This study was conducted to assess the possibility of simultaneous nitrification and denitrification in an activated sludge using a cilia media packed with granular sulfur in a single reactor. For the granular sulfur column adopted, the total nitrogen removal was up to 67%. This facilitated the simultaneous decomposition of autotrophic and heterotrophic denitrifiers present at a 5:2 ratio. On the other hand, the control incubation test employing glass beads achieved only 18% denitrification. Regardless of the NH4-N loadings, the use of ciliated granular sulfur columns, made denitrification 1.5 times faster than when cilia was not used. The size of the granular sulfur columns directly contributed to the extent of denitrification, which was correlated to the void sphere of anoxic zones through the columns. Dissolved oxygen (DO) concentrations lower than 4.0 mg/L did not influence the level of denitrification. However, when higher than 4.0 mg/L, the DO began to negatively impact the denitrification rate. The study found that the simple installation of a cilia media packed with granular sulfur in an existing activated sludge could simultaneously achieve an efficient nitrification/denitrification in a single reactor.