AbstractThis study is an evaluation of the effects of using filter media on the performance of an integrated settler-based biofilm reactor (ISBR) for onsite treatment of domestic wastewater, as it is a known fact that filter media play an important role in the biological treatment of wastewater. The ISBR had three compartments. The first one was a settler, which was followed by two upflow anaerobic biofilm reactors, each representing a single compartment. All three compartments were accommodated within a single compact unit. The study was divided into two phases, based on the different filter media (aqwise carrier, moving bed biofilm reactor (MBBR), and brick) used in the biofilm reactors. In the first phase, aqwise carrier and MBBR media were used in the second and third compartments of the reactor, respectively; in the second phase, the MBBR medium in the third compartment was replaced with brick medium. The ISBR delivered remarkably good removal efficiency for organic pollutants. It also worked well in color removal to a considerably good extent. The average pollutant removal efficiency of the ISBR in the second phase was observed as 93.06 ± 4.5, 91.83 ± 3.2, and 90.89 ± 5.5% for total suspended solids (TSS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD), respectively. As regards bacterial analysis, the total and fecal coliform removal efficiencies in the second phase were found to be 90.5 ± 3.6 and 95.36 ± 1.8%, respectively. Field scanning electron microscopy of the media showed the morphology of anaerobes as clearly visible, which was a good sign for the system. The results observed after replacement of MBBR medium with brick medium proved that the ISBR had good potential for use as an onsite sanitation system.