Tailoring of highly efficient nitrifying biofilms in fluidized bed for ammonia-rich industrial wastewater treatment

We proposed two tailoring methods for efficient nitrifying biofilms on particles which are expected to be used in fluidized bed in nitrogen removal processes for industrial wastewaters. The first method was examined with gradual reduction of the hydraulic retention time in continuous feeding reactor to form biofilm with high nitrification ability. As a result, nitrification rate was successfully improved mainly due to acclimation of nitrifying bacteria to higher loading. The second tailoring method for nitrifying biofilm started with the biofilm which had been previously constructed in synthetic domestic wastewater containing high concentration of NH₄⁺-N as well as various biodegradable organic compounds. Stepwise reduction of C/N ratio in inlet wastewater was performed during one month simultaneously with observation of microbial population dynamics in the biofilm using fluorescent in situ hybridization (FISH) analysis. As a result, this acclimation process promoted occupation of the biofilm by ammonia-oxidizing bacteria and resulted in making suitable biofilm structure for nitrification of ammonia-rich industrial wastewater. Moreover, it is confirmed that this new tailoring method greatly shortened required time to obtain nitrifying biofilms.