Characterization and evaluation of a biological submerged filter was carried out on a full-scale pilot plant performing removal of biochemical oxygen demand (BOD) and total nitrogen (TN) from pre-treated urban wastewater. The average influent values of BOD5, chemical oxygen demand (COD) and TN were 370, 1,015 and 60 mg/L, respectively. The pilot plant produced good discharge quality during steady-state operation. Average effluent BOD5, COD and TN values were 11, 58 and 15 mg/L, respectively. The reactor had been operating beyond its organic design capacity (200 population equivalent (PE)). At 480 PE the removal achieved for BOD, COD and TN were 98, 97 and 78%, respectively. This technology can absorb pollutant overloads while maintaining stable performance. Denitrification was performed by using sewage itself as carbon source. It was used as an intermittent aeration cycle in the unaerated cell to improve the denitrification process. The predenitrification with submerged unaerated filter has proved to be an efficient process for advanced removal of TN.