This paper analyzes the results of floated leaved wetland system and its effectiveness in improving the quality of drain water. A field floated leaved wetland pilot is constructed in Fayoum governorate and monitored for about two months. Treatment effectiveness of the wetland system was determined using mass balance techniques. Also, a water quality model was used to predict treatment effectiveness as a function of retention time, which is a function of both system size as well as flow rate. Treatment effectiveness of the modeled wetland system was than compared under varied theoretical retention times to provide an indication of how size and flow rate within the system might affect the performance of a full-scale IST System. Atypical IST proposed considering the recommendations in (8)4. Finally, the possible directions for further studies are recommended.