الفهرس 
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Abstract
Water is essential for human life, so management of water quality and control of pollution are major issues. Pollution of the Nile has been increased due to increasing of population and related anthropogenic activities. This thesis aimed at assessing the quality of a point of wastewater pollution namely Omer Bek drain and its impact on the receiving water of Damietta branch of the River Nile. Four water samples(Omer Bek drain, the mixing station, downstream the drain and upstream the drain) have been collected and analyzed for its physico-chemical characteristics, phytoplankton community, biological indices and algal bioassay. Data obtained revealed the presence of high concentration of ammonia, nitrite, nitrate, phosphate, BOD, COD and some heavy metals (Cd, Cu, Pb, Ni) at the drain station which deteriorate the water quality of the receiving water compared to upstream reference station. The phytoplankton communities were dominated by Chlorophyceae, Bacillariophyceae, Cyanophyceae, Euglenophyceae, Dinophyceae and Cryptophyceae. Also the photosynthetic pigments were also seasonally analyzed which revealed high concentrations of chlorophyll a at the drain station indicating phytoplankton abundance and productivity in this water. The biological indices and water quality index (the compound eutrophication, the diversity index, the Saprobic index and the diatomic indices) were investigated to characterize the eutrophication and pollution state at study area. The Compound Eutrophication index indicates eutrophic condition of water. The Diversity index indicates that the overall quality of wastewater negatively affected the species richness of phytoplankton community. The Saprobic index indicates that the drain station contain high amount of biodegradable organic matter. Also the diatomic indices revealed strong pollution status at the drain station. Water quality index (WQI) indicates bad water quality condition at the drain station and medium water quality condition at the receiving water. Finally, the algal growth potential test was used to assess the water fertility, toxicity, the nutrient limitation and their bioavailable concentrations at wastewater drain and the receiving water using Pseudokirchneriella subcapitata. The results of AGP showed that maximum standing crop of test alga was at the drain station indicating the water fertility of this site. Also the test alga was potentially inhibited by heavy metal toxicity in water samples.