Increasing the demand for potable water, followed by the high quantity of discharged effluents linked with the water scarcity problems has necessitated giving more attention to improving wastewater treatment processes and operations. The constructed wetland has proven to be an excellent green sustainable technique for purification. This study aimed to examine the performance of four experimental free water surface constructed wetlands (FWSCWs) for the depuration of sewage effluents as a secondary treatment stage during winter season conditions. The objectives were to assess the raw and treated wastewater concentrations, evaluate the removal efficiency of chemical oxygen demand (COD), biological oxygen demand (BOD), nutrients, and total suspended solids (TSS) of each treatment line, and compare the impact of plastic rings (biofilm carriers) and Lemna minor L. with the presence of gravel bed on the treatment efficiency and bacterial growth, as well as assess the plant's adaption and growth. The results showed that all treatment systems improved the water characteristics, and adding biofilm carriers enhanced the efficiency of water purification, especially BOD reduction. The combination of the plants, biofilm carriers, and gravel in the wetland filter significantly enhanced (ρ < 0.05) the treatment efficiency in terms of TSS, COD, BOD, Ammonia (NH 3 ), Nitrates (NO 3 ), and Orthophosphate (PO 4 ) compared to the control treatment system (gravel bed). Plant growth was restricted in the presence of carriers in the system. Further study for examining the system performance under summer conditions, which may improve the nutrient reduction rates by biofilm carriers, is underway.