This study examines the efficiencies of Imhoff tanks filled with plastic bottles and synthetic sponges, to improve the low efficiency of the conventional Imhoff tank. To evaluate the effectiveness of media, two Imhoff tanks with the reactor volume of 131 L, were installed and operated at the treatment site of an apartment complex in a small community. The laboratory Imhoff tank with reactor volume of 23 L was operated to examine the effects of aeration in the sedimentation chamber. At the HRT of 1 day, the Imhoff tanks filled with plastic bottles and synthetic sponges showed BOD removal efficiencies of 48.7% and 46%, respectively, and SS removal efficiencies of 71.1% and 76%, respectively. However, BOD removal efficiency of 80.1% and SS removal efficiency of 89.5% were obtained when the effluent of Imhoff tank was aerated in the sedimentation chamber.