Gabal El-Asfar drain (GAD) receives a secondary treated sewage effluent from Gabal El-Asfar wastewater treatment plant (GAWWTP). The design capacity of GAWWTP is 2.5 million m³/d. The drain receives also agriculture drainage water from agriculture sub drain. The drain length is about 7.7 km starts from the GAWWTP and discharge in Belbeis drain. This study focused in the first 7 km of the GAD. The objective of this study is to develop a hydrodynamic model for GAD and simulate the fate of residual pollutants from GAWWTP and subdrains to study the effect of  velocity variation within the drain channel GAD using a water quality module. Delft3D-FLOW software was used firstly to develop the hydrodynamic model of the drain based on the historical geometric and hydraulic data. hereafter, Delft3D-WAQ was used to simulate the fate of residual pollutants in terms of Biochemical, chemical, etc. based on water quality measurements that were conducted from February to May 2023 in the field. The calibrated model was used to study the impact of the drain velocity on GAD water quality. Many scenarios have been conducted assuming that the capacity of GAWWTP is varied from 1 to 3.5 million m³/ day, which these capacity refer to longitudinal velocity in GAD from 0.3 to 0.8 m/s. The results showed that as the velocity in the drain increased, the removal rate of BOD5, COD and TSS were decreased. The reduction of BOD5, COD and TSS were 33.56, 3.12 and 71.30 % respectively for scenario 1 where the velocity is 0.3 m/s, While the reduction of BOD5, COD and TSS was 12.29, 1.31 and 23.81 % respectively for scenario 6 where the velocity is 0.8 m/s.
 
 
Special Issue of AEIC 2024 (Civil Engineering  Session)