A Biological aerate filter (BAF) is considered one of the most important applications used in wastewater treatment. Therefore, in this study, we were looking forward to discovering its ability to treat primary sedimentation tank effluent utilizing Polyethylene floated media called bio-media as a biological filter media, which is considered the novelty point of this research. This study and investigations operated for several months with a designed pilot plant installed and designed in Zenin Wastewater Treatment Plant located in Egypt. During the operation study of the BAF system, dissolved oxygen (DO) and flow rate with different hydraulic retention times (HRT) were studied. All these parameters were measured to investigate the ability of the BAF with polyethylene bio media on removal rates of chemical oxygen demand (COD), biological oxygen demand (BOD), and total suspended solids (TSS). The result showed that the optimum HRT was 72 minutes with the DO equal to 4.67±0.2 mg/l for COD and BOD removal rates; it yielded the largest removal efficiency of COD and BOD5 68.08 % and 69.18%, respectively. While the optimum HRT was 24 minutes with the DO equal to 4.67±0.2 mg/l for TSS removal efficiency, it recorded maximum removal efficiency up to 70.40 %.