DYNAMICS OF NITRIFYING BIOFILM GROWTH IN BIOLOGICAL NITROGEN REMOVAL PROCESS

A conventional laboratory scale annular reactor was employed to invest igate the dynamics of nitrifying biofilm growth. A dense and thin nitr ifying biofilm was developed in this study. The results showed that th e active growth of the nitrifying biofilm can be characterized best by the increase of the specific substrate removal rate until a maximum v alue, at which the maximum active film thickness and active biomass we re attained. It was found that non active biomass accumulation directl y resulted in the reduction in the specific ammonium nitrogen removal rate, however the ammonium nitrogen surface removal rate was not affec ted by the additional biomass accumulation. As a result, the credibili ty of the classic method using the substrate surface removal rate to e stimate the maximum active film thickness was doubted. It was expected that thinner nitrifying biofilm ranging from 20 to 30 mu m has a high er specific nitrification rate to be 9.0mgNH(4)(+)-N/mgCOD-biomass/day .