Characteristics of Cells Proliferation and Mass Transfer of Immobilized Nitrifiers in a Nitrification Process

Characteristics of cells proliferation and substrate transfer of immobilized nitrifiers during cultivation was investigated. The respiratory rate, nitrification rate and biomass in the pellets showed a similar tendency of slow increase when cultivation was over. The activity of unit biomass decreased for the difficult oxygen transfer into the compact microcolonies. De also went degressive gradually along with time because the diffusivities in the microcolonies near the pellets surface are lower than that in the support phase. SEM and TEM pictures reveal that the microorganisms grow like a biofilm on the pellets surface, while expand as colonies inside the pellets. mu_i obtained via cells balance in the reactor decreased gradually, would reach a steady state that mu_i approximates 0.