The impact of hydraulic loading rate (HLR) and hydraulic retention time (HRT) on the bioremediation of municipal wastewater using a horizontal flow constructed wetland (HFCW) vegetated with Cyprus papyrus was investigated. Three different HLRs were applied with values of 0.18, 0.10 and 0.07 m³/m².d with corresponding HRT of 1.8, 3.2 and 4.7 days. The flow rate was 8.3 m³/d and the average organic loading rate was 0.037kg BOD/m³/d. Results showed that the performance of HFCW is linearly affected by decreasing HLR and increasing the HRT. The remediation for the heights HRT (4.7) days and lowest HLR (0.07 m³/m².d) produced high quality effluent in terms of reduction of chemical oxygen demand (COD; 86%), biochemical oxygen demand (BOD; 87%) and total suspended solids (TSS; 80%) as well satisfactory nutrient removal. Also, removal of 2-3 logs of bacterial indicators was achieved. The dry biomass of Cyprus papyrus was 7.7 kg/m². Moreover, Cyprus papyrus plant proved to be very efficient in nitrification processes due to high diversity of the roots that increase the treatment surface area.