. On the inert support material the bicarbonates and ammonia concentrations decreased simultaneously, but when the bicarbonates present in the bulk liquid were exhausted, the nitrification ceased. For the alkaline support media, the alkalinity in bulk liquid decreased to almost zero, but the carbonaceous support materials (marble, dolomite and Dofiltr™) react with the protons and buffer the system inside biofilm. If the marble or other carbonaceous support materials are used, the packed bed material due to dissolution controls the pH inside the fixed biofilm. In reactors, the mean residence time and the Peclet number were measured. On the basis of two models (dispersion model and reactors in series model) the nitrification constant rates in reactors were estimated.