The present results revealed that phytoplankton communities in the study area were represented mainly by 7 classes namely: Chlorophyceae, Cyanophyceae and Bacillariophyceae as the main groups followed by Euglenophyceae, while Cryptophyceae, Dinophyceae and Xanthophyceae were rarely present. Chlorophyceae was the first dominant group, forming 59.7% of the total phytoplankton community, while Bacillariophyceae was the second dominant group forming 19.3% followed by the third dominant group, the Cyanophyceae forming 15.6% of the total phytoplankton community. The seasonal variations of chlorophyll a and b revealed that ,the maximum chlorophyll a and b values of 251.6 and 70.9 mg/L were recorded in the effluent water during summer respectively, while the minimum one of  26.8 and 2.9 mg/L were recorded in primary sedimentation tank (PST) during autumn and winter respectively. The highest values of gross production (3120 mg C/m³/h ) and net production (1146 mg C/m³/h ) were found in the effluent during summer and spring seasons respectively, while the lowest values 110.9 mg C/m³/h  and 78.6 mg C/m³/h) were  found in the PST during winter season.