Pilot-Scale Investigation of Two-Step Biofiltration for Municipal Wastewater Treatment

Abstract

Pilot plant of two-step biofiltration, a pre-denitrification step followed by a nitrifying step (CN-biofilter),was designed to treat the primary settled municipal wastewater. Performance of the two-step biofiltration was evaluated and compared with the one-step biofiltration (CN-biofilter only). The two-step biofiltration was more effective in removing COD and BOD from municipal wastewater. The predenitrification step reduced significantly the organic loading to the following step, CN-biofilter. Therefore, in the CN-biofilter, nitrification rate was enhanced. An important factor affecting the performance of two-step biofiltration is the recirculation ratio. The recirculation ratio determines SCOD/NO3 pre-denitrification step. In order to maximize total nitrogen removal, SCOD/NO3 -N in the -N ratio has to be maintained at 6 .